Influence of mask material and process parameters on etch angle in a chlorine-based GaN dry etch

In this study, we have performed a thorough characterization of the GaN surface after etching up to 100 nm in Cl2 plasma under various bias voltages and according to the carrier wafer used (Si, SiO2, Si3N4, and photoresist). The objective of this article is to evaluate the etch damage and contamination of the GaN surface when materials with other chemical nature are present during etching. The effects of etching conditions on surface morphology and chemical compositions of etched GaN films are studied in detail using XPS and AFM measurements. To this aim, a universal methodology is proposed to estimate accurately by XPS the stoichiometry of the GaN surface exposed to reactive plasmas when only an Al Kα x-ray source is available. The results indicate that the GaN etching mechanisms are very sensitive to the chlorine radical density present in the plasma, the latter being strongly influenced by the carrier wafer. Substrates that are more chemically reactive with Cl2 plasma such as silicon or photoresist compared to SiO2 or Si3N4 will lead to a greater loading of atomic chlorine, which in turn will lead to lower GaN etch rates. Moreover, the GaN surface contamination will depend on the etch by-products ejected by the carrier wafer. The GaN surface exposed to Cl2 plasma shows a Ga-depleted surface because of the more important reactivity of Cl with Ga rather than N, except in the SiO2 carrier wafer case. In this latter case, the formation of Ga–O bond limits the Ga removal. Regarding the surface roughness, it seems that the contaminants play a little role in the roughness formation except for the oxygen released by the SiO2 carrier wafer. On the other hand, the surface roughness evolution is clearly driven by the chlorine radical flux reaching the GaN surface. At low bias voltage, a preferential crystalline orientation etching driven by the Cl radicals leads to the formation of hexagonal shaped defects that are associated to screw-type threading dislocations already present in the pristine GaN material. At higher bias, the enlargement of the defects is limited, leading to a very low surface roughness value but to amorphized surfaces.

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“…In literature, it has been observed a higher selectivity for GaN:SiO 2 (mask) than for GaN:photoresist (mask) [46][47][48] . respectively 49 .…”

Section: A Gan and Carrier Wafers Etch Rate In CL 2 Plasmamentioning

confidence: 99%

Influence of the carrier wafer during GaN etching in Cl2 plasma

Meyer

Petit-Etienne

Pargon

2022

Journal of Vacuum Science &Amp; Technology A

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“…Most efforts on the reduction of surface damage and roughness of mesas [7] have been made using inductively coupled plasma (ICP) power, radio frequency 2 of 13 (RF) power, the ratio of etching gas, flow rate [8][9][10][11], and mask selection [12]. Moreover, the steepness of the mesa sidewall has also been investigated using ICP dry etching [13]. However, few works have been reported to eliminate microtrench issues for GaN mesa etching [14].…”

Section: Introductionmentioning

confidence: 99%

Optimization of Mesa Etch for a Quasi-Vertical GaN Schottky Barrier Diode (SBD) by Inductively Coupled Plasma (ICP) and Device Characteristics

et al. 2020

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The optimization of mesa etch for a quasi-vertical gallium nitride (GaN) Schottky barrier diode (SBD) by inductively coupled plasma (ICP) etching was comprehensively investigated in this work, including selection of the etching mask, ICP power, radio frequency (RF) power, ratio of mixed gas, flow rate, and chamber pressure, etc. In particular, the microtrench at the bottom corner of the mesa sidewall was eliminated by a combination of ICP dry etching and tetramethylammonium hydroxide (TMAH) wet treatment. Finally, a highly anisotropic profile of the mesa sidewall was realized by using the optimized etch recipe, and a quasi-vertical GaN SBD was demonstrated, achieving a low reverse current density of 10−8 A/cm2 at −10 V.

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“…ICP-RIE processes have been developed for compounds such as GaAs, AlGaAs, InGaAs, InP and GaN [13][14][15][16][17][18]. In contrast, GaP is a largely unexplored material for integrated nanophotonic and opto-electronic applications despite its attractive combination of large refractive index and large electronic bandgap, and fabrication processes for this material are in general far less advanced.…”

Section: Introductionmentioning

confidence: 99%

Highly selective dry etching of GaP in the presence of Al_xGa_1–xP with a SiCl₄/SF₆plasma

Hönl¹,

Hahn²,

Baumgartner³

et al. 2018

J. Phys. D: Appl. Phys.

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We present an inductively coupled-plasma reactive-ion etching process that simultaneously provides both a high etch rate and unprecedented selectivity for gallium phosphide (GaP) in the presence of aluminum gallium phosphide (Al x Ga1−xP). Utilizing mixtures of silicon tetrachloride (SiCl 4 ) and sulfur hexafluoride (SF 6 ), selectivities exceeding 2700:1 are achieved at GaP etch rates above 3000 nm min −1 . A design of experiments has been employed to investigate the influence of the inductively coupled-plasma power, the chamber pressure, the DC bias and the ratio of SiCl 4 to SF 6 . The process enables the use of thin Al x Ga1−xP stop layers even at aluminum contents of a few percent.

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Influence of mask material and process parameters on etch angle in a chlorine-based GaN dry etch

Abstract: Articles you may be interested inFormation of large-area GaN nanostructures with controlled geometry and morphology using top-down fabrication scheme

Cited by 14 publications

References 13 publications

Influence of the carrier wafer during GaN etching in Cl2 plasma

Influence of the carrier wafer during GaN etching in Cl2 plasma

Optimization of Mesa Etch for a Quasi-Vertical GaN Schottky Barrier Diode (SBD) by Inductively Coupled Plasma (ICP) and Device Characteristics

Highly selective dry etching of GaP in the presence of Al_xGa_1–xP with a SiCl₄/SF₆plasma

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Influence of mask material and process parameters on etch angle in a chlorine-based GaN dry etch

Abstract: Articles you may be interested inFormation of large-area GaN nanostructures with controlled geometry and morphology using top-down fabrication scheme

Cited by 14 publications

References 13 publications

Influence of the carrier wafer during GaN etching in Cl2 plasma

Influence of the carrier wafer during GaN etching in Cl2 plasma

Optimization of Mesa Etch for a Quasi-Vertical GaN Schottky Barrier Diode (SBD) by Inductively Coupled Plasma (ICP) and Device Characteristics

Highly selective dry etching of GaP in the presence of AlxGa1–xP with a SiCl4/SF6plasma

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Highly selective dry etching of GaP in the presence of Al_xGa_1–xP with a SiCl₄/SF₆plasma