High reliability interconnect technology with tungsten-barrier metal in next generation

The purpose of this paper is to reveal the mechanism of discoloration which leads to a via open problem and to demonstrate the effect of W-barrier metal on W-stud process to prevent this problem. In this paper we describe some experiments aimed at solving the discoloration of CVD-W film. These experiments revealed the mechanism whereby this problem leads to degradation of the reliability of W-stud vias because of high via resistance. It is confirmed that using sputtered tungsten film as a barrier metal is very effective in preventing not only WF₆ attack in CVD-W process but also discoloration due to residual polymer generated in the via etching process. It seems that, in future generations of semiconductors, using sputtered tungsten film as a barrier metal will be effective in preventing high via resistance, which leads to the reliability problem of the W-stud via.