JP3225220B2 - Coating film formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a silicon oxide film by applying a coating film on a substrate.

[0002]

2. Description of the Related Art As a method for forming an interlayer insulating film of a semiconductor device, there are a CVD method, a thermal oxidation method and the like, and another method called a sol-gel method. This method
For example, TEOS (tetraethoxysilane; Si (C2 H
5 O) A coating solution in which the colloid of 4) is dispersed in an organic solvent such as an ethanol solution is applied to the surface of a semiconductor wafer (hereinafter simply referred to as a wafer), and the coating film is gelled and dried to oxidize silicon. This is a technique for obtaining a film.
62450 and JP-A-8-59362.

The present inventors are studying the formation of an interlayer insulating film using this sol-gel method. FIG. 5 schematically shows the state of denaturation of the coating solution in this method. First, when the coating solution is first applied to a wafer, TEOS particles or colloid 10 is in a state of being dispersed in solvent 11 (FIG. 5). (See FIG. 5A.) Then, when this coating solution is exposed to an alkaline atmosphere, TEOS undergoes polycondensation and hydrolysis, and the coating film gels, forming a network structure of TEOS 12 (see FIG. 5B). . Then, the solvent in the coating film is replaced with another solvent 13 in order to remove the water in the coating solution (see FIG. 5C), and then dried to obtain a coating film of a silicon oxide film.

In the replacement step of the solvent shown in FIG.
In addition to the purpose of removing water, the purpose of making the membrane hydrophobic is to use a solvent having a lower surface tension than ethanol so that a large force is not applied to the TEOS network structure when the solvent evaporates. It also has the purpose of suppressing the collapse of the film structure.

Here, when the sol-gel method is applied to an actual production line, the present inventors consider that T
The coating liquid, which is obtained by dispersing EOS particles or colloids in a solvent, is supplied to almost the center of rotation of the wafer surface, and then the wafer is rotated around a vertical axis. We are considering forming a coating film by extending the entire surface of the wafer.

[0006]

After the coating liquid is applied to the wafer, it is necessary to suppress the evaporation of the solvent so that the gelation of TEOS is not hindered. For example, a solvent having a high boiling point and difficult to evaporate, for example, ethylene glycol is used. However, since this ethylene glycol has a high viscosity, the use of the ethylene glycol as a component of the solvent makes the coating liquid itself viscous.

On the other hand, the surface of a wafer on which an interlayer insulating film is to be formed has fine irregularities because aluminum wiring is provided. For this reason, simply supplying the coating liquid to the wafer surface and rotating the wafer as described above causes the coating liquid to be viscous and difficult to spread, so that the coating liquid penetrates into fine concave portions on the wafer surface. Hard to go in,
It was difficult to form a coating film on the entire wafer surface. In particular, in recent years, patterns have tended to be miniaturized. However, when the patterns have been miniaturized and the line width of the aluminum wiring has been reduced, there has been a problem that the coating liquid has become more difficult to enter.

The present invention has been made under such circumstances, and an object of the present invention is to make it easier to apply the coating solution on the substrate surface, thereby forming a coating film evenly on the entire substrate surface. An object of the present invention is to provide a technique capable of obtaining a high-quality thin film, for example, an interlayer insulating film.

[0009]

Therefore, a method of forming a coating film according to the present invention comprises applying a coating liquid in which particles or colloids of a starting material of a film forming component are dispersed in a plurality of solvents including ethylene glycol to the surface of a substrate. A coating film forming step of forming a coating film, and a gelling step of gelling particles or colloid in the coating film formed in the coating film forming step,
The coating film forming step includes a step of applying a solution having a viscosity lower than that of the ethylene glycol , in which a starting material and water are dissolved, to a surface of the substrate, and a step of subsequently applying the coating liquid to the surface of the substrate. And characterized in that: Here, for example, tetraethoxysilane can be used as a starting material. Further, after the gelling step, a solvent different from the solvent is supplied to the coating film forming surface of the substrate, and a solvent replacement step for replacing the solvent in the coating film with another solvent may be performed. Good. In this case, the coating film type
The forming step is a step of loading a substrate from the opening into the processing container.
And then closing the opening of the processing container, and then
The vapor of the solvent of the coating solution is supplied into the processing container to
Filling with the steam.
In the processing vessel, the ethylene glycol
Solution with a viscosity less than that of the
Applying a solution to the surface of the substrate, and then applying the solution
Applying the liquid to the surface of the substrate.
Good.

In such a method, in the step of forming a coating film, ethylene glycol is applied before the coating liquid is applied to the substrate.
Since a solution having a viscosity lower than that of the substrate is applied to the entire surface of the substrate, when the application liquid is supplied to the surface, first, the starting material of the application liquid and water are first applied to the solution applied to the entire surface of the substrate. The dissolution causes the coating liquid to mix with the solution, thereby reducing the viscosity of the coating liquid. For this reason, the coating liquid easily spreads on the substrate, and the coating liquid is applied evenly on the entire surface of the substrate. As a result, a high-quality thin film can be formed.

Here, in the method of the present invention, a component having a viscosity smaller than that of ethylene glycol may be used as a solution applied to the substrate surface before the step of applying the coating solution to the substrate surface. In this case, since one of the components of the solvent is applied, the component and the coating solution are apt to be mixed when the coating solution is applied, and no bubbles are generated when these are mixed. A high-quality coating film can be formed. Before the step of applying the coating liquid on the surface of the substrate, an alcohol may be used as a solution applied to the substrate surface, and the alcohol dissolves the starting material and water. The same effect can be obtained.

[0012]

FIG. 1 is a plan view schematically showing an entire configuration of an example of a coating film forming apparatus for carrying out the method of the present invention. Reference numeral 21 denotes an input / output port for a wafer as a substrate. A transfer arm 22 takes out a wafer W from a cassette C placed on a cassette stage CS, and a main arm 23.
It is configured to be passed to. On one side of a conveyance path (guide rail) 24 of the main arm 23, a coating unit 3 for performing a coating film forming process, an aging unit U1 for performing a gelling process, and a solvent replacing for performing a solvent replacing process. The units U2 are arranged in this order.
Processing units U3 to U6 are also arranged on the other side of the transport path 14, and these processing units U3 to U6 are units for performing hydrophobic treatment, cooling treatment, heat treatment (baking treatment), and the like. Assigned.

Next, the coating unit 3 will be described with reference to a longitudinal side view of FIG. In the drawing, reference numeral 31 denotes a chuck for holding the wafer W horizontally (including a substantially horizontal state). The chuck 31 is constituted by, for example, a vacuum chuck, and is adapted to hold the back surface of the wafer W by suction. Has become. A rotation shaft 33 that can be moved up and down and rotated by a driving unit 32 is provided substantially at the center of the lower surface of the chuck 31.
The chuck 31 is moved up and down between a delivery position of a wafer W above the cup, which will be described later, and a processing position of the wafer W shown by a solid line in the drawing, and the chuck 31 is vertically moved. It can rotate around its axis.

A cup 4 is provided around the chuck 31 and the wafer W at the processing position to form a processing container for surrounding the chuck 31 and the wafer W. The wafer W is placed on the upper surface of the cup 4. An opening 41 that can pass through is formed, and the opening 41 is opened and closed by a lid 42 that can be moved up and down. A solvent vapor supply pipe 51 for supplying a component of a solvent used in the coating liquid X described later, for example, a vapor of ethylene glycol into the cup 4 is connected to a side wall portion of the cup 4. Are generated at the solvent vapor generation source 52. Further, a drain pipe 53 and an exhaust pipe 54 are connected to the bottom of the cup 4.

The lid 42 has a coating liquid nozzle 61 for supplying a coating liquid X to the rotation center of the wafer surface (coating film forming surface) and a solution S at a rotation center of the wafer surface.
And a solution nozzle 62 for supplying
1, 62 are attached to the lid 42 in such a manner that the tips of the wafers 62 face obliquely downward toward the center of rotation of the wafer surface.

Here, the coating solution X will be described. The coating solution X is a metal alkoxide as a starting component such as TE
The colloid or particles of OS are dispersed in a solvent. As the solvent, for example, ethylene glycol, ethyl alcohol, water and a very small amount of hydrochloric acid are used. One example of the ratio of each component in the coating liquid X is, for example, TEOS
And water are almost equal in molar ratio, and the ethylene glycol solution and the ethanol solution are several times the amount of water in molar ratio.

The solution S supplied to the wafer surface from the solution nozzle 62 is a solution having a lower viscosity than the component having the highest viscosity among the components of the solvent of the coating solution X, and the metal alkoxide and water are It is desirable to use one that dissolves. Here, the component having the highest viscosity among the components of the solvent of the coating liquid X is ethylene glycol.
Metal alkoxides such as S are generally insoluble in water, but are known to be soluble in alcohols and organic solvents. Therefore, as the solution S used in the present embodiment, an alcohol or an organic solvent having a viscosity lower than that of ethylene glycol can be used. In particular, ethanol, which is one of the components of the solvent of the coating solution X, is used. It is desirable to use

Next, the method of the present invention performed by the above-described coating film forming apparatus will be described. In this coating film forming apparatus, the wafer W is subjected to a hydrophobizing treatment and a cooling treatment, and then sequentially transferred by the main arm 23 to the coating unit 3, the aging unit U1, and the solvent replacement unit U2. After the processing is performed, baking processing is performed.

Here, a coating film forming process performed by the coating unit 3 will be described with reference to FIGS. First, the lid 42 is raised to the position indicated by the dashed line in FIG. 2, and the chuck 31 is also raised to the position above the cup 4. The wafer W transferred to the unit 3 by the main arm 23 at the position indicated by the dashed line in FIG. It is delivered to the chuck 31. Next, the chuck 31 is lowered to the processing position and the lid 42 is lowered to seal the cup 4.

In this example, for example, the ethylene glycol vapor is supplied into the cup 4 from the solvent supply pipe 51 while exhausting from the exhaust pipe 54, and the exhaust is stopped after the inside of the cup 4 is filled with the vapor. As shown in FIG. 3A, a solution S, for example, a 99.9% ethanol solution is supplied from the solution nozzle 62 to a substantially rotational center of the wafer W. Then FIG.
As shown in (b), the wafer W is rotated by the chuck 31, and the solution S is diffused and spread over the entire surface of the wafer W by centrifugal force.

Subsequently, as shown in FIG. 3C, a coating liquid X is supplied from a coating liquid nozzle 61 to a substantially rotational center of the wafer W. At this time, the coating solution X does not evaporate the applied solution S,
It is desirable to supply the solution S when the solution S is present on the surface of the wafer W. Next, as shown in FIG. 3D, the wafer W is rotated by the chuck 31, and the coating liquid X is diffused and spread over the entire wafer surface by centrifugal force to form a coating film. Although not shown, the thinner is then sprayed from the thinner nozzle in the cup 4 onto the peripheral portion of the wafer W to remove the coating film on the peripheral portion. In this example, the reason why the inside of the cup 4 is filled with the vapor of ethylene glycol is to suppress evaporation of the solvent in the coating liquid.

Thereafter, the inside of the cup 4 is evacuated, for example, with the lid 42 slightly raised, and the lid 42 and the chuck 31 are raised to transfer the wafer W from the chuck 31 to the transfer arm 23.
To the aging unit U1 and the solvent replacement unit U2. In each of the units U1 and U2, a gelation step and a solvent replacement step are performed. Next, these steps will be briefly described with reference to FIG.

First, in the gelling step, a process is performed in which the colloid of TEOS contained in the coating film on the wafer W is gelled and the colloids are chained in a network, and therefore, the colloid is filled with the vapor of ethylene glycol. In the processing chamber 71,
The wafer W is heated to about 100 ° C. by the heating plate (FIG. 4A). The reason why the vapor of ethylene glycol is introduced into the processing chamber 71 is to suppress the evaporation of the solvent in the coating film. Therefore, the vapor becomes 100% at the temperature in the processing chamber 71, for example. Has been adjusted. In this gelation step, instead of heating, a treatment is performed at room temperature in a treatment chamber 71 filled with ammonia gas, and TEOS is performed using ammonia gas as an alkali catalyst.
The gelation of the colloid may be promoted.

Subsequently, in a solvent replacement step, ethanol, HMDS (hexamethylenediamine) and heptane are sequentially supplied to the rotation center of the surface of the wafer W to replace the solvent in the coating film with another solvent. Is performed. For this reason, in the solvent replacement unit U2, as shown in FIG. 4B, the wafer holding unit 7 configured to be rotatable around a vertical axis.
2 allows the wafer W to be held horizontally,
Three nozzles 73 that respectively discharge HMDS and heptane
(73a, 73b, 73c) are prepared.
3 are sequentially taken out of the nozzle receiving portion (not shown) by the transfer arm 74 in this order, and are transferred to the center of the wafer W.

In this step, first, the wafer W is rotated, and the ethanol is dropped on the rotation center of the surface of the wafer W and diffused over the entire surface of the wafer W by centrifugal force. As a result, the ethanol dissolves in the water in the coating film, and as a result, the water is replaced by the ethanol. Subsequently, the HMD is rotated while the wafer W is rotated in the same manner.
S is supplied to the surface of the wafer W to remove hydroxyl groups in the coating film. Further, heptane is supplied to the surface of the wafer W, and the solvent in the coating film is replaced with heptane. The reason for using heptane is to reduce the force applied to the porous structure, that is, the network structure of TEOS by using a solvent having a small surface tension so that the structure is not broken.

The wafer W which has been subjected to the predetermined processing in the solvent replacement unit U2 is transferred to the bake unit by the main arm 13 and baked by the unit. An interlayer insulating film made of an oxide film is formed.

According to the above-described embodiment, in the coating film forming step, ethanol is applied to the entire surface of the wafer before the application of the coating liquid, and the ethanol does not evaporate on the surface of the wafer. When ethanol is present, the coating liquid X is supplied to the surface. Here, since ethanol has a lower viscosity than ethylene glycol, ethanol itself is easily diffused over the entire wafer surface, and penetrates evenly into the fine irregularities formed on the surface.

When the coating liquid X is supplied and diffused in the state where ethanol is present on the entire wafer surface, the components constituting the coating liquid X, that is, TE
Since OS, water, ethylene glycol and HCl are all soluble in ethanol, the coating solution X mixes with ethanol on the wafer surface and mixes with ethanol where ethanol exists. It enters in a state that fits.

Further, since ethanol has a lower viscosity than ethylene glycol, as described above, the viscosity of the coating solution X mixed with ethanol becomes lower, and the state becomes easier to diffuse. Therefore, when the wafer W is rotated, the coating liquid X
Extends uniformly over the entire surface of the wafer and penetrates into fine irregularities, so that a coating film is formed on the entire surface of the wafer. At this time, the viscosity of the solution S is lower than that of ethylene glycol, and even when a solution or an alcohol in which the metal alkoxide and water are dissolved is used, the components of the coating solution X and the solution S are mixed. The viscosity of the coating solution X to be spread on the surface of the wafer W is reduced, and the same effect is obtained.

Further, when ethanol, which is one of the components of the solvent of the coating solution X, is used as the solution S, since ethanol is contained as a solvent in advance, the solution S on the wafer surface and the coating solution X The mixing takes place quickly. For this reason, when the solution S and the coating liquid X are mixed, bubbles are not generated and the bubbles do not remain in the coating film, so that a higher quality coating film is formed.

If a solution having a viscosity higher than that of ethylene glycol is used as the solution S, the solution S itself is difficult to diffuse and hardly enter fine irregularities on the wafer surface. Since the viscosity of the coating solution X after the mixing of X increases, the coating solution X
Is difficult to spread, and it becomes difficult to apply the coating liquid X over the entire wafer surface.

If a solution in which metal alkoxide or water is not dissolved is used as the solution S, the viscosity of the coating solution X cannot be reduced because the solution S and the coating solution X do not mix. There is also a possibility that the application of the coating liquid X to the surface of the wafer W may not be possible due to the interference with the solution S. Note that the solvent of the coating liquid is not limited to containing water, but when water is contained, it is necessary that the starting material and water are dissolved in the solution.

As described above, according to the above-described embodiment, the coating liquid X can be easily applied to the wafer surface.
Is uniformly applied over the entire wafer surface, so that a coating film can be reliably formed over the entire wafer surface, and as a result, a high-quality thin film, for example, an interlayer insulating film can be formed.

In the above, in the method of forming a coating film of the present invention, it is not always necessary to perform the above-described solvent replacement step, and a thin film such as an interlayer insulating film is formed by performing a gelling step after the coating film forming step. It may be.

[0035]

According to the present invention, the viscosity of the solvent in the coating solution is reduced before the coating solution in which particles or colloid of the starting material of the film forming component are dispersed in the solvent is applied to the surface of the substrate. By applying to the surface of the substrate a solution having a lower viscosity than the highest component and in which the starting material dissolves
The application of the coating liquid to the substrate surface is facilitated, whereby a coating film is uniformly formed on the entire substrate surface, and as a result, a high-quality thin film, for example, an interlayer insulating film can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing an overall configuration of an example of a coating film forming apparatus in which a method of the present invention is performed.

FIG. 2 is a vertical sectional side view showing an example of a coating unit in which a coating film forming step of the method of the present invention is performed.

FIG. 3 is a process chart for explaining a solvent replacement step of the method of the present invention.

FIG. 4 is a process chart for explaining a gelation step and a solvent replacement step of the method of the present invention.

FIG. 5 is a schematic view showing a state of modification of a coating solution when an interlayer insulating film is formed by using a sol-gel method.

[Explanation of symbols]

 3 Coating Unit 31 Chuck 4 Cup 61 Coating Liquid Nozzle 62 Solution Nozzle U1 Aging Unit U2 Solvent Substitution Unit S Solution X Coating Liquid W Semiconductor Wafer

──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazutoshi Yano 2655 Tsukure, Kikuyo-cho, Kikuchi-gun, Kumamoto Prefecture Tokyo Electron Kyushu Co., Ltd. Kumamoto Office (72) Inventor Yoji Mizutani 5-3 Akasaka, Minato-ku, Tokyo No. 6, in the Akasaka Office of Tokyo Electron Limited (56) References JP-A-5-243140 (JP, A) JP-A 8-162450 (JP, A) JP-A 8-316311 (JP, A) JP-A-9-134909 (JP, A) JP-A-10-70121 (JP, A) JP-A-11-3888 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21 / 312-21/318

Claims (7)

(57) [Claims] 1. A coating film forming step of forming a coating film by applying a coating solution in which particles or colloids of a starting material of a film forming component are dispersed in a plurality of solvents including ethylene glycol to a surface of a substrate; A gelling step of gelling particles or colloid in the coating film formed in the forming step, wherein the coating film forming step is a solution having a viscosity smaller than that of the ethylene glycol , and the starting material is dissolved. A method for forming a coating film, comprising: a step of applying a solution to be applied to the surface of a substrate; and a step of subsequently applying the coating solution to the surface of the substrate. 2. The method according to claim 1, wherein the solution having a viscosity lower than that of ethylene glycol is one of components of a solvent of the coating solution. 3. The method according to claim 1, wherein the solution having a viscosity lower than that of ethylene glycol is alcohol.
Or the method for forming a coating film according to 2. 4. The method according to claim 1, wherein the starting material is tetraethoxysilane. 5. A solvent replacement step for supplying a different solvent from the solvent to the coating film forming surface of the substrate on which the gelation step has been performed, and replacing the solvent in the coating film with another solvent. The method for forming a coating film according to any one of claims 1 to 4, comprising: 6. The method according to claim 6, wherein the step of forming the coating film comprises opening the inside of the processing container.
A step of loading the substrate from an opening, a step of closing the opening of the processing container, and then, supplying a vapor of the solvent of the coating liquid into the processing container.
And filling with the steam, in the processing vessel filled with the steam, on the surface of the substrate,
A solution having a viscosity lower than that of the ethylene glycol
To apply a solution in which the starting material dissolves to the surface of the substrate.
And then applying the coating solution to the surface of the substrate
5. The method according to claim 1 , further comprising:
Or a method for forming a coating film. 7. A composition having a viscosity lower than that of said ethylene glycol.
The solution is one of the components of the solvent of the coating solution, and
Use a solvent different from the solvent supplied as steam in the
7. The method as claimed in claim 1, wherein:
Or a method for forming a coating film.