Characterization of stain etched p-type silicon in aqueous HF solutions containing HNO 3 or KMnO 4

Abstract

Stain etching of p-type silicon in hydrofluoric acid solutions containing nitric acid or potassium permanganate as an oxidizing agent has been examined. The effects of etching time, oxidizing agent and HF concentrations on the electrochemical behavior of etched silicon surfaces have been investigated by electrochemical impedance spectroscopy (EIS). An electrical equivalent circuit was used for fitting the impedance data. The morphology and the chemical composition of the etched Si surface were studied using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques, respectively. A porous silicon layer was formed on Si etched in HF solutions containing HNO 3, while etching in HF solutions containing KMnO 4 led to the formation of a porous layer and simultaneous deposition of K 2SiF 6 inside the pores. The thickness of K 2SiF 6 layer increases with increasing the KMnO 4 concentration and decreases as the concentration of HF increases.