The effect of nitrogen pre-annealing on the sidewall oxidation of WSi/sub x/ and on the related electrical properties of WSi/sub x//poly Si gate structure

N/sub 2/ pre-annealing at 900/spl deg/C for 20 minutes was effective to suppress undesirable sidewall oxidation of WSi/sub x/ in a tungsten polycide gate structure during post oxidation processing. Contact resistance measurements show that the N/sub 2/ pre-annealing improved the metal contact resistance on the gate while it degraded the tungsten polycide contact resistance on the gate. The contradictory effects on two contact resistances on the gate are attributed to Si out-diffusion from dichlorosilane-based tungsten silicide (DCS-WSi/sub x/) during N/sub 2/ pre-annealing. From experiment and simulation data, it is verified that the additional thermal budget of N/sub 2/ pre-annealing does not affect the device parameters of n- or p-MOSFETs at gate length L=10 /spl mu/m. It is considered that the segregation of fluorine (F) atoms from DCS-WSi/sub x/ on to the gate oxide caused the increase in threshold voltage (V/sub T/), the reduction of saturation current (I/sub DSAT/), and the increase in subthreshold slope of n-MOSFETs. However, no significant changes were observed in p-MOSFETs. On the other hand, the gate oxide characteristics were not degraded by N/sub 2/ pre-annealing.