Surface reaction and B atom segregation in ECR chlorine plasma etching of B-doped Si1−xGex epitaxial films

The dry etching characteristics of B-doped Si1−xGex epitaxial films have been investigated using an electron–cyclotron–resonance chlorine plasma. The etch rate of Si1−xGex films increases with increasing Ge fraction and decreases with B doping. In particular, for the chlorine radical-dominant etching, the etch rate of B-doped films decreases with increasing etching time. The phenomena are caused by the segregation of B atoms on the etched surface. The segregated B atom concentration for B-doped Ge film is larger than that for B-doped Si film. It is also suggested that the decrease of B atom concentration when increasing the etching time for the Si1−xGex films is caused by the segregation of Si atoms on the etched surface.