JPS60149131A - Method of applying resist - Google Patents

Abstract

PURPOSE:To prevent striae from occurring on the surface of a resist film when a predetermined thickness of the resist is applied on the surface of a planar material while rotating the material at a predetermined speed, by stopping the rotation before the resist hardens. CONSTITUTION:A planar material 1 to be applied with resist is located on a spin head 2 for rotating the material 1, and fixed thereto by vacuum chucking or the like. Resist A is dropped from a nozzle 3 onto the surface of the stationary material 1. The head 2 is then driven to rotate the material at a low rotational speed of about 1,000rpm such that the resist A is diffused all over the surface. After that, the rotational speed is increased to about 5,000rpm. The resist is applied in a thickness slightly larger than the predetermined final thickness, and the rotation is stopped before the resist hardens so that the resist is allowed to harden in a stationary state. According to this method, no difference is produced in movement of the resist A between a part where it has hardened first and a part where it has no hardened yet on the surface of the material to be applied with 1. Therefore, striae can be prevented from occurring in the resist.

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 manufacturing semiconductor chips that form the main body of semiconductor devices,
Photolithography technology applied to wafer processing and manufacturing 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 frequently used, it is important to make the coating thickness uniform.

(C) Prior art and problems Figures 1, 2, and 3 are a plan view (al) and a side view (b) showing an example of the conventional method for applying resist.
, FIG. 4 is a diagram showing the time course, where 1 is the object to be coated, 2 is the spin head, 3 is the nozzle, and A is the resist 1S1.
, S2 is the rotation speed, a, b, c.

d indicates time.

The work order when applying 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 is fixed by, for example, a vacuum chuck, so that the object to be coated 1 is at rest. The resist A is dripped and supplied from the nozzle 3 onto the surface of the object 1 to be coated.Then, as shown in FIG.
1. For example, about 1100 Orp) L. Spread the resist A on the object 1 to be coated over the entire surface of the object 1 to be coated.

Next, as shown in FIG. 3, the object to be coated 1 is rotated at a predetermined high speed (rotation speed S2, for example, about 5000 rpm), and
The excess resist A is scattered around the object 10 to be coated, so that the thickness of the resist A on the object 1 is set to a predetermined value (for example, about 1 μm).

The time course of the operation of this embodiment is as shown in FIG. 4, where the resist A supply time a is about 2 seconds, the time 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, and the high speed rotation time d is about 20 seconds.

When the resist (all resist) 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 difference in height between the high and low points of the striae is approximately 300 to 500, and is 3 to 5% of the thickness of the resist A film of about 1 μm. 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 It has a drawback that leads to deterioration of characteristics.

(d) Object of the Invention In view of the above-mentioned conventional drawbacks, an object of the present invention is to rotate a flat plate-shaped object to be coated at a predetermined speed parallel to the surface of the object, and apply a resist to the surface in a predetermined manner. When applying the 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.

(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. This is achieved by a resist coating method characterized in that the rotation is stopped before the resist reaches the predetermined thickness and solidifies.

The solidification of the resist is due to the volatilization of the solvent contained in the resist, and the occurrence of the striae is caused by the microscopic unevenness of solvent volatilization in the resist on the surface of the object to be coated and the centrifugal force caused by the rotation. It is believed that this is due to the centrifugal force, so by stopping the rotation before the resist solidifies, it is possible to remove the centrifugal force and prevent the formation of striae.

(fl Embodiments of the Invention The embodiments of the invention will now be described with reference to the drawings. The same reference numerals refer to the same objects throughout the design.

FIGS. 5, 6, and 7 are a plan view Tal 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 shows the time course thereof. It is a diagram.

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

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 resist A is dripped and supplied from the nozzle 3 onto the surface of the object 1 to be coated. Thereafter, as shown in FIG. 6, the heavy object 1 to be coated is rotated at a low speed (rotational speed S1, for example, about 1001000 rp) by driving the spin head 2 (rotation speed S1, for example, about 1001000 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. Then, as shown in FIG.
2, for example, about 5000 rpm) is the same as the conventional example.

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, the predetermined thickness of the resist is set to be slightly larger than the final value, and the resist A is rotated at high speed before it reaches the predetermined thickness (for example, about 1.1 μm) and solidifies. stop.

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 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. This is thought to be due to a difference in movement to the resist between the previously solidified portion and the yet unsolidified portion on the surface of the object 1 to be coated. Therefore, by stopping the high-speed rotation before the resist A solidifies, it is possible to remove the centrifugal force and prevent the occurrence 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, the rotational speed S2 of the high-speed rotation should be increased to about 600 μm, for example.
It can be easily inferred from the conventional setting method of 32 that it is sufficient to use Orpm.

tg+ 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 in a predetermined manner. It is possible to provide a resist coating method that prevents striae from occurring on the surface of the coated resist film when coating the resist to a certain 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 drawings]

Figures 1, 2, and 3 are a plan view ta+ and a side view (bl
, Fig. 4 shows the time course, Fig. 5, Fig. 6
FIG. 7 is a plan view (al and a side view fbl,
FIG. 8 is a diagram showing the time course. In the drawing, l is the object to be coated, 2 is the spin head, 3 is the nozzle, A is the resist, Sl and S2 are the rotation speeds, a, b
, c, and d indicate time, respectively. Calculation 17 %2 Figure 3rd Layer System 4 Figure 5Il! I Ko 6 Figure 7 Figure 6

Claims (1)

[Claims] 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 is applied to the surface of the object to a predetermined thickness. A resist coating method characterized in that the rotation is stopped before the resist becomes solid and solidifies.