Critical tasks in high aspect ratio silicon dry etching for microelectromechanical systems

The process of pattern transfer of desired topological features into silicon plays a critical role for the production of microelectronic and photonic devices, and micro- and nanoelectromechanical systems. Any deviation from the desired shape of the pattern limits density, yield, and reliability of these devices. Gas reactivity, pressure, ion, electron, and reactant transport to the surface, and product transport away from the surface, have all been identified as important issues that control the microscopic uniformity in high aspect ratio etching. When etch-inhibiting chemistry by the gas chopping deep reactive ion etching (RIE) was employed, it caused enormous complications in the scaling of etching rates, with increasing aspect ratio. Using an energy-resolving quadrupole mass spectrometer assembled into the cathode, specially designed test features, and etching simulation models, we establish the link between etch process parameters such as pressure, rf power, etching gas chemistry, temperature, and the physical and chemical process parameters like energy and angular distribution of ions and neutrals, radical sticking, and surface charging. The most significant effects like RIE lag, notching, bowing, faceting, microtrenching, profile shape dependence, etc. will be discussed in this article. (C) 2003 American Vacuum Society.