WO1997001864A1

WO1997001864A1 - Removal rate behavior of spin-on dielectrics with chemical mechanical polish

Info

Publication number: WO1997001864A1
Application number: PCT/US1996/010836
Authority: WO
Inventors: Lynn Forester; Dong K. Choi; Reza Hosseini
Original assignee: Alliedsignal Inc.
Priority date: 1995-06-26
Filing date: 1996-06-26
Publication date: 1997-01-16
Also published as: CN1196829A; JPH10510399A; KR100434929B1; US5952243A; JP3264936B2; DE69634800D1; KR19990028284A; CN1129173C; DE69634800T2; EP0836746B1; EP0836746A1

Abstract

A method for forming a gap-filled, planarization structure of dielectric materials on a substrate topography useful for forming microelectronic devices. A dielectric material is first deposited as continuous, dry dielectric layer, preferably a SOG layer. Then the dielectric layer is partially removed by chemical-mechanical polishing (CMP). The chemical and mechanical properties of the structure can be chosen by varying the composition of the SOG layer and the subsequent CMP conditions.

Description

REMOVAL RATE BEHAVIOR OF SPIN-ON DIELECTRICS WITH

5 CHEMICAL MECHANICAL POLISH

CROSS REFERENCE TO RELATED APPLICAΗON

This appUcation claims the benefit of U.S. provisional application serial

number 60/000,515, filed June 26, 1995 (pending) which is incorporated

l o herein by reference.

BACKGROUND OF THE INVENTION FTFT D OF THE INVENTION

The present invention relates to the preparation of substrates used in the

15 manufacture of integrated circuits ("IC"), multichip modules, printed circuit boards, high-speed logic devices, flat panel displays, and other

microelectronic devices. More particularly, the invention pertains to an

improved technique for filling surface voids, leveling spaces between metal contacts and planarizing dielectric layers of substrates suitable for

20 use in the manufacture ofthe above submicron size devices. This is done using spin-on glass materials together with a chemical mechanical

polishing process. DESCRIPTION OF THE PRIOR ART

A continuing trend in semiconductor technology is the formation of integrated circuit chips having more and faster circuits thereon. Such

ultralarge scale integration has resulted in a continued shrinkage of

feature sizes with the result that a large number of devices are available on a single chip. With a limited chip surface area, the interconnect density

typically expands above the substrate in a multi-level arrangement and the

devices have to be interconnected across these multiple levels. The

interconnects must be electrically insulated from each other except where

designed to make contact. Usually electrical insulation requires

depositing or spinning-on dielectric films onto a surface. See, i.e., "Spin/Bake Cure Procedure for Spin-On-Glass Materials for Interlevel and Intermetal Dielectric Planarization" brochure by AlliedSignal Inc. (1994)(thermally cured spun-on films).

A key processing difficulty associated with the formation of local

interconnects is the topography ofthe device surface. Not only is the

substrate surface itself quite non-planar, but device forming processes

additionally create topographical irregularities such as gaps thereon. Loss

of planarity can cause many problems which can adversely impact

manufacturing yield including failure to open vias due to interlevel dielectric thickness disparity, poor adhesion to underlying materials, step

coverage, as well as depth-of-focus problems. Thus the ability to fill narrow gaps in IC substrates is critical for forming sub-micron size

elements thereon. Various substrate gap filling techniques known in the art include deposit-etch-deposit cycles, and applications of Sub- Atmospheric Tetra-Ethyl Ortho Silicate (SATEOS), Atmospheric Plasma Tetra-Ethyl Ortho Silicate (APTEOS), Chemical Vapor Deposition (CVD), High Density Plasma (HDP) systems and spin-on glass (SOG) materials. The technique employing the application of SOG materials is more economic than the other above equipment-intense techniques.

Other critical concerns in IC substrate processing include regional and global dielectric planarization. The planarization or smoothing of surfaces is essential in the fabrication of integrated circuits. As optical lithography techniques are used to define smaller and smaller features, the depth of focus ofthe exposure tool decreases. Therefore, it is necessary to employ planarizing films to smooth or "level" the topography of microelectronic devices in order to properly pattern the increasingly complex integrated circuits. IC features produced using photolithographic techniques require regional and global dielectric planarization where the lithographic depth of focus is extremely limited,

i.e., at 0.35 μm and below. Without sufficient regional and global planarization, the lack of depth of focus will manifest itself as a limited lithographic processing window. One method for improving the planarization of IC surfaces includes

chemical-mechanical polishing ("CMP"). Thus CMP has a unique

advantage in that it can rapidly remove elevated topographical features

without significantly thinning flat areas. CMP can reduce more of

applied oxide coating thicknesses in raised areas than in recessed areas since the raised areas have a greater surface contact with the polishing

pad and thus can be abraded to a greater extent than recessed areas. By

applying mechanical as well as chemical abrasion to the upper surfaces,

CMP achieves greater planarization than that obtained by conventional etching.

While planarization can be achieved with CMP, its use does not eliminate the need for gap-filling. It has been heretofore believed that the use of

SOG and CMP techniques were mutually exclusive processes. This is

because ofthe common belief that SOG layers are porous and hence the

polish rate of SOG would be much higher than that of other gap-filling

processes.

It would be desirable to provide an improved process for forming

continuously uniform microelectronic substrates whereby the substrate

would be essentially void-free, the metal contacts would be effectively

insulated, and the layers would be effectively planarized. SUMMARY OF THE INVENTION The invention provides a process for forming a void-free, continuous planarized substrate surface comprising:

(a) applying a dielectric composition to a surface of a substrate in an amount sufficient to uniformly coat and fill voids on the surface; and

(b) performing a chemical mechanical polishing step to said dielectric composition until said dielectric composition on said substrate surface is substantially planarized.

The invention also provides a process for treating a semiconductor substrate surface comprising: a) spin depositing a layer of a liquid dielectric composition onto a surface of a semiconductor substrate; b) heating said dielectric layer at a temperature and for a time sufficient to form a continuous, dry dielectric layer on the surface; and c) chemical-mechanical polishing the dielectric layer to remove at least a portion ofthe dielectric layer.

BRIEF DESCRIPTION THE DRAWINGS OF Fig. 1 (a) is an atomic force micrograph (AFM) image of a siloxane

available from AlliedSignal under the tradename Accuglass^® 311 after

thermal cure for 60 min. at 425°C under nitrogen atmosphere, and (b) is the AFM image ofthe SOG Accuglass^® 311 siloxane after being CMP

processed with SC-112 brand fumed silica slurry.

Fig. 2 is a graph of polishing rate (A/min.) of AlliedSignal SOG

Accuglass^® 311 siloxane using slurries of varying pH.

Fig. 3 is a graph ofthe polishing rate (A min.) of substrates coated with

thermal oxide, thermally cured SOG siloxane and vacuum cured SOG

siloxane using SC-112 slurry at various organic ratios.

Fig. 4 (a-d) are graphs ofthe polishing rate (A/min.) of substrates coated

with thermal oxide, PETEOS, PESiHj, Accuglass^® 311 siloxane and

Flare™ fluorinated poly(arylether) available from AlliedSignal Inc. using SC-112 slurry at varying platen rpm.

Fig. 5 is a graph ofthe polishing rate (A/min.) of silicate SOG material

with varying phosphorus content rates using various different slurries.

Fig. 6 is a graphic screen of a Luxtron 2350 end point detector

monitoring variations of motor current to detect the stop point. Figures 7 (a) and (b) show wafer surfaces by scanning electron

microscopy (SEM) micrograph to present the surface condition of wafers before and after CMP.

Fig. 8 shows a substrate having a pattern of metal contacts on which is deposited a CVD layer and an SOG layer, respectively.

Fig. 9 shows a substrate having a pattern of metal contacts on which is

deposited a CVD layer , an SOG layer an additional CVD layer,

respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In its broadest embodiment, the process includes the steps of providing an upper surface of a semiconductor substrate with a dielectric layer. Thereafter, CMP is conducted to remove at least a portion ofthe dielectric layer in an amount sufficient to formed a planarized layer on the

substrate.

Typically the dielectric compositions are applied onto wafer substrates, which are to be processed into an IC or another microelectronic device.

Suitable planar substrates for the present invention non-exclusively

include gallium arsenide (GaAs), silicon and compositions containing silicon such as crystalline silicon, polysilicon, amoφhous silicon, epitaxial

silicon, and silicon dioxide (SiO₂) and mixtures thereof, which may or

may not have a circuit pattern on their surface. Typically, the substrates have a diameter in the range of from about 2 inches to about 12 inches, although the present invention would still be effective for larger or smaller substrates.

One applies a liquid dielectric layer, preferably a spin-on glass (hereinafter SOG) such as a silicate or siloxane in a suitable solvent, to the substrate surface under ambient conditions. Suitable solvents non- exclusively include water and organic solvents in an amount sufficient to

form a uniform solution or dispersion ofthe dielectric material.

A wide variety of commercially available dielectric materials may be used for this puφose. Illustrative of such suitable dielectric materials which

may be spun-on to substrates include, but are not limited to, silicates,

phosphosilicates, siloxanes such as phenylsiloxanes, methylsiloxanes,

methylphenylsiloxanes, phosphosiloxanes, silsesquioxane, methyl

silsesquioxane, methylphenyl silsesquioxane, and organic polymers such as fluorinated polymers, in particular fluorinated poly(arylethers)

available under the tradename Flare™ from AlliedSignal Inc., and copolymers mixtures thereof. Organic dielectrics, i.e. those containing carbon atoms are preferred and siloxanes and fluorinated poly(arylethers) are more preferred. Preferred siloxanes are amoφhous, crosslinked glass-type materials having the formula SiOx wherein x is greater than or equal to one and less than or equal to two, and have, based on the total weight ofthe siloxane materials, from about 2 % to about 90%, and preferably from about 10% to about 25% of organic groups such as alkyl

groups having from about 1 to about 10 carbons, aromatic groups having

from about 4 to about 10 carbons, aliphatic groups having from about 4

to about 10 carbons, and mixtures thereof. Optionally, the siloxane and silicate materials may also contain phosphorus in an amount from about 0% to about 10%, and preferably from about 2 % to about 4% based on the total mol percent ofthe dielectric materials. Preferred siloxane

materials suitable for use in this invention are commercially available

from AlliedSignal Inc. under the tradename Accuglass^®.

Suitable siloxane materials contain about 100 parts per billion or less,

preferably 50 parts per billion or less, and more preferably 10 parts per billion or less of trace element impurities such as sodium, potassium, chlorine, nickel, magnesium, chromium, copper, manganese, iron, calcium, and the like, and preferably have a molecular weight of from about 1,000 to about 50,000, and more preferably from about 300 to

about 1,000 molecular weight units.

In the preferred embodiment, the dielectric materials have a viscosity when applied ranging from about .8 to about 70 cP, a percent solids when applied ranging from, based on the total weight ofthe dielectric

material, solvent and water, about 3% to about 36% and a water content

of from about 0 to about 11%, a dielectric constant of about 10 or less,

preferably from about 2.4 to about 3.2, and a refractive index of from

about 1.37 to about 1.65.

The dielectric material may be applied to the substrates via conventional

spin-coating, dip coating, spraying, or meniscus coating methods which

are well-known in the art. Details of such methods are described in, for

example, "Processing Equipment and Automated Systems", a brochure by Integrated Technologies. Spin-coating is most prefeπed. The

thickness ofthe dielectric film on the substrate may vary depending on the amount of liquid dielectric that is applied to the substrate, but

typically the thickness may range from about 500 A to about 2 microns,

and preferably from about 3000 A to about 9000 A. The amount of

dielectric liquid applied to the substrate may vary from about 1 ml to

about 10 ml, and preferably from about 2 ml to about 8 ml. In the preferred embodiment, the liquid material is spun onto the upper surface the substrate according to known spin techniques. Preferably, the dielectric is applied from a solution which is centrally applied to the substrate and then spun on a rotating wheel at speeds ranging between about 500 and about 6000 rpm, preferably between about 1500 and

about 4000 φm, for about 5 to about 60 seconds, preferably about 10 to

about 30 seconds, in order to spread the solution evenly across the substrate surface. Once placed, the liquid dielectric composition fills valleys or crevices both in the substrate and between densely spaced metal conductors on the substrate to provide a smoothing effect which does present some planarization in the crevices, however, not enough to fiilly planarize that area.

After the dielectric material is applied to the substrate, the dielectric- substrate combination is optionally, but preferably heated for a time and at a temperature sufficient to evaporate any residual solvent present within the dielectric film, to further reduce the viscosity ofthe film, and to enhance leveling ofthe film on the substrate, and to increase or decrease the density, chemical resistance properties and/or physical abrasion resistance properties ofthe film, as may be determined by one skilled in the art without undue experimentation. A change in the density and chemical properties ofthe dielectric affords a change in its

susceptibility to CMP removal. An increase in temperature or exposure time to heat will incrementally change the chemical and mechanical properties ofthe dielectric layer thereby bringing about a change in CMP removal rate. Removal can be fixed at a higher or lower rate according to the properties ofthe dielectric layer material and the particular CMP chemical slurry and mechanical pressure conditions being applied.

Generally, the dielectric coated substrate is heated at a temperature of

from about 50 °C to about 400 °C , more preferably from about 50 °C

to about 250 °C for about .5 to about 10 minutes, more preferably from about 1 to about 3 minutes. This is preferably done on a hot plate but may also be done in an oven. In a prefeπed embodiment, the dielectric is

first heated at about 50 °C for about 30 seconds to one minute, then

heated at about 150 °C for about 30 seconds to one minute, and heated a

third time at about 250 °C for about 30 seconds to one minute. The

liquid dielectric material partially crosslinks and solidifies as a result of such heating.

After the coating is heated, the thickness ofthe resulting film ranges from about 0.2 to about 3.0 micrometers, preferably from about 0.5 to about 2.5 micrometers, and most preferably from about 0.7 to about 2.0 micrometers. The films produced by this invention generally exhibit a

thickness standard deviation less than 2%, and preferably less than 1%, of the average film thickness.

Prior to CMP, the dielectric layer may optionally receive a curing cycle defined at a level and duration necessary to density and change the chemical composition of the dielectric layer. In the preferred curing

embodiment, the dielectric layer is heated to cause an incremental mechanical hardening and chemical change in the dielectric composition

under temperatures of from about 250 °C to about 1,000 °C for a period

of from about 5 minutes to about 240 minutes, more preferably from

about 300 °C to about 800 °C for from about 30 minutes to about 120

minutes, and most preferably from about 350 °C to about 450 °C for from about 30 minutes to about 120 minutes to further cure the layer.

In an alternate curing embodiment, the dielectric layer may be exposed to electron beam radiation under conditions sufficient to cure the dielectric material prior to removal ofthe dielectric layer. The dielectric coated substrate is cured by exposing the surface ofthe substrate to a flux of electrons while in the presence of a gas selected from the group consisting of oxygen, argon, nitrogen, helium and mixtures thereof, and preferably oxygen, argon, nitrogen, and mixtures thereof. Nitrogen gas is

more preferred. The temperature at which the electron beam exposure is conducted will depend on the desired characteristics ofthe resulting film

and the length of desired processing time. One of ordinary skill in the art

can readily optimize the conditions of exposure to get the claimed results

but the temperature will generally be in the range of about 25 °C to about

250 °C, and preferably from about 150 °C to about 250 °C. The

pressure during electron beam curing will range between from about 10

mtorr to about 200 mtorr, and preferably from about 10 mtorr to about

40 mtorr. The period of electron beam exposure will be dependent upon

the strength ofthe beam dosage applied to the substrate. One of

ordinary skill in the art can readily optimize the conditions of exposure to

get the claimed results, but generally the exposure will range from about 5 to about 45 minutes, and preferably from about 7 to about 15 minutes with application of an electron beam dose of about 2000 to about 50,000, preferably from about 7500 to about 10,000 microcoulombs per square

cm. The accelerating voltage ofthe electron beam may range from about

5 to about 15 KeV. The dose and energy selected will be proportional to

the thickness ofthe films to be processed. The dielectric coated substrate may be exposed to electron beams in any chamber having a means for

providing electron beam radiation to substrates placed therein. Typically,

the chamber is also equipped with a means for emitting electrons into a

gaseous atmosphere comprising oxygen, argon, nitrogen, helium and

mixtures thereof, and preferably oxygen, argon, and nitrogen, simultaneously with electron beam exposure. In a prefeπed embodiment, the dielectric coated substrate is placed into a chamber which is commercially available from Electron Vision, San Diego, California,

under the tradename "ElectronCure"™, the principles of operation and

performance characteristics of which are described in U.S. Patent Number 5,001,178, which is incoφorated herein by reference.

After the dielectric layer is optionally cured, one performs a CMP to the

dielectric layer according to known techniques. Details of such

techniques are well known in the art, see for example, U.S. patent 5,516,729 which is incoφorated herein by reference. In general, the chemical-mechanical polish step is conducted by abrading the dielectric layer with an abrasive powder slurry comprised of an alkali silica, a umed silica or cerium oxide, using a polishing pad such as a foamed fluorocarbon polishing pad employing a pressure of from about 5 to about 20 lbs/in², preferably from about 5 to about 10 lbs/in². The preferred slurry is cerium oxide having a crystallite size of from about 14 to about 100 nm, and preferably from about 14 to about 20 nm. Preferably the slurry composition has a pH range of from about 2.8 to about 11, or more preferably from about 10.3 to about 11. Particularly useful slurry materials nonexclusively include SCI 12, which is a fumed

silica available commercially from Cabot Coφoration of Aurora, Illinois and has a pH of 10.3; ILD 1300 which is a fumed silica available commercially from Rodel Coφoration of Scottsdale, Arizona and has a pH of 11.0 and SS25 which is a fumed silica available commercially from

Cabot Coφoration and has a pH of 10.8. Preferably CMP is done with a

commercially available polisher such as a Avanti 372 or 472 from

IPEC/Westech, having a platen speed of from about 10 to about 100

φm, preferably from about 25 to about 60 φm and a downward pressure

from a polishing pad to the dielectric surface of from about 5 to about 20

psi, preferably from about 7 to about 11 psi. CMP may be conducted for

from about .5 to about 60 minutes, preferably from about .5 to about 30 minutes and more preferably from about .5 to about 60 minutes. The

amount of dielectric layer typically removed depends on the dielectric

layer thickness applied.

The dielectric layer is partially removed such that after such portions are removed, the remaining layer is more planar than prior to CMP. The following non-limiting examples serve to illustrate the invention.

EXAMPLE 1: Preparation of SOG coated wafers

Six inch diameter silicon wafers are coated with a siloxane SOG, namely

Accuglass^®311 available from AlliedSignal Inc., by dispensing 3 to 4 ml

of the SOG onto the surface of the wafers. The wafers are then spun on

a SOG coater track, manufactured by DNS Inc., for 2 seconds at 72°F at

about 350 φm. After the coated wafers are additionally spun at 3000

φm for about 20 seconds under similar conditions, they are then heated on hot plates in the coater track for three consecutive intervals of 120 seconds at 80°C, 120°C and 175°C.

The coated wafers from step 1 are then cured in a furnace, manufactured by MRL Industries for 1 hour at 425°C and 1 atmosphere in the presence of nitrogen to produce a cured dielectric layer.

EXAMPLE 2: Thickness of Polished wafers

The wafers produced in Example 1 are then polished with an Avanti 472

polisher manufactured by IPEC/Westech, with slurries that have pH's ranging from 10.3 pH to 11 pH. Polishing is conducted at a down

pressure of 7.0 psi, plate speed of 28 φm, oscillating at a 5 mm range at

speed of 2 mm/minute. Polishing is done at 110 °F using an IC 1000

polishing pad available from Rodel Coφoration. The slurry flows at 130

ml/minute. Wafer thicknesses are pre-measured before CMP using a

Prometrix instrument manufactured by Tencor at twenty five different

locations on the wafers and then the twenty five values are averaged.

Polished SOG coated wafers are then post-measured after CMP for thickness at twenty five different locations on the wafers, then the twenty

five values are averaged. The polish rate is obtained by subtracting post- measurement thickness from pre-measurement thickness. Automated calculation is done by the Prometrix instrument. Fig. 1 (a) shows an

atomic force micrograph (AFM) image of SOG Accuglass^® 311 after

thermal cure for 60 min. at 425°C under a nitrogen atmosphere, and (b)

is the AFM image of SOG Accuglass^® 311 after CMP processed with

SC-112 slurry. Fig. 2 shows a graph of polishing rate (A/min.) of SOG

Accuglass^® 311, range from 0 to 2000 A/min. with slurries that have

different pH rates from a 10.3 pH to 11 pH. EXAMPLE 3: Preparation of wafers with different organic ratios

A thermal oxide film is grown on a bare Si wafer in a fumace to produce a thermal oxide wafer which is then thermally cured according to the procedure set forth in Example 1. An additional layer ofthe SOG used in Example 1 is applied thereon according to the procedure of Example

1, then the wafer is cured in a vacuum furnace, manufactured by DNS, to

produce vacuum cured SOG wafer. Figure 3 shows the polishing rate of

different dielectric surfaces as a function of percent organic content of the SOG. This example shows the polish rate of thermal oxide film, thermally cured SOG and vacuum cured SOG as a function of organic content in the SOG.

EXAMPLE 4: Preparation of wafers using different SOG materials Example 1 is repeated, but with different dielectric SOG materials,

namely, a thermal oxide, PETEOS, PESiHt , Accuglass^® 311 silane and FLARE™ fluorinated poly(arylether). This example exemplifies CMP polish rates, as shown in Figures 4 (a-d), as a function of polishing down pressure and platen φm for a variety of SOG materials.

EXAMPLE 5: Preparation of wafers with different phosphorus contents Example 1 is repeated with different SOG materials having different phosphorous wt.%, which are available from AlliedSignal Inc. under the tradename Accuglass^® 203 AS, Pl 12A and Pl 14A. The coated wafers are

then polished with an Avanti 472 polisher, using SC-112, SS-25 and

ILD- 1300 slurries. Wafer thickness is pre-measured and post measured

as set forth in Example 2. The polishing rate as a function of phosphorus

content is shown in Fig.5. This example shows the use of SOG materials having various phosphorus contents.

EXAMPLE 6: End Point Detection bv

Preparation of CVD TEOS/SOG coated wafer

The CMP may be conducted through the dielectric layer until an underlying layer is reached. This underlying layer is usually a substrate with metal conductors and an oxide layer. A stopping or end-point is reached when a portion ofthe desired underlying layer is reached by the

CMP.

A layer of TEOS film having a thickness of 2kA is applied onto

polysilicon wafers via CVD at a temperature of about 350°C to 400°C and a pressure at 10 mtorr. The wafers are then similarly deposited with

another layer of TEOS film at a thickness of 8 kA, after the wafer was

processed by the method of Example 1.

The prepared wafer is polished and monitored by a Luxtron 2350 End¬

point detection system to observe constant rotational velocity ofthe wafer polishing head in order to maintain constant a polishing rate. Results are shown in Fig.6.

EXAMPLE 7: Endpoint Detection of PESJH4 Coated Wafers Example 6 is repeated but with a different layer of CVD film, PESiH,, to produce test wafers. Then the wafers are polished and monitored by a Luxtron 2350 End-point detection system to observe constant rotational velocity ofthe wafer polishing head in order to maintain constant polishing rate.

EXAMPLE 8 SEM shows local and global planarization by the SOG/CMP combined process when Examples 1 and 2 are repeated on a bare unpattemed Si wafer. Figures 7 (a) and (b) show the surface ofthe wafers both before and after CMP.

EXAMPLE 9

Example 1 and 2 are repeated except the slurry used for CMP is cerium oxide at a variety of weight percentages in deionized water, pH's and

particle sizes, and the dielectric layer is comprised of Accuglass^® 311

siloxane, Accuglass^® 418 methylsilsesquioxane, Flare™ fluorinated

poly(arylether) and TEOS Polishing rates are measured as set forth in Example 2 and results of which are presented in Table 1 TABLE 1

Slurry Polish Rate (^<$/ min.)

Cell^' % CeO pH Particle Accuglass^® Accuglass^® Flare TEOS Size 311 418

Cell 1 10% (+) 7.0 (+) 350 nm (+) 2484 9900 4000 6000

Cell 2 10% (+) 2.8 (-) 20 nm (-) 2833 165 1034 740

Cell 3 10% (+) 7.0 (+) 170 nm (-) 2490 3719 5000 2120

Cell 4 10% (+) 2.8 (-) 350 nm (+) 519 4263 4655 1135

Cell 5 3% (-) 2.8 (-) 20 nm (-) 1092 1053 1295 1321

Cell 6 3% (-) 7.0 (+) 170 nm (-) 5328 10278 1650 5124

Cell 7 3% (-) 7.0 (+) 350 nm (+) 5060 2171 4380 2432

Cell 8 3% (-) 2.8 (-) 350 nm (+) 248 8172 2432 1434

cell refers to the cell ofthe Prometrix measurement instrument.

One ofthe most important uses for the SOG/CMP process is endpoint control, i.e. operator control ofthe point at which CMP is ended when the polishing through the dielectric layer reaches an underlying layer.

The underlying layer is typically the substrate with metal conductors and an oxide layer. A stopping or end-point is reached when a portion ofthe underlying layer is reached by the polish operation. The use ofthe SOG layer as a stop layer in the planarization process is shown in Fig. 8 and Fig. 9, which illustrate a silicon substrate 1 having a pattem of metal contacts 2 thereon, onto which is deposited a CVD layer 3 of PETEOS or PESiH, , followed by a SOG layer 4. Fig. 9 shows an additional CVD exterior layer 5 of PETEOS or PESiH,. The CMP step may be conducted wherein polishing can stop in SOG layer 4, CVD layer 5 or CVD layer 3, depending on the end use.

It will be appreciated to those skilled in the art having the benefit of

this disclosure that this invention is capable of applications with multiple

levels of interconnect and can be repeated to form interlevel dielectrics between each level of interconnect. Furthermore, it is also to be understood that the form ofthe invention shown and described is to be taken as exemplary, presently preferred embodiments. Various modifications and changes may be made without departing from the spirit and scope ofthe invention as set forth in the claims. It is intended that the following claims be inteφreted to embrace all such variations and modifications.

Claims

What is claimed is:

1. A process for forming a void-free, continuous planarized substrate surface

comprising:

(b) performing a chemical mechanical polishing step to said dielectric composition until said dielectric composition on said substrate surface is substantially

planarized.

2. The process of claim 1 further comprising heating the dielectric composition and substrate at a temperature and for a time sufficient to form a continuous, dry

dielectric film on the surface after step (a) but before step (b).

3. The process of claim 1 wherein the dielectric composition comprises a material

selected from the group consisting of silicates, phosphosilicates, siloxanes,

silsesquioxane, organic polymers, copolymers and mixtures thereof.

4. The process of claim 1 wherein said dielectric composition comprises a siloxane having, based upon the total weight of said siloxane, of from about 2% to

about 90% of organic groups comprising alkyl groups having from about 1 to

about 10 carbons, aromatic groups having from about 4 to about 10 carbons,

aliphatic groups having from about 4 to about 10 carbons, or mixtures thereof.

5. The process of claim 2 wherein said dielectric composition is further cured by an additional subsequent heating before step (b) at a temperature of from about 25 °C to about 250 °C.

6. The process of claim 2 wherein said dielectric composition is further cured by an electron beam curing treatment.

7. The process of claim 1 wherein the chemical mechamcal polishing is conducted with an alkali silica slurry.

8. The process of claim 1 wherein the surface comprises a pattem of metallic electrical conductors and a layer of an oxide on the metal contacts.

9. The process of claim 1 wherein the surface comprises a pattem of metallic electrical conductors and a layer of an oxide on the metal contacts and the process further comprises depositing a second oxide layer on the dielectric layer before conducting step (b).

10. A substrate produced according to the process of claim 1.

l l. A microelectronic device comprising the substrate of claim 21.

12. A process for treating a semiconductor substrate surface comprising a) spin depositing a layer of a liquid dielectric composition onto a surface of a semiconductor substrate; b) heating said dielectric layer at a temperature and for a time sufficient to form a continuous, dry dielectric layer on the surface; and c) chemical-mechanical polishing the dielectric layer to remove at least a portion ofthe dielectric layer.