Development of insulating system with low dielectric constant, high dielectric strength a-C:F film coated conductor prepared by plasma CVD as alternatives to SF_6

为了减少具有高GWP（全球变暖潜势）的SFs绝缘气体的使用，本项目提出采用射频等离子体CVD法制备的a-C:F膜涂覆导体作为SF_6的替代品，用于电力系统的绝缘。这个项目的动机是，如果使用全氟碳蒸汽，我们在射频等离子体中经历了非常高的沉积速率。主要结果如下：1。在Si和A1衬底上的沉积速率为100 ~ 200nm/min，比传统的CF_4和C_2F_6气体的沉积速率提高了几十倍。由C-C和C-F键组成的a-C:F薄膜具有优良的绝缘性能（介电常数【近似等于】2）、高密度和良好的热强度。在低p（压力）d（间隙长度）区，a-C:F膜Al电极间的N_2、Ar和He击穿电压V_s比Al电极间的击穿电压V_s大3倍。当pd<20 Torr/cm时，V_s明显高于sfs。V_s增强的原因可以解释为该膜涂层显著降低了二次电子发射速率。等离子体中分解物质对a-C:F膜性能的影响曾试图进行研究，但在本项目期内并没有得到真正的明确。

In order to reduce the usage of SFs insulation gas, which has high GWP (global warming potential), the present project proposed to use a-C:F film coated conductor prepared by RF plasma CVD method for insulation of electric power systems as alternatives of SF_6. This project was motivated because we had experienced very high deposition rates in RF plasma if per-fluorocarbon vapors were used. The main results are listed as follows.l. The deposition rate on Si and A1 substrates was > 100-200nm/min, which is a few tens times higher than those obtained by conventional CF_4 and C_2F_6 gases.2. The a-C:F film, which is composed of C-C and C-F bonds, was excellent insulation properties (dielectric constant 【approximately equal】 2) with high density and good thermal strength.3. The breakdown voltage V_s of N_2, Ar and He between the a-C:F film coated Al electrodes were 3 times larger than that between Al ones in low p(pressure)d(gap length) region. For pd<20 Torr/cm the V_s was rather higher than that of SFs.4. Reason of the enhancement of V_s was explained by the fact that secondary electron emission rate was reduced significantly by this film coating.5. Effect of decomposed species in the plasma on the a-C:F film properties was tried to examine, but in this project term it was not really cleared.