Ultradeep electron cyclotron resonance plasma etching of GaN

Abstract

Ultradeep (≥5 μm) electron cyclotron resonance plasma etching of GaN micropillars was investigated. Parametric studies on the influence of the applied radio-frequency power, chlorine content in a Cl2/Ar etch plasma, and operating pressure on the etch depth, GaN-to-SiO2 selectivity, and surface morphology were performed. Etch depths of >10 μm were achieved over a wide range of parameters. Etch rates and sidewall roughness were found to be most sensitive to variations in RF power and % Cl2 in the etch plasma. Selectivities of >20:1 GaN:SiO2 were achieved under several chemically driven etch conditions where a maximum selectivity of ∼39:1 was obtained using a 100% Cl2 plasma. The etch profile and (0001) surface morphology were significantly influenced by operating pressure and the chlorine content in the plasma. Optimized etch conditions yielded >10 μm tall micropillars with nanometer-scale sidewall roughness, high GaN:SiO2 selectivity, and nearly vertical etch profiles. These results provide a promising route for the fabrication of ultradeep GaN microstructures for use in electronic and optoelectronic device applications. In addition, dry etch induced preferential crystallographic etching in GaN microstructures is also demonstrated, which may be of great interest for applications requiring access to non- or semipolar GaN surfaces.

Fabrication and field emission properties of vertical, tapered GaN nanowires etched via phosphoric acid

“…Figures 1(a) and (b) show the nanowires after the remaining metal mask was stripped but prior to H 3 PO 4 . This slight faceting at the base of the nanowires from ICP-RIE etching of GaN in Cl 2 chemistry is well documented in the literature [54][55][56], and these facets here are oriented in the á ñ l 112 a-type direction. There is also an apparent trench at the base of the dry-etched nanowires which is thought to appear due to the Ti/Ni mask erosion at extended high-bias plasma etching [32,57,58].…”

Low specific on-resistance GaN-based vertical heterostructure field effect transistors with nonuniform doping superjunctions

“…Nowadays, thick in situ doping GaN layer growth technologies, [22,23] GaN-based selective area growth technologies (SAG), [14,24] and GaN etching technologies have become more and more mature. [25,26] The reported highest GaN pillar height by SAG and the deepest etching trench by plasma etching technology have been more than 10 µm, [27,28] which could pave the way for fabricating the non-SJ HFET. Therefore, the proposed non-SJ HFET may be realized by SAG technology, during which the n-pillar and p-pillar will be grown alternately.…”

Ultrahigh GaN:SiO2etch selectivity byin situsurface modification of SiO2in a Cl2-Ar plasma

“…Previous experiments on deep etching GaN in an electron cyclotron resonance (ECR) plasma etcher resulted in anomalously high GaN:SiO 2 etch selectivities of 39 [23]. After etching in that system, the etched features were visibly coated with a residue as seen in the SEM image in Figure 1(b) which were revealed to be an Al-containing material by Auger electron spectroscopy (Figure 1(a)).…”

“…Unfortunately, GaN:SiO 2 selectivities reported in the literature are low at ∼ 6 [15][16][17], which are not ideal for deep etching. Previously, we reported exceptionally high GaN:SiO 2 etch selectivities (39:1) using a Cl 2 -Ar plasma in an Electron Cyclotron Resonance (ECR) plasma etcher [23]. The goal of this work is to determine the cause of this unusually high selectivity.…”