State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, People's Republic of China.
Nanotechnology. 2013 May 10;24(18):185302. doi: 10.1088/0957-4484/24/18/185302. Epub 2013 Apr 11.
This paper reports the use of ultrathin free-standing porous alumina membrane (PAM) in pattern transferring for selective epitaxial growth (SEG) of Ge dots and films on Si. PAM, as a large-scale, controllable and lithography-free mask, can transfer nanopatterns onto Si without introducing any contaminants. High-density Ge dots are achievable with Ge adatoms confined in Si pits transferred from PAM. High-quality Ge films can also be grown on Si substrates through SiO2 nano-windows. In this work, 80 and 60 nm pore sizes of PAM were transferred to 70, 50 and 20 nm windows for comparison. For the former two sizes, over-etching of Si beneath every SiO2 window forms epi-seeds to improve intermixing of Ge-Si. No threading dislocations can be observed emanating from the epi-seeds due to the decreased lattice mismatch. An innovative shadow-etching technique utilizing the aspect ratio of PAM further decreased the lateral dimension of patterns from 60 to 20 nm. Cross-sectional transmission electron microscopy images show that the selective epitaxial Ge films grown from a 20 nm-width interface are defect free, which is attributed to the exponential decay of strain energy as well as Ge-Si intermixing.
本文报道了使用超薄独立多孔氧化铝膜（PAM）在选择性外延生长（SEG）中进行图案转移的方法，用于在 Si 上进行 Ge 点和薄膜的图案转移。PAM 作为一种大规模、可控制且无需光刻的掩模，可以在不引入任何污染物的情况下将纳米图案转移到 Si 上。通过从 PAM 转移的 Si 凹坑中限制 Ge 原子，可以实现高密度的 Ge 点。通过 SiO2 纳米窗口，也可以在 Si 衬底上生长高质量的 Ge 薄膜。在这项工作中，分别使用 80nm 和 60nm 孔径的 PAM 转移到 70nm、50nm 和 20nm 的窗口进行比较。对于前两种尺寸，每个 SiO2 窗口下方的 Si 过刻蚀会形成外延种子，以改善 Ge-Si 的混合。由于晶格失配减小，不会观察到源自外延种子的位错。利用 PAM 的纵横比的创新阴影刻蚀技术，进一步将图案的横向尺寸从 60nm 减小到 20nm。横截面透射电子显微镜图像表明，从 20nm 宽度的界面生长的选择性外延 Ge 薄膜无缺陷，这归因于应变能的指数衰减以及 Ge-Si 的混合。
