US3661117A

US3661117A - Apparatus for depositing thin lines

Info

Publication number: US3661117A
Application number: US881746A
Authority: US
Inventors: William L Cornelius; John G Martner
Original assignee: Stanford Research Institute
Current assignee: SRI International Inc
Priority date: 1969-12-03
Filing date: 1969-12-03
Publication date: 1972-05-09
Anticipated expiration: 1989-05-09

Abstract

An apparatus for depositing thin lines of conducting, semiconducting or dielectric material on a substrate including a crucible having a vaporizable material charge receiving chamber and a vapor chamber. A first tube for introducing a flow of carrier gas and a heated capillary tube penetrate the vapor compartment. On heating the crucible to a temperature above the evaporation temperature of the charge, the charge evaporates and is pushed through the capillary tube by the carrier gas. The stream of carrier gas and vapor deposits dots or lines on the target. Patterns are produced by translating the target with respect to the crucible.

Description

United States Patent Cornelius et al.

[541 APPARATUS FOR DEPOSITING THIN LINES [72] Inventors: William L. Cornelius, Mountain View;

John G. Mariner, Athert'on, both of Calif.

[73] Assignee: Stanford Research Institute, Menlo Park,

Calif.

22 Filed: Dec. 3, 1969 [21] Appl. No.: 881,746

[52] U.S.Cl ..1l8/48,2l9/275 1451 May 9,1972

Primary E.\'aminerMorris Kaplan. Attor11ey-Samuel Lindenberg and Arthur Freilich [57] ABSTRACT An apparatus for depositing thin lines of conducting, semiconducting or dielectric material on a substrate including a crucible having a vaporizable material charge receiving chamber and a vapor chamber. A first tube for introducing a flow of carrier gas and a heated capillary tube penetrate the vapor compartment. On heating the crucible to a temperature above the evaporation temperature of the charge, the charge evaporates and is pushed through the capillary tube by the carrier gas. The stream of carrier gas and ,vapor deposits dots or lines on the target. Patterns are produced by translating the target with respect to the crucible.

8 Claims, 2 Drawing Figures MOTOR PATENTEDMAY 9 I972 8 3 m Ellu R T w VI RC A R T m mH CRUCIBLE HEATER CONTROLLER FIG.

" FIG. 2

MOTOR INVENTORS.

WILLIAM L.CORNEL|US JOHN G. MARTNER ATTORNEYS.

BACKGROUND OF THE INVENTION 1. Field of the Invention The-present invention relates to an apparatus for depositing thin lines-on a substrate, and more particularly, this invention relates to deposition of patterns of thin lines on a substrate without the use of masks and associated equipment.

2. Description of the Prior Art Devices formed by depositing a pattern on a substrate find many uses by the integrated circuit, transistor, semi-conductor and allied industries. Most of these devices are produced by vacuum-depositing a pattern of material through a mask onto the substrate. This is not a totally satisfactory procedure due to the time and expenserequired to produce the masks and to maintain them in alignment during deposition.

It would be preferable to directly write the pattern of the material on the substrate. A technique where a vacuumevaporating furnace containing a large hole in the center of the lid is utilized to roughly direct a vapor beam toward a target, has been previously tested and found useful. However, it has been difficult to funnel the stream of atoms into a small target area.

When a metal or a dielectric material is heated, emission vapor is initiated at a temperature below the melting point of material. If the melting process is conducted in vacuum, the

vapors will expand tofill the whole environment. Vapor emission starts at the surface and the emitted atoms are considered to leave the surface and travel in all directions. It is known, that a given point on the surface acts as a point source. However, the density distribution of atoms leaving is not uniform in all directions. It follows, instead; a cosine distribution with a maximum number leaving in a direction normal to the emitting surface point. This phenomena makes it difficult to deliver the stream of atoms in high resolution onto a small target area. Furthermore, since the atoms are mostly neutral in charge, they cannot be focused either with electric or magnetic fields.

OBIECTS AND SUMMARY OF THE INVENTION It is therefore an object of this invention to directly deposit thin lines onto a substrate.

Yet another object of this invention is the provision of an improved apparatus for depositing thin lines in high resolution without the use of masks and associated equipment.

A further object of the present invention is the provision of an improved deposition apparatus that is simple to construct and operate and effectively funnels a stream of vaporous atoms onto a small target area.

These and other objects and many attendant advantages of the invention will become apparent as the description proceeds.

The deposition apparatus, in accordance with the invention, includes in combination a closed crucible for receiving a charge of vaporizable material associated with a heating means for maintaining the chargev at a temperature above the evaporation temperature of the material. A small diameter tube penetrates the crucible and has a first end disposed within the vapor head space above the charge and has a second end directed toward a target substrate. The tube is as sociated with heating means to maintain the inner wall ofthe tube at a temperature above the vaporization temperature of the material and preferably at a temperature slightly higher than the temperature within the crucible. A source of carrier gas may also be introduced into the crucible through a second small diameter tube.

The deposition apparatus is operated by energizing the separate heating elements to maintain the crucible at a first temperature above the evaporating temperature of the charge of material and the capillary tubing at a slightly higher tem' perature. The supply of carrier gas is initiated. The stream of carrier gas mixes with the vapor leaving the surface of the charge and pushes the mixture through the heated tube. The hot walls of the tube prevent condensation of material within the tube. The mixture of gases emitted from the outer end of the heated tube are directed toward the substrate and condensed thereon. By translating the substrate with respect to the end of the tube, a series of fine-lines and dotscan be drawn on the surface of the substrate.

The invention will become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a first embodiment of the invention; and

FIG. 2 is a schematic view of a second embodiment of an apparatusin accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, the deposition system, according to the invention, generally includes a crucible 10, a substrate support assembly 12 and a source of carrier gas 14. The crucible 10 is a closed body formed from a lower cylindrical vessel portion 16 and a lid 18. The upper inner edge of the vessel is internally threaded as is the outer lower edge of the lid I8. When the lid 18 is assembled to the vessel 16, a vapor-tight chamber is formed. The lower portion of the vessel -16 receives a charge 20 of vaporizable material and the upper portion forms a head space 22 for collecting the vapor atoms leaving the top surface 24 of the charge 20. The vessel 16 is surrounded with a heating coil 26 throughout the length thereof. The ends of the heating coil 26 are connected to a variable power supply and controller 28 which can be selectively adjusted to maintain the temperature of the crucible above the vaporization temperature of the charge 20. This will both melt the charge and cause vaporization of atoms from the charge and will also prevent condensation of the vapor on the internal walls of the vessel 16.

' A small diameter aperture is provided in the lid 18 of the crucible 10. A tube 30 is inserted into the hole and is suitably joined to the walls of the lid 18 such that a gas-tight seal is formed. One end 32 of the tube 30 communicates with the head space 22 while the other nozzle end 34 is directed at the target substrate member 36. The portion of the tube 30'exterior to the crucible 10 is surrounded with a heating coil 38. The ends of the coil 38 are electrically connected to a variable power supply and controller 40. The controller 40 is selectively adjusted to maintain the temperature of the tube walls 30 at a temperature above the condensation temperature of the vapor. Suitably a temperature differential at least 50 C above that of the crucible is maintained to prevent condensation within the tube 30.

The source of carrier gas 14 can be in the form of a pressurized cylinder 42 containing a valve 44. A length of tubing 46 is attached to the cylinder 42 and-penetrates the wall of the vessel 16 at a level containing the hot molten charge 20. The upper end 48 of the tubing 46 extends into the head space 22. In this manner the carrier gas will be heated by the time it emerges into the head space 22. This will prevent cooling of the vapor and avoid condensation on the inside of the crucible 10 or within the capillary tube 30.

The target support assembly 12 includes a moveable shutter 50 disposed in front of the nozzle end 34 of the tube 30. The shutter 50 is attached through a linking rod 52 to a rotatable axle 54. On rotation of knob 56, the shutter plate 50 is rotated into or out of position in front of the nozzle 34. The substrate 36 is positioned immediately behind shutter plate 50 and in position to receive the jet output from tube 30. The substrate 36 is supported between clamps 58. The back of the clamping members 58 is provided with a set of teeth 60. A gear 62 engages the teeth 60. On rotation of gear 62 the substrate is translated in the vertical direction with respect to the noule opening 34. A second gear and set of grooves may be provided to translate the substrate support assembly 12 in a horizontal direction so that the substrate may be externally moved along two axes to trace a line or any desired pattern.

The deposition apparatus of the invention may be used to form lines of conductive metal such as silver, copper, gold, cadmium, platinum, palladium or aluminum or dielectric or semi-conductor material such as zinc oxide or cadmium sulfide to form microwave or piezoelectric transducer devices. The carrier gas is preferably an inert noble gas such as xenon, argon or neon. In certain cases a reactive gas such as hydrogen can be utilized in combination with a reducible metal compound which will react at the surface of the substrate to form a deposit of metal or metal compound.

The apparatus is constructed of high temperature refractory material such as alumina, zirconia or carbon. The pressure within the crucible can be maintained at very low vacuum but is suitably operated at slightly above ambient if contamination with ambient gases is not deleterious to the finished surface. The flow of carrier gas is maintained at a very low level sufficient to maintain a uniform controlled flow of vaporous material through the capillary tube. The flow is generally maintained below 10 cc. per second and preferably below 5 cc. per second.

The capillary tube is also formed of a refractory material such as alumina and the internal diameter of the tube is selected considering the desired line size and flow rate desired, The internal diameter is usually below 20 mils and is preferably about 1 to mils. The line width is also dependent on the spacing of the end of the capillary tube from the substrate and wider spacing will provide wider line widths with less resolution and thinner deposits and in the converse thicker deposits, higher resolution and thinner line sizes will be provided with closer spacing. Typically the spacing is maintained below 250 mils and is usually from 10 to 100 mils. The thickness of the line deposited also depend on the rate of translation of the substrate.

The substrate may be formed of many materials such as a ceramic, glass, organic resin, metal foil or resin impregnated laminates or glass fiber filled resinous sheets.

The deposition apparatus is operated by placing a charge 20 of vaporizable material within the vessel 16 and assembling the lid 18. The controller 28 is adjusted to a temperature above the evaporation point of the charge 20. The head space 22 is then evacuated by purging with carrier gas or preferably by attaching a source of vacuum to the nozzle 34 of the capillary tube 30. The controller 40 is set to heat the walls of the tube 30 to a temperature 50 to 300 C. higher than that of the vessel 16. Valve 44 is open to provide a flow of carrier gas into the head space 22.

After a steady flow of a mixture of carrier gas and vapor is leaving the nozzle 34 knob 56 is rotated to open the shutter plate 50 and gear 62 is rotated to translate the substrate 36. A thin line of material is deposited on the substrate 36. Plural deposition assemblies may be utilized to simultaneously write parallel lines on the substrate. After the line has been written across the face of the substrate 36, the shutter plate 50, is rotated into closed position.

The device of FIG. 1 was operated by charging the crucible with silver utilizing argon as the carrier gas. The crucible was heated to a temperature of about 800 C. while the capillary tube was maintained at a temperature of 850 C. The substrate is kept at a much lower temperature than the vapor, thus producing condensation on the receiving surface. With this arrangement a series of fine lines and dots were drawn on the surface of microscope slides. The contours observed were clean enough to make use of masks unnecessary. The line thickness was controlled by the speed of travel of the substrate, the line width of the aperture of the capillary tube and the distance of the substrate from the capillary nozzle. The

electrical resistivity along the lines was found to be 0.5 ohms/cm. and the boundaries of the line exhibited a slight fringing effect when the end of the emitting tube was located about 0.5 cm. from the target surface. As this distance was decreased the fringing effect was less pronounced.

A further embodiment of the invention is illustrated in FIG. 2. The crucible 70 in this case is in the form of an elongated cylinder 72 having a sealed, removable end plate 74 on one end, and a closed integral plate 76 on the other end. A spring loaded pressure release 84, is provided in end wall 76.

The length of the crucible is surrounded with a heating filament 86. Conductors 88 are attached to the ends of the fila-- ment 86 and to a variable power source and controller, not shown.

Each end plate is provided with an axially mounted

cylindrical bearing member

90, 92. Bearing member 92 receives a shouldered pivot pin 94. The inner enlarged shoulder portion of pin 94 is attached to the inner face of the end wall 76. The pin 94 extends through a support 98 and the outer end is attached to a pulley 100. The pulley 100 is driven by pulley 102 through a drive belt 104.

Bearing member 90 receives a pivot pin 106. The outer end of pin 106 is fixedly mounted in an aperture within a support member 108. A support 110 extends from the inner end of pin 106 and a baffle plate 112 is mounted on the end thereof in a direction normal to the aperture 83 in the plate 82.

A vapor barrel 114 in the form of a ceramic crucible tube is inserted through the removable end plate 74 and has an end 116 opening into the vapor chamber 80. The outer portion of the barrel 1 14 is surrounded with a heating filament 120. Electrical leads 122 are connected to the ends of the filament and to a variable power source and controller, not shown. A shutter plate 126 and a translatable substrate 128 are mounted in front of the nozzle 124 of the barrel member 114.

The apparatus of FIG. 2 may be operated without an independent supply of carrier gas. The vapor leaving the top of the charge 20 is slowed down by means of the baffle plate 112 and by means of the constricted output provided by the small diameter capillary tube 114. By rotation of the crucible during deposition, dot or circular patterns may be deposited on the substrate 128. By rotation of the crucible through a partial arc and then maintaining the crucible stationary while the substrate 128 is translated, parallel lines may be deposited.

It is to be understood that only preferred embodiments of the invention have been disclosed and that numerous substitutions, alterations and modifications may be practised without departing from the spirit and scope of the invention as defined in the following claims.

What is claimed is:

l. A system for depositing a fine line of conducting, dielectric or semi-conducting material on a substrate comprising:

a closed crucible having a charge receiving chamber and a vapor chamber, a wall of said crucible defining a first aperture;

a partition means forming a common wall structure between said chambers and including means therein communicating said charge receiving and vapor chambers;

first heating means for maintaining said chambers at a temperature above the evaporation temperature of said material;

an elongated small diameter barrel means inserted through the aperture, the barrel having an internal diameter below 20 mils, a first end communicating with the vapor chamber and a second end terminating in a nozzle;

second heating means for heating said barrel to a temperature above the evaporation temperature of the material;

substrate support means facing said nozzle, disposed in a plane transverse to the axis of the nozzle and spaced no more than 250 mils from the nozzle; and

translation means for moving said support means relative to said nozzle in vertical and horizontal directions within said plane.

2. A deposition system according to claim 1 in which the internal diameter of said barrel is from 1 to 10 mils.

3.. A deposition system according to claim 2 in which said barrel is formed of a refractory material.

4. A deposition system according to claim 1 in which said first and second heating means each comprise a heating filament wound respectively around said crucible and said barrel.

5. A deposition system according to claim 1 in which the translation means include means for rotating the crucible.

6. A deposition system according to'claim 1 in which the substratesupport means includes a substrate clamping means for positioning said support from to 100 mils from the nozzle and said translation means includes means connected to said clamping means for translating the substrate in a horizontal and vertical directions in a plane transverse to the nozzle.

7. A deposition system according to claim 6 further including shutter means mounted between said nozzle and said support means.

8. A deposition apparatus for depositing a pattern of fme lines of a conducting, semi-conducting or dielectric material onto a substrate comprising:

an elongated, hollow, cylindrical,vapor tight, refractory the wall of the vessel intermediate said ends dividing the vessel intoa charge receiving compartment and a vapor compartment;

a first insulated, electrical heating coil surrounding the vessel for heating the compartments to a temperature above the vaporization temperature of said material;

a vapor output barrel having a first portion inserted through the vessel end adjacent the vapor compartment and having a first end terminating in the vapor compartment and a second portion extending from the vessel terminating in a nozzle;

a second, insulated, electrical heating coil surrounding the second portion of the barrel for heating the second portion to at least the vaporization temperature of the material;

baffle means mounted within the vapor compartment between the central aperture of the plate member and the first end of the nozzle;

substrate support means mounted in a plane transverse to the axis of the vessel facing the nozzle;

translation means connected to the support means for translating the support means in said plane; and

shutter means disposed between the nozzle and the substrate support means.

Claims

1. A system for depositing a fine line of conducting, dielectric or semi-conducting material on a substrate comprising: a closed crucible having a charge receiving chamber and a vapor chamber, a wall of said crucible defining a first aperture; a partition means forming a common wall structure between said chambers and including means therein communicating said charge receiving and vapor chambers; first heating means for maintaining said chambers at a temperature above the evaporation temperature of said material; an elongated small diameter barrel means inserted through the aperture, the barrel having an internal diameter below 20 mils, a first end communicating with the vapor chamber and a second end terminating in a nozzle; second heating means for heating said barrel to a temperature above the evaporation temperature of the material; substrate support means facing said nozzle, disposed in a plane transverse to the axis of the nozzle and spaced no more than 250 mils from the nozzle; and translation means for moving said support means relative to said nozzle in vertical and horizontal directions within said plane.

3. A deposition system according to claim 2 in which said barrel is formed of a refractory material.

6. A deposition system according to claim 1 in which the substrate support means includes a substrate clamping means for positioning said support from 10 to 100 mils from the nozzle and said translation means includes means connected to said clamping means for translating the substrate in a horizontal and vertical directions in a plane transverse to the nozzle.

8. A deposition apparatus for depositing a pattern of fine lines of a conducting, semi-conducting or dielectric material onto a substrate comprising: an elongated, hollow, cylindrical, vapor tight, refractory vessel having first and second vapor tight ends; bearing means connected to each of said ends; rotation means connected to said bearing means for rotating the cylindrical vessel; a plate member having a central aperture mounted across the wall of the vessel intermediate said ends dividing the vessel into a charge receiving compartment and a vapor compartment; a first insulated, electrical heating coil surrounding the vessel for heating the compartments to a temperature above the vaporization temperature of said material; a vapor output barrel having a first portion inserted through the vessel end adjacent the vapor compartment and having a first end terminating in the vapor compartment and a second portion extending from the vessel terminating in a nozzle; a second, insulated, electrical heating coil surrounding the second portion of the barrel for heating the second portioN to at least the vaporization temperature of the material; baffle means mounted within the vapor compartment between the central aperture of the plate member and the first end of the nozzle; substrate support means mounted in a plane transverse to the axis of the vessel facing the nozzle; translation means connected to the support means for translating the support means in said plane; and shutter means disposed between the nozzle and the substrate support means.