The Effects of a Few Formation Parameters on Porous Silicon Production in HF/HNO3 Using Ag-Assisted Etching and a Comparison with a Stain Etching Method

Abstract

AbstractIn a solution of HF with HNO3 as an oxidizing agent, silver-catalyzed etching of p-type silicon is made easier. Before immersing in the etchant solution, silver (Ag) was electroless deposited on the p-Si (100) surface. By stain etching in HF/HNO3, a porous silicon layer (PSL) was also produced on p-Si. Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM), and X-ray diffraction (XRD) were used to evaluate the properties of the produced PSL. According to the SEM, Ag+ ion at a concentration of 1 × 10−3 M is the optimal concentration for depositing on Si before chemical etching in HF/HNO3, resulting in PSL with uniformly distributed pores. The EIS data showed that coated Si dissolves faster in 22 M HF/0.5 M HNO3 than untreated Si, resulting in the formation of a homogenous PSL of regular round pores, as proven by SEM micrographs. An acceptable electrical circuit model with two-time constants was used to fit the experimental impedance values. Increased concentrations of the etchant HF or the oxidizer HNO3 aid in the dissolution of Si and the rapid development of PS. The AFM analysis revealed that when the etching time increases, the pore width and roughness of the Si surface increase. X-ray spectra diffraction was used to determine the crystallinity of the PSL after various etching times.