Growth Of Diamond Films By Hot Filament Chemical Vapor Deposition

Abstract

Results of research on diamond films grown by the hot filament chemical vapor deposition process are discussed. The parameters for film deposition have been surveyed and the conditions for routine and reproducible film formation established for our deposition system. These were: 800°C substrate temperature, 52-78 sccm flow rate, 5x103 Pa deposition pressure and 99.5% H2, 0.5% CH4 gas composition. Characterization of the deposited films has been accomplished with scanning electron microscopy (SEM), x-ray diffraction (XRD), Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS) and Raman spectroscopy; and the presence of the diamond phase was verified. Initial depositions on Si and Al203 substrates resulted in individual diamond particles showing the distinct diamond morphology. These particles, when examined by Raman microprobe spectroscopy, displayed the diamond spectra. Subsequently, continuous diamond films were formed after pretreating the substrates by rubbing with 1 pm diamond abrasive before deposition. Films, all shown to be diamond, grown on fused silica, polycrystalline SiC and different orientations of single crystal Si (all pretreated), exhibit very similar surface topography and x-ray diffraction patterns. Additionally, x-ray diffraction shows no preferred orientation in the films. Mechanical surface measurements on a 5 pm thick film grown on Si show that the films possess an average surface roughness of 0.4 μm and a peak-to-valley roughness of 2.5 μm. Films deposited on optically clear fused silica substrates could be seen to be water white, suggesting no significant optical absorption. Considerable optical scatter, however, is present due to the roughness of the film surface. Deposition rates were of the order of 0.1 μm/hr, with the fastest apparent growth occurring on pretreated polycrystalline SiC substrates.