Fabrication of black silicon via reactive ion etching through Cu micromask

Black silicon was fabricated on a pyramid silicon surface via reactive ion etching (RIE) through a Cu micromask formed by a sputtering and annealing process. This adopted RIE technique does not rely on oxygen gas avoiding the silicon surface damage from oxygen plasma. Scanning electron microscopy and an UV-vis-NIR spectrophotometer were used to characterise the morphology and optical reflectance of the prepared samples with porous structures on a pyramid. The results show that the homogeneity of the Cu micromask controlled by the annealing condition determines the reflectance of the textured silicon wafer. A lowest reflectance of 6.2% appears in the samples with sputtered Cu thin film annealed at a temperature of 500°C for 10 min. This work may provide a choice to fabricate black silicon with an excellent light confinement structure, which will have potential application for the improvement of efficiency of silicon solar cells.