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Aluminum Copper Silicon Subetch Process

IP.com Disclosure Number: IPCOM000086302D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Alcorn, G: AUTHOR [+3]

Abstract

Large-scale integrated circuits having aluminum-copper metallurgy, employ a thin layer of silicon thereover to avoid metallurgical penetration through shallow junctions of the substrate. Conventional etching techniques for the aluminum-copper-silicon composite employ a sequence of steps, including etching the silicon layer with nitric acid and hydrofluoric acid followed by etching the aluminum-copper layer with an appropriate etchant.

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Aluminum Copper Silicon Subetch Process

Large-scale integrated circuits having aluminum-copper metallurgy, employ a thin layer of silicon thereover to avoid metallurgical penetration through shallow junctions of the substrate.

Conventional etching techniques for the aluminum-copper-silicon composite employ a sequence of steps, including etching the silicon layer with nitric acid and hydrofluoric acid followed by etching the aluminum-copper layer with an appropriate etchant.

Often, incomplete etching of the silicon occurs leaving silicon fragments or silicon bridging which will be undercut by the subsequent aluminum-copper etchant, thereby leaving a ledge along the conductor surface. Existing techniques attempt to remove this ledge through a sequence of ultrasonic steps.

A technique for sharply delineating the edge of an aluminum-copper-silicon composite is as follows. The silicon layer when deposited on the aluminum- copper layer, has a coarse texture which allows the aluminum-copper layer to be etched under the silicon which remains in place, by using a phosphorous/nitric acid etchant at 40 degrees centigrade for a three minute exposure.

This is followed by a reactive plasma etching step, wherein the etched composite is exposed in a reactive plasma etching chamber for 15 seconds in an ambient of CF(4)+7% O(2) at a flow rate of 50CC/minute and a radio-frequency power of 300 watts. The silicon fragments and the silicon ledge are readily removed from the surface of...