JP3200586B2 - Method and apparatus for forming coating film - 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 and a method for forming the same.
Device .

[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. 6 schematically shows the state of denaturation of the coating solution in this method. First, when the coating solution is first applied to the wafer, TEOS particles or colloid 10 are dispersed in the solvent 11 (FIG. 6). (See FIG. 6A.) Then, when this coating solution is exposed to an alkaline atmosphere, TEOS undergoes polycondensation and hydrolysis, and the coating film gels to form a network structure of TEOS 12 (see FIG. 6B). . Then, the solvent in the coating film is replaced with another solvent 13 in order to remove moisture in the coating solution (see FIG. 6C), and then dried to obtain a coating film of a silicon oxide film.

In the solvent replacement step shown in FIG. 6C, a solvent having a lower surface tension than ethanol is used for the purpose of removing water, and TEO is used when the solvent evaporates.
Another purpose is to prevent a large force from being applied to the network structure of S to prevent the structure of the film from being collapsed.

Here, when the sol-gel method is applied to an actual production line, in a process of forming a coating film, a coating solution is supplied substantially to the center of rotation of the wafer surface, and then the wafer is rotated. We are considering forming a coating film by extending the entire wafer surface using the centrifugal force of rotation. At this time, it is considered that the coating liquid is prepared by mixing TEOS and the solvent in advance, storing the mixed liquid (coating liquid) in a tank or the like, and supplying the stored coating liquid to the wafer surface. .

[0006]

However, when a coating film is formed using a coating solution prepared in advance and stored in a tank, the occurrence of unevenness in film thickness and film quality may be visually confirmed. For this reason, when the present inventors confirmed,
It has been empirically recognized that deterioration of film quality is observed when a coating solution that has been used for a certain period of time after mixing TEOS and a solvent is applied to a wafer, which is a problem.

The present invention has been made under such circumstances, and an object of the present invention is to provide a technique capable of suppressing a deterioration in the quality of a coating film and, as a result, obtaining a high-quality thin film such as an interlayer insulating film. It is in.

[0008]

For this reason, the method for forming a coating film of the present invention comprises a first liquid containing water and particles or colloids of a starting material of a film-forming component which is insoluble or hardly soluble in water; Mixing a second liquid composed of an organic solvent in which a film forming component is dissolved, and after the step, a mixed liquid containing the first liquid and the second liquid is supplied to the surface of the substrate within 6 minutes. And then gelling particles or colloid in the coating film applied to the substrate to obtain a thin film, for example, a silicon oxide film.

In such a method, the mixed liquid within six minutes after the first liquid and the second liquid are mixed is applied to the surface of the substrate. As a result, a high-quality thin film such as a silicon oxide film can be obtained.

Here, in the present invention, after the step of applying the mixed liquid to the surface of the substrate within 6 minutes after mixing the first and second liquids, the mixed liquid is applied to the surface of the next substrate. Before the cleaning, a washing step of washing the mixing section of the first and second liquids and the flow path of the mixed liquid downstream of the mixing section with an organic solvent such as an alcohol may be performed. The mixed liquid remaining in the flow path of the mixed liquid after 6 minutes or more is washed with the organic solvent, so that the old mixed liquid remaining in the flow path when the next substrate is processed is processed. Since the liquid is not applied, deterioration of the quality of the applied film is suppressed. When alcohol is used as the organic solvent, the alcohol dissolves the starting material of the film-forming component and water, so that the inside of the flow path can be more easily washed. The coating film forming apparatus of the present invention is a film forming component that is insoluble or hardly soluble in water.
Liquid containing particles or colloids of the starting material and water
And the organic solvent in which water and film forming components are dissolved.
A second container storing a liquid comprising a medium and a first container
Between the liquid supplied from the second container and the liquid supplied from the second container.
Mix the mixing part to be mixed and the mixed liquid mixed in the mixing part
A nozzle for supplying to the substrate surface within a predetermined time afterward;
The liquid in the container and the second container to and from the mixing section
And a liquid supply pipe for sending the liquid to the nozzle.
And

[0011]

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 forming a coating film, an aging unit U1 for performing a gelling process, and a solvent replacement process are performed. The solvent replacement units U2 are arranged in this order. Processing units U3 to U are also provided on the other side of the transport path 24.
6 for these processing units U3 to U6, a hydrophobic treatment, a cooling treatment and a heat treatment (baking treatment).
Units for performing such operations are respectively assigned.

Next, a method of forming a coating film performed by such an apparatus will be briefly described with reference to FIG. 2. In this apparatus, after a wafer W is subjected to a hydrophobic treatment and a cooling treatment, the coating unit 3 is formed by a main arm 23. , An aging unit U1 and a solvent replacement unit U2, and a predetermined process is performed in each of these units.

That is, in the coating unit 3, as shown in FIG. 2A, a coating liquid nozzle 5 described later applies a coating liquid nozzle 5 to a rotation center of a surface of the wafer W suction-held by a wafer holding unit 31 described later. X is supplied, and then FIG.
By rotating the wafer W as shown in (1), the coating solution X is spread over the entire surface of the wafer W by centrifugal force to form a coating film (coating film forming process).

Next, in the aging unit U1, a process of gelling the colloid of TEOS contained in the coating film on the wafer W and chaining the colloids in a network (gelation process) is performed. In the processing chamber 25 filled with the vapor of the
And heated to around 100 ° C. (FIG. 2C). In this step, instead of heating, the processing may be performed at room temperature in the processing chamber 25 filled with ammonia gas, and the gelation of the colloid of TEOS may be promoted by the ammonia gas as an alkali catalyst. The processing chamber 25 is filled with the vapor of ethylene glycol in order to suppress evaporation of the solvent in the coating solution.

Subsequently, in the solvent replacement unit U2, an ethanol-free surface is placed almost at the rotation center of the surface of the coating film M on the wafer W.
And HMDS (hexamethylenediamine) and heptane are sequentially supplied to replace the solvent in the coating film M with another solvent (solvent replacement process). For this reason, in the solvent replacement unit U2, as shown in FIG. 2D, the wafer W is held horizontally by the wafer holding portion 26 which is rotatable around a vertical axis, and first, ethanol is applied to the surface of the wafer W. After dripping almost at the center of rotation, the wafer W is rotated,
It is 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 M, and as a result, the water is replaced by the ethanol.

Subsequently, HMDS is similarly supplied to the surface of the wafer W to remove the 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 subjected to the predetermined processing in the solvent replacement unit U2 is transferred to the bake unit by the main arm 23 and baked in the unit. An interlayer insulating film made of an oxide film is formed.

Here, the coating film forming method of the present invention is characterized by a coating film forming process. Next, the coating unit 3 in which this process is performed will be described with reference to a vertical side view of FIG. In the drawing, reference numeral 31 denotes a chuck for holding the wafer W horizontally (including a substantially horizontal state).
1 is constituted by, for example, a vacuum chuck,
The rear surface side of the wafer W is held by suction. At the center of the lower surface of the chuck 31, a rotating shaft 33 that can be moved up and down and rotatable by a driving unit 32 is attached. It can move up and down with respect to the processing position of the wafer W shown by the solid line, and can rotate around a vertical axis.

A fixed cup 4 for surrounding the chuck 31 and the wafer W at the processing position is provided.
Is formed, and the opening 41 is opened and closed by a lid 42 provided so as to be able to move up and down. A drain pipe 43 and an exhaust pipe 44 are connected to the bottom of the fixed cup 4.

Above the wafer W at the processing position, a coating liquid nozzle 5 for supplying a coating liquid, which will be described later, to a substantially rotational center of the wafer surface (coating film formation surface) has a tip end of the nozzle 5. Is attached to the supporting arm 51 so as to face substantially the center of rotation of the wafer surface. The support arm
The drive unit 52 is configured to be able to move in the horizontal direction by the drive unit 52, so that the application liquid nozzle 5 supplies the application liquid to the surface of the wafer W (the position shown in FIG. Nozzle cleaning unit 5 provided outside W
3 is moved. The nozzle cleaning unit 53 is configured by connecting a drainage passage 53b to a lower surface of, for example, a cylindrical liquid receiving unit 53a for receiving a liquid flowing out of the coating liquid nozzle 5.

One end of a coating liquid supply pipe 61 for supplying the coating liquid X to the nozzle 5 is connected to the coating liquid nozzle 5. The other end of the coating liquid supply pipe 61 is connected to a mixing section 62. It is connected to the. The coating liquid supply pipe 61 has, for example, a double pipe structure including an inner pipe and an outer pipe, and the temperature control liquid flows through the outer pipe.

In the mixing section 62, a plurality of, for example, two storage tanks 63 and 64 for storing a first liquid and a second liquid, which are components of the coating liquid X, respectively, are provided with pumps P1 and P2.
The first and second storage tanks 63, 64 are connected via solution supply pipes 63a, 64a provided with P2.
The liquids stored in the mixing unit 62 are mixed by the mixing unit 62 and supplied to the coating liquid nozzle 5 via the coating liquid supply pipe 61.

Here, the coating solution X will be described. The coating solution X is obtained by dispersing a metal alkoxide, for example, a colloid or particles of TEOS, which is a starting material of a film-forming component, in a solvent. Solution,
Ethylene glycol, water and traces of hydrochloric acid (HCl) are used.

In such a coating solution X, TEOS colloids or particles are insoluble or hardly soluble in water, and a liquid obtained by mixing the TEOS colloids or particles with ethylene glycol water and hydrochloric acid is a first liquid. It is stored in the first storage tank 63 as S1. The ethanol solution is an organic solvent that dissolves water and TEOS colloid and the like, and is used as the second liquid S2 in the second storage tank 64.
Is stored in

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

First, as shown in FIG. 4 (a), a coating liquid X is supplied from the coating liquid nozzle 5 to a substantially central portion of the surface of the wafer W to form a coating film on the surface.
That is, the first liquid S1 and the second liquid S2 are mixed by the mixing unit 62.
To form a coating liquid X (mixed liquid), and apply the coating liquid X to the surface of the wafer W within 6 minutes after mixing the liquids.

Specifically, the pumps P1 and P2 are operated,
A predetermined amount of the first liquid S1 and the second liquid S2 are supplied to the mixing unit 62 from the first and second storage tanks 63 and 64,
In the mixing section 62, the first and second liquids S
The coating liquid X is prepared by mixing 1 and S2, and the coating liquid X is supplied to the surface of the wafer W via the coating liquid supply pipe 61. Next, the wafer W is rotated, and the coating liquid X is diffused and spread over the entire wafer surface by centrifugal force to form a coating film. In this way, the coating liquid X is supplied to the surface of the wafer W to form a coating film on a predetermined number of wafers W, for example, within six minutes after the first and second liquids S1 and S2 are mixed.

After the coating film is formed, the fixed cup 4
From the thinner nozzle (not shown) inside the wafer W
Is sprayed on the peripheral part of the peripheral part to remove the coating film on the peripheral part,
After that, the lid 42 and the chuck 31 are raised to transfer the wafer W from the chuck 31 to the transfer arm 23, and to transfer the wafer W to the aging unit U1 and the solvent replacement unit U2 sequentially.

Subsequently, in the coating unit 3, the next wafer W
Before applying the coating liquid X to the surface of the substrate, a step of washing the flow path of the coating liquid X formed by the mixing unit 62 and the coating liquid supply pipe 61 with an organic solvent as shown in FIG. . That is, the supply of the first liquid to the mixing unit 62 is stopped after the application liquid nozzle 5 is moved to the upper side of the nozzle cleaning unit 53, and only the second liquid is supplied to the application liquid supply pipe via the mixing unit 62. 61.

In this way, the flow path of the coating liquid X is gradually replaced from the coating liquid X with an organic solvent, in this example, an ethanol solution S2 from the upstream side (see FIG. 4B).
After that, it is completely replaced by the ethanol solution S2 (FIG. 4).
(See (c))), whereby the flow path is washed with the ethanol solution S2. At this time, the coating liquid X and the ethanol solution S2 flowing out from the coating liquid nozzle 5 are supplied to the liquid receiving section 53.
The liquid is discharged from the liquid discharge passage 53b through the line a. Here, it is desirable to use a component that dissolves a starting material of a film forming component and water as an organic solvent for washing the flow path. Examples of such an organic solvent include an ethanol solution and IPA (isopropyl alcohol). Can be used.

Thus, the ethanol solution S2
After the replacement, the first and second liquids S1 and S2 are supplied into the flow path as shown in FIGS. 4C and 4D,
The flow path is replaced with the coating liquid X, and then the coating liquid nozzle 5
Is moved to the supply position, and the process of forming a coating film on the wafer W is performed again. At this time, after moving the coating liquid nozzle 5 to the supply position, the flow path is replaced with the coating liquid X, so that the ethanol solution and the coating liquid X
May be replaced.

According to the above-described embodiment, the first liquid S
Since the coating liquid X within 6 minutes after the mixing of the first liquid S2 with the second liquid S2 is applied to the surface of the wafer W, deterioration of the coating film quality is suppressed as is clear from the experimental results described later.
The experiments performed by the present inventors are as follows. That is, the first liquid S1 and the second liquid S2 are mixed to generate the coating liquid X, and after mixing, the time for supplying the coating liquid X to the surface of the wafer W is changed. Thus, a coating film was formed on the surface of the wafer W by the above-described method, and the state of the formed coating film was visually checked.

At this time, when the time for mixing the first and second liquids S1 and S2 and supplying them to the surface of the wafer W elapses about 6 minutes, the present inventors consider the quality of the coating film to be formed. Since it was empirically understood that deterioration was observed, the time from mixing to supply to the surface of the wafer W was 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes,
The experiment was performed by setting to 6, 10 and 30 minutes, respectively.

For the coating film obtained under each condition, in-plane uniformity of film thickness = (standard deviation of film thickness in wafer surface) / (average film thickness in wafer surface) × 100 (%). And visually observed. The result is shown in FIG. However, ○ indicates a state in which no abnormality was observed in the coating film, and × indicates a state in which radial traces of particles running on the surface were observed.
From this result, if the coating liquid X within 6 minutes after mixing the first and second liquids S1 and S2 is used, deterioration of the film quality of the formed coating film and in-plane non-uniformity of the film thickness can be suppressed. It was understood.

As described above, when the coating solution X having a time longer than 5 minutes after mixing TEOS and a solvent such as an ethanol solution is used, the thickness and quality of the coating film become uneven. Although it is not clear, the present inventors speculate as follows. That is, the coating solution X is a mixed solution of TEOS and a solvent as described above. However, when TEOS and the solvent are mixed, hydrolysis and polymerization of TEOS occur. It is considered that the colloid grows too much and deviates from an optimum colloid state for obtaining an appropriate film quality, thereby causing unevenness in the thickness and film quality of the coating film.

At this time, since TEOS is hardly soluble in water and soluble in alcohol, the hydrolysis and polymerization of TEOS are carried out for a predetermined time after TEOS, water and hydrochloric acid are dissolved in the ethanol solution. It is presumed to occur later, for example,
This may occur when more than 6 minutes have passed since the mixing of the solution with the other components.
Therefore, as in the present embodiment, the components of the coating liquid X are composed of an ethanol solution (second liquid) and other components (first liquid).
If the coating film is formed using the coating liquid X within 6 minutes after mixing these, the coating liquid X can be used before the growth of the colloid is excessively advanced. It is presumed that deterioration of the film quality of the formed coating film is suppressed.

Also, as in the present embodiment, the first and second
After forming a coating film on a predetermined number of wafers W using the coating liquid X within 5 minutes after mixing the liquids S1 and S2, the coating liquid X is applied before coating the coating liquid X on the next wafer W. Part 6
2 and the flow path on the downstream side of the mixing section 62 are washed with an organic solvent, the old coating liquid X that has passed 5 minutes or more after mixing does not remain in the flow path. When processing the wafer W, the old coating liquid X is not supplied onto the wafer W, and the deterioration of the quality of the formed coating film is suppressed.

Further, at this time, if an alcohol such as an ethanol solution is used as the organic solvent, TEOS, water and hydrochloric acid are dissolved in the ethanol solution as described above, so that the ethanol solution is present in the flow path. Each component of the coating solution X is dissolved by the ethanol solution, and the washing in the flow path can be performed more easily. Furthermore, as in the present embodiment, the first and second
If the liquids S1 and S2 are sent from different storage tanks 63 and 64 to the mixing section 62 by the pumps P1 and P2, the mixing ratio of the first and second liquids S1 and S2 can be easily changed. There is also an advantage that can be.

As described above, according to the above-described embodiment, since the hydrolysis and polymerization of the coating solution X supplied to the surface of the wafer W are suppressed, the film quality of the coating film caused by the decomposition of the coating solution X is reduced. Is suppressed, and as a result, a high-quality thin film such as an interlayer insulating film can be formed.

As described above, in this embodiment, the first and second liquids S1 and S2 are mixed in another place without providing the first and second storage tanks 63 and 64, the mixing section 62, and the like. The mixed liquid (coating liquid X) may be applied to the surface of the wafer W within 6 minutes after mixing. Further, the vapor of ethylene glycol may be supplied into the fixed cup 4 and the coating liquid X may be supplied after the inside of the cup 4 is filled with the vapor. There is an effect that the evaporation of the solvent is suppressed.

As described 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 treatment, and a thin film, for example, an interlayer insulating film is formed by performing a gelling treatment after the formation of the coating film. You may make it.

[0042]

According to the present invention, a first liquid containing particles or colloid of a starting material of a film forming component and water and a second liquid composed of water and an organic solvent in which the film forming component is dissolved are mixed. Then, by applying the mixed solution to the surface of the substrate within 6 minutes after preparation to form a coating film, deterioration of the coating film quality is suppressed, and as a result, a high quality thin film such as an interlayer insulating film is formed. Obtainable.

[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 process chart for explaining a coating film forming method of the present invention.

FIG. 3 is a vertical sectional side view showing an example of a coating unit in which a coating film forming process of the method of the present invention is performed.

FIG. 4 is a process chart for explaining a process of forming the coating film.

FIG. 5 is a characteristic diagram showing a relationship between a coating liquid and a state of film quality of a coating film.

FIG. 6 is a schematic diagram showing a state of denaturation of a coating solution when an interlayer insulating film is formed using a sol-gel method.

[Explanation of symbols]

 Reference Signs List 3 coating unit 31 chuck 4 fixed cup 5 coating liquid nozzle 53 nozzle cleaning section 61 coating liquid supply pipe 62 mixing section 63 first storage tank 64 second storage tank U1 aging unit U2 solvent replacement unit X coating liquid W semiconductor Wafer

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Muramatsu 2655 Tsukure, Kikuyo-cho, Kikuchi-gun, Kumamoto Prefecture Inside the Kumamoto Office of Tokyo Electron Kyushu Co., Ltd. (72) Inventor Yoji Mizutani 3-chome Akasaka 5-chome, Minato-ku, Tokyo No. Tokyo Electron Co., Ltd. Akasaka Office (56) References JP-A-8-46047 (JP, A) JP-A-2-46730 (JP, A) JP-A-64-90034 (JP, A) 8-330303 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/316 H01L 21/312 H01L 21/31 H01L 21/768

Claims (7)

(57) [Claims] 1. A first liquid containing particles or colloids of a starting material of a film-forming component which is insoluble or hardly soluble in water, a first liquid containing water, and a second liquid comprising an organic solvent in which water and the film-forming component are dissolved. And a step of applying a mixed liquid containing the first liquid and the second liquid to the surface of the substrate within 6 minutes after this step; and then applying the applied liquid to the substrate. A step of gelling particles or colloids in the film to obtain a thin film, and a method for forming a coating film. 2. A first liquid containing particles or colloid of a starting material of a film forming component insoluble or hardly soluble in water, a first liquid containing water, and a second liquid comprising water and an organic solvent in which the film forming component is dissolved. And a step of applying a mixed liquid containing the first liquid and the second liquid to the surface of the substrate within 6 minutes after this step. Before applying the mixed solution on the surface of the next substrate, a washing step of washing the mixing section and the flow path on the downstream side of the mixing section with an organic solvent, and in the coating film applied to the substrate, A method of gelling particles or colloid to obtain a thin film. 3. The method according to claim 2, wherein the organic solvent used in the washing step is an alcohol. 4. The method according to claim 1, wherein the starting material of the film forming component is tetraethoxysilane, and the thin film is a silicon oxide film. 5. The method according to claim 1, wherein the second liquid is alcohol. 6. Starting of a film-forming component which is insoluble or hardly soluble in water.
Stored liquid containing particles or colloid of substance and water
A first container and a liquid containing an organic solvent in which water and film forming components are dissolved are stored.
A second container, a liquid supplied from the first container, and a liquid supplied from the second container.
A mixing section for mixing the liquid to be mixed with the liquid to be mixed, and a substrate within a predetermined time after mixing the mixed liquid mixed in the mixing section.
Nozzle to be supplied to the surface and liquid in the first and second containers to the mixing section
And a liquid supply pipe for feeding the liquid from the section to the nozzle . 7. A liquid supply pipe for sending liquid from a mixing section to a nozzle.
The mixed liquid is replaced with the liquid in the second container while the mixed liquid is being replaced.
The mixed liquid discharged from the nozzle and discharged from the nozzle is
7. A discharge unit for discharging to a discharge port is provided.
The coating film forming apparatus as described in the above.