Optical diagnostics of SF6 low pressure plasma jet applied to silicon etching

Abstract

In this work the applicability of a low pressure sulphur hexafluoride (SF6) plasma jet for silicon etching was investigated by optical emission spectroscopy (OES) technique. Through the use of actinometry method the density of atomic fluorine was obtained as a function of process parameters namely radio-frequency (rf) power, axial magnetic field, SF6 gas pressure and flow rate, and O2 concentration in the SF 6+O2 mixture. The results indicate large fluorine concentrations (>10% in overall plasma volume) for the conditions studied. To confirm the applicability of these results for microelectronic material processing, we performed the etching of masked silicon (Si) substrates under some optimum process conditions. Etch rates of up to 1.2 μm/min were obtained for rf power of about 150W and operating pressures about 3.1 mTorr. These values of etching rates are comparable with those obtained in inductively coupled plasma (ICP) systems operating at similar process conditions. © The Electrochemical Society.