Chemical vapour deposition tungsten film growth studied by in situ growth stress measurements

Abstract

In this paper we present in situ measurements of the wafer curvature during nucleation and growth of W films deposited by chemical vapour deposition (CVD) on Si substrates. Because of the absence of stress relaxation mechanisms in the films, these measurements directly reflect the growth stress in the W films. The growth stress development is measured during self-limiting W film growth by the Si(100) reduction of WF 6 and during continuous W film growth by the H 2, SiH 4, and GeH 4 reduction of WF 6. It is shown that these measurements provide detailed information on the growth kinetics (for the Si reduction of WF 6) as well as the (high) growth stresses themselves. High stress gradients are observed in the growth direction of the films. In general the growth stresses range from highly tensile during the initial stages of growth, to compressive in an intermediate region and tensile again in the thick film regime. The average film stress decreases with increasing deposition temperature. The process-dependent growth stresses reported in this paper can be used to engineer the magnitude of the average film stress in W CVD metallization of integrated circuits.