Wet-etch bulk micromachining of (100) InP substrates

The study focused on object formation in (100) InP by etching in 3HCl:1H(3)PO(4) through convex and concave square mask patterns of varied orientation and size. Their upper right-hand-side corners were aligned to [0 (1) over bar0], and to 15degrees, 30degrees and 45degrees off [0 (1) over bar0] to [0 (1) over bar(1) over bar]. Some [0 (1) over bar(1) over bar]-oriented convex squares had [01 (1) over bar]- and [0 (1) over bar1]-oriented corners compensated with rectangular extensions. The concave patterns led to objects with ordinary slow-etching or etch-stop facets along sides in line within [0 (1) over bar0]-[0 (1) over bar1] and with ordinary and re-entrant facets along sides in line within [00 (1) over bar]-[0 (1) over bar(1) over bar]. The convex patterns ([0 (1) over bar0], 15degrees and 30degrees) led to objects initially confined by fast-etching facets at corners and slow-etching or etch-stop facets at sides (ordinary between [0 (1) over bar0] and [0 (1) over bar1], and re-entrant between [00 (1) over bar] and [0 (1) over bar(1) over bar]). The side facets were eliminated by the progress of the corner ones. They ([0 (1) over bar0]-oriented patterns) proceeded at rates almost independent of size before the eradication of the side facets, after which they proceeded faster. The [0 (1) over bar(1) over bar]-oriented convex patterns led to objects confined only by fast-etching facets. The objects developed at rates that considerably depended on pattern size and etching time. Objects under small patterns developed faster compared to those under large ones. The [0 (1) over bar(1) over bar]-oriented corner-compensated patterns led to pyramidal objects confined by facets related to (110), (1 (1) over bar0), (101) and (10 (1) over bar).