Selective etching of GaAs is critical for many applications, including flat optical components and high electron mobility transistors. It is long-known that F-containing process gases produce a nonvolatile AlF${}_x$ layer on AlGaAs. In this work, we present a selective GaAs etch using an inductively coupled plasma with an HBr/SF${}_6$/He etch chemistry. The optimized process exhibits $>1\mu$m/min etch rates, $>200$:1 GaAs:AlGaAs selectivity, $>50$:1 GaAs:photoresist selectivity, sub-nm surface roughness, and minimal undercut. The effect of aspect ratio is investigated, revealing limitations for deposition of an Si-rich passivation layer. Moreover, selectivity dramatically increases with an AlGaAs etch stop with high (90%) Al content. By characterizing an HBr-based selective GaAs etch, this work provides a possible alternative to the better established chlorine-based selective processes.

中文翻译：

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使用 HBr/SF6/He 的高选择性 GaAs/AlGaAs 干法蚀刻

GaAs 的选择性蚀刻对于许多应用至关重要，包括平面光学元件和高电子迁移率晶体管。众所周知，含 F 的工艺气体会产生非挥发性的 AlF${}_X$AlGaAs 上的层。在这项工作中，我们提出了使用具有 HBr/SF 的电感耦合等离子体的选择性 GaAs 蚀刻${}_6$/他蚀刻化学。优化的工艺展示$>1\mu$米/分钟蚀刻速率， $>200$:1 GaAs:AlGaAs 选择性， $>50$:1 GaAs：光刻胶选择性、亚纳米表面粗糙度和最小底切。研究了纵横比的影响，揭示了沉积富硅钝化层的局限性。此外，选择性随着具有高 (90%) 铝含量的 AlGaAs 蚀刻停止而显着增加。通过表征基于 HBr 的选择性 GaAs 蚀刻，这项工作为更好地建立的基于氯的选择性工艺提供了可能的替代方案。