Pd/Ge/Ti/Pt ohmic contact to n-type InCaAs was investigated. Minimum specific contact resistivity of $3.7 imes10^{-6}; Omega extrm{cm}^2$ was achieved by rapid thermal annealing at $400^{circ}C$ for 10 seconds. This was related to the formation of Pd-Ge compounds and the in-diffusion of Ge atoms to InGaAs surface. However, the specific contact resistivity increased slightly to $low-10^5; Omega extrm{cm}^2$ in the case of longer annealing time. Superior ohmic contact and non-spiking planar interface between ohmic materials and InGaAs were maintained after annealing at high temperature. Therefore, this thermally stable ohmic contact system is a promising candidate for compound semiconductor devices.