METALLIZATION OF W/CO-TI/SI AND SIMULTANEOUS FORMATION OF DIFFUSION BARRIER AND SHALLOW COSI2 CONTACT IN NORMAL FLOWING-NITROGEN FURNACE

Abstract

A structure of W-Ti/CoSi2/Si can be formed from an appropriate metallization system of W(400 angstrom)/Co63Ti37(360 angstrom)/Si at temperatures from 620 to 760-degrees-C in a normal flowing-nitrogen ambient. The W-Ti alloy layer is only slightly oxidized on the shallow surface and can be used as a diffusion barrier between the aluminum and silicide. Furthermore, silicide lateral growth does not occur in this silicidation scheme. However, an additional intermediate Ti-silicide and/or Ti-oxide as well as a Ti-oxide layer on the surface will be formed if the content of Ti in the Co-Ti alloy exceeds that required to saturate in the overlying W film, e.g., W (400 angstrom)/Co63Ti37(840 angstrom)/Si. The Al/W-Ti/COSi2/p+ n diodes with metallization using this scheme are able to maintain the integrity of I-V characteristics with a post-Al annealing at 550-degrees-C for 20 min. In addition, epitaxy of CoSi2 occurs in this metallization system.