Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of...
Reexamination Certificate
2000-12-13
2002-05-07
Gmyka, Alexander G. (Department: 2812)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
C118S052000, C118S631000
Reexamination Certificate
active
06383948
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coating film forming apparatus and a coating film forming method for coating, for example, a semiconductor wafer, and a processing substrate such as an LCD substrate, an exposure mask and the like with liquid, which is obtained by dissolving resin and so on, particularly a resist liquid to form a film of this liquid.
2. Description of the Related Art
A mask for forming a circuit pattern on a surface of a semiconductor wafer, and that of a processing substrate such as an LCD substrate and like is obtained by coating the substrate surface with a resist liquid, irradiating the resist surface with light, an electron beam, or an ion beam and developing the resultant. As a resist liquid coating method, a spin coating method is mainly used. This method, for example, as shown in
FIG. 33
, a substrate, e.g., a semiconductor wafer (hereinafter referred as “wafer”) W is absorbed and held on a spin chuck
11
having a vacuum absorbing function, a resist liquid
13
is dropped on the central portion of wafer W from a nozzle
12
, thereafter, the wafer W is rotated at high speed, whereby diffusing the resist liquid
13
to the entirety of wafer W by a rotational centrifugal force, so that a substantially uniform resist film is formed over the entire surface of wafer W.
There has been a growing trend in recent years to fine the wiring width of the circuit pattern, and it is required that a resist film be thinned since the wiring width of the circuit is proportional to the thickness of the resist film and an exposure wavelength. In the spin coating method, an increase in the rotational speed of wafer W allows the resist film to be thinned. For this reason, for example, 8-inch wafer W is rotated at high speed of 200 to 4000 rpm.
However, this spin coating method has the following problems to be solved.
First, according to this method, when the wafer W is upsized, peripheral speed at an outer peripheral portion is increased, so that air turbulence is generated. The thickness of resist film is easily varied by this air turbulence to reduce uniformity of the resist film thickness, and this causes a reduction in exposure resolution. For this reason, it is difficult to obtain a fixed coating thickness in the case of the film thickness of 0.4 &mgr;m or less, and there is a limitation in the manufacture of about more than some giga-semiconductors naturally.
Next, according to this method, in the process in which the resist liquid is spread to the peripheral edge portion from the central portion of wafer W, solvents contained in the resist liquid are sequentially evaporated. This makes a difference in viscosity of the resist liquid along the diffusion direction, to cause a possibility that the thickness of resist film formed between the central portion and the peripheral edge portion will differ.
Moreover, according to this method, since the wafer W is rotated at high speed, the amount of resist liquid, which is spread from the peripheral edge portion of wafer W and becomes useless, is large. As one example, it is clear that only 10% or less of the amount of resist liquid supplied onto the wafer W contributes to formation of resist liquid film.
Furthermore, though there is a necessity to rotate the wafer W in a cup to receive the splashing resist liquid, there is a possibility that the resist liquid adhered onto the cup will form particles with which the wafer W will be polluted. For this reason, the cup must be frequently cleaned.
Still furthermore, according to this method, the outside area of the circuit forming area of wafer W is also coated with the resist liquid. If the resist liquid is left in this area, this will cause occurrence of particles in the later process. For this reason, the resist liquid of this area must be removed by a dedicated device, which is called edge remover, just after the resist liquid coating process.
As a method in place of the aforementioned spin coating method, the inventors of this invention have reviewed the following method (hereinafter referred to as “one-stroke drawing type”):
Specifically, as shown by a solid line in
FIG. 34
, the nozzle
12
for discharging the resist liquid
13
onto the surface of wafer W and the wafer W are relatively reciprocated in an X direction as being intermittently feeding by a predetermined pitch in a Y direction to coat the wafer W with the resist liquid in the so-called one-stroke drawing manner. In this case, it is preferable that the portion other than the circuit forming area of wafer W be covered with a mask in order to prevent the resist liquid from being adhered onto the peripheral edge of wafer W and the rear surface. In this method, since the wafer W is not rotated, the aforementioned problems are solved and the resist-liquid coating can be performed without wasting the resist liquid.
In the coating method of the one-stroke drawing type, a diameter of a discharge hole of the nozzle
12
is formed considerably thinly, that is, about 10 &mgr;m to 200 &mgr;m in order to reduce the thickness of the resist film. When the resist liquid
13
is discharged from the nozzle
12
and collides with the wafer
12
, the resist liquid
13
expands wider than the discharge diameter as shown in, for example,
FIG. 35
, with the result that the discharged resist liquids
13
are connected to one another and a liquid film of the resist liquid
13
is formed on the entirety of the surface of the wafer W.
However, when the coating of the resist liquid
13
is made from a coating start point, which is shown by Ya in
FIG. 36
, to a coating end point, which is shown by Yb, in a direction shown by an arrow in the figure, there is confirmed occurrence of a phenomenon in which the film thickness at point Ya becomes larger than the film thickness at point Yb. Depending on the kind of resist liquid
13
, the film thickness at point Ya becomes conspicuously high in some cases.
The reason can be considered as follows:
Specifically, the resist liquid
13
is drawn to the pre-coated area shown by slanted lines of
FIG. 20
by the above-mentioned expansion of the resist liquid
13
, which is caused by the collision with the wafer W. In this way, the film thickness at point Ya becomes large.
While, in order to obtain a necessary film thickness, parameters such as a discharge quantity of resist liquid, discharge pressure, scanning speed of coating liquid nozzle (moving rate in an X direction), an index pitch (intermittent moving distance) of wafer W, and so on are appropriately set, coating of resist liquid is performed on the condition, and drying is performed, and then the thickness of the resist film is measured. Then, the discharge pressure is controlled based on the measurement result. However, the work for controlling the parameters by trial and error is cumbersome. In addition, when the solid content quantity in the resist liquid varies, the amount of solvent, which is volatilized and disappears, varies even if the coating with the same amount is carried out, with the result that the film thickness of the resist is changed. Moreover, the range for changing the values of the respective parameters is determined to some degree in accordance with hardware configuration. For this reason, regarding a case in which the film thickness is doubled, it is impossible to deal with such a case by a method in a value of one parameter is simply doubled. Namely, the plurality of parameters must be controlled. For the above-mentioned reason, a so-called condition derivation work is complicated and needs much time, causing a problem in which smooth activation of the apparatus is prevented.
SUMMARY OF THE INVENTION
It is an object of the present invention is to provide a coating film forming apparatus, which is capable of obtaining a stable film thickness over a substrate surface by dividing a coating area of the substrate, and relates to a coating film forming method.
Another object of the present invention is to provide a coating film forming apparatus, which is capable of formi
Akimoto Masami
Esaki Yukihiko
Ishizaka Nobukazu
Kitano Takahiro
Koga Norihisa
Gmyka Alexander G.
Rader & Fishman & Grauer, PLLC
Tokyo Electron Limited
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