METHOD FOR LOWERING THE PHASE TRANSFORMATION TEMPERATURE OF A METAL SILICIDE

摘要

The phase transformation temperature of a metal silicide layer formed overlying a silicon layer on a semiconductor wafer is lowered. First, a refractory metal is disposed proximate to the surface of the silicon layer, a precursory metal is deposited in a layer overlying the refractory metal, and the wafer is heated to a temperature sufficient to form the metal silicide from the precursory metal. The precursory metal may be a refractory metal, and is preferably titanium, tungsten, or cobalt. The concentration of the refractory metal at the surface of the silicon layer is preferably less than about 101 atoms/cm3. The refractory metal may be Mo, Co, W, Ta, Nb, Ru, or Cr, and more preferably is Mo or Co. The heating step used to form the silicide is performed at a temperature less than about 700.degree.C, and more preferably between about 600-700.degree.C. Optionally, the wafer is annealed following the step of disposing the refractory metal and prior to the step of depositing the precursory metal layer. Preferably, this annealing step is performed at a wafer temperature of at least about 900.degree.C.