Surface Morphology Control of Passivated Porous Silicon Using Reactive Ion Etching

In this paper, reactive ion etching of porous silicon (PS) passivated using a low-temperature anneal in N₂ atmosphere is studied. The average etch rates of both as-fabricated PS and passivated PS required tens of seconds to stabilize due to plasma initialization. The steady-state etch rate of our passivated PS was lower than that of the as-fabricated PS, due to the change in the surface chemistry caused by the passivation process. Depending on etch conditions, the PS surface can be made smooth or rough with features up to 600 nm in height. Feature height could be controlled via the etching time, and their composition could be changed from an oxide-rich silicon oxynitride to pure silicon, depending on the etching conditions.