JPH09298149A - Coating film forming method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a coating film at a high film thickness accuracy, without subjecting the thickness to the influence of the pressure change on the thickness of the film of a coating liq. formed on a work. SOLUTION: A wafer W is held with a spin chuck 3 so as to be rotatable by a motor 1. A nozzle 5 for dripping a resist liq. on the wafer W faces the wafer W. The resist liq. L dropped from the nozzle 5 is diffused on the entire surface of the wafer W by rotating the wafer at specified diffusion rotation speed to form a coating film. The atmospheric pressure of the coating atmosphere is detected by a barometer 7 to control the diffusion rotation speed according to the detected value. Thus a coating film of a uniform thickness on the surface of the wafer, if the atmospheric pressure changes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming a coating film by applying a liquid to the surface of an object to be coated, and, for example, a semiconductor wafer, a magnetic disk, a laser disk or the like is used as the object to be coated and a coating film is formed on the surface thereof. Related to forming technology.

[0002]

2. Description of the Related Art As a spin coating apparatus for forming a thin film of photoresist on the surface of a semiconductor wafer (hereinafter referred to as a wafer), there is, for example, the one shown in JP-A-63-76431. This spin coating device has a spin chuck that is rotated by a motor via a drive shaft to hold a wafer, and a coating cup that covers the spin chuck, and drops a resist solution onto a surface of the wafer from a nozzle. The wafer is stopped at the time of dropping, or 200 to 50
Rotate at a low speed of about 0 rpm, and after the dropping is completed, the motor is rotated at a constant diffusion rotation speed within a range of about 3000 to 5000 rpm by a motor to diffuse the resist solution on the surface of the wafer to form a resist film. I have to. Further, as a technique for removing the photoresist film on the peripheral portion of the wafer with a photoresist solvent, there is one disclosed in JP-A-2-115066.

[0003]

The miniaturization of semiconductor integrated circuit devices is advancing year by year, and the demand for processing dimensional accuracy is increasing accordingly. One of the factors that reduce the processing dimensional accuracy is the change in the film thickness of the photoresist used for patterning. When the change in film thickness occurs, when the change is large, a dimensional shift due to the bulk effect occurs, and when the change is small, a dimensional balance change due to the standing wave effect occurs. The electrical characteristics may be deteriorated and the product yield may be reduced.

As a factor causing the film thickness change, the influence of the temperature change is considered. As a technique for preventing the change in the film thickness of the photoresist from the temperature side, for example, by controlling the temperature of the resist solution or by controlling the temperature of the coating section with a temperature control cover so that the temperature of the coating section does not change, A technique for controlling the film thickness by keeping the constant is considered.

However, even if the temperature of the resist solution is controlled to keep the film thickness constant, variations in the film thickness may occur and the film thickness of the resist solution may not be set to a desired value. It was

Therefore, the present inventor speculates that the change in atmospheric pressure is the cause of the change in film thickness,
Various experiments were performed. The following is a technique studied by the present inventors, and the outline is as follows.

That is, since the resist solution contains a solvent and the vapor pressure of the solvent changes depending on the atmospheric pressure, it is considered that the thickness of the resist film changes, and the solvent is injected into the coating cup. Therefore, it was studied to keep the solvent atmosphere concentration constant. However, it has been found that even if the solvent is injected into the coating cup to keep the solvent atmosphere concentration constant, the change in the film thickness cannot be made constant.

It is an object of the present invention to form a film thickness of a coating liquid such as a resist liquid to be coated on a coating product such as a semiconductor wafer with high accuracy without being affected by a change in atmospheric pressure. To do so.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0010]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, according to the present invention, the liquid to be coated is dropped on the surface of the liquid to be coated, and then the liquid to be coated is rotated at the diffusion rotation speed to diffuse the liquid to be coated on the surface of the liquid to be coated. In this way, by making the diffusion rotation speed different according to the change in atmospheric pressure, it is possible to set the thickness of the coating film formed by the liquid to be coated constant even if the atmospheric pressure changes.

To form a coating film on the surface of an object to be coated, first, the liquid to be coated is dropped. At this time, the object to be coated may be stopped or rotated at a low speed. When the dropping is completed, the object to be coated is rotated at a constant diffusion rotation speed in order to diffuse the liquid to be coated on the surface of the object to be coated.

It has been found that there is a constant relationship between this number of revolutions and the film thickness of the liquid to be coated, and further that even at the same number of revolutions, there is a constant relationship between the atmospheric pressure and the film thickness. By correcting the diffusion rotation speed based on the atmospheric pressure value, it is possible to form a coating film having a predetermined film thickness with high accuracy without being affected by the atmospheric pressure.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing a coating film forming apparatus according to an embodiment of the present invention, which is also called a spin coater. A spin chuck 3, which is also called a spinner, is attached to a rotation shaft 2 of the motor 1, and a wafer W, which is an object to be coated, is sucked and held by the spin chuck 3. As a result, the wafer W is rotationally driven by the drive of the motor 1. This apparatus has a coating cup that covers the spin chuck 3, that is, a coating section cover 4, and a nozzle 5 faces the wafer W from an opening formed at the upper end of the coating section cover 4, The resist solution L is applied.

A temperature control cup 6 is arranged outside the coating section cover 4 so that the temperature in the coating atmosphere inside the temperature control cup 6 is kept constant. The inside of the temperature control cup 6 is not completely shut off from the outside, and the outside air flows into the temperature control cup 6 to have a pressure substantially similar to the atmospheric pressure. In order to detect this pressure, that is, atmospheric pressure, the temperature control cup 6 is provided with a barometer 7. The value of the atmospheric pressure detected by the barometer 7 is sent to the control unit 8, and the rotation speed of the motor 1 is set based on the atmospheric pressure.

FIG. 2 is a time chart showing changes in the number of rotations of the wafer W when the resist solution L is applied to one wafer W. In the step of applying the resist solution L, the wafer W is not rotated. Under the stopped state or the state where the resist solution L is rotated at a low speed, a dropping step A for dropping the resist solution L from the nozzle 5 is performed, and the wafer W is rotated at a predetermined diffusion rotation speed to remove the resist solution L from the wafer W. And a diffusion step B for diffusing on the surface.

FIG. 3 is a graph showing the change in atmospheric pressure during 35 hours at a certain time. Within this time, after the atmospheric pressure decreased from 977 mb to 962 mb, 980 mb.
Since the resist coating is not performed in a completely sealed container, this pressure acts on the resist coating atmosphere almost as it is.

FIGS. 4A and 4B show data obtained by measuring the relationship between atmospheric pressure and resist film thickness by rotating the wafer W with different types of resist solutions L at the same diffusion rotation speed. It is a graph which shows.

Further, FIGS. 5A and 5B show wafers under different rotation speeds from those described above for resist liquids different in kind from each other and different in kind from each other. It is a graph which shows data when W is rotated and the relation between atmospheric pressure and resist film thickness is measured. From these experimental data shown in FIGS. 4 and 5, under the same diffusion rotational speed of the wafer W, the resist film thickness becomes thinner as the atmospheric pressure becomes higher, and conversely, when the atmospheric pressure becomes lower, the resist film thickness becomes smaller. It was found to be thin, and the amount of change depends on the type of resist solution. From this experimental data, it is possible to obtain a characteristic formula showing the relationship between the atmospheric pressure and the resist film thickness.

FIG. 6 is a graph showing the relationship between the rotation speed and the resist film thickness when the diffusion rotation speed of the wafer W is changed under the same atmospheric pressure. From the experimental data shown in FIG. 6, it was found that, under the same atmospheric pressure, the resist film thickness becomes smaller as the diffusion speed becomes larger. It is possible to obtain a characteristic expression indicating the relationship of The diffusion rotation speed and the amount of change in the resist film thickness also differ depending on the type of the resist solution.

From such experimental data, if the diffusion rotation speed of the wafer W is changed based on the atmospheric pressure at the time of applying the resist solution, the film thickness of the resist solution L applied to the wafer W can be changed to a desired film. It turned out that the thickness can be set.

Therefore, when there are a plurality of types of resist liquid applied to the wafer W, the relationship between the rotation speed of the wafer W and the resist film thickness according to the atmospheric pressure is found by experiments for each resist liquid. If the data is stored as a data table 10 in the memory of the control unit 8 shown in FIG. 1, the operator operates the input unit 11 composed of an operation board or the like to select the type of resist solution and the set resist film thickness. By inputting the value of, the diffusion rotation speed of the wafer W is controlled to a desired rotation speed based on the atmospheric pressure detected by the barometer 7.

Further, instead of storing the experimental data in the memory as a data table, the above-mentioned characteristic formula is stored in the memory, and the characteristic formula is read to set the coating film forming rotation speed of the wafer W to atmospheric pressure. You may make it control based on this.

Next, the procedure for forming a coating film on the wafer W by the coating film forming apparatus shown in the drawing will be described with reference to the time chart shown in FIG. 2 and the flowchart shown in FIG.

First, under the condition that the wafer W is set on the spin chuck 3 and the nozzle 5 is arranged so as to face the wafer W and the coating film forming operation can be started, a start command is issued in step S1. Then, in step S2, the resist liquid is dropped from the nozzle 5 onto the center of rotation of the wafer W. Next, in step S3, the spin chuck 3 is rotated at a low speed to lightly spread the resist solution. The low speed rotation is performed for about 1 to 2 seconds, and if the end of the dropping step A is determined in step S8, the diffusion step is performed. Then, the spin chuck 3 is rotated at a low speed for about 1 to 2 seconds to lightly spread the resist solution. In this way, the dropping step A is completed. In addition, in the dropping step A, the resist solution may be dropped from the beginning in a state of being rotated at a low speed.

Thereafter, in step S9, the spin chuck 3 is rotated at a diffusion rotation speed higher than that of the dropping step A, and the process proceeds to the diffusion step B. This diffusion rotation is performed for 10 to 20 seconds to diffuse the resist solution over the entire wafer W.
FIG. 2 shows a coating operation including the dropping step A and the diffusion step B. It should be noted that after the diffusion step B is completed, the peripheral edge of the wafer W may be subjected to the edge cutting process of the resist liquid.

In step S4, the barometer 7 turns the temperature control cup 6
The atmospheric pressure of the resist coating space inside is detected, and this detection signal is sent to the controller 8. The control unit 8 reads the data stored in the memory based on the detected atmospheric pressure value, and calculates the optimum diffusion rotational speed for the atmospheric pressure state in step S7. In this way, the optimum coating film forming rotation speed is obtained each time the resist solution is applied, and the rotation speed of the motor 1 is controlled by the rotation speed. As a result, the number of rotations of the wafer W in the diffusion step B is set to a desired number of rotations, and the coating film of the resist solution can be formed to have a desired film thickness without receiving a change in atmospheric pressure.

In the illustrated case, the barometer 7 is arranged inside the temperature control cup 6, but the pressure in the temperature control cup 6 corresponds to almost atmospheric pressure. You may make it arrange | position on the outer side of 6. When a large number of coating film forming apparatuses are used at the same time, the atmospheric pressure may be intensively measured at one place and the signal may be transmitted to each coating film forming apparatus. When measuring the atmospheric pressure at a location away from the coating film forming device, if the location and the pressure in the temperature control cup of the coating film forming device are different, add a correction value to the measured value. Is also good.

As described above, the spin chuck 3, that is, the wafer W, is corrected in diffusion rotational speed according to the change in atmospheric pressure, and is rotated at the corrected constant rotational speed. Can be maintained at a constant value with high accuracy. This correction may be performed each time one wafer W is processed, or may be performed each time a predetermined number of wafers are processed.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, in the illustrated case, the case where the resist liquid is used as the liquid to be coated and is applied to the wafer W has been described. However, for example, an inorganic liquid to be coated such as SOG (Spin-on-Glass). The same can be applied to a spin coater for applying a.

In the above description, the case where the invention made by the present inventor is mainly applied to the formation of a photoresist film of a semiconductor wafer, which is the field of application thereof, has been described.
The present invention is not limited to this, and can be applied, for example, to a case where a magnetic disk, a laser disk, or the like is used as an object to be coated and a coating film is formed on the surface of the object.

[0034]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

(1) Since the film thickness of the coating liquid applied to the coating object is not affected by the change in atmospheric pressure, the film thickness can be formed to a desired thickness with high accuracy.

(2) Since the film thickness can be formed with a uniform thickness over the entire surface of the object to be coated, a fine circuit pattern of the semiconductor integrated circuit device can be processed with high dimensional accuracy.

(3) The yield of products such as semiconductor integrated circuit devices can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic structure of a coating film forming apparatus according to an embodiment of the present invention.

FIG. 2 is a time chart showing a coating film forming step.

FIG. 3 is a graph showing changes in atmospheric pressure.

4A and 4B are graphs showing the relationship between atmospheric pressure and resist film thickness when resist liquids of different types are applied to a wafer.

5A and 5B are graphs showing the relationship between atmospheric pressure and resist film thickness when resist liquids of different types are applied to a wafer.

FIG. 6 is a graph showing the relationship between the wafer rotation speed and the resist film thickness in the diffusion step.

FIG. 7 is a flowchart showing an operation procedure of the coating film forming apparatus.

[Explanation of symbols]

 1 Motor 2 Rotating Shaft 3 Spin Chuck 4 Coating Part Cover 5 Nozzle 6 Temperature Control Cup 7 Barometer 8 Control Part 10 Data Table 11 Input Part L Resist Liquid W Wafer

Claims (4)

[Claims] 1. A method for forming a coating film, wherein a coating liquid dropped on the surface of a coating object is diffused by rotating the coating object to form a coating film on the surface of the coating object. A dropping step of dropping the coating liquid onto the surface of the coating object, and a diffusion step of rotating the coating object at a predetermined diffusion rotation speed to diffuse the coating liquid on the surface of the coating object. And a method for forming a coating film, characterized in that the atmospheric pressure is measured, and the diffusion rotational speed is varied depending on the atmospheric pressure. 2. The method for forming a coating film according to claim 1, wherein when the atmospheric pressure is high, the rotational speed is different so that the rotational speed of the object to be coated is lower than when the atmospheric pressure is low. And a method for forming a coating film. 3. A coating film forming apparatus for forming a coating film on the surface of an object to be coated by diffusing the object liquid dropped on the surface of the object to be coated by rotating the object to be coated. A chuck for holding the object to be coated, rotating means for rotating the object to be coated, a nozzle for supplying the liquid to be coated onto the surface of the object to be coated, a barometer for measuring atmospheric pressure, Control means for varying the diffusion rotation speed for diffusing the coating liquid dropped on the surface of the coating object to the surface of the coating object based on the value of the atmospheric pressure detected by the barometer. An apparatus for forming a coating film. 4. The coating film forming apparatus according to claim 3, wherein the control means uses a relationship between the atmospheric pressure and the diffusion rotation speed as a data table for a plurality of types of liquids to be coated, or a characteristic. Having a memory for storing as a formula, reading the data in the data table according to the type of the coating liquid designated by the input means, or calculating the characteristic formula and sending a control signal to the rotating means, A coating film forming apparatus, wherein the object to be coated is rotated at a predetermined diffusion rotation speed.