Ultra-shallow junction formation using silicide as a diffusion source and low thermal budget

Ultra-shallow p/sup +//n and n/sup +//p junctions were fabricated using SADS (silicide-as-diffusion-source) and ITS (ion-implantation-through-silicide processing) of 45-nm CoSi/sub 2/ films (3.5 Omega / Square Operator ) using a low thermal budget. The best junctions of either type were made by moderate 10-s RTA (rapid thermal annealing) at 800 degrees C, where the total junction depth, counting the silicide thickness, is believed to be under 60 nm. Diffusion-limited current predominated down to 50 degrees C in junctions made under these conditions. The initial implantation energy had only a minor effect on the junction leakage, where shallower implants required slightly higher temperatures to form low leakage diodes, resulting in diodes which were somewhat more susceptible to shorting during silicide agglomeration at high temperatures. The ITS scheme, where dopant is implanted slightly beyond the silicide, gives an equally low leakage current. Nevertheless, the ITS scheme gives deeper junctions than the SADS process, and it is difficult to control the position of the ITS junction due to silicide/silicon interface fluctuations.<
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