Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2000-06-21
2002-06-11
Utech, Benjamin L. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C134S006000, C134S021000
Reexamination Certificate
active
06403489
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The invention relates to a preventive maintenance of etching equipment for the semiconductor technology. More particularly, the invention relates to a method for removing polymer stacked on a lower electrode within an etching reaction chamber.
B. Description of the Related Art
Along with progress of the fine processing technology, the degree of integration and the performance of semiconductor devices is gradually increasing. In the semiconductor manufacturing process, the primary function of the etching process is to remove layers on which there are no photoresist layers in the photolithography process, such that the mask patterns are transferred to the layers. In the above-mentioned etching process, there are two main methods: (1) the process of wet etching performed by a chemical reaction and (2) the process of dry etching performed by physical mechanisms. Compared with the process of wet etching, the process of dry etching takes a more important part in the fine processing technology due to anisotropic properties. In the physical mechanism of the process of dry etching, plasma is utilized to dissociate molecules of a reaction gas to reactive ions, and then the layers made of materials such as SiO
2
, Si
3
N
4
, poly-Si, or Al alloy are removed by the bombardment of the reactive ions.
FIG. 1
is cross-sectional view showing the structure of etching equipment for performing the process of dry etching. Referring to
FIG. 1
, etching equipment
1
for performing the process of dry etching consists of an upper electrode
10
, a lower electrode
20
, a radio frequency generator
30
, and a reaction chamber
70
. In general, the upper electrode
10
is connected to the wall
40
of the reaction chamber
70
, and both are grounded. In addition, the radio frequency generator
30
is connected to the lower electrode
20
, and a wafer
50
to be etched is placed on the lower electrode
20
. Referring to
FIG. 2
, the wafer
50
includes a substrate
51
on which a conductive, semiconductive, or insulating layer
52
is formed. A patterned photoresist layer
53
has been provided on the surface of the layer
52
by the process of photolithography before the wafer
50
is transferred into the reaction chamber
70
. During the process of dry etching, a reaction gas (not shown) for carrying out dry etching is supplied into the reaction chamber
70
through a supply tube
60
, and then is dissociated into ions by the radio frequency generator
30
to form a plasma. After the formation of the plasma within the reaction chamber
70
, the plasma ions are accelerated by the electric potential difference between the upper electrode
10
and lower electrode
20
so as to bombard the exposed part
54
of the layer
52
formed on the surface of the substrate
51
. Afterwards, the reaction product, as a result of the bombardment, is expelled through an exhaust tube
80
by a vacuum system (not shown) connected to the exhaust tube
80
. Therefore, the transfer of the pattern from the photoresist layer
53
to the layer
52
is achieved.
In the manufacturing process of semiconductor devices, a layer made of silicon dioxide is usually applied as the insulating layer to be etched and the reaction gas for carrying out dry etching usually contains carbon and fluorine atoms. As a result, a polymer (not shown) including carbon and fluorine is produced by the chemical reaction between the reactive ions dissociated from the reaction gas and the silicon dioxide of the insulating layer. A part of the polymer stacks on the wall
40
of the reaction chamber
70
and the peripheral surface
90
of the lower electrode
20
. After a period of time, the stacked polymer becomes the source of particle contamination and affects the yield of the wafer
50
. In order to prevent the polymer from being stacked on the lower electrode
20
so as to make the process of dry etching effective, it is necessary to perform preventive maintenance of the reaction chamber
70
during intervals.
FIG. 3
is a plane view showing the structure of the lower electrode
20
. Referring to
FIG. 2
, the polymer
100
adheres to the peripheral surface
90
of the lower electrode
20
in the form of a lump. The conventional preventive maintenance of the lower electrode
20
is to remove the polymer
100
adhering to the surface by the process of wet cleaning as described in the following.
At the beginning of the conventional preventive maintenance, the temperature of the lower electrode
20
is set to a room temperature. Then, the reaction chamber
70
is repeatedly cleaned several times by a pump/purge cleaning method. Next, the reaction chamber
70
is opened after the internal pressure of the reaction chamber
70
is up to atmospheric pressure by supplying nitrogen gas through the supply tube
60
. Afterwards, using Cleaner 5060 (having as a main component C
6
F
14
), produced by the 3M corporation, as a cleaning solution, the surface of the lower electrode
20
is wiped several times. Furthermore, using a scraper (not shown), the polymer
100
adhering to the peripheral surface
90
of the lower electrode
20
is removed. Finally, the surface of the lower electrode
20
is wiped several times again by using Cleaner 5060 produced by the 3M corporation.
According to practical operations of the conventional preventive maintenance, it is necessary to use a large amount of Cleaner 5060 because the conventional method is not effective to remove the polymer
100
adhering to the peripheral surface
90
of the lower electrode
20
. Moreover, it takes a long time to finish the conventional preventive maintenance due to the use of the scraper. The scraper also makes the surface of the lower electrode
20
worn and damaged resulting in a shortening of its lifespan, and therefore affects the stability of the etching process.
SUMMARY OF THE INVENTION
In view of the above problems and disadvantages, it is therefore an object of the invention to provide a method for removing polymer stacked on a lower electrode within an etching reaction chamber without the use of an additional cleaning solution or scraper.
The invention is an improvement over the conventional preventive maintenance of a lower electrode. Using the invention, the polymer stacked on the lower electrode is effectively removed, the cleaning time is shortened, the quantity of the required cleaning solution is decreased, and the lifespan of the lower electrode is increased.
According to the invention, a method for removing polymer stacked on a lower electrode within an etching reaction chamber comprises the following steps: setting a first temperature of the lower electrode in the range from −10° C. to 0° C., preferably 0° C.; cleaning the reaction chamber 5 to 50 times, preferably 20 times, by a pump/purge cleaning method; supplying at least one gas selected from a group consisting of nitrogen and an inert gas into the reaction chamber such that the internal pressure is equal to atmospheric pressure; opening the reaction chamber; keeping the reaction chamber open and the temperature of the lower electrode at 0° C. for 5 to 15 minutes, preferably 10 minutes; wiping the surface of the lower electrode with a piece of clean cloth; setting a second temperature of the lower electrode in the range from 20 to 30° C., preferably 25° C.; and wiping the surface of the lower electrode several times by using at least one cleaning solution selected from a group consisting of de-ionized water, isopropanol (IPA), ethanol, a solution of hydrogen peroxide in water, and Cleaner 5060 (having as a main component C
6
F
14
) produced by the 3M corporation.
REFERENCES:
patent: 5180467 (1993-01-01), Cook et al.
patent: 5403453 (1995-04-01), Roth et al.
patent: 5486235 (1996-01-01), Ye et al.
patent: 5676759 (1997-10-01), Ye et al.
patent: 5952060 (1999-09-01), Ravi
patent: 6039834 (2000-03-01), Tanaka et al.
patent: 6079426 (2000-06-01), Subrahmanyam et al.
patent: 6125859 (2000-10-01), Kao et al.
Kao Kuo-tsai
Lai Shih-chi
Wu Kuang-yung
Yuan Tien-min
Anderson Matthew
Bacon & Thomas
Mosel Vitelic Inc.
Utech Benjamin L.
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