Browse Prior Art Database

Etching Method for Cr/Cu/Al Metallization

IP.com Disclosure Number: IPCOM000045592D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Elias, KL: AUTHOR [+3]

Abstract

One conventional technique for packaging IC chips employs a ceramic substrate which has metallization applied thereto, and on which metallized substrate the chips are mounted by solder connections. It has been proposed that in some cases two levels of metallization may be usefully employed rather than only one. One such system employs a first level of metallization M1 on the ceramic substrate comprised of superimposed layers of Cr- Cu-Cr. Over this M1 layer a polyimide coating is applied, and then a second layer of metallization M2 is applied over the polyimide. The second layer M2 may contain superimposed layers of Al-Cu-Cr. It is often desirable to etch through this second layer of metallization. The following etch process has proved successful. 1.

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Etching Method for Cr/Cu/Al Metallization

One conventional technique for packaging IC chips employs a ceramic substrate which has metallization applied thereto, and on which metallized substrate the chips are mounted by solder connections. It has been proposed that in some cases two levels of metallization may be usefully employed rather than only one. One such system employs a first level of metallization M1 on the ceramic substrate comprised of superimposed layers of Cr- Cu-Cr. Over this M1 layer a polyimide coating is applied, and then a second layer of metallization M2 is applied over the polyimide. The second layer M2 may contain superimposed layers of Al-Cu-Cr. It is often desirable to etch through this second layer of metallization.

The following etch process has proved successful. 1. Apply and develop photo resist over the M2 layer to provide the desired openings. 2. Etch the top layer of Cr in the M2 layer with KMnO(4). 3. Etch the intermediate layer of Cu in the M2 layer with NH(4))(2) S(2)O(8). 4. Etch the bottom layer of Al in the M2 layer with H(3)PO(4)/HNO(3).

Various concentrations and temperatures of the reagents can be selected to control the etching rates.

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