Surface Structure Chemical Transfer Method for Formation of Ultralow Reflectivity Si Surfaces

Abstract

We have developed a surface structure transfer method by use of the catalytic activity of platinum (Pt). When a Pt mesh contacts Si wafers immersed in a HF plus H2O2 solution, Si oxidation and its dissolution instantaneously proceed, resulting in formation of the inverted structure of the Pt mesh on Si. The etching depth is proportional to the immersion time, indicating the reaction-limited mechanism. The reaction rate constant is proportional to the concentration of H2O2, showing that oxidation is the rate-determining step. Nanocrystalline Si is formed on the whole Si surfaces including non-contacted regions with the Pt mesh. The nanocrystalline Si formation is attributable to an electrochemical reaction which includes accumulation of holes in Pt by decomposition of H2O2, injection of holes to Si, hole diffusion, and Si dissolution by use of trapped holes. The nanocrystalline Si layer greatly decreases the reflectivity of crystalline Si surfaces less than 10% in the wide wavelength region (300∼800 nm).