SPECTROSCOPIC ELLIPSOMETRY INVESTIGATION OF NICKEL SILICIDE FORMATION BY RAPID THERMAL PROCESS

Titanium and cobalt silicides are used widely in microelectronics fabrication. There are limitations for both silicides. With TiSi2, a linewidth dependence of sheet resistance for lines narrower than 0.35 μm has become dramatic. The transformation from the high-resistivity C49 phase to the low-resistivity C54 TiSi2 phase is nucleation limited. With CoSi2 there is much less linewidth dependence of the sheet resistance, but more Si is consumed to form the silicide. With the use of NiSi, these problems can be avoided as reported so far in literature. In this article we shall report an investigation of rapid thermal silicidation of nickel on single crystalline silicon wafers in the annealing range of 150–1150 °C. It has been found that there are five zones in the dependence of sheet resistance on silicidation temperatures as follows: below 175, 175–350, 350–650, 650–900, and above 900 °C. In order to extensively study the phase sequence for Ni/Si reactions and the kinetics of nickel silicide formation corresp...