Comparing ICP and ECR etching of HgCdTe, CdZnTe, and CdTe

The surface roughness of inductively coupled plasma (ICP)-etched CdTe is greater than that of electron cyclotron resonance (ECR)-etched CdTe. This greater roughness is undesirable for further processing of the material. Lower-frequency plasma excitation from the ICP is more efficient at cracking hydrogen than the high-frequency plasma excitation of ECR. In binary semiconductors it is important to balance removal of both constituents. Bombardment controls the removal of the metal constituent while hydrogen removes the tellurium. Research performed with ECR plasma processing on HgCdTe shows that reducing the pressure can greatly reduce hydrogen ionization. Applying this to ICP it can be shown that reduced pressure greatly improves the morphology of CdTe. This balanced etching also greatly improves etch rate and selectivity of HgCdTe.