This letter presents an under-etching prevention method for an aqueous hydrofluoric acid (HF) releasing process by adding a single-side low-pressure chemical vapor deposition (LPCVD) silicon protection layer. The proposed method enables advanced silicon-on-insulator (SOI) based millimeter-wave/terahertz (mmW/THz) MEMS waveguide devices, which require for RF performance a complete metallization film over the SOI buried-oxide (BOX) layer, and simultaneously need a locally under-etched BOX layer for implementing MEMS actuators reconfiguring the devices. A comparison between the WR-3.4 waveguide (220-330 GHz) using the proposed under-etching prevention method and the one without using it proves the effectiveness and feasibility during HF releasing processes. A MEMS tunable phase shifter driven by comb-drive actuators has been successfully implemented by applying this method in a micromachined waveguide. [2021-0036]

中文翻译：

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先进太赫兹微机械波导器件的高频蚀刻不足预防


这封信提出了一种通过添加单面低压化学气相沉积（LPCVD）硅保护层来防止水性氢氟酸（HF）释放工艺的蚀刻不足的方法。所提出的方法可实现先进的基于绝缘体上硅 (SOI) 的毫米波/太赫兹 (mmW/THz) MEMS 波导器件，这需要在 SOI 埋氧化物 (BOX) 层上使用完整的金属化薄膜来实现射频性能，同时需要一个局部蚀刻不足的 BOX 层来实现 MEMS 执行器重新配置设备。使用所提出的防蚀刻方法的WR-3.4波导（220-330 GHz）与未使用该方法的WR-3.4波导（220-330 GHz）之间的比较证明了在高频释放过程中的有效性和可行性。通过在微机械波导中应用这种方法，成功实现了由梳状驱动执行器驱动的MEMS可调谐移相器。 [2021-0036]