The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 21, 1990
Filed:
Apr. 14, 1989
Ravishankar Sundaresan, Garland, TX (US);
Mishel Matloubian, Dallas, TX (US);
Texas Instruments, Incorporated, Dallas, TX (US);
Abstract
An improved masking stack (63) comprises a pad oxide (58), polysilicon (60) and nitride (62). After forming a photoresist pattern (64) over the stack (63), an anisotropic etch is performed to remove the nitride (62) and a portion of the polysilicon (60) not covered by the pattern (64). Another etch is performed to remove the remaining polysilicon (60) to leave at least a portion of the pad oxide (58). A boron implant (66) is conducted to form implant areas (68 and 70) within the unmasked silicon active device layer (56). A portion of the implant areas (68 and 70) is masked with nitride (72), and the unmasked silicon layer (56) is then etched. The masking stack (63) and the nitride (72) is removed and unprotected silicon layer (56) and implant areas (68 and 70) are covered with an oxide forming the silicon dioxide mesa (78).