JPH0659453B2 - Method of applying resist to substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of use) The present invention relates to a method for coating a resist on a substrate, and in particular, to a coating layer having a uniform film thickness on a predetermined surface of a substrate having corners and the like. The present invention relates to a resist coating method that can be easily formed.

(Prior Art) A photoresist is generally used as a masking material in forming a desired pattern on a circuit board, for example. That is, a desired circuit pattern or the like is formed by applying a photoresist on a predetermined substrate surface, exposing and developing the photoresist to create a predetermined photoresist master (pattern), and then performing an etching process or a vapor deposition process. . By the way, in the case of forming a thin coating layer in the coating formation of the resist film described above, after the substrate is subjected to cleaning treatment such as pure water cleaning or heating, the resist film is generally formed by a spin coating method (spin coating method). It is formed by coating.
However, in the above resist coating, it is difficult to form a coating film having a uniform film thickness, especially when the substrate has corners, for example, one side
The thickness of the coating film formed by spin coating on a 250 mm square substrate and drying at 110 ° C. was as shown in FIG. That is, the film thickness was 1.2 μm at any point (a) in the side direction, whereas the film thickness in the corner direction was 1.2 μm at the point near the center and at the corner side (c). The thickness was 2.3 μm, the point (d) was 3.8 μm, and the film thickness at the corner portion was 3 to 4 times as large as that at the central portion of the substrate (1). Such unevenness of the film thickness of the coating film is accompanied by a decrease in pattern resolution when considering, for example, a case where a photoresist coating film is formed, and exposure and development are performed to form a desired pattern. There is no loss of accuracy. Especially when it is desired to form a fine circuit on a rectangular substrate, for example, when manufacturing a circuit substrate for a small display device such as a liquid crystal television, the uneven thickness of the resist film becomes a factor that hinders formation of a predetermined circuit pattern. ing. Therefore, a complicated operation such as forming a resist coating layer on a large substrate and cutting out a rectangular substrate having a required size is required.

(Problems to be Solved by the Invention) The present invention addresses the above circumstances and provides a practical resist coating method capable of easily forming a resist film having a substantially uniform film thickness on a substrate. Is.

[Structure of Invention]

(Means for Solving the Problem) In the present invention, when a resist is applied to a substrate by a spin coating method, when the substrate is pretreated by ultraviolet irradiation and heat treatment, the wettability of the substrate with respect to the resist is improved. It was made paying attention to the fact that the coating film is remarkably improved and a uniform coating film is formed. That is, in the present invention, when forming a resist film on a substrate by a spin coating method, the main point is to subject the resist coating surface of the substrate to a heat treatment at the same time as the ultraviolet irradiation treatment or in advance.

(Operation) When the predetermined surface of the substrate (resist coated surface) is subjected to the ultraviolet irradiation treatment in a state where the temperature is raised by the heating treatment as described above, the treated surface is effectively cleaned, Therefore, the wettability with respect to the resist is improved. Thus, when the resist is applied by the spin coating method, a coating film having no film thickness unevenness (uniform film thickness) is easily and constantly formed in the side direction and the corner direction of the substrate.

(Examples) Examples of the present invention will be described below. First, a square glass rectangular substrate with a thickness of 1 mm and a side length of 250 mm is prepared, and this rectangular substrate is placed substantially horizontally on a hot plate with a set temperature of 150 to 200 ° C, while a 65 W low-pressure mercury lamp. UV light was applied to the rectangular substrate surface for 120 seconds. Thus, the rectangular substrate is subjected to ultraviolet irradiation treatment and heat treatment,
A predetermined surface (resist coated surface) of the rectangular substrate was cleaned. Then, as shown in FIG. 1, the rectangular substrate (1b) was adsorbed and supported by a vacuum chuck (4) mounted on a rotary shaft (3) rotated by a rotary drive mechanism (2). This rectangular substrate (1b)
In the suction support by the vacuum chuck (4), the surface opposite to the processing surface of the substrate (1b) is the vacuum chuck (4) side. Then, at the center of the upper surface (processing surface) of the rectangular substrate (1b) supported by the vacuum chuck (4), for example, a viscosity of 30 cp
The rectangular substrate (1b) that is dripped with the resist of s, then drives the rotation drive mechanism (2), and is adsorbed and supported by the vacuum chuck (4).
To rotate. The rotation of this rectangular substrate (1b) is, for example, 60r.p.
The dropped resist is first spread on the surface of the rectangular substrate (1b) by low-speed rotation of about m, and then switched to high-speed rotation of, for example, about 3500 rpm, and the resist is rotated by centrifugal force to rotate the rectangular substrate (1b). The required resist coating is performed by further expanding in the outer peripheral direction. FIG. 2 shows the state of the thickness of the resist coating layer formed by drying at 110 ° C. after the spin coating, and the film thickness was substantially uniform in the side direction and the corner direction. In FIG. 2, the point (a) has a film thickness of 1.2 μm, and the point (a ′) has a film thickness of 1.3 μm.

In the above-mentioned embodiment, the ultraviolet irradiation treatment and the heating treatment are simultaneously performed on the substrate. However, this treatment may be performed by first performing the heating treatment and then performing the ultraviolet irradiation treatment.
That is, since the heat treatment in this pretreatment promotes the ultraviolet irradiation treatment, there is no problem even if the heating treatment is performed in advance and the ultraviolet irradiation treatment is subsequently performed. However, the heating source for the above heat treatment is not limited to the hot plate, and other means may be used, and the ultraviolet ray source for irradiating the ultraviolet rays is not limited to the low pressure mercury lamp. On the other hand, in spin coating, in the above, the rotation was performed by two-step switching from low speed to high speed, but it may be switched in multiple steps, or conversely, it may be performed at constant speed. In short, it may be appropriately selected in consideration of the viscosity of the resist used. Further, the substrate is not limited to the above-mentioned shape, and may be, for example, one having rounded corners.

Pretreatment of the substrate prior to applying the resist is effective for forming a coating layer having a uniform film thickness only by UV irradiation, but the irradiation treatment requires a relatively long time and is therefore sufficiently satisfactory for practical use in terms of mass productivity. It is hard to say.

〔The invention's effect〕

As is clear from the above specific examples, according to the present invention, a resist coating layer having a substantially uniform film thickness can be formed on a substrate, for example, a rectangular substrate for a liquid crystal display device. However, it is easy to form a uniform coating layer on a given surface of a substrate of this kind without unevenness in film thickness when, for example, a photoresist is applied, and exposure and development are performed to form a mask pattern or the like. Especially effective for. That is, since the resist coating layer has no film thickness unevenness, variations in resolution are eliminated in the exposure step, variations in side etching in the development process and resist residue are eliminated, and a desired circuit pattern or the like can be formed with high precision. Of course, the present invention is not limited to the case of forming a mask using a photoresist, but can be applied to the formation of a general coating film layer. That is, it is possible to form a coating layer having a uniform film thickness, good appearance, and being difficult to peel off from the substrate.

[Brief description of drawings]

FIG. 1 is an explanatory view for explaining the method of the present invention, FIG. 2 is a plan view schematically showing a distribution state of a resist film thickness applied and formed on a rectangular substrate according to one embodiment of the present invention, and FIG. It is a top view which imitates and shows the distribution state of the resist film thickness applied and formed in the square substrate by the conventional method. (1b) …… Substrate, (2) …… Rotation drive mechanism (3) …… Rotary axis, (4) …… Vacuum chuck

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Claims (3)

[Claims] 1. A step of subjecting a resist-coated surface of a heated substrate to an ultraviolet irradiation treatment, and dropping a resist on a substantially central portion of a treated surface of the substrate subjected to the ultraviolet irradiation treatment, and rotating the substrate. And a step of applying the resist to the entire surface of the substrate onto which the resist has been dropped by the centrifugal force. 2. The method for coating a resist on a substrate according to claim 1, wherein a low-pressure mercury lamp is used as an ultraviolet irradiation source in the ultraviolet irradiation treatment. 3. In resist coating by rotating a substrate,
The method for coating a resist on a substrate according to claim 1 or 2, wherein the rotation of the substrate is switched between low speed and then high speed.