等离子体增强化学气相沉积法制备立方氮化硼薄膜过程中的表面生长机理

利用感应耦合等离子体增强化学气相沉积法以Ar，He，N₂和B₂H₆为反应气体制备了高纯立方氮化硼薄膜.用四极质谱仪对等离子体状况进行了系统的分析，发现B₂H₆完全被电离而N₂只是部分被电离.H₂和过量的N₂在等离子体中生成大量中性的H原子和活化的N^*₂，它们与表面的相互作用严重地阻碍了立方 关键词： 立方氮化硼薄膜 等离子体 质谱

Surface growth mechanism of cubic boron nitride thin films prepared by plasma-enhanced chemical vapor deposition

Chemical species in the low-pressure inductively coupled plasma for cubic boron nitride (cBN) film deposition using B₂H₆, N₂, He and Ar as reactant gases were investigated by quadrupole mass spectrometry. B₂H₆ was found to be ionized totally, while N₂ was only partially ionized. The species in plasma were Ar, He, N₂ molecules and Ar⁺, He⁺, N⁺, N⁺₂, B⁺, B_xH⁺_y, H⁺ and H⁺₂ ions, no H and N radical was detected by appearance potential mass spectrometry. The introduction of H₂ and N₂ gases into the deposition system was found to produce a large mount of H radicals and excited N^*₂ molecules, which suppressed the cBN formation by reacting with the growth surface. The etching and sputtering of cBN and turbostraotic boron nitrde (tBN) by H₂ and Ar plasmas were also evaluated, and we did not find that the tBN is selectively etched or sputtered. Moreover, high-resolution transmission electron microscopy of as-deposited cBN on the edge of ultrathin silicon flake substrate showed that the surface of as-deposited cBN film was composed of cBN {111} nanofacets, and no thin sp²-bonded boron nitride surface layer was observed. Our results suggest that cBN nucleates and then grows on the top surface in chemical vapor deposition systems, and the processes of cBN surface nucleation and growth in the present system was also discussed simply.