FORMATION OF BILAYER SHALLOW MOSI2/COSI2 SALICIDE CONTACT USING W/CO-MO ALLOY METALLIZATION

Abstract

A very simple process to form a bilayer shallow MoSi2/CoSi2/Si silicided contact using W/Co54Mo46/Si bilayer alloy metallization has been developed. Two-step annealing in a conventional flowing-nitrogen furnace is employed. The first annealing is performed at a temperature of 500-600-degrees-C, with the W film passivating the underlying Co-Mo alloy layer from being oxidized and consuming some Co. A shallow contact is feasible by selectively etching away the remaining outer layer of the Mo-dominant Mo-Co alloy (or W-Co alloy) phase to deduct the metal source which would finally be transformed into silicides. Silicide lateral growth which is observed during the silicidation of Co on Si does not occur in the present system. This is presumably because the formation of CoSi2 is not preceded by Co2Si or CoSi due to the nonrich Co source in the Co-Mo alloy system. The second annealing performed at a higher temperature of 700-950-degrees-C is to further transform the CoSi2 and mixed-silicide layers obtained after the first annealing into separate layers of MoSi2 and CoSi2.