Semiconductor device manufacturing: process – Radiation or energy treatment modifying properties of... – Ionized irradiation
Reexamination Certificate
1999-09-08
2001-07-17
Booth, Richard (Department: 2812)
Semiconductor device manufacturing: process
Radiation or energy treatment modifying properties of...
Ionized irradiation
C438S905000, C438S906000, C438S907000
Reexamination Certificate
active
06261977
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for reventing corrosion, and more particularly, to a method for preventing an electrostatic chuck from being corroded during a cleaning process.
DESCRIPTION OF THE PRIOR ART
In semiconductor processing, HDPCVD (high density plasma chemical vapor deposition) is performed in a plasma vacuum chamber to form a thin film on the semiconductor wafer by depositing. But the reactive gas also deposits on the inner wall of the plasma vacuum chamber causing unwanted buildup. Therefore, most plasma vacuum chambers come equipped with self-cleaning devices that clean the chamber. This improves the yield of the products on the process and prolongs the service life of the chamber.
Please refer to FIG.
1
.
FIG. 1
is schematic diagram of the electrostatic chuck
10
according to the prior art. The electrostatic chuck
10
is located at the bottom of a plasma vacuum chamber (not shown) for placing a semiconductor wafer. The electrostatic chuck
10
comprises a metallic circular plate
14
functioned as a lower electrode during the HDPCVD process, and an insulating layer
12
covering the surface of the metallic circular plate
14
for electrically isolating the semiconductor wafer
10
and the metallic circular plate
14
. The electrostatic chuck
10
contains a plurality of vent holes
17
through which a cooling gas passes to the semiconductor wafer and a plurality of channels
18
arranged in a radiating pattern for guiding the cooling gas.
During the HDPCVD process, the inner wall of the plasma vacuum chamber is also being deposited, and this deposited layer increases with increased frequency of use of the plasma vacuum chamber. So it is necessary to clean the plasma vacuum chamber at a certain accumulated thickness properly to maintain the quality of the process and to prolong the service life of the plasma vacuum chamber. In the cleaning process of the plasma vacuum chamber, a fluorine-contained gas is injected into the plasma vacuum chamber for performing a cleaning process to remove the chemical layer from the inner wall of the plasma vacuum chamber. If the product of the HDPCVD process is related to silicon oxide, NF
3
gas can be used as the plasma reactive gas. But in the cleaning process, the plasma gas is subject to corrode the electrostatic chuck
10
reposed in the plasma vacuum chamber. Therefore, before the cleaning process, measures to safeguard the electrostatic chuck need to be taken.
Please refer to FIG.
2
.
FIG. 2
is a schematic diagram of the method of preventing the electrostatic chuck
10
from being corroded during the cleaning process according to the prior art. In the method of the prior art, a ceramic shutter
16
made of Al
2
O
3
is reposed on the electrostatic chuck
10
before the cleaning process is performed to isolate it from the fluorine-contained gas and to prevent the surface of the electrostatic chuck
10
from being corroded caused by the fluorine ions. But since the ceramic shutter
16
rests on the electrostatic chuck
10
by relying only on the gravitational force, thereby, fluorine ions can probably flow into the gap between the ceramic shutter
16
and the insulating layer
12
to corrode the periphery of the electrostatic chuck
10
.
For a long period of time under the condition of corrosion, the difference in flatness of the electrostatic chuck
10
at the periphery and at the center portion will become significant. As a result, the periphery of the semiconductor wafer
10
may become suspended from the surface of chuck, thereby, the semiconductor wafer may not be able to be well fixed on the electrostatic chuck
10
, leading to an unstable film's quality. For example, during the HDPCVD process, the cooling gas passing through the vent holes
17
and channels
18
of the electrostatic chuck
10
is not evenly distributed over the back face of the semiconductor wafer, so the temperature in different areas of the semiconductor wafer will not be the same, thus leading to inconsistency of the deposition rate.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide a method for preventing an electrostatic chuck from being corroded during a cleaning process to resolve the above-mentioned problem.
In a preferred embodiment of the present invention, the method for preventing an electrostatic chuck from being corroded during a cleaning process, the electrostatic chuck being locating at the bottom of a plasma vacuum chamber for placing a semiconductor wafer and comprising a conductive substrate functioned as a lower electrode in a plasma process, and an insulating layer on the conductive substrate to electrically isolate the semiconductor wafer and the conductive substrate, the cleaning process involving a plasma process in which a fluorine-contained gas is injected into the plasma vacuum chamber, the method comprising:
placing a ceramic shutter on the electrostatic chuck during the cleaning process and applying a DC (direct current) voltage to the conductive substrate and the ceramic shutter which causes the ceramic shutter and the electrostatic chuck tightly stick together through an electrostatic force such that the fluorine-contained gas cannot corrode the insulating layer under the ceramic shutter through the gap between the ceramic shutter and the electrostatic chuck.
It is an advantage of the present invention that the ceramic shutter can stick on the electrostatic chuck
10
tightly to prevent the fluorine-contained gas from flowing into the gap between the ceramic shutter
16
and the electrostatic chuck
10
.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.
REFERENCES:
patent: 5606485 (1997-02-01), Shamouilian et al.
patent: 5870271 (1999-02-01), Herchen
Liu Chih-Chien
Tsai Cheng-Yuan
Wu Juan-Yuan
Booth Richard
Gurley Lynne
Hsu Winston
United Microelectronics Corp.
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