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:
Apr. 04, 2000
Filed:
Jun. 25, 1999
Mitsuhiro Horikawa, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
On the back side of a base body, three layers of polysilicon layer are formed. These polysilicon layers contain boron. A boron concentration C.sub.B(1), C.sub.B(2) and C.sub.B(3) of the first, second and third polysilicon layers from the base body side have a relationship of C.sub.B(1) .ltoreq.C.sub.B(2) .ltoreq.C.sub.B(3). On the other hand, between the polysilicon layers, silicon oxide layers are formed respectively. Upon fabrication of a semiconductor device, at first, a gettering heat treatment is effected for the substrate under a given condition. Thus, contaminating impurity is captured at the grain boundary of polysilicon layers formed on the back side of the base body. Next, the polysilicon formed at the most back side is removed by etching. By this, contaminated impurity is removed from the semiconductor substrate.