Reactive Ion Etching: Anisotropic Pattern Transfer

Nanofabrication's top-down half comes down to one repeated act: pattern a mask, then remove everything the mask doesn't cover, one exposed atomic layer at a time. This simulator models that removal as a real cellular automaton on a masked silicon cross-section — each surface cell etches with a probability built from two independently tunable mechanisms, directional physical sputtering and isotropic chemical attack, exactly as in real reactive-ion etching (RIE) plasma tools. Drag the ion-anisotropy slider from a pure chemical wet-etch profile to a pure physical ion-mill profile and watch the sidewalls straighten and the undercut vanish; drop the mask selectivity and watch the mask itself erode and widen the printed feature. Live readouts track etch depth, undercut, and aspect ratio — the three numbers that actually decide whether a real nanofabrication process can hit its target feature size.