JPH0463532B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method of resist coating in photolithography technology.

(b) Background of the Technology In the production of semiconductor chips, which are the main components of semiconductor devices, photolithography technology, which is applied to wafer processing and the production of masks necessary for the processing, includes a resist coating process.

Resist coating generally involves a method of rotating a flat object to be coated, such as a wafer or a mask substrate, at a predetermined speed parallel to the surface of the object to be coated, and coating the surface with a resist to a predetermined thickness. Although the so-called spin treatment method is important, it is important to make the coating thickness uniform.

(c) Prior Art and Problems Figures 1, 2, and 3 are a plan view a and a side view b showing the order of an example of a conventional method for applying resist, and Figure 4 is a chronological diagram. A diagram showing the progress,
1 is the object to be coated, 2 is the spin head, 3 is the nozzle,
A is the resist, S1 and S2 are the rotation speeds, a, b,
c and d indicate time, respectively.

The work order when applying the resist A to a flat object 1 such as a wafer or a mask substrate by a spin process is as follows. That is, as shown in FIG. 1, the object to be coated 1 is placed on a spin head 2 that rotates the object to be coated and fixed by, for example, a vacuum chuck, and while the object to be coated 1 is stationary, the nozzle is 3, liquid resist A is dripped onto the surface of the object 1 to be coated. Thereafter, as shown in FIG. 2, the object 1 to be coated is rotated at a low speed (rotation speed S1, for example, 1000 rpm) by driving the spin head 2, and the resist A on the object 1 to be coated is spread over the entire surface of the object 1 to be coated. spread. Next, as shown in FIG.
at a predetermined high speed rotation (rotation speed S2, e.g. approx.
5000rpm), and remove the excess resist A from the object to be coated 1.
The resist A on the object to be coated 1 is scattered around the area.
The thickness is set to a predetermined final value (for example, about 1 μm) finally reached by the high-speed rotation.

The time course of the operation of this embodiment is as shown in FIG. 4, where the time a for supplying resist A is about 2 seconds, the time b from the end of supplying resist A to the start of low speed rotation is about 1 second, and the time c for low speed rotation. is about 2 seconds, and the high speed rotation time d is about 20 seconds.

When the resist A film coated by this method is closely observed, the presence of so-called striae, which is waviness in the rotational direction, is observed on the surface. The height of these striae (difference in height between high and low points) is approximately 300 to 500 Å,
It becomes 3 to 5% for a thickness of about 1 μm of the resist A film. The presence of such striae affects the pattern formed on a wafer or mask. For example, if the pattern is a line, the width of the line may be thick and thin, causing the semiconductor device to It has a drawback that leads to deterioration of characteristics.

(d) Object of the Invention In view of the above-mentioned conventional drawbacks, the object of the present invention is to rotate a flat plate-shaped object at a predetermined speed parallel to the surface of the object to be coated, and coat the surface with a resist to a predetermined thickness. It is an object of the present invention to provide a resist coating method that prevents the formation of striae on the surface of the coated resist film when coating the resist film.

(e) Structure of the Invention The above object is to provide a method in which a resist is supplied in liquid form to the surface of a plate-shaped object to be coated, when the resist is applied to the surface of the object to a predetermined thickness by rotating the object at a predetermined speed. The predetermined thickness is set to be larger than the final value of the thickness that the resist reaches due to the speed of rotation, and when the thickness of the resist reaches the predetermined thickness before reaching the final value. This is achieved by a resist coating method characterized by stopping the rotation.

The resist supplied to the surface of the object to be coated is
The solvent contained therein evaporates during the rotation, and solidification begins when the thickness approaches the final value. The occurrence of striae is thought to be due to a combination of uneven solidification due to microscopic unevenness of volatilization and centrifugal force due to rotation. Therefore, by stopping the rotation as described above, it is possible to remove the centrifugal force before the resist begins to solidify, thereby preventing the formation of striae.

(f) Embodiments of the invention Examples of the invention will be described below with reference to the drawings. The same reference numerals indicate the same objects throughout the figures.

5, 6 and 7 are a plan view a and a side view b showing the sequence of an embodiment of the method of applying a resist according to the present invention, and FIG. 8 is a diagram showing the time course thereof. be.

The work order when applying the resist A to the object to be coated 1 by the method of the present invention is the conventional example (Figs. 1 to 3).
The timing at which the final high-speed rotation is stopped is different from that shown in the figure.

That is, as shown in FIG. 5, the object to be coated 1 is placed on a spin head 2 that rotates the object to be coated and fixed by, for example, a vacuum chuck, and while the object to be coated 1 is stationary, the nozzle is 3 to resist A
is applied dropwise to the surface of the object to be coated 1. Thereafter, as shown in FIG. 6, the object to be coated 1 is rotated at a low speed (rotational speed S1, for example, approximately
1000 rpm), and the resist A on the object 1 to be coated is spread over the entire surface of the object 1 to be coated. Subsequently, as shown in FIG. 7, the process is similar to the conventional example until the object to be coated 1 is rotated at a predetermined high speed (rotational speed S2, for example, about 5000 rpm).

Due to this high-speed rotation, the excess resist A is scattered around the object 1 to be coated, and the thickness of the resist A on the object 1 to be coated becomes gradually thinner. However, on the other hand, the solvent contained in the resist A is evaporated. , solidification of the resist A begins when the thickness approaches approximately the final value. Therefore, in the method of the present invention, for example, when the final value is about 1 μm, the predetermined thickness is
1.1 μm, the predetermined thickness to be coated with resist A is determined to be slightly larger than the final value, and the high-speed rotation is stopped before the thickness of resist A reaches the final value. The time to stop is before the solidification of resist A begins.

The time course of the operation of this embodiment is as shown in FIG. 8, where the resist A supply time a is about 2 seconds, the time b from the end of resist A supply to the start of low speed rotation is about 1 second, and the low speed rotation time c is about 2 seconds, which is the same as in the case of FIG. 4, and the final high-speed rotation time d is about 3 seconds.

The inventor of the present application carefully observed the resist A film coated by this method and confirmed that almost no striae were observed on the surface. In the case of the conventional method, striae occur due to the combination of the above-mentioned microscopic unevenness of solvent volatilization during solidification of resist A and centrifugal force due to high-speed rotation during this time. , on the surface of the object to be coated 1, a resist A is placed between the previously solidified part and the not yet solidified part.
This is thought to be due to a difference in the movement of Therefore,
By stopping the high-speed rotation before the resist A solidifies, it is possible to remove the centrifugal force and prevent the formation of problematic striae.

Note that in the above example, the predetermined thickness of resist A is approximately
1.1 μm, but if this is set to about 1 μm as in the conventional example, it can be easily inferred from the conventional setting method of S2 that the rotation speed S2 of high-speed rotation should be increased to, for example, about 6000 rpm. It is.

(g) Effects of the Invention As explained above, according to the configuration of the present invention, a flat plate-shaped object to be coated is rotated at a predetermined speed parallel to the surface of the object to be coated, and a resist is applied to the surface of the object. It is possible to provide a resist coating method that prevents striae from occurring on the surface of the applied resist film when coating it to a predetermined thickness, thereby improving the quality of patterns formed on wafers, masks, etc. This has the effect of making it possible to improve the characteristics of the semiconductor device accordingly.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are a plan view a and a side view b showing the order of an example of a conventional method for applying a resist, and Figure 4 is a diagram showing the time course of the process. 6 and 7 are plan views showing the sequence of an embodiment of the method of applying a resist according to the present invention.
, side view b, and FIG. 8 are diagrams showing the time course. In the drawings, 1 is the object to be coated, 2 is the spin head, 3 is the nozzle, A is the resist, S1 and S2 are the rotational speeds, and a, b, c, and d are the times, respectively.

Claims (1)

[Claims] 1. When a flat plate-shaped object to be coated is rotated at a predetermined speed and a resist is applied to the surface of the object to a predetermined thickness, the resist supplied in liquid form to the surface of the object is rotated at a predetermined speed. The predetermined thickness is set to be larger than the final value of the thickness to be reached, and the rotation is stopped when the thickness of the resist reaches the predetermined thickness before reaching the final value. Resist application method.