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Polymer Passivation of Integrated Circuits

IP.com Disclosure Number: IPCOM000078689D
Original Publication Date: 1973-Feb-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Clark, RJ: AUTHOR [+3]

Abstract

Integrated circuit chips designed for flip-chip bonding require etching through passivation layers to allow mounting on substrates. When alkali soluble organic polymers are used as passivating materials, strong alkali etchants can corrode aluminum chip metallurgy.

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Polymer Passivation of Integrated Circuits

Integrated circuit chips designed for flip-chip bonding require etching through passivation layers to allow mounting on substrates. When alkali soluble organic polymers are used as passivating materials, strong alkali etchants can corrode aluminum chip metallurgy.

This technique provides a method for protecting metallurgy in such applications. Prior to the application of an alkali soluble passivating material, such as a polyimide, chips containing exposed metallurgy are placed in an electroless bath comprising nickel chloride, sodium citrate, ammonium chloride, and sodium hypophosphite, to provide a protective nickel coating over all exposed aluminum. The passivating polymer is then applied in any desired manner and etched with an aqueous solution of tetramethyl ammonium hydroxide having a Ph of about 13. If desired, the nickel may be removed with nitric acid after etching is complete.

Electroless plating is preferable over electrolytic techniques, because it does not require application of an electrical potential which could damage sensitive electronic components on the integrated circuit chip and because of its inherent economy.

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