Fast speed nano-sized macropore formation on highly-doped n-type silicon via strong oxidizers

The growth of nano-sized macropores at high speed is studied in this work. Nice macropores with diameters of 60–100 nm and aspect ratio up to 2500 were formed by anodic etching on highly-doped n-type silicon without illumination. The HF-containing electrolytes were modulated with strong oxidizer, H2O2, which was also attempted by a few other researchers, but did not lead to the expected macropore formation. Our findings reveal that the pore morphology and etching speed are on dependence of HF concentration and the applied current density. The parameter window of macropore formation, corresponding to the HF concentration ranging from 33% to 67% (by volume) in our experiment, is rather large. In addition, the growth speed can be driven up to 1800 μm/h, while the pores are straight, cylindrical and rather smooth. The current-burst-model is applied to interpret the mechanism of such nano-sized macropore formation.