Formation of self-aligned TiSi2 for very large scale integrated contacts and interconnects

Abstract

In this paper, we present the results of a study on self-aligned TiSi2 formation. TiSi2 was formed by a rapid thermal anneal (RTA) of a sputtered Ti film on crystalline Si and on phosphorus doped poly-Si at a temperature from 600 to 1100 °C. A film resistivity of 16 μΩ cm has been achieved after an RTA at 800 °C for 10 s. Auger electron spectroscopy analysis indicated that a stoichiometric TiSi2 below a surface TiNxOy layer was formed by RTA in N2. The Si consumption during RTA in N2 was less than in Ar ambient due to the TiNxOy formation. In addition, RTA in N2 resulted in less lateral silicide growth than in Ar. Ti film started to react with the underlying SiO2 layer at 600 °C for 30 s and titanium oxide and titanium silicide were observed after RTA at 800 °C for 30 s. The TiSi2 formation on POCl3 doped poly-Si and moderately doped crystalline Si exhibited the same characteristics as on bare Si. Secondary ion mass spectroscopy analysis indicated that As+ and B+ did not pile up at the TiSi2/Si interface. From the measurements of lateral silicide growth lengths after stripping the ‘‘unreacted Ti’’ on oxide, a process window of RTA temperature and time for forming self-aligned silicide was determined. Good I–V characteristics of silicided diodes and salicide metal–oxide semiconductor field-effect transistors have been obtained.