Browse Prior Art Database

Oblique Wafer Detect Mechanism

IP.com Disclosure Number: IPCOM000112144D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 90K

Publishing Venue

IBM

Related People

Nahata, P: AUTHOR [+3]

Abstract

A wafer detection mechanism is provided which eliminates the problem caused by accidentally positioning wafers obliquely within their cassettes, thereby precluding the possibility of damaging or destroying a wafer in the cassette.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Oblique Wafer Detect Mechanism

      A wafer detection mechanism is provided which eliminates the
problem caused by accidentally positioning wafers obliquely within
their cassettes, thereby precluding the possibility of damaging or
destroying a wafer in the cassette.

      A mechanism is provided to automatically determine whether
semiconductor wafers, which have been manually handled, are properly
loaded in a carrying cassette.  Major problems can be created if the
wafers are cross-threaded or skewed in the cassettes when the wafers
are being retrieved by a robot arm.  If a wafer is cross-threaded in
a cassette, the wafer will not be in its expected position and the
pickup motion of the wafer handling robot arm will cause it to move
through the plane of the cross-threaded wafer, thereby causing damage
to the wafer.  Since the wafer may have nearly completed its
processing, a destroyed wafer can be very costly.

      On-line automatic wafer checking systems have been found to be
more reliable than manual checking.  However, known wafer checking
systems are very costly.

      The mechanism described herein is more desirable than known
automatic wafer checking systems because it is compatible with the
work envelope of robot handlers and the multiple cassette nesting
surrounding the robot.  Also, the mechanism, as illustrated in Figs.
1, 2 and 3, is simple, inexpensive and automatic.  Fig. 1 shows a
wafer carrying cassette 10 having indentations or recesses 12 on both
sides thereof by which wafers, such as semiconductor wafers a, b and
c, are supported.  Also shown in Fig. 1 is the end of a robot arm 14
used to retrieve the wafers a, b and c from the cassette 10.  A
source of radiation 16, preferably infrared radiation, is disposed on
one side of the wafers and a sensor 18 is positioned on the opposite
side of the wafers so as to intercept a beam 20 of the infra...