JP2866295B2 - Method of applying coating liquid to substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer, a glass substrate for a liquid crystal display (LCD), a glass substrate for a photomask and the like, a photoresist solution, a polyimide resin, a silica-based film forming material, a dopant material and the like. A method of applying a coating liquid on the surface of the substrate by supplying the coating liquid in a thin film form, and in particular, applying the coating liquid over the entire surface of the substrate by rotating the substrate around a vertical axis to thereby form a uniform coating of the coating liquid. The present invention relates to a rotary coating liquid coating method for adjusting a film thickness.

[0002]

2. Description of the Related Art When a coating film of a coating solution is formed on a surface of a substrate such as a semiconductor wafer, a glass substrate, and a mask substrate by a spin coating method (spinning), a coating solution such as a photoresist solution is usually supplied onto the substrate. After that, first, the substrate is rotated at a relatively low speed, for example, about 1,000 rpm, around a vertical axis in a horizontal plane, and the coating liquid supplied on the substrate is diffused and flowed by centrifugal force, thereby causing the surface of the substrate to flow. The coating is spread over the entire surface (diffusion flow process), and then the substrate is rotated at a high speed, for example, at a rotation speed of 3,000 rpm, and the coating of the coating solution spread over the entire surface of the substrate is adjusted to a uniform film thickness and dried. (Shake-off process).

In the case where a coating film of a coating solution is formed by the above-described spin coating method, during the rotation of the substrate after the supply of the coating solution onto the substrate, the evaporation of the solvent in the coating solution from the substrate surface is promoted. The viscosity of the coating liquid applied to the substrate surface gradually increases, and the fluidity decreases. As a result, as shown in FIG. 9A, the surface of the substrate 1 has a profile (hereinafter, referred to as a profile) having a constant thickness along the surface shape of the substrate 1.
Coating liquid film 2 with “contour type profile”
Is formed.

[0004] As a coating apparatus using a rotary coating method, for example, Japanese Utility Model Publication No. 4-51907 discloses a spinner that adsorbs and holds a substrate and rotates it around a vertical axis. There is disclosed an application device in which an opening for opening and closing a substrate is formed on the upper surface of a case, and a lid that can be freely opened and closed is provided in the opening. In this coating device, since the case rotates integrally with the spinner in a closed state, airflow hardly occurs in the case even during rotation of the substrate, and air acts as a resistance to the coating liquid dropped on the substrate surface. Therefore, the coating liquid on the substrate surface is prevented from receiving air resistance and rising to the edge of the substrate, and a coating liquid film having a uniform thickness is formed on the substrate surface. Also, Japanese Patent Publication No. 57-48980, Japanese Patent Publication No. 58-45
No. 88, Japanese Unexamined Patent Publication No. 1-135565, etc. disclose a container or lid integrally with a turntable so as to surround a substrate held in a horizontal position on the turntable to form a sealed or closed space. There is disclosed a coating apparatus in which a rotating table and a substrate held thereon and a container or a lid are integrally rotated. According to the coating apparatus disclosed in these publications, the coating liquid is spin-coated on the substrate in a state where the substrate is placed in an atmosphere of a closed or closed coating liquid solvent, so that the peripheral edge of the large round substrate is In areas where the peripheral speed increases or the wind is cut off during rotation, such as the corners of a square substrate, and the wind is more strongly affected by other parts, the viscosity of the coating liquid increases due to the promotion of evaporation of the solvent components of the coating liquid. As a result, the diffusion flow due to centrifugal force is prevented from being weakened, and the thickness of the coating liquid film is partially prevented from increasing, thereby improving the uniformity of coating. In addition, Japanese Unexamined Patent Publication
No. 0-143871 discloses that a substrate and a spin head are surrounded and sealed by a lower cup fixed to a spindle of a spin head for holding the substrate in a horizontal posture and an upper cup combined with the lower cup, and the lower cup and the upper cup are closed. The cup is integrated with an appropriate lock pin or the like, and the lower cup and the upper cup are driven to rotate by separate motors, so that the rotation direction and the rotation speed of the substrate and the upper and lower cups can be freely selected. An application device is disclosed. According to this coating apparatus, the atmosphere around the substrate (temperature, humidity, vapor pressure of the resist solvent, etc.) is less likely to fluctuate, evaporation of the resist solvent is suppressed, and the resist can be applied to a uniform film thickness. . Further, Japanese Patent Application Laid-Open No. Hei 4-61855 discloses that a substrate held in a horizontal position on a turntable, in particular, a rectangular substrate or a large substrate in parallel with a predetermined small interval,
There is disclosed a rotary coating apparatus in which an upper rotating plate having a size equal to or larger than the outer shape of a substrate is provided, and the upper rotating plate is rotated integrally with a turntable. According to this coating apparatus, the air layer in the flat coating processing space formed between the rotating table and the upper rotating plate rotates together with the rotating table and the upper rotating plate rotating together, and is contained in the coating processing space. Since the movement of air relative to the surface of the substrate is suppressed, the partial increase in the viscosity of the coating solution due to the increase in the viscosity of the coating solution due to the partial promotion of the vaporization of the solvent of the coating solution is eliminated. Coating becomes possible.

[0005]

In the conventional spin coating method, the evaporation of the solvent in the coating liquid from the substrate surface is accelerated during the rotation of the substrate, so that the use efficiency of the coating liquid is low. And so on. In addition, since the viscosity of the coating liquid increases during the coating operation and the flow characteristics change, there is a problem that the thickness and profile of the coating liquid coating differ between the substrates. These problems become more remarkable as the size of the substrate increases.

On the other hand, in the coating apparatus disclosed in each of the above publications, the evaporation of the solvent in the coating liquid from the substrate surface during the rotation of the substrate is suppressed, so that the coating operation is completed (the rotation of the substrate is stopped). Also at (time), the increase in the viscosity of the coating liquid applied to the substrate surface is small, and the coating liquid applied to the substrate surface has fluidity. For this reason, immediately after the end of the coating operation (immediately after the rotation of the substrate is stopped), FIG.
A coating film having a profile as shown in (a) is formed, but the coating solution applied to the substrate surface immediately after the completion of the coating operation until the drying step or during the heating process in the drying step. Flows, and as shown in FIG.
The process shifts to the coating liquid coating 3 having a profile whose surface is flattened (hereinafter, referred to as “flat profile”).
However, for example, when a photoresist film is formed on a substrate surface in a photoetching process, it is necessary to form a film having a contour-type profile, and a coating apparatus having a configuration as described in each of the above publications However, there is a problem that it is difficult to obtain a photoresist film having a profile according to the requirement.

The present invention has been made in view of the above circumstances, and has a contour type profile as shown in FIG. 9A on the substrate surface while maintaining a high use efficiency of the coating liquid. It is an object of the present invention to provide a method for applying a coating solution to a substrate, which can form a coating film with good reproducibility.

[0008]

According to a method of applying a coating solution to a substrate according to the present invention, at least a coating film of a coating solution spread over the entire surface of a substrate in a diffusion flow process is adjusted to a uniform film thickness. In the cutting process, the rotating plate disposed at a slight distance above the substrate in parallel with the substrate is substantially parallel to the substrate in the same vertical direction as the rotation axis of the substrate and in the same direction as the substrate. Evaporation at the same speed, and following the shaking process, a relative speed difference is provided between the rotation speed of the substrate and the rotation speed of the rotary plate to promote the evaporation of the solvent of the coating solution from the substrate surface. I am going through the process. As means for providing a relative speed difference between the rotation speed of the substrate and the rotation speed of the rotating plate in the evaporation promotion process, the rotation of the substrate is stopped, and the rotating plate is continuously rotated at the same speed from the shaking process. Rotate or stop the rotation of the rotating plate, and rotate the substrate at the same speed continuously from the shaking process, or rotate the substrate at the same speed continuously from the shaking process, and rotate the rotating plate. What is necessary is just to rotate in the opposite direction to the substrate, to rotate the rotating plate continuously at the same speed from the shaking-off process, and to rotate the substrate at a lower speed than in the shaking-off process. Further, in the evaporation promotion process, a substrate may be supplied to the substrate surface or a closed space surrounded by the rotating plate and the substrate may be opened to the atmosphere,
Alternatively, the distance between the substrate and the rotating plate may be larger than in the diffusion flow process and the shaking process.

[0009]

When the coating liquid is applied to the surface of the substrate by the above-described method of applying the coating liquid to the substrate, the coating liquid is disposed in parallel with the substrate at a slight distance above the substrate during the shaking process. The air between the substrate and the rotating plate is rotated by the rotating plate rotating at substantially the same speed as the substrate in the same direction as the rotating direction of the substrate around the same vertical axis as the rotation axis of the substrate. Co-rotating with the plate eliminates or reduces the flow of air relative to the surface of the substrate. As a result, solvent evaporation from the coating liquid applied to the substrate surface is suppressed. Then, at the end of the shaking-off process, a coating liquid film having a certain thickness and a certain contour profile as shown in FIG. 9A is formed on the substrate surface.
In addition, in the evaporation promotion process subsequent to the shaking-off process, a relative speed difference is provided between the rotation speed of the substrate and the rotation speed of the rotating plate. Solvent evaporation of the coating liquid from the
The viscosity of the coating liquid applied to the substrate surface gradually increases, and the fluidity decreases. As a result, the coating liquid film formed on the surface of the substrate is changed from the contour profile shown in FIG. 9A during the period from immediately after the end of the coating operation to the drying step or during the temperature raising process in the drying step. The transition to the flat profile as shown in FIG. 9B is prevented.

[0010]

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the configuration of an apparatus for carrying out a method of applying a coating liquid to a substrate according to the present invention, and is a partially broken side view showing a schematic configuration of a main part of the coating liquid coating apparatus. is there. The coating liquid applying apparatus includes a rotation holder 10 that sucks the substrate 1, holds the substrate 1 in a horizontal position, and rotates the substrate 1 about a vertical axis. The rotation holder 10 is integrally connected to the rotation holder 10, and rotates integrally with the rotation holder 10. It has a flat container body 12 having an open upper part, and a rotating plate 16 disposed so as to close the upper opening part 14 of the container body 12 and held rotatably. .

A plurality of suction holes 18 for vacuum-sucking the substrate 1 are formed in the rotation holding table 10, and a vacuum suction path 20 communicating with the suction holes 18 is formed therein.
The vacuum suction path 20 is connected to a vacuum suction source (not shown), for example, a vacuum pump. The rotation holder 10 is connected to a substrate rotation driving motor 22. By controlling the driving of the motor 22 by a control device (not shown), the rotation speed of the rotation holder 10 and thus the rotation speed of the substrate 1 can be changed. I can do it. The container body 12 is
The substrate 1 has a shape that surrounds the lower surface side and the side surface of the substrate 1 to be sucked and held, and a drain hole 24 is formed in the bottom wall portion. Further, in the container 12, the coating liquid applied onto the substrate 1 and scattered from the surface of the substrate 1 to the surroundings as the substrate 1 rotates is repelled toward the substrate 1 and adheres again to the surface of the substrate 1. A coating liquid guide plate 26 for preventing the occurrence of the liquid is provided inside. The coating liquid guide plate 26 is provided obliquely outward and downward, and the coating liquid scattered from the surface of the substrate 1 to the periphery collides with the coating liquid guide plate 26 and flows down to the inner bottom of the container 12. It has become.

The rotary plate 16 is arranged in parallel with the substrate 1 with a slight space above the substrate 1 sucked and held by the rotary holding table 10, and is connected to a rotary plate driving motor 28 in a suspended state. I have. The motor 28 is attached to and held by the mounting holder plate 30, and the mounting holder plate 30 is held by a lifting drive mechanism (not shown). Then, the rotating plate 16, the motor 28, and the mounting holder plate 30 are configured to be integrally moved in a vertical direction by an elevating drive mechanism.
The rotating plate 16 has a coating liquid supply path 32
The liquid supply port 34 is opened at a position facing the center of the substrate 1 which is sucked and held by the rotation holding table 10. The rotating plate 16 is rotated by changing the rotation speed in the normal rotation direction and the reverse rotation direction by controlling the driving of the motor 28 by a control device (not shown).

As shown in FIG. 2, the rotating plate 36 may be formed with a coating liquid supply passage 38 and a ventilation passage 40. Then, gas is introduced through the ventilation path 40 to blow the gas onto the surface of the substrate 1 held by the rotary holding table 10, or is surrounded by the container 12 and the rotating plate 36 through the ventilation path 40. Make the enclosed space open to the atmosphere.

Next, the operation of forming a coating film of the coating liquid on the surface of the substrate by using the coating liquid coating apparatus having the above-described configuration will be described with reference to time charts shown in FIGS. In each of FIGS. 3 to 6, (a) shows the change over time of the rotation speed of the substrate 1, (b) shows the change over time of the rotation speed of the rotating plate 16, and (c) shows the change over time of the rotating plate 16 with respect to the substrate 1. Shows the time-dependent change of the relative rotation speed of each.

First, the rotating plate 16, the rotating plate driving motor 28, and the mounting holder plate 30 are integrally raised to open the opening 14 of the container 12, and the substrate to be coated is transferred through the opening 14 to the container 12. Then, the substrate 1 is vacuum-adsorbed and held on the rotary holding table 10. Next, the rotating plate 16, the motor 28 and the mounting holder plate 30 are lowered integrally, and the opening 14 of the container 12 is closed by the rotating plate 16 as shown in FIG. In this state, the application liquid is supplied to the center of the substrate 1 through the application liquid supply path 32 of the rotating plate 16. After the application liquid is supplied, the substrate 1 is rotated integrally with the rotation holding table 10 and the container 12, and
Also rotate 16 At this time, as shown in FIG.
Are rotated in the same direction as the substrate 1 at the same speed. The substrate 1 and the rotating plate 16 are initially low speed, for example,
It is rotated at a rotation speed of about 00 rpm, and in the process (diffusion flow process), the coating liquid supplied on the substrate 1 is caused to flow toward the outer periphery of the substrate 1 by centrifugal force and spread over the entire surface of the substrate 1. The number of rotations of the substrate 1 and the rotary plate 16 is changed to a high speed, for example, about 3,000 rpm, and in the process (shaking-off process), an excess portion of the coating solution spread over the entire surface of the substrate 1 is removed. 1 is scattered from the surface of the coating liquid 1 and adjusted so that the coating film of the coating liquid has a uniform film thickness. In the diffusion flow process and the shaking-off process described above, as shown in FIG. 3C, no relative rotation occurs between the substrate 1 and the rotating plate 16 (the relative rotation speed between the two). Since it is zero, the flow of air on the surface of the substrate 1 is small, and therefore, evaporation of the solvent in the coating liquid from the surface of the substrate 1 is suppressed. By going through both processes, the surface of the substrate 1 has a predetermined film thickness and a contour type profile,
A fluid coating film having fluidity is formed. In the above,
After the application liquid is supplied to the substrate surface, the substrate 1 and the rotating plate 16 are rotated. However, another application liquid supply form may be selected according to the characteristics of the application liquid.
The application liquid may be supplied to the surface of the substrate 1 while rotating the substrate 1 and the rotating plate 16 at a low speed.

When a coating liquid film having a predetermined thickness is formed on the surface of the substrate 1, the rotation of the substrate 1 is stopped.
16 is to rotate at the same speed continuously from the shaking-off process. As a result, as shown in FIG. 3C, a relative rotation occurs between the substrate 1 and the rotating plate 16, and the air on the surface of the substrate 1 flows violently, so that the air from the surface of the substrate 1 Evaporation of the solvent in the coating liquid is promoted. As a result, the viscosity of the coating liquid applied to the surface of the substrate 1 increases, the fluidity decreases, and the profile of the coating liquid film formed on the surface of the substrate 1 is prevented from shifting from the contour type to the flat type. Is done. In addition, a gas is supplied to the surface of the substrate 1 through the air passage 40 in the evaporation promoting process by using the rotating plate 36 having the structure shown in FIG.
The evaporation of the solvent in the coating liquid may be further promoted by opening the closed space surrounded by the container body 12 and the rotating plate 36 to the atmosphere. In this case, it is necessary to close the air passage 40 in the diffusion flow process and the shaking-off process.

When the evaporation promoting process is completed, the rotation of the rotating plate 16 is also stopped, and the rotating plate 16, the motor 28 and the mounting holder plate are stopped.
30 is integrally raised to open the opening 14 of the container body 12,
The substrate 1 having the coating liquid film formed on its surface is carried out of the container 12.

As a method for providing a relative speed difference between the rotation speed of the substrate 1 and the rotation speed of the rotating plate 16 in the evaporation promoting process, various methods other than the above-described method shown in FIG. 3 can be employed. For example, as shown in FIG. 4, the rotation of the rotating plate 16 is stopped at the time when the shaking-off process is completed.
Is rotated continuously at the same speed from the shaking-off process, or as shown in FIG. 5, when the shaking-off process is completed, the rotating plate 16 is rotated in the opposite direction. From the same speed continuously,
As shown in FIG. 6, when the shaking-off process is completed, the substrate 1
May be reduced to, for example, about 500 rpm, and the rotating plate 16 may be rotated at the same speed continuously from the shaking-off process. In particular, as shown in FIG. 5, the relative speed difference between the rotation speed of the substrate 1 and the rotation speed of the rotating plate 16 becomes larger, and the evaporation of the solvent in the coating liquid is further promoted. .

The method for applying a coating liquid to a substrate according to the present invention is carried out as described above.
It is not limited by the contents of the above embodiment. For example, as shown in FIG. 7, the rotating plate may be rotated in the direction opposite to the rotating direction of the substrate in the diffusion flow process. In this case, the air between the substrate and the rotating plate rotates together with the rotating plate, and the air flows in the circumferential direction opposite to the rotation direction of the substrate, and the air flows in the circumferential direction due to the air flow. The force acts on the coating liquid on the substrate, which promotes the force of the coating liquid to stay on the substrate, and the coating liquid diffuses and flows quickly in the circumferential direction of the substrate, and the entire surface of the substrate is Therefore, it is possible to expect the effect that the coating liquid can be spread in a short time. Further, as shown in FIG. 8, the substrate and the rotating plate are diffused in the shaking-off process without switching between the rotation speeds of the substrate and the rotating plate in the diffusing flow process and the rotating speeds of the substrate and the rotating plate in the shaking-off process. You may make it rotate at the same speed continuously from a flow process. 7 and 8, as in FIGS. 3 to 6, (a) shows the change over time of the rotation speed of the substrate 1, (b) shows the change over time of the rotation speed of the rotating plate 16, and (c) shows the change over time. The change with time of the relative rotation speed of the rotating plate 16 with respect to the substrate 1 is shown. Also, in the evaporation promotion process, the rotating plate 16, the rotating plate driving motor 28 and the mounting holder plate 30 are integrated so that the distance between the substrate and the rotating plate is made larger than in the shake-out process and the diffusion flow process. To evaporate the solvent in the coating liquid. In the shaking-off process, it is necessary to rotate the substrate and the rotating plate in the same direction at the same speed, but the same speed in this specification means substantially the same speed. In addition, as long as the promotion of the evaporation of the solvent in the coating liquid from the substrate surface is suppressed, there may be an allowable speed difference between the rotation speed of the substrate and the rotation speed of the rotating plate. Further, as an apparatus for performing the method of applying a coating liquid to a substrate according to the present invention, the container body 12 is integrally connected to the rotation holding base 10 and is integrally rotated in the above, The container body 12 is not limited to
May be configured to be stationary and the rotation holding table 10 rotates.

[0021]

Since the present invention is constructed and operates as described above, according to the method for applying a coating liquid to a substrate according to the present invention, a coating liquid having a contour profile is finally formed on each substrate. While maintaining good uniformity of film thickness and profile between substrates and maintaining high use efficiency of coating liquid,
It can be formed on the substrate surface.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view showing an example of the configuration of an apparatus for performing a method of applying a coating liquid to a substrate according to the present invention, and showing a schematic configuration of a main part of the coating liquid application apparatus.

FIG. 2 is a partial cross-sectional view showing another example of the configuration of the rotary plate, which is one of the components of the coating liquid application device, different from that shown in FIG.

FIG. 3 is a diagram for explaining an operation of forming a coating film of a coating liquid on the surface of a substrate using the coating liquid coating apparatus shown in FIG. 1; It is a time chart shown.

FIG. 4 is a diagram showing another example of the time chart.

FIG. 5 is a diagram showing still another example of the time chart.

FIG. 6 is a diagram showing still another example of the time chart.

FIG. 7 is a diagram showing still another example of the time chart.

FIG. 8 is a diagram showing still another example of the time chart.

FIG. 9 is a partially enlarged cross-sectional view showing a profile of a coating film of a coating liquid formed on a surface of a substrate.

[Explanation of symbols]

 1 Substrate 10 Rotation holding table 12 Container body 14 Opening on top of container body 16, 36 Rotating plate 18 Suction hole 20 Vacuum suction path 22 Motor for driving substrate rotation 28 Motor for driving rotation plate 32, 38 Coating liquid supply path 40 Ventilation path

Continuation of the front page (56) References JP-A-6-89853 (JP, A) JP-A-5-283331 (JP, A) JP-A-7-51611 (JP, A) JP-A-4-122469 (JP) JP-A-4-302414 (JP, A) JP-A-63-248471 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B05D 1/40 B05C 11/08 G02F 1/13 G03F 7/16 502 H01L 21/027

Claims (7)

(57) [Claims] 1. A diffusion flow process in which a substrate is rotated about a vertical axis in a horizontal plane to spread a coating liquid supplied on the substrate over the entire surface of the substrate, and a coating film of the coating liquid spread over the entire surface of the substrate. In a method of applying a coating liquid to a substrate, which forms a coating liquid coating on the substrate surface through a shaking process of adjusting the thickness of the substrate to a uniform film thickness, a rotating plate is arranged in parallel with the substrate with a slight interval above the substrate And rotating the rotating plate at substantially the same speed as the substrate around the same vertical axis as the rotation axis of the substrate and in the same direction as the rotation direction of the substrate at least in the shaking-off process. Followed by
A method of applying a coating solution to a substrate, comprising: providing a relative speed difference between the rotation speed of the substrate and the rotation speed of the rotating plate to promote a solvent evaporation of the coating solution from the substrate surface. . 2. The method according to claim 1, wherein the rotation of the substrate is stopped in the evaporation promoting step, and the rotating plate is rotated at the same speed continuously from the shaking-off step. 3. The method of applying a coating liquid to a substrate according to claim 1, wherein in the evaporation promoting step, the rotation of the rotating plate is stopped, and the substrate is rotated at the same speed continuously from the shaking-off step. 4. The method according to claim 1, wherein, in the evaporation promoting step, the substrate is rotated at the same speed continuously from the shaking-off step, and the rotating plate is rotated in a direction opposite to the substrate. 5. The application of a coating liquid to a substrate according to claim 1, wherein in the evaporation promoting step, the rotating plate is continuously rotated at the same speed from the shaking off step, and the substrate is rotated at a lower speed than in the shaking off step. Method. 6. The method according to claim 1, wherein a gas is supplied to the surface of the substrate or a closed space surrounded by the rotating plate and the substrate is opened to the atmosphere in the evaporation promotion step. 7. The method of applying a coating liquid to a substrate according to claim 1, wherein the distance between the substrate and the rotating plate is made larger in the evaporation promoting process than in the diffusion flow process and the shaking-off process.