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:
May. 03, 1988
Filed:
Apr. 14, 1987
Stephen R Burnham, Tucson, AZ (US);
William J Lillis, Tucson, AZ (US);
Burr-Brown Corporation, Tucson, AZ (US);
Abstract
A subsurface zener diode is formed in an N.sup.- epitaxial region formed on a P type substrate. The N.sup.- epitaxial region is isolated by a P.sup.+ isolation region. An N.sup.+ buried layer region is disposed between a portion of the N.sup.- epitaxial region and the P type substrate. A first P.sup.+ region is formed in the middle of the N.sup.- epitaxial region at the same time as the P.sup.+ isolation regions. Second and third adjacent P.sup.+ regions also are formed in the N.sup.- epitaxial region adjacent to and slightly overlapping the first P.sup.+ region, all three P.sup.+ regions terminating at the N.sup.+ buried layer. An N.sup.+ region, formed during an emitter diffusion operation, has first and second opposed edges centered within the overlapping portions of the first, second, and third P.sup.+ regions. Two other opposed edges of the N.sup.+ region extend beyond the other edges of the first P.sup.+ region, forming N.sup.+ N.sup.- contacts to the N.sup.+ epitaxial region, enabling it to be reverse biased without an additional N.sup.+ contact region and a corresponding metal conductor. Masking alignment tolerances in the direction of the N.sup.+ N.sup.- overlap are eased, increasing overall processing yields.