Formation of W underlayer by switching bias sputtering to plug 0.25 μm contact holes

Abstract

Physical vapor deposion by a newly developed switching bias sputtering method for the formation of both adhesion and barrier metal underlayers on 0.25 μm contact/via holes with sufficient step coverage has been investigated as a hole filling process. The method features alternating operation of sputtering to deposit and resputtering of the film to enhance step coverages of the side walls by resputtering of the bottom. It was found that W films formed for holes with aspect ratios of 3.0–3.5 gave step coverages of 17%–23% for the side wall and 30%–33% for the bottom. The resistivity of W films deposited on planar surfaces was 10.5 μΩ cm, similar to values for W films deposited by conventional direct current (dc) sputtering. The deposition rate of the sputtering was 50%–80% of the rate of conventional dc sputtering.