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Formation of Cylindrical Nanoholes in Heavily Doped P-Type Si(100) Substrate via Pt Nanoparticles-Assisted Chemical Etching

Metal assisted chemical etching of heavily doped p-type Si(100) wafer was investigated in a solution containing HF and hydrogen peroxide using Pt nanoparticles as catalyst. The Pt nanoparticles were formed on Si(100) substrate by magnetron sputtering and post-deposition annealing. In a solution containing low concentration HF, formation of cylindrical nanoholes are unstable in the early stage of the etching process. After that, nanoholes with diameters ranging from 40 to 50 nm are stably formed in silicon substrate and the calculated growing rate is 60 nm/min. Instead, in a solution containing high concentration HF, cylindrical nanoholes with a diameter of about 10 nm can be stably produced in silicon substrate all the time and the growing rate is increased to as fast as 160 nm/min. In both cases, no Pt nanoparticles are observed at the bottom of the nanoholes. Finally, the underlying mechanisms of the aforementioned phenomena are also discussed.