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Selective Plating of Ohmic Contacts

IP.com Disclosure Number: IPCOM000091826D
Original Publication Date: 1968-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Regh, J: AUTHOR

Abstract

This plating method is for the formation of temporary ohmic contacts to silicon devices. The ohmic contacts can be utilized for testing during intermediate stages in the fabrication of devices. The interfacial silicon oxide layer, which is always present when silicon is exposed to air, must be broken to allow good contact for testing purposes. Difficulties which are normally encountered in making ohmic contacts to high-resistivity wafers due to this silicon oxide layer can be overcome. This is effected by exposing the wafers to be tested to a solution containing a cupric salt and ammonium fluoride or hydrofluoric acid. The ammonium fluoride dissolves the silicon oxide. The resultant exposed silicon surface immediately plates with copper which prevents the reformation of a new silicon-oxide layer.

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Selective Plating of Ohmic Contacts

This plating method is for the formation of temporary ohmic contacts to silicon devices. The ohmic contacts can be utilized for testing during intermediate stages in the fabrication of devices. The interfacial silicon oxide layer, which is always present when silicon is exposed to air, must be broken to allow good contact for testing purposes. Difficulties which are normally encountered in making ohmic contacts to high-resistivity wafers due to this silicon oxide layer can be overcome. This is effected by exposing the wafers to be tested to a solution containing a cupric salt and ammonium fluoride or hydrofluoric acid. The ammonium fluoride dissolves the silicon oxide. The resultant exposed silicon surface immediately plates with copper which prevents the reformation of a new silicon-oxide layer. The silicon-copper interface provides an ohmic contact.

A typical solution contains: 40 gm Cupric Sulfate or nitrate

250 gm Ammonium Fluoride

1000 cc Water.

After testing, the wafers are cleaned with nitric acid to remove all copper in the contact areas.

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