CHEMICAL-VAPOR-DEPOSITION TUNGSTEN FILM GROWTH STUDIED BY INSITU GROWTH STRESS MEASUREMENTS

In this paper we present in situ measurements of the wafer curvature d uring nucleation and growth of W films deposited by chemical vapour de position (CVD) on Si substrates. Because of the absence of stress rela xation mechanisms in the films, these measurements directly reflect th e growth stress in the W films. The growth stress development is measu red during self-limiting W film growth by the Si(100) reduction of WF6 and during continuous W film growth by the H-2, SiH4, and GeH4 reduct ion of WF6. It is shown that these measurements provide detailed infor mation on the growth kinetics (for the Si reduction of WF6) as well as the (high) growth stresses themselves. High stress gradients are obse rved in the growth direction of the films. In general the growth stres ses range from highly tensile during the initial stages of growth, to compressive in an intermediate region and tensile again in the thick f ilm regime. The average film stress decreases with increasing depositi on temperature. The process-dependent growth stresses reported in this paper can be used to engineer the magnitude of the average film stres s in W CVD metallization of integrated circuits.