Deep mesa process for fabricating monolithic integrated Schottky barrier diode for millimeter wave mixers

摘要

A method of fabricating gallium arsenide devices in which contact isolation is provided by a deep mesa step structure. Step coverage of deposited conductive films is facilitated by preferential orientation of the non-centrosymmetric crystal substrate and wet anisotropic etching that provides a sloped step. Problems of fine line definition of the Schottky anode contact in the photolithographic process are addressed by a two-step exposure of a single layer of thick photoresist followed by a chlorobenzene soak prior to development that ensures a retrograde resist profile needed for good lift-off of undesired evaporated metal. Mesas as deep as 7 mu m have been obtained, which permit the fabrication of monolithic planar mixer millimeter-wave diodes with low series resistance and reduced parasitic capacitance.