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:
Nov. 25, 2008
Filed:
Nov. 29, 2007
Kazushige Kawasaki, Tokyo, JP;
Takafumi Oka, Tokyo, JP;
Katsuomi Shiozawa, Tokyo, JP;
Mitsubishi Electric Corporation, Tokyo, JP;
Abstract
An SiOfilm is formed on a semiconductor layer stack, the SiOfilm having a thickness da and an etch rate Ra in buffered (BHF). A waveguide ridge with the SiOfilm thereon is formed using a resist pattern. An SiN film is formed on top and both sides of the waveguide ridge, while leaving the resist pattern in place, the SiN film having a thickness db and an etch rate Rb in BHF, where 1<(db/Rb)/(da/Ra). Then the resist pattern and the overlying portion of the SiN film are removed by lift-off to form an opening in the SiN film. Wet etching for a predetermined period of time with BHF removes the SiOfilm from the waveguide ridge, while leaving the SiN film in place.