THE PHYSICS OF MACROPOROUS SILICON FORMATION

Self-organizing properties are observed for pore formation on silicon electrodes during anodization in hydrofluoric acid. In contrast with a quantum size mechanism which dominates in the microporous regime, a steady state condition at the pore tip is found to be the determining factor for macropore formation. This steady state condition is characterized by a critical current density for which the reaction changes from the charge-limited transfer to the mass-transfer-limited regime. Pore arrays of a depth up to the wafer thickness and aspect ratios of 250 were etched using the equations presented in this work.