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The measurement and interpretation of ion bombardment energies in rf discharges of SF6, CF3Cl, and CF3Br from 0.2 to 1.0 Torr, are discussed. Errors in ion sampling due to disturbances of the electric field and neutral density around the sampling orifice are shown to be most important at higher pressures and with larger orifices. The dependence of the ion bombardment energy distribution on the electric-field-to-pressure ratio is reviewed. Combining this relation with a simple electrical model of a plasma gives estimates of the ion bombardment energies in collisional sheaths. The bombardment energy is proportional to (rf current)/(electrode area×frequency ×pressure) with the proportionality constant for a particular system depending on the collision cross sections and relative ion-to-netural mass ratio. The constants found for the three gases studied experimentally are close to theoretical estimates.

Articles you may be interested inHBr concentration and temperature measurements in a plasma etch reactor using diode laser absorption spectroscopy J.Oxygen atom actinometry reinvestigated: Comparison with absolute measurements by resonance absorption at 130 nm Atomic chlorine concentrations in C1 2 and CF 3 Cl plasmas have been measured using both infrared absorption spectroscopy and optical emission actinometry. These measurements were made over a range of plasma conditions including plasma excitation frequencies of 72 kHz-13.5 MHz, power inputs of 10-100 W, and pressures of 200-800 mTorr. In C1 2 plasmas, the technique of optical emission actinometry misrepresents atomic chlorine concentration changes by nearly an order of magnitude. The errors in the actinometry technique are believed to result from excited state Cl production by electron impact dissociation of C1 2 • A simple model for Cl emission is in good agreement with the experimental observations. In CF 3 CI discharges, the technique of optical emission actinometry is shown to accurately represent variations in atomic chlorine concentration with changing process conditions. 792

P ~s energ.y scaling parameter based on predicted mean 1on energy scaling parameter, P/Po ion-neutral scattering cross section (cm 2) time-averaged sheath electric field (V/cm) [Additional symbols listed in Ref. (1)]ABSTRACT Three kinetic models, based on experimentally measured and theoretically estimated plasma properties, are developed to describe heavily P-doped polysilicon etching in CF3C1 (Freon | 13) RF discharges. The models include both chemical and ion-assisted processes, and, therefore, predict etching directionality as well as etching rate. The results indicate the importance of relatively low energy (<30 eV) ion bombardment, and suggest that the dominant loss process for the chemical etchant is diffusion-limited recombination at the electrode surfaces. Agreement between measured and predicted etching rates is excellent. The major trends in etching directionality are reproduced by the model, although there is some quantitative disagreement at low pressure.