【作者】 彭银桥；

【导师】 周继承；

【作者基本信息】 中南大学 ， 材料科学与工程， 2013， 博士

【摘要】 硅碳氮(SiCN)集成了碳化硅(SiC)和四氮化三硅(Si3N4)的优良特性,具有高硬度、高抗氧化能力、化学惰性和宽带隙等优良的光、电和力学性能,在超硬涂层、光电子、铜互连的介质阻挡层以及微机电系统方面具有广泛的应用前景。其能发射蓝光或蓝紫外光的特点使其成为解决国际上“蓝光问题”的重点研究材料之一同时与硅集成电路工艺兼容特点使其成为光电集成电路的优选材料。但SiCN薄膜的成分、结构与特性非常复杂。本文作者使用两种工艺(Ar/C2H2/N2+多晶Si靶,Ar/N2+烧结SiC靶)制备SiCN薄膜样品,优化了制备工艺；使用光电子谱仪、红外傅立叶光谱仪、X射线衍射仪、紫外-可见分光光度计和荧光光谱仪等对薄膜样品的成分、化学键、晶体结构、光致发光等特性进行了表征；分析了薄膜的制备工艺、成分、微结构及光学特性之间的相互作用规律；探讨了SiCN薄膜的370nm、400nm和440nm发光机理。利用第一性原理的密度泛函理论和材料计算软件Material Studio5中CASTEP模块,基于β-Si6N8晶体模型构建β-Si12-nCnN16(n=0,4,6,8,12)超晶胞,并计算它们的结构和光学特性。结果发现随着碳(C)原子不断地替代Si原子,它们的晶格常数a、c及晶胞体积不断减少,但它们的a/c比值基本保持不变,表明SiCN在a和c方向保持各向同性收缩,β-Si12-nCnN16(n=4,6,8)超晶胞的能带结构特性更接近β-Si12N16,而不是接近β-C12N16；β-Si12-nCnN16(n=0,4,6,8,12)结构的光透性随n增大有变差的趋势,其吸收峰位置向短波长方向移动。研究了溅射功率对薄膜沉积速率、成分、微结构及光学带隙的影响及其影响机理。溅射功率增大,沉积速率先增大后减少,光学带隙单调减少,薄膜中C的含量单调减少,而Si的含量单调增大,N含量基本保持不变。发现SiCN网络结构中Si和C原子占据相似的位置。研究发现沉积态SiCN薄膜中主要形成了C-N、N-Hn、C-Hn、C-C、C≡N、Si-H和Si-C键,高溅射功率有利于C≡N、Si-H和C-Hn键的形成。研究了C2H2流速对薄膜沉积速率、成分、微结构及光学带隙的影响及其影响机理。C2H2流速增大,沉积速率急剧增大,薄膜中C的含量增大而Si和N含量减少,Si-C和C-N键单调增大,而Si-H键明显减少,以及薄膜光学带隙单调减少。发现薄膜中C含量的增加有利于Si-C和C-N键的形成,SiCN薄膜表面与薄膜内部的成键状态不一致,在薄膜表面形成了Si-O、C-C、C-O、C-N、N-Si和C=N键的网络结构。研究了N2/Ar流速比对薄膜沉积速率、成分、微结构及光学带隙的影响及其影响机理。N2/Ar流速比增大,薄膜的沉积速率增大,薄膜中N元素含量增加,而C和Si含量的减少,薄膜表面粗糙度增大。发现薄膜中N含量的增加促进了Si-N键的形成,而抑制了C-C、C-Si和N-C等键的形成；同时发现具有较高光学带隙的Si-N键增加,而较低光学带隙的Si-C、C-C和C-N键减少,从而引起薄膜光学带隙增大。研究了薄膜成分、微结构与薄膜发光特性的关系。在沉积态中观察到了400nm发光,在退火的SiCN薄膜中观察到了强烈的370nm和440nm发光。370nm、400nm和440nm的发光分别起源于SiCN薄膜中SiOx的发光中心、C团簇和SiC晶粒。发现600℃退火有利于SiCN薄膜中的SiC晶粒的形成,可以通过提高Si-C键的含量提高SiCN薄膜的440nm的发光强度。更多还原

【Abstract】 A compound of silicon carbonitride (SiCN) integrates the unique characteristics of SiC and Si3N4, and is of excellent optical, electrical and mechanical properties, such as high hardness, high antioxidant capacity, chemical inertness and wide band gap. It has potential application prospects in superhard coating, optoelectronics, dielectric barrier layer in copper interconnect and micro-electro-mechanical systems. Its characteristic of emitting blue or blue-ultraviolet light makes it to be one of the key research materials which can resolve the international "blue light" problem. And its compatibility with the silicon integrated circuits process makes it to be the preferred materials for optoelectronic integrated circuits. But its compositions, structures and properties are very complex. In this work, SiCN thin films were prepared using two kinds of process (Ar/C2H2/N2mixed gas+polysilicon target, Ar/N2mixed gas+sintered SiC target), and the characteristics of the composition, chemical bonding, crystal structure and photoluminescence were characterized by X-ray photoelectron spectrometry, Fourier transform infrared spectroscopy, X-ray diffraction, ultraviolet-visible spectrophotometer and fluorescence spectrometer. The mutual interactions among the preparation process, composition, microstructure and optical property of the films were analysized. The photoluminescence mechanisms of370nm,400nm and440nm for the SiCN thin films were discussed.Using the density functional theory of first-principles calculations and the CASTEP module of the material calculation software Material Studio5, the structures and optical properties of the constructed β-Si12-nCnN16(n=0,4,6,8,12) supercells based on β-Si6N8crystal structure were calculated. The results show that the lattice constants a, c and cell volume of the calculated supercells become smaller, while their a/c ratio is essentially unchanged when Si atoms are continually replaced by C atoms. These indicate they maintain isotropic shrinkage in the lattice a and c directions. The band structures of the β-Si12-nCnN16(n=4,6,8) supercells are closer to P-Si12N16rather than β-C12N16. The light transmission for β-Si12-nCnN16(n=0,4,6,8,12) structures has a trend of deterioration and their absorption peak wavelengths move to shorter wavelength with the increase of n.The influence of sputtering power on thin film deposition rate, composition, microstructure and optical band gap and its mechanism were studied. With sputtering power increasing, the deposition rate first increases and then decreases, and optical band gap monotonously decreases, and the Si content monotonously increases and the C content monotonously decreases while the N content is essentially unchanged. It is found that Si and C atoms accupy similar sites in the SiCN network. The C-N, N-Hn, C-Hn, C-C,C≡N, Si-H and Si-C bonds were mainly formed in the SiCN films, and a higher sputtering power is in favor of the formation of C=N, Si-H and C-Hn bonds.The influence of C2H2flow rate on thin film deposition rate, composition, microstructure and optical band gap and its mechanism were studied. With C2H2flow rate increasing, the deposition rate sharply increases, and the C content increases while the Si and N contents decrease in the films, and optical band gap monotonously decreases, and Si-C and C-N bonds monotonically increase while Si-H bond obviously decreases. It is found that the increase of C content favors to the formation of the Si-C and C-N bonds and supresses the formation of the Si-H bond. The bondings are not consistent between in the film surface and in the SiCN film, and Si-O, C-C, C-O, C-N, N-Si and C=N network structure is formed in the film surface.The influence of the N2/Ar flow ratio on thin film deposition rate, composition, structure and optical band gap and its mechanism were studied. With the N2/Ar flow ratio increasing, the deposition rate increases, and the N content increases while the Si and C contents decrease in the films, and the surface roughness values of the films increase. It is found that the increase of N content in the SiCN films promotes the formation of Si-N bond, and supresses the formation of C-C, C-Si and N-C bonds. The increase of Si-N bond with higher optical band gap and the decrease of the Si-C, C-C and C-N bonds with lower optical band gap bring about the increase of optical band gap of the SiCN film. The dependence of photoluminescence of the thin films on their compositions and structures were studied. The strong photoluminescence at400nm was observed in the deposited SiCN films, while the strong photoluminescence at370nm and440nm was observed in the annealed SiCN films. The photoluminescences at370nm,400nm and440nm respectively originate SiOx luminescence center, C clusters and the SiC crystal particles in the SiCN films. It is found that the600℃annealing favors to the formation of the SiC crystal particles in the SiCN film, and the emitting light intensity at440nm in the films can be improved by improving the content of the Si-C bond.更多还原