【作者】 李磊；

【导师】 黎向锋； 左敦稳；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2007， 硕士

【摘要】 在热丝化学气相沉积(Hot Filament Chemical Vapor Deposition,简称HFCVD)金刚石膜的系统中,系统温度场和流场的分布直接决定着金刚石膜的形核密度和生长速率。本文对影响系统温度场和流场的相关工艺参数进行了系统的模拟计算,确定了生长大面积优质金刚石膜的工艺参数优化值,主要工作如下:1.选取氢气作为HFCVD系统中流场的主要研究对象,经计算该流场的雷诺数Re=979.3,马赫数Ma=0.05,最终确定流场的流态为层流、不可压缩流体的低速流动,为热-流耦合分析奠定了理论基础。2.采用K型热电偶对Φ80mm的平面衬底沿径向距中心不同距离处的温度进行了多点测量,得到了衬底表面温度分布曲线。在ANSYS中建立热丝和Φ80mm平面衬底的三维有限元模型,对多种沉积参数影响下的衬底温度规律进行了详细地仿真计算。结果表明,考虑衬底三维热传导以及热丝温度的不均匀分布条件下衬底温度场与纯热辐射相比更加接近实验结果。3.在FLOTRAN CFD中建立了热丝、衬底和氢气的二维热-流耦合模型,仿真计算了不同沉积参数影响下的系统温度场和流场分布,同时分析了热丝阵列附近气体“热绕流”的成因及其对金刚石膜生长的影响。4.根据仿真结果优化出生长Φ80mm金刚石膜的工艺参数:热丝根数n=14,热丝-衬底距离Hf=5mm,热丝间距df=6mm,热丝半径Rf=0.3mm,气体进口速度Vin=2.36m/s,进气口数Nin=1。采用优化工艺参数进行了金刚石膜的沉积实验,结果表明,金刚石膜总体质量较高,中心呈(100)晶面,边缘呈(111)面,生长速率在4～6μm/h之间,中心的生长速率略低于边缘的生长速率,与仿真结果是一致的。5.将HFCVD系统热丝和平面衬底的三维温度场计算模型推广到大面积曲面衬底及拉丝模的应用上,从温度场的角度,对在球面衬底和拉丝模上沉积金刚石膜的可行性进行了研究。更多还原

【Abstract】 Temperature distribution and flow field of the system, to a great extent, significantly affect the nucleation density and growth velocity of diamond film over large area by Hot Filament Chemical Vapor Deposition （HFCVD）. In this paper, the influence of various deposition parameters on the temperature and flow field is investigated. Then the parameters are optimized for the growth of diamond film over large area. The main works are as follows:1. H₂ is chosen as the main research object of fluid in HFCVD system. It is calculated that the Reynolds number is 979.3 and the Mach number is 0.05. Therefore, the flow regime is laminar, incompressible and low-speed flow.2. Multipoint temperature of the planar substrate with the diameter of 80 millimeter is measured by the K-thermocouple. And the temperature distribution curve of the substrate surface is attained. Then using the 3D finite element （FE） model of filaments and substrate in ANSYS, the influence of the hot filaments parameters and thermal contact resistance on substrate temperature is simulated in detail. According to the results, when the effect of 3D-substrate heat conduction and the nonuniform filament temperature distribution are considered, the substrate temperature field is more uniform than in pure heat radiation system.3. Using the 2D thermal-flow coupled model of the hot filaments, substrate and H2 in FLOTRAN CFD, the effect of different deposition parameters on the system temperature and flow field is simulated. The results reveal that the high temperature of hot filament array leads to thermal round-flow of gas which can’t be ignored in the growth of diamond film.4. The optimized deposition parameters based on the simulation results are: the number of the hot filaments is 14, the radius of the hot filaments is 0.3 millimeter, the distance between the hot filaments and substrate is 5 millimeter, the distance between the hot filaments is 6 millimeter, the velocity of the gas inlet is 2.36 meter per second, and the number of the gas inlets is 1. The high quality diamond film of 80 millimeter diameter deposited in HFCVD system is obtained using the optimized deposition parameters. The polycrystalline diamond film presents the （100） facets in the center and （111） facets in the fringe. And the growth rate of the diamond film in the center is lower than that in the fringe, which is consist with the simulation result.5. Based on the research of the temperature distribution of the planar substrate, the simulations of spherical substrate and wire drawing die HFCVD system are developed. According to the temperature field, it is feasible to deposit diamond films on the spherical substrate and wire drawing die.更多还原