高质量超薄SGOI衬底材料的制备新方法

A new fabrication method of ultra-thin SGOI with high crystal quality

绝缘体上的锗硅(SiGe-On-Insulator,SGOI)材料不仅是高迁移率新型沟道材料应变硅的良好衬底,其本身也是一种极具潜力的高迁移率衬底材料.Ge浓缩是获得高Ge组分、高质量SGOI的最优制备方法之一,传统Ge浓缩工艺在实验中得到改进,在高纯N2气氛中,进行了1000℃的后退火以改善所得SGOI中Ge元素的分布.实验制备了三种后退火条件下的Ge浓缩样品以作对比,并在三种样品上分别外延了20 nm厚的顶层Si以进一步确定所得SGOI材料性能.实验结果发现,三种样品表面平整度并无太大差别,而使用了改进后退火工艺的样品具有最好的Ge组分均匀性和最低的缺陷密度.同时,改进后退火工艺的样品上外延所得顶层硅具有最大的应变值,而Si/SiGe界面处Ge的组分是顶层硅应变度的决定性因素之一.

A modified post-annealing at 1000 ℃ in N2 ambient was carried out to improve the Ge distribution in the SiGe layer fabricated by the Ge condensation process, which is a potential technique for strained Si fabrication. Three kinds of SiGe-on-insulator （SGOI） samples were fabricated by so-called Ge condensation, which was the oxidation of the SiGe layer on an insulator to enhance the Ge fraction. After different post-annealing processes and the necessary cleaning steps, 20-nm-thick strained Si films were epitaxially grown on them. Though the differences of surface topography among the three samples are not great, the one with the modified post-annealing process has the most uniform Ge element distribution and the least misfit dislocations. Meanwhile, the strain values obtained by Raman spectra are coherent with the Ge fraction in SiGe near the Si/SiGe interface and the sample with the modified post-annealing process has a larger strain value than the one with a conventional post-an- nealing.