W/WNx as a low-resistance gate material and local interconnect

In this study we continue the proposal to use an in-situ deposition of an interfacial WNx film as a process that enables the use of W as a low-resistance gate and local interconnect layer. We have previously found that an interfacial WNx layer provides greatly improved adhesion, nucleation, and thermal stability of the subsequent W deposition [1]. In the present work we are extending the scope of the study to investigate the deposition characteristics of the plasma enhanced chemical vapor deposition method in more detail. The variation in film resistivity and its relationship to film morphology is shown to be controlled by the gas flow ratio of NH3/WF6. The ability to nucleate continuous 10 nm WNx films is demonstrated by comparing film thickness and resistivity. The persistent P-W phase in W films that occur without a nucleation layer of amorphous WN, is found to result from a combination of dendritic growth and voids. Impurity dopant diffusion is investigated using secondary ion mass spectroscopy (SIMS). That WN, is an effective diffusion barrier to boron and phosphorous, even when deposited directly on silicon damaged by 5 x 10(15) cm(-2) implants, suggests the suitability as a contact barrier. Oxidation behavior of WNx was investigated and found to be essentially the same as that of pure W.