Collision Cross Sections for Electron-Impact Dominated Processes in Etching Plasmas

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Plasma based processes such as plasma etching and plasma enhanced chemical vapor deposition are used in the fabrication of microelectronic devices. Models of the system, used for design and control purposes, require a microscopic data base of the ground and excited-state densities of the various species in a "cold" plasma. Physical parameters such as the gas mixture, gas pressure, power deposition, flow rate and reactor geometry are needed to determine the characteristics of the plasma. Electronic collisions are the dominant processes in the initial breakdown of the plasma. Dissociative and/or ionizing electron collisions play a pivotal role, since they produce the species that are responsible for the etching and deposition. Building a comprehensive data base, including experimentally derived data on electron collision cross sections, will help in the modelling and design of plasma processes. The P.I.'s plan to study dissociative and ionizing electron collisions with the reactive constituents of processing plasmas, and the stable radicals resulting from their break- up, along three lines: (1) Laser-induced fluorescence (LIF) studies of the formation of neutral ground-state fragments using an electron beam / gas beam / laser beam apparatus set up to determine the absolute cross sections and appearance potentials for the formation of neutral ground-state dissociation fragments. (2) Studies of ionization and dissociative ionization processes- absolute ionization cross sections, appearance potentials, mass spectral cracking patterns - using a crossed fast atomic beam / electron beam apparatus. (3) Time of flight studies of energetic metastable formation of dissociation fragments using the above apparatus.