Browse Prior Art Database

METHOD FOR FORMATION OF SOLDER BUMPS DIRECTLY ONTO ALUMINUM BOND PADS

IP.com Disclosure Number: IPCOM000009762D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-17
Document File: 2 page(s) / 119K

Publishing Venue

Motorola

Related People

Iwona Turlik: AUTHOR [+3]

Abstract

Currently, solder based flip chip bumps on IC bond pads are deposited either by evaporation, plating, thermo-compression bonding (stud bump bonding) or stencil printing (Figure 1). In order to form a robust bond to the aluminum IC bond pad, additional solder wettable layers are added to the IC bond pad e.g. TiW, Au.

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MOTOROLA

Technical Developments

METHOD FOR FORMATION OF SOLDER BUMPS DIRECTLY ONTO ALUMINUM BOND PADS

by Iwona Turlik, Cindy Melton and Dan Gamota

Currently, solder based flip chip bumps on IC bond pads are deposited either by evaporation, plating, thermo-compression bonding (stud bump bonding) or stencil printing (Figure 1). In order to form a

robust bond to the aluminum IC bond pad, additional solder wettable layers are added to the IC bond pad e.g. TiW, Au.

, 0"'

Fig. 1 Left: Solder bumped wafer.

Right: Individual bump.

These layers are called the under bump metallurgy (UBM). The additional process steps to add the UBM are costly and make technologies that can eliminate their need very attractive for high volume wafer manufacturing.

The UBM deposition techniques which are used today for qualified flip chip bump metallurgies (high Pb/Sn alloys) are sputtering and evaporation (Figure 2).

Fig. 2 Solder joint created on UBM.

Motorola. Inc. 2000

]9

May 2000

MOTOROLA

Technical Developments

The processing equipment required for these UBM deposition techniques adds significant cost to the bumping process (equipment, time and materials). Until a lower cost process can be identified and qualified to create the UBM, the lowest cost potential for flip chip bumping technology will not be realized.

The invention being disclosed is a method to deposit micro-volumes of metallurgical solder directly onto an aluminum IC bond pad without the need for a solder wettable UBM. The solder is dis...