Browse Prior Art Database

Scanning Mechanism for Workpiece Identification Reading

IP.com Disclosure Number: IPCOM000084805D
Original Publication Date: 1976-Jan-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Karsch, AF: AUTHOR [+4]

Abstract

The mechanism described is for scanning a sequence of numbers on a workpiece, such as a semiconductor wafer, the numbers being positioning serially, and reading (differentiating) each digit in its position.

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Scanning Mechanism for Workpiece Identification Reading

The mechanism described is for scanning a sequence of numbers on a workpiece, such as a semiconductor wafer, the numbers being positioning serially, and reading (differentiating) each digit in its position.

Referring to the drawing, a laser 10 (HeNe) is used as a collimated light source. A mask wheel 11 having a glass block 12 thereon is mounted for rotation. Twice in every mask wheel revolution, the laser beam passes through the block 11 and impinges on the surface of the wafer. Each digit on the wafer is written with Theta modulation (i.e., an 18 Degrees difference in line information for each digit 0-9 see for example, Fig. 5 of U. S. patent 3,305,834) the reflected defraction also passing back through the rotating glass block 12, which reflection is sensed by a photodiode array 13. The photodiode array is separated into 10 sets of segments which relate to the digits 0-9.

As the constantly rotating mask wheel 11 and block 12 passes the laser beam from digit to digit, the beam passes through a distance S on the wafer surface (see Fig. 2). The block 12 at the same time, rotates through an angular distance "A". In order that each digit on the workpiece or wafer may be read, a delta A position hole 14 is placed in the mask wheel 11. As the mask rotates, a light source 15 communicates with a diode detector 16 through the delta A position hole 14. Thus, the only time the diode detector 16 senses the light is wh...