Dry Etching Of GaN Research Articles

Normally off AlGaN/GaN HEMT on Si substrate with selectively dry-etched recessed gate and polarization-charge-compensation δ-doped GaN cap layer

We demonstrate a recessed-gate normally off AlGaN/GaN high-electron-mobility transistor (HEMT) on a silicon substrate that provides a precisely controllable threshold voltage (Vth). To ensure Vth uniformity, dry-etching of GaN with high etching selectivity between GaN and AlGaN is developed. Furthermore, to introduce selective dry-etching in the HEMT fabrication process, we propose a delta-doped GaN cap structure that enables negative polarization charges between the GaN cap and the AlGaN barrier to be compensated. Combining these two technologies, we fabricate recessed-gate normally off metal–insulator–semiconductor HEMTs with a subthreshold slope of 130 mV/dec and an on–off drain current ratio exceeding 107.

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

The vertical structuring of GaN layers for power application purposes is a key step for successful device operation. Thus, the dry etching of GaN becomes a crucial step. While etch rates and surface roughness have been analyzed well, the sidewall angle of the etched GaN has drawn less attention. In this paper, the authors report on the influence of mask material and etch parameters in an inductively coupled plasma reactive ion etching process on the angle of the etched GaN sidewall. Deep etches up to 3.3 μm are shown. The authors show how the sidewall angle can either be adjusted to high values up to 80° or, if necessary, to small angles down to 46°.

Dry etching of GaN and related materials: comparison of techniques

The etch rates and feature anisotropy for GaN, AlN, and InN etched in Cl/sub 2/-Ar plasmas with four different techniques were examined. Conventional reactive ion etching produces the slowest etch rates, even when high dc self-biases (>-900 V) are employed, and this leads to mask erosion and sloped feature sidewalls during ridge waveguide fabrication. Two high-ion-density techniques, inductively coupled plasma and electron cyclotron resonance, provide the highest etch rates and most anisotropic features through their combination of high-ion flux and moderate-ion energy. Etch selectivities of GaN to AlN and InN are typically /spl les/4 in these tools. Reactive ion beam etching utilizing a high density (ICP) source is also an attractive option for pattern transfer in the nitrides, although its etch rates are slower than for ICP or ECR due to its lower operating pressure.

Dry Etching of GaN Using Reactive Ion Beam Etching and Chemically Assisted Reactive Ion Beam Etching

ABSTRACTDry etching characteristics of GaN using reactive ion beam etching (RIBE) were studied. Etching profile, etching rate and etching selectivity to a photoresist (PR) mask were investigated as a function of various etching parameters. Characteristics of chemically assisted reactive ion beam etching (CARIBE) and RIBE were compared at varied mixtures of CH4 and Cl2. A highly anisotropie etching profile with a smooth surface was obtained for tilted RIBE with Ch at room temperature. Etching selectivity to a PR was dramatically improved in RIBE and CARIBE when a volume fraction of CH4 to the mixture of CH4 and Ch was larger than 0.83.

Dry etching of GaN using chemically assisted Ion beam etching with HCI and H2/Cl2

The dry etching characteristics of GaN were investigated using chemically assisted ion beam etching (CAIBE) with HCI and H2/Cl2 gas. Etch rates using CAIBE/HC1 were investigated as a function of Ar ion beam energy and substrate temperature. These results were compared to CAIBE/C12. Etch rates were also investigated for CAIBE/H2/Cl2 for various ratios of H2:C12. Highly anisotropic submicron lines are demonstrated using CAIBE/HC1. Auger electron spectroscopy was used to investigate surface stoichiometric changes of samples etched with CAIBE/HC1, CAIBE/H2/Cl2,, and CAIBE/C12. The diffusion of deuterium into GaN during etching was also investigated using secondary ion mass spectrometry.

Photothermally Assisted Dry Etching Of GaN

AbstractPhotoassisted dry etching of GaN in HC1 by 193 nm ArF excimer laser is developed as apotential alternative process to eliminate the ion damage and surface roughness which occur inetching techniques that involve an energetic ion beam impinging the surface. A directed stream ofHC1 etchant with background pressure of ∼ 5 × 10−4 Torr, sample surface temperature between 200 to 400°C, and laser fluence of 10 to 20 mJ/ pulse combine to produce etching. The photoassistedetching reaction under these process conditions is thermal in nature, with activation energy near 1.2kcal/ mol. Increases in laser fluence results in increase of etch rate, but the surface also becomesrougher. Distinct etch features can be produced with smooth surfaces at expense of etch rate.

Comparison of dry etch techniques for GaN

Dry etching of GaN in Cl2/H2/CH4/Ar has been compared using electron cyclotron resonance (ECR), inductively coupled plasma (ICP), and reactive ion etch (RIE) systems. GaN etch rates and surface morphology were obtained as a function of RF power, and showed significant improvements under high density plasma conditions.