A system and method is disclosed for providing an etch procedure to facet the top corners of a via in a semiconductor device. In a typical example of the SiGeC heterojunction bipolar transistor, the collector has a layer of n-type single-crystal Si and a layer of n-type single-crystal SiGe, the base is a layer of heavily doped p-type single-crystal SiGeC, and the emitter is a layer of n-type single-crystal Si. As a result, the impeller can be smoothly activated to drive by controlling a coil current.