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Titanium Ball Limiting Metallurgy

IP.com Disclosure Number: IPCOM000046043D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Bhattacharya, SS: AUTHOR [+4]

Abstract

Pn-Sn solder bumps interconnect, by flip-chip bonding, the ball limiting metallurgy (BLM) on the chip to the wettable metallurgy on the ceramic carrier. The BLM requirements consist of (i) good electrical contact to the Al-Cu interconnection metallurgy on the chip, (ii) good adhesion to the passivation layer on the chip, (iii) a wettable surface for Pb-Sn solder, and (iv) relatively low stress metal. Conventionally, this has been accomplished by a layered metal structure tailored to meet BLM requirements.

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Titanium Ball Limiting Metallurgy

Pn-Sn solder bumps interconnect, by flip-chip bonding, the ball limiting metallurgy (BLM) on the chip to the wettable metallurgy on the ceramic carrier. The BLM requirements consist of (i) good electrical contact to the Al-Cu interconnection metallurgy on the chip, (ii) good adhesion to the passivation layer on the chip, (iii) a wettable surface for Pb-Sn solder, and (iv) relatively low stress metal. Conventionally, this has been accomplished by a layered metal structure tailored to meet BLM requirements.

Titanium provides an excellent electrical contact to the Al-Cu metallurgy on the chip and also has good adhesion to the passivation layer; it also provides a wettable surface to Pb-Sn solder when protected from atmospheric oxidation by a thin layer of gold. Another advantage of a titanium BLM is its inherently low intrinsic stress and therefore easy compatibility with a lift-off process.

The titanium BLM offers simpler processing and higher throughput than the conventionally layered BLM. Deposition of titanium can be accomplished by evaporation or sputtering. Prior to titanium deposition the openings in the passivation layer can be cleaned chemically or by sputter etching. Titanium thickness in the range of 2,000 ~ -15,000 ^ has been found suitable. Other titanium deposition process parameters are not critical.

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