CA1284536C - Member for semiconductor apparatus - Google Patents
Member for semiconductor apparatusInfo
- Publication number
- CA1284536C CA1284536C CA000570628A CA570628A CA1284536C CA 1284536 C CA1284536 C CA 1284536C CA 000570628 A CA000570628 A CA 000570628A CA 570628 A CA570628 A CA 570628A CA 1284536 C CA1284536 C CA 1284536C
- Authority
- CA
- Canada
- Prior art keywords
- warp
- copper
- radiating
- aluminum nitride
- substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/02—Containers; Seals
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/12—Mountings, e.g. non-detachable insulating substrates
- H01L23/14—Mountings, e.g. non-detachable insulating substrates characterised by the material or its electrical properties
- H01L23/15—Ceramic or glass substrates
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/02—Containers; Seals
- H01L23/06—Containers; Seals characterised by the material of the container or its electrical properties
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
- H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
- H01L23/373—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon
- H01L23/3735—Laminates or multilayers, e.g. direct bond copper ceramic substrates
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/42—Wire connectors; Manufacturing methods related thereto
- H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
- H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
- H01L2224/481—Disposition
- H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
- H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
- H01L2224/48225—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation
- H01L2224/48227—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation connecting the wire to a bond pad of the item
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12014—All metal or with adjacent metals having metal particles
- Y10T428/12028—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, etc.]
- Y10T428/12049—Nonmetal component
- Y10T428/12056—Entirely inorganic
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
- Y10T428/12528—Semiconductor component
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
- Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
- Y10T428/12576—Boride, carbide or nitride component
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
- Y10T428/12771—Transition metal-base component
- Y10T428/12861—Group VIII or IB metal-base component
- Y10T428/12882—Cu-base component alternative to Ag-, Au-, or Ni-base component
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
- Y10T428/12771—Transition metal-base component
- Y10T428/12861—Group VIII or IB metal-base component
- Y10T428/12903—Cu-base component
- Y10T428/1291—Next to Co-, Cu-, or Ni-base component
Abstract
ABSTRACT OF THE DISCLOSURE
A member for a semiconductor apparatus for carrying or holding a semiconductor device, obtained by joining an aluminum nitride substrate and a radiating substrate, comprises an insulating member formed by an aluminum nitride sintered body to be provided thereon with the semiconductor device, a radiating member to be joined to the insulating member, which radiating member is mainly formed of a copper-tungsten alloy or a copper-molybdenum alloy, a stress relieving member interposed between the insulating member and the radiating member and a silver solder member for joining the insulating member, the stress relieving member and the radiating member with each other. The stress relieving member is prepared by copper or a copper alloy, implementing a soft metal or a soft alloy having high plastic deformability, in order to relax, by its own plastic deformation, thermal stress caused by difference in thermal expansion coefficient between the insulating member and the radiating member in a cooling step upon soldering.
A member for a semiconductor apparatus for carrying or holding a semiconductor device, obtained by joining an aluminum nitride substrate and a radiating substrate, comprises an insulating member formed by an aluminum nitride sintered body to be provided thereon with the semiconductor device, a radiating member to be joined to the insulating member, which radiating member is mainly formed of a copper-tungsten alloy or a copper-molybdenum alloy, a stress relieving member interposed between the insulating member and the radiating member and a silver solder member for joining the insulating member, the stress relieving member and the radiating member with each other. The stress relieving member is prepared by copper or a copper alloy, implementing a soft metal or a soft alloy having high plastic deformability, in order to relax, by its own plastic deformation, thermal stress caused by difference in thermal expansion coefficient between the insulating member and the radiating member in a cooling step upon soldering.
Description
TIT:~.E C)F Ti~E INVE,MTI 01~
Melnbe~ for Semicorlductor Appardtus BACKGROUND ~F THE INVENTION
Field of the Invention The present invention relates to a member for a semi~onduc-tor apparatus, and mo~e parti.cularly, it relates to a member for a semiconductor apparatus such as a c.ircuit substrate, which must be of high thermal conductiv.ity to be mounted w.ith a semicorlduc~or de~ice oE
high caloxi~ic pow~r such as a high-power tx~nsistor or a laser diode.
Description of the Prior Art A member for a sem~conductor apparatus to be mounted with a semiconductor device is generally formed by an insulating member and a radiating member joined to the insulating member. For example, such a member for a semiconductor:apparatus is formed by an insulating substrate to be provided thereon with a sem.icondu~tor device and a :radiating.substrate joined to the.back surface of the insulating substrate by soldering through silver solder or the li.ke. In this case, gerJerally re~uired for the ins~llating substrate are high electric insulability for insulation from the semiconduct~r device, high mechanical strength and high.thermal con~uctivity Eor dissipating heat.generated from the.semiconductor-device.
3L~ 6 The radiating substrh~e must have hiyh thermal conductivity simi.larly to the .insulating substrate, w~lile its thermal expansion coefficient must be approximat-e to those of materials forming a semiconductor substrate, the insulating substrate and the like.
In general, alumina.(A12O3) is selected as a material satisfying the aforementioned properties for formi.ny the insulating substrate employed in.such a member for a semiconductor apparatus. However, although al~nina is excellent in electric insulability and mechanical strength, its he-at dissipation property is inferior due-to small thermal conductivity of 17 Wm lK 1. Thus, it is improper to carry a field-effect transistor (FET) of.high calorific power, for example, on an alumina substrate; In order to carry a semiconductor device of high.calorific power, another type of insulating substrate is prepared by beryllia (BeO) having high thermal.conductivity of 260 Wm K , whereas beryllia is toxic and hence it is troublesome to take safety measures in employment of such an insulating substrate.
The radiating.substrate .is generally prepared by a material satisfying the aforemention~d properties, which material is selected from metal materials such' as various types of copper alloys, copper-tungstén alloys and copper-molybdenum alloys. For example, Japanese Patent Laying-Open Gazette No. 21032/198~l discloses a sub~trate of high thermal conductivity for carrying a semicondllctor device, the material of which is prepared by mixi.ng 2 to 30 percent by weight of copper into tungsten or molybdenum. This substrate is employed as a radiating substrate which is suitably joined to an alumina substrate having inferior heat dissipation property, and differencs in thermal expansion coefficient between tlle same and alumina is relatively-small. Thus, t~lis prior art e~ampls is.insufficient in heat dissipation property, which is required entirely over a substrate for carrying a semiconductor device.
In recent years, nontoxic aluminum nitride tAlN) has generated great interest as a material for such an insulating substrate for carrying a semiconductor device of high calorific power because of its high thermal conductivity of about. 200 Wm 1K 1, which value is substantially e~ual to that of beryllia> as well.as..its electric insulability and mechanical strength which are equivalent to those of alumina.
However, when an aluminum.nitride substrate provi.ded with a metallized layer is soldered by a soldering metal such as gold solder or silver solder, for example, to a generally employed radiating substrate.of a copper-tungsten alloy or copper~molybdenum alloy contain.ing ln to 25 percent by weight of copper, lrhe aluminum oitr.ide substrate may be cracked or the radial~ g substrate of the copFer-tungsterl alloy or the copper-molybdenum alloy-may be warpe~.
Such a phenomenon results f rom thermal stress caused by difference in therma~l expansion coe~ficient~ between the copper-tun~sten alloy or the copper-moJ ybdenum alloy and alurninum nitride during a cooling step UpOll soldering, which is performed at a ternperature of 500 to 9~0C. Thi.~s 10 thermal stress may conceivably be lef t in the alurninum nitride substrate as tensile residual stress, to crack the aluminurn nitride- substrate and/or warp the radiating substrate of the copper-tungsten alloy or the copper-molybdenurn alloy.
When an alurninum nitride substrate is joined to a radiating substrate of a copper-tungsten alloy or a copper-molybdenum alloy by cold soldering or soldering, the alumi.num nitride subs.trate or an interf ace between the same and a metallized layer is cracked by a therrno cycle 20 tesl~ ~-55C to +150C, 1000 cycles) or a thermal shocl~
tes t to cause a signif icant problern in practice, even if no warp nor crack. is recognized upon joining.
In a sample of an aluminum nitride substrate joined to a radiating substrate of a copper-t.ungsten alloy or a 25 copper-molybdenum alloy by silver soldering, therma~l f~
~atigue or thermal st~ess was caused in a t}lermo cycie test or a thermal shoc~ test due to d.iffelence in thern)al expansion coefficient between the radiating substrate of the copper-tungsten alloy or the copper-molybdenum alloy S and the aluminum nitride substrate, similarly to the above. Such a problem of thermal stress or thermal fatigue is aggravated with increase in junction-area.
Thermal expansion-coefficierlts of the copper-tungsten alloy or the copper-molybdenum alloy having.the aforementioned composition and aluminurn nitride are 6.5 to 10 X 10 6IK and 4 to 5 x 10 6/K respectively, within a ranye of the room temperature to about 950C. Further, these materials, having high Young's modulus of 27000 to 35000 KgJmm2 and 35000 to 37000 Kg/n~2 respectively, are ~lardly plastically deformed. Thus, when the copper-tungsten alloy or the copper~molybdenum alloy of the aforementioned composition:and.aluminum nitride are joined with each other by soldering, large thermal.stress is conceivably caused in a cooling step.
SUMMARY OF THE INVEN~'ION
An object o~ the present invention is to provide a member for a semiconductor apparatus by employing an insulating member of alumin.um nitride, being excellent in thermal dissipation property, for mounting a semiconductor device of high balorific power, so that a radiating memb2r .
L~
mainly ~ormed of a cop~er-tullgsterl.alloy or a copper molybdenum alloy having~high heat radi.ation property can be joined to the insulatiny member while causing no crack nor warp.
The inventors have made deep study to solve the aforementioned problem, to Eind that it is effective to interpose a specific thermal.stress.relieving member between an insulating member.of aluminum nitride and a radiating mem~er mainly formed of a copper-tungsten~alloy or a copper-molybderlum alloy, to prevent cracking or warping caused by thermal stress in a cooling step upon soldering.
A member for a semiconductor apparatus in accordance with the present invention, being.adapted to carry or hold a semiconductor devicej comprises an insulating.member oE
aluminum nitride having a major surface to face the semiconductor device, a radiating member to be joined to the insulating member and mainly Eormed oE a copper-tungsten alloy or a copper-molybdenwn alloy, a stress relieving.member, and a soldering.member for joining the insulating member, the stress relieving member and the radiating member with each other. The stress relieving member, to be interposed betweeT~ the insulating member and the radiating member, is prepared by a soft z5 metal or a soft alloy having high plastic deformability in order to relax, throuyll its own plastic deEoLmation, thermal stress caused by differencQ in t~lermal expansion coefficient between the insulating member and the radiating member in a cooling step upon soldering.
Preferably the stress.reli.eving member is prepared by copper, a copper alloy, nickel or a nick~l alloy.
The stress relieving member of either a soft metal.or a soft alloy-thus interposed between the insulating member of aluminum nitride and the radiating memher is further softened around the soldering temperature, to be extremely plastically deformable~ Thus., most part of thermal ~stress caused by difference in thermal.expansion coefficient between the insulating member of aluminum nitride and tlle radiating member is absorbed by plastic deformation.of the stress relieving member, to solve the problem of residual stress in the insulating member. Consequently, the insulating member is prevented from cracking and the radiating member is prevented from warping.
The stress relieving member is preferably in a range of ~.~1 to 1 mm in thickness. If the thickness is not more than 0.01 mm, the stress relieving member cannot be sufficiently plastically deformed to absorb thermal stress. If the thickness exceeds.1 mm, on the other-hand, thermal stress caused.by thermal expansion of the stress relieving member itself in soldering cannot be neglected..
Namely, although thermal stress caused by difference in therrnal expans.ion coefficient betweell tl,e radiating mernb~r and the insulating member can be ab,orbed by plastic deformation of.the stress relieving memher, the stress relieving member itself causes significant thermal stress to exert bad influence of thermal deformat.i.on on the radiating member or the insulati.ng member.
The insulating member of aluminum nitride is preferably employed as a substrate having a major surface to be provi.ded.thereon.with a semiconductor device.
Alternatively, the insulating member m~y be applied to a covering member. provided above a semiconductor device to protect the same, which covering member forms a cap for airtightly sealing a semiconductor device provided on an insulating substrate, for example. When the insulating member is employed as a substrate for carrying:a semiconductor device or a covering member for protecting-a semiconductor device, the inventive member for a semiconductor apparatus is adapted to conduct heat generated from the semiconductor device to the insulating member and a radiating mem~er, thereby to dissipate the same to the exterior. The insulating.memb.er of aluminum nitride preferably includes a sintered body.
The insulating member.of alumlnum nitride is preferably provided on its junction surface with a metallized layer, which contains ~t least tullgsten or molybdenum, at least one aluminum compound within aluminum nitride, aluminum o~ide-and aluminwn o~ynitride, and calcium oxide or yttri~lm o~ide, to attain preferable junction strength and thermal conductivity.
Further, a plating layer is provided in a junction surface of the metallized layer with a soldering member to uniformly perform stabilized soldering. Namely, wettability between the soldering member and the metallized layer can be improved by provision of the plating layer. Another plating la~er provided in a junction surface of the radiating member with the soldering member functions similarly to the above. Such plating layers are preferably formed by nickel plating.
Such nickel plating is preferably performe~ particularly when processing such as gold plating is performed in a later step, in order to improve adhesion and precipi.tation properties of gold plating for forming a uniform gold plating layer.
Further, the copper-tungsten alloy or the copper-molybdenum alloy employed for the inventive member preferably contains 5 to 25 percent by weight of copper.
If the content of copper is less than 5 percent by weight, thermal conductivity, being an essential function of the copper-tungsten alloy or the copper-molybdenum alloy 3~
forming the radiating rnembe-, may be lost althougll mismatch in therma~ expa~sion coefficient between the copper-tungsten alloy or the copper~molybdenum alloy and aluminum nitride is relaxed. 1~ ti-le content of copper exceeds 25 percent by weight, the thermal expansion coefficient of the copper-tungsten alloy or.the copper-molybdenum alloy is further increased to diEfer from that of aluminum nitride, leading to increase in thermal stress caused.in the junction surface, although thermal conductivity of the copper-tungsten alloy or the copper-molybdenum alloy is rendered urther preferab'e.
According.to the inventive member for a se~iconduct.or apparatus, a stress relieviny member is interposed between the insulating member and the radiating.member, thereby to prevent cracking.of the.insulating membex and warping of the radiating member upon joining of the insulating.member of aluminum nitride and the radiating mem~er mainly formed of the copper-tungsten alloy or the copper-molybdenum alloy. Thus, a reliable:member for a semiconductor apparatus.can be easily obtained to be applied to a substrate for carrying a semiconductor apparatus, a covering member for sealing a semiconductor device or the like.
These and other objects, features, aspects and advantages of the-present invention will become more ,, . , ;
3 ~
apparent from the following-detailed descriptiorl of the present invention when taken in conjunc-tion- Wit~l the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figs. lA and lB are process drawings schematically showing two exemplary methods of manufacturing a rnember for a semiconductox apparatus in accordance with the present invention;
Figs. 2A, 2B and 2C are a plan view and sectional vi~ws showing an example oE junction structure in a member for a semiconductor apparatus in accordance with the present invention, such as jw~ction struct-lre between a lead frame, an aluminum nitride substrate and a radiating substrate;
Fig. 3 is a sectional view showing an embodiment of a member for a semiconductor apparatus in accordance with the present invention, which is applied to a heat sink mernber for a semiconductor devi.ce such as a light emitting diode (LED) or a laser diode tLD);
Fig. 4 is a sectional view showing another embodiment of the inventive member for a semiconductor apparatus, which is applied to a part of a cap for airtightly sealing a semiconductor device to serve as a covering member; and Fig. 5 is a side elevational view.show~3ng a porti.on subjected to measu.rernent of a warp caused in a radiating member joined to an aluminum nitride substrate.
DESCRIPTION OF THE PRE~FERRF~D EMBODIMENTS
S As hereinabove described, the present invention is adapted to improve the technique of formin~ a member for a semiconductor apparatus by employing.an insulating.member of aluminum nitride~ Aluminum nitride employed in the form of a sintered body in the present inven-tion is obtained by the following method, for example:
The insulating member ~ormed by an aluminum nit~ide sintered body employed in the present invention, preferably being mainly composed.of aluminllm nitride, contains 0.01 to 1.0 percent by weight o~ an element belonging to the group Illa of the periodic table and 0.001 to 0.5 percent by weight o oxygen, and its thermal conductivity is at least 180 Wm 1K 1. First, at least one compound containing a rare earth element is mixed with powder of aluminum nitride so that its content is 0.01 to 1.0 percent by weight in rare earth element conversion. A
~orming additive.is prepared by paraphine, PVD or PEG. A
substance, such as phenol resin, being decomposed to leave carbon, carbon powder, graphite powder or.the like may be added to control residual carbon.in the sintered body.
The rare earth compound is prepared by stearic acid, palmitic acid, alkoxide nitrate, carbonatc, hydroxide or t~e like. Preferably employed is a high molecule compoulld such as stearic acid. Such a compound is conceivably adapted to reduce the content oE the rare earth elem~nt to enable good mixing with aluminum nitride powder. In particular, stearic acid is JnoSt preEerable in view~of mixability with aluminwn nitride powder, the amount of residual carbon etc~ in addition to its function as a formir)g additive. The alumirlum nitride pow~er must be Eormed by fine uniform particles. Preferably its average particle size is not more than 1 ~m, and the oxygen content is not more than 2.0 percent by weight. Such aluminum nitride powder is obtained by a reduction nitriding method ~method by reduction nitriding of aluminum oxide), since it is difficult to obtain the same by a direct nitriding method (method by nitriding of metal aluminum). In order to obtain the powder by the direct nitriding method, sufficient considerati.on must be made on reaction control, classification of the particle size and the like.
Then the mixed powder is shaped into a prescribed configuration and sintered in a non-oxidizing atmosphere containing nitrogen. In order to attain high thermal conductivi.ty, it is preferable to sinter the substance at a temperature of 1000 to 2100C for at least five hours, ~ h~-~
so that its average part.icle si~e i~s at least 5 ~)m. A~e-r such sintering, .i-t is prefera~le to quickly carry ouL a cooling step. If the subs~ance is slow-ly cooled, a sintering additive is precipitated and the sintered face is extremely deteriorated. Therefore, -the sintered body is preferably cooled to a temperature of 150~C at a rate o~ at least 200C/h.
The steps of forming a metallized layer on the surface of a substrate formed by thc aluminum nitride sintered body obtained in the aforementione~ manner are performed as follows:
First, a substrate of the aluminum ni~ride sintered body is prepared by the aforementioned method. A material for-the metallized layer is prepared by kneading powder of a calcium compound, that of an alwninum compound and metal powder of tungsten or molybdenum with addition.of:an organic binder.such.as vehicle, to provide metal paste.
The contents of the respective components may be within the ranges of 40 to 98 percent by weight o~ the metal powder, 1 to 25 percent b~ weigh.t of the aluminum compo-lnd and l to 35 percent by weight of calcium oxide. In order to perform a later sintering step at a low temperature, copper or nickel ma~ be added.as a catalyst for reducing the sintering temperature. The metal paste thus provided is applied to the surface of the substrate formed by the al~ninum nitride sintexe~ body. The-su~s~rate formed by the aluminum nitride sinter.ed body is fired in an inert atmosphere of nitrogen or the like at a temper~ture.-of 1500 to 1800C, to be provided with a metallized layer ~n its suxface. A metallized layer prepared by metal powder of tungsten and containing 1 to 10 percent by weight of aluminum oxide, employed as the aluminum compound, and 1 to 20 percent by weight of calcium oxidej or that prepar.ed by metal powder of molybdenum and.containing 1 to 10 percent by weight of aluminum oxidej employed as the alumi.nwn compound, and 1 to 35 percent by weight. of calcium oxide is preferable in view of adhe~ion betwe2n the substrate formed by the aluminum nitride sintere~ body and the metallized layer and thermal conductivity.
The steps of forming a metallized layer on the su~face of a substrate formed by the aluminum nitride sintered body may be.performed as follows, by sintering.an aluminum nitride formed body coated with the metal paste at one time.
First, a substrate of the aluminum nitride formed body is prepared by shaping the aforementioned mixed powder into a prescri.bed configuration such as a green sheet. A material for the metalli7.ed layer is prepared by kneading powder of tungsten and at least one additive 25 selected from a group of aluminum oxide, aluminum nitride, f~
calcium oxide, yt~rium oxide and stearic acid yt~rium and the like, to provide metal paste, similarly to the above.
The metal paste thus pro~ided is applied to the surface of the substrate formed by the aluminum nitride formed body, by printing or coating. The substrate formed by the aluminum nitride formed body is sintered with the metal paste similarly to the above conditions, to be provided with a metallized layer on the-surface-of a substra-te formed by the aluminum nitride sintered body. Thus, the aluminum nitride sintered body with the metallized having high thermal conductivity can be obtained.
Description is now made on a typical method of forming the member for a semiconductor apparatus in accordance with the present invention. Figs. lA and lB
are process drawings showing two methods of manufacturing the member for a semiconductor apparatus in accordance with the presenk invention. Referring to Fi~. lA, an aluminum nitride sintered substrate is first prepared.
Then, the metal paste obtained through the aforementioned method is applied to the surface of the aluminum nitride sintered substrate. Thereafter the metal paste thus applied is dried. Then the aluminum nitride sintered substrate is fired in an inert gas atmosphere which is heated to a prescribed temperature.
~L,~
The above steps may be performed as follows.
Referring to Fig. lB, an aluminum nitride formed substrate is first prepared. Then, the metal paste obtained through the aforementioned method is applied to the surface of-the aluminum nitride formed su~strate. Thereafter the metal paste thus applied is dried. ~hen the aluminum nitride formed substrate is sintered with the metal pa~te in an inert gas atmosphere which is heated to a prescribed temperature. Thus, an aluminum nitride sintere~ substrate with a metallized layer is formed.
After a metallized layer is formQ~ on the aluminum nitride sintered substrate, nickel plating is performed on the surface of the metalliæed layer. Heat treatment is performed at a temperature of about 800C to sinter the lS nickel plating, thereby to improve strength and airtightness of the same. On the other hand, nickel plating is also performed on the surface of a heat sink member, serving as a radiating member, which is joined to the aluminum nitride sintered substrate, similarly to the above. Then soldering is performed on the nickel plating surface in order to join the aluminum nitride sintered substrate to the heat sink member. Further, gold plating is performed on such junction. Thus, the member for a semiconductor apparatus in accordanae with the present invention can be manufactured.
Description is now made on an embodiment of a member for a semiconductor apparatus in accordance with an aspect of the present invention, which is manufactured along the aforementioned steps, such as a member comprising an aluminum nitride substrate joined to a lead frame on its surface and to a heat sink member on its back surface, with reference to the dxawings.
Fig. 2A is a plan view showing an embodiment which is applied to a substrate for carrying a semiconductor device, Fig. 2B is a sectional view of the substrate and Fig. 2C is a sectional view showing a junction between a heat sink member 6 and an aluminum nitride substrate 1 in detail. Referring to these figures, the aluminum nitride substrate 1, implementing the inventive member-for a semiconductor apparatus, is partially formed on its surface with a metallized layer 2 in accordance with the aforementioned steps, and a lead frame 3 is joined to the metallized layer 2 through soldering by a soldering metal or the like. Another metallized layer 2 is formed on a ZO part of the back surface of the aluminum nitride substrate 1 in accordance with the aforementioned steps, while the heat sink member 6 is joined to the metallized layer 2 through soldering by a soldering metal or the like. A
semiconductor device 4 such as an FET of high calorific power is carried on a prescribed Fosition of the aluminum ' ' ~ ' ' '" ' '~ .- .
nitride subs~rate 1, to be conllected wi~h the rneLallized layer 2 or the lead ~rame 3 by a bondir.g wire ~. As shown in Fig. 2C, a thin plating layer.7 is formod on t.he metallized layer 2 in the junction between-the aluminum nitride substrate 1 and the heat sink member-6, while a plating layer 3 is formed at need on the surface oE the heat sink member 6, in order to stabilize wettability of a soldering metal 9. In this case, a stress relieving member 10 of a soft metal such as copper, which is formed with nickel plating layers 7 on its surface, is interposed between the metallized layer 2 and the heat sink member 6 serving as a radiating member.
Description is now made on another embodi~ent of a member for a semiconductor apparatus in accordance with another aspect of the present invention, which is applied to a radiating substrate for carrying a semiconductor device such as a diode having high calorific power, for example, with reference to Fig. 3. Referring to Fig. 3, an aluminum nitride substrate 1 is mounted on a heat sink member 6, serving as a radiating member mainly formed of the copper-tungsten alloy or the copper-molybdenum alloy in accordance with the present invention~ through a metallized layer 2 similarly to the above, while a semiconductor:device 4 such as a light emitting diode (LED) or a laser diode (LD) is joined on the aluminum nitride substrate 1. The semicondu,tor device 4 is joined on another metallized layer 2 which is formed on the surface of the aluminum nitride substrate 1. In this case, the aluminum nitride substrate 1 serves as a heat sink member. The alwninum nitride substrate 1 and the heat sink member 6 are joined with each other in a similar manner to the above description with reference to the junction structure between the aluminum nitride substrate provided with the lead frame and the heat sink member.
Description is now made on the structure of a cap to which a member for a semiconductor apparatus in accordance with the present invention is applied, with reference to Fig. 4. A metallized layer 2 is provided on the surace of a peripheral edge~portion of a covering member 11 formed by an aluminum sintered body. A frame-member 13 formed by a layer of a metal such as an iron-nickel alloy is joined to the metallized layer 2 by a soldering metal or the like. The lower end of the frame member 13 is joined to a ceramic substrate 101 through another metallized layer 2. A semiconductor device 4 is carried on the ceramic substrate 101. A heat sink member 6 is mounted on the upper surface of the covering member 11, so that heat generated from the semiconductor device 4 is dissipated by the heat sink member 6 through the covering member 11, to improve a cooling effect. The covering r~3L~
member 11 of the aluminum nitride sintere~ body and the heat sink member 6 are joined w.ith each other in a similar manner to the above description with reference to the junction structure between the aluminum nitride substrate provided with the lead frame and the heat sink member.
The soldering metal employed for such junction is preferably prepared by silver solder, while another soldering material.is also available so far as a thin metal coating layer having good wettability to the soldering material can be formed on the junction surEace of the heat sink member 6 or the metallized layer 2 to strongly join the covering member 11 and the-heat sink member 6 with each other. The function of such a thin metal coating.layer, such as a plating layer, is as hereinabove described with reference to the example of junction structure-between the aluminum nitride substrate provided with the lead frame and the heat sink member.
Descript:;on .is now made on Examples 1 and 2 of the present invention, which were made by sa.mples prepared by substrates of the aluminum nitride sintered body obtained by the aforementioned method.
Example 1 Aluminum nitride sintered substrates of 1 . 3 mm iII
thickness were prepared by the aforementioned method, to be subjected to metallization. The metalliz.ation processing was perf~rmed by applying metal pas~e oE
prescribed composition to the surfaces of respective samples of the aluminum nitride sintered substrates, performing debindering and then Eiring the same in a nitrogen atmosphere at a temperature of 16~0C fox 60 minutes. Thus, metallized layers were formed on prescribed portions of the aluminum nitride sinte.red substra~es. The metal paste was prepared by adding calciurn oxide powder and alurnina powder to tungsten powder and kneading the same with an organic binder such as vehicle. The conteTlt of ca.lcium oxide.was 14 percent by weight and that of alumina was 4 percent by weight. The shapes of the employed aluminum nitride sintered substrates were 5 mm square, 20 mrn square and 50 mrn s~uare respectively.
Further, nickel plating layers of 2 ~m in thickness were formed on the surfaces of the rnetallized layers. On the other hand, copper-tungsten alloy plates oE 1.5 mm in thickness having various compositions.were prepared as radiating members to be joined to the respective aluminum nitride sintered substrates. Nickel plating of 2 ~m in thickness was performed on the surfaces of these copper-tungsten alloy plates, which were then soldered to the respective aluminum nitride sintered subs.t-rates ~y ~rP~
silver solder with interposi.tion o~ stress relieving members of nickel or coppex at, a tempera.ture of 830C.
Examination was.made as to whet.he~ or not the aluminum nitride sintered substrates were cracked and whet~,er or not the cop~er-tungsten alloy plates were warped in the respective samples thus obtained. As shown in Fig. 5, an aluminum nitride sintered substrate 1 and a heat sink member 6 of each sample were joined with each other, to evaluate the degree of wa.rping as the amo~lnt a by a surface roughness tester (product of Tokyo Seimitsu:
E-SP-SOlA). Cracks caused in the respective aluminum nitride sintered substrates were obser~ed by a scanning type electron microscope of 5000 magnifications or a steromicroscope o~ 40 magnifications. Tables 1 to 3 show the results. As to evaluation of warps, those oE not more than 2 ~m with respect to effective length of 1 rnm were regaxded as l~X10 warp", while samples causing warps exceeding 2 ~m with respect to effective length oE 1 mm were regarded as "warped".
The numerals 5, 10 and 20 in "CuW5", "CuW10" and l'CuW20" in Tables indicate contents.of copper in the copper~tungsten alloys. As to the copper-tungsten alloys, thermal expansion coeffi.cients of CuW5, CuW10 and CuW20 were 6.0 to 7.0 x 10 6JK, 6.5 to 7.5 x 10 6/K and 8.5 to 25 9.5 x 10 ~K in a range of the room tempera-ture to 950C.
Melnbe~ for Semicorlductor Appardtus BACKGROUND ~F THE INVENTION
Field of the Invention The present invention relates to a member for a semi~onduc-tor apparatus, and mo~e parti.cularly, it relates to a member for a semiconductor apparatus such as a c.ircuit substrate, which must be of high thermal conductiv.ity to be mounted w.ith a semicorlduc~or de~ice oE
high caloxi~ic pow~r such as a high-power tx~nsistor or a laser diode.
Description of the Prior Art A member for a sem~conductor apparatus to be mounted with a semiconductor device is generally formed by an insulating member and a radiating member joined to the insulating member. For example, such a member for a semiconductor:apparatus is formed by an insulating substrate to be provided thereon with a sem.icondu~tor device and a :radiating.substrate joined to the.back surface of the insulating substrate by soldering through silver solder or the li.ke. In this case, gerJerally re~uired for the ins~llating substrate are high electric insulability for insulation from the semiconduct~r device, high mechanical strength and high.thermal con~uctivity Eor dissipating heat.generated from the.semiconductor-device.
3L~ 6 The radiating substrh~e must have hiyh thermal conductivity simi.larly to the .insulating substrate, w~lile its thermal expansion coefficient must be approximat-e to those of materials forming a semiconductor substrate, the insulating substrate and the like.
In general, alumina.(A12O3) is selected as a material satisfying the aforementioned properties for formi.ny the insulating substrate employed in.such a member for a semiconductor apparatus. However, although al~nina is excellent in electric insulability and mechanical strength, its he-at dissipation property is inferior due-to small thermal conductivity of 17 Wm lK 1. Thus, it is improper to carry a field-effect transistor (FET) of.high calorific power, for example, on an alumina substrate; In order to carry a semiconductor device of high.calorific power, another type of insulating substrate is prepared by beryllia (BeO) having high thermal.conductivity of 260 Wm K , whereas beryllia is toxic and hence it is troublesome to take safety measures in employment of such an insulating substrate.
The radiating.substrate .is generally prepared by a material satisfying the aforemention~d properties, which material is selected from metal materials such' as various types of copper alloys, copper-tungstén alloys and copper-molybdenum alloys. For example, Japanese Patent Laying-Open Gazette No. 21032/198~l discloses a sub~trate of high thermal conductivity for carrying a semicondllctor device, the material of which is prepared by mixi.ng 2 to 30 percent by weight of copper into tungsten or molybdenum. This substrate is employed as a radiating substrate which is suitably joined to an alumina substrate having inferior heat dissipation property, and differencs in thermal expansion coefficient between tlle same and alumina is relatively-small. Thus, t~lis prior art e~ampls is.insufficient in heat dissipation property, which is required entirely over a substrate for carrying a semiconductor device.
In recent years, nontoxic aluminum nitride tAlN) has generated great interest as a material for such an insulating substrate for carrying a semiconductor device of high calorific power because of its high thermal conductivity of about. 200 Wm 1K 1, which value is substantially e~ual to that of beryllia> as well.as..its electric insulability and mechanical strength which are equivalent to those of alumina.
However, when an aluminum.nitride substrate provi.ded with a metallized layer is soldered by a soldering metal such as gold solder or silver solder, for example, to a generally employed radiating substrate.of a copper-tungsten alloy or copper~molybdenum alloy contain.ing ln to 25 percent by weight of copper, lrhe aluminum oitr.ide substrate may be cracked or the radial~ g substrate of the copFer-tungsterl alloy or the copper-molybdenum alloy-may be warpe~.
Such a phenomenon results f rom thermal stress caused by difference in therma~l expansion coe~ficient~ between the copper-tun~sten alloy or the copper-moJ ybdenum alloy and alurninum nitride during a cooling step UpOll soldering, which is performed at a ternperature of 500 to 9~0C. Thi.~s 10 thermal stress may conceivably be lef t in the alurninum nitride substrate as tensile residual stress, to crack the aluminurn nitride- substrate and/or warp the radiating substrate of the copper-tungsten alloy or the copper-molybdenurn alloy.
When an alurninum nitride substrate is joined to a radiating substrate of a copper-tungsten alloy or a copper-molybdenum alloy by cold soldering or soldering, the alumi.num nitride subs.trate or an interf ace between the same and a metallized layer is cracked by a therrno cycle 20 tesl~ ~-55C to +150C, 1000 cycles) or a thermal shocl~
tes t to cause a signif icant problern in practice, even if no warp nor crack. is recognized upon joining.
In a sample of an aluminum nitride substrate joined to a radiating substrate of a copper-t.ungsten alloy or a 25 copper-molybdenum alloy by silver soldering, therma~l f~
~atigue or thermal st~ess was caused in a t}lermo cycie test or a thermal shoc~ test due to d.iffelence in thern)al expansion coefficient between the radiating substrate of the copper-tungsten alloy or the copper-molybdenum alloy S and the aluminum nitride substrate, similarly to the above. Such a problem of thermal stress or thermal fatigue is aggravated with increase in junction-area.
Thermal expansion-coefficierlts of the copper-tungsten alloy or the copper-molybdenum alloy having.the aforementioned composition and aluminurn nitride are 6.5 to 10 X 10 6IK and 4 to 5 x 10 6/K respectively, within a ranye of the room temperature to about 950C. Further, these materials, having high Young's modulus of 27000 to 35000 KgJmm2 and 35000 to 37000 Kg/n~2 respectively, are ~lardly plastically deformed. Thus, when the copper-tungsten alloy or the copper~molybdenum alloy of the aforementioned composition:and.aluminum nitride are joined with each other by soldering, large thermal.stress is conceivably caused in a cooling step.
SUMMARY OF THE INVEN~'ION
An object o~ the present invention is to provide a member for a semiconductor apparatus by employing an insulating member of alumin.um nitride, being excellent in thermal dissipation property, for mounting a semiconductor device of high balorific power, so that a radiating memb2r .
L~
mainly ~ormed of a cop~er-tullgsterl.alloy or a copper molybdenum alloy having~high heat radi.ation property can be joined to the insulatiny member while causing no crack nor warp.
The inventors have made deep study to solve the aforementioned problem, to Eind that it is effective to interpose a specific thermal.stress.relieving member between an insulating member.of aluminum nitride and a radiating mem~er mainly formed of a copper-tungsten~alloy or a copper-molybderlum alloy, to prevent cracking or warping caused by thermal stress in a cooling step upon soldering.
A member for a semiconductor apparatus in accordance with the present invention, being.adapted to carry or hold a semiconductor devicej comprises an insulating.member oE
aluminum nitride having a major surface to face the semiconductor device, a radiating member to be joined to the insulating member and mainly Eormed oE a copper-tungsten alloy or a copper-molybdenwn alloy, a stress relieving.member, and a soldering.member for joining the insulating member, the stress relieving member and the radiating member with each other. The stress relieving member, to be interposed betweeT~ the insulating member and the radiating member, is prepared by a soft z5 metal or a soft alloy having high plastic deformability in order to relax, throuyll its own plastic deEoLmation, thermal stress caused by differencQ in t~lermal expansion coefficient between the insulating member and the radiating member in a cooling step upon soldering.
Preferably the stress.reli.eving member is prepared by copper, a copper alloy, nickel or a nick~l alloy.
The stress relieving member of either a soft metal.or a soft alloy-thus interposed between the insulating member of aluminum nitride and the radiating memher is further softened around the soldering temperature, to be extremely plastically deformable~ Thus., most part of thermal ~stress caused by difference in thermal.expansion coefficient between the insulating member of aluminum nitride and tlle radiating member is absorbed by plastic deformation.of the stress relieving member, to solve the problem of residual stress in the insulating member. Consequently, the insulating member is prevented from cracking and the radiating member is prevented from warping.
The stress relieving member is preferably in a range of ~.~1 to 1 mm in thickness. If the thickness is not more than 0.01 mm, the stress relieving member cannot be sufficiently plastically deformed to absorb thermal stress. If the thickness exceeds.1 mm, on the other-hand, thermal stress caused.by thermal expansion of the stress relieving member itself in soldering cannot be neglected..
Namely, although thermal stress caused by difference in therrnal expans.ion coefficient betweell tl,e radiating mernb~r and the insulating member can be ab,orbed by plastic deformation of.the stress relieving memher, the stress relieving member itself causes significant thermal stress to exert bad influence of thermal deformat.i.on on the radiating member or the insulati.ng member.
The insulating member of aluminum nitride is preferably employed as a substrate having a major surface to be provi.ded.thereon.with a semiconductor device.
Alternatively, the insulating member m~y be applied to a covering member. provided above a semiconductor device to protect the same, which covering member forms a cap for airtightly sealing a semiconductor device provided on an insulating substrate, for example. When the insulating member is employed as a substrate for carrying:a semiconductor device or a covering member for protecting-a semiconductor device, the inventive member for a semiconductor apparatus is adapted to conduct heat generated from the semiconductor device to the insulating member and a radiating mem~er, thereby to dissipate the same to the exterior. The insulating.memb.er of aluminum nitride preferably includes a sintered body.
The insulating member.of alumlnum nitride is preferably provided on its junction surface with a metallized layer, which contains ~t least tullgsten or molybdenum, at least one aluminum compound within aluminum nitride, aluminum o~ide-and aluminwn o~ynitride, and calcium oxide or yttri~lm o~ide, to attain preferable junction strength and thermal conductivity.
Further, a plating layer is provided in a junction surface of the metallized layer with a soldering member to uniformly perform stabilized soldering. Namely, wettability between the soldering member and the metallized layer can be improved by provision of the plating layer. Another plating la~er provided in a junction surface of the radiating member with the soldering member functions similarly to the above. Such plating layers are preferably formed by nickel plating.
Such nickel plating is preferably performe~ particularly when processing such as gold plating is performed in a later step, in order to improve adhesion and precipi.tation properties of gold plating for forming a uniform gold plating layer.
Further, the copper-tungsten alloy or the copper-molybdenum alloy employed for the inventive member preferably contains 5 to 25 percent by weight of copper.
If the content of copper is less than 5 percent by weight, thermal conductivity, being an essential function of the copper-tungsten alloy or the copper-molybdenum alloy 3~
forming the radiating rnembe-, may be lost althougll mismatch in therma~ expa~sion coefficient between the copper-tungsten alloy or the copper~molybdenum alloy and aluminum nitride is relaxed. 1~ ti-le content of copper exceeds 25 percent by weight, the thermal expansion coefficient of the copper-tungsten alloy or.the copper-molybdenum alloy is further increased to diEfer from that of aluminum nitride, leading to increase in thermal stress caused.in the junction surface, although thermal conductivity of the copper-tungsten alloy or the copper-molybdenum alloy is rendered urther preferab'e.
According.to the inventive member for a se~iconduct.or apparatus, a stress relieviny member is interposed between the insulating member and the radiating.member, thereby to prevent cracking.of the.insulating membex and warping of the radiating member upon joining of the insulating.member of aluminum nitride and the radiating mem~er mainly formed of the copper-tungsten alloy or the copper-molybdenum alloy. Thus, a reliable:member for a semiconductor apparatus.can be easily obtained to be applied to a substrate for carrying a semiconductor apparatus, a covering member for sealing a semiconductor device or the like.
These and other objects, features, aspects and advantages of the-present invention will become more ,, . , ;
3 ~
apparent from the following-detailed descriptiorl of the present invention when taken in conjunc-tion- Wit~l the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figs. lA and lB are process drawings schematically showing two exemplary methods of manufacturing a rnember for a semiconductox apparatus in accordance with the present invention;
Figs. 2A, 2B and 2C are a plan view and sectional vi~ws showing an example oE junction structure in a member for a semiconductor apparatus in accordance with the present invention, such as jw~ction struct-lre between a lead frame, an aluminum nitride substrate and a radiating substrate;
Fig. 3 is a sectional view showing an embodiment of a member for a semiconductor apparatus in accordance with the present invention, which is applied to a heat sink mernber for a semiconductor devi.ce such as a light emitting diode (LED) or a laser diode tLD);
Fig. 4 is a sectional view showing another embodiment of the inventive member for a semiconductor apparatus, which is applied to a part of a cap for airtightly sealing a semiconductor device to serve as a covering member; and Fig. 5 is a side elevational view.show~3ng a porti.on subjected to measu.rernent of a warp caused in a radiating member joined to an aluminum nitride substrate.
DESCRIPTION OF THE PRE~FERRF~D EMBODIMENTS
S As hereinabove described, the present invention is adapted to improve the technique of formin~ a member for a semiconductor apparatus by employing.an insulating.member of aluminum nitride~ Aluminum nitride employed in the form of a sintered body in the present inven-tion is obtained by the following method, for example:
The insulating member ~ormed by an aluminum nit~ide sintered body employed in the present invention, preferably being mainly composed.of aluminllm nitride, contains 0.01 to 1.0 percent by weight o~ an element belonging to the group Illa of the periodic table and 0.001 to 0.5 percent by weight o oxygen, and its thermal conductivity is at least 180 Wm 1K 1. First, at least one compound containing a rare earth element is mixed with powder of aluminum nitride so that its content is 0.01 to 1.0 percent by weight in rare earth element conversion. A
~orming additive.is prepared by paraphine, PVD or PEG. A
substance, such as phenol resin, being decomposed to leave carbon, carbon powder, graphite powder or.the like may be added to control residual carbon.in the sintered body.
The rare earth compound is prepared by stearic acid, palmitic acid, alkoxide nitrate, carbonatc, hydroxide or t~e like. Preferably employed is a high molecule compoulld such as stearic acid. Such a compound is conceivably adapted to reduce the content oE the rare earth elem~nt to enable good mixing with aluminum nitride powder. In particular, stearic acid is JnoSt preEerable in view~of mixability with aluminwn nitride powder, the amount of residual carbon etc~ in addition to its function as a formir)g additive. The alumirlum nitride pow~er must be Eormed by fine uniform particles. Preferably its average particle size is not more than 1 ~m, and the oxygen content is not more than 2.0 percent by weight. Such aluminum nitride powder is obtained by a reduction nitriding method ~method by reduction nitriding of aluminum oxide), since it is difficult to obtain the same by a direct nitriding method (method by nitriding of metal aluminum). In order to obtain the powder by the direct nitriding method, sufficient considerati.on must be made on reaction control, classification of the particle size and the like.
Then the mixed powder is shaped into a prescribed configuration and sintered in a non-oxidizing atmosphere containing nitrogen. In order to attain high thermal conductivi.ty, it is preferable to sinter the substance at a temperature of 1000 to 2100C for at least five hours, ~ h~-~
so that its average part.icle si~e i~s at least 5 ~)m. A~e-r such sintering, .i-t is prefera~le to quickly carry ouL a cooling step. If the subs~ance is slow-ly cooled, a sintering additive is precipitated and the sintered face is extremely deteriorated. Therefore, -the sintered body is preferably cooled to a temperature of 150~C at a rate o~ at least 200C/h.
The steps of forming a metallized layer on the surface of a substrate formed by thc aluminum nitride sintered body obtained in the aforementione~ manner are performed as follows:
First, a substrate of the aluminum ni~ride sintered body is prepared by the aforementioned method. A material for-the metallized layer is prepared by kneading powder of a calcium compound, that of an alwninum compound and metal powder of tungsten or molybdenum with addition.of:an organic binder.such.as vehicle, to provide metal paste.
The contents of the respective components may be within the ranges of 40 to 98 percent by weight o~ the metal powder, 1 to 25 percent b~ weigh.t of the aluminum compo-lnd and l to 35 percent by weight of calcium oxide. In order to perform a later sintering step at a low temperature, copper or nickel ma~ be added.as a catalyst for reducing the sintering temperature. The metal paste thus provided is applied to the surface of the substrate formed by the al~ninum nitride sintexe~ body. The-su~s~rate formed by the aluminum nitride sinter.ed body is fired in an inert atmosphere of nitrogen or the like at a temper~ture.-of 1500 to 1800C, to be provided with a metallized layer ~n its suxface. A metallized layer prepared by metal powder of tungsten and containing 1 to 10 percent by weight of aluminum oxide, employed as the aluminum compound, and 1 to 20 percent by weight of calcium oxidej or that prepar.ed by metal powder of molybdenum and.containing 1 to 10 percent by weight of aluminum oxidej employed as the alumi.nwn compound, and 1 to 35 percent by weight. of calcium oxide is preferable in view of adhe~ion betwe2n the substrate formed by the aluminum nitride sintere~ body and the metallized layer and thermal conductivity.
The steps of forming a metallized layer on the su~face of a substrate formed by the aluminum nitride sintered body may be.performed as follows, by sintering.an aluminum nitride formed body coated with the metal paste at one time.
First, a substrate of the aluminum nitride formed body is prepared by shaping the aforementioned mixed powder into a prescri.bed configuration such as a green sheet. A material for the metalli7.ed layer is prepared by kneading powder of tungsten and at least one additive 25 selected from a group of aluminum oxide, aluminum nitride, f~
calcium oxide, yt~rium oxide and stearic acid yt~rium and the like, to provide metal paste, similarly to the above.
The metal paste thus pro~ided is applied to the surface of the substrate formed by the aluminum nitride formed body, by printing or coating. The substrate formed by the aluminum nitride formed body is sintered with the metal paste similarly to the above conditions, to be provided with a metallized layer on the-surface-of a substra-te formed by the aluminum nitride sintered body. Thus, the aluminum nitride sintered body with the metallized having high thermal conductivity can be obtained.
Description is now made on a typical method of forming the member for a semiconductor apparatus in accordance with the present invention. Figs. lA and lB
are process drawings showing two methods of manufacturing the member for a semiconductor apparatus in accordance with the presenk invention. Referring to Fi~. lA, an aluminum nitride sintered substrate is first prepared.
Then, the metal paste obtained through the aforementioned method is applied to the surface of the aluminum nitride sintered substrate. Thereafter the metal paste thus applied is dried. Then the aluminum nitride sintered substrate is fired in an inert gas atmosphere which is heated to a prescribed temperature.
~L,~
The above steps may be performed as follows.
Referring to Fig. lB, an aluminum nitride formed substrate is first prepared. Then, the metal paste obtained through the aforementioned method is applied to the surface of-the aluminum nitride formed su~strate. Thereafter the metal paste thus applied is dried. ~hen the aluminum nitride formed substrate is sintered with the metal pa~te in an inert gas atmosphere which is heated to a prescribed temperature. Thus, an aluminum nitride sintere~ substrate with a metallized layer is formed.
After a metallized layer is formQ~ on the aluminum nitride sintered substrate, nickel plating is performed on the surface of the metalliæed layer. Heat treatment is performed at a temperature of about 800C to sinter the lS nickel plating, thereby to improve strength and airtightness of the same. On the other hand, nickel plating is also performed on the surface of a heat sink member, serving as a radiating member, which is joined to the aluminum nitride sintered substrate, similarly to the above. Then soldering is performed on the nickel plating surface in order to join the aluminum nitride sintered substrate to the heat sink member. Further, gold plating is performed on such junction. Thus, the member for a semiconductor apparatus in accordanae with the present invention can be manufactured.
Description is now made on an embodiment of a member for a semiconductor apparatus in accordance with an aspect of the present invention, which is manufactured along the aforementioned steps, such as a member comprising an aluminum nitride substrate joined to a lead frame on its surface and to a heat sink member on its back surface, with reference to the dxawings.
Fig. 2A is a plan view showing an embodiment which is applied to a substrate for carrying a semiconductor device, Fig. 2B is a sectional view of the substrate and Fig. 2C is a sectional view showing a junction between a heat sink member 6 and an aluminum nitride substrate 1 in detail. Referring to these figures, the aluminum nitride substrate 1, implementing the inventive member-for a semiconductor apparatus, is partially formed on its surface with a metallized layer 2 in accordance with the aforementioned steps, and a lead frame 3 is joined to the metallized layer 2 through soldering by a soldering metal or the like. Another metallized layer 2 is formed on a ZO part of the back surface of the aluminum nitride substrate 1 in accordance with the aforementioned steps, while the heat sink member 6 is joined to the metallized layer 2 through soldering by a soldering metal or the like. A
semiconductor device 4 such as an FET of high calorific power is carried on a prescribed Fosition of the aluminum ' ' ~ ' ' '" ' '~ .- .
nitride subs~rate 1, to be conllected wi~h the rneLallized layer 2 or the lead ~rame 3 by a bondir.g wire ~. As shown in Fig. 2C, a thin plating layer.7 is formod on t.he metallized layer 2 in the junction between-the aluminum nitride substrate 1 and the heat sink member-6, while a plating layer 3 is formed at need on the surface oE the heat sink member 6, in order to stabilize wettability of a soldering metal 9. In this case, a stress relieving member 10 of a soft metal such as copper, which is formed with nickel plating layers 7 on its surface, is interposed between the metallized layer 2 and the heat sink member 6 serving as a radiating member.
Description is now made on another embodi~ent of a member for a semiconductor apparatus in accordance with another aspect of the present invention, which is applied to a radiating substrate for carrying a semiconductor device such as a diode having high calorific power, for example, with reference to Fig. 3. Referring to Fig. 3, an aluminum nitride substrate 1 is mounted on a heat sink member 6, serving as a radiating member mainly formed of the copper-tungsten alloy or the copper-molybdenum alloy in accordance with the present invention~ through a metallized layer 2 similarly to the above, while a semiconductor:device 4 such as a light emitting diode (LED) or a laser diode (LD) is joined on the aluminum nitride substrate 1. The semicondu,tor device 4 is joined on another metallized layer 2 which is formed on the surface of the aluminum nitride substrate 1. In this case, the aluminum nitride substrate 1 serves as a heat sink member. The alwninum nitride substrate 1 and the heat sink member 6 are joined with each other in a similar manner to the above description with reference to the junction structure between the aluminum nitride substrate provided with the lead frame and the heat sink member.
Description is now made on the structure of a cap to which a member for a semiconductor apparatus in accordance with the present invention is applied, with reference to Fig. 4. A metallized layer 2 is provided on the surace of a peripheral edge~portion of a covering member 11 formed by an aluminum sintered body. A frame-member 13 formed by a layer of a metal such as an iron-nickel alloy is joined to the metallized layer 2 by a soldering metal or the like. The lower end of the frame member 13 is joined to a ceramic substrate 101 through another metallized layer 2. A semiconductor device 4 is carried on the ceramic substrate 101. A heat sink member 6 is mounted on the upper surface of the covering member 11, so that heat generated from the semiconductor device 4 is dissipated by the heat sink member 6 through the covering member 11, to improve a cooling effect. The covering r~3L~
member 11 of the aluminum nitride sintere~ body and the heat sink member 6 are joined w.ith each other in a similar manner to the above description with reference to the junction structure between the aluminum nitride substrate provided with the lead frame and the heat sink member.
The soldering metal employed for such junction is preferably prepared by silver solder, while another soldering material.is also available so far as a thin metal coating layer having good wettability to the soldering material can be formed on the junction surEace of the heat sink member 6 or the metallized layer 2 to strongly join the covering member 11 and the-heat sink member 6 with each other. The function of such a thin metal coating.layer, such as a plating layer, is as hereinabove described with reference to the example of junction structure-between the aluminum nitride substrate provided with the lead frame and the heat sink member.
Descript:;on .is now made on Examples 1 and 2 of the present invention, which were made by sa.mples prepared by substrates of the aluminum nitride sintered body obtained by the aforementioned method.
Example 1 Aluminum nitride sintered substrates of 1 . 3 mm iII
thickness were prepared by the aforementioned method, to be subjected to metallization. The metalliz.ation processing was perf~rmed by applying metal pas~e oE
prescribed composition to the surfaces of respective samples of the aluminum nitride sintered substrates, performing debindering and then Eiring the same in a nitrogen atmosphere at a temperature of 16~0C fox 60 minutes. Thus, metallized layers were formed on prescribed portions of the aluminum nitride sinte.red substra~es. The metal paste was prepared by adding calciurn oxide powder and alurnina powder to tungsten powder and kneading the same with an organic binder such as vehicle. The conteTlt of ca.lcium oxide.was 14 percent by weight and that of alumina was 4 percent by weight. The shapes of the employed aluminum nitride sintered substrates were 5 mm square, 20 mrn square and 50 mrn s~uare respectively.
Further, nickel plating layers of 2 ~m in thickness were formed on the surfaces of the rnetallized layers. On the other hand, copper-tungsten alloy plates oE 1.5 mm in thickness having various compositions.were prepared as radiating members to be joined to the respective aluminum nitride sintered substrates. Nickel plating of 2 ~m in thickness was performed on the surfaces of these copper-tungsten alloy plates, which were then soldered to the respective aluminum nitride sintered subs.t-rates ~y ~rP~
silver solder with interposi.tion o~ stress relieving members of nickel or coppex at, a tempera.ture of 830C.
Examination was.made as to whet.he~ or not the aluminum nitride sintered substrates were cracked and whet~,er or not the cop~er-tungsten alloy plates were warped in the respective samples thus obtained. As shown in Fig. 5, an aluminum nitride sintered substrate 1 and a heat sink member 6 of each sample were joined with each other, to evaluate the degree of wa.rping as the amo~lnt a by a surface roughness tester (product of Tokyo Seimitsu:
E-SP-SOlA). Cracks caused in the respective aluminum nitride sintered substrates were obser~ed by a scanning type electron microscope of 5000 magnifications or a steromicroscope o~ 40 magnifications. Tables 1 to 3 show the results. As to evaluation of warps, those oE not more than 2 ~m with respect to effective length of 1 rnm were regaxded as l~X10 warp", while samples causing warps exceeding 2 ~m with respect to effective length oE 1 mm were regarded as "warped".
The numerals 5, 10 and 20 in "CuW5", "CuW10" and l'CuW20" in Tables indicate contents.of copper in the copper~tungsten alloys. As to the copper-tungsten alloys, thermal expansion coeffi.cients of CuW5, CuW10 and CuW20 were 6.0 to 7.0 x 10 6JK, 6.5 to 7.5 x 10 6/K and 8.5 to 25 9.5 x 10 ~K in a range of the room tempera-ture to 950C.
- 2~ -Further, values of thermal conductivity of CuW5, CuW10 and CuW20 were 180 ~mKr 210 W~mK and 246 W~'mK respectively The wording."cracked'` in Tables indicates that cracks were caused i~ the interiors of the aluminum nitride sintered substxates.
Similar evaluation was also made on reference examples including no interposed layers serv~ng as stress relieving members. Table 4 shows the results.
According to Table 1, no crack nor warp was recognized in samples having interposed layers-, serving as the stress relieving.members in accordance with the present inventionj of at least 100 ~n in thickness.
According to Table 2, no warp nor crack was recoynized in samples having.interposed layers of 500 ~m in thickness.
According to Table 3, no crack nor warp was rec~gnized in samples having interposed layers of 1000 ~m in thickness, while those having.interposed layers o~ less.than and in excess of 1000 ~m in thickness presented cracks and./or warps. As shown in Table 4, all samples of reference examples, including no interposed layers for.serving as stress relieving members, presented warps and/or cracks.
-T~ e 1 ( O S ~
_____ _ Interpo~ed Layer Cu Cu L,ayer wiLh Ni Or_N;__ _ __ _ PlalilJg of ~_~m of ~ r- CuWS ; cu~o CuW20 CuW5 cuwin CuW20 CuW~ CuW10 C~nW20 L yer warped warped warped no warp warped warped no warp no warp w~rped _ _ _ .___ _ _ __ _ .. _._ I_ _ _ _ __.
100 ~m no warp no warp no warp r,o warp no warp no warp no warp no warp no w~rp ___ ._ _ __ _ _ ._ . ..._. ._ _ _.. .... __ _ __ . _ . _ _ . _ _ . 500 ~m no walp no warp 110 warp no war~ no warp no w~rp no warE~ no warp no war~
Tab.le 2 (~ 20 mm) _ _ . _ .
Interposed Layer Cu Cu Layer w;t~ Ni o~ Ni_ _ _ ___ __ __..__ __. . _ __. _._ Plat;nc _oE ~
'I'hickness CuW5 CuW10 Cu~20 CuW5 CuW10 CuW20 CuW5 Cu~10 CuW20 of Inter-, _ _ _ 10 ~m warped warped wa.rpe~ warped warped warped warpea warpe~ warp~d(crack- (crack- ~cr~ck- ~crA(k-ecl) ed) ed) ~d) 100 ~m no warp warped warped no warp warped warpea no warp no war~ wa.rp~d S00 ~m no warp no wa.~p no warp no warp no warp no warp no warp no warE~ n~ wa~E
Table 3 ~ S~ mm) Il~terE~sed L~y~ C~l C~ I.aye~ ~;lh of Ni l'latin of Thichness C~WS CuWlO Cu~20 C~IWS C~WlO C~W20 CuWS CuWl~ ~IW~
I _ _ _ ___ ___ 100 ~m w~rped wal~ped w3rped warp~d warped w3r~ea warp~ warped w~rp~l (crack- (crack- (crack- (crack- (crack- (crack- (crack- (crack- (crack-e-l) ed) ed) ¦ed) led) ed) ~d) ed) ed) 500 l~ warp~d warped warp~ n~ w~rp ~arr!~d war~e~3 no warF n~ wlr~ .~rp~d _ _ ( r~oh-1000 ~ no warp no warp 110 W3rF no warF no warp no w~rp nc> warp no warp 110 w~r~
, I _ l 500 ~m no warp no warp no warp no warp no warp no warp no warp no warp no warp (crack- (crack- (crack- (crack- ~crack- ~crack- ~crack- ~crack- ~c~c~-ed) ed) ed) ed) ed) ed) ed) e~) ed) Table 4 (Reference Example) _ _ _ CUW5 CuW10 CuW20 __ ,_~ I
5 mm warped warp~d warped (craeked)(eracked) I_ a 20 mm ~arped warped warped (cxacked) (cracked)(cracked) I_ I
a ~o ~n warped warped warped (cracked) (cracked!(cracked) Example 2 Samples of alumin~n nitride sintered substrates with metallized layers were prepared by the aEorementioned method as shown in Fig. lB. The metallization processj.n~
of sam~les was perfol-med by app~yiny tungstell paste of pxescribed composi.tion. to the surfaces of respecti.ve samples of the aluminum formed substrates shaped in a configuration such as a green shee~ by the aEorementioned method with screen printing of prescribed patterns, drying, performing debindering and then sintering the s~ne in a nitrogen-hydrogen atmosphere at a temperature of 1850C for 5 minutes Thus, metallized layers were formed on prescribed portions of aluminum nitride sintered substrates. The shapes of the employed aluminum nitride sintered substrates with metallized layers were 5 mm square, 20 mm square and 50 mm sguare of 1.5 mm in thickness respectively.
Further, nickel plating layers were formed on:the surfaces of the metallized layers, simi.larly to Example 1 On the other hand, copper-molybdenum alloy plates of 1.5 mrn in thickness having various compositions:were prepared as radiating members to be joined to.the respective aluminum nitride.sintered.substrates. Nickel plating of 2 llm in thickness was performed on the surfaces of these copper-molybdenum alloy plates, which were then soldered to the respective alumi.num nitride sintered substrates by silver solder with interposition of stress relieving members of nickel or copper in a hydrogen atmosphere at a temperature of 830C.
~ sb~ ~ 6 Examination was made as to cxacks of the aluminnm nitride sintered subs~rates and warps of the copper-molybdenum alloy plates similarly to Example 1.
Tables 5 to 7 show the results.
The numerals 10, 15 and 20 in "CuMolO", "CuMol5" and 'ICuMo20`' in Tables indicate contents of copper in the copper-molybdenum alloys. As to the copper molybdenum alloys, thermal expansion coefficients of CuMolO, C~1015 and CuMo20 were 6.4 to 6.8 x 10 6/K, 7.0 to 7.4 x 10 6/K
and 7.6 to 8.3 x 10 6/K in a range of the room temperat~ e to 950C. Further, values of thermal.conductivity oE
CuMolO, CuMol5 and CuMo20 were 165 W/mK, 184 W/mK and 196 W/mK respectively.
Similar evaluati.on was also made on reference examples includiny no interposed layers serving as stress relieving.members. Table 8 shows the.resul.ts.
According to Table 5, no crack nor warp was recognized in samples having.interposed layer, serving as the stress relieving.members in accordance.with the present invention, of at least 100 ~m in thickness.
According to Table 6, no warp nor crack was recognized in samples.having interposed layers of 500.~m in thickness.
According to Table 7, no crack nor warp was recognized in samples having interposed layers of 1000 ~m in thickness, while those having interposed layers of less than and in - 28 ~
excess of 1000 ~ in th.ickness presente~ cracks and/or warps. As shown in Table 8, all sample~ o~ reference exc~nples, including no interposed layers for serving as stress relieving members, presented warps and/or-cracks.
~ 5 (U~- mln) _. _ Interposed Layer Cu C'u Layer wit}, ~i of Ni _ ~latil) c, ~
Thi<:kne~s CuMolO CuMc~5 CUM~20 1 CuMolO C'uMol.'i CuMo20 Cu~olO CuMolS C~o20 Lay r 10 ~m warped warped warped warped warped warped no warp no warp no warp __ 100 ~m no warp no warp no warp no warp no warp rlo warp no warp n~ warp n~ warp _ _ 500 ~m no warp no warp no warp no warp no warp no warp no warp no warp no W~rE' _ Tc~ble 6 (D 20 n~) Interposed Layer Cu Cu Layer w.ith ~i of N. _ ____ _ _ __ _ _ Pla~in~ _o~_~_Lm Thickness CuMolO CuMol5 CuMo20 CuNolO CuMolj CuMo20 CuMolO C'uMol5 CuMo20 of Inter _ I
10 ~m warped warpe~ warpea warpe~ warpe~ warped warp~ war~e.~ warp~d (crack- ~ crac:k- ( crack- (craok- (crack- (crac:k (cra~k ed) ed) ed) ~d) ed) ed) ed) 1- -- I -- _ 100 ~m warped ¦warped warped warped warped warpe~ wc~rped- warped w~ped SOO ~m no warp no wc~rp no warp no warp no warp no warp no warp no w~r~) no W~l p ¦
~,P'~ ~6 Tc~Ie 7 (~ 50 mm) _ Interpos~.1 Lay~r Cu r,~ J,~y~-- wi~h Hi ~f_N~ Iatinc oE ~ lul I _ Thickne~ CuMolO ~ Hol5 CuMo20 CuMolO CuMol5 C~o20 CuMo10 CuM~15 C'uM.20 o~ Inte.r-_ ~ _ _ _. .. .,._, ,_ _ ,.,.,._ ___ __ _ ._ ___ ___ 100 llm warped warped warp~d w3rped warped warp~d w~rped walped ~Yr~ed (crack- (crack- (crack- (crack- (crack- (crack- (crack- (crack- (crack-ed) ed) ed) ed) ~d) ed) ed) ~d) ~d) __ .. _, . ,, _. ,__. .. , ,, ... ____ ._,_, _ ,. . _, SOO ~m warped w3rped warped no warp warp~d warped no warp no warp w~rp~d edr)ack- eCd)ack-~_ _ _. . __ __ _ l _ _ lOOO ~m no warp no warp no warp no warp no warp no warp na warp no warp no warp 500 ~m no warp no warp no warp no warp no warF no warp no warp no warp no warp (crack- (crack- ~crack- (crack- (cr2ck- (crzck- (crack- (crack- (crack-ed) led) ~d) ed) ed) ed) ed) e~) ed) __ /
Table ~ (~e:Eerence Exa~,p].e) .
CuMolO CuMoW15 CuMo20 5 mm warped wa~ped wa~ped (cracked) (cracked) (cracke~) 20 mm warped warped warped (cracked~ (cracked) ( Cl acked) 50 mm warped warped wal-ped (cracked) lcracked) (cracked) Although the present invention has been described and illustrated in detail, it is c].early understood that the same is by way of illustration.and example only and is not to be taken by way of limitation, the-spirit and scope of the present invention being limited only by the terms of the appended.claims.
." ., , . .. :
Similar evaluation was also made on reference examples including no interposed layers serv~ng as stress relieving members. Table 4 shows the results.
According to Table 1, no crack nor warp was recognized in samples having interposed layers-, serving as the stress relieving.members in accordance with the present inventionj of at least 100 ~n in thickness.
According to Table 2, no warp nor crack was recoynized in samples having.interposed layers of 500 ~m in thickness.
According to Table 3, no crack nor warp was rec~gnized in samples having interposed layers of 1000 ~m in thickness, while those having.interposed layers o~ less.than and in excess of 1000 ~m in thickness presented cracks and./or warps. As shown in Table 4, all samples of reference examples, including no interposed layers for.serving as stress relieving members, presented warps and/or cracks.
-T~ e 1 ( O S ~
_____ _ Interpo~ed Layer Cu Cu L,ayer wiLh Ni Or_N;__ _ __ _ PlalilJg of ~_~m of ~ r- CuWS ; cu~o CuW20 CuW5 cuwin CuW20 CuW~ CuW10 C~nW20 L yer warped warped warped no warp warped warped no warp no warp w~rped _ _ _ .___ _ _ __ _ .. _._ I_ _ _ _ __.
100 ~m no warp no warp no warp r,o warp no warp no warp no warp no warp no w~rp ___ ._ _ __ _ _ ._ . ..._. ._ _ _.. .... __ _ __ . _ . _ _ . _ _ . 500 ~m no walp no warp 110 warp no war~ no warp no w~rp no warE~ no warp no war~
Tab.le 2 (~ 20 mm) _ _ . _ .
Interposed Layer Cu Cu Layer w;t~ Ni o~ Ni_ _ _ ___ __ __..__ __. . _ __. _._ Plat;nc _oE ~
'I'hickness CuW5 CuW10 Cu~20 CuW5 CuW10 CuW20 CuW5 Cu~10 CuW20 of Inter-, _ _ _ 10 ~m warped warped wa.rpe~ warped warped warped warpea warpe~ warp~d(crack- (crack- ~cr~ck- ~crA(k-ecl) ed) ed) ~d) 100 ~m no warp warped warped no warp warped warpea no warp no war~ wa.rp~d S00 ~m no warp no wa.~p no warp no warp no warp no warp no warp no warE~ n~ wa~E
Table 3 ~ S~ mm) Il~terE~sed L~y~ C~l C~ I.aye~ ~;lh of Ni l'latin of Thichness C~WS CuWlO Cu~20 C~IWS C~WlO C~W20 CuWS CuWl~ ~IW~
I _ _ _ ___ ___ 100 ~m w~rped wal~ped w3rped warp~d warped w3r~ea warp~ warped w~rp~l (crack- (crack- (crack- (crack- (crack- (crack- (crack- (crack- (crack-e-l) ed) ed) ¦ed) led) ed) ~d) ed) ed) 500 l~ warp~d warped warp~ n~ w~rp ~arr!~d war~e~3 no warF n~ wlr~ .~rp~d _ _ ( r~oh-1000 ~ no warp no warp 110 W3rF no warF no warp no w~rp nc> warp no warp 110 w~r~
, I _ l 500 ~m no warp no warp no warp no warp no warp no warp no warp no warp no warp (crack- (crack- (crack- (crack- ~crack- ~crack- ~crack- ~crack- ~c~c~-ed) ed) ed) ed) ed) ed) ed) e~) ed) Table 4 (Reference Example) _ _ _ CUW5 CuW10 CuW20 __ ,_~ I
5 mm warped warp~d warped (craeked)(eracked) I_ a 20 mm ~arped warped warped (cxacked) (cracked)(cracked) I_ I
a ~o ~n warped warped warped (cracked) (cracked!(cracked) Example 2 Samples of alumin~n nitride sintered substrates with metallized layers were prepared by the aEorementioned method as shown in Fig. lB. The metallization processj.n~
of sam~les was perfol-med by app~yiny tungstell paste of pxescribed composi.tion. to the surfaces of respecti.ve samples of the aluminum formed substrates shaped in a configuration such as a green shee~ by the aEorementioned method with screen printing of prescribed patterns, drying, performing debindering and then sintering the s~ne in a nitrogen-hydrogen atmosphere at a temperature of 1850C for 5 minutes Thus, metallized layers were formed on prescribed portions of aluminum nitride sintered substrates. The shapes of the employed aluminum nitride sintered substrates with metallized layers were 5 mm square, 20 mm square and 50 mm sguare of 1.5 mm in thickness respectively.
Further, nickel plating layers were formed on:the surfaces of the metallized layers, simi.larly to Example 1 On the other hand, copper-molybdenum alloy plates of 1.5 mrn in thickness having various compositions:were prepared as radiating members to be joined to.the respective aluminum nitride.sintered.substrates. Nickel plating of 2 llm in thickness was performed on the surfaces of these copper-molybdenum alloy plates, which were then soldered to the respective alumi.num nitride sintered substrates by silver solder with interposition of stress relieving members of nickel or copper in a hydrogen atmosphere at a temperature of 830C.
~ sb~ ~ 6 Examination was made as to cxacks of the aluminnm nitride sintered subs~rates and warps of the copper-molybdenum alloy plates similarly to Example 1.
Tables 5 to 7 show the results.
The numerals 10, 15 and 20 in "CuMolO", "CuMol5" and 'ICuMo20`' in Tables indicate contents of copper in the copper-molybdenum alloys. As to the copper molybdenum alloys, thermal expansion coefficients of CuMolO, C~1015 and CuMo20 were 6.4 to 6.8 x 10 6/K, 7.0 to 7.4 x 10 6/K
and 7.6 to 8.3 x 10 6/K in a range of the room temperat~ e to 950C. Further, values of thermal.conductivity oE
CuMolO, CuMol5 and CuMo20 were 165 W/mK, 184 W/mK and 196 W/mK respectively.
Similar evaluati.on was also made on reference examples includiny no interposed layers serving as stress relieving.members. Table 8 shows the.resul.ts.
According to Table 5, no crack nor warp was recognized in samples having.interposed layer, serving as the stress relieving.members in accordance.with the present invention, of at least 100 ~m in thickness.
According to Table 6, no warp nor crack was recognized in samples.having interposed layers of 500.~m in thickness.
According to Table 7, no crack nor warp was recognized in samples having interposed layers of 1000 ~m in thickness, while those having interposed layers of less than and in - 28 ~
excess of 1000 ~ in th.ickness presente~ cracks and/or warps. As shown in Table 8, all sample~ o~ reference exc~nples, including no interposed layers for serving as stress relieving members, presented warps and/or-cracks.
~ 5 (U~- mln) _. _ Interposed Layer Cu C'u Layer wit}, ~i of Ni _ ~latil) c, ~
Thi<:kne~s CuMolO CuMc~5 CUM~20 1 CuMolO C'uMol.'i CuMo20 Cu~olO CuMolS C~o20 Lay r 10 ~m warped warped warped warped warped warped no warp no warp no warp __ 100 ~m no warp no warp no warp no warp no warp rlo warp no warp n~ warp n~ warp _ _ 500 ~m no warp no warp no warp no warp no warp no warp no warp no warp no W~rE' _ Tc~ble 6 (D 20 n~) Interposed Layer Cu Cu Layer w.ith ~i of N. _ ____ _ _ __ _ _ Pla~in~ _o~_~_Lm Thickness CuMolO CuMol5 CuMo20 CuNolO CuMolj CuMo20 CuMolO C'uMol5 CuMo20 of Inter _ I
10 ~m warped warpe~ warpea warpe~ warpe~ warped warp~ war~e.~ warp~d (crack- ~ crac:k- ( crack- (craok- (crack- (crac:k (cra~k ed) ed) ed) ~d) ed) ed) ed) 1- -- I -- _ 100 ~m warped ¦warped warped warped warped warpe~ wc~rped- warped w~ped SOO ~m no warp no wc~rp no warp no warp no warp no warp no warp no w~r~) no W~l p ¦
~,P'~ ~6 Tc~Ie 7 (~ 50 mm) _ Interpos~.1 Lay~r Cu r,~ J,~y~-- wi~h Hi ~f_N~ Iatinc oE ~ lul I _ Thickne~ CuMolO ~ Hol5 CuMo20 CuMolO CuMol5 C~o20 CuMo10 CuM~15 C'uM.20 o~ Inte.r-_ ~ _ _ _. .. .,._, ,_ _ ,.,.,._ ___ __ _ ._ ___ ___ 100 llm warped warped warp~d w3rped warped warp~d w~rped walped ~Yr~ed (crack- (crack- (crack- (crack- (crack- (crack- (crack- (crack- (crack-ed) ed) ed) ed) ~d) ed) ed) ~d) ~d) __ .. _, . ,, _. ,__. .. , ,, ... ____ ._,_, _ ,. . _, SOO ~m warped w3rped warped no warp warp~d warped no warp no warp w~rp~d edr)ack- eCd)ack-~_ _ _. . __ __ _ l _ _ lOOO ~m no warp no warp no warp no warp no warp no warp na warp no warp no warp 500 ~m no warp no warp no warp no warp no warF no warp no warp no warp no warp (crack- (crack- ~crack- (crack- (cr2ck- (crzck- (crack- (crack- (crack-ed) led) ~d) ed) ed) ed) ed) e~) ed) __ /
Table ~ (~e:Eerence Exa~,p].e) .
CuMolO CuMoW15 CuMo20 5 mm warped wa~ped wa~ped (cracked) (cracked) (cracke~) 20 mm warped warped warped (cracked~ (cracked) ( Cl acked) 50 mm warped warped wal-ped (cracked) lcracked) (cracked) Although the present invention has been described and illustrated in detail, it is c].early understood that the same is by way of illustration.and example only and is not to be taken by way of limitation, the-spirit and scope of the present invention being limited only by the terms of the appended.claims.
." ., , . .. :
Claims (9)
1. A member for a semiconductor apparatus for carrying or holding a semiconductor device, said member comprising:
an insulating member of aluminum nitride having a major surface to face said semiconductor device;
a radiating member to be joined to said insulating member, being mainly formed of a material selected from group of a copper tungsten alloy and a copper-molybdenum alloy;
a stress relieving member interposed between said insulating member and said radiating member; and a soldering member for joining said insulating member, said stress relieving member and said radiating member with each other, said stress relieving member being prepared by any of a soft metal and a soft alloy having high plastic deformability in order to relax, by its own plastic deformation, thermal stress caused by difference in thermal expansion coefficient between said insulating member and said radiating member in a cooling step upon soldering.
an insulating member of aluminum nitride having a major surface to face said semiconductor device;
a radiating member to be joined to said insulating member, being mainly formed of a material selected from group of a copper tungsten alloy and a copper-molybdenum alloy;
a stress relieving member interposed between said insulating member and said radiating member; and a soldering member for joining said insulating member, said stress relieving member and said radiating member with each other, said stress relieving member being prepared by any of a soft metal and a soft alloy having high plastic deformability in order to relax, by its own plastic deformation, thermal stress caused by difference in thermal expansion coefficient between said insulating member and said radiating member in a cooling step upon soldering.
2. A member for a semiconductor apparatus in accordance with claim 1, wherein said stress relieving member is formed of a material selected from a group of copper, a copper alloy, nickel and a nickel alloy.
3. A member for a semiconductor apparatus in accordance with claim 1, wherein said insulating member includes a substrate having a major surface to be provided thereon with said semiconductor device.
4. A member for a semiconductor apparatus in accordance with claim 1, wherein said insulating member includes a covering member provided above said semiconductor device to protect the same.
5. A member for a semiconductor apparatus in accordance with claim 1, wherein said insulating member includes a sintered body.
6. A member for a semiconductor apparatus-in accordance with claim 1, further-comprising a metallized layer formed in a junction surface of said insulating member.
7. A member for a semiconductor apparatus in accordance with claim 6, wherein said metallized layer contains at least one metal within tungsten and molybdenum, at least one aluminum compound selected from a group of aluminum nitride, aluminum oxide and aluminum oxynitride, and calcium oxide.
8. A member for a semiconductor apparatus in accordance with claim 6, further comprising a plating layer formed in a junction surface between said metallized layer and said soldering member.
9. A member for a semiconductor device in accordance with claim 8, further comprising a plating layer formed in a junction surface between-said radiating member and said soldering member.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP165191/1987 | 1987-07-03 | ||
| JP16519187 | 1987-07-03 |
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| CA1284536C true CA1284536C (en) | 1991-05-28 |
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| CA000570628A Expired - Fee Related CA1284536C (en) | 1987-07-03 | 1988-06-28 | Member for semiconductor apparatus |
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| US (1) | US4886709A (en) |
| EP (1) | EP0297569B1 (en) |
| KR (1) | KR920003594B1 (en) |
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|---|---|---|---|---|
| US5529852A (en) * | 1987-01-26 | 1996-06-25 | Sumitomo Electric Industries, Ltd. | Aluminum nitride sintered body having a metallized coating layer on its surface |
| JPH02263445A (en) * | 1988-12-23 | 1990-10-26 | Toshiba Corp | Aluminum nitride substrate and semiconductor using same |
| US5292552A (en) * | 1989-12-20 | 1994-03-08 | Sumitomo Electric Industries, Ltd. | Method for forming metallized layer on an aluminum nitride sintered body |
| DE69013310T2 (en) * | 1989-12-22 | 1995-04-27 | Westinghouse Electric Corp | Housing for power semiconductor components. |
| US5109268A (en) * | 1989-12-29 | 1992-04-28 | Sgs-Thomson Microelectronics, Inc. | Rf transistor package and mounting pad |
| DE69128601T2 (en) * | 1990-10-26 | 1998-06-04 | Sumitomo Electric Industries | Method for producing heat-radiating substrates for mounting semiconductors and semiconductor package produced according to this method |
| US5395679A (en) * | 1993-03-29 | 1995-03-07 | Delco Electronics Corp. | Ultra-thick thick films for thermal management and current carrying capabilities in hybrid circuits |
| JPH0864724A (en) * | 1994-07-25 | 1996-03-08 | General Electric Co <Ge> | Electronic device containing adaptive metal chip-substrate bonding layer |
| JP3845925B2 (en) * | 1996-02-05 | 2006-11-15 | 住友電気工業株式会社 | Semiconductor device member using aluminum nitride substrate and method for manufacturing the same |
| US6783867B2 (en) * | 1996-02-05 | 2004-08-31 | Sumitomo Electric Industries, Ltd. | Member for semiconductor device using an aluminum nitride substrate material, and method of manufacturing the same |
| JPH1065294A (en) * | 1996-08-14 | 1998-03-06 | Toshiba Corp | Ceramic wiring board and manufacture thereof |
| US6004624A (en) | 1997-07-02 | 1999-12-21 | International Business Machines Corporation | Method for the controlling of certain second phases in aluminum nitride |
| US5988488A (en) * | 1997-09-02 | 1999-11-23 | Mcdonnell Douglas Corporation | Process of bonding copper and tungsten |
| US6089444A (en) * | 1997-09-02 | 2000-07-18 | Mcdonnell Douglas Corporation | Process of bonding copper and tungsten |
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| DE102004054996B4 (en) * | 2003-12-06 | 2013-07-18 | Schaeffler Technologies AG & Co. KG | Electronic device |
| US7964883B2 (en) * | 2004-02-26 | 2011-06-21 | Lighting Science Group Corporation | Light emitting diode package assembly that emulates the light pattern produced by an incandescent filament bulb |
| US20050225222A1 (en) * | 2004-04-09 | 2005-10-13 | Joseph Mazzochette | Light emitting diode arrays with improved light extraction |
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| WO2007005003A1 (en) * | 2005-06-30 | 2007-01-11 | Lamina Ceramics, Inc. | Light emitting diode package assembly that emulates the light pattern produced by an incandescent filament bulb |
| JP2007305962A (en) * | 2006-05-12 | 2007-11-22 | Honda Motor Co Ltd | Power semiconductor module |
| DE102009021236A1 (en) * | 2009-05-14 | 2010-12-02 | Osram Gesellschaft mit beschränkter Haftung | Light-emitting diode module and lighting unit with light-emitting diode module |
| KR101242218B1 (en) * | 2011-01-07 | 2013-03-11 | 에이텍 테크놀로지 코포레이션 | Lighting device and method for forming the same |
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| DE102017119346A1 (en) | 2017-08-24 | 2019-02-28 | Osram Opto Semiconductors Gmbh | Component with buffer layer and method for producing a component |
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Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57181356A (en) * | 1981-04-30 | 1982-11-08 | Hitachi Ltd | Sintered aluminum nitride body with high heat conductivity |
| JPH0810710B2 (en) * | 1984-02-24 | 1996-01-31 | 株式会社東芝 | Method for manufacturing good thermal conductive substrate |
| US4656101A (en) * | 1984-11-07 | 1987-04-07 | Semiconductor Energy Laboratory Co., Ltd. | Electronic device with a protective film |
| DE3523061A1 (en) * | 1985-06-27 | 1987-01-02 | Siemens Ag | Semiconductor chip arrangement |
| JPS62197379A (en) * | 1986-02-20 | 1987-09-01 | 株式会社東芝 | Aluminum nitride substrate |
| DE3883873T2 (en) * | 1987-06-30 | 1994-01-05 | Sumitomo Electric Industries | Carrier element for semiconductor apparatus. |
-
1988
- 1988-06-28 CA CA000570628A patent/CA1284536C/en not_active Expired - Fee Related
- 1988-06-29 EP EP88110419A patent/EP0297569B1/en not_active Expired - Lifetime
- 1988-06-29 DE DE3888880T patent/DE3888880T2/en not_active Expired - Fee Related
- 1988-06-29 KR KR1019880007889A patent/KR920003594B1/en not_active IP Right Cessation
- 1988-07-01 US US07/214,508 patent/US4886709A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0297569A3 (en) | 1990-07-11 |
| KR920003594B1 (en) | 1992-05-04 |
| DE3888880T2 (en) | 1994-07-28 |
| EP0297569B1 (en) | 1994-04-06 |
| EP0297569A2 (en) | 1989-01-04 |
| KR890003021A (en) | 1989-04-12 |
| US4886709A (en) | 1989-12-12 |
| DE3888880D1 (en) | 1994-05-11 |
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| MKLA | Lapsed |