Mo/TiW contact for VLSI applications

A molybdenum and titanium-tungsten double-layer contact metallization was developed for VLSI applications. The thin TiW layer produces good ohmic contact and thermal stability with n+ silicon, p+ silicon, and polysilicon up to 650°C without any spiking. The contact formation process, including the etching of about 1-µm size contacts and tightly pitched lines 1.5-µm wide was developed. The specific contact resistance for n+ silicon and polysilicon contacts was less than 35 Ω.µm²and that for the p+ silicon contact resistance was within a range of 35 to 85 Ω.µm². There is no junction leakage degradation for the p+ up to 750°C, whereas some degradation of the n+ observed above 600°C is in a tolerable range. The mechanism and cause of the contact resistance and leakage current changes with sintering temperature were studied by means of x-ray, SIMS, TEM, and SEM.