Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2001-06-22
2004-04-06
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C422S168000, C422S169000, C422S175000, C422S202000, C422S198000, C096S372000, C423S210000
Reexamination Certificate
active
06716750
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains in general to a system and method for processing residual gas and, more particularly, to a system and method for processing and disposing of residual toxic gas in a semiconductor manufacturing process.
2. Description of the Related Art
A variety of process gases are used in various process equipment in a semiconductor manufacturing process. For example, a Chemical Vapor Deposition (CVD) process often uses SiH
4
, B
2
H
6
, NH
3
and H
2
as process gases. Because many process gases are toxic and explosive, and because process gases are seldom completely reacted during a manufacturing process, handling of residual gases, i.e., process gases that remain after completion of the manufacturing process, is an important issue in semiconductor manufacturing. In addition, environmental concerns and government legislating prohibit toxic gases and harmful particles from being vented to the atmosphere or disposed of with waste water.
FIG. 1
is a flow chart of a conventional process for handling residual gas in a semiconductor manufacturing process that uses silane (SiH
4
) as the processing gas. Referring to
FIG. 1
, process gas, for example, silane, is selected at step
1
. Some of the characteristics of silane gas are described in the following table:
Atomic
Boiling
Molecule
Name
Weight
Color
Smell
point (° C.)
SiH
4
Silane
32
None
Repulsive
−112
Melting
Status in
Point
Density
Room
Safety
Toxic
(° C.)
(g/L)
Temperature
Characteristics
Indication**
−185
0.68
Gas
E/F/P*
TLV
IDLH
5 ppm
—
*E: explosive; F: inflammable; P: toxic
**TLV: Threshold Limit Value (time weighted average exposure for an 8-hour day in a 40-hour workweek)
IDLH: Immediate Danger to Life and Health
Source: R. J. Lewis, Sr., Hazardous Chemicals Desk Reference, 3
rd
Ed., Van Nostrand Reinhold, 1993.
These characteristics show that silane is toxic and explosive, and therefore great care should be taken in handling and disposing of silane gas. The process gas is then introduced at step
10
to a process chamber through a connecting pipe. After a semiconductor manufacturing process is performed in the process chamber at step
10
, a pump propels the remaining silane gas that did not fully react during the process, i.e., the residual gas, from the process chamber to a wet scrubber through another connecting pipe at step
20
. As described above, the residual gas introduced to the wet scrubber still contains non-reacted silane gas. Upon entering the wet scrubber, oxidation ensues and powdered silicon dioxide (SiO
2
) is formed. Water is then added to the wet scrubber so that both soluble and non-soluble SiO
2
powders are further processed at a waste water facility drain at step
42
. The resultant waste water is expelled to the environment. Any remaining residual gas and powders are vented at step
40
to a waste gas facility exhaust to be further processed and then be expelled into the atmosphere.
This conventional technique, however, cannot ensure that all of the silane gas that passes through the wet scrubber is reacted. Therefore, an explosion is still possible if the silane gas were to come into contact with oxygen in one of the connecting pipes. Furthermore, the non-reacted silane gas expelled to the atmosphere may still exhibit a toxic level higher than the legally prescribed safety level. In addition, the powders produced through oxidation of the silane gas may result in the blockage of inlets and outlets to and from the wet scrubber.
As a proposed improvement to ensure complete reaction of the residual gas, an alternative conventional technique employs catalysts to breakdown the residual gas, or absorbents to absorb toxic materials or particles so that the gas expelled into the atmosphere is harmless. Such a method, however, requires complex chemical reaction processes. In addition, catalysts and absorbents are usually expensive and cannot be repeatedly used, resulting in an additional cost to the manufacturing process. Moreover, the catalysts and absorbents themselves become toxic from the process and become industrial wastes, of which cannot be easily disposed.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a system and method for processing residual gas that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structures and methods particularly pointed out in the written description and claims hereof, as well as the appended drawings.
To achieve these and other advantages, and in accordance with the purpose of the invention as embodied and broadly described, there is provided a chamber for processing residual gas that includes a residual gas inlet mechanism for receiving residual gas, at least one first gas inlet mechanism for receiving inert gas, at least one second gas inlet mechanism for receiving a reactive gas, at least one baffle for increasing a path of gas flow, and a gas outlet mechanism for outputting mixed gases from mixing the residual gas, inert gas and reactive gas and non-reacted residual gas, inert gas and reactive gas.
In one aspect of the invention, the chamber further includes a plurality of baffles for increasing a time the residual gas is in contact with the reactive gas.
In another aspect of the invention, the chamber further includes a pressure meter connected to the chamber for monitoring a pressure inside the chamber.
Also in accordance with the present invention, there is provided a system for processing residual gas that includes a chamber having at least one baffle for increasing gas flow path, a residual gas inlet mechanism connected to the chamber for supplying residual gas to the chamber, at least one first gas inlet mechanism connected to the chamber for supplying inert gas to the chamber, at least one second gas inlet mechanism connected to the chamber for supplying a reactive gas to the chamber, and a gas outlet mechanism for connected to the chamber for outputting mixed gases from mixing the residual gas, inert gas and reactive gas and non-reacted residual gas, inert gas and reactive gas.
Further in accordance with the present invention, there is provided a method for processing residual gas that includes providing a chamber, introducing residual gas into the chamber, the residual gas having a first toxic level, diluting the residual gas, introducing a reactive gas into the chamber to cause a reaction between the diluted residual gas and reactive gas to produce a mixed gas, and outputting the mixed gas from the chamber, the mixed gas having a toxic level lower than the first toxic level.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5335609 (1994-08-01), Nelson et al.
patent: 5521263 (1996-05-01), Seeger et al.
patent: 5955037 (1999-09-01), Holst et al.
patent: 6322756 (2001-11-01), Arno et al.
patent: 6423284 (2002-07-01), Arno et al.
Chen Chang-Cheng
Chen Chun-Chi
Wu Cheng-ta
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
ProMos Technologies Inc.
Rocchegiani Renzo N
Smith Matthew
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