Rapid thermal processing of WSi, contacts to InP in low-pressure N2:H2 and tertiarybutylphosphine ambients

WSi, thin films deposited on InP substrates have been investigated for possible use as refractory ohmic contact materials for self-aligned laser devices. The films have been rf diode sputtered using various Ar gas pressures from a single commercial target composed of W and Si with an atomic ratio of 1:l. Following the deposition, the WSiJInP samples were rapid thermal processed using a rapid thermal metalorganic chemical vapor deposition system in a controlled low-pressure ambient of NsH, (9:l) and tertiarybutylphosphine. The as-deposited films ( 100 nm thick) were amorphous but crystallized iI? the temperature range of 600-650 “C. The WSi, phase forms first at 600 “C and then the W,Si3 nucleate with further heating at 650 “C. As a result of the crystallization, a reduction in the specific contact resistance to a value of 7.5 x 10 6 0, cm* and a decrease in the sheet resistance to values lower than 2 n/Cl were observed. In addition, a significant reduction in the internal stress and an improvement in the WSi,-to-InP adhesion were found, demonstrating the potential of WSi, as a contact material for InP-based self-aligned devices.