Abstract
We have developed a measurement technique for absolute hydrogen (H) atom densities in process plasmas using a vacuum ultraviolet absorption spectroscopy (VUVAS) technique employing a high-pressure microdischarge hollow cathode lamp (MHCL) as a Lyman α (Lα, 121.6 nm) emission light source. The characterization of the Lα emission line profile could be simplified by using a high-pressure discharge at about 1 atmosphere. In order to evaluate the absolute H atom density, the estimation of the self-absorption and the emission line profile of the MHCL have been carried out. Using the VUVAS technique with the MHCL, the absolute density of H atoms was measured in inductively coupled hydrogen molecule plasmas. The H atom density increased from 1.4 × 1011 cm-3 to 1.2 × 1012 cm-3 with increasing the pressures from 1.33 Pa to 66.5 Pa at a power of 100 W.
