Browse Prior Art Database

Multilayer IC Substrate System

IP.com Disclosure Number: IPCOM000052314D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Darrow, RE: AUTHOR [+3]

Abstract

In this system, Au is used instead of Cr for the top metal layer of an internal plane of a multiplanar, i.e., multilayer, integrated circuit (IC) substrate.

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Multilayer IC Substrate System

In this system, Au is used instead of Cr for the top metal layer of an internal plane of a multiplanar, i.e., multilayer, integrated circuit (IC) substrate.

An IC substrate having two metalization planes M1 and M2, each with a three-metal-layer structure of Cr-Cu-Cr, is described in the article "Process for Making Multilayer IC Substrate," IBM Technical Disclosure Bulletin, Vol. 22, No. 4, September 1979, pages 1420-1421, and the addendum thereto, Vol. 23, No. 12, May 1981, page 5642. In that particular substrate, the system uses a process whereby the gold replaces the M1 top Cr at the via hole sites. In the present system, a process is used whereby gold replaces the M1 top Cr entirely.

To do this, after the M1 bottom Cr and M1 Cu are blanket evaporated on the ceramic substrate, the M1 personality is photoetched therein. The gold is then immersion-plated over the M1 Cr-Cu personality, thus forming the M1 layer. The Au plates, i.e., covers, not only the top surface of the M1 Cu but also the sides of the Ml Cu and underlying M1 bottom Cr, thus providing a protective, anti- corrosive coating to the M1 Cu and Cr. Moreover, when the polyimide layer is subsequently applied, and the via hole formation is accomplished, the gold is already at the via sites, and the assembly is ready to receive the subsequent blanket evaporation of the M2 Cr-Cu-Cr layers.

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