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Nickel Ohmic Contacts

IP.com Disclosure Number: IPCOM000090289D
Original Publication Date: 1969-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Leff, J: AUTHOR [+2]

Abstract

The semiconductor substrate to which the ohmic contacts are to be made is a silicon substrate, the surface of which is coated with silicon dioxide. Apertures in the silicon dioxide layer expose the silicon substrate in the positions where ohmic contacts are to be made. Nickel is evaporated onto the silicon dioxide coated substrate at a temperature of from 500 degrees to 760 degrees C. Then the substrate is immersed in a 50% aqueous solution of concentrated nitric acid until the nickel deposited on the silicon dioxide is etched away, leaving deposits only in the contact holes. At the evaporation temperatures, the nickel alloys with the silicon to form a nickel silicide which is unaffected by the nitric acid and, consequently, remains intact.

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Nickel Ohmic Contacts

The semiconductor substrate to which the ohmic contacts are to be made is a silicon substrate, the surface of which is coated with silicon dioxide. Apertures in the silicon dioxide layer expose the silicon substrate in the positions where ohmic contacts are to be made. Nickel is evaporated onto the silicon dioxide coated substrate at a temperature of from 500 degrees to 760 degrees C. Then the substrate is immersed in a 50% aqueous solution of concentrated nitric acid until the nickel deposited on the silicon dioxide is etched away, leaving deposits only in the contact holes. At the evaporation temperatures, the nickel alloys with the silicon to form a nickel silicide which is unaffected by the nitric acid and, consequently, remains intact. Wire bonds or evaporated pad-type contacts can be made directly to the nickel-coated regions on large area devices. For small area or integrated circuit devices, a second metal, such as aluminum or molybdenum, can be deposited over the entire wafer surface and selectively removed to form land patterns over the silicon dioxide, connecting to the nickel silicide ohmic contacts.

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