Redistribution of excess Si in chemical vapor deposited WSix films upon post-deposition annealing

Abstract

WSix films of three different compositions (X>2.0) were deposited by chemical vapor deposition onto polysilicon and Si3N4 coated substrates and subsequently annealed in N2 at 1000 °C. The redistribution of the excess Si was studied using Auger depth profiling and cross-sectional scanning electron microscopy techniques. For polysilicon sublayers the excess Si segregates to the polysilicon interface with a resulting increase in polysilicon thickness and decrease in WSix thickness in proportion to the excess Si content. For Si3N4 sublayers the excess Si precipitates within the WSix layer, but preferentially toward the free surface. Changes in surface and interface topography resulting from the Si redistribution are presented. The kinetics of the Si redistribution observed in the depth profiles are correlated with resistivity measurements.