Browse Prior Art Database

Preservation of E-beam Registration Marks

IP.com Disclosure Number: IPCOM000041219D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Tsai, CC: AUTHOR

Abstract

A Technique is shown for preserving the integrity of direct-write e-beam registration marks through all semiconductor processing levels to insure precise overlay registration. By preventing the destruction of direct-write e-beam registration marks, the need for extra registration marks which would occupy valuable chip area is negated.

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Preservation of E-beam Registration Marks

A Technique is shown for preserving the integrity of direct-write e-beam registration marks through all semiconductor processing levels to insure precise overlay registration. By preventing the destruction of direct-write e-beam registration marks, the need for extra registration marks which would occupy valuable chip area is negated.

In some etch processes (e.g., ones that rely on a "non-erodible mask", such as oxide or nitride), the photoresist is removed prior to completion of the etch. This poses a problem to direct-write e-beam registration marks that rely on the photoresist layer for protection during such etch steps. While this would not occur if a negative resist were used, in some applications a positive resist is the photoresist of choice. By using a complementary resist system, the e-beam alignment targets can be preserved throughout the semiconductor fabrication process steps.

A bilayer negative resist is applied to a wafer and a block-out pattern is exposed over the registration marks etched in the underlying silicon substrate. The negative resist is then developed away everywhere except over the registration marks, as shown in Fig. 1. Next a layer of positive resist is spun on top of the wafer and trench images are exposed, developed and etched as shown in Fig. 2. By scanning over the registration marks during the exposure of the trench images, good registration is maintained. The positive resist over and ar...