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，采用化学气相沉积(CVD)和分子束外延(MO-MBE)方法在外延的Al_2O_3/Si衬底上异质外延生长了Si薄膜。采用化学气相沉积(CVD)方法，以SiH_4为衬底，在1050ﾟC的温度下，异质外延生长了10 0 nm的Si薄膜，RHEED观察表明，所生长的薄膜具有孪晶结构。在此结构上制作了超薄SOI晶体管，并成功地进行了工作。然而，研究发现，硅膜中的孪晶结构等缺陷会对晶体管特性产生影响。另一方面，在较低的生长温度(750ﾟC)下，用Si2H6在Al_2O_3/Si衬底上进行了分子束外延生长Si薄膜(100 Nm)，生长的薄膜具有明显的2×1条纹。利用离子球磨机对Si/Al_2O_3/Si结构进行了横截面分析，观察了异质外延界面附近的结晶度。我们已经成功地实现了外延堆积的Si/Al_2O_3/Si结构，结果表明，在Al_2O_3/Si上用分子束外延生长Si薄膜对提高薄膜质量是非常有效的，该技术对于实现超薄SOI结构是有吸引力的。

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.