New Technique to Grow High Quality SOI layer

采用液相外延技术（LPE）进行横向外延生长（ELO），获得了高质量的SOI薄膜。由于LPE是在几乎热平衡的过程中进行的，因此它具有以下三个优点：（1）良好的晶体质量（2）大的横向宽度与垂直厚度之比（ELO比）（3）由于生长表面被小平面覆盖，因此具有高平坦度。对于ELO，衬底限于（111）表面。首先，研究了ELO的生长机理。结果发现，在圆形种子的生长发生在不仅由螺旋位错和取向不良的衬底，但也由二维成核提供的步骤。从线种子的生长被发现几乎发生在由取向不良的衬底提供的步骤，而有时螺旋位错被引入在ELO的外围，其中由于形态不稳定形成二维胞状结构。发现保持尽可能低的过饱和度以防止形态不稳定是重要的。在最佳条件下，ELO比提高到75，并获得了台阶自由端面。ELO层由脊晶种生长而成。它的厚度与山脊的高度相同。因此，ELO厚度可以通过调节脊的高度来控制。0.23生长了μ m厚的层，并且显示ELO厚度可控制到100 nm的量级。最后，用Sirtl腐蚀法对ELO层的晶体质量进行了评价。在低过饱和度下的生长完全消除了位错。结果表明，ELO层具有良好的晶体质量。综上所述，利用LPE横向过生长技术获得了高质量SOI层的新技术。

High quality SOI film was obtained by epitaxial lateral overgrowth (ELO) with LPE. Since LPE is carried out with almost thermally equilibrium process, it has three advantages as follows: (1) Good crystal quality (2) Large ratio of lateral width to vertical thickness (ELO ratio) (3) High flatness because the grown surface is covered with a facet. For ELO, the substrate is limited to the (111) surface. Sn was used as a solvent.First, the growth mechanism of the ELO was studied. It was found that in the circular seeds the growth occurred at steps which were supplied not only by screw dislocations and the misoriented substrate but also by 2D nucleation. Growth from the line seeds was found to occur almost at steps supplied by the misoriented substrate, while sometimes the screw dislocation was introduced at the periphery of the ELO where 2D cellular structure was formed because of the morphological instability. It was found that it is important to keep the supersaturation as low as possible to prevent morphological instability. ELO ratio was improved to 75 and the step free facet was obtained at the optimum condition.Second, the technique to control ELO thickness was developed. ELO layer was grown from a ridge seed. Its thickness was same as the height of the ridge. Therefore, ELO thickness can be controllable by adjusting the height of the ridge. 0.23 um thick layer was grown and ELO thickness was shown to be controllable to the order of 100 nm. With this technique the ELO ratio was improved to 163.Finally, crystal quality of ELO layer was evaluated by Sirtl etching. Dislocations were completely eliminated by the growth at the low supersaturation. This result indicates that the ELO layer has a good crystal quality.In summary, new technique has been developed for obtaining high quality SOI layer by using LPE lateral overgrowth.