Optical emission spectroscopy of low temperature CVD diamond
Abstract
The gas phase chemistry in low temperature (< 300°C) diamond and DLC chemical vapor deposition processes was investigated using optical emission spectroscopy (OES) to determine the effects of the different deposition parameters such as methane concentration, substrate temperature, plasma current and gas pressure in relation to diamond growth on silicon substrates. The OES data were analyzed to qualitatively monitor the important factors favorable for diamond deposition such as the mean electron temperature, Te, and the relative concentration levels of methane radicals (CH and CH+) as inferred from intensity ratios of spectral lines. The results indicated that the optimum deposition parameters for the low temperature diamond CVD system can be achieved by applying low methane concentration (1% to 3% methane in hydrogen), high substrate temperature (above 200°C), low pressure (< 20 Torr) and high plasma current (above 30 mA).
Diamond films were attempted to be deposited on silicon substrates while gathering the OES data using varying methane concentrations (1%, 3%, 5% and 8 % methane in hydrogen) at fixed pressure (10 Torr) and fixed plasma current (50 mA). X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) characterization of the deposited samples confirmed that diamond films were deposited at low methane concentrations (1% to 3%). Also, film samples deposited substrate temperature above 200°C yielded diamond characteristics.