Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1999-03-26
2001-07-03
Bueker, Richard (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S729000, C118S730000
Reexamination Certificate
active
06254687
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a chemical vapor deposition system, and in particular to a chemical vapor deposition system which can prevent undesired deposition of material on surfaces in the reaction chamber.
BACKGROUND OF THE INVENTION
Chemical vapor deposition (CVD) is commonly used for forming thin layers of material known as films over an integrated circuit substrate and other surfaces. The substrate commonly known as a wafer is heated in a reaction chamber, and is exposed to material gases introduced into the chamber. As a result of thermal decomposition and/or reaction of the material gases, a film such as a gallium arsenide compound is formed on the surface of the wafer.
In a system for such a CVD process, as a result of contact with the material gas, unnecessary byproducts such as arsenide tend to be deposited on various surfaces such as the wall surfaces provided opposite to the susceptors for the wafer to be processed for controlling the flow of the material gas. Such byproducts are known to reduce the use efficiency of the material gas, and may become particulate contaminants that could be included in the deposited layers. Inclusion of such contaminants in the wafer can seriously impair the quality of the integrated circuits, semiconductor devices and other final products.
BRIEF SUMMARY OF THE INVENTION
In view of such problems of the prior art, a primary object of the present invention is to provide a chemical vapor deposition system which can reduce undesired material deposition on the wall surfaces of the reaction chamber so as to minimize the cost and effort required for the maintenance of the chemical vapor deposition system.
A second object of the present invention is to provide a chemical vapor deposition system which is resistant to contamination, and can thereby improve the quality of the CVD products.
A third object of the present invention is to provide a chemical vapor deposition system which can form a uniform film on the surface of the substrate to be treated.
A fourth object of the present invention is to provide a chemical vapor deposition system which can minimize the waste of the material gas.
According to the present invention, these and other objects can be accomplished by providing a chemical vapor deposition system, comprising: a pair of susceptors placed opposite to each other defining a gap therebetween and having opposing surfaces adapted to retain wafers thereon; a conduit for passing material gas through the gap; and a pair of heater units each provided adjacent the other side of the corresponding one of the susceptors.
Thus, the mutually opposing surfaces of the susceptors provide flow control surfaces so that a favorable material gas flow can be achieved. As these surfaces are mostly covered by the wafers to be processed, any wasteful deposition of material on the chamber surfaces can be avoided. Thus, the need to clean the surface of the chamber wall is minimized. Such material deposition is not only wasteful but also could become a source of contamination as such deposition tends to peel off. Also, a relatively large number of wafers can be processed in a limited space within the reaction chamber.
In view of minimizing contamination, the susceptors may be preferably disposed vertically and/or parallel to each other so that any particulate contaminants may drop into the bottom of the reaction chamber without falling onto the surfaces of the wafers, and the material gas may flow without any significant disturbances. For uniform processing of the wafers, the susceptors may be supported by turntables. These turntables may rotate in mutually opposing directions for an optimum result.
According to a preferred embodiment of the present invention, the wafer retaining surfaces of the susceptors are adapted to retain a plurality of wafers in a concentric arrangement so that a maximum number of wafers may be processed in a given space of the reaction chamber. From a similar consideration as well as for achieving a controlled flow of the material gas, the conduit for passing material gas through the gap may be received in a rotary shaft of one of the turntables, and provided with an opening communicating with the gap.
REFERENCES:
patent: 4858558 (1989-08-01), Ohmura et al.
patent: 5427620 (1995-06-01), deBoer et al.
patent: 5679405 (1997-10-01), Thomas et al.
Bueker Richard
Japan Process Engineering Ltd.
Marshall & Melhorn LLC
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