Suppression of the Phase Transition to C54 TiSi2 due to Epitaxial Growth of C49 TiSi2 on Si(001) Substrates in Silicidation Process

Tile epitaxial C49 TiSi2 formed after annealing of Ti films deposited on Si(001) substrates has been studied by grazing-incidence X-ray diffraction. The relations C49 TiSi2(101)parallel to Si(001), C49 TiSi2(100)parallel to Si(001), and C49 TiSi2(010)parallel to Si(001) are observed on a highly BF2-implanted substrate, and the a or b face of C49 is sharply orientated toward the directions deviating +/-5 degrees from Si(110) on a clean substrate in ultrahigh vacuum (UI-IV). These epitaxial C49 grains are thermally stable and difficult to transform into the C54 phase even after annealing at high temperature. In contrast, ramdomly distributed C49 grains have been observed on unimplanted and low-dosed substrates and for thick Ti films in UHV. These polycrystalline Cia grains are thermally unstable and easily transformed into the C54 phase. The influence of implantation and UHV process on the growth of the epitaxial C49 and the phase transition of C49 to C54 are discussed.