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:
Feb. 02, 1999
Filed:
Aug. 14, 1996
Mitsuo Kono, Hadano, JP;
Kei Matsumoto, Hiratsuka, JP;
Komatsu Electronic Metal Co., Ltd., Kanagawa, JP;
Abstract
In the wafer-bonding method of fabricating an SOI (silicon-on-insulator) substrate, even if there exists thickness variation in the silicon layer, devices fabricated onto the silicon layer, in accordance with the present invention, have a decreased threshold voltage variation. According to the present invention, after bonding two wafers, the thickness of the thinned silicon layer atop the SOI substrate is measured to precisely determine the local thickness distribution. However, the fabricated devices' threshold voltage depends upon the doping concentration as well as the thickness of the silicon layer. Shielding masks of photoresist are thereafter formed selectively on a portion of the silicon that are thicker. Then, through the masks as shielding, impurities are implanted into the silicon layer to adjust the doping concentration therein. Accordingly, the doping concentration is varied corresponding to the thickness, with the result that the threshold voltage variation nearly approaches zero.