Advances in the formation of C54-FiSi₂ with an interposed refractory metal layer some properties

Abstract

The formation of TiSiz has been intensively studied because of its great technological importance in the microelectronics industry. TiSi2 may exist either as the C49 phase (with a resistivity of 60-70 pL2 cm) or as the C54 phase (with a lower resistivity of 15-20 j.& cm). The desired C54 phase usually forms as a result of a polymorphic phase transformation from the previously formed C49 phase. The latter forms as a result of the Ti-Si interaction. The main issue of this sequence of phase formation is the dependence of the transformation temperature on pattern dimensions and dopant concentrations in Si. As the line width of polycrystalline Si runners decreases, the formation temperature has to be increased in order to obtain the C54 phase. With the upper-limit of the process temperature determined by the formation of shallow junctions and the thermal stability of TiSi2/Si structures, the process window can eventually vanish as a result of the increased formation temperature.An important breakthrough has recently been made by Mann et al.[ 11 : the temperature needed to transform the C49 phase to the C54 phase is reduced by 100 to 150" by MO or W