Browse Prior Art Database

Missing Pattern Detector

IP.com Disclosure Number: IPCOM000051382D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Admirand, DJ: AUTHOR [+2]

Abstract

This circuit provides an operator with the status (exposed/not exposed) of wafers processed in projection printers such as described in US Patents 4,068,947 and 4,198,159 taken in conjunction with the article in the IBM Technical Disclosure Bulletin 23, 1414-1415 (September 1980). This enables missing patterns and double exposures to be eliminated.

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Missing Pattern Detector

This circuit provides an operator with the status (exposed/not exposed) of wafers processed in projection printers such as described in US Patents 4,068,947 and 4,198,159 taken in conjunction with the article in the IBM Technical Disclosure Bulletin 23, 1414-1415 (September 1980). This enables missing patterns and double exposures to be eliminated.

As shown in the block diagram, this circuit provides four wafer status lights to the operator. Inboard wafer exposed

Inboard wafer unexposed

Outboard wafer exposed

Outboard wafer unexposed.

These signals come directly from inboard and outboard status latches (see the block diagram).

When the acting filter of the projection system opens, the inboard status latch is set (e.g., inboard wafer exposed). This data is transferred to the outboard latch when wafer transfer arms of the projection system are rotated. Simultaneously, the inboard status latch is reset, and vacuum on the outboard wafer is pulsed for 200 ms at a 1 second rate. This allows for wafer sensing and operator wafer removal. When no vacuum is sensed, the outboard status latch is reset.

If either or both the inboard and the outboard status latches or both the outboard status latch and the wafer reject line are set, then the "go" button is disabled and an exposed wafer cannot be put into the tool.

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