Electron beam generated plasmas: Characteristics and etching of silicon nitride

The Naval Research Laboratory (NRL) has developed a processing system based on an electron beam-generated plasma, where unlike conventional discharges produced by electric fields (DC, RF, microwave, etc.), ionization is driven by a high-energy (~keV) electron beam. The resulting plasmas are characterized by large electron densities (1010–1011cm−3) and low electron temperatures (0.3–1.0eV). Accordingly, a large flux of ions can be delivered to substrate surfaces with kinetic energies of only a few eV, a feature that can be attractive to processing applications that require low damage and atomic layer precision. This work describes the salient features of these plasmas produced in mixtures of argon and sulfur hexafluoride (SF6) and their use in silicon nitride etching, with particular attention paid to developing processing parameters relevant to atomic layer processing.