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

Abstract

In this study we investigated the effects of SF 6 and CF 4 plasma pretreatments on the adhesion and junction leakage characteristics of the selective CVD W films by SiH 4 reduction of WF 6 on the Si substrate. The SF 6 plasma pretreatment performed in situ prior to W deposition to remove the polymer films in contact holes results in enhacement of the adhesion of W films to the Si substrate but degradation of junction leakages due to vertical and lateral Si consumptions. The CF 4 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 fir thick W films. The selective CVD W films deposited by the three step process of SiH 4 reduction/in situ annealing/SiH 4 reduction was found to have both good adhesion and low junction leakage characteristics