CH3I VAPOR ETCHING OF MASKED AND PATTERNED GAAS

CH3I vapor etching of masked and patterned GaAs substrates has been experimentally investigated. For GaAs samples masked with silicon nitride stripes that are wider than 30 pm, the etch depth increased compared to unmasked samples, the magnitude of which increased with increasing mask width. Etching of bulk substrates of (111)Ga and (111)As GaAs revealed a dependence of etch rate on crystal orientation, with (111)Ga > (100)GaAs > (111)As. Increasing etch temperature reduced the orientation dependence of etch rates. Orientation dependence of etch rates was also observed on non-planar GaAs substrates patterned to expose different orientations on wet-etched groove structures. In this case, etch rate differences between the different orientations were amplified when compared to the bulk substrate results. Finally, it was found that the extent of mask undercutting depended on the direction of mask stripes in a fashion consistent with the orientation reactivity results. Mask stripes on (100)GaAs oriented in the [01 (1) over bar] direction were severely undercut whereas stripes oriented in the [011] direction were undercut less.