Macropore Formation on p-Type Si in Fluoride Containing Organic Electrolytes

Abstract

Electrochemical oxidation of p‐silicon of different crystal orientation and doping density has been investigated in fluoride containing nonaqueous solution of acetonitrile and dimethylformamide. The formation of a macroporous layer with macropore diameter and length in the micron range in acetonitrile is observed only if the resistivity of the silicon exceeds for both (100) and (111) crystal orientations, whereas in dimethylformamide the macroporous layer can be formed on substrates. The influence of water concentration in the electrolyte on the morphology of the macropores has also been studied. The resistivity of the used electrolyte solutions was measured and compared to that of silicon. Formation of a macroporous layer is explained by the effective collection of holes at the tip of the growing macropores. ©1998 The Electrochemical Society