Optoelectronic monitoring of plasma discharge optimized for thin diamond film synthesis

Abstract
We used Optical Emission Spectroscopy (OES) as a non-invasive optoelectronic tool of in-situ monitoring of plasma discharge. The low-temperature plasma, based on mixture of CH₄ and H₂, was produced during Microwave Plasma Assisted Chemical Vapour Deposition (PA CVD) synthesis process of thin diamond/DLC films. Molecular modelling showed that quality of the synthesized films is determined by total amount as well composition ratio of ions H⁺ and CH₃⁺, produced in an area of Electron Cyclotrone Resonance (ECR). Therefore, dissociation of H₂ molecules as well as excitation and ionization of hydrogen atoms were a subject of the presented OES studies. Developed monitoring systems uses spectrometers coupled with the reaction chamber by a dedicated optical probe and a fibre bundle. Intensity of Balmer and Paschen series were measured as a function of main CVD process parameters.