Formation of Ultra-Thin Hetero-Epitaxial SOI Structure and Its Application to Thin Film Transistors.

为了实现超薄SOI晶体管，采用CVD和MO-MBE方法在外延Al_2O_3/Si衬底上异质外延生长Si薄膜。用CVD法在1050 ℃下用SiH_4进行了Si薄膜（100 nm）的异质外延生长。通过RHEED观察，生长的膜显示出包括孪晶的斑点图案。在此结构上制作了超薄SOI晶体管，并成功运行。然而，发现晶体管特性受Si膜中的缺陷如孪晶结构的影响。另一方面，在Al_2O_3/Si衬底上，用Si_2H_6在较低的生长温度（750 ℃）下进行了Si薄膜（100 nm）的MO-MBE生长。生长膜的RHEED图案指示尖锐的2x 1条纹图案。利用离子束刻蚀装置对Si/Al_2O_3/Si结构进行了截面TEM分析，观察了异质外延界面附近的结晶情况。我们已经成功地实现了Si/Al_2O_3/Si外延叠层结构，从这些结果可以看出，在Al_2O_3/Si上MO-MBE生长Si薄膜对于改善薄膜质量是非常有效的，这种技术对于实现超薄SOI结构是很有吸引力的。

In order to realize ultra thin SOI transistor, heteroepitaxial growth of Si thin film on epitaxial Al_2O_3/Si substrate was investigated by CVD and MO-MBE method. Hetero-epitaxial growth of Si thin film (100 nm) by CVD method was carried out using SiH_4 at growth temperature of 1050^ﾟC. The grown film indicated spot pattern including twin by RHEED observation. The ultra thin SOI transistors were fabricated on this structure and successful operation was confirmed. However it was found that the transistor characteristics were affected by defect in Si film such as twin structure. On the other hand, MO-MBE growth of Si thin film (100 nm) on Al_2O_3/Si was carried out using Si_2H_6 at lower growth temperature of 750^ﾟC. The RHEED pattern of grown film indicated sharp 2x1 streak pattern. The property of the Si/Al_2O_3/Si structure was evaluated by cross-sectional TEM technique using ion milling apparatus, and the crystallinity around hetero-epitaxial interface was observed. We have successfully realized the epitaxially stacked Si/Al_2O_3/Si structure.From these results, it was found that MO-MBE growth of Si thin film on Al_2O_3/Si was greatly effective for improving film quality, and this technique was attractive for the realization of ultra thin SOI structure.