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Browse Prior Art Database

Metal Planarization Process Which Retains Alignment Targets

IP.com Disclosure Number: IPCOM000039587D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Chaloux, PN: AUTHOR [+3]

Abstract

By means of the scheme described in this article it is possible to planarize an opaque metal film covering semiconductor substrate topological features without the loss of targets essential for proper alignment of the next masks for photoresist patterns. Some semiconductor processing technologies require that wafer/substrate structures be made planar at various stages of build in order to minimize process tolerances and to improve uniformity. While it is possible to create alignment masks on the resultant surfaces with a blockout mask and etch, the procedure is costly and relies on gross manual alignment of the blockout mask.

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Metal Planarization Process Which Retains Alignment Targets

By means of the scheme described in this article it is possible to planarize an opaque metal film covering semiconductor substrate topological features without the loss of targets essential for proper alignment of the next masks for photoresist patterns. Some semiconductor processing technologies require that wafer/substrate structures be made planar at various stages of build in order to minimize process tolerances and to improve uniformity. While it is possible to create alignment masks on the resultant surfaces with a blockout mask and etch, the procedure is costly and relies on gross manual alignment of the blockout mask. This scheme provides appropriate targets for mask alignment through modification of an existing ion milling planarization procedure, which employs an intermediate etch in oxygen or oxygen/carbon tetraflouride (O2/CF4) plasma, to both improve throughput and the ability to align the next mask level. Fig. 1 illustrates a cross-sectional view of a substrate surface 1 following deposition of a blanket of metal 2 over its topological features. An alignment target 3 is identified among these features. A planarization coating of photoresist 4 is next applied to the surface, as indicated in Fig. 2. The typical pattern density existing is such that no via is large enough to significantly affect photoresist planarization, so the alignment target 3 can be easily located in a trough large enough...