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. 23, 1993
Filed:
Mar. 27, 1991
Applicant:
Inventors:
Assignee:
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G01R / ; G01R / ;
U.S. Cl.
CPC ...
3241 / ; 324 731 ; 3241 / ; 324642 ;
Abstract
Applying a first light (.lambda.=950 nm) to a Si wafer to generate electron-hole pairs, a microwave is emitted to the Si wafer and the amount of reflection of the microwave is measured. In like manner, applying a second light (.lambda.=633 nm), the amount of reflection of the microwave is measured. The two amounts are normalized by intensities of the lights respectively. In order to cancel an error resulting from geometrical position between a measuring apparatus and the Si wafer, a normalized finite difference is calculated through subtraction between the normalized amounts. The difference may be obtained by another calculation so that it stays in a specified width when a uniformly doped Si wafer is measured.