Building Solder Bumps on GaAs Flip Chip Schottky
Devices
Prasit
Sricharoenchaikit
M/A-COM, Inc.,
Keywords: under bump metallurgy (UBM), plating,
photolithography, solder bumps, high temperature reverse bias (HTRB), and Joint
Electron Devices Engineering Council (JEDec)
Abstract
The semiconductor industry
has made astonishing improvements in decreasing circuit dimensions and more
importantly, greater performance. Making connections with gold contacts on GaAs
devices using solder bumps instead of silver Epoxy offers lower contact
resistance and hence, better performance. Further more, solder bump application
to GaAs devices is amenable to high volume production and ease of
manufacturing. Benefits from using solder bumps then become obvious for
connections. This paper describes a process development using our existing
technology of wafer processing in both wet and dry chemistries to build solder
bumps on GaAs wafer for flip chip Schottky devices. Eutectic Sn/Pb solder bumps
and Pb-free solder bumps were investigated. Detailed processing and chemistry
will be discussed. Reliability of solder bumps on GaAs flip chip Schottky
devices will also be presented.