JPH10156273A - Coating liquid-applying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen the range for adjusting a film thickness while keeping the film thickness uniformity even for a large diameter substrate. SOLUTION: In a coating liquid-applying method for applying a coating liquid onto a substrate and forming a coated film of desired film thickness, the application of the coating liquid is started in the state of setting the substrate standstill (timing ts ), and the application is interrupted (timing tE). Then the substrate is rotated at high speed of first number of rotations R3 set at the comparatively high speed (t1 -t3 ), and the substrate is rotated at the second number of rotations R4 lower than the first number of rotations R4 to form a coated film (t4 -t5 ). For adjusting the film thickness, the empty rotation time TH', for rotating at the high speed of first number of rotations R3 is adjusted.

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 photomask, a glass substrate for a liquid crystal display, a substrate for an optical disk (hereinafter simply referred to as a substrate), and the like. Liquid, photoresist liquid, coating liquid such as polyimide resin, etc., is applied to the coating liquid coating method, especially when the substrate is stationary and the coating liquid is supplied to the surface. The present invention relates to a technique for forming a coating film having a thickness.

[0002]

2. Description of the Related Art A conventional coating liquid applying method of this type will be described with reference to FIG. FIG. 3 is a diagram illustrating a main part of the rotary substrate coating apparatus. This apparatus includes a suction-type spin chuck 1 that suction-supports and rotates a substrate W in a substantially horizontal posture.
And a discharge nozzle 30 for supplying a photoresist liquid R as a coating liquid to the surface of the substrate W, substantially above the center of rotation.

[0003] In a conventional method of applying a photoresist liquid using the apparatus configured as described above, for example, as shown in a time chart of FIG. Is formed.

That is, first, the supply of the photoresist liquid R from the discharge nozzle 30 is started at the time point t _{S in} a state where the substrate W is kept stationary without being rotated only by being sucked and supported by the suction-type spin chuck 10. Then, the supply of the photoresist liquid R is continued in this state, and the supply of the photoresist liquid R from the discharge nozzle 30 is stopped at the time point t _E.

After the supply of the photoresist liquid R is completed in this manner, the substrate W is rotated at a low speed R1 (for example, 900 rpm) by a motor (not shown).
The photoresist liquid R is diffused. Thereafter, the number of rotations of the substrate W is increased to a number of rotations R2 (for example, 3,000 rpm) higher than the current number of rotations R1, and the high-speed rotation is maintained for a predetermined period of time. The photoresist liquid R is shaken off to form a photoresist film having a desired thickness on the surface of the substrate W. In order to adjust the thickness of the photoresist film, as shown by a dotted line in FIG. 4, a film having a large thickness is formed mainly by lowering the rotation speed R2, or a thin film is formed by increasing the rotation speed R2. Is formed. The method of supplying the photoresist liquid R in which the supply of the photoresist liquid R is started in a state where the substrate W is stationary and the supply is stopped in this state is also called a “static method”.

[0006]

Recently, there has been a movement to increase the diameter of a semiconductor wafer used in a semiconductor device manufacturing process. Specifically, for example, 300 m, which is even larger than an 8-inch (about 200 mm) diameter substrate
This is a transition to a substrate having a diameter of m. When such a large-diameter substrate is processed by the photoresist liquid coating method according to the conventional example as described above, there are the following problems.

That is, when a large-diameter substrate such as a 300 mm-diameter substrate is processed by controlling the number of rotations of the substrate as shown in the time chart of FIG. 4, the uniformity of the thickness of the photoresist film formed on the surface is greatly increased. The problem is that it decreases. When the photoresist film is formed by rotating the substrate, the turbulence of the peripheral portion is remarkably generated due to the large diameter of the substrate, and therefore, the photoresist liquid supplied near the center of the substrate is exposed to the peripheral edge. The non-uniform volatilization of the solvent that occurs when spreading toward the part is the main factor that significantly reduces the film thickness uniformity.

Therefore, in order to suppress the occurrence of turbulence and ensure the uniformity of the film thickness, the rotation speed of the substrate must be reduced. For example, in the above-described example, the rotation speed R1 is reduced from 900 rpm to 700 rpm in the related art, and the rotation speed R2 is reduced from 3,000 rpm to 1,500 rpm. When the rotation speeds R1 and R2 are reduced as described above, turbulence can be suppressed, and the uniformity of the film thickness can be improved. On the other hand, the amount of the photoresist liquid that can be shaken off by the rotation drive can be reduced. As a result, the thickness of the formed photoresist film is increased, and it is difficult to form a photoresist film having a desired film thickness, particularly, a thin film.

In order to obtain a photoresist film having a desired film thickness while maintaining good film thickness uniformity, for example,
0.1 cp viscosity of the photoresist solution according to the desired film thickness
It has been proposed to fine tune in units. That is, by supplying a photoresist liquid having a low viscosity, a thin film can be formed even at a low rotation speed. However, since the range of the film thickness that can be adjusted by such a method is limited, it is necessary to adjust the film thickness by changing the magnitudes of the rotation speeds R1 and R2, as described above. Since the substrate has a problem of non-uniform film thickness due to turbulence, the rotational speeds R1 and R2 cannot be largely adjusted over a range that was conventionally possible. As a result, there is a problem that the range in which the thickness of the photoresist film can be adjusted while maintaining good film thickness uniformity is narrowed.

In order to realize the technique of adjusting the film thickness by changing the viscosity of the photoresist solution as proposed, it is necessary to add a solvent in an amount corresponding to a desired film thickness to a photoresist solution having a constant viscosity. The necessity of a solvent mixing mechanism for mixing, or the preparation of photoresist solutions of various viscosities in advance, and a photoresist solution switching mechanism that switches the photoresist solution to be supplied according to the film thickness or an increase in the number of nozzles. In any case, there is a problem that the apparatus and its control become complicated, and it is hard to say that this is a practical method for processing a large-diameter substrate.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is possible to increase the range in which the film thickness can be adjusted while maintaining good film thickness uniformity even with a large-diameter substrate. It is an object to provide a liquid coating method.

[0012]

The present invention has the following configuration in order to achieve the above object. That is, the present invention relates to a method of applying a coating liquid to form a coating film having a desired thickness by supplying the coating liquid to a substrate, wherein (a) the coating liquid is provided near the center of the surface of the substrate while the substrate is stationary. Starting and stopping the supply of
(B) rotating the substrate at a relatively high first rotation speed at a high speed; and (c) rotating the substrate at a second rotation speed lower than the first rotation speed to form a coating film. And the steps are performed in that order, and the time for rotating the substrate at a high speed at the first rotation speed is adjusted to adjust the film thickness of the coating film.

[0013]

The operation of the present invention is as follows. The supply of the coating liquid is started near the center of the surface of the substrate while the substrate is stationary, and the supply of the coating liquid is stopped in that state (step (a)). (Step (b)). That is, after the supply of the required amount of the coating liquid is completed, when the substrate is driven to rotate at a high speed at a relatively high first rotation speed, the coating liquid rapidly spreads over the substrate surface due to the strong centrifugal force at the first rotation speed. It covers almost the entire surface in a short time. 1st rotation speed of the substrate is relatively high
When the rotation speed reaches the rotation speed, a turbulent flow is generated in the vicinity of the surface layer at the periphery of the substrate to some extent from that point, and the turbulent flow gradually proceeds toward the rotation center. Due to this turbulent flow, the volatilization of the solvent contained in the coating liquid becomes non-uniform in the substrate surface and the uniformity of the film thickness decreases, but at this point, not only the supply of the coating liquid has already been completed, but also the coating liquid. Is spread over substantially the entire surface of the substrate, so that the coating solution can be uniformly spread over substantially the entire surface of the substrate without being affected by the influence. Thereafter, by rotating the substrate at a second rotation number lower than the first rotation number (step (c)), the coating liquid is dried to form a coating film.

In the above process, if the high-speed rotation time of the substrate is adjusted by the first rotation speed without greatly adjusting the rotation speed, the amount of the application liquid spread over almost the entire surface of the substrate is adjusted. be able to. Therefore, the thickness of the coating liquid covering the entire surface of the substrate can be adjusted.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a rotary substrate coating apparatus to which a coating liquid coating method according to the present invention is applied.

In FIG. 1, reference numeral 10 denotes a suction-type spin chuck, which sucks and supports the substrate W in a substantially horizontal posture. This suction-type spin chuck 10 has a hollow rotating shaft 1.
1 and is driven to rotate by a motor 12. Around the suction-type spin chuck 10, a scattering prevention cup 13 for preventing scattering of a coating liquid such as a photoresist solution is provided. In addition, when the transfer means (not shown) places the unprocessed substrate W on the suction-type spin chuck 10 or receives the processed substrate W from the suction-type spin chuck 10, the lifting means (not shown) is connected to the rotating shaft 11. The suction-type spin chuck 10 is moved above the scattering prevention cup 13 by moving the scattering prevention cup 13 up and down relative to the scattering prevention cup 13 (two-dot chain line in the figure).

The anti-scattering cup 13 includes an upper cup 14 and
It is composed of a circular current plate 15 and a lower cup 17. The upper cup 14 has an opening 14a at an upper portion and an inclined surface 14b for guiding droplets such as a photoresist solution due to rotation of the substrate W downward.

The circular rectifying plate 15 reduces the air flow flowing from the opening 14a and flowing down along the periphery of the substrate W into the lower cup 17.
And the inclined surface 1 of the upper cup 14
The droplets such as the photoresist liquid guided downward by 4b are put on this airflow and guided to the lower cup 17.

A drain port 17a is provided at the bottom of the lower cup 17. The drain port 17a is connected to the drain tank 17
b, and is adapted to collect the photoresist solution and the like after the spin-off. At the bottom of the lower cup 17, a cup exhaust port 17c is further provided.
The cup drain port 17c is connected to an exhaust pump 17d, and sucks and exhausts mist-like photoresist liquid or the like staying in the scattering prevention cup 13 together with air.

Inside the circular rectifying plate 15, there is provided a back rinse nozzle 20 for discharging a photoresist solution wrapping around the back surface of the substrate W and a cleaning solution for removing adhering mist toward the back surface of the substrate W. It is arranged. The back rinse nozzle 20 includes a pipe joint 18 and a supply pipe 18a.
The cleaning liquid is supplied from the cleaning liquid supply unit 18b via the.

Furthermore, the opening 14 of the scattering prevention cup 13
above a and substantially above the center of rotation of the substrate W,
An ejection nozzle 30 for ejecting a photoresist liquid is provided. Also, a coating liquid supply unit (not shown) for supplying a predetermined amount of the photoresist liquid to the discharge nozzle 30, a lifting unit (not shown) for vertically moving the spin chuck 10 and the scattering prevention cup 13 relative to each other, and the motor 12 include a control unit 50. It is configured to be controlled by The control unit 5
Numeral 0 controls the above-described units by a processing program stored in the memory 51 and according to a time chart described later.

An example of the control of the number of revolutions based on the method of the present invention applied to the rotary type substrate coating apparatus configured as described above will be described with reference to FIG. Although omitted in the following time chart, an instruction is added to discharge the cleaning liquid from the back rinse nozzle 20 to wash and remove the photoresist liquid and the mist adhering to the back surface of the substrate W. Is preferred.

First, the substrate W is placed on the suction-type spin chuck 10.
In a state where the substrate W is kept stationary without rotating the motor 12, the photoresist nozzle is started to be supplied from the discharge nozzle 30 at a constant flow rate at the time point t _S. Then, at time t _E, which elapses supply time T _SU from t _S time to stop the supply of the photoresist solution. In other words, the supply completing the required amount of photoresist liquid within the feed time T _SU. In this process, the photoresist liquid forms a circular mass near the center of the surface of the substrate W,
As the liquid volume increases, the diameter increases concentrically.
The period from the time point t _{S to the} time point t _E corresponds to the step (a) in the present invention.

At time t ₁ when the supply of the photoresist solution is stopped at time t _E and a certain time has elapsed, the control unit 50 drives the motor 12 to rotate, and at time t ₂ the rotational speed of the substrate W is relatively high. Control is performed so as to reach the rotation speed R3. When the substrate W is rotated at the relatively high rotation speed R3, the photoresist liquid is applied to the substrate W by a strong centrifugal force.
And spreads from the vicinity of the center toward the peripheral edge to cover almost the entire surface in a short time. Then, holding the rotational driving by the rotation speed R3 to t ₃ time points. The rotation speed R3 corresponds to the first rotation speed in the present invention, and is, for example, 4,000 rpm. Also, from time point t ₁ to t ₃ point corresponds to step (b) in the present invention.

In this process, shortly after the rotation speed of the substrate W reaches the relatively high rotation speed R3, a turbulent flow is generated from the peripheral surface layer of the substrate W, and the substrate W
It progresses toward the center of. When the photoresist solution spreads from the vicinity of the center of the substrate W toward the peripheral edge, if the turbulence is applied, the solvent volatilization in the surface of the substrate W becomes uneven and the film thickness becomes uneven. Problem. However, at the time when the turbulent flow occurs, not only the supply of the required amount of photoresist liquid has already been completed, but also the photoresist liquid has already covered almost the entire surface of the substrate W. Thus, it is possible to prevent the solvent volatilization from becoming non-uniform. Therefore, the photoresist liquid can be spread almost uniformly over substantially the entire surface of the substrate W.

Note that the timing between the supply stop time t _E and the time t ₁ at which the rotation drive is started, the value of the rotation speed R3, the acceleration to the rotation speed R3, and the like are determined by the diameter of the substrate W, the surface state thereof, the photoresist solution, and the like. It is preferable to set in consideration of various conditions such as the viscosity of the substrate W and the supply amount thereof. The photoresist liquid covers almost the entire surface of the substrate W at or immediately after the turbulence due to the rotation speed R3 occurs. It is preferable to set. In other words, the diffusion of the photoresist liquid can be almost completed before or immediately after the formation of a large space for solvent evaporation due to the turbulence caused by the relatively high rotation speed R3 in the vicinity of or above the surface layer of the substrate W. It is preferable to set as follows.

In this manner, the photoresist solution is applied to the substrate W
Even after spreading almost evenly over the entire surface of the
Maintains rotation drive at rotation speed R3 for a time corresponding to film thickness
I do. Specifically, the rotation speed of the substrate W reaches the rotation speed R3.
Time t_TwoIs driven at the rotation speed R3 based on
Time (hereinafter, idle rotation time T)_H’), That is, t _Two
From time t_ThreeIf the time at the time is set according to the desired film thickness
Good. This idle rotation time T_H’Process, the surface of the substrate W
When the photoresist solution is completely spread over the whole
In both cases, the surplus is shaken off to some extent and a film close to the desired film thickness is obtained.
Roughly adjust the thickness. Thus, the relatively high rotational speed R3
If held, it will be affected by turbulence,
As described above, the photoresist liquid has already spread over the entire surface of the substrate W.
Inconsistency due to non-uniform film thickness
Does not occur.

At time t ₃ when the idle rotation time T _H ′ has elapsed, the rotation speed of the substrate W is reduced to a rotation speed R lower than the rotation speed R 3.
4 beginning lowered toward the control unit 50 so as to reach the rotation speed R4 at t ₄ time controls the motor 12. Thus, when the rotation speed of the substrate W is reduced to the rotation speed R4, the turbulence generated near the surface layer of the substrate W can be substantially suppressed by the relatively high rotation speed R3. By holding the rotation number R4 to t ₅ time, the photoresist liquid that is substantially a desired thickness over the entire surface of the substrate W may be dried to form a photoresist film of desired thickness. The above-mentioned rotation speed R4 corresponds to the second rotation speed of the present invention, and is, for example, 3,000 rpm. Also, t
₄ time point t ₅ the time is equivalent to the process of the present invention (c).

As described above, the supply of the photoresist liquid is completed with the substrate W kept still, and the relatively high speed (first
Since the photoresist liquid is spread over almost the entire surface of the substrate W in a short time by the rotation speed R3), the solvent volatilization becomes non-uniform due to the turbulence caused by the relatively high rotation speed R3. Non-uniform film thickness can be prevented. Therefore, a photoresist film having good film thickness uniformity over the entire surface of the substrate W can be formed. Further, in order to adjust the film thickness changes the photoresist liquid amount shaken off by varying the above idling time T _H 'as shown in parentheses in FIG. 2, the photo covering the entire surface of the substrate W What is necessary is just to change the thickness of the resist solution. Therefore, it is possible to change the thickness of the photoresist film without greatly changing the number of rotations according to the film thickness, thereby preventing the occurrence of uneven film thickness due to turbulence even with a large-diameter substrate W. As a result, the range in which the film thickness can be adjusted can be widened as compared with the related art. In particular, when a thin film thickness is required, it is generally necessary to increase the number of revolutions in the conventional method, but according to the method of the present invention, the idling time T
_By increasing _H ′, a thin film can be formed with good quality. In addition, in the present method, films of various thicknesses can be formed with a single type of photoresist solution,
It can be easily applied to existing equipment, and does not complicate the structure of the equipment and its control as in the proposed method of changing the film thickness by adjusting the viscosity of the photoresist solution.

In the time chart of FIG. 2, the supply of the photoresist solution from the stop time t _E (first
A certain period of time is required before the rotation speed of the substrate W is increased to the rotation speed R3), but depending on the temperature difference between the substrate W and the photoresist liquid, uneven coating may occur during that time. Therefore, as shown in parentheses in FIG.
_E ) It is preferable to stop the supply of the photoresist solution at the time point and to control the rotation speed of the substrate W to start increasing to the (first) rotation speed R3.

In the above description, the idle rotation time T _H '
The case where the film thickness is adjusted by adjusting only the thickness has been described as an example, but other parameters that can adjust the film thickness include a (first) rotation speed R3, a (second) rotation speed R4, and the rotation speed thereof. There is a drive time. However, when adjusting these rotation speeds, it is necessary to take into account the occurrence of turbulence, which is a cause of uneven film thickness.

In the above description, the (first) rotation speed R3 is set to 4,000 rpm, and the (second) rotation speed R4 is set to 3,000 rpm. Can be set within a range in which can be maintained satisfactorily. For example, the (first) rotation speed R3 is set within a range of 3,000 to 5,500 rpm, and the (second) rotation speed 4 is 2,000 to 5,000 rpm.
It is preferable to set within the range of 0 rpm. It is preferable to set such a range because if the (first) rotation speed R3 is lower than 3,000 rpm, the effect of shaking off the photoresist liquid becomes small and it becomes difficult to form a thin film. If the rotation speed exceeds 500 rpm, the photoresist liquid shaken off by the high-speed rotation rebounds on the inner surface of the scattering prevention cup to cause inconvenience to adhere to the substrate, or the influence of the turbulence increases, so that the processing is performed within the above upper limit. This is because the film thickness uniformity tends to deteriorate. On the other hand, if the (second) rotation speed R4 is lower than 2,000 rpm, it takes time to dry the photoresist solution, and the throughput decreases. If the rotation speed R4 exceeds 5,000 rpm, the influence of turbulence increases, and in this process, This is because the inconvenience as described for the (first) rotation speed R3 tends to occur.

In the above description, the photoresist liquid is taken as an example, but it goes without saying that the present invention can be applied to a coating liquid such as an SOG liquid or a polyimide resin.

[0034]

As is apparent from the above description, according to the present invention, the supply of the coating liquid to the substrate is completed before the high-speed rotation at the first rotation speed, and then the high-speed rotation is performed. The coating liquid can be spread over almost the entire surface of the substrate in a short time. Therefore, the coating liquid can be spread over almost the entire surface of the substrate before being affected by the turbulence caused by the relatively high-speed first rotation speed,
The volatilization of the solvent can be made uniform within the substrate surface. Furthermore, since the amount of the application liquid to be shaken off can be adjusted by adjusting the rotation driving time at the first rotation number without largely adjusting the rotation number, the film thickness of the application liquid can be adjusted. As a result, it is possible to prevent nonuniform film thickness due to turbulence which is particularly likely to occur on a large-diameter substrate, and to broaden the range in which the film thickness can be adjusted while maintaining good film thickness uniformity as compared with the related art. it can. For this reason, a thin coating film can be formed with high quality, and it is possible to cope with the manufacture of semiconductor devices having strict design rules. In addition, since it is not necessary to change the viscosity of the coating liquid according to the film thickness, it is possible to form a uniform coating film on a large-diameter substrate simply by applying this coating liquid coating method to a conventional apparatus. It can be used effectively.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic configuration of a rotary substrate coating apparatus to which the method of the present invention is applied.

FIG. 2 is a time chart illustrating an example of a method of applying a photoresist liquid.

FIG. 3 is a view showing a main part of a rotary substrate coating apparatus according to a conventional example.

FIG. 4 is a time chart showing a coating liquid application method according to a conventional example.

[Explanation of symbols]

W: substrate 10: suction-type spin chuck 12: motor 13: scattering prevention cup 30: discharge nozzle 50: control unit 51: memory R3: rotation speed (first rotation speed) R4: rotation speed (second rotation speed) T _H '... idling time T _SU ... supply time

Claims (1)

[Claims] 1. A method for applying a coating liquid to a substrate to form a coating film having a desired thickness by supplying the coating liquid to the substrate, the method comprising: (a) applying the coating liquid near the center of the surface of the substrate while the substrate is stationary; Starting the supply and stopping the supply; (b) rotating the substrate at a relatively high speed at a first speed; and (c) lowering the substrate at a speed lower than the first speed. Rotating the substrate at the second rotational speed to form a coating film in that order, and adjusting the time for rotating the substrate at the first rotational speed at a high speed,
A method for applying a coating liquid, wherein the thickness of the coating film is adjusted.