甲烷浓度对金刚石单晶生长的影响和金刚石刻蚀坑的研究

发布时间：2018-05-08 14:56

本文选题：MPCVD + 甲烷浓度　；参考：《吉林大学》2015年硕士论文

【摘要】：微波等离子体化学气相沉积法（MPCVD）制备金刚石，是实现高速率高质量金刚石单晶生长的主要手段。甲烷浓度对金刚石单晶的生长以及结晶质量具有决定性作用。在高速生长的基础上，甲烷浓度的提高引起的变化主要包括： (1)改变等离子体中金刚石相前驱物、非金刚石相前驱物以及H原子的浓度比例。相较其他基团，非金刚石相前驱物C2随甲烷浓度的增加有较大幅度的增加，等离子体内刻蚀作用呈先增大后减小的趋势，使金刚石质量先提高后下降。 (2)提高金刚石的成核率、生长速率,生长模式随之发生改变，致使高甲烷浓度下金刚石的生长速率较高，台阶密度增加，表面形貌变差。 (3)降低N的扩散。单晶的生长过程中，N是由扩散作用进入晶体内。N2通入量不变的情况下，单晶沉积速率的增加使N得相对扩散速率降低，外延层中N含量降低。 H2/O2等离子体可以刻蚀非金刚石相，同时对金刚石相也有一定影响。它对金刚石单晶表面抛光遗留缺陷有很好的祛除作用。本文初步研究H2/O2等离子体刻蚀对单晶表面形貌的影响。通过对四种不同单晶刻蚀情况进行对比，得出： (1)等离子体刻蚀主要对非金刚石相和晶界进行刻蚀，故在缺陷附近的刻蚀坑密度较高。 (2)由于本实验所用HTHP单晶金刚石结晶质量较CVD单晶金刚石差，，相同条件下HTHP单晶表面刻蚀强度比CVD单晶刻蚀强度大。反之，可以通过比较表面刻蚀坑密度大小等来判断金刚石单晶质量的好坏。 (3)由于缺陷种类不同，HTHP单晶表面的刻蚀坑呈平台状，而CVD单晶的刻蚀坑形状不规则，大致呈倒锥形状。 (4)随刻蚀时间的增加，由机械抛光引入缺陷产生的刻蚀坑逐渐消失，而晶体内部缺陷引发的刻蚀坑则不会消失。
[Abstract]:The preparation of diamond by microwave plasma chemical vapor deposition (MPCVD) is the main method to achieve high rate and high quality diamond single crystal growth. Methane concentration plays a decisive role in the growth and quality of diamond single crystals. On the basis of high-speed growth, the changes caused by the increase of methane concentration mainly include: 1) changing the concentration ratio of diamond precursor, non-diamond precursor and H atom in plasma. Compared with other groups, the precursor C2 of non-diamond phase increases greatly with the increase of methane concentration, and the etching effect in plasma increases first and then decreases, which makes the quality of diamond increase first and then decrease. (2) increasing the nucleation rate, growth rate and growth mode of diamond, resulting in higher growth rate, higher step density and worse surface morphology under high methane concentration. 3) reducing the diffusion of N. In the process of single crystal growth, the N content in the epitaxial layer decreases and the relative diffusion rate decreases with the increase of the deposition rate of single crystal. The H2/O2 plasma can etch the non-diamond phase and has some influence on the diamond phase. It has a good effect on removing defects left over by polishing diamond single crystal surface. The effect of H2/O2 plasma etching on the surface morphology of single crystal was studied. By comparing the etching conditions of four different single crystals, it is concluded that: 1) Plasma etching is mainly used to etch non-diamond phase and grain boundary, so the densities of etched pits near defects are high. 2) because the quality of HTHP single crystal diamond is worse than that of CVD single crystal diamond, the etching intensity of HTHP single crystal surface is higher than that of CVD single crystal under the same condition. On the contrary, the quality of diamond single crystal can be judged by comparing the density of etched pits on the surface. (3) the etch pits on the surface of CVD crystals are flat because of the different defect types, while the etched pits of CVD single crystals are irregular in shape and generally in the shape of inverted cones. 4) with the increase of etching time, the etch pits induced by mechanical polishing defects gradually disappear, but the etching pits caused by internal defects do not disappear.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ164.8;O78

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