NiGeAu Ohmic
Contact in InGaP pHEMTs
Ellen Lan, Qianghua
Xie, Peter Fejes, and Ha Le,
Motorola Inc.,
Semiconductor Products Sector
Phone: (480)
413-4128, Fax: (480) 413-4453, Email: ellen.lan@motorola.com
Keywords: InGaP/InGaAs pHEMT, ohmic contacts, NiGeAu,
annealing, contact resistance, TEM
Abstract
NiGeAu ohmic contact as a
function of alloying temperature on InGaP/InGaAs pHEMT structure was
investigated. It was found that the optimum RTA condition is 460 °C 60 sec for
n+ contact resistance, whereas 420 °C 30 sec for on-resistance. Electron microscope examinations of the
cross-sectional samples annealed at these two conditions revealed three types
of alloy grains. Chemical compositions of these grains were obtained by the
nano-probe X-ray energy dispersive spectrum (EDS) analysis. A correlation
between these alloy grains and the contact resistance and on-resistance was
established.