Adhesion and leakage current characteristics of selective CVD tungsten films on the silicon substrate

Abstract
In this study we investigated the effects of SF₆ and CF₄ plasma pretreatments on the adhesion and junction leakage characteristics of the selective CVD W films by SiH₄ reduction of WF₆ on the Si substrate. The SF₆ plasma pretreatment performed in situ prior to W deposition to remove the polymer films in contact holes results in enhancement of the adhesion of W films to the Si substrate but degradation of junction leakages due to vertical and lateral Si consumptions. The CF₄ plasma pretreatment performed as the last step of the reactive ion etching for contact window opening produced the W/Si contacts of good adhesion, low contact resistances and low junction leakages for thin W films, while it produced the W/Si contacts of poor adhesion and high contact resistances for thick W films. The selective CVD W films deposited by the three step process of SiH₄ reduction/ in situ annealing / SiH₄ reduction was found to have both good adhesion and low junction leakage characteristics.