Synthesis of Diamond Film at Low Temperature and Its Apprications

在纯CH4射频等离子体中沉积硬碳膜的机理研究中，提出了由离子鞘电位加速的离子与基体表面物理吸附的CH_3自由基的化学反应决定了薄膜沉积速率。等离子体中CH3数密度与总烃离子密度的乘积很好地描述了薄膜的沉积速率，这一事实也支持了该沉积模型。在不同的衬底温度下，研究了沉积在Si和Fe/Si衬底上的碳膜与Si衬底之间的膜性能和界面结构。薄膜的沉积速率很大程度上取决于衬底温度。当衬底温度升高时，其在200℃前显著降低，随后显示出中等程度的降低。在源气压力大于60 mTorr时，薄膜密度不受衬底温度的影响，而在小于60 mTorr时，薄膜密度随衬底温度的升高而增大，在400 C时达到2.8 g/cm^3。在向深度的薄膜结构中，400 C时沉积在Fe/Si衬底上的薄膜表面顶部保留Fe_xCy薄膜，薄膜下沉积有超硬的碳薄膜。该膜在CF4射频等离子体中的刻蚀速率远低于普通硬碳膜（约一个数量级）。在碳膜和硅衬底之间的界面上，存在一层非常薄的金刚石膜。

In the mechanistic study on the hard carbon film deposition in pure CH4 rf plasma, it was suggested that chemical reactions of ions, accelerated by ion sheath potential, and CH_3 radicals, physisorbed on the substrate surface, determine the film deposition rate. This deposition model is also supported by the fact that the product of CH3 number density and total hydrocarbon ions density in tha plasma, describes well the film deposition rate.The film properties and the structure of the interface between deposited carbon film and Si substrate, were examined for the films deposited on both Si and Fe/Si substrates with several kinds of substrate temperatures. The film deposition rate greatly depends on the substrate temperature. It considerably decreases until 200 C,and then indicates the moderate decrease, when the substrate temperature is increased. At source gas pressures more than 60 mTorr, the film density dose not depends on the substrate temperature, but at the pressures less than 60 mTorr it increases with increasing the substrate temperature, and then reaches to 2.8 g/cm^3 at 400 C.In the film structure toward the depth, for the film deposited on Fe/Si substrate at 400 C,Fe_xCy thin film remains at top of the surface, and under this film a superhard rbon filn is deposited. The etching rate of this film in CF4 rf plasma is much lower (by about a order of magunitude) than that of normal hard carbon film. At the interface between tha carbon film and the Si substrate, a very thin diamond film exists.