Gas reactivity, pressure, ion, electron, and reactant transport to the surface, and product transport away from the surface, have been identified as important issues that control the microscopic uniformity in high aspect ratio etching. Any deviation from the desired shape of the pattern limits density, yield, and reliability of these devices. The process of pattern transfer of desired topological integrated circuits features into silicon or other semiconductor compounds plays a critical role for the production of microelectronic and photonic devices, and micro- and nanoelectromechanical systems.