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Maskless Ball-Limiting Metallurgy

IP.com Disclosure Number: IPCOM000046392D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Crnic, F: AUTHOR [+4]

Abstract

Ball-limiting metallurgy (BLM) is formed without masked subetching of the BLM by use of a blanket deposit of BLM and a masked deposit of PbSn followed by reactive ion etching of the BLM using the PbSn as a mask. A simpler and cleaner (no photoresist residue in vias) process is achieved along with self-alignment of the BLM to the PbSn.

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Maskless Ball-Limiting Metallurgy

Ball-limiting metallurgy (BLM) is formed without masked subetching of the BLM by use of a blanket deposit of BLM and a masked deposit of PbSn followed by reactive ion etching of the BLM using the PbSn as a mask. A simpler and cleaner (no photoresist residue in vias) process is achieved along with self- alignment of the BLM to the PbSn.

Advantage is taken of the large difference in the relative thicknesses of the BLM and of the PbSn pad (approximately l:50). Thus, a loss in thickness of the PbSn during the reactive ion etching of the blanket BLM, using the PbSn as a mask, is not significant, as shown in the figure by the shaded area.

A feature of the techniques is the illustrated tapered edge which the PbSn imparts to the BLM.

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