COATING METHOD AND APPARATUS
This application is a continuation of application Ser. No. 07/549,411, filed on Jul. 6, 1990, now abandoned. 5
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to method and apparatus for coating material such as the resist onto a matter 10 to be processed.
2. Description of the Related Art
The spin coating method is often employed for the resist-coating process in the course of manufacturing semiconductor devices. According to the spin coating 15 method, a spin chuck 2 is rotatably housed in a spin cup 1 which is opened outside at the top thereof, as shown in FIG. 3. A matter or wafer 3 to be processed is sucked and fixed on the spin chuck 2. Resist 5 is dropped onto the wafer 3 through a nozzle 4 while rotating the spin 20 chuck 2. The resist 5 on the wafer 3 is spread uniformly by centrifugal force to form a resist film 6 on the wafer 3.
Solvent is mixed in the resist 5 in this case to keep the resist viscous and the resist film 6 on the wafer 3 is 25 hardened while causing the solvent to be volatilized.
The wafer 3 on which the resist film 6 has been formed is then carried to the next baking process.
According to this coating method, however, rotation speed at the center area of the wafer 3 is different from 30 that at the circumferential area thereof. Therefore, the evaporation rate of the solvent in the resist 5 is different at the center and circumferential areas of the wafer 3. When the resist 5 dropped on the wafer 3 in the center thereof is spread toward the circumference thereof, the 35 amount of the solvent contained in the resist 5 is changed by increasing evaporation rate of the solvent along the radius of the wafer 3 due to the increase of the rotation speed, thereby change the viscosity of the resist 5 in the correspondence with the distance from the 40 center of the wafer 3. As shown in FIG. 4, therefore, the resist film 6 is hardened while leaving it thicker at the circumferential area of the wafer 3. As the result, the resist film 6 does not become uniform all over the wafer 3, thereby causing the productivity of semicon- 45 ductor devices to be lowered.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide coating method and apparatus capable of form- 50 ing a predetermined film uniform in thickness all over a matter to be processed.
According to the present invention, there can be provided a method comprising rotating a matter which is housed and processed in a closed chamber by a prede- 55 termined number of rotation, setting pressure in the chamber higher than the vapor pressure of a solvent mixed in a liquid which is to be coated on the matter, and causing the coating liquid to be dropped and spread on the surface of the matter. 60
According to the present invention, there can also be provided an apparatus for carrying out the coating method comprising a spin chuck provided on the top thereof a table on which a matter to be processed is mounted, and freely rotatably housed in a closed cham- 65 ber, a means provided with a nozzle in opposite to the table of the spin chuck and arranged in the closed chamber to supply coating liquid through the nozzle, a means
for supplying predetermined high pressure gas into the chamber, a pressure gauge for measuring pressure in the chamber, an exhaust means attached to the chamber, a means attached to the exhaust means to adjust the amount of gas exhausted, and a pressure controller for controlling the adjuster means responsive to signal applied from the pressure gauge.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate a presently preferred embodiment of the invention, and together with the general description given above and the detailed description of the preferred embodiment given below, serve to explain the principles of the invention.
FIG. 1 shows an example of the coating apparatus according to the present invention;
FIG. 2 is a characteristic graph showing the relation of the vapor pressure of solvent relative to temperature;
FIG. 3 shows the conventional coating apparatus; and
FIG. 4 is a sectional view showing a wafer on which resist film is formed non-uniform in thickness according to the conventional coating method.
DETAILED DESCRIPTION OF THE
FIG. 1 shows an example of the coating apparatus according to the present invention. Numeral reference 11 represents a closed chamber. The chamber 11 consists of a lower half 11a and an upper half lib freely detachably attached to the top of the lower half 11a through an O-ring 12. A spin chuck 13 is freely rotatably arranged in the chamber 11.
A semiconductor wafer 6 to be processed is sucked and fixed onto the top of the spin chuck 13. One end of a rotating shaft 13a of the spin chuck 13 is projected outside the lower half 11a through a seal member 14 and a motor 15 for rotating the spin chuck 13 is attached to this outside end of the rotating shaft 13a.
Gas and liquid exhaust pipes 16 and 17 are connected to the bottom of the lower half 11a of the chamber 11. Valves 16a and 17a for controlling amounts of gas and liquid exhausted are attached to the pipes 16 and 17, respectively. A probe 18a of a pressure gauge 18 is inserted into the chamber 11 through a side wall of the lower half 11a to measure atmospheric pressure in the chamber 11. The pressure gauge 18 and the valve 16a are electrically connected to a pressure controller 19. One end of a high pressure gas supply pipe 20 is inserted into the chamber 11 through the side wall of the lower half 11a at a position higher than the pressure gauge 18, while the other end thereof is connected to a high pressure gas supply source 21. Pressure gauge and regulator 20a and 20b are attached to the supply pipe 20.
One end of a coating liquid supply pipe 22 is inserted into the chamber 11 through the top of the upper half lib and opposed to the top of the spin chuck 13. A valve 22a for controlling the amount of coating liquid supplied is attached to the pipe 22. A coating liquid