Black Silicon - Production By Reactive-ion Etching

Production By Reactive-ion Etching

In semiconductor technology, reactive-ion etching (RIE) is a standard procedure for producing trenches and holes with a depth of up to several hundred micrometres and very high aspect ratios. In Bosch process RIE, this is achieved by repeatedly switching between an etching and passivation. With cryogenic RIE, the low temperature and oxygen gas achieve this sidewall passivation by forming SiO₂, easily removed from the bottom by directional ions. Both RIE methods can produce black silicon, but the morphology of the resulting structure differs substantially. The switching between etching and passivation of the Bosch process creates undulated sidewalls, which are visible also on the black silicon formed this way.

During etching, however, small debris remain on the substrate; they mask the ion beam and produce structures that are not removed and in the following etching steps and result in tall silicon pillars. The process can be set so that a million needles are formed on an area of one square millimeter.