Modeling of complex surface interactions in low and high pressure plasmas by

Plasma etching (or dry etching) is widely used in the fabrication of integrated circuits (IC). Anisotropic features are easily obtained by controlling reactive ion trajectories in plasma. Twisting and bowing are two main issues during high aspect ratio (HAR) feature etching. Twisting is, instead of a feature etching vertically, the feature twists or turns to the side. Mixing damage by ion bombardment of underlying materials is also a critical problem in post-etch processing. One of the explanations for twisting is charge accumulation on feature surfaces during ion bombardment. An asymmetric local electric field (E-field) changes ion trajectories incident into the feature to one direction opposite the Efield. This causes twisting. Bowing at the top of the feature near the mask-SiO2 interface mainly results from bombardment of ions reflecting from eroded mask surface. Ions with energies of many keV are required for HAR etching to get a high etch rate and a straight profile. While, if the ion energy is too high, it will penetrate into the under layer material and produce mixing damage during over etch. Our research goals are to propose mechanisms to help eliminate twisting by applying high energy electron (HEE) beams, to reduce bowing by protecting the patterntransferring material photoresist (PR), and to minimize post-etching damage by optimizing operating conditions in HAR etching. A dc augmented capacitively coupled plasma (CCP) reactor is simulated using the Hybrid Plasma Equipment Model (HPEM) to generate energetic ions as well as HEE beams in Ar/C4F8/O2 gas mixture. Energy and angle distributions and fluxes for reactive species obtained from the HPEM are then input into the Monte Carlo Feature Profile