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US 5,409,848 AGranted
Angled lateral pocket implants on p-type semiconductor devices
AssigneeVLSI Technology, Inc.
InventorsYu-Pin Han, Samuel J. S. Nagalingam
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Abstract
The punchthrough capacity of a p-type semiconductor device is significantly improved by nonuniformly doping the p-channel with n-type implants such as phosphorus. The n-type dopants are implanted at large angles to form pocket implants within the channel region. The dose of the implants, angle of the implants and the thermal cycle annealing of the implants will be optimized for maximum punchthrough capability without substantially detracting from the performance of the semiconductor device.
Claims20
A method for nonuniformly doping a channel region in a p-type MOSFET comprising the steps of:
- (A) providing an n-type semiconductor substrate;
- (B) forming a gate insulating film on said substrate;
- (C) forming a conductive layer upon said gate insulating film, which forms the gate electrode;
- (D) doping the entire source and drain regions of said substrate with a p-type dopant to a first impurity concentration, which is self-aligned to the gate electrode;
- (E) doping said substrate with an n-type dopant to form first and second pockets containing n-type dopant and having a second impurity concentration that is lower than said first impurity concentration, wherein said n-type dopant is implanted at an angle greater than 0.degree. from a line drawn perpendicular to the surface of said substrate and wherein said first pocket is beneath the gate insulating layer and adjacent to the source region and said second pocket is beneath the gate insulating layer and adjacent to the drain region;
- and
- (F) thermally treating said substrate to electrically activate said dopants.
4 more elements
Dependencies are inferred from the claim text.