Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Ion implantation of dopant into semiconductor region
Reexamination Certificate
1999-08-16
2001-02-13
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Ion implantation of dopant into semiconductor region
C438S592000, C438S593000
Reexamination Certificate
active
06187655
ABSTRACT:
BACKGROUND OF INVENTION
1) Field of the Invention
This invention relates generally to fabrication of semiconductor devices and more particularly to performing a pre-amorphization implant (PAI) during a salicide process.
2) Description of the Prior Art
Self-aligned silicide (salicide) formation is widely used in semiconductor manufacting. It is well known that salicide formation is enhanced by doping the silicon region on which salicide formation will occur. This doping process is known as pre-amorphization implant (PAI). PAI is widely, used in 0.25 &mgr;m devices. However, if the salicide process parameters are not precisely controlled, voids can form in the resist protect oxide (RPO) resulting in juction leakage. As PAI energy increases and/or pre-metal dip time increases RPO voids increase.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering the following patents.
U.S. Pat. No. 4,635,347 (Lein et al.) shows a self-aligned TiSi
x
gate and contact forming process.
U.S. Pat. No. 5,605,854 (Yoo) shows a TiSi
x
process.
U.S. Pat. No. 5,656,546 (Chen et al.) shows a self-aligned TiN/TiSi
x
process.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of performing a pre-amorphization implant (PAI) which reduces damage to the resist protect oxide (RPO).
It is another object of the present invention to provide a method of performing a pre-amorphization implant (PAI) which reduces leakage current in the RPO.
It is another object of the present invention to provide a method of performing a pre-amorphization implant (PAI) which reduces salicide spiking on the RPO.
It is yet another object of the present invention to provide a method for forming a self-aligned silicide contact using the aforementioned novel PAI process.
To accomplish the above objectives, the present invention provides a method for performing a pre-amorphization implant which reduces damage to the resist protect oxide layer and reduces leakage current between the gate and substrate. Two novel approaches are provided, both of which use a photoresist mask to protect the RPO from implant damage during PAI. In the first approach, the PAI is performed immediately after RPO etching to form contact openings. Thus the original photoresist mask is still on the RPO. In the second approach, the photoresist mask is re-formed prior to PAI to protect the RPO from implant damage.
The present invention provides considerable improvement over the prior art. The photoresist mask (
16
) overlying the resist protect oxide (
14
) prevents impurity ions (
20
) from penetrating the resist protect oxide layer (
14
). When ions are implanted into the resist protect oxide (
14
), they cause damage to the resist protect oxide (
14
), resulting in voids. During the subsequent salicide step, silicide spikes are formed in the voids causing junction leakage. Thus, the present invention reduces junction leakage.
Also, since the present invention prevents implant damage to the RPO, the PAI of the present invention can accomodate a greater range of the implant energy. A greater range in pre-metal dip can also be tolerated in the present invention, since implant damage to the RPO is prevented.
The present invention achieves these benefits in the context of known process technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.
REFERENCES:
patent: 4635347 (1987-01-01), Lien et al.
patent: 5605854 (1997-02-01), Yoo
patent: 5656546 (1997-08-01), Chen et al.
patent: 5920774 (1999-07-01), Wu
patent: 6004843 (1999-12-01), Huang
patent: 6054357 (2000-04-01), Choi
Hsiue Horng-Jer
Hu Ding-Dar
Huang Ching-Kunn
Wang Jiann-Jong
Ackerman Stephen B.
Le Dung A
Nelms David
Saile George O.
Stoffel William J.
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