Device for detecting the position of a surface

Details Device for detecting the position of a surface Device for detecting the position of a surface

1991-02-21

1992-11-10

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

250561, 356376, G01J 120

Patent

active

051626420

ABSTRACT:
A surface position detecting device usable with a semiconductor device manufacturing exposure apparatus having a projection lens system for projecting an image of a pattern of a mask onto a semiconductor wafer. The device is arranged to detect the position of the wafer relative to an image plane of the projection lens system, into which plane the wafer is to be positioned. The device includes a sensor for sensing light reflected by the wafer thereby to detect the position of the wafer. Also, in order to avoid detection errors due to interference of light caused by a resist layer formed on the wafer, the wafer is irradiated with different wavelengths of lights from plural light sources. In one aspect, the device uses a reference light which is directed to the sensor without reflection by the wafer in order to avoid an effect of drift of the sensor.

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