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法和MO-MBE法在外延Al_2O_3/Si衬底上研究了Si薄膜的异质外延生长。以SiH_4为原料，在1050^ C的生长温度下，用CVD法制备了100 nm的硅薄膜。经RHEED观察，生长膜呈斑点状，包括孪生。利用该结构制备了超薄SOI晶体管，并取得了成功的运行效果。然而，硅薄膜中存在的孪晶结构等缺陷会影响晶体管的性能。另一方面，采用Si_2H_6在较低生长温度750^ C下，在Al_2O_3/Si表面生长了100 nm的MO-MBE薄膜。生长膜的RHEED模式显示出明显的2x1条纹模式。利用离子铣削仪对Si/Al_2O_3/Si结构的性能进行了表征，并观察了异质外延界面周围的结晶度。我们成功地实现了Si/Al_2O_3/Si外延叠加结构。结果表明，在Al_2O_3/Si表面MO-MBE生长Si薄膜对提高薄膜质量非常有效，该技术对实现超薄SOI结构具有重要意义。

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.