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Enhanced Selectivity in GaAs/AlGaAs Selective Dry Etching in BCl3+CF4 Plasma by Adsorbed CxFy for Precise Control of HJFET Threshold Voltages
Published in Jong-Chun Woo, Yoon Soo Park, Compound Semiconductors 1995, 2020
M. Tokushima, H. Hida, T. Maeda
The total gas flow rate was 20 sccm, and the gas flow ratio of CCl2F2 and He was set at 9:1. First, GaAs etching characteristics were investigated. Figures 1(a) and 1(b) are SEM photographs of cross sections for an etched GaAs surface. Facets of (111) and (122) were observed as in Fig. 1(a), indicating that the etching process of GaAs was mainly a spontaneous radical reaction on the surface and that the self- bias of -12 V was low enough to prevent ions from significant sputtering. In Fig. 1(b), the rough etched-surface is shown. The surface roughness together with an XPS signal of Ga3d for the GaAs etched surface suggests that the GaAs etching was limited by desorption of a low-volatile gallium fluoride on the etched surface. Thus, we presume that dependence of GaAs etching rate on substrate temperature shown in Fig. 2 corresponds to that of etching product desorption rate.
Fabrication of GaAs micro-optical components using wet etching assisted femtosecond laser ablation
Published in Journal of Modern Optics, 2020
Xiaoyan Sun, Fang Zhou, Xinran Dong, Fan Zhang, Chang Liang, Lian Duan, Youwang Hu, Ji’an Duan
A schematic diagram of the femtosecond laser machining system is shown in Figure 1. The laser used in the experiment was a titanium-doped sapphire femtosecond laser (Spectra Physics, Newport corporation) with a central wavelength of 800 nm, a repetition frequency of 1 kHz, and the pulse width of 120 fs. The processing power varied from 20 to 100 mW, and the peak power density of the femtosecond laser pulse can reach 1021 W/cm2; this can be used to easily process the surface of metals and semiconductors. After passing through the optical path, the laser was introduced into the objective (20×, NA 0.4, Spectra Physics) for focusing, and the beam propagation direction was perpendicular to the surface of the target material. The target material was placed on a three-dimensional motion stage (Suruga Seiki corporation) that has an accuracy of 5 nm and a velocity in the range of 1–2 mm/s. Compared to the traditional lithography process, the femtosecond laser processing system is flexible. The laser power, laser frequency, or speed of the stage can be adjusted to quickly and efficiently obtain different processing parameters. The thickness of GaAs (T2177138, Beijing Tebovande Technology Co., Ltd.) that was used in this paper was 350 ± 20 µm, and the crystal direction was (100) without doping. The corrosion solution was mainly composed of chromium trioxide (CrO3) and hydrofluoric acid (HF), and the ratio of H2O:CrO3:HF was 20 mL:8 g:10 mL. CrO3 was dissolved in water and formed chromic acid, which has a strong oxidation property. Chromic acid decomposed and released oxygen to oxidize GaAs. The oxide film was dissolved by HF in the etching solution to generate gallium fluoride (GaF3) and arsenious acid (H3AsO3) [19]. Therefore, the equation of the total corrosion reaction of GaAs is as follows: