Fast pore etching on high resistivity n-type silicon via photoelectrochemistry

In this paper, five factors, namely the HF (hydrofluoric acid)concentration, field strength, illumination intensity as well as theoxidizing-power and conductivity of electrolytes were found tostrongly affect the fast pore etching. The oxidizing power ofaqueous HF electrolyte of different concentrations was especiallymeasured and analysed. A positive correlation between optimal biasand HF concentration was generally observed and the relationship wassemi-quantitatively interpreted. Pore density notably increased withenhanced HF-concentration or bias even on patterned substrates where2D (two-dimensional) nuclei were densely pre-textured. The etch ratecan reach 400μm/h and the aspect ratio of pores can bereadily driven up to 250.