NiCr thin film resistor integration with InP technology

We present a study of nickel chromium (NiCr) thin film resistors deposited on InP substrate. In contrast to previously published work, the NiCr film resistance changes by a factor of 2.5 after temperature exposure to 250 degrees C in air. In order to explain this effect, XPS and SIMS tests were performed on NiCr films as-deposited and with temperature treatment. Annealed samples show strong in and out diffusion of Ni and In, respectively. Interfacial reactions were described explaining the severe resistivity decrease. As a solution, a SiN diffusion barrier between NiCr and InP is proposed and applied.