Process for making a contact structure including polysilicon and metal

Abstract

A multi-layer contact process is described for providing contact to a shallow semiconductor region forming a semiconductor PN junction and with a silicon semiconductor body. The multi-layer structure includes a layer of polycrystalline silicon doped with an impurity of the same conductivity type as that of the semiconductor region. A first layer of a refractory alloy is deposited over the polycrystalline silicon layer to provide electrically stable interface therewith. A second layer of another refractory metal or alloy is deposited over the first refractory metal alloy layer and serves to protect the shallow PN junction against current leakage failure. A third layer of interconnect metal is deposited over the multi-layer contact structure. The resulting structure provides a low resistance ohmic contact to a shallow semiconductor region with improved electrical characteristics.