Paper PS-TuP14
N₂, O₂, and NF₃ Dissociation in a Low Frequency, High Density Plasma Source

Tuesday, October 31, 2017, 6:30 pm, Room Central Hall

Most capacitive and inductive plasmas used in deposition and etching tools for semiconductor processing operate at pressures in the sub-Torr regime (typically <200 mTorr) at relative low power densities (~0.01 – 0.1 W/cm³). Higher pressure, high power density plasma sources offer significant advantages in improved cost of ownership through increased tool throughputs, but have not received as much attention in the academic world. In this poster we present measurements of radical densities and gas dissociation fractions for various mixes of N₂, O₂, and NF₃ feed gases with Ar at 400 sccm total flow rate in a low frequency (400 kHz), high pressure (1-10 Torr), inductively-coupled toroidal remote plasma source from MKS Instruments operating at a power density of 5 – 50 W/cm³. The radical densities and feed gas dissociation percentages in the plasma were measured by optical emission spectroscopy (OES), combined with Ar actinometry. The dissociation of O₂ drops from 55% to 10% with increasing O₂ percentage, while the dissociation of N₂ rises from 10% to ~100% with increasing N₂ percentage. For NF₃, the dissociation to form F rises with increasing NF₃ percentage from 60% at 1% NF3 and to 100% at 10% NF₃, while about 25% of the nitrogen is present as N₂, independent of NF₃ percentage, with presumably some or nearly all of the remaining nitrogen present as N atoms, which are detected in optical emission. Enhanced or suppressed dissociation as a function of added Ar will compared with changes in discharge current, relative electron density and other plasma parameters.