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:
Jan. 09, 1990
Filed:
Dec. 02, 1988
Satoshi Kudo, Maebashi, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
Disclosed is a method of producing a bipolar transistor which enables an external base region, an intrinsic base region and an emitter region to be formed in self-alignment with respect to the base electrode. More specifically, the method comprises the steps of side-etching an insulating film formed underneath the base electrode by a wet etching process to provide an undercut portion, depositing polycrystalline silicon so as to extend into the undercut portion by low pressure CVD to thereby fill the undercut portion with the polycrystalline silicon, and subjecting the polycrystalline silicon to thermal oxidation, thereby simultaneously forming a sidewall spacer whereby the base electrode and the emitter electrode are electrically isolated from each other and an oxide film on the emitter forming region, the oxide film having high selectivity in anisotropic etching with respect to the substrate (silicon).