JPH05123632A - Liquid coating substance coating method - Google Patents

Abstract

(57) [Summary] [Purpose] When a substrate or the like is rotated and a liquid coating substance such as resist is coated on the substrate by using centrifugal force, the wettability between the coating surface and the liquid coating substance is poor. Prevents uneven coating. [Structure] Before applying the liquid coating substance, a step of applying a liquid treatment agent having a surface tension not higher than that of the liquid coating substance and having compatibility with the liquid coating substance to the coating surface is provided.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for applying a liquid coating material to the surface of a sample.

[0002]

2. Description of the Related Art By a so-called spinner coating device, a sample to be coated on a flat plate such as a wafer or a mask substrate is horizontally rotated and the liquid coating substance supplied to the surface is diffused outward by a centrifugal force to coat the sample. The coating method (hereinafter referred to as “rotary diffusion coating method”) is superior in uniformity of the thickness of the coating film compared to other methods such as spray coating, so that a fine pattern is formed on a semiconductor wafer or an exposure mask substrate. In photolithography, it is used to apply a photoresist to a semiconductor wafer or an exposure mask substrate, and recently, it has been favorably used as the size of a wafer and the size of a liquid crystal display device increase.

FIG. 2 is a diagram showing the construction of a spinner coating device. A substrate 1 to which a liquid coating substance is applied, for example, a circular substrate such as a wafer, is held on a table 3 by means of vacuum suction or the like, and the table 3 is horizontally rotated by a motor 6 via a shaft. Usually, an enclosure, commonly called a cup, is provided around these to prevent the coating material from scattering from the periphery of the apparatus.

The processing of the spin diffusion coating method is performed as follows, for example. (1) The substrate 1 to be coated is held on the table 3 concentrically with the grooves. (2) Means for supplying liquid coating material such as resist (not shown)
Is dripped and supplied to the rotation center portion 5 of the coating surface 2 of the substrate 1. (3) The substrate 1 is horizontally rotated together with the table 3 by the drive of the motor 6, the liquid coating material supplied to the coating surface 2 is diffused on the coating surface 2 and outward, and the excess liquid coating material is coated. A coating film having a uniform thickness is formed on the coating surface 2 of the substrate 1 by scattering from the outer periphery of the surface 2 to the outside of the substrate 1. (4) Stop rotation of the motor 6 and remove the substrate 1 coated with the liquid substance.

Thus, the coating on the coating surface is completed.

Next, the substrate to which the liquid coating substance is applied will be described. 3 to 5 are cross-sectional views showing the outline of the substrate to be coated with the liquid coating substance and the coating surface thereof.

FIGS. 3A and 3B show a substrate 1 in which the entire coating surface 2 is made of the same material. It should be noted that (2) shows a substrate having two layers. Figure 4 shows coated surface 2
3 shows a substrate composed of a plurality of different materials, which are not the same as each other, and the region of the constituent material 9 _{1 and} the region of the constituent material 9 ₂ are different materials. Figure 5 is the material of the coating surface is a entirely identical only constituent material 9 _1, it indicates a substrate there is a step (unevenness) not flat shape of the coated surface.

Typical examples of the constituent material of the coating surface include metals, metal oxides, ceramics, glass and plastics, and a single material or a plurality of materials are used for the coating surface depending on the purpose. These materials have different degrees of wettability with the liquid substance to be applied. If the material forming the coating surface has poor wettability with the liquid substance to be coated, the method of diffusing and coating the liquid substance on the coating surface by using centrifugal force prevents uniform diffusion and causes uneven coating. Will occur. Even when the coating surface is composed of a plurality of materials having different wettability, uniform diffusion is hindered and the same problem occurs. Further, even if the entire coating surface is made of the same material, if it is not flat and has steps (unevenness), the application to the uneven portion tends to be insufficient.

[0009]

As described above, in the spin diffusion coating method of the liquid coating material, when coating unevenness often occurs, air bubbles remain in the coating film after drying, or pinholes occur. There is. This often occurs especially when a liquid coating substance having a relatively high viscosity is applied, or when the substrate coating surface is composed of at least two different kinds of materials, or when there is a step on the substrate coating surface. ing. That is, when the wettability (familiarity) between the liquid coating substance and the coating surface is poor, or when the composition of the coating surface is not uniform throughout and the wettability varies depending on the position on the coating surface, The uniform diffusion of the coating substance over the entire coated surface is hindered, resulting in uneven coating.

An object of the present invention is to provide a coating method for a liquid coating substance which can obtain a coating film having a uniform thickness over the entire coating surface even under the above-mentioned conditions.

[0011]

In a method of applying a liquid coating substance by diffusing it onto the surface of a sample while horizontally rotating a sample on a flat plate, the liquid coating substance is applied before the application of the liquid coating substance. A liquid treatment agent which is compatible with and has a surface tension equal to or less than the surface tension of the liquid coating substance is applied alone or together with a surfactant by a method similar to the method for applying the liquid coating substance. Have steps.

Further, the main solvent of the liquid coating material may be used in place of the liquid processing agent.

[0013]

[Function] The wettability with the coating surface is higher than that of the liquid coating substance,
In addition, by first applying the liquid treatment agent having compatibility with the liquid coating substance to the coating surface, the coating conditions of the coating surface are made uniform, and the liquid coating substance is uniformly diffused and coated.

[0014]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a flow chart showing a processing flow of an embodiment of a method of applying a liquid coating material of the present invention. This processing flow will be described using the spinner coating apparatus shown in FIG. 2. First, the substrate 1 to be coated with the liquid coating substance is placed on the table 3 with its coating surface 2 facing upward, and is held concentrically with the step (step 11). Next, the liquid processing agent is supplied to the central portion of the coating surface 2 of the substrate 1 (step 12), and when the motor 6 is driven, the substrate 1 rotates together with the table 3, and the liquid processing agent moves to the outside of the central portion on the coating surface. Diffusion coating (step 13). Next, the liquid coating substance is supplied to the central portion of the coating surface 2 of the substrate 1 (step 14), and the liquid coating substance is diffused and coated on the coating surface 2 rotated by the drive of the motor 6 (step 1).
5) The motor 6 is stopped, the substrate is removed, and the coating process is completed.

The feature of the coating method of the present invention resides in that steps 12 and 13 of applying a liquid treatment agent are placed before steps 14 and 15 of the coating treatment of a target liquid coating substance. Since the application of the liquid treatment agent forms the application surface 2 on which the liquid application substance can be uniformly diffused and applied, the liquid treatment agent has compatibility with the liquid application substance and the surface tension thereof is the liquid application. It should be equal to or less than the surface tension of the substance.

As the liquid treatment agent, for example, methanol,
Lower alcohols such as ethanol, n-propanol, iso-propanol, or acetone, methyl, ethyl,
It is a ketone such as a ketone or an ester such as methyl acetate or ethyl acetate, and is selected depending on the type and characteristics of the liquid coating material. It may also be appropriate to use the main solvent in the liquid coating substance. Further, it is also possible to use a surfactant together with the liquid processing agent on condition that the substrate 1 and the liquid coating material are not adversely affected. In particular, when the liquid coating substance is aqueous, the liquid treating agent may be water to which a surfactant is added.

Steps 12, 13 or 14 of FIG.
15 describes that the liquid treatment agent or the liquid treatment substance is dropped and supplied to the rotation center portion 5 of the coating surface 2 and then the motor 6 is driven to start the diffusion coating. The supply of the substance to the coating surface 2 is not limited to dropping onto the rotation center portion 5, and may be dropped onto the rotating coating surface 2.

The basic conditions for applying the liquid treatment agent are that the rotation speed of the table 3 is the same as in the case of diffusion application of the liquid application substance, but it should be lower than the rotation speed at the time of application of the liquid application substance. Is desirable.

Further, it is desirable that the movement from step 13 to step 14, that is, the start of the application of the liquid coating substance, be carried out before the previously applied liquid treatment agent has dried.

[0021]

When a liquid coating substance is spin-diffusively coated on a substrate or the like, a substrate is obtained by spin-diffusion coating a liquid treatment agent having a surface tension not higher than that of the liquid coating substance and having compatibility with the liquid coating substance. By applying the liquid coating substance after improving the wettability between the coating surface and the liquid coating substance, the effect of eliminating or greatly reducing the occurrence of coating unevenness, bubbles, pinholes, etc. that can prevent the uniformity of the coating film There is.

Particularly, when the substrate to be coated is a material which is difficult to be wet with the liquid coating substance, when the coating surface is composed of a plurality of materials and the wettability with respect to the liquid coating substance is not uniform, or when there is a step on the coating surface. The effect is extremely remarkable.

[Brief description of drawings]

FIG. 1 is a flow chart showing a processing flow of an example of a coating method of a liquid coating substance of the present invention.

FIG. 2 is a configuration diagram of a spinner coating device.

FIG. 3 is a cross-sectional view showing an outline of a substrate to be coated with a liquid coating substance and its coating surface.

FIG. 4 is a cross-sectional view showing an outline of a substrate to be coated with a liquid coating substance and its coating surface.

FIG. 5 is a cross-sectional view showing an outline of a substrate to be coated with a liquid coating substance and its coating surface.

[Explanation of symbols]

 1 substrate 2 coating surface 3 table 4 axis 5 rotation center 6 motor

Claims (2)

[Claims] 1. A method of applying a liquid coating substance by diffusing it onto the surface of the sample while horizontally rotating a sample on a flat plate, and compatibilizing the liquid coating substance with the liquid coating substance before applying the liquid coating substance. And having a step of applying a liquid treatment agent having a surface tension equal to or lower than the surface tension of the liquid coating substance, alone or together with a surfactant, by a method similar to the method for coating the liquid coating substance. A characteristic method for applying a liquid coating material. 2. The method for coating a liquid substance according to claim 1, wherein the liquid treatment agent is the same as the main solvent of the liquid coating substance.