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Analog Automatic Wafer Alignment for Fine Positioning

IP.com Disclosure Number: IPCOM000082963D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Khoury, HA: AUTHOR

Abstract

Fig. 1 shows an automatic wafer alignment of a photoetched X-line 4 and Y-line 2 on a wafer 6, which scans a linear photodiode array across the wafer to pick up the diffraction pattern. A step and repeat process is used by moving the X-Y table 12 (fig. 2) until the diffraction pattern is detected in the diode array.

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Analog Automatic Wafer Alignment for Fine Positioning

Fig. 1 shows an automatic wafer alignment of a photoetched X-line 4 and Y- line 2 on a wafer 6, which scans a linear photodiode array across the wafer to pick up the diffraction pattern. A step and repeat process is used by moving the X-Y table 12 (fig. 2) until the diffraction pattern is detected in the diode array.

This method leaves a "dead zone" see Fig. 3, when only the diffraction pattern is monitored.

A more precise positioning of the area of the dead zone may be accomplished by selecting one of the diodes in the array 8 and 10 of Fig. 2 and monitoring its voltage amplitude output. The selected diode is peaked when the wafer is scanned by the step and repeat movement of the X-Y table 12 beneath the optical column 14 and the photoetched line(s) of the wafer is detected. Alignment within the center of the photoetched line (Kerf) of the wafer is possible (See Fig. 4).

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