THE BLACK SILICON METHOD .2. THE EFFECT OF MASK MATERIAL AND LOADING ON THE REACTIVE ION ETCHING OF DEEP SILICON TRENCHES

Very deep trenches in Si with smooth controllable profiles are etched using a fluorine-based Reactive Ion Etcher (RIE). The effect of variou s mask materials and loading on the profile is examined using the Blac k Silicon Method. It is found that most metal layers have an almost in finite selectivity. When the aspect ratio of the trenches is beyond fi ve, RIE lag is found to be an important effect. Evidence is found that this effect is caused by the bowing of incoming ions by the electrica l field.