Apparatus method for determining the presence or absence of a wa

Details Apparatus method for determining the presence or absence of a wa Apparatus method for determining the presence or absence of a wa

1997-03-31

1998-08-18

Nelms, David C.

Optics: measuring and testing

By polarized light examination

With light attenuation

250548, 25055912, 250 221, 118675, 118676, 414936, G01B 1114, B05C 1100, B65G 4907, H01J 4014

Patent

active

057964866

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.

REFERENCES:
patent: 3902615 (1975-09-01), Levy et al.
patent: 3972424 (1976-08-01), Levy et al.
patent: 4713551 (1987-12-01), Layman et al.
patent: 5015177 (1991-05-01), Iwata
patent: 5240746 (1993-08-01), Litteral
patent: 5264918 (1993-11-01), Kagami
patent: 5271953 (1993-12-01), Litteral
patent: 5370745 (1994-12-01), Litteral
patent: 5518542 (1996-05-01), Matsukawa
patent: 5664254 (1997-09-01), Ohkura et al.
patent: 5686143 (1997-11-01), Matsukawa et al.

Affiliated with

Also associated with

Rating

Apparatus method for determining the presence or absence of a wa does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Apparatus method for determining the presence or absence of a wa, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus method for determining the presence or absence of a wa will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1119810