X-ray Diffraction Study of the Formation Process of SiO_2/Si Interfaces

迄今为止，人们对二氧化硅进行了大量的研究，但氧化过程尚不清楚。例如，热氧化的逐层生长是前所未有的现象之一。SIMOX晶圆片是SOI（绝缘体上硅）衬底之一，有望用于低功耗和高速器件。然而，埋藏氧化层的形成过程尚不清楚。本文利用x射线衍射技术研究了SiO_2与Si晶体界面的形成过程。研究了氧注入硅在热退火过程中外延有序Si0_2的生长。在退火初期观察到额外的衍射条纹。这意味着小析出物本身相对于硅层具有2x2对称的有序结构。进一步退火后，随着析出相尺寸的增大，额外条纹的强度逐渐增大。这表明有序析出物发生了外延生长，特别是在横向上，因为有序结构在横向上比在垂直方向上具有更好的周期性。在垂直方向上埋藏氧化层的形成主要是由于聚结而不是外延生长。还发现Si（113）上的热氧化层不是简单的非晶结构，而是与Si衬底呈外延关系的有序结构，与Si（001）和Si（111）衬底上的结构相似。

A lot of studies for the silicon dioxide have been carried out so far, but the oxidation process is not clear. For example, a layer-by-layer growth of the thermal oxidation is one of unprecedented phenomena. A SIMOX (seperatiorr-hy-implanted oxygen) wafer is one of the SOI (silicon-on-insulator) substrate, which is expected for low-power and high-speed devices. However, the formation process of the buried oxide layer is obscure. In this study we studied the formation process of the interface between the SiO_2 and Si crystals by X-ray diffraction technique.The growth of epitaxially ordered Si0_2 in oxygen-implanted silicon during thermal annealing was investigated. The extra diffraction streak was observed at the initial stage of annealing. This means that the small precipitate itself has the ordered structure of 2x2 symmetry with respect to the Si layers. As the size of the precipitates became larger upon further annealing, the intensity of the extra streak gradually increased. This indicates that epitaxial growth of the ordered precipitates occurred, particulary, in the lateral direction because the ordered structure has better periodicity in the lateral direction than in the perpendicular direction. The formation of the buried oxide layer in the perpendicular direction was due mainly to coalescence rather than to epitaxial growth.It was also found that the thermal oxide layer on Si(113) did not simple amorphous structure, but has the ordered sturucture with an epitaxial relation with the Si substrate, which was similar to those on the Si(001) and (111) substrates.