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. 20, 1990
Filed:
Jan. 17, 1990
Hugo Hauser, Palo Alto, CA (US);
Kevin M Monahan, Mountain View, CA (US);
Tritec Industries, Inc., Mountain View, CA (US);
Abstract
Circularly polarized light is used to detect an end point of a thin film layer. Collimated light is passed through a polarizing filter and a polarizing beam splitter resulting in light which is almost entirely linearly polarized in a first direction. This first direction polarized light is passed through a quarter wave retarder and is converted to circularly polarized light. The circularly polarized light is reflected off of a surface having a thin film layer and passes back through the quarter wave retarder. This reflected circularly polarized light is converted by the quarterwave retarder into linearly polarized light having a second direction. This second direction polarized light is easily isolated by passing it back through the beam splitter. The light may then be analyzed by end-point detection circuitry and the end-point of the film layer detected.