Research On The Preparation Process And Performance Of The CVD Diamond Thin Films For Industry Application

Chemical vapor deposition diamond thin films have a wide range of applicationsin mechanics, acoustics, thermal and electronics fields for its remarkable physical andchemical properties. The preparation of diamond thin films on the silicon wafer andcemented carbide substrate by means of adopting self-designed high-power HFCVDsystem in this paper. Moreover, the uniformity, surface roughness, adhesion propertiesand thermal properties of diamond thin films have been system analyzed andinvestigated.The deformation problem of substrates during HFCVD diamond films depositionhas been dealt with and deposition of uniform, large area thin diamond films has beenrealized on3inch diameter,0.4mm thickness silicon wafers through the adoption ofthe substate rotation and filaments ununiformity arrange. It is shown that substaterotation can minue gain, improve the uniformity of the film, but slow down thegrowth rate at the same time. The finite element analysis of substrate temperaturefield indicate that the uniformity and the isothermal area of substrate temperaturefield remarkable improved and enlarged by adopting filament ununiformity arrange.Deposition pressure is a important process method to control grain size andsurface roughness of diamond films.The results indicated that the re-nucleation rate ofCVD willl increase, grain size smaller, surface roughness reduce, with the reductionof deposition pressure. Nano-diamond film with20nm grain size and the25nmsurface roughness has been prepared by ultra low deposition pressure.Pretreatment process and deposition process have a significant impact on theadhesion strength of diamond films on cemented carbide substrate. The results showthat the combination pretreatment method can enhance the nucleation density andadhesive strength of diamond films. Too high or too low deposition pressure and theacetone concentration have a negative impact on the bonding properties of diamondfilm coated tools, so the much more appropriate for the deposition pressure andcarbon concentrations were4kPa and4%.The thermal conductivity of diamond thin film/composite substrate were testedby photothermal deflection technique. The results show that the better the quality ofdiamond thin films, the higher degree of (220) preferred orientation, the larger size ofgrain, the more thicker of film thickness, and the much more higher of the thermal conductivity.