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:
Jul. 28, 2009
Filed:
May. 23, 2007
Mingwei Xu, South Portland, ME (US);
Jamal Ramdani, Scarborough, ME (US);
Mingwei Xu, South Portland, ME (US);
Jamal Ramdani, Scarborough, ME (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A system and method are disclosed for providing a fully self aligned bipolar transistor using modified cavity formation to optimize selective epitaxial growth. A collector of a transistor is formed and at least two layers of silicon oxide are formed above the collector and covered with a polysilicon external raised base. Then an emitter window is etched through the polysilicon external raised base down to the top layer of silicon oxide. A wet etch process is performed to form a cavity in the at least two layers of silicon oxide. Different wet etch rates of the silicon layers with respect to the wet etch process cause the cavity to be formed with a shape that optimizes selective epitaxial growth in the cavity. Polysilicon rich corners and a monocrystalline silicon base are then formed within the cavity.