Ion Bombardment as Dominant Factor in Plasma Cryo-Etching for High Aspect Ratio Silicon Structures

SF₆/O₂ Plasma cryo-etching is discussed to show that it is a promising technology for etching the high aspect ratio silicon structures. Through a series of etching experiments, process factors including chuck temperature, gas composition, chamber pressure and ICP coil power are variated to show their influences to the etching results. Some valuable details of the experiment data point to some key mechanisms of the cryo-etching. It is not the surface chemical reaction but the ion bombardment that dominates the cyro-etching process in most cases. Notching near to the mask is due to the discharging effects of dielectric layer, and ARDE effect here is also different from the usual etching processes but is driven by the sidewall step coverage effect to the ion sputtering.