N- well CMOS process on a P substrate with double field guard rings and a PMOS buried channel
AssigneeSolid State Scientific Corporation
InventorsMark A. Halfacre, David S. Pan, Wing K. Huie
Life of this patent
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Abstract
CMOS transistors are fabricated in a P substrate using N- well regions. These wells are positioned to prevent aluminum spiking in the N channel devices. After P guard rings are formed for both P and N channel devices, additional masking and implantation are performed to produce N guard rings in the P channel devices. Before the transistors are formed, an implantation of P type impurities is performed causing the P channel devices, when they are formed, to have a PMOS buried channel.
Claims3
A method of fabricating complimentary P-channel and N-channel insulated gate field effect transistors in a P-conductivity type substrate which comprises the steps of:
- (a) forming a first masking layer over said substrate with a first opening to define the surface of said P-channel transistor, and a second and third opening at the surface areas at which a source and drain of said N-channel transistor is to be formed;
- (b) simultaneously introducing impurities into said substrate through said first, second and third openings to form a deep N-conductivity type well region in which said P-channel transistor is to be formed and to form deep N-conductivity type well regions in which respectively said source and drain of said N-channel transistor is to be formed;
- (c) removing said first masking layer;
- (d) growing a gate oxide layer over the substrate region at which said N-channel transistor is to be formed;
- (e) forming a conductive gate over a central portion of said N-channel transistor region;
- and
- (f) implanating N-type impurities through said gate oxide on either side of said gate into said source and drain areas to form said source and drain of said N-type transistor which are substantially more heavily doped and shallower than said corresponding underlying N-type wells.
Dependencies are inferred from the claim text.