X-ray photochemical wet etching of n-Si (100) in hydrofluoric solution

Abstract

Photochemical wet etching of n-type Si (100) was carried out in hydrofluoric acid (49wt%) solution using high-flux synchrotron x-ray radiation. Under illumination of high-flux white x-ray beam, silicon is electropolished with an etching rate of about 1.5nm∕min. When illuminated with a monochromatic x-ray beam of relatively low flux, a porous silicon layer is formed instead. The open circuit potential increases under the white x-ray beam, in contrast to the results of visible or ultraviolet photoelectrochemistry. The authors attribute the electroless electropolishing of silicon to the enhanced band bending caused by the x-ray illumination.