Increased O (¹D) metastable density in highly Ar-diluted oxygen plasmas

Enhancement of the growth rate of Si O2 with a rare gas diluted O2 plasma is of interest for application to various microelectronics fabrications. The key is the oxygen metastable atom (D1) density, which has the potential for surface activation. We used vacuum ultraviolet optical absorption spectroscopy to detect O (D1) and found a twofold increase in the density of O (D1) due to the dilution with Ar. The density increase is reasonably explained by the increase of the electron density, the oxygen dissociation fraction, and the Ar metastable density, that are experimentally obtained for low O2 fractions.