A trilevel lift‐off process using a soluble polyimide as the base layer is described. Al–Cu–Si metallizations are obtained with good pattern fidelity over 1 μm high structures with the use of substrate metallization temperatures of up to 325 °C. The process routinely produces metallizations 1 μm thick with linewidths less than 1.5 μm and pitch less than 2.5 μm.