JPH0344824B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method of applying a liquid agent such as a photoresist onto a substrate surface using a roll coater, and particularly to a method of effectively leveling the applied liquid film to make it uniform in thickness. [Prior Art] In semiconductor manufacturing processes and other manufacturing processes such as thermal head manufacturing, metals (Au, Cu, Cr, SnO ₂ , ItO
etc.) A roll coater for applying a photoresist to the surface of a substrate on which a photoresist has been deposited is well known for the purpose of forming a desired pattern using a photolithography method. Generally, a roll coater has a configuration as schematically shown in the drawing, in which a coating roll 1 and a doctor roll (also called a metering roll) 2 are in contact with each other and are pivotally supported, and a back-up roll 3 is arranged below the coating roll 1. Then, the substrate 4 to be treated is sent between the coating roll 1 and the back-up roll 3 by a conveyor such as a roller conveyor 5, and the required liquid is supplied to the coating roll 1 from a liquid supply pipe 6 disposed above. The liquid agent is supplied to the contact portion 7 with the doctor roll 2, and each roll is driven to rotate in the direction of the arrow to apply the liquid onto the surface of the substrate 4 via the surface of the coating roll 1. The amount of liquid applied (thickness of the liquid layer) can be adjusted to a desired value by adjusting the contact pressure of the doctor roll 2 against the coating roll 1. The drawing shows the most basic configuration of a roll coater, but instead of the roller conveyor 5, the substrate is placed on a table that moves horizontally, and the whole table is sent under the coating roll 1. In this way, devices in which the back-up roll 3 is omitted and devices in which a plate-shaped doctor knife is used in place of the doctor roll 2 are also known. When a liquid such as a photoresist is applied to a thickness of, for example, several μm using such a roll coater, pinholes, linear unevenness, or wrinkles may occur in the liquid on the surface of the applied liquid layer. . If there is any unevenness on the surface of the applied photoresist film, poor adhesion may occur when the pattern on the original plate is closely exposed, and problems such as line breakage or short circuits may occur in the pattern. It must be applied so that it is as smooth as possible. One of the causes of this non-uniformity in film thickness is thought to be that the surface of the coating roll 1 is provided with a large number of narrow grooves for holding the liquid agent. That is, since the applied liquid layer becomes thick in the narrow groove portion, the thickness of the applied liquid layer does not immediately become uniform, especially when the viscosity is high. Additionally, depending on the ambient conditions such as the temperature and humidity surrounding the roll coater, the drying state of the applied liquid may locally slow down, and a relatively uniform liquid layer thickness may not be obtained in areas where drying is slow. This is also thought to be due to the fact that even if the roll is dried, unevenness corresponding to the narrow grooves on the roll surface remains in the portion that dries relatively early. Furthermore, the cleanliness of the substrate surface and the relationship between the metal film formed on the substrate surface and the liquid agent (for example, surface tension) are also considered to be factors that cause unevenness in the liquid layer thickness. As a means to deal with this problem, the invention disclosed in Japanese Patent Application No. 58-75626 (Japanese Unexamined Patent Publication No. 59-203665, title of the invention "Roll Coating Method and Apparatus") by the present applicant is based on the above-mentioned roll coater. A uniform coating result is obtained by arranging a plurality of units in series, applying a relatively low-viscosity liquid in the first stage, and then applying a relatively high-viscosity liquid in the second stage. Also, patent application No. 59-214370 also filed by the present applicant.
The invention described in No. (name of the invention "coating device") is
A means is attached to the front or rear stage of the roll coater to spray a solution that dilutes the liquid to be coated onto the substrate surface in the form of fine particles or in a vaporized state, thereby reducing the viscosity of the liquid and achieving uniform coating. It is designed to obtain the state. [Problems to be Solved by the Invention] Each of the above-mentioned means of the prior application is effective, but the former requires a plurality of roll coaters, and the latter requires a method for atomizing or vaporizing the solution. Since it is necessary to install a device for spraying on the substrate surface and a device for spraying onto the substrate surface, there is a problem in that the scale of the equipment increases and the cost increases. The present invention provides a liquid coating method that does not require any incidental equipment on the roll coater itself and makes it possible to obtain a liquid layer of uniform thickness using only a single roll coater. It is something. [Means for Solving the Problems] The present invention is characterized in that a leveling promoter that promotes uniformity of the liquid layer when the liquid is applied is added in advance to the liquid to be applied. It is something. As this leveling accelerator, one that has both the effect of lowering the viscosity of the liquid agent similar to the first one of the prior application and the drying suppressing effect of slightly slowing down the drying speed of the liquid layer after application is applied. . It has been experimentally confirmed that "N-methyl-2-pyrrolidone" or a derivative thereof is effective as such a leveling accelerator for photoresists used in semiconductor manufacturing. [Function] The liquid agent applied to the surface of the substrate to be processed has a lower viscosity due to the leveling accelerator added in advance and has abundant fluidity, so the surface of the liquid layer quickly becomes smooth, and at the same time, Due to the drying suppressing effect of the leveling accelerator, fluidity is maintained until the surface becomes sufficiently smooth. Therefore, unevenness or pinholes in the liquid layer that occur in correspondence with the narrow grooves cut on the surface of the coating roll are completely eliminated, and a liquid layer with an extremely uniform thickness can be obtained. It should be noted that the leveling accelerator has a relatively low degree of drying suppression effect, so it is possible to apply the same manufacturing process as before by placing a normal drying device next to the coating process using a roll coater. is possible. [First Example] An example in which a photoresist is applied to a substrate having a metal film deposited on glass will be described. In this example, "JSR-3003-S" manufactured by Japan Synthetic Rubber Co., Ltd. was used as a photoresist.
As a leveling accelerator, the above-mentioned “N-methyl-
2-pyrrolidone" was added in advance at a required ratio, and coating was performed using a roll coater according to a conventional method. The distance between the coating roll 1 and the doctor roll 2 of the roll coater (see drawing) and the distance between the coating roll 1 and the back-up roll 3 are maintained at constant values, and the leveling accelerator added to the photoresist is adjusted. The photoresist film was coated on a substrate at different proportions (weight ratio) using a roll coater, and the surface condition of the photoresist film after drying was checked, and the results shown in the table below were obtained.

[Table] Note: Leveling property 〓×〓 indicates poor, 〓△〓 indicates slightly good, 〓○〓 indicates good.
In case 1, where "N-methyl-2-pyrrolidone" was not added at all as a leveling accelerator, the pattern of narrow grooves carved on the coating roll was
The photoresist film remained in a transferred state on the surface of the applied photoresist film, and considerable unevenness was observed in the film thickness, and the leveling property was judged to be poor. In case 2, when the leveling accelerator was added at a weight ratio of 4:1, the unevenness on the surface of the applied photoresist film disappeared and a uniform film thickness could be obtained, but it took a long time to reach that state. It took a relatively long time, 60 to 90 seconds, and it was determined that there was a problem in actual work. In case 3, when the leveling accelerator is added at a weight ratio of 4:2, a uniform film thickness can be obtained, and the time required for the surface of the photoresist film to reach a uniform and smooth state after coating is approximately 10%. It was judged to be practical. Furthermore, when the amount of leveling accelerator added was increased to a weight ratio of 4:4, a uniform film thickness was obtained as well, and the required time was slightly less than 10 seconds, which is also suitable for practical use. It was determined that it was. [Second Example] As a photoresist, "Microposit #1400 Positive Resist" manufactured by Shipley Far East Co., Ltd. was used, and "N-methyl-2-pyrrolidone" was added as a leveling accelerator and applied. However, almost the same results were obtained. As mentioned above, the reason why it is possible to obtain uniform thickness of the applied photoresist film by adding "N-methyl-2-pyrrolidone" in advance is due to the viscosity of the photoresist as a liquid agent. It is understood that reducing the photoresist to increase its fluidity and suppressing drying of the photoresist for a period of time until the film thickness becomes uniform are based on maintaining the fluidity. The fact that the viscosity of the photoresist decreases is supported by the fact that the "film thickness" data in the table above becomes smaller as the amount added increases. This is understood to be because the boiling point of ``-2pyrrolidone'' is 100°C or higher and the evaporation rate is slow. The above explanation is based on the use of “N” as a leveling accelerator.
-Methyl-2-pyrrolidone" has been described based on the example, but it is not necessarily limited to this, and the present invention can be applied as long as it has the effect of reducing the viscosity of the liquid to be applied and suppressing drying. It is possible to apply the method. For example, when targeting photoresist, "N-methyl-
A similar effect can be obtained by using a derivative of 2-pyrrolidone. [Effects of the invention] (1) When applying a liquid to a substrate to be processed using a roll coater, the thickness of the applied film can be made uniform,
A film with a smooth surface can be obtained. (2) The desired effect can be obtained by simply adding a leveling accelerator to the target liquid in advance, and there is no need to make any modifications to the roll coater itself.
Easy to implement.

[Brief explanation of drawings]

The drawing is a schematic diagram showing the configuration of a roll coater that is an object of implementing the method of the present invention. DESCRIPTION OF SYMBOLS 1...Coating roll, 2...Doctor roll, 3...Backup roll, 4...Substrate to be processed, 5...Roller conveyor, 6...Liquid supply pipe, 7...Roll contact portion.

Claims (1)

[Scope of Claims] 1. Using a roll coater equipped with a coating roller in which a large number of thin grooves are carved in the circumferential direction on the circumferential surface, a substrate on which a metal film is formed on at least a part of the surface,
A method for applying a photoresist, characterized in that N-methyl-2-pyrrolidone or a derivative thereof is added in advance to the photoresist at a weight ratio of 4:1 to 1:1. Application method.