REACTIVE ION ETCHING OF HGCDTE WITH METHANE AND HYDROGEN

Reactive ion etching (RIE) of HgCdTe using hydrogen and methane/hydrogen mixtures has been studied. The hydrogen RIE was found to form a Cd-rich residue which resulted in a very rough surface and which gradually inhibited via formation. The addition of methane (approximately 25%) resulted in smoother etched surfaces and ultimately deeper vias without the residue. Aspect ratios (via depth to width) of approximately 0.9 were attained using this RIE process. A very strong HgCdTe surface orientation dependence was noted regarding both etch rate and etched surface morphology. For short etch times, the [111B] surface etched faster than the [100] surface, which etched faster than the [111A] surface. On the other hand, the [111A] etched surface was far smoother than either the [111B] or [100] surfaces.