Electrochemical aspects of anodically etched Si in strong hydrofluoric acid solutions

Summary form only given. The authors have investigated the electrochemistry of Si in strong hydrofluoric acid (HF) solutions using potentiodynamic and alternating-current techniques. Their aim was to elucidate the anodizing process in the oxidation of porous Si (FIPOS) SOI technology. A number of p-type (0.005 to 60 Ω-cm) and n-type (0.005 to 0.1 Ω-cm) resistivities have been studied, most of which anodize readily. Potentiodynamic experiments on such material show an anodic branch with three different regions. Frequency dispersion impedance measurements indicate that nondegenerate p-type material biased in the anodic direction has a large surface-state capacitance. The charge-transfer resistance (R_ct) decreases with increasing anodic bias. Highly doped p- and n-type material (>0.15 Ω-cm) has a maximum R_ct at the rest potential. Complicated inductive and negative resistance features are seen in the anodizing regime