CVD金刚石中的氮对等离子体刻蚀的影响

摘要

采用非对称磁镜场电子回旋共振等离子体分别对沉积过程中掺氮和未掺氮的化学气相沉积金刚石膜进行了刻蚀研究,结果表明：掺氮制备的金刚石膜的刻蚀主要集中在晶棱处,经过4h刻蚀后其表面粗糙度由刻蚀前的4.761µm下降至3.701µm,刻蚀对金刚石膜的表面粗糙度的影响较小；而未掺氮制备的金刚石膜的刻蚀表现为晶面的均匀刻蚀,晶粒坍塌,刻蚀4h后其表面粗糙度由刻蚀前的3.061µm下降至1.083µm.刻蚀导致表面粗糙度显著降低.上述差别的主要原因在于金刚石膜沉积过程中掺氮导致氮缺陷在金刚石晶棱处富集,晶棱处电子发射加强,引导离子向晶棱运动并产生刻蚀,从而加剧晶棱的刻蚀.而未掺氮金刚石膜,其缺陷相对较少且分布较均匀,刻蚀时整体呈现为(111)晶面被均匀刻蚀继而晶粒坍塌的现象.%Nitrogen-doped and undoped diamond films grown by microwave plasma chemical vapor deposition (CVD) were etched by electron cyclotron resonance (ECR) plasma with asymmetric magnetic mirror field. The influences of nitrogen doping on the etching characteristic of CVD diamond films are studied by scanning electron microscope (SEM), X-ray photoelectron spectroscopy(XPS), and surface roughness measuring instrument; and the etching mechanism is explicated in detail by etching models. It is found that the crystal edges are dramatically etched for the nitrogen-doped diamond film, while the (111) facets are etched and crystalline grains collapse for the undoped diamond film. And after etching by ECR plasma for 4 h, the nitrogen-doped diamond film surface roughness decreases from 4.761 µm to 3.701 µm, while the surface roughness of the undoped film decreases from 3.061 µm to 1.083 µm. The results indicate that nitrogen doping has great influence on the etching characteristic of the CVD diamond films. Nitrogen-doping deteriorates the film quality and increases the defect density in the crystallites. And the defects distributed in the crystal edge lead to dramatically etching of the crystal edge. Compared with the nitrogen-doped diamond film, the defect density in undoped diamond film is relatively low and the distribution of defects is comparatively uniform, resulting in the fact that (111) facets would suffer from oxygen cyclotron ion beams bombardment and so grains of the film collapse. The reason why the surface roughness of nitrogen-doped diamond film decreases less than the undoped diamond film is that the movement of ions is affected by the electrons emitting from crystal edge, which weakens the ion bombardment on (111) facets.