New etching phenomena occurring at catalytic metal/Si interface in gas phase

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We discovered new gas-phase etching processes of Si using metallic catalyst and proposed the mechanisms based on the experimental results. In each experiment, etching was carried out with a Si substrate, on which a metal film was loaded, in air containing hydrofluoric acid gas at 100 C. When a Au layer was used as the catalyst, Si atoms, which passed through the Au layer, were oxidatively etched on the Au surface. When a Pd layer was used as the catalyst, etching proceeded via a Pd-Si alloy. Since the alloy was produced isotropically, the pore formed in Si was much larger than the size of the Pd layer, especially when the size was small. In addition, we found that arc-shaped pores can be formed by combining two different metal catalysts.