硅基锗薄膜选区外延生长研究

Selective area growth of Ge film on Si

利用超高真空化学气相沉积系统,基于低温Ge缓冲层和选区外延技术,在Si/Si O2图形衬底上选择性外延生长Ge薄膜.采用X射线衍射、扫描电镜、原子力显微镜、拉曼散射光谱等表征了其晶体质量和应变等参数随图形尺寸的变化规律.测试结果显示,位错密度随着图形衬底外延窗口的尺寸减小而减少,Ge层中的张应变随窗口尺寸的增大先增大而后趋于稳定.其原因是选区外延Ge在图形边界形成了(113)面,减小了材料系统的应变能,而单位体积应变能随窗口尺寸的增加而减少;选区外延厚度为380 nm的Ge薄膜X射线衍射曲线半高宽为678′′,表面粗糙度为0.2 nm,表明选区生长的Ge材料具有良好的晶体质量,有望应用于Si基光电集成.

According to low temperature Ge buffer layer and selective area epitaxy technology, we selectively grow Ge film on patterned Si/SiO2 substrate using ultra-high vacuum chemical vapor deposition. By using X-ray diffraction （XRD）, scanning electron microscope, atomic force microscopy and Raman scattering spectrum, we obtain its crystal quality and the laws of stress and other parameters varying with shape size. The results show that threading dislocation density decreases with shape size decreasing. Moreover, the tensile strain of Ge layer first increases and then turns stable with the increase of shape size, which can be attributed to the formation of （113） facet during Ge selective area growth. The formation of （113） facet reduces the strain energy of epitaxial material system, and the reduction of strain energy per unit volume decreases with increasing the shape size. The root-mean-square surface roughness of the Ge epilayer with a thickness of 380 nm is about 0.2 nm, the full-width-at-half maximum of the Ge peak of the XRD profile is about 678″. It is indicated that the selective area epitaxial Ge layer is of good quality and will be a promising material for Si-based optoelectronic integration.