掺氮SiC薄膜制备及其光学特性的研究

【作者】 赵武；

【导师】 张志勇；

【作者基本信息】 中国科学院研究生院（西安光学精密机械研究所） ， 物理电子学， 2009， 博士

【摘要】 硅碳氮（SiCN）薄膜作为一种新型三元薄膜材料具有优异的光、电和机械性能,此外,该薄膜独特的发光性能和从可见光到紫外光范围的可调节带隙,使其成为很有潜力的发光材料。本论文以制备高质量SiC,SiCN等半导体薄膜材料以及探索其光学特性为研究目标,该材料可用于制备应用于恶劣环境下的光电子器件及作为光学保护膜,主要工作包括以下几方面。首先,对实验中所用到的热丝化学气相沉积（Hot Filament Chemical VaporDeposition,HFCVD）设备进行了改造与设计。其次,以β-SiC和β-Si₃N₄晶体结构为基础,建立SiCN的基本模型。采用材料计算软件根据第一性原理的泛函理论对所建的模型进行计算。结果显示以β-Si₃N₄晶体模型为基础建立的SiCN模型较接近试验的结果。再次,以硅烷（SiH₄）、甲烷（CH₄）和氢气（H₂）为反应气体利用HFCVD法在硅、石英等衬底上成功制备了SiC薄膜。研究了预处理和薄膜生长的主要工艺对SiC薄膜的影响,并对制备工艺进行了优化。结果表明薄膜为排列致密整齐结晶度很高的3C-SiC薄膜,薄膜中Si、C原子比接近1:1并且分布均匀、稳定。FTIR谱和Raman谱分析显示沉积的SiC样品中,主要化学键为Si-C键。由于薄膜量子尺寸效应,根据紫外-可见谱（UV-vis）计算出薄膜光学带隙以及光致发光（PL）谱计算的禁带能量皆大于3C-SiC的带隙（2.40eV）。探索性研究了SiC薄膜的场发射特性,发现SiC薄膜的场发射特性不仅和薄膜的表面形貌有关和内部结构也有密切的联系。最后,利用热丝化学汽相沉积（HFCVD）法制备了SiCN薄膜。研究了主要工艺条件（氮气流量、甲烷流量和衬底温度等）对制备SiCN薄膜的影响,并对制备薄膜的工艺进行了优化。分析了SiCN薄膜的结构、形貌、组成成份及其化学键等,结果表明所制备薄膜为表面存在裂纹和空隙的、且晶化并不充分的一种新型SiCN薄膜。薄膜中Si、C、N三元素含量分布相对稳定,形成了Si-C,Si-N,C-N等化学键合态。讨论了SiCN薄膜的光学特性,利用紫外-可见透射谱分析N₂流量对SiCN薄膜的光学带隙的影响（2.33-2.94eV）,薄膜中的N含量对光学带隙的影响也不是简单的线性关系。利用nkd-8000型薄膜光学分析仪测试出所至备样品的厚度（d,808nm）、折射率（n,2.34～2.37）和消光系数（k,0.007～0.012）等。更多还原

【Abstract】 Silicon carbon nitride （SiCN） thin films, as a new ternary element films, exhibit outstanding optical, electrical and mechanical properties. Particularly they are proposed as candidates for luminescent application due to their extraordinary luminescent properties and adjustable band gaps varying from to visible light range. In this dissertation, we grow the silicon carbide （SiC） and SiCN semiconductor films by using the modified hot filament chemical vapor deposition （HFCVD） method and study their optical properties. The main work and results are listed as following.First of all, the modified hot filament chemical vapor deposition （HFCVD） system used in present dissertation is designed and developed.Secondly, based on the crystalline structure of theβ-SiC andβ-Si₃N₄, two kinds of elementary models of the SiCN structure are constructed and investigated by the first-principles calculation of plane wave ultrasoft pseudopotential. The calculated results indicate that the SiCN model based on theβ-Si₃N₄ structure is consistent with the experimental results.And then, SiC films are successfully deposited on silicon, quartz, etc... substrates by HFCVD method with the mixture of silane （SiH₄）, methane （CH₄） and hydrogen （H₂） used as reacting gas. The influence of pretreatment and growth technology on the SiC films is studied systematically and the technology is optimized. The deposited samples are highly crystallized 3C-SiC films consisted of compact and orderliness grains. And the atom ratio of Si to C reaches nearly 1:1 and these atoms distribute homogeneous. The FTIR and Raman spectrum confirm that Si-C bond take a dominant position in the deposited 3C-SiC samples. Because of quantum size effect, the band gap of the samples obtained by UV-vis spectroscopy and photo- luminescence （PL） is wider than that of the 3C-SiC bulk structure. Moreover, the field emission properties of the SiC films are explored, and it is found that the field emission properties are related to the surface morphology and structure of the films. At last, SiCN films are successfully grown on substrate（such as silicon, quartz）. The effects of technological conditions （nitrogen （N₂） flow rate, CH₄ flow rate, substrate temperature） on quality of SiCN thin films are analyzed and discussed and the growth technology is optimized. The structure, surface morphology, composition and chemical bond of the SiCN films are explored in detail. It reveals that there are some cracks and space in the surface of the prepared films, which means that a new material with undercrystal structure has formed. And the uniform distribution of Si, C, and N elements is observed in the film, altogether with Si-C, Si-N, C-N bonds. The UV-vis spectroscopy indicates that optical band gap of the SiCN films is affected by N₂ flow rate, and the relationship between the band gap and the N content in films is not linear. The film thickness （d,808nm）, refraction index （n, 2.34～2.37） and extinction coefficient （k, 0.007～0.012） are measured by nkd-8000.更多还原