JPS62235738A - Formation of insulating film on semiconductor sub-strate - Google Patents

Abstract

PURPOSE:To form a flat insulating film with high reliability very easily by a method wherein a semiconductor substrate is coated with a coating agent mixed with a hydrolyzed product of a specified organosilane compound and a specified silane compound, water and a hydrophilic organic solvent to be hardened by heat-treatment and then a resist mask formed on a hardened film is removed after etching process. CONSTITUTION:A semiconductor substrate 1 with lower layer interconnections 2 formed thereon is spin-coated with a coating agent mixed with 25 weight % of methyltrimethoxysilane, 24.9 weight % of isopropylalcohol, 50 weight % of colloidal silica and 0.01 weight % of fine particle alumina at an r.p.m. attaining to specified film thickness to be hardened by heat-treatment in the air. Next, after forming a resist film on a hardened film 3, the hardened film 3 is etched by RIE process using C2F6 gas as well as a resit pattern 4 formed by photolithography as a mask to form a connecting hole 7 between upper and lower interconnections. Finally, the resist pattern 4 is removed by plasma etching process and then an upper layer interconnection 5 is formed by evaporating a metallic layer as the upper layer interconnection 5 on overall surface to be dryetched.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 2 B] The present invention relates to a method for forming an insulating film used in semiconductor integrated circuits and the like. Specifically, the present invention relates to a method of forming an interlayer insulating film, a protective film, a planarization film, etc. used in a multilayer wiring structure.

Prior Art The prior art will be explained using FIG. 4, taking a multilayer wiring structure as an example. Lower layer wiring 2 is formed on semiconductor substrate 1 on which predetermined elements are formed. A SiO2 film 6, which is intended to be an insulating film between the eyebrows, is formed on the lower layer wiring 2 using a vapor phase growth method such as a CVD method (fourth diagram). A resist 4 is formed on the 5102 film 6 using a normal photolithography process (FIG. 4(B)),
Using this as a mask, the 5i02 film 6 is dry etched to form upper and lower wiring connection holes. Finally, a wiring metal layer such as A1 is deposited and dry etched to form a multilayer wiring structure as the upper layer wiring 6 (FIG. 4q).

In the conventional method described above, since an insulating film formed by a vapor phase growth method is used as an interlayer insulating film, the upper layer wiring 6 may be disconnected due to the residual level difference in the underlying layer as shown in FIG. 3 There are problems with page connections, etc.

To solve these problems, organic polymer resins and spin-on glass (product name: Merck & Co., Ltd.), which are excellent at flattening substrate steps, have been proposed, but organic polymer resins are less effective than inorganic insulating films. It has the disadvantage of poor heat resistance and moisture resistance,
Spin-on glass has the disadvantage that cracks occur when the film thickness is 3 μm or more. For this reason, forming methods such as etch-back are used to form the interlayer insulating film, but there are problems in that the steps are complicated and damage to the elements occurs.

Problems to be Solved by the Invention As described above, insulating films formed by vapor phase growth methods may cause residual step differences in the base layer, disconnections in upper layer interconnects in multilayer interconnect structures due to poor coverage, short circuits between upper and lower interconnects, etc. There are problems such as reduced reliability, and complicated processes. Further, organic polymer resins are excellent in flattening the substrate because they can form an insulating film by spin coating, but they have a problem in that they are inferior in heat resistance and moisture resistance compared to inorganic insulating films.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a structure in which a general formula RSi (OR
') 3 (in the formula, R is an organic group having 1-8 carbon atoms, and R' is an alkyl group having 1-5 carbon atoms or an acyl group having 1-4 carbon atoms). A hydrolyzate of colloidal silica and/or a silane compound represented by 5t(OR')4 (wherein R' is the same as above) or a polycondensate thereof, water, and a hydrophilic organic solvent are mixed. a step of applying a coating agent of A method for forming an insulating film on a semiconductor substrate is proposed.

Function Since the coating agent used in the present invention is of a liquid type, it can be formed by a method that does not use a vacuum system, such as spin coating. In addition, its concentration is higher than that of conventional spin/5 page on glass, and its viscosity is lower than that of organic polymer resins such as polyimide resin, so it is superior in flattening compared to conventional materials. Furthermore, it is possible to form a thick film of 1 μm or more, and after curing, it becomes an insulating film with excellent heat resistance and moisture resistance.

Further, the coating agent used in the present invention can be cured at a low temperature of 80° C. to 300° C. in N2Φ or air, and can be cured in a short processing time of several tens of minutes. Therefore, it is also effective in preventing stress migration of the wiring metal layer. In addition, since the same method as for the 5102 film is used in the etching process, conventional equipment can be used, and the etching process becomes easy for insulating films used in a multilayer structure with the Sio2 film, such as the niche back method.

EXAMPLE First, the composition of the coating material used in the present invention will be explained.

Specific examples of the coating agent used in the present invention include coating agents obtained by mixing the following components (-) to (d).

6 Page (-) General formula R81(OR')3 (wherein, R is an organic group having 1 to 8 carbon atoms, and R' is an alkyl group having 1 to 5 carbon atoms or an acyl group having 1 to 4 carbon atoms. 5 to 60 parts by weight of an organosilane compound represented by (b) colloidal silica and/or S i (OR')4 (in the formula,
(R' is the same as above) 3 to 40 parts by weight of a hydrolyzate obtained by hydrolyzing a 7-run compound or its polycondensate in terms of solid content; (C) 3 to 60 parts by weight of water; , and (d) 10 to 80 parts by weight of a hydrophilic organic solvent (including water that may be present in the component (C), and (a) + (b) + (c) + (d) -1
00 parts by weight).

The components (a) to (d) will be explained below.

(-) R in the organosilane compound is an organic group having 1 to 8 carbon atoms, such as an alkyl group such as a methyl group, an ethyl group, an n-propyl group, a l-propyl group, or an r-chloropropyl group. , vinyl group, 3.3.3-) lifluoroprovir group, r-glycidoxypropyl group, r-methacryloxyglobin 7Bage/14, r-mercaptopropyl group, phenyl/L4.3
．． These include 4-epoxycyclohexylethyl group and r-aminopropyl group.

Furthermore, R' in the organosilane compound has 1 to 6 carbon atoms.
an alkyl group or an acyl group having 1 to 4 carbon atoms, such as a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 5ea-butyl group, tert-butyl group, acetyl group, etc. be.

Specific examples of these organosilane compounds include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, and l-propyltriethoxysilane. Methoxysilane, i-propyltriethoxysilane, r-chloropropyltrimethoxysilane, r-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3 , 3.3-trifluoropropyltriethoxysilane, r-glycidoxypropyltrimethoxysilane, r-glycidoxypropyltrimethoxysilane,
r-methacryloxypropyltrimethoxysilane, r
-methacryloxypropyltriethoxysilane, r-
Mercaptopropyltrimethoxysilane, r-mercaptopropyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, r-aminopropyltrimethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, 3,4-epoxycyclohexylethyl Examples include triethoxysilane.

These organosilane compounds can be used alone or in combination of two or more.

Furthermore, among these organosilane compounds, methyltrimethoxysilane is particularly preferred.

The proportion of such an organosilane compound in the coating agent is 5 to 60 parts by weight, preferably 20 to 35 parts by weight; if it is less than 5 parts by weight, the storage stability of the resulting coating agent itself is good, but there is a problem with page printing. When subjected to
In addition, the hardness is not sufficiently improved, and if the amount exceeds 60 parts by weight, the storage stability of the composition (2) deteriorates and the coating film tends to crack.

Next, what is the colloidal silica used in component (b)?
It is an aqueous dispersion or a hydrophilic organic solvent dispersion of high-purity silicic anhydride, and usually has an average particle size of 6 to 30 mμ, preferably 10 to 20 mμ, and a solid content concentration of 15 to 405 to 4.
0 parts by weight of colloidal silica, in the case of an aqueous dispersion, is usually
Acidic region, preferably pH 2-6, particularly preferably 2
~6.

Examples of colloidal silica in such an aqueous dispersion include Snowtex, manufactured by Nichichi Kagaku Kogyo ■; Cataloid, manufactured by Catalysts and Chemicals; Ludox, manufactured by DuPont, USA;
Examples include Syton, manufactured by Monsanto Company, USA; Nalcoag, manufactured by Nalco Chemical Company, USA.

In addition, as colloidal silica using alcohol, which is a hydrophilic organic solvent, as a dispersion medium, alcohol sol manufactured by Nissan Kagaku Kogyo 10 Page Industry ■;
Examples include L.

Those that can still be used as the other component (b) are:
A hydrolyzate obtained by hydrolyzing a silane compound represented by S i (OR' )4 (wherein R' is the same as above) or a polycondensate thereof (hereinafter simply referred to as "hydrolyzate") ).

Here, examples of the silane compound include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-1-propoxysilane, tetra-n-butoxysilane, tetra-ttea-butoxysilane, and tetra-tart- Examples include butoxysilane.

These silane compounds can be used alone or
Or two or more types can also be used together.

In the coating agent used in the present invention, in order to achieve further thickening, high purity, and low-temperature sintering of the resulting coating film, it is necessary to use a hydrolyzate as the component (b). preferable. When a hydrolyzate is used as component (b), it is used as a dispersion having a solid content concentration of 11 and a Behn degree of 3 to 40 by weight.

The ratio of component (b) as described above in the coating agent is
The solid content is 3 to 40 parts by weight, and the solid content is 5 to 30 parts by weight, and if it is less than 3 parts by weight, the hardness of the resulting coating film will decrease,
It is difficult to achieve a thick film, while if the amount exceeds 40 parts by weight, a thick film is easily obtained, but cracks are likely to occur in the coating film.

Next, (C) water is an essential component for the hydrolysis of the organosilane compound (a), and also serves as a dispersion medium for the component Φ).

Such water includes component (b) (and (e) described later).
When water is present in the alumina, distilled water, ion-exchanged water, etc. can be used in addition to the water.

The proportion of water in the coating agent is 3 to 60 parts by weight, preferably 5 to 50 parts by weight; if it is less than 3 parts by weight, sufficient hydrolysis of the organosilane compound will not occur; If it exceeds this value, the stability of the coating agent will deteriorate.

Next, as the hydrophilic organic solvent (d), for example, alcohols, glycol derivatives, or low boiling point organic solvents having a boiling point of 120° C. or less are suitable.

Among these, examples of the alcohols or glycol derivatives include ethylene glycol, which is a monohydric alcohol or dihydric alcohol, or derivatives thereof. Among these, the monohydric alcohol is preferably an aliphatic alcohol having 1 to 8 carbon atoms. , specifically methanol,
Ethanol, n-propyl alcohol, i-propyl alcohol, 5ec-butyl alcohol, tert-butyl alcohol, n-pentyl alcohol, n-hexyl alcohol, etc. can be mentioned, and examples of ethylene glycol or its derivatives include ethylene glycol, ethylene Examples include glycol monobutyl ether and acetic acid ethylene glycol monoethyl ether.

In addition, as a low boiling point organic solvent with a boiling point of 120°C or less,
Examples include acetone, methyl ethyl ketone, and tetrahydrofuran.

Among these hydrophilic organic solvents, particularly preferred are inpropyl alcohol and ethylene glycol monoethyl alcohol acetate.

These hydrophilic organic solvents can be used alone or in combination of two or more.

The proportion of the hydrophilic organic solvent (d) in the coating agent is 10 to 80 parts by weight, preferably 20 to 60 parts by weight, and if it is less than 10 parts by weight, the weight of the organotrisilanol produced by hydrolysis of the organosilane compound is If the condensation progresses too much, gelation will occur, while if it exceeds 80 parts by weight, the polycondensation reactivity will decrease.

The coating agent used in the present invention is as described above (
The solid content in the coating agent is usually 6 to 45 parts by weight, preferably 8 to 3 parts by weight.
It is 0 parts by weight.

In addition, the coating agent used in the present invention has a pH of
It is desirable to adjust the pH to 3 to 6, and such pH adjustment is usually carried out with the above-mentioned component (C) and/or (4i
1) This can be achieved by using the alumina component, but in some cases it is also possible to adjust the pH by separately adding various acids to the Co-14 venting agent. Such acids include inorganic acids such as nitric acid and hydrochloric acid; acetic acid, formic acid, propionic acid, maleic acid, chloroacetic acid, citric acid, benzoic acid, dimethylmalonic acid, glutaric acid, glycolic acid, malonic acid, toluenesulfonic acid, and sulfuric acid. Mention may be made of sodium chloride organic acids.

The coating agent further contains, as component (8), 0.005 to 0.6 parts by weight of alumina fine particles, such as colloidal alumina, ultrafine alumina particles with an average particle size of 10 to 100 mμ, etc. in terms of solid content. , preferably 0.0
It may be added in an amount of 0.7 to 0.03 parts by weight.

Such alumina has a strong tendency to become positively charged and can form stable colloids with negatively charged solids in coatings.

Among the components (e), colloidal alumina is usually commercially available as an acidic alumina sol using water as a dispersion medium, and contains 6 to 26% by weight of aluminum oxide (A1203), and nitric acid and hydrochloric acid as stabilizers. , 15 benoacetic acid, the particle diameter is about 10 mμ x 100 mμ, and the specific surface area of the particles is 200 to 6 oOn per 1f. That's about it.

Such colloidal alumina has a pH of 2 to 6, particularly 3, in order to cure the coating film well after applying the coating agent.
It is preferable that it is in the range of ~6.

However, the average particle size used as the other component (e) is 10 to 100 mμ, preferably more than 20 mμ to 50 mμ.
Ultrafine alumina particles of micron or less can be produced by a known production method, for example, by high-temperature hydrolysis of anhydrous aluminum chloride, or by aluminum trialkoxide;
7 (OR')3 (R' is the same as above, for example, aluminum trimethoxide, aluminum triethoxide, aluminum tripropoxide, aluminum triptoxide, etc.), and is usually obtained by hydrolyzing ,
The aluminum oxide component is 99% by weight or more.

Examples of such ultrafine particle alumina include Aluminum Oxide C manufactured by Degussa of West Germany.

Further, when ultrafine alumina particles are used as component (e), it is preferably in an acidic region, particularly preferably in a p-
Acidic aqueous dispersion of H2-6 with a solid content concentration of 10-20
Used as a weight handler.

These alumina fine particles can also be used in combination.

The proportion of component (e) as described above in the coating agent is
The solid content is preferably 0.005 to 0.3 parts by weight, particularly preferably 0.007 to 0.03 parts by weight, and 0.0
If the amount is less than 0.5 parts by weight, the improvement in storage stability of the coating agent will be small, and if it exceeds 0.3 parts by weight, the transparency of the coating film will deteriorate.

Other conventionally known additives such as various pigments, dyes, surfactants, cassoplating agents, hardening agents, etc. can also be added to the coating agent.

When preparing the coating agent used in the present invention, for example, (a) to (d) may be mixed at once;
Further, (a) may be added to the mixed solution of (b) to (d).

As described above, since the coating agent 17 used in the present invention is a liquid type, it can be formed by a method that does not use a vacuum system, such as spin coating. In addition, its concentration is higher than that of conventional spin-on glass, and its viscosity is lower than that of organic polymer resins such as polyimide resin, so it is superior in flattening compared to conventional materials. Furthermore, it is possible to form a thick film of 1 μm or more, and after curing, it becomes an insulating film with excellent heat resistance and moisture resistance.

Furthermore, the coating agent used in the present invention can be cured in N2 or air at a low temperature of 80 DEG C. to 300 DEG C., and can be cured in a short processing time of several tens of minutes. Therefore, it is also effective in preventing stress migration in the wiring metal layer. In addition, since the same method as for the Si02 film is used in the etching process, conventional equipment can be used, and the etching process becomes easier with an insulating film used in a multilayer structure with the 5102 film, such as an etch-back method.

(Example 1) A multilayer wiring structure using the present invention will be described with reference to FIG.

1 is a semiconductor substrate on which a semiconductor integrated circuit element is fabricated. On the semiconductor substrate 1 on which the lower layer wiring 2 such as A7 is formed, 2 BMik parts of methyltrimethoxysilane, 24.9974 parts of Inglobil alcohol, and colloidal silica (Snowtex o;
H=2.5, silicic anhydride content -20 to 21 by weight, average particle size of silicic anhydride -10 to 20 mμ, water used as a dispersion medium) Part by weight of SO and particulate alumina (aluminum oxide manufactured by Tegusa, West Germany) C9 average particle size 6-30mμ
) A coating agent obtained by mixing 0.01 parts by weight is applied using a spinner at a rotation speed to achieve the desired film thickness, and heated at 8°C x 3 in air or nitrogen, preferably under reduced pressure.
Heat treatment is performed for 0 minutes + 160°C for 30 minutes to harden the film. A resist film is formed on the cured film 3, and a resist pattern 4 is formed using a normal photorin process (FIG. 1A). Using the resist pattern 4 as a mask, the cured film 3 is etched by RIE using 02F6 gas to form connection holes (through poles) 7 between the upper and lower wirings (FIG. 1B). Resist pattern 44, plasma etching or fuming nitric acid, etc. 1
After removal on page 9, a metal layer that will become the upper layer wiring is deposited on the entire surface and dry etched using a resist pattern to form the upper layer wiring 5 (FIG. 1C).

The cured film of the coating agent used in the present invention has excellent chemical resistance and does not become rough due to O2 plasma etching or fuming nitric acid, which are disadvantages of organic insulating film materials.

In addition, since the thermal loss starting temperature is as high as 800"C, it is stable even during heat treatment for A7 sintering, and no cranking occurs.The surface of the substrate after the film 3 has been formed has unevenness and is excellent in flattening. There will be no disconnection of the upper layer wiring 6 or short circuit between the upper and lower wirings due to poor coverage.The above method is not limited to two-layer wiring, but can also be applied to multilayer wiring of three or more layers.

(Example 2) An etch-back method using the present invention will be explained using FIG. 2.

A coating agent similar to that in Example 1 is applied onto the semiconductor film 2 on which predetermined elements and lower wiring 2 have been formed, and is hardened by heat treatment to flatten the surface (FIG. 2B). SiO
The two-layer insulating film 6 and the cured film 3 are etched using isotropic etching until a desired thickness is achieved, and the surface is flattened (FIG. 2C).

In the conventional method, an organic polymer film such as a resist film is used as a flattening film on an insulating film.
In the process of etching the iO2 film and the resist film at the same rate, there were problems in confirming the etching end point and setting etching conditions, but the method using the present invention
Since etching can be performed using only the etching conditions for the O2 film, the process is simple and reproducibility is improved.

A similar application is to fill in defective areas of SiO2°C force coverage by forming a film on a fine pattern using a vapor phase growth method. S is applied on the fine pattern using CVD method etc.
When the 102 film is formed, a space 1o is created in the recess as shown in FIG. Therefore, during cleaning or wet etching, the solution tends to remain in the space, causing defects. Then, using the present invention, an insulating film is formed on the 21-page insulating film formed by vapor phase growth to fill the space in the recess 1o. Since the coating agent used in the present invention is a liquid type, it is formed thicker on the recesses and thinner on the protrusions, and can fill the four spaces with almost no change in the film thickness on the protrusions.

Effects of the Invention As described above, since the coating agent used in the present invention is a liquid type, it can be formed by a method that does not use a vacuum system, such as spin coating. Also, its concentration is lower than that of conventional spin-on.
It has a higher concentration than glass and a lower viscosity than organic polymer resins such as polyimide resin, so it is better at flattening than conventional materials. Furthermore, it is possible to form a thick film of 1 μm or more, and after curing, it becomes an insulating film with excellent heat resistance and moisture resistance.

Further, the coating agent used in the present invention can be cured in N2 or air at a low temperature of 80 DEG C. to 300 DEG C., and can be cured in a short processing time of several tens of minutes. Therefore, it is also effective in preventing stress migration in the wiring metal layer. In addition, since the same method as for the 8102 film is used in the etching process, the conventional equipment on page 22 can be used, and the etching process becomes easier for insulating films used in a multilayer structure with the 8102 film, such as by the etch-back method.

As described above, according to the present invention, a flat and highly reliable insulating film can be formed by a simple method, which greatly contributes to the production of high-density semiconductor devices.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of the process steps of an embodiment of the present invention, FIG. 3 is a cross-sectional view of a semiconductor substrate after vapor phase growth S 102 is formed, and FIG. 4 is a method of forming multilayer wiring using a conventional method. FIG. 1... Semiconductor substrate, 2... Lower layer wiring,
3...Coating agent of the present invention, 4...
・Resist mask, 6... Upper layer wiring, 7...
...Through hole. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] On a semiconductor substrate on which predetermined elements and wiring have been formed, a compound of the general formula RSi(OR')_3 (where R is an organic group having 1 to 8 carbon atoms, R' is an alkyl group having 1 to 5 carbon atoms or 1-4
refers to the acyl group of ) and colloidal silica and/or Si(OR')_4
(In the formula, R' is the same as above) A step of applying a coating agent made by mixing a hydrolyzate of a silane compound or a polycondensate thereof, water, and a hydrophilic organic solvent, and applying a coating agent by heat treatment. A semiconductor characterized by comprising the steps of: curing an agent to form a cured film; forming a resist mask on the cured film using a photolithography process and etching the cured film; and removing the resist mask. A method for forming an insulating film on a substrate.