生长温度对4HN-SiC同质外延层表面缺陷的影响

Effect of Growth Temperature on Surface Defects of 4HN-SiC Homo-Epitaxial Layers

采用化学气相沉积(CVD)的方法在直径100 mm4°偏角衬底上生长4HN-SiC同质外延片,研究工艺生长温度对外延层表面缺陷的影响,并使用金相显微镜、表面缺陷测试设备、汞探针和红外膜厚仪进行分析和表征。结果表明,工艺生长温度由1 550℃增加到1 620℃,外延层表面的三角形缺陷密度可降低至0.39 cm^(-2);但随着工艺生长温度的增加,导致外延层边缘的台阶聚集数量和长度也急剧增加。在高生长温度下,外延层表面三角缺陷减少以及边缘台阶聚集增加的原因为:一是衬底表面原子迁移率的增加,减少了衬底表面2D生长;二是硅原子的气相成核受到抑制;三是〈1100〉和〈1120〉方向横向生长速率的差异加剧。综上结果,采用1 550℃生长工艺可在高生长速率下制备厚度均匀性和掺杂浓度均匀性分别为1.44%和1.92%的高质量4HN-SiC同质外延片。

4 HN-SiC homoepitaxial wafers were grown on the 4°off-axis substrate with the diameter of 100 mm using the chemical vapor deposition(CVD)method.The effect of the growth temperature on surface defects of the epitaxial layer was investigated.The epitaxial layers were analyzed and characterized by using the metallographic microscope,surface defect test device,mercury-probe and infrared film thickness gauge.The results show that the triangle defect density of the epitaxial layers can be decreased to 0.39 cm-2 by increasing growth temperature from1 550℃to 1 620℃,but the edge step bunching number and length of the epitaxial layers increase obviously with the increase of growth temperature.These results can be attributed to the following aspects:the substrate surface 2 D growth is reduced by increasing of the atom mobility on the substrate surface;the vapor nucleation of silicon atom is restrained;the difference of lateral growth rates increases in〈1100〉and〈1120〉directions.It is found that the high quality 4 HN-SiC homoepitaxial wafers can be prepared by using the high growth rate at 1 550℃,the thickness uniformity and doping concentration uniformity are 1.44%and 1.92%,respectively.