Rapid thermal chemical vapor formation of TiSi2: An alternative refractory metallization process for device fabrication

Scaling of MOSFETs into the deep submicron regime requires novel metallization schemes to form low resistivity contacts on ultra-shallow junctions. In this paper, we present our recent results on rapid thermal chemical vapor formation (RTCVF) of TiSi2. In this process, the gaseous Ti source, TiCl4 (g), reacts with solid Si to form C54 TiSi2 (s) at temperatures as low as 700 degrees C with a resistivity of 15-20 mu Omega-cm without a follow-up anneal. In this paper, we explore the previously reported barrier for nucleation of TiSi2 on Si at temperatures below 800 degrees C. Without proper surface preparation, this barrier results in an incubation time which can vary according to the conditions of the surface and the deposition environment. We show that contrary to general belief, surface morphology instead of surface cleanliness is the most likely contributor to this barrier. We also show that if in-situ deposition of a Si-Ge layer precedes TiSi2 formation, the incubation time can be completely eliminated. Experiments performed in a temperature range of 650 degrees C - 800 degrees C indicate an approximate activation energy of 100 kJ/mol. The process provides excellent selectivity to both SiO2 and Si3N4 and little growth rate dependence on patterns in the 2 mu m - 200 mu m regime.