Roughness kinetic and multiaffinity of anisotropic etched silicon

The effect of etching time (20-200 min) on surface roughness, statistical and fractal properties of silicon wafers during anisotropic chemical etching by KOH is investigated experimentally and theoretically. The evolution of surface morphology of silicon wafers during an anisotropic chemical etching is investigated by using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and statistical methods. FESEM investigation shows the formation of pyramid like silicon micro structures that disappear in large time scales. The surface roughness increases and decreases periodically in time with a decreasing exponentially trend. The statistical analysis were performed by calculating the roughness and correlation length, distribution of height fluctuations and two-dimensional multifractal detrending moving average (MFDMA). The fractal nature of silicon wafer changes from mono fractal to multi fractal scaling by etching process and formation of pyramid like silicon nanostructures on it. The strength of multi-fractallity has not an increasing monotonic behavior. The enhancement of irregularities could be a reason for reduction of surface roughness and structure downfall.