Infrared diode laser and laser-induced fluorescence diagnostics of an electron cyclotron resonance plasma etching tool

摘要

Abstract: Two separate laser spectroscopic approaches have been used to investigate plasmas in the downstream region of a diverging field ECR etcher driven by a standard 1 kW ASTeX 2450 MHz source. Infrared absorption spectroscopy with a diode laser source and a multipass optical system has been used to monitor concentrations of CF$-2$/, CF$-3$/, and CF$-4$/ in pure CF$-4$/ or CHF$-3$/ or in mixtures of these with other or with O$-2$/. These species concentrations, which in the cases of CF$-2$/ and CF$-4$/ are absolute, have been obtained as functions of both pressure and power. In the same tool details of the ion dynamics were studied using laser induced fluorescence (LIF) with a pulsed, etalon narrowed dye laser source, pumped by a nitrogen laser. Doppler limited line profiles of several rotational transitions of the (0 - 0) band of the B $+2$/$Sigma$-u$/$+$PLU$/ $MIN X $+2$/$Sigma$- g$/$+$PLU$/ system of N$-2$/$+$PLU$/ were used to extract axial and transverse ion velocity distributions. Both pure nitrogen and nitrogen-helium mixtures were studied, and the transverse distributions were also obtained as a function of radial position. In the pressure region studies (0.5 - 4 mTorr) ion energies are generally much smaller than had been anticipated, a result we attribute to the major role played by collisions. We have also measured the translational temperature of neutral helium (by LIF) and the rotational temperature of N$-2$/$+$PLU$/ (by LIF and optical emission) for comparison purposes.!9