Study of dry etched N-polar (Al)GaN surfaces obtained by inductively coupled plasma etching Article Swipe

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Inductively coupled plasma Etching (microfabrication) Surface roughness Polar Analytical Chemistry (journal) Dry etching Materials science Surface finish Plasma etching Layer (electronics) Plasma Chemistry Nanotechnology Metallurgy Composite material Chromatography Quantum mechanics Astronomy Physics

Xiaoming Ge , Xuebing Yin , Qiaoyu Zeng , Qi Feng , Xiaohui Wang , Quantong Li , Zhitao Chen , Chengguo Li ·

YOU? · · 2022 · Open Access · · DOI: https://doi.org/10.3389/fphy.2022.1042998 · OA: W4307556091

We report the Cl-based inductively coupled plasma etching of N-polar Al(Ga)N layers obtained from layer transfer. It is found that debris appeared on the etched N-polar surface after exposing in air for a short period whereas the etched Al-/Ga-polar surface was clean and smooth. The debris can be completely self-vanished on the N-polar Al 0.4 Ga 0.6 N surface after exposing in air for a few hours but still remained on the N-polar GaN surface even after over 1 month. The surface chemical analysis results suggested that the debris is the result of Cl-related byproduct generated during the etching process. Byproducts like Al(Ga)Cl x and its derivatives are believed to cover on the N-polar surface after the inductively coupled plasma etching and increase the etched surface roughness significantly. The formation and disappearance of debris are attributed to the formation of Al(Ga)Cl x ⋅ 6H 2 O crystals when Al(Ga)Cl x absorbs moisture in the air and its spontaneous decomposition on the N-polar surface, respectively. Adding O 2 /SF 6 in the process helps remove Al(Ga)Cl x byproducts but at the cost of roughened surface/reduced etch rate. With an additional cleaning process after etching, an uniform and smooth N-polar GaN surface with a low root-mean-square surface roughness of 0.5–0.6 nm has been successfully obtained at a reasonable etch rate (∼150 nm/min). The results can provide valuable guidance for the fabrication of high-performance N-polar GaN devices.