Global model of plasma chemistry in a low-pressure O2/F2discharge

Global model (volume averaged) calculations are used to study the plasma chemistry in an O 2 /F 2 low-pressure high-density discharge. The plasma parameters, electron temperature T e , dc plasma potential V pl , electronegativity n - / n e as well as the densities of the species, were calculated as a function of F 2 content and discharge pressure in the pressure range 1-100 mTorr. The fluorine discharge is highly dissociated. The density of the fluorine atom increases as F 2 is added to the discharge and for mixtures with ~35% F 2 atomic fluorine is the dominating specie in the discharge. At a fixed ratio of O 2 to F 2 , <50% F 2 in the flow rate, the electron temperature decreases with increased pressure and the dominant positive ion species changes from being O + at low pressure (<5 mTorr) to O + 2 at high pressure (>50 mTorr). At a fixed ratio of O 2 to F 2 , >50% F 2 in the flow rate, the electron temperature decreases with increased pressure at low pressure (<5 mTorr), increases with further increase in pressure up to roughly 40 mTorr and decreases again with further increase in pressure. The dominant positive ions change from being O + and F + at low pressure (<5 mTorr) to O + 2 and F + 2 at high pressure (>50 mTorr).