Pd/Si/Ti/Pt ohmic contact to n-type InGaAs was investigated. As-deposited contact showed non-ohmic behavior, and high specific contact resistivity of $5 imes10^{-3}Omega extrm{cm}^2$ was achieved by rapid thermal annealing at $375^{circ}C$ for 10 seconds. However, the specific contact resistivity decreased remarkably to $1.7 imes10^{-6}Omega extrm{cm}^2$ and $2 imes10^{-6}Omega extrm{cm}^2$ at $375^{circ}C$/60sec and $425^{circ}C$/10sec, respectively. Superior ohmic contact and non-spiking planar interface between ohmic materials and InGaAs were maintained even at $450^{circ}C$, therefore, this thermally stable ohmic contact system is a promising candidate for compound semiconductor devices.