JPS60193339A - Method of coating resist film - Google Patents

Abstract

PURPOSE:To obtain a desired film thickness while avoiding formation of unevenness on the surface of the film, by rotationally applying a resist solution which is dropped down on a target material in the atmosphere applied with a pressure at least higher than atmospheric pressure. CONSTITUTION:A rotatable stage 2 is received in an envelope 4 of a spinner having a resist discharge opening 4H on the bottom face thereof. A rotary shaft provided on the lower face of the stage is projected outside the envelope 4 through an O ring 6. A semiconductor wafer 1 is put on the stage 2, and the envelope 4 is covered with a cover 5 having a pressurized gas feed opening 7. This cover 5 is sealed to the envelope 4 airtightly while the outlet of the discharge opening is also closed airtightly. For operating the spinner constructed in this manner, nitrogen gas whose pressure is adjusted to be 2-3kg/cm<2> is injected through the feed opening 7. After the pressure is stabilized, a proper quantity of resist is dropped down from a nozzle 3 provided to pass through the envelope 4 and, simultaneously, the stage 2 is rotated at a predetermined rate so that the resist is diffused into a uniform thickness.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a resist film coating method, and in particular to a resist film coating method applied to a semiconductor wafer (hereinafter abbreviated as wafer) in a photo process when manufacturing a semiconductor device. This invention relates to a method of coating a film.

Prior Art and Problems As is well known, in semiconductor devices such as ICs, a large number of elements are formed on the uni/%- plane, which are divided and assembled into a pan cage. In the process (wafer process), patterning is performed by repeatedly applying a photo process to the wafer surface.

In such photoprocessing, the most important thing is to form fine patterns with high precision, and for this purpose, electron beam exposure has been used instead of the conventional ultraviolet exposure method. It's here. In addition, resist film materials with high sensitivity, high resolution, and good film retention rates have been developed, and with the progress of such photoprocesses, the degree of integration of ICs has also significantly improved.

On the other hand, in such a photo process, the method of applying the resist film is also an important issue, and the resist film must be coated as uniformly and thinly as possible on the wafer surface. Therefore, conventionally, a rotary coating device (spinner)
is commonly used, and FIG. 1 shows a schematic sectional view of such a conventional spinner. In the figure, 1 is a wafer, 2 is a stage, 3 is a resist solution dripping nozzle, and 4
For example, the stage 2 is an envelope, and the stage 2 sucks and holds the wafer 1 from the back side using a vacuum chuck, and is a stage that can be connected to a drive device such as a motor and rotated at a speed of 3000 to 5000 rpm. The envelope 4 is configured to prevent the blown-off resist solution from rebounding and adhering to the wafer 1 surface again. 411 in the figure is a discharge port for the blown away resist solution.

In this manner, a certain amount of resist solution is dropped from the dropping nozzle 3, and when it has spread to a certain extent over the surface of the wafer, the stage 2 is rotated at the above speed to spread and uniformly coat the entire surface of the wafer. However, recently, wafers have become larger with a diameter of 4 to 5 inches, and when the resist solution is dropped and the stage 2 is rotated to spread it over the entire surface of the wafer, a vortex-like pulsating current flows from the drop point to the surface of the resist film. is formed. FIG. 2 shows a wafer 1 coated with a resist film 11.
The resist film usually has a constant thickness of 1 to 2 μm, but the difference in thickness due to such pulsating flow is about 3000λ.

In order to eliminate these veins, various measures have been taken, such as changing the concentration of the resist solution, but it is difficult to maintain a predetermined film thickness and eliminate the veins. Maintaining a specified film thickness is extremely important in the photo process.
This is because if the film thickness becomes thin, the pattern shape cannot be maintained during etching, and if the film thickness is large, it becomes difficult to form a fine pattern.

(C1 Purpose of the Invention The present invention proposes a coating method that maintains a predetermined thickness of the applied resist film and prevents the formation of veins on its surface.

(d) Structure of the Invention The object is achieved by a resist film coating method in which a resist solution is dropped onto a sample to be coated (wafer) and spin-coated in an atmosphere with a pressure higher than at least atmospheric pressure. Ru.

(e) Examples of the invention An embodiment will be described in detail below with reference to one drawing.

FIG. 3 shows a schematic sectional view of an embodiment of the spinner according to the present invention. As shown in the figure, the envelope 4 is covered with a cover 5, the banking is sandwiched and hermetically sealed. An O-ring 6 is interposed between the stage 2 and the stage 2 for airtight sealing. Further, the resist solution outlet 411 is also sealed. Thus, the pressure from the inflow lower of the pressurized gas is 2 to 3 kg/cIl.
1 liter of nitrogen gas flows into the container and pressurizes it, and by increasing the pressure, a certain amount of the resist solution is dripped from the dropping nozzle 3.

When the resist solution is dropped in a 6 (f) shape and has spread to about half the surface of the wafer, the stage 2 is rotated at high speed to spread it over the entire surface of the wafer.

Then, during dropping, the evaporation rate of the solvent (solution in which the resist material is dissolved) is slowed down, the change in viscosity is reduced, and pulsation is reduced. According to the implementation results, the error in film thickness could be reduced to several hundred people.

In the present invention, since the resist solution is dropped under pressure in this manner, the relationship between the thickness of the resist film and the viscosity of the resist solution must be readjusted. However, such a method of application under pressure can therefore significantly reduce the pulsation.

(f) Effects of the Invention As is clear from the above description, the present invention is effective in reducing pulsating currents and making the thickness of the applied resist 11 more uniform.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a conventional spinner, FIG. 2 is a sectional view showing pulsating flow, and FIG. 3 is a schematic sectional view of a spinner according to an embodiment of the present invention. In the figure, 1 is a wafer, 2 is a stage, 3 is a resist solution dripping nozzle, 4 is an envelope, 48 is a solution outlet, and 5
6 indicates a cover, 6 indicates an O-ring, and 7 indicates a gas inlet.

Claims (1)

[Claims] 1. A method for applying a resist film, characterized in that a resist solution is dropped onto a sample to be coated and spin-coated in an atmosphere in which a pressure higher than at least atmospheric pressure is applied.