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:
Dec. 27, 1994
Filed:
Mar. 31, 1994
Hiroshi Hirabayashi, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
On manufacturing a bipolar transistor, a field silicon oxide layer (7) having a beaked edge portion (bird's beak portion) is formed by a heat oxidation process using a silicon nitride film (5) as an oxidation mask. In this event, an edge of the nitride film is boosted up as a boosted portion by an upper part of the beaked edge portion. The upper part of the beaked edge portion is etched to form an undercut portion under the boosted portion. The undercut portion is filled with a base leading polysilicon (10) having impurities. On forming an insulator film (11) on the base leading polysilicon in a heated atmosphere, an outer base region (14) is formed in an epitaxial layer (3) by making the impurities diffuse from the base leading polysilicon towards the epitaxial layer in the heated atmosphere. Between the epitaxial layer and an edge portion of a nonboosted portion of the nitride film, a silicate glass (12) containing impurities is buried. The silicate glass (12) containing impurities is buried under the nitride film through an opening to form an inner base region (13) on the inside of the outer base region by diffusion of the impurities. The silicate glass is removed except an edge portion thereof which forms a link base region (15) by diffusion of the impurities. A hole of an insulator spacer (16) formed in the opening is filled with an emitter leading polysilicon (17) having impurities used in forming an emitter region (19) by diffusion.