Al‐Si contacts have been formed by implantation of As ions through Al‐Si interfaces followed by heat treatment at 400–500 °C for 10 min. The erosion of Si proceeds uniformly in contact areas at the sintering temperatures. Diodes using Al‐Si contacts produced by this technique have been fabricated on thinn+layers inp‐type Si substrates with junction depths of 0.35 &mgr;m and contact areas of 5 &mgr;m2. The average leakage current per diode (with an approximate junction area of 14×26 &mgr;m2) is about 10−8A, as compared to the leakage current of 10−5A for diodes with Al‐Si contacts prepared by sintering of Al on Si at 420 °C. We attribute the improvement to the uniformity of Si erosion after the interfacial oxide has been dispersed by ion irradiation.