Research Of The Controllability Of The CVD Diamond Film Deposition

The excellent physical and chemical properties of CVD diamond film make it won thegood application in many fields, especially in high-tech areas like the military andaerospace, it’s more urgent demand for high quality CVD diamond film. Now theresearchers at home and abroad are focused on the research how to get the high qualitydiamond film which is to meet various application requirements, and the main way is toexplore the inherent law from the aspects of diamond film growth process parameters. Thisthesis is mainly to study the influences of process parameters on diamond film growth, andexplore the influence law of thin film growth after the nitrogen has been introduced byusing microwave plasma chemical vapor deposition (MPCVD).Based on the effect of process parameters on diamond film deposition, we found thatthe low substrate temperature (800℃) leads to secondary nucleation increase in the growthprocess of the diamond film, diamond growth rate is reduced, grain size is smaller, and theetching effect of atomic hydrogen on non diamond phase weaken, the quality of thediamond film was poor. Substrate temperature (950℃) leads crystal type of diamond to benot obvious, and grain is arranged chaotic, surface topography was poor. The higher carbonsource concentration (2%) make the growth rate faster, but the atomic hydrogen etchingeffect is reduced, the quality of the film gradually decline. Low carbon sourceconcentration (0.5%) can lead to the growth rate of thin film is too slow, and increase thesecondary nucleation rate, grain size is also very small. This research further explores thecoupling relationship between substrate temperature and the concentration of carbonsource when diamond film deposition on the cases of1%carbon source concentration. Theresults show that in the process of the substrate temperature has risen from750℃to1000℃, the changes of diamond film surface morphology can be divided into five stages,it can be deposited respectively the <100> orientation and <111> orientation of diamondfilm in medium substrate temperature (870℃~920℃) and higher substrate temperature(960℃~1000℃).At the same time this thesis also systematic discusses the influence of introducing the nitrogen for diamond film deposition. When the substrate at a high temperature (980℃),the increase of nitrogen concentration can significantly increase the grain size of diamondfilm; But when the substrate at a low temperature (800℃), the grain size of diamond willsignificantly reduce with the increase of nitrogen concentration. While the increase ofnitrogen concentration will also decrease the quality of the diamond film. Based on thesystem analysis of experimental results, it explores the coupling relationship of substratetemperature and nitrogen concentration on the influence of grain size of diamond. Resultsshow that the increase of nitrogen concentration can significantly increase the grain sizeand growth rate of diamond film when the substrate in850℃~950℃temperature range,which is beneficial to micron grade diamond film high speed of deposition; When thesubstrate temperature is in750℃~820℃temperature range, the effect of introducenitrogen is mainly manifested in the increase of the diamond film secondary nucleationrate, and reduced the grain size of diamond film, which will be conducive to nanometerdiamond film deposition.This research through systematic analyze the experiment, in10kW cylindricalmultimode resonant cavity MPCVD device, it basic grasped the general regularity of theprocess parameters on the high quality diamond film deposition, and provided a theoreticalsupport for achieving the high quality diamond film growth.