Growth and characterization of anodic oxides on Si(100) formed in 0.1 M hydrochloric acid

Abstract

Anodic oxides of thickness 1–10 nm have been grown on Si(100) using anodic oxidation at room temperature. The electrolyte was 0.1 M HCl. The effects of the anodic potential, growth time, external visible illumination intensity, substrate doping type, and density on the oxide thickness were determined. Coulometric and etching experiments suggest that no silicon is lost to the 0.1 M HCl solution. Under sufficient visible illumination, the oxide thickness was independent of dopant level for n-type substrates and only weakly dependent for p-type substrates. These results suggest that this technique can be used for accurate dopant profiling, when combined with cyclical etch back and four-point probe electrical measurements. In the dark, the oxide thickness was substantially reduced for n-type substrates. This suggests that this technique can be used for lateral delineation of n- and p-type regions on patterned wafers. The as grown oxides were characterized by x-ray photoelectron spectroscopy, ellipsometry, and x-ray reflectometry. The substrates were characterized by Mott–Schottky analysis which, together with electrochemical polarization curves, assisted in a qualitative description of the oxide growth as a function of doping density and type. Flatband potentials obtained from Mott–Schottky analysis were obtained at pH 1.1 and 11.7, and show a pH dependence of approximately 60 mV/pH unit, which in contrast to previously reported data indicates an ideal behavior.