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:
Mar. 18, 2003
Filed:
Mar. 22, 2001
Mitsubishi Materials Silicon Corporation, Tokyo, JP;
Abstract
A first chopper between a laser device and a semiconductor substrate chops an excitation light at a specific frequency, and a second chopper between the first chopper and the semiconductor substrate chops the excitation light at a variable frequency higher than the first chopper. A photoluminescence light emitted by the semiconductor substrate when the semiconductor substrate is intermittently irradiated with the excitation light is introduced into a monochromator. A controller obtains the decay time constant T of the photoluminescence light from variation of the average intensity of the photoluminescence light when gradually increasing the chopping frequency of the excitation light by controlling the second chopper, and computes the life time &tgr; of the semiconductor substrate from an expression “&tgr;=T/C”, where C is a constant. An object of the invention is to accurately evaluate impurities, defects and the like in a semiconductor substrate by obtaining quantitatively the life time of the semiconductor substrate having a long life time.