JPH0594944A - Method of coating resist - Google Patents

Abstract

PURPOSE:To reduce the irregularities of a resist film coated by a spin coating method in each semiconductor wafer or among semiconductor wafers to obtain an even film thickness and to make possible the formation of the film thickness to cover a wide range using a few kinds of resist. CONSTITUTION:When a resist material is dripped on the surface of a semiconductor wafer, the temperature of the resist material is made 2 deg.C or more higher than the atmospheric temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a resist to a semiconductor wafer, which is intended to obtain a uniform film thickness by reducing the variation in the applied resist film thickness. It is intended to obtain a uniform film thickness when forming a thick film.

[0002]

2. Description of the Related Art In a photolithography technique often used in the manufacturing process of semiconductor devices, a resist acts as a mask for selectively etching a material to be processed.
Methods for applying this resist to the surface of a semiconductor wafer include a spin coating method, a roller coating method, a spray coating method, etc., but a spin coating method which is advantageous in stability and uniformity of a coating film is generally used. Target. In this spin coating method, a resist material is dropped onto the surface of a semiconductor wafer held horizontally, and the semiconductor wafer is rotated in situ to form a resist film on the surface of the semiconductor wafer.

There are various factors that determine the resist film thickness in this spin coating method. For example, the number of rotations of the spin motor, the viscosity of the resist material, the ambient temperature / humidity, the amount of resist dropped from the nozzle, and the like. In order to apply the resist uniformly, these factors are controlled to control the resist film thickness.

[0004]

However, even if the above-mentioned factors are controlled, there is a problem that the resist film thickness varies from semiconductor wafer to semiconductor wafer. There is also a problem that the film thickness is different between the central part and the outer peripheral part in the semiconductor wafer. The temperature of the resist coating atmosphere and the temperature of the resist material to be coated are ± 1
It is considered that this is because the temperature fluctuates by about 0 ° C. and the temperature is different between the central part and the outer peripheral part in the semiconductor wafer.

Conventionally, such a problem has been controlled by the number of rotations of the spin motor, the rotation pattern of the spin motor, or the amount of resist dropped from the nozzle.
Not only the control is complicated but also the film thickness variation is insufficient, which leaves a problem in product yield.

In addition, when the resist film thickness to be applied is to be changed depending on the type of the underlying layer to be etched, the rotation speed of the spin motor, the rotation pattern of the spin motor, or the amount of resist dropped from the nozzle is changed. Although the film thickness was controlled to a predetermined value by this, it was difficult to keep the changed resist film thickness uniform, and a stable coating film could not be obtained. Note that it is an advantageous method to provide a plurality of nozzles for dropping the resist material, and to supply the resist material having different viscosity depending on the resist film thickness to be applied from the nozzle toward the semiconductor wafer, but for each resist. It is necessary to set various conditions and the equipment becomes complicated.

Therefore, it is conceivable that the low-viscosity resist is heated to a high viscosity to be used over a wide range of coating film thickness. However, when the resist temperature is increased, the resist film thickness also varies from semiconductor wafer to semiconductor wafer. In addition, there is a problem that the central portion and the outer peripheral portion in the semiconductor wafer have different film thicknesses.

The present invention advantageously solves the above-mentioned problem, and obtains a uniform film thickness by reducing the variation of the applied resist film thickness for each semiconductor wafer and within the semiconductor wafer. The purpose is to enable film formation over a wide range with a small number of resist species.

[0009]

In view of the temperature dependence of the resist film thickness, the inventors have made the temperature of the resist material, which has been the same as the atmospheric temperature, higher, so that the variation in the film thickness can be reduced. It has been found that it can be advantageously reduced.
This invention is based on the above findings.

That is, according to the present invention, in a temperature-controlled atmosphere, a resist material is dropped onto the surface of a semiconductor wafer held horizontally, and the semiconductor wafer is rotated on the spot to form a resist on the surface of the semiconductor wafer. In the resist coating method for forming a film, the resist coating method is characterized in that the temperature of the resist material is raised to 2 ° C. or higher with respect to the temperature of the atmosphere and then dropped.

[0011]

[Function] Fig. 1 shows the effect of varying the resist material temperature from 19 to 32 ° C when the ambient temperature is 24 ° C, and the influence on the resist film thickness coated on the Si wafer at the central portion and the peripheral portion of the Si wafer. The results of the examination are shown together with the average value. At this time,
Other conditions such as the resist material, the spin motor rotation speed, the spin motor rotation pattern, and the resist dropping amount are all the same.

From the figure, when the temperature of the resist material is lower than the atmospheric temperature, the film thickness changes (gradient of the graph) with respect to the temperature change is large, while when the temperature of the resist material exceeds the atmospheric temperature, the film thickness change with respect to the temperature change. It turns out that is gentle. The same can be said for the difference in film thickness between the central portion and the outermost periphery in the semiconductor wafer. Therefore, when the temperature of the resist material is the same as the atmospheric temperature as in the conventional case and the temperature of the resist material becomes lower than the atmospheric temperature due to the disturbance, the film thickness variation remarkably appears.

Therefore, according to the present invention, by increasing the temperature of the resist material to 2 ° C. or higher with respect to the temperature of the atmosphere,
Even if the temperature of the resist material becomes lower than the ambient temperature due to disturbance, the range is limited to a region where the film thickness change is gradual, and therefore the film thickness change is suppressed. In this case, the same applies to the central portion and the outermost periphery in the semiconductor wafer, and the difference in film thickness is small, so there is no problem.

When the temperature of the resist material is less than 2 ° C. with respect to the temperature of the atmosphere, there is a problem that the amount of film thickness variation due to disturbance becomes large. The upper limit depends on the film thickness to be applied and is not particularly limited, but if it is too high, the viscosity becomes too high, which is not preferable. Preferably 2
Increase the temperature by ~ 10 ° C.

In the concrete temperature control of the present invention, it is possible to control by changing either or both of the temperature of the resist material and the ambient temperature. Control of heating the resist material to a high temperature is easy.

[0016]

[Example] A 6-inch diameter Si wafer is horizontally held and fixed on a chuck of a spin coater, and the chuck is rotated at 1000 rpm.
While rotating for 6 seconds, a resist material: OFPR-800 (30 cP) is dropped onto this Si wafer surface with a dropping amount of 5 cc, and the chuck is rotated at a rotation speed of 600 rpm to form a film thickness of 1.2 μm.
A resist film of At this time, the atmosphere, the semiconductor wafer temperature isothermal with the atmosphere, the chuck temperature is 24 ℃,
On the other hand, the temperature of the resist material was 27 ° C. As a result,
± 0.005 film thickness difference between the center and outer edges of Si wafer
It was μm. In addition, the film thickness deviation in processing 25 sheets is ± 0.00
It was 5 μm.

On the other hand, when the temperature of the resist material was set to 24 ° C. and the other conditions were the same as above and resist coating was performed, the film thickness difference between the central part and the outer peripheral part of one Si wafer was ±. It was 0.05 μm. Moreover, the film thickness deviation in the processing of 25 sheets was ± 0.01 μm, and the film thickness variation was large.

The same resist material as described above is used, and in order to obtain a thicker resist film, the resist temperature is further raised to 27 ° C. and the chuck is rotated at 1000 rpm × 19 se.
The amount of dropping was 5 cc while rotating, and the chuck was rotated at a rotation number of 4500 rpm to obtain a resist film having a film thickness of 2.50 μm. At this time, the atmosphere, the semiconductor wafer temperature isothermal to the atmosphere, and the chuck temperature were 24 ° C. As a result, the film thickness difference between the central part and the outer peripheral part of one Si wafer is ± 0.01 μm, and the film thickness deviation in processing 25 wafers is ± 0.005 μm. It became possible with little fluctuation.

[0019]

According to the resist coating method of the present invention, the temperature of the resist material is raised to 2 ° C. or more with respect to the temperature of the atmosphere and then dropped, so that each semiconductor wafer having the resist film thickness coated or within the semiconductor wafer is coated. Can be reduced to obtain a uniform film thickness, and the product yield can be improved.
Further, it becomes possible to form a resist film having a wide range of thickness with a small number of resist species.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of a temperature change of a resist material on a resist film thickness.

Claims (1)

[Claims] 1. A resist film is formed on the surface of a semiconductor wafer by dropping a resist material onto the surface of a semiconductor wafer held horizontally in a temperature-controlled atmosphere and rotating the semiconductor wafer in place. In the resist coating method described above, the temperature of the resist material is raised to 2 ° C. or higher with respect to the temperature of the atmosphere, and the dropping is performed.