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:
Aug. 18, 1998
Filed:
Mar. 31, 1997
David E Jacob, Fremont, CA (US);
LAM Research Corporation, Fremont, CA (US);
Abstract
The presence and absence of a semiconductor wafer on a wafer holder in a vacuum chamber having an optically transparent window is detected by an optical system including a source of optical energy positioned outside the chamber and a receiver for the optical energy positioned outside the chamber. A light path extends from the source through the window and an opening in the wafer holder when no wafer is on the wafer holder. The optical path is bent downstream of the wafer holder, thence continues back through another opening in the wafer holder, and through the window to the receiver. The optical receiver is positioned and arranged so optical energy reflected from a wafer (even a wafer having dispersive mirror properties) in situ on the wafer holder cannot be reflected or otherwise incident on the optical receiver. The optical receiver thus has optical energy from the source incident on it when no wafer is present on the wafer holder and no optical energy from the source is incident on the receiver when a wafer is on the wafer holder.