Synthesis of Diamond Film at Low Temperature and Its Apprications

在纯CH_4射频等离子体中沉积硬碳膜的机理研究中，提出了离子鞘层电位加速的离子与物理吸附在基片表面的CH_3自由基之间的化学反应决定了膜的沉积速率。用等离子体中的CH_3数密度与总碳氢离子密度的乘积来描述薄膜的沉积速率也支持了这一沉积模型.本文研究了在Si和Fe/Si两种衬底上沉积的碳膜在不同衬底温度下的薄膜特性和沉积碳膜与Si衬底的界面结构.薄膜沉积速率很大程度上取决于衬底温度。当衬底温度升高时，它显著降低，直到200 ℃，然后指示适度降低。当源气压大于60 mTorr时，薄膜密度与衬底温度无关，但当源气压小于60 mTorr时，薄膜密度随衬底温度的升高而增加，400 ℃时达到2.8 g/cm^3。在向深处的薄膜结构中，400 ℃时沉积在Fe/Si衬底上的薄膜，Fe_xCy薄膜仍保持在表面顶部，并且在该膜下沉积超硬Rbon膜。该膜在CF_4射频等离子体中的刻蚀速率比普通硬碳膜低得多（约一个数量级）。在碳膜和硅衬底的界面处，存在一层很薄的金刚石膜。

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.