APPLICATION OF AN ACOUSTOOPTIC SPECTROMETER FOR PLASMA-ETCHING PROCESS QUALITY-CONTROL

The solution is proposed to the problem of the relative concentration dynamics control of chemically active particles in the low temperature gas plasma as well as the investigation of their generation and annih ilation by means of time-resolved actinometry. A special small-size ac ousto-optic spectrometer has been constructed capable of spectral reso lution of 0.1-0.3 nm in the visible range (430-850 nm) and the maximum time resolution of 2.0 mu s. The software package developed allows: ( 1) measuring of the chronograms of the relative concentrations of vari ous active particles in parallel mode at eight spectral channels; (2) generating impulse plasma modulation and measuring the microdynamics o f the generation and annihilation of the active particles in the frame -by-frame mode (1024 points) in four parallel spectral channels, inclu ding the two corresponding background values. To shorten the measureme nt time and to improve the measurement accuracy of the particle annihi lation kinetic characteristics in the interval between two stationary (long) pulses, it is proposed to form a series of probing (short) puls es. Some preliminary results are presented of the monitoring of the fl uorine radicals (703.7 nm) relative concentration in the SF6 gas r.f. plasma, containing as an actinometer a small amount (up to 5%) or argo n (750.4 nm) at different discharge powers. Using the measurement resu lts of the fluorine radicals, relative concentration in the pulse-modu lated noble gas plasma obtained at monosilicon etching, the constants of the radical accumulation, as well as their life time values, are de termined for the loaded and unloaded reaction chamber.