JPH0797547B2 - Resist coating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a resist coating method.

(Prior Art) For example, in the manufacture of a semiconductor device, a circuit pattern is transferred using a precision photo transfer technique, and therefore there is a step of uniformly coating a semiconductor wafer with a resist.

As described above, as a method for coating a semiconductor wafer with a resist, by supplying the resist near the central portion of the semiconductor wafer and rotating the semiconductor wafer at a high speed,
A general method is spin coating in which a resist is diffused over the entire surface of a semiconductor wafer.

(Problems to be Solved by the Invention) However, in the conventional resist coating method described above, the resist is shaken off from the center to the periphery by centrifugal force, and in the process of forming a constant film thickness Due to the difference in peripheral speed, the volatilization rate (volatilization amount) of the resist solvent in the atmosphere is different, the apparent viscosity of the resist is different, and the resist film thickness around the semiconductor wafer is different from the resist film thickness at the center of the semiconductor wafer. There is a problem that it becomes thicker and the resist film thickness becomes non-uniform. Such a difference in resist film thickness becomes larger particularly in a semiconductor wafer having a large diameter, but in recent years, the semiconductor wafer tends to have a larger diameter, which may cause a particularly serious problem.

The present invention has been made in consideration of such conventional circumstances, and an object thereof is to provide a resist coating method capable of uniformly coating a substrate to be processed such as a semiconductor wafer with a resist.

[Structure of the Invention] (Means for Solving Problems) That is, according to the present invention, a resist whose temperature is adjusted to a temperature higher than the temperature of the substrate to be processed is supplied to the central portion of the substrate to be processed and / or in the vicinity thereof. And a step of rotating the substrate to be processed.

(Operation) In the resist coating method of the present invention having the above-mentioned configuration, the resist to be processed is supplied to the central portion of the substrate to be processed and / or the vicinity thereof by controlling the temperature of the resist to a temperature higher than the temperature of the substrate to be processed. The temperature of the central part of the substrate is higher than that of the peripheral part.

Therefore, the difference in volatilization rate of the resist solvent due to the difference in peripheral speed is offset by the temperature difference, and the volatilization rate is made uniform in each part of the substrate to be processed, so that the resist can be coated uniformly over the entire surface of the substrate to be processed. it can.

(Example) An example in which the method of the present invention is applied to resist coating of a semiconductor wafer will be described below with reference to the drawings.

In the method of this embodiment, first, as shown in FIG. 1A, the semiconductor wafer 1 is placed on a holding table 2 of a resist coating apparatus, and the semiconductor wafer 1 is suction-held by, for example, a vacuum chuck.

Next, as shown in FIG. 1B, a resist 3 having a temperature higher than that of the semiconductor wafer 1 is dropped on the central portion of the semiconductor wafer 1.

After that, as shown in FIG. 1C, the holding table 2 and the semiconductor wafer 1 are rotated at a rotation speed of, for example, tens of thousands of revolutions per minute to diffuse the resist 3 over the entire surface of the semiconductor wafer 1.

The temperature of the resist 3 is room temperature and the semiconductor wafer 1
It is necessary to appropriately select the temperature depending on the temperature. For example, the graph in Figure 2 shows a room temperature of 21.6 ° C and a semiconductor wafer temperature of 21.5 ° C.
The results of measuring the relationship between the resist temperature and the variation in film thickness under the conditions of
The resist temperatures of e, f, g, and h are 16.2 ° C and 1 respectively.
8.1 ℃, 19.9 ℃, 20.9 ℃, 21.3 ℃, 21.8 ℃, 22.7 ℃, 24.
The case of 4 ° C is shown.

As indicated by the curve g in this graph, under the above conditions, a substantially uniform film thickness can be obtained at a resist temperature of about 22.7 ° C. If the resist temperature is raised too high, the curve h
As shown by, the thickness of the central portion of the semiconductor wafer 1 becomes thicker. This is because the difference in volatilization rate of the resist solvent due to the difference in peripheral speed causes the difference in volatilization rate of the resist solvent due to the difference in temperature.

FIG. 3 shows another embodiment method. In this embodiment method, a temperature gradient is formed on the holding table 2 of the resist coating apparatus so that the temperature is high in the central part and low in the peripheral part. Place a temperature control mechanism. Note that such a temperature control mechanism can be realized, for example, by disposing the heater 4 only in the central portion of the holding table 2 and heating only the central portion of the holding table 2 to a predetermined temperature by the heater 4. it can.

Then, as shown in FIG. 3A, first, the semiconductor wafer 1 is placed on a holding table 2 in which a temperature gradient is formed so that the temperature is high in the central part and low in the peripheral part in advance. The semiconductor wafer 1 is suction-held by a vacuum chuck or the like.

Next, as shown in FIG. 3 (b), the dist 3 is dropped on the central portion of the semiconductor wafer 1.

After that, as shown in FIG. 3C, the holding table 2 and the semiconductor wafer 1 are rotated at a rotation speed of, for example, tens of thousands of revolutions per minute, and the resist 3 is diffused over the entire surface of the semiconductor wafer 1.

That is, in this embodiment, the holding table 2 is provided with a temperature control mechanism that forms a temperature gradient so that the temperature is high in the central part and low in the peripheral part, and the semiconductor wafer is the same as in the above-described embodiments. 1 The difference in the volatilization rate of the resist solvent due to the difference in the peripheral speed of each part is offset by the temperature difference, and the volatilization rate of the resist solvent is made uniform in each part.
The resist 3 can be uniformly coated over the entire surface. The heating temperature set by the heater 4 needs to be appropriately selected as in the above-described embodiment.

It should be noted that in these embodiments, an example in which the temperature of the semiconductor wafer 1 is adjusted by adjusting the temperature of the resist 3 and an example in which the temperature of the semiconductor wafer 1 is adjusted by adjusting the temperature of the holding table 2 have been described. The temperature of the semiconductor wafer 1 can be adjusted by adjusting the temperature of the atmosphere, such as by blowing a gas having a different temperature from above, or a combination of these methods can be used.

[Effects of the Invention] As described above, according to the resist coating method of the present invention, it is possible to uniformly coat a resist on a substrate to be processed such as a semiconductor wafer.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a resist coating method according to an embodiment of the present invention, FIG. 2 is a graph showing a relationship between resist temperature and variations in film thickness, and FIG. 3 is a resist coating method according to another embodiment. It is an explanatory view shown. 1 ... semiconductor wafer, 2 ... holding table, 3 ... resist,
4 ... Heater.

Claims (1)

[Claims] 1. A step of supplying a resist, the temperature of which is adjusted to a temperature higher than the temperature of the substrate to be processed, to a central portion of the substrate to be processed and / or the vicinity thereof, and a step of rotating the substrate to be processed. A resist coating method characterized by the above.