Synthesis of CBN Films by A New Plasma CVD Apparatus with Thermal Electron Radiation

已经开发了几种类型的等离子体CVD设备，其能够有效地形成cBN膜。在等离子体化学气相沉积（CVD）技术的发展过程中，通过电磁和热的方式将高能引入反应空间以激发等离子体是非常重要的。坩埚盖上有小孔，以便高能等离子体喷出。射频线圈围绕坩埚。在一定的最佳工艺条件范围内，cBN的生成率得到了很大的提高，生成的BN膜中cBN的体积分数约为100%。发现钨丝加热通过激发等离子体气体以产生高能离子、自由基和原子而有助于cBN的形成。所产生的原子氢被发现相当大地蚀刻所沉积的t-BN结构，以在BN膜中得到高体积分数的cBN。结合sp^2和sp^3电子轨道的原子势定性地讨论了cBN的形成机制，提出了cBN（或金刚石）形成机制的新概念，即具有sp^3态的B-N-H自由基在台阶或扭结上被捕获和猝灭，成为cBN成核和生长的稳定位置。

Several types of plasma CVD apparatus have been developed which enable the formation of cBN films effectively. In the development, it was essentially important to introduce high energy into reaction space electromagnetically and thermally for the excitation of plasma.A recently developed plasma CVD apparatus is composed of Knudsen-cell -type crucible in which a tungsten filament is mounted. The crucible is covered by a cap with a small-pinhole for the high energy plasma to jet out. The radio frequency coil is.around the crucible. With this apparatus the formation yield of cBN has been so such increased and BN film of about 100% cBN in volume fraction was formed in some range of optimum condition. It was found that the tungsten filament heating contributes to the cBN formation by an excitation of plasma gas to create high energy ions,radicals and atoms. The created atomic hydrogen was found to etch the deposited t-BN structure considerably to give high volume fraction of cBN in the BN films. A mechanism for the cBN formation was discussed qualitatively in relation to atomic potentials with sp^2 and sp^3 electron orbitals.Conclusively, a new concept on the formation mechanism of cBN (or diamond) has been constructed that cBN is made on substrate when the B-N-H radicals with the sp^3 state are trapped and quenched on steps or kinks as stable sites for the nucleation and growth of cBN.