Novel resistance reduction and phase changes of contacts to n-type InP by rapid thermal annealing

Abstract

ABSTRACTWe studied the influence of n-metal alloy on the long wavelength InP device performance. Various alloy schemes of rapid thermal annealing (RTA) were experimented to obtain the optimized contact resistance for the n-InP/AuGe/Ni/Au/Cr/Au metallization systems. Significant resistance reduction was achieved at 390°C for 45sec with wafer flattening step at 310°C. Using scanning transmission electron microscopy (STEM) and Auger electron spectroscopy (AES) analyses, we showed that resistance was correlated with interfacial reaction at the n-InP/metal. For the high resistance devices, little interfacial reaction between n-InP and Au occurred. For the low resistance devices, significant out-diffusion of P in the bottom Au and Ni layers occurred, forming Au-P and Ni-P metallic compounds. In addition, accumulation of Ge in the Ni layer was also detected. We suggest that Ni-P is very critical in obtaining low contact resistance for n-InP.