Aqueous HF-HBrO 4 Solutions for Wet-Chemical Etching of (100) Silicon Wafer Surfaces

Abstract

Aqueous solutions of hydrofluoric acid (HF) and perbromic acid (HBrO4) are investigated as nitrogen oxide (NOx)-free mixtures for wet-chemical etching of (100) silicon wafer surfaces. Such mixtures are polishing silicon surfaces with high etch rates of up to 2 µm min -1 at room temperature. Silicon surfaces are investigated by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The reduction of HBrO4 leads to multiple Br-species in equilibria, thus altering the etching behavior and leading to different surface morphologies. HBrO4 oxidizes silicon surfaces by insertion of oxygen into Si-Si-bonds. An improved synthesis for HBrO4, which uses less fluorine (F2) is also reported.