【作者】 赵楠；

【导师】 柴常春；

【作者基本信息】 西安电子科技大学 ， 微电子学与固体电子学， 2008， 硕士

【摘要】 SiC是一种宽带隙半导体材料,具有带隙宽、临界击穿场强高、饱和电子漂移速度大等优点,是高温、高频、高功率半导体器件的首选材料,在微电子学领域具有广阔的应用前景。由于SiC的单晶制备技术较复杂,成本较高,所以采用在Si基片上异质外延生长SiC的方法成为了研究的热点。然而这一方法首要需要解决的是SiC与Si之间存在较大的晶格失配度(约20%)和热膨胀系数差异(8%)。因此,SiC在Si基片上的异质外延制备仍存在困难,还有很多问题需要研究解决。本论文提出在多孔硅衬底上,采用常压化学气相淀积(APCVD)生长SiC薄膜的方法:首先通过双槽电化学腐蚀方法在待生长的Si基片上通过电化学腐蚀得到多孔硅结构作为缓冲层,其次再使用常规的APCVD方法在多孔硅结构上异质外延生长SiC。该方法的优点是利用了预处理的Si片表面的多孔结构来减小与SiC之间的晶格失配度,同时在APCVD生长过程中不用进行缓冲层的预生长,可以直接在多孔硅衬底上生长SiC薄膜。论文首先分析了APCVD法生长SiC薄膜的物理和化学机理。对生长的样品,采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)及其附件能谱分析(EDS)对外延薄膜的结构性质进行了分析。侧重研究了源气体Si/C比和生长温度对SiC薄膜质量的影响,研究结果表明:SiC薄膜的晶粒尺寸随Si/C比的减小而增大。硅碳比较小时,C的过量将导致化合反应过快,从而导致薄膜表面形成缺陷和空洞,表面变得粗糙;当硅碳比较大时,Si的过量又会使薄膜晶粒尺寸和分布不均匀;只有适当的Si/C比可以得到晶粒取向一致性较好和表面较平整的SiC薄膜。SiC薄膜的晶粒取向的一致性随着温度的进一步升高而变好,晶粒尺寸增大,生长的薄膜从多晶形态向单晶形态转变。更多还原

【Abstract】 Characterized by wide bandgap, silicon carbide is an excellent material with high breakage electric field, high thermal conductivity, high saturated electron mobility, which is considered as one of the most promising wide band gap semiconductors, and widely utilized in high temperature, high frequency and large power semiconductor devices. But the fabrication of single-crystal SiC costs too much and the process is very complicated, so the heteroexpitaxial growth of SiC on Si substrate become very popular in research. Due to the large lattice parameter mismatch(20%) and the large thermal expansion coefficient mismatch(8%), however, the heteroexpitaxial growth of SiC on Si substrate is difficult and still has problem to be studied.In this paper, the growth technology is presented for epitaxial silicon carbide films on porous silicon by atmosphere-pressure chemical vapor deposition(APCVD) process, that is, to fabricate porous silicon (PS) on the Si wafer by electrochemical etching method first in order to form a buffer layer, and then depositing the SiC films on this buffer layer. The porous silicon on the wafer was used to reduce the lattice parameter mismatch between Si wafer and SiC film, and then SiC film can be deposited on porous silicon without preparing a buffer layer on Si wafer in APCVD process.The chemical and physical process of atmosphere-pressure chemical vapor deposition SiC thin films is analyzed firstly. The structural properties of the films grown on porous silicon substrate are studied by X-ray diffraction(XRD), scanning electronic microscope(SEM) and EDS detector attachment to SEM. The effects of Si/C ratio of the source gas and growth temperature on the quality of thin films was studied in detail. It was observed that the size of particles in SiC film was increased with the decrease of Si/C ratio. The small Si/C ratio would accelerate the chemical process and lead to the formation of defeat and void on the surface of film, and the large Si/C ratio would lead to the different size and disorder of film particle. Only the proper Si/C ratio could obtain a SiC films that had a good single-crystalline orientation and a smooth surface. The single-crystalline orientation of the thin films meliorated with the increasing of growth temperature, the size of particles became large and the polycrystalline SiC films would turn to single crystal with the increasing of temperature.更多还原