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 l ow-resistance gate and local interconnect layer. We have previously fo und 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 investi gate the deposition characteristics of the plasma enhanced chemical va por deposition method in more detail. The variation in film resistivit y 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 resistivi ty. The persistent P-W phase in W films that occur without a nucleatio n layer of amorphous WN, is found to result from a combination of dend ritic growth and voids. Impurity dopant diffusion is investigated usin g secondary ion mass spectroscopy (SIMS). That WN, is an effective dif fusion barrier to boron and phosphorous, even when deposited directly on silicon damaged by 5 x 10(15) cm(-2) implants, suggests the suitabi lity as a contact barrier. Oxidation behavior of WNx was investigated and found to be essentially the same as that of pure W.