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:
Dec. 17, 2002
Filed:
Oct. 28, 1999
Takao Morimoto, Tokyo, JP;
Yoshiharu Muroya, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
In exposing a diffraction grating pattern on a resist, the diffraction grating pattern is exposed via EB on an active region and the adjacent thereto only and the region which is not exposed via EB is exposed via Deep UV light so that the resist may be left on the active region and the adjacent thereto only after the exposed resist is developed according to the process of forming a diffraction grating for a distributed feedback semiconductor laser of the present invention. In addition, the resist-coated area can be gradually reduced from the resist existing area to the non-resist existing area and the average height of the substrate on which said diffraction grating is formed can be gradually changed on the diffraction grating forming region and non-diffraction grating forming region which results in preventing the crystallinity of a semiconductor layer on the substrate from being deteriorated. This enables formation of an excellent crystallinity semiconductor layer on the substrate on which the diffraction grating is locally formed.