Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-04-21
2003-06-03
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S680000, C438S682000, C438S683000, C438S773000, C438S775000
Reexamination Certificate
active
06573178
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method for a semiconductor device and a semiconductor manufacturing apparatus, and more particularly, to a semiconductor device manufacturing method utilizing a CVD (Chemical Vapor Deposition) film formation process and a semiconductor manufacturing apparatus utilizing a CVD film formation process.
2. Description of the Related Art
In a processing for manufacturing a semiconductor device, a film is formed on a substrate to be processed such as a semiconductor silicon wafer by a chemical vapor deposition (CVD) method.
A wafer processing will be explained below with reference to
FIGS. 3 and 4
.
In a state where a load lock chamber
1
and a reaction furnace
2
are under the atmospheric pressure, a boat
10
is lowered (unloaded) from the reaction furnace
2
to the load lock chamber
1
. In the state where the boat
10
is lowered, a predetermined number of wafers
11
are mounted on the boat
10
by a substrate transfer apparatus (not shown) (step
41
).
A temperature in the reaction furnace
2
is maintained at a film forming temperature during operation. The boat
10
is hoisted by a boat elevator (not shown), and the wafers
11
are brought (loaded) into the reaction furnace
2
(step
42
).
An interior of the reaction furnace
2
is evacuated into vacuum by an evacuating device
9
(step
43
), reaction gas is introduced into the reaction furnace
2
through gas introducing lines
7
and
8
, and films are formed on the wafers
11
(step
44
).
After the film forming processing is completed, the pressure in the reaction furnace
2
is brought back to the atmospheric pressure (step
45
), and the boat
10
is unloaded and pulled into the load lock chamber
1
by the boat elevator (not shown) (step
46
). In the load lock chamber
1
, the boat
10
is cooled (step
47
), the wafers
11
are removed by the substrate transfer apparatus (not shown) (step
48
).
When the wafer removal is completed, unprocessed wafers are further mounted on the boat
10
and then, the load lock chamber
1
is once evacuated into vacuum by a vacuum evacuating device
13
to eliminate moisture and oxygen in the air. Thereafter, nitrogen gas is introduced from a gas purge nozzle
12
, the pressure in the load lock chamber
1
is brought back to the atmospheric pressure which is substantially the same as the pressure in the reaction furnace
2
. Next, the boat
10
is loaded into the reaction furnace
2
, and the processing is continued.
If a film, e.g. an SiN film is formed on a substrate to be processed such as a wafer and a glass substrate by a CVD apparatus, by-products of reaction are adhered and deposited on a wall surface of the reaction furnace, thereby forming the film. This deposited film grows whenever the substrate processing is repeated, and when a thickness of the film reaches a predetermined value, cracking and peeling are caused to generate particles. The particles float in the reaction furnace and adhere to the substrate to be processed. When the number of particles is increased and the number of particles adhering to the substrate to be processed is increased, detrimental effects that yield is lowered and quality of product is deteriorated are generated. Especially in the case of a Si
3
N
4
film whose film thickness generated by one time processing is equal to or greater than 1000 Å, this phenomenon becomes remarkable. It is conceivable that the Si
3
N
4
film is subjected to a self cleaning which is usually carried out in the case of polycrystalline film. However, in the case of the Si
3
N
4
film, since particles are generated when the deposited film thickness reaches 1 &mgr;m, it is necessary to carry out the cleaning whenever film thickness of the deposited Si
3
N
4
film reaches 1 &mgr;m. Therefore, a frequency of the cleaning is higher than that of the polycrystalline film, and this causes inconvenience that quartz member is degraded due to the cleaning gas.
It is considered that the cracking of the reaction by-product deposited film is generated if residue stress at the time of deposited film formation is increased together with growth of the film, and thermal stress is generated due to difference in thermal expansion between the deposited film and an outer tube
5
and between the deposited film and an inner tube
6
, and these stresses exceed tolerance limits (mechanical disruptive strength of the deposited film). The cracking of the deposited film progresses into film peeling in due time, but particles are generated even when the deposited film cracking is generated. The particle at that time is extremely fine as small as about 0.1 to 0.2 &mgr;m.
Further, it is considered that the cracking of the deposited film is generated during a semiconductor manufacturing process. When the thickness of the deposited film reaches about 1 &mgr;m, the number of particles adhering to a wafer becomes 100/wafer or greater, and the number of the particles is never reduced thereafter.
For this reason, it is necessary to eliminate the deposited film in order to maintain the number of particle adhering to a wafer at a level equal to or lower than a predetermined value, and the inner tube
6
and the outer tube
5
constituting the reaction furnace
2
was cleaned before the thickness of the deposited film reaches about 1 &mgr;m.
When constituent members of the reaction furnace
2
such as the outer tube
5
and the inner tube
6
are cleaned, operation of the semiconductor manufacturing apparatus is stopped and the reaction furnace
2
is disassembled. Therefore, if the cleaning frequency is high, there are problems that the rate of operation of the semiconductor manufacturing apparatus is lowered, and productivity is deteriorated.
SUMMARY OF THE INVENTION
The present inventor has found that it is possible to reduce adhesion of the fine particles to a wafer by forcibly generating a cracking in a deposited film of reaction by-products during the manufacturing process of a semiconductor apparatus, and by forcibly discharging out, by means of a gas purge, the fine particles generated when the cracking was generated, and as a result, it is possible to reduce the frequency of cleaning operations of a reaction furnace, and to enhance the productivity.
The present inventor has found that it is possible to reduce adhesion of the fine particles to a wafer by lowering the temperature in a reaction furnace, in a state where there are no substrates to be processed in the reaction furnace, to increase the stress of a reaction by-product deposited film adhered to the reaction furnace, and by forcibly generating a cracking in the deposited film, and by forcibly discharging out, by means of a gas purge, the fine particles generated when the cracking was generated.
The present invention is based upon the above-mentioned findings, and according to a first aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising:
forming a film on a substrate to be processed in a reaction furnace at a first temperature,
unloading the substrate from the reaction furnace, and
lowering a temperature in the reaction furnace to a second temperature which is lower than the first temperature, and conducting a gas purge, using only an inert gas, in the reaction furnace after the substrate has been unloaded from the reaction furnace.
According to a second aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising:
conducting batch processing in a reaction furnace in a state in which a plurality of substrates to be processed are mounted on a boat, to form films on the plurality of substrates to be processed at a first temperature,
thereafter unloading the boat from the reaction furnace,
taking out processed substrates,
after the boat has been unloaded from the reaction furnace, lowering a temperature in the reaction furnace to a second temperature which is lower than the first temperature, conducting a gas purge in the re
Anya Igwe W.
Kokusai Electric Co. Ltd.
Smith Matthew
LandOfFree
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