Wet-etch bulk micromachining of (100) InP substrates

Abstract

The study focused on object formation in (100) InP by etching in 3HCl:1H3PO4 through convex and concave square mask patterns of varied orientation and size. Their upper right-hand-side corners were aligned to , and to 15°, 30° and 45° off to . Some -oriented convex squares had - and -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 and with ordinary and re-entrant facets along sides in line within . The convex patterns (, 15° and 30°) led to objects initially confined by fast-etching facets at corners and slow-etching or etch-stop facets at sides (ordinary between and , and re-entrant between and ). The side facets were eliminated by the progress of the corner ones. They (-oriented patterns) proceeded at rates almost independent of size before the eradication of the side facets, after which they proceeded faster. The -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 -oriented corner-compensated patterns led to pyramidal objects confined by facets related to (110), , (101) and .

Inverse Metal-Assisted Chemical Etching Produces Smooth High Aspect Ratio InP Nanostructures

“…Tapered anisotropic wet-etching behavior of InP had been reported previously using HCl-based solutions through the use of a lattice-matched InGaAs layer as an etching mask and was attributed to a crystal orientation-dependent etch rate. 39 The etch profile observed here in the presence of metals can be explained by the competition between oxidation and material dissolution during etching. It is well known that the etch rates are enhanced if a metal with a higher work function is used as a catalyst during MacEtch of Si, 1 GaN, 40 and InP.…”

Formation of micro- and nano-striations at (211)A facets during wet etching of InP in HCl

“…On the anisotropy of InP dissolution in 3HCl:1H 3 PO 4 we previously reported in detail [9,10]. It can be summarised as follows: within the (100) plane there are four very narrow (approximately 10 • ) angular sectors each centred along 001 directions which are significant for undercutting.…”

“…The first stage of the development of the "in-facet" features was studied previously [9]: upon the onset of etching the comb teeth were undercut only at their convex corners as the result of the revelation of fast etching corner facets. In contrast to this the orthogonal sections of the teeth were not underetched due to the revelation of stop-etch facets: (211)Arelated facets along [011] and perpendicular ones along [011] [9]. The first stage finished when the progress of corner facets eliminated the (211)A-facets along the [011]-oriented edges of the teeth.…”

“…Outside the four intervals mask undercutting is vastly or completely suppressed [10]. Also, when (100) InP is patterned through convex-cornered mask patterns, they are undercut at the corners through the revelation of a specific facet which proceeds in a direction approximately 1.3 • off 001 towards [011] or [011] [9].…”

Precise Formation of Dovetail Structures for InP-Based Devices

“…It has been proposed that different crystallographic planes of InP have different chemical reactivity. 11 Without the presence of strain the etching continues until the acid molecules reach the slow etching plain (111A). 12 (111A) contains Indium atoms, each of which have three bonds to phosphate atoms on the underlying (111B) plane as shown in Fig.…”