Electrochemical aspects of etching and passivation of silicon in alkaline solutions

Electrochemical polarization experiments were performed on Si wafers in ammoniacal solutions maintained at a pH in the range of 9.5 to 11.5. Anodic polarization of silicon yielded curves which are typical for materials that undergo passivation. The values of open circuit potential and passivation potential for p-type Si wafers were more anodic than for the n-type Si wafers. Corrosion current density of p-type Si wafers of low resistivity was lower than that of wafers of high resistivity. Corrosion current densities correlated well with surface roughness induced in alkaline solutions. Addition of surfactant or H₂O₂ to alkaline solutions reduced critical current density for passivation and corrosion current density.