AN EMISSION ACTINOMETRIC METHOD FOR MEASURING OF PLASMACHEMICAL REACTION KINETIC-PARAMETERS WITH DISCHARGE POWER MODULATION BY A SERIES OF SHORT PROBING PULSES

A method of emission actinometric measurement of kinetic parameters of plasmachemical reactions is proposed including the determination of t he kinetic order, annihilation rate constants of chemically active par ticles and their characteristic lifetimes. The basis of the method is the time-resolved actinometry and the discharge power modulation by a probing pulse series at the afterglow stage with a time resolution of Delta t greater than or equal to 1 mu s. Kinetic accumulation and anni hilation curves at this stage are derived from the microdynamics of sp ectral line intensitities of the selected actinometric pairs, The meas urements of spectral line peaks and their background values controlled by the PC microcomputer are carried out at four to nine wavelengths i n a quasi parallel mode of an acoustooptic spectrometer. The duration of a measurement cycle of 100 repeated measurements al four wavelength s with a time resolution of 25 mu s took no more than 50 s. The values of kinetic parameters can be derived from the analysis of the logarit hmic plot of the kinetic curve of particle annihilation. Measurements of the heterogeneous annihilation rate constant for atomic fluorine ha ve been carried out in the SF, RF plasma with an addition of argon as an actinometer in a standard diode-type Al-reactor. The values of puls e length and duty cycle of probing pulses are determined experimentall y for measuring the kinetic parameter of fluorine annihilation in such a way that there is no substantial increase of the fluorine residual concentration level. Based on the analysis of the experimental kinetic curve of heterogeneous annihilation, a solution taking into account a procedural error of the proposed method due to nonzero level of the r esidual concentration of the observed particles at the afterglow stage is proposed, The experimentally obtained value of the fluorine hetero geneous annihilation rate constant measurement error is about (15 +/- 2)% at a residual concentration level of about 10%. The measurement re producibility of fluorine heterogeneous annihilation rate constant is 3-5% in the unloaded and silicon wafer loaded reaction chamber with ac tinometer concentrations of 2.5 and 5.6%. (C) 1998 Elsevier Science S. A.