Browse Prior Art Database

Dual Television Photomask Alignment and Exposure System

IP.com Disclosure Number: IPCOM000076635D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Miller, JC: AUTHOR

Abstract

In aligning masks to semiconductor wafers on which photoresist has been applied, a microscope is used to view the mask and the wafers to permit alignment of one to the other prior to exposure of the mask pattern onto the wafer. However, such alignment, as line width and device size decreases, creates a strain on the operator and makes it extremely difficult for correct alignment after several hours of operation. Secondly, misalignment of the illuminating light or condenser lens creates a "shadow" image which is difficult to detect. Thirdly, image contrast in the microscope creates a very realignment problem, especially with subcollector patterns and chrome metallization masks over aluminum evaporations.

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Dual Television Photomask Alignment and Exposure System

In aligning masks to semiconductor wafers on which photoresist has been applied, a microscope is used to view the mask and the wafers to permit alignment of one to the other prior to exposure of the mask pattern onto the wafer. However, such alignment, as line width and device size decreases, creates a strain on the operator and makes it extremely difficult for correct alignment after several hours of operation. Secondly, misalignment of the illuminating light or condenser lens creates a "shadow" image which is difficult to detect. Thirdly, image contrast in the microscope creates a very realignment problem, especially with subcollector patterns and chrome metallization masks over aluminum evaporations.

To avoid the above problems, the microscope is replaced with a dual television system. The system as shown includes a pair of television cameras 10 and 11 which view through beam splitter mirrors 12, 13 associated with separate optical systems 14 and 15, the light projected through the systems onto a mask 16 and wafer 17. The light may be provided by a mercury-vapor high pressure burner 18. This light passes through an ultraviolet collimator 19 and a rotary shutter and filter 20 onto a mirror 21 which reflects the light through the optical lens systems onto the mask and wafer. The cameras 10 and 11 are connected to separate television viewing screens so that spaced apart indicia on the mask may be aligned wit...