Browse Prior Art Database

Mask for Producing a Pattern of Fiducial Points on Semiconductor Wafers

IP.com Disclosure Number: IPCOM000080460D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Wuestenhagen, JF: AUTHOR

Abstract

An etch mask pattern consisting of a plurality of identical individual segments that are to be juxtaposed very accurately (tolerance about 0.2 mu) is transferred to a photoresist-coated wafer, by being projected segment-by-segment until the full wafer has been exposed. With this method it is important that prior to each exposure, the segment is accurately aligned to the segments previously projected onto the wafer. During the manufacture of integrated circuits, several etch masks are superimposed on the wafer. From the second etch mask onward, alignment is very simple since particular points in the pattern of the preceding masks can be used as fiducial points. However, etching the fiducial points required for aligning the first etch mask into the wafer surface is a problem.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Mask for Producing a Pattern of Fiducial Points on Semiconductor Wafers

An etch mask pattern consisting of a plurality of identical individual segments that are to be juxtaposed very accurately (tolerance about 0.2 mu) is transferred to a photoresist-coated wafer, by being projected segment-by-segment until the full wafer has been exposed. With this method it is important that prior to each exposure, the segment is accurately aligned to the segments previously projected onto the wafer. During the manufacture of integrated circuits, several etch masks are superimposed on the wafer. From the second etch mask onward, alignment is very simple since particular points in the pattern of the preceding masks can be used as fiducial points. However, etching the fiducial points required for aligning the first etch mask into the wafer surface is a problem. This problem is particularly crucial, since the first mask determines how accurately the individual segments of the various masks are juxtaposed.

The problem is solved by a chromium mask which is used to contact print a pattern of fiducial points onto the wafer. The chromium mask is produced in the following steps: segment S shown in Fig. 1 is projected roughly onto the center of a thin photoresist-coated chromium layer on a glass substrate having the size of a wafer, using the same projection equipment as for the etch masks. The photoresist is developed, the chromium is etched, and finally the photoresist is stripped off (field S1 in Fig. 2). The chromium layer is again photor...