LOW-TEMPERATURE FORMATION OF C54-TISI2 USING TITANIUM-ALLOYS

We demonstrate that the temperature at which the C49 TiSi2 phase trans forms to the C54 TiSi2 phase can be lowered more than 100 degrees C by alloying Ti with small amounts of Mo, Ta, or Nb. Titanium alloy blank et films, containing from 1 to 20 at. % Mo, Ta, or Nb were deposited o nto undoped polycrystalline Si substrates. The temperature at which th e C49-C54 transformation occurs during annealing at constant ramp rate was determined by in situ sheet resistance and x-ray diffraction meas urements. Tantalum and niobium additions reduce the transformation tem perature without causing a large increase in resistivity of the result ing C54 TiSi2 phase, while Mo additions lead to a large increase in re sistivity. Titanium tantalum alloys were also used to form C54 TiSi2 o n isolated regions of arsenic doped Si(100) and polycrystalline Si hav ing linewidths ranging from 0.13 to 0.56 mu m. The C54 phase transform ation temperature was lowered by over 100 degrees C for both the blank et and fine line samples. As the concentration of Mo, Ta, or Nb in the Ti alloys increase, or as the linewidth decreases, an additional diff raction peak appears in in situ x-ray diffraction which is consistent with increasing amounts of the higher resistivity C40 silicide phase. (C) 1997 American Institute of Physics. [S0003-6951 (97)02550-3].