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Obtaining Cu Al Metallurgy Patterns

IP.com Disclosure Number: IPCOM000073553D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Harvilchuck, JM: AUTHOR [+2]

Abstract

A method for achieving Cu-Al blanket films or metal conductor patterns which does not involve vacuum evaporation of copper has been developed.

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Obtaining Cu Al Metallurgy Patterns

A method for achieving Cu-Al blanket films or metal conductor patterns which does not involve vacuum evaporation of copper has been developed.

Only pure aluminum is evaporated. After normal photoresist processing, appropriate etching and resist removal, a preparatory rinse cycle of ethanol- acetic acid and DI water "neutralizes" the surface conditions introduced by these previous chemical processes. A 30 minute bake at 200 degrees C in an oxygen atmosphere sufficiently oxidizes all scratched or otherwise exposed silicon to prevent its cladding with copper. The aluminum is also uniformly oxidized (200 angstroms).

An immersion in a solution consisting typically of 2gm. CuSO(4)-5H(2)O in 200 ml 1:1 volume H(3)PO(4): acetic acid removes most of the aluminum oxide while uniformly seeding the surface with a poorly adherent copper coating. The plating solution is strongly alkaline (12.5gms CuSO(4)-5H(2)O dissolved in 100 mls of 6.7% ethylenediamine) and displaces the loose acidic film with a uniform adherent copper coating.

After an alloying cycle (450 degrees C - 1 hr. in forming gas), a saturated ammonium persulfate solution strips the excess copper from the surface with no appreciable attack on the remaining film. Ideally 9 mass units of aluminum are dissolved and replaced by 31.8 mass units of copper.

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