Characterization of W/WSIx/Si Contact Structures under Thermal Annealing for Some X Values

Abstract

ABSTRACTThermal stability of W/WSix/Si (X=1.4, 2.1, 2.5) contact structures has been characterized at annealing temperature up to 900°C. Thermal reaction in these contact structures was strongly affected by the X values of deposited WSix films. The X values were presicely controlled by a novel co-sputter deposition apparatus. After annealing at 900°C, in the samples of X=1.4 and 2.1, the W films were stably maintained. On the other hand, in the sample of X=2.5, the structure changed into the WSi2. 2/Si resulting in the disappearance of the W film. The silicidation of the W film in the sample of X=2.5 was likely due to a diffusion of Si into the W film through the precipitated region of the excess Si in the tungsten silicide film. The W/WSi2.2/Si structure can provide the electrically stable W-Si contact at annealing temperature up to 800°C.