微波等离子化学气相沉积金刚石膜新型微波谐振腔设计

Design of novel microwave cavity for MPCVD diamond film

提出新型微波谐振腔用于化学气相沉积金刚石薄膜,腔体有效体积可以调节,采用环形介质窗口,置于沉积基台的下方,允许产生较大并且温度较高的等离子体。同轴内导体与沉积台相连接,微波从谐振腔底端传输经同轴导体耦合进入腔体。采用有限元的方法优化谐振腔的尺寸,使其能耦合进更大的微波能量,优化后,最大电场区域位于沉积台上方,并且均匀分布,在腔体内其它区域和介质窗口附近电场强度则很小,满足设计要求。采用时域有限差分法模拟了谐振腔在一定微波输入功率下产生等离子体的特性,并对设计的谐振腔进行试验研究,实验观察到的等离子体位置与模拟结果一致。

New microwave cavity for diamond film deposition was proposed in this paper,the effective volume of cavity can be adjusted,ring shape quartz window is located under the substrate holder,which is far from the plasma,allowing to generate plasma with high temperature.Inner conductor is connected with the substrate holder,microwave power enters the chamber from the bottom of the cavity.Numerical simulations were performed to optimize the geometry by finite element method（FEM）,after optimization,the electric field in cavity exhibits one maximum and homogeneous distribution on substrate.Especially,it is very weak near the dielectric window,which satisfy the requirement of design.The calculation of the number density of electrons by finite difference time domain（FDTD）method,primary experiment was carried out,the shape and position of plasma are consistent with numerical prediction.