Oshima Yuichi, Oshima Takayoshi
Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba, Japan.
Sci Technol Adv Mater. 2025 Sep 3;26(1):2546285. doi: 10.1080/14686996.2025.2546285. eCollection 2025.
The planar and lateral HCl-gas etching behavior of (001) β-GaO under oxygen supply were investigated at partial pressures of (O) = 0-2.5 kPa and 645-1038°C, while maintaining a constant HCl supply partial pressure of (HCl) at 63 Pa. At 747°C, the planar etch rate (PER) exhibited a slight decrease with increasing (O). Notably, at (O) = 1.25 kPa, the PER increased with temperature, demonstrating a plateau between 747 and 848°C, whereas the thermodynamically calculated etching driving force did not. Even minimal O supply effectively suppressed root mean square (RMS) roughness to <1 nm at 747°C. At (O) = 1.25 kPa, RMS roughness remained at <2 nm at up to 847°C, but sharply increased to >7 nm above 947°C, indicating that lower temperatures realize smoother surfaces. Lateral etch rate (LER) analysis, employing a spoke-wheel pattern mask at 747°C revealed significant anisotropy, demonstrating a kidney-like polar plot pattern, with minimum values in the <100 > direction and maximum values in the <010> direction. Although (O) had a limited effect on anisotropy, temperature increase significantly enhanced the LER, particularly along the ± 20°-rotated directions from <100> . Above 947°C, etched sidewalls exhibited a multi-faceted morphology owing to the formation of {310} and {3̅10} facets depending on the spoke direction, whereas the sidewalls were relatively smooth below 848°C. These findings underscore the potential of controlled HCl-gas etching for the plasma-free processing of β-GaO, enabling the fabrication of high-performance devices.
在氧气供应下，研究了（001）β-GaO在氧分压（O）=0 - 2.5 kPa和温度645 - 1038°C下的平面和侧向HCl气体蚀刻行为，同时保持HCl供应分压（HCl）恒定在63 Pa。在747°C时，平面蚀刻速率（PER）随（O）的增加略有下降。值得注意的是，在（O）=1.25 kPa时，PER随温度升高而增加，在747至848°C之间呈现出一个平稳期，而热力学计算的蚀刻驱动力并非如此。即使是极少量的氧气供应也能在747°C时有效地将均方根（RMS）粗糙度抑制至<1 nm。在（O）=1.25 kPa时，直至847°C，RMS粗糙度仍保持在<2 nm，但在947°C以上急剧增加至>7 nm，这表明较低温度可实现更光滑的表面。在747°C下使用辐条轮图案掩模进行的侧向蚀刻速率（LER）分析显示出显著的各向异性，呈现出类似肾脏的极坐标图图案，在<100>方向上具有最小值，在<010>方向上具有最大值。尽管（O）对各向异性的影响有限，但温度升高显著提高了LER，特别是在与<100>方向±20°旋转的方向上。在947°C以上，蚀刻侧壁由于根据辐条方向形成{310}和{3̅10}晶面而呈现出多面形态，而在848°C以下侧壁相对光滑。这些发现强调了受控HCl气体蚀刻在β-GaO无等离子体加工中的潜力，能够制造高性能器件。
