Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-02-26
2001-10-16
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S299000, C438S592000, C438S655000, C438S649000, C438S664000
Reexamination Certificate
active
06303504
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to semiconductor manufacturing technology and more specifically to the nickel salicide process in semiconductor manufacturing.
BACKGROUND ART
The nickel salicide (self-aligned silicidation) process has been considered as a possible replacement for the traditional titanium salicide process on source/drain and polysilicon gate regions in semiconductors because of the lack of linewidth dependence of nickel silicide. While titanium disilicide increases in sheet resistance with decreasing linewidth, nickel monosilicide has a sheet resistance which gradually decreases with linewidth.
Also, the nickel salicide process has been considered as a possible replacement for the traditional titanium salicide process because of its processing simplicity. While the titanium salicide process involves two rapid thermal anneals at 700° C. and 850° C., the nickel salicide process only needs one rapid thermal anneal at a lower temperature between 400° C. to 600° C.
However, the nickel salicide process has not become a comprehensive replacement because it is subject to process variation not only because nickel is a less reactive metal in contact with silicon oxide, but also because the rapid thermal anneal temperatures for nickel are too low to initiate silicon oxide reduction. This means that the residual surface silicon oxide on the surface of the silicon substrate will interfere with the transition of nickel to nickel silicide during the annealing step. On the other hand, the titanium salicide process is known to be robust partially thanks to the ability of titanium to reduce surface silicon oxide and readily react with the silicon substrate.
As a result of the aforegoing, despite the advantages of nickel, titanium has been the metal of choice for a long time. A solution to these problems has been long sought but elusive to those skilled in the art.
DISCLOSURE OF THE INVENTION
The present invention provides the advantage of reducing the process variation of a nickel salicide process by the deposition of a very thin titanium layer on the silicon substrate followed by a layer of nickel of the desired thickness. The combination is then subject to a rapid thermal annealing step. The titanium acts as a reductant to break up the residual surface silicon oxide on the silicon surface and promotes the reaction of the nickel with the silicon in the silicon substrate to form nickel silicide.
The invention provides that the titanium and nickel are deposited sequentially in a vacuum cluster tool to prevent oxidation of the titanium by air.
The above and additional advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5027185 (1991-06-01), Liauh
patent: 5041394 (1991-08-01), Spratt et al.
patent: 5498569 (1996-03-01), Eastep
patent: 5567651 (1996-10-01), Berti et al.
patent: 5635426 (1997-06-01), Hayashi et al.
patent: 5635765 (1997-06-01), Larson
patent: 5646070 (1997-07-01), Chung
patent: 5656546 (1997-08-01), Chen et al.
patent: 5668040 (1997-09-01), Byun
patent: 5795808 (1998-08-01), Park
patent: 5924010 (1999-07-01), Chen et al.
patent: 402039528 (1990-02-01), None
Wolf, silicon processing for the VLSI ERA, vol. 1, pp. 399, 359-362, 1986.*
Wolf “Silicon Processing for the VLSI Era” vol. 1, pp. 397-399, 1986.
Bowers Charles
Ishimaru Mikio
Nguyen Thanh
VLSI Technology Inc.
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