Deposition And Bom-doping Of Nano-Crystalline Iamond Films

Nano-crystalline diamond （NCD）, compared to the micron diamondfilms, have great application prospect in high-power and high-frequencysemiconductors due to its excellent properties, such as high thermalconductivity, high elastic modulus, high dielectric breakdown field strengthand high carrier mobility. At present, two important problems in the field ofNCD film semiconductor applications need to be solved:1.how to get a largearea, high flatness NCD work layer;2. how to get more mature NCD dopingprocess. If these two problems can be solved, the industrialization of NCDsemiconductor will be just around the corner.In this work, the growth and doping technique of NCD films wasstudied by Microwave Plasma enhanced Chemical Vapor Deposition（MPCVD） method, and on the5kW-MPCVD devices, boron doping of NCDfilms on silicon substrate was carried out, which provide a good theoreticalbasis to the semiconductor devices application of NCD films as much aspossible.The new multimode microwave frequency of MPCVD devices forNCD deposition is2.45GHz, and the maximum output power is10kW. TM01and TM02were two microwave modes that mainly be used in the experiment.The superposition of two microwave modes can form a diameter of about150mm ball of plasma above the water-cooled substrate, which can realize theobjective of the deposition of large area diamond films. The growth anddoping technique of NCD films was prepared on mirror polishedsingle-crystalline silicon substrate, which grinded by Nano-diamond powderbefore the deposition of NCD to improve the nucleation rate. By analyzing the deposition temperature, microwave power and reaction pressure, theconcentration of carbon source and the effect of oxygen on the deposition ofNano-crystalline Diamond Films, the ideal process conditions to prepare largearea, high formation degree of Nano-diamond films were that the depositiontemperature was controlled at680℃and the concentration of H₂/CH₄/O₂was200/12/4, and we get the properties of NCD film were the diameter is100mm, and the surface roughness is26.8nm.Boron doping of NCD films on silicon substrate was carried out on thestainless steel5kW-MPCVD devices.The influence of doping temperature,deposition pressure and boron concentration on the doping of NCD thin filmwere studied and analyzed. The surface properties of boron-doped NCD filmwere analyzed by AFM and the electrical properties of films were analyzed byFour-Probe resistance tester. Well doped NCD thin films were obtained at220ppm boron concentration, doping temperature of700℃and reactionpressure of6kPa.In this thesis, the research provided good experimental guidance toprepare a large area, high smoothness of NCD thin film and goodexperimental basis for the NCD film semiconductor applications.