温度对化学气相沉积碳化硅涂层的影响

Effect of temperature on the chemical vapor deposition of silicon carbide coatings

以三氯甲基硅烷和氢气为气源,研究了化学气相沉积碳化硅过程中,温度(850-1350℃)对沉积速率、反应物消耗效应、涂层形貌和相结构的影响.用磁悬浮天平在线实时称量基体质量变化进行动力学研究;采用扫描电镜和X射线衍射对样品做了表征.结果表明,沉积过程存在四个控制机理:a区(<1000℃)为表面反应动力学控制;b区(1000-1050℃)主要是HCl对沉积的抑制作用;c区(1050-1300℃)是表面化学反应和传质共同控制;d(>1300℃)为传质为限速步骤.由于不同的控制机制,导致所得涂层的形貌存在差异.含碳含硅中间物质浓度的减小、HCl增多和MTS的分解共同导致反应物消耗效应.涂层由热解碳和碳化硅两相组成,温度的升高使热解碳相减少,碳硅比接近1.

The effect of temperature（850-1350 ℃） on deposition rates,reactant depletions,surface morphologies and microstructures was investigated in chemical vapor deposition（CVD） of silicon carbide coatings from methyltrichlorosilane and hydrogen system at constant pressure and flow rates.The in-situ kinetics by magnetic suspension balance shows that there are four rate-limiting mechanisms：the surface reactionsin a region（1000 ℃）;the inhibition of HCl from deposition rate in b region（1000-1050 ℃）;the combination of surface reactions and mass transfer in c region（1050-1300 ℃）,and the reactant depletions in d region.The different rate-limiting mechanisms result in different coating morphologies.The combination of decreased concentrations of carbon-containing,silicon-containing species increased,HCl and decomposition of MTS causes the reactants depletion.The XRD results show that coatings consist of porlycrystalβ-SiC.The C/SiC is gradually close to 1 with the increasing temperature.