THERMAL-STABILITY OF W ON RTCVD SI1-XGEX FILMS

Thermal reaction of W with Si0.67Ge0.33 films epitaxially grown by RTC VD was investigated in the temperature range 300-1000 degrees C. The r eaction products were investigated by Rutherford backscattering spectr oscopy, energy dispersive spectrometry, X-ray diffraction and secondar y ion mass spectrometry. The progress of the reaction was also followe d by using sheet resistance measurements. The reaction of W with Si0.6 7Ge0.33 is similar to that of W with silicon. W reacts with silicon at 700 degrees C to form tetragonal WSi2. The Ge content in the silicide is lower than that of the as-deposited alloy. It is shown that the pr esence of a metal overlayer may significantly modify the thermal stabi lity of the alloy. Thus, an annealing at deposition temperature is suf ficient to lead to the formation of non-homogeneous Si1-xGex unreacted alloy below the silicide film.