Hydrogen microwave plasma etching of silicon dioxide at high temperatures with in situ low-coherence interferometry control

We used a low-coherence interferometry (LCI) to measure in situ the etch rate of silica surfaces in H-2 microwave plasma at high temperatures of 970-1480 degrees C. The method allows collection of kinetic data on a single sample without switching-off the plasma, moreover, the LCI provides simultaneous measurements of the sample thickness and temperature evolution. The etching rates up to similar to 80 nm/min are measured, and activation energy for SiO2 reaction with atomic hydrogen is determined. Appearance of Si atoms in the plasma as a result of the etching was monitored with optical emission spectroscopy, and a very good correlation of intensity of Si lines at 288 H 390 nm wavelengths in the spectra with the etching rate is demonstrated. The data on the surface relief modification caused by the etching are presented.