Abstract
HF wet and vapor etching of dielectric oxide films, which were prepared by thermal atomic layer deposition (ALD) and plasma-enhanced ALD (PEALD), are examined for radiofrequency microelectromechanical system (RF MEMS) application. The chemical stability of oxide films was increased in the order of ALD–Al 2O 3 < PEALD–ZrO 2 < PEALD–TiO 2 ≈ ALD–Ta 2O 5 under wet etching in 6:1 buffered HF aqueous solution, but in a different order of Ta 2O 5 < ZrO 2 < TiO 2 ≈ Al 2O 3 under anhydrous HF/CH 3OH vapor etching at 4 kPa. The unstable films were uniformly and completely etched under the wet etching, while transformed to have increased thickness or non-uniformly etched with thicker residue under the vapor etching. Al 2O 3 and TiO 2 (Ta 2O 5 and TiO 2) can be used for RF MEMS capacitive switch fabricated by using HF vapor (wet) etching of sacrificial SiO 2.
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