LATTICE DEFECTS IN SILICON RAPIDLY SOLIDIFIED FROM THE MELT

为了研究硅在高温下的缺陷行为，我们进行了两种实验。(1)研制了红外线快速加热冷却装置，对FZ-Si小颗粒进行真空熔炼和淬火处理。用透射电子显微镜对淬火后的样品进行了观察。(2)利用专门设计的加热试件夹持器，用高分辨电子显微镜(HRTEM)原位观察了硅的熔化和凝固过程。主要使用氧含量较低的FZ-Si样品，但也对半导体器件工艺中广泛使用的CZ-Si样品进行了测试。结果表明：淬火样品中形成了多种晶格缺陷：{111}微孪晶、非本征类型的{111}层错、层错四面体、60度位错、间隙型位错环和未知的细小缺陷簇。…更多的HRTEM建议将空缺集中在一起。高温HRTEM观察表明，大部分液-固界面成{111}，界面沿界面的一对原子台阶沿界面横向运动，界面温度变化不大。界面运动经常被几个微小的硅酸盐打断，杂质扩散到试件表面。液-固界面附近连续的{111}晶面的剪切运动形成了{111}微孪晶。固液两相之间存在厚度约为1 nm的瞬变层。在高温下观察到许多可能与间隙原子聚集有关的{113}缺陷团簇。实验结果表明，间隙原子和空位都是在硅熔化温度附近的高温下产生的，它们与引入的杂质有关，形成各种晶格缺陷。较少

In order to study defect behaviors of silicon at high temperatures, two kinds of experiments have been performed. (1) A rapid heating and cooling apparatus with infrared rays was prepared, and small FZ-Si particles were vacuum-melted and quenched. The as-quenched specimens were investigated by transmission electron microscopy (TEM). (2) In situ high-resolution transmission electron microscopy (HRTEM) has been carried out to observe melting and solidification of silicon using a specially designed heating specimen holder. FZ-Si specimens with lower oxygen content have been mainly used, but CZ-Si specimens widely used in the semiconductor device technology were also examined in some cases. The results are summarized as follows.A variety of lattice defects were found to be formed in the as-quenched specimens ; {111} micro-twins, extrinsic type {111} stacking faults, stacking fault tetrahedra, 60 degree dislocations, interstitial type dislocation loops and unidentified fine defect clusters. … More HRTEM suggested clustering of vacancies. In situ high temperature HRTEM observations showed most liquid-solid interface planes became {111}, and the interface went forth or back by lateral motion of a pair of atomic steps along the interface with slight temperature change. The interface motion was frequently interrupted by several tiny silicate with impurities diffusing on the specimen surfaces. It was also shown that {111} micro-twins were formed by shear motion of successive {111} planes in the vicinity of liquid-solid interface. Formation of a transient layer with a thickness of about 1 nm is suggested to exist between solid and liquid phases. A number of {113} defect clusters possibly associated with interstitial atom clustering were observed at high temperatures. It is concluded from the present experiments that both interstitial atoms and vacancies are certainly produced at high temperatures near the melting temperature of silicon, and they are correlated with introduced impurities to form various lattice defects. Less