Study of C49-TiSi2 and C54-TiSi2 formation on doped polycrystalline silicon using in situ resistance measurements during annealing

In situ resistance versus temperature or time for reactions between 32 and 57.5 nm of titanium and undoped or doped polycrystalline silicon (boron, arsenic, or phosphorus, 7.9×1019–3.0×1020/cm3) has been measured and no clear correlation was found between the activation energy for the formation of the industrially important low-resistance C54-TiSi2 phase and its formation temperature. It is also demonstrated that with certain moderate doping levels typical of complementary metal-oxide-semiconductor manufacturing, boron or phosphorus-doped polycrystalline silicon can delay the formation of C54-TiSi2 more than arsenic-doped polycrystalline silicon. Finally, by using in situ resistance measurements, it is demonstrated that the ‘‘two-step’’ thermal annealing process similar to a salicide process requires less thermal annealing time at high temperatures to form C54-TiSi2 than a single ‘‘one-step’’ thermal anneal at the same temperature.