带偏角4H-SiC同质外延生长和拉曼散射研究

发布时间：2018-01-17 14:08

  本文关键词：带偏角4H-SiC同质外延生长和拉曼散射研究　出处：《西北大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 4H-SiC 拉曼光谱 载流子浓度 LOPC模

【摘要】：碳化硅(SiC)属于第三代宽禁带半导体材料,是重要的间接带隙半导体之一,具有优异的物理特性和电学特性。因而,SiC电子器件非常适合在高温、高频和大功率等特殊情况下工作,在许多领域都具有很重要的应用价值。制造SiC功率器件的关键之一,是在4H-SiC上生长一层同质外延层,其物理、电学特性,都与其掺杂的载流子浓度密切相关。因此,需要一种有效可靠的方法对4H-SiC外延层的载流子浓度进行研究。拉曼散射是一种对实验样品没有损害的测试方法,不用对样品进行专门的处理,并可以方便快捷的对样品结构进行分析。本文使用水平热壁低压化学气相沉积技术,进行了有偏角4H-SiC衬底上同质外延生长工艺的实验,对三个影响载流子浓度的实验参数进行对比实验,得出最适合拉曼散射载流子分析的碳硅比、生长温度和生长气压。经过对比分析后,我们使用最佳的实验方案：在偏离(0001)面8。的2寸n型4H-SiC单晶上生长不同掺杂浓度的外延层。制备过程中SiH4、C3H8作为Si源和C源；高纯N2与TMA作为掺杂的N和Al源,氢气为载气。外延样品生长温度在1580℃,压力为100mbar。通过调节N2与TMA来改变掺杂N和A1的浓度。在室温下对不同掺杂浓度的4H-SiC外延层进行拉曼光谱测试,通过使用MATLAB拟合等离子声子耦合模的线型,并通过扩展的经典介电函数计算出载流子的浓度。通过对比发现经过拉曼测量后计算出来的载流子浓度的理论计算值,与SIMS测量的结果符合的很好。即可与通过拉曼测试来给出材料的载流子浓度。对LOPC峰进行分析,发现随着掺杂浓度的变大,载流子浓度变大,LOPC峰蓝移,频移变大,散射强度变小,峰宽变宽。LOPC峰发生蓝移主要和压缩应力有关。随着掺杂浓度的增加,其LOPC峰的半高宽会变宽,这与晶体内缺陷的变化有密切关系。随着掺杂浓度的增大,使得自由载流子浓度增加,自由载流子数量的增加就会使得势能降低,从而引起散射强度降低,随之引起峰强的变化。
[Abstract]:Silicon carbide (sic) is one of the third generation wide band gap semiconductor materials and is one of the important indirect band gap semiconductors with excellent physical and electrical properties. Therefore sic electronic devices are very suitable for high temperature. High frequency and high power are very important applications in many fields. One of the keys to fabricate SiC power devices is to grow a homogeneous epitaxial layer on 4H-SiC. The electrical properties are closely related to the carrier concentration. An effective and reliable method is needed to study the carrier concentration of 4H-SiC epitaxial layer. Raman scattering is a kind of testing method without any damage to the experimental sample. The structure of the sample can be analyzed conveniently and quickly. In this paper, the experiment of homoepitaxial growth on 4H-SiC substrate with deflection angle was carried out by using horizontal hot wall and low pressure chemical vapor deposition technology. The three experimental parameters affecting carrier concentration were compared, and the C / Si ratio, growth temperature and growth pressure which were most suitable for Raman scattering carrier analysis were obtained. We use the best experimental scheme: the epitaxial layer with different doping concentration is grown on the 2-inch n-type 4H-SiC single crystal deviated from the plane 80.The SiH4 is used in the preparation process. C _ 3H _ 8 is used as Si source and C source. High purity N2 and TMA were used as doped N and Al sources and hydrogen as carrier gas. The growth temperature of epitaxial samples was 1580 鈩，

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