An Etching Mechanism of Ta by Chlorine‐Based Plasmas

Abstract

Ta is easily etched by chlorine plasmas in spite of the low vapor pressure of the reaction product, i.e., Ta‐chloride. In order to clarify the etching mechanism of Ta in relatively low temperature conditions below 25°C, optical emissions were monitored. Contrary to the case of Al etching, the emission intensity of atomic chlorine, which is assumed to be an active etching species, becomes stronger during Ta etching as if it is a reaction product itself. This suggests that molecular chlorine reacts with Ta as strong as atomic chlorine, and that the reaction, especially the desorption process of the reaction product, is strongly assisted by ion bombardment, and that the reaction product, , is sputtered off the surface to form partly as decomposed and atomic chlorine.