JPH03272130A - Spin coating process - Google Patents

Abstract

PURPOSE:To equalize the film thickness by a method wherein a substrate is spinned in a vacuum vessel so as to dry up and solidify the coating solution. CONSTITUTION:An upper cup 14 is opened to mount a glass substrate 11 on a specimen base 13; liquid resist is dripped on the central part of the substrate 11 and then the cup 14 is closed; the substrate 11 is spinned at 300rpm for 5 minutes by a motor 12 to spread the resist over the whole surface; next the pump 12 is accelerated at 1000rpm; and after 10sec. exhaust step is started by a pump 24 to attain to the vacuum degree of 50Hg after 20sec. While preserving the vacuum degree using a pressure regulating valve 23, the spinning step is continued for 30sec. to be further prebaked at 90 deg. for 30 minutes in an oven. Through these procedures, coating solution in fluid state can be dried up and solidified in a vacuum vessel so that the phenomena of friction between air and the surface of coating solution as well as the sweeping wind may be eased thereby enabling the even distribution of film thickness to be realized while the drying and solidifying time are cut down.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a one-spin coating method in which a coating liquid is applied while rotating a substrate. For example, it is used in the semiconductor manufacturing process, and is particularly effective for coating a liquid resist with a uniform thickness on a square substrate.

[Conventional technology] Currently, electronic components such as semiconductors, liquid crystal displays, and contact image sensors are manufactured using photolithography technology. It determines the manufacturing yield, electrical characteristics, reliability, manufacturing cost, etc. of

In the above microfabrication process, a resist film is formed on a silicon wafer or a glass substrate to which an inorganic thin film is attached, and a circuit pattern is transferred onto the film by exposing the circuit pattern to the pattern formed on the resist film. Accordingly, silicon and inorganic thin films are etched using acids. This faII
Electronic parts are completed by repeating the llII process several times.

Conventionally, in this microfabrication process, a spinner device as shown in the cross-sectional configuration diagram of FIG. 3 has been used to form a resist film on a substrate such as silicon. This device is equipped with a sample stage (3) that rotates a substrate (1) on which a resist film is to be formed by a motor (2), and a separate system (not shown) for dropping liquid resist onto the substrate (1). An apparatus board (1) consisting of an upper cup (4) and a lower cup (5) equipped with a duct (6) for exhausting solvent vapor etc. in the spinner cup is placed on the sample stage (3). After dropping the liquid resist in the center, close the spinner upper cup (4) and rotate the motor (2), the sample stage (3) will rotate and the substrate (1) will also rotate and sit on it. The liquid resist spreads over the entire surface, and as the rotation time passes, the solvent evaporates and a resist film is formed.

As described above, when coating with a spinner, the rotation of the substrate (1) causes the film thickness to vary due to friction between the air in the cup and the resist surface. Particularly in the case of a square board, the corners of the board cut the wind and have a noticeable effect. Figures 4 (A) and (B) show commercially available resist OF'PR-800 (15 cp) (manufactured by Tokyo Ohka Kogyo Co., Ltd.) at a spinner rotation speed of 1000 rpm.
FIG. 3 is a characteristic diagram showing the film thickness distribution within the substrate when the film is coated at 90° C. and prebaked for 30 minutes. The vertical axis represents the average film thickness of the substrate.
The horizontal axis shows the relative film thickness when the distance is 4th L.
l(A) shows the film thickness distribution of a round substrate of 125Nφ, and the fourth
Figure (B) shows the film thickness distribution of a 125 x 125 tm square Galanu substrate. The former is 20. The film thickness becomes approximately 5q6 thinner between , (the part indicated by a in the figure), and the latter becomes a uniform film thickness inside the inscribed circle of the square substrate, but outside of it, there is a trough (in the figure) along with the wind flow. (shown above), and the film thickness becomes thicker near the edge due to surface tension.The rotation of the spinner cuts the wind at the edge of the substrate, making the resist film thickness uneven, making it difficult for electronic components to Only the flat central part can be used for manufacturing, and much of it is wasted. In particular, when a square substrate is used, the flat portion becomes narrow and there are many unusable areas around the substrate.

On the other hand, in order to obtain a coating film with a uniform thickness,
82975Jij-publication and JP-A-60-245225
In Japanese Patent No. 3, a device has been proposed which evacuates the inside of a coating treatment tank and sucks up the photoresist spray generated during high speed rotation to prevent redeposition, splashing, etc.

However, the exhaust means used for these are similar to ventilation fans, and the wind is rotating.

Therefore, when the air is exhausted, wind is generated instead, forming streak-like waveforms on the coating film.

[Problem to be solved by the invention]

In the conventional spin coating method, a resist film is formed by evaporating the coating liquid, such as the solvent of the photoresist, while rotating as described above, so the film thickness fluctuates due to friction between the air and the resist surface, resulting in non-uniformity. There was a problem. This was especially noticeable in the case of a square board because the corners of the board cut the wind.

This invention was made to solve the above-mentioned problems, and an object thereof is to provide a spin coating method that can form a coating film of uniform thickness.

[Means to solve the problem]

In the spin coating method of the present invention, the coating solution is spread over the entire surface by rotating the substrate, and then the inside of the tank housing the substrate is evacuated, and the coating solution in a fluid state is dried and fixed while rotating the substrate. This method forms a coating film.

[Effect]

In this invention, since the substrate is rotated in a vacuum to evaporate the solvent and form a coating film, it is possible to reduce the friction between the air and the resist film and the phenomenon of wind cutting, and to improve the uneven film thickness caused by this. [Embodiment] This invention provides a coating solution, such as Ii, on a substrate using a spinner.
When applying liquid Nuto, place the substrate on the sample stage,
After dropping the resist solution on it, or rotating the spinner while dropping it, the resist solution spreads over the entire surface of the substrate.
The inside of the cup, which is the tank that houses the substrate, is rotated while creating a vacuum within the range where the resist solvent does not boil (above the vapor pressure of the solvent) to reduce the wind effect on the edge of the substrate, evaporate the solvent, and turn the coating liquid into a fluid state. is dried and fixed to obtain a coating film of uniform thickness.

If the vacuum is set to a high degree and the pressure is lower than the vapor pressure of the resist solvent, bubbles will occur within the resist film, making it impossible to obtain a flat film. It is effective even if the degree of vacuum is several 6 as Hg, but in practical terms it is several tens of seconds.
lug is suitable.

If the solvent is completely removed from the resist film coated in vacuum as described above, pattern exposure can be performed immediately without pre-baking, but if there is residual solvent, pre-baking is performed before pattern exposure.

Hereinafter, this invention will be specifically explained based on Examples.

FIG. 1 is a sectional view showing an example of a spinner device according to the present invention. The substrate (1) is connected to a sample stage (13) that is rotated by a motor (12), and a magnetic seal is applied to the part (22) where the rotating shaft of the motor (12) passes through the lower cup to maintain airtightness. . Further, a vacuum is maintained between the upper cup (14) and the lower cup (15) by an O-ring (21). The exhaust pipe (16) has a pressure adjustment valve (
23) is provided and connected to the rotary pump (24),
It has a structure that can create a vacuum inside the spinner cup.

Next, the operation will be explained.

An example of applying resist using this apparatus is shown below.

Open the upper cup (14) and measure 125 x 1.25 ra
An m square glass substrate (11) is placed on the sample stage (13). Next, liquid resist 0FPR-800 (15c
) manufactured by Tokyo Ohka Kogyo Co., Ltd., onto the center of the substrate, close the upper cup, and move the substrate (11) by 300 mm using the motor (12).
rpm for 5 seconds to spread the liquid resist over the entire surface. Immediately increase the rotation speed to 1.000 rpm and
Evacuation was started by the rotary pump (24) after 0 seconds, and a vacuum level of 50 mHg was reached after 20 seconds. After rotating for an additional 30 seconds while maintaining this degree of vacuum with the pressure adjustment valve (23), brebake was performed in the open for an additional 90,030 minutes. The film thickness distribution at this time is shown in the characteristic diagram of FIG.

The vertical axis represents relative film thickness, and the horizontal axis represents distance.

When compared with the film thickness distribution coated by the conventional technique (FIG. 4(B)), it can be seen that there is less influence of wind at the corners of the substrate, and a flat coating film is obtained around the substrate.

In the past, by drying and fixing the coating liquid in a fluid state in a vacuum chamber, it was possible to reduce the friction between the air and the coating liquid surface and the wind blowing of the substrate, and to achieve a uniform film thickness distribution. The time required for fixing can be shortened, and the rotation speed of the substrate can also be kept low. Reducing the speed of substrate rotation is particularly advantageous for large substrates, and the motor required for rotation can also be made smaller, increasing safety.

〔Effect of the invention〕

As described above, according to the present invention, in spin coating, after the coating liquid is spread over the entire surface by rotating the substrate, the inside of the tank containing the substrate is evacuated, and while the substrate is being rotated, the coating solution is spread over the entire surface. By drying and fixing the coating liquid in a fluid state, it is possible to reduce friction between the air in the tank and the surface of the coating liquid and the wind blowing phenomenon of the substrate, and to reduce unevenness in film thickness caused by this, resulting in a uniform film thickness. This has the effect of providing a coating film.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional configuration diagram showing an example of a spinner device according to the present invention, Fig. 2 is a characteristic diagram showing the film thickness distribution of a coating film by the spin distribution method of an embodiment of the invention, and Fig. 3 is a conventional Cross-sectional configuration diagram showing the spinner device of FIG. 4 (A) (B)
2A and 2B are characteristic diagrams showing film thickness distributions of coating films obtained by conventional methods. In the figure, (11) is the board, (12) is the motor, (1
4) is an upper cup, (15) is a lower cup, (21) is a vacuum O-ring, (22) is a magnetic seal, and (23) is a pressure adjustment valve (24) and a halo refill pump. Here, an upper cup/Ql cup (14) and a lower cup (15) form a tank. In the figures, the same symbols indicate the same or equivalent parts.

Claims (1)

[Claims] In a method of spin-coating a coating liquid onto a substrate, the coating liquid is spread over the entire surface by rotating the substrate, and then the inside of a tank containing the substrate is evacuated, and the coating liquid is applied in a fluid state while rotating the substrate. A spin coating method characterized by drying and fixing the coating solution.