Effect of adding an upper-substrate holder in the quartz-tube MPCVD on plasma parameters

Abstract

An upper-substrate holder is introduced into the quartz-tube microwave plasma chemical vapor deposition (MPCVD) resonant cavity. For two configurations of substrate holder, standard without upper-substrate and modified with upper-substrate, the distribution of detected H, temperature (Te) and density (Ne) of electrons in the plasma above the substrate surface was monitored by optical emission spectroscopy. Finite element simulation of electric field distribution and intensity shows that in modified resonant cavity (with upper-substrate holder), the electric field intensity is more concentrated and higher than in traditional resonant cavity under the same discharge deposition parameters. As a consequence of a more intense electric field in the plasma above the substrate, an increase in Te and Ne was observed in modified resonant cavity. At the same time, the diamond coatings deposited in the modified resonant cavity has a significantly higher growth rate as well as higher phase purity, well (111) crystal plane considering the results of Raman spectroscopy (more intense peak 1332 cm−1, as well as less presence of sp2 phase) and XRD than deposits in traditional resonant cavity.