JPS61280618A - Spin coating and spin coating device - Google Patents

Abstract

PURPOSE:To enable to uniformize the film thickness of an applied film to be formed on the substrate by a method wherein the atmosphere in the interior of the case is filled with the volatile component of volatile solution and the volatilization of the volatile solution is positively suppressed through the time of spin coating of the volatile solution onto the substrate. CONSTITUTION:A substrate 18 is installed on a turning table 14, volatile solution, such as resist liquid, is dripped on the center part of the substrate 18 and when the substrate 18 is made to rotate along with the turning table 14 at the prescribed speed, the volatile solution is diffused toward the outer peripheral part of the substrate 18 by a centrifugal force and is applied on the substrate 18. At this time, by sealing the interior of a case 13 with a cover 19, the interior of the case 13 is turned into an atmosphere to be filled saturated with the volatile component of the volatile solution. As it is suppressed that a film is formed of the volatile solution in the atmosphere to be filled or saturated with the volatile component, the volatile solution is sufficiently diffusion-applied on the substrate and reaches an equilibrium film thickness. after the volatile solution reaches an equilibrium film thickness, the cover 19 is removed and the volatile component is made to volatilize, thereby enabling to obtain the applied film having a uniform film thickness on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a spin coating method and a spin coating device in which a volatile solution is dropped onto a substrate and the substrate is rotated to spread and coat the volatile solution.

"Prior Art and its Problems" For example, in a mask process or a wafer process, a spin coating method is employed to apply a resist solution such as a photoresist to a substrate such as a mask blank or a wafer. When applying a resist solution, uniform film thickness is a necessary condition for improving pattern dimensions and patterning fidelity. The thickness of the resist film formed by the spin coating method is determined by the rotation speed.

It is influenced by various factors such as the rotation start-up speed, rotation time, the concentration and viscosity of the resist solution, the volatility of the solvent (thinner), and the wettability of the resist solution and the substrate surface. Furthermore, in order to make the film thickness uniform within the plane of the substrate, the following conditions must be qualitatively satisfied. In other words, the resist solution dropped onto the substrate surface spreads within the surface due to centrifugal force according to a predetermined rotational speed, and reaches an equilibrium film thickness determined by the above factors. However, if the resist solution significantly evaporates before reaching this equilibrium film thickness, At that point, the film formation is completed, and the film thickness is distributed from the center of the substrate to the periphery. This problem becomes more noticeable as the rotation speed increases, and as the resist solution becomes more volatile and has a higher viscosity. sexuality is impaired. Furthermore, if the substrate is rectangular like a mask substrate, the airflow at some of its corners will be disturbed, so volatilization will be considerably accelerated, and the film thickness at some of the corners will become abnormally thick. If the film thickness becomes non-uniform as described above, variations in pattern dimensions will occur within the plane, and patterning fidelity cannot be guaranteed in a photolithography process using a contact exposure method.

``Object of the Invention'' In view of the problems of the prior art described above, the object of the present invention is to provide a spin coating method and a spin coating device that can coat a volatile solution such as a resist solution to form a film with a uniform thickness. It is about providing.

"Structure of the Invention" The present invention has been made with an eye to the fact that the film thickness can be made uniform by actively suppressing the volatilization of a volatile solution during spin coating.

That is, in the spin coating method according to the present invention, a volatile solution is dropped onto a base material, and when the base material is rotated to spread and coat the volatile solution, the atmosphere is filled with volatile components of the volatile solution. It is characterized by

Further, the spin coating device according to the present invention is characterized in that a mechanism for supporting and rotating the base material is provided in a predetermined case, and a lid body is provided for sealing the case.

Furthermore, another spin coating device according to the present invention is provided with a mechanism for supporting and rotating a base material in a predetermined case, and a supply means for filling the case with volatile components of a volatile solution. It is characterized by the presence of

Therefore, in the present invention, during spin coating of a volatile solution,
Since the atmosphere is filled or saturated with the volatile components of the volatile solution, it is possible to suppress the volatile solution from forming a film until the volatile solution is sufficiently diffused and applied to reach an equilibrium film thickness. Then, when the volatile solution reaches an equilibrium film thickness, the atmosphere filled with volatile components is removed and film formation is performed, whereby a coating film having a uniform film thickness can be obtained.

Embodiment of the Invention FIG. 1 shows an embodiment of a spin coating apparatus according to the present invention. This spin coating device 11 includes a turntable 14 in a case 13 installed on a base 12. The turntable 14 is configured to rotate at a predetermined speed by a rotating shaft 1B that is interlocked with a motor 15 installed within the base 12. A plurality of grooves 17 are formed on the top surface of the turntable 14, and a substrate 1 such as a mask blank is formed.
When the substrate 8 is installed, the substrate 18 is vacuum chucked.

In the present invention, a lid 21 for sealing the inside of the case 13 is detachably attached to the upper opening of the case 13.

Therefore, in this spin coating device 11, the substrate 1
8 is placed on the turntable 14, a volatile solution such as a resist solution is dropped onto the center of the substrate 18, and when the substrate 18 is rotated together with the turntable 14 at a predetermined speed, the volatile solution is transferred to the substrate 18 by centrifugal force. It is spread and applied towards the outer periphery of the area. At this time, by sealing the inside of the case 13 with the lid 18, the inside of the case 13 can be made into an atmosphere filled with or saturated with volatile components of the volatile solution. In this way, in an atmosphere full or saturated with volatile components, the volatile solution is inhibited from forming a film, so that the volatile solution is sufficiently diffused and coated to reach an equilibrium film thickness. and.

After the volatile solution reaches the equilibrium film thickness, the lid 19 is removed and the volatile components are volatilized, thereby making it possible to obtain a coating film with a uniform film thickness.

In the above embodiment, a vaporizer 20 for the volatile components (solvent) of the volatile solution may be provided to supply the volatile components into the tennis ball 13 through the pipe 21. In order to release the atmosphere, a suction device 22 is provided, and a pipe 23 is passed through the case 13.
Volatile components may be removed by suction from within.

Experimental example: PMMA was coated using a spin coating device as shown in Figure 1.
A positive type EB resist of the same type was used for spin coating on a mask blank. The solvent for this resist is ECA (ethyl cellosolve acetate), and the viscosity of the resist liquid is 20
0 cp, belongs to the class of volatile high viscosity solutions,
It is one of the resists for which it is difficult to obtain a uniform in-plane film thickness by high-speed rotational coating. A mask blank having a size of 5 inches square was used, and after dropping the above resist solution onto the mask blank, it was rotated at 4000 rpm to spread and apply the resist solution. Then, there are cases in which the atmosphere is saturated with ECA vapor and spin coating is carried out (hereinafter referred to as a closed system), and cases in which spin coating is carried out in an open atmosphere (
(hereinafter referred to as an open system), the in-plane film thickness distribution of the mask blank was measured. The results are shown in FIG. 2. In the figure, .

As is clear from Figure 2, the in-plane film thickness uniformity in the closed system is better than that in the open system, and
In the plane along the 3111 radius, the film thickness is 3800 ±
There were 20 people. In addition, in the sample coated in an open system, the area with uniform film thickness was smaller than 4.5″φ, and the film thickness became thicker toward the periphery, and especially in some corners, streak-like surface irregularities occurred. The film thickness was also 2 to 3 times that of the center.

Furthermore, in open systems, unevenness due to, for example, concentration differences in the resist solution is likely to occur, and the rate of occurrence of in-plane defects tends to be higher than in closed systems.

Note that the above results were similar not only to PMMA-based positive EB resists but also to other commonly used EB resists and photoresists. As described above, the effect of the atmosphere on the in-plane uniformity of the film thickness was extremely large.

"Effects of the Invention" As explained above, according to the wood invention, during spin coating,
Since the atmosphere is filled with volatile components of the volatile solution, film formation is suppressed until the volatile solution is sufficiently diffused and coated onto the substrate to reach an equilibrium film thickness. After the volatile solution reaches the equilibrium film thickness in this way, by opening the atmosphere and forming the film, it is possible to obtain a coating film with a uniform film thickness distribution within one surface. It is suitable for applying resist liquid where thickness uniformity has an important effect on patterning accuracy.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an embodiment of the spin coating device according to the invention, and Fig. 2 shows the in-plane thickness distribution of the resist film obtained by the present invention and the in-plane thickness distribution of the resist film obtained by the conventional method. It is a chart showing film thickness distribution. In the figure, 11 is a spin coating device, 12 is a base, 13 is a case, 14 is a turntable, 15 is a motor, 16 is a rotating shaft, 1B is a substrate, 19 is a lid, 20 is a vaporizer, and 21 is a pipe. be. No. 1 Fig. 09I8 C voice indicating a distance of 1°C force during differential combing] Part Z Diagram procedural amendment 1, case description 1985 Patent Application No. 103998 2) Name of invention Spin coating method and spin coating device 3. Relationship with the case of the person making the amendment Patent applicant address 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Name
(004) Voluntary amendment by one person other than Asahi Glass Co., Ltd. 6, Number of inventions increased by amendment None 7, Subject of amendment (1) Detailed description of the invention in the specification (2) Drawing 8, Contents of amendment (1) ) “Equilibrium” on page 5, line 13 of the specification is “predetermined”
I am corrected. (2) "Volatile solution" on page 5, line 13 of the specification is corrected to "volatile component." (3) “Film formation” on page 5, lines 13-14 of the specification is changed to “
"Volatilization," he corrected. (4) “Equilibrium” on page 5, line 15 of the specification is “predetermined”
I am corrected. (5) "To form a film" on page 5, line 16 of the specification is corrected to "to evaporate volatile components." (8) Correct Figure 2 of the drawings as shown in the attached sheet. that's all

Claims (6)

[Claims] (1) In a spin coating method in which a volatile solution is dropped onto a substrate and the substrate is rotated to spread and apply the volatile solution, the atmosphere is filled with volatile components of the volatile solution during spin coating. A rotary coating method characterized by: (2) The spin coating method according to claim 1, wherein the volatile solution is a resist solution. (3) The spin coating method according to claim 1 or 2, wherein the volatile component is ethyl cellosolve acetate. (4) The spin coating method according to any one of claims 1 to 3, wherein the base material is glass, a mask blank, or a wafer. (5) In a spin coating device in which a mechanism for supporting and rotating a base material is provided in a predetermined case, and by rotating the base material, a volatile solution dropped onto the base material is diffused and coated,
A rotary coating device comprising a lid for sealing the case. (6) A spin coating device in which a mechanism for supporting and rotating a base material is provided in a predetermined case, and the volatile solution attached to the base material is diffused and coated by rotating the base material,
A spin coating apparatus characterized by comprising a supply means for filling the case with volatile components of the volatile solution.