The etching behavior of tungsten (W) with respect to the orientation of the grain boundary and masking layers

In this paper, we present the study of the tungsten (W) etch rate as a function of different masking materials: Ti/TiN and SiO 2. In addition, the impact of the W grain boundary orientation on the etch rate is established. With the use of a SiO 2 masking layer, the W etch rate is five times higher compared to etching with a Ti/TiN masking film. The blanket W etch rate is the average of these two values. The difference of etch rate with respect to the orientations of grain boundaries is only detected in pure SF 6 plasma.