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:
Oct. 22, 2002
Filed:
Jan. 24, 2001
Hiroji Kawai, Kanagawa, JP;
Sony Corporation, Tokyo, JP;
Abstract
After making a GaN FET by growing GaN semiconductor layers on the surface of a sapphire substrate, the bottom surface of the sapphire substrate is processed by lapping, using an abrasive liquid containing a diamond granular abrasive material and reducing the grain size of the abrasive material in some steps, to reduce the thickness of the sapphire substrate to 100 &mgr;m or less. Thereafter, the bottom surface of the sapphire substrate is processed by etching using an etchant of phosphoric acid or phosphoric acid/sulfuric acid mixed liquid to remove a strained layer by lapping followed by making a via hole by etching the bottom surface of the sapphire substrate by using a similar etchant.