JPH0556847B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a resist coating method in a resist process, particularly to a resist coating method using a spin coating method.

<Prior Art> In a resist coating step in a resist process, it is necessary to uniformly coat a photoresist on the wafer surface after pretreatment, and a conventional resist coating method includes, for example, a spin coating method.

In this spin coating method, the wafer is chucked in a vacuum and rotated at high speed, and the photoresist dropped onto the wafer surface from a nozzle is uniformly applied to the surface. That is, Fig. 2 shows the time T and the rotation speed N.
As shown in the relationship, the process consists of a first process A in which the resist is dropped and rotated at low speed, and a second process B in which the resist is shaken off by rotating at high speed. Here, as shown in FIG. 3, the coating film thickness d of the photoresist and the spinner rotational speed N are in a relationship such that the film thickness d becomes thinner as the rotational speed increases.
Therefore, according to this method, the resist is rotated at low speed in the first step A and the dropped resist is maintained at a predetermined thickness and spread over the entire wafer surface, and then the resist is rotated at high speed in the second step B. The overall resist film thickness is uniformly formed to a required thickness.

<Problems to be Solved by the Invention> However, in such a conventional resist coating method, since the rotation is always at a constant speed during the first step, the rotation speed increases toward the outer edge of the wafer. As the speed increased, the resist film thickness had to become thinner. As a result, the resist cannot overcome the steps (protrusions) existing at the outer edge, and at a constant rotational speed, the resist tends to flow in the direction in which it flows easily. There was a risk that the resist would not be applied to some Y areas or that the resist would be uneven.

<Means for Solving the Problems> A resist coating method according to the present invention includes the steps of: after dropping a resist onto a wafer surface, rotating the wafer at a first rotation speed, then decreasing the rotation speed;
Next, the wafer is configured to be rotated at a second rotation speed higher than the first rotation speed.

<Operations and Effects> According to the resist coating method according to the present invention, the resist dropped onto the wafer surface is spread over the entire surface by rotating the wafer at a first rotation speed, and then at a second rotation speed higher than this. The resist is rotated at a rotational speed of 2 to form a uniform resist coating thickness to a required thickness. In this case, the wafer is rotated at the first rotation speed and then the rotation speed is reduced. As a result, the film thickness of the dropped resist is maintained at an appropriate thickness even at the outer edge of the wafer, and it is possible to overcome the level difference on the wafer surface, so that the resist is distributed over the entire surface.

<Example> An example of the present invention will be described below with reference to FIG.

As shown in the figure, the resist coating method according to the present invention includes a first step A and a subsequent second step B.
It consists of and. In the first step A, the wafer is rotated at a first rotational speed _N1 while dropping a predetermined amount of photoresist using a nozzle or the like onto the substantially central portion of the wafer surface after pretreatment (cleaning);
Gradually reduce this rotation speed. Note that it is not necessary to drop the resist over the entire period of time, and the resist may be dropped before the rotation starts. As a result, the film thickness of the resist on the wafer increases as the speed decreases, so even if it moves to the outer edge of the wafer due to centrifugal force, the film thickness is larger than in the past.
It rides over steps or protrusions and evenly spreads over the entire wafer surface.

Next, in the second step B, the resist coated on the entire wafer as described above has a non-uniform thickness in the radial direction and is large, so
The wafer is rotated for a predetermined time at a second rotational speed _N2 higher than the first rotational speed _N1 . As a result, the resist coating film is formed to have a uniform thickness over the entire wafer surface and to a required predetermined thickness.

Note that after resist application, a predetermined resist process such as soft baking is performed, followed by an etching process.

Further, in the above embodiment, the first rotation speed
N ₁ and the second rotational speed N ₂ are each, for example
The speeds are 1000 rpm and 5000 rpm, and the times of A and B are changed depending on the resist film thickness, etc., but are, for example, 10 seconds and 30 seconds, respectively.

<Effects> As described above, according to the present invention, even if the wafer surface has a large step, the resist can be applied uniformly and evenly over the entire surface of the wafer. As a result, yield can be improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the time and rotation speed of each step in an embodiment of the resist coating method according to the present invention, and FIG. 2 is a graph showing the relationship between the time and rotation speed of each step in a conventional method. , FIG. 3 is a graph showing the relationship between spinner rotation speed and resist coating thickness, and FIG. 4 is a plan view of a wafer showing defects caused by the conventional method.

Claims (1)

[Claims] 1. While or after dropping the resist on the wafer surface, the wafer is rotated at a first rotation speed, and then the rotation speed is decreased, and then,
A resist coating method comprising rotating the wafer at a second rotation speed higher than the first rotation speed.