高剂量离子注入形成的非晶层重新结晶过程中杂质外扩散的物理模型

本文提出了一个杂质沉淀引起位错生成、位错-杂质相互作用、杂质原子沿晶粒间界快速扩散的模型,用以解释高剂量离子注入形成的非晶层在重新结晶的退火过程中杂质外扩散和缺陷运动现象。给出了在位错的合应力场的影响下杂质的扩散方程。以能量为80keV,剂量为10¹⁶cm^-2的Pb⁺注入Si(111)面为例,对扩散方程进行了数学物理处理,从而给出了根据实验测量推演表观扩散系数随时间变化及位错的合应力场对杂质的作用力的纵向分布的方法。实验测得的位错合应力场对杂质的作用系数α≈8.4×10^-28dyn·cm³,退火时间在5×10³sec至8.25×10³sec内,表观扩散系数D随时间的变化为一指数关系。 关键词：

IMPURITY OUT-DIFFUSION MODEL IN RECRYSTALLIZATION OF AMORPHOUS LAYER DUE TO HIGH DOSE ION IMPLANTATION

A model of impurity precipitate-dislocation generation, impurity atom-dislocation interaction and impurities rapid diffusion along grain boundaries has been used to explain the out-diffusion behaviour of implanted impurities and defect movement in the amorphous layers due to high dose ion implantation during reerystallization annealing. Taking the resultant stress effect of the dislocations in to account, the diffusion equation of impurities has been established. By using Pb⁺ ions with energy of 80 keV implanted in (111) silicon to the dose of 10¹⁶cm^-2 as an example, a mathematical and physical treatment of the diffusion equation has been carried out. Thereby a method of deducing the apparent diffusion coefficient varying with time and the longitudinal profile of the force exerted by the resultant stress of dislocations on the impurities according to the experimental measurements has been proposed. The measured constant of interaction between dislocations and impurities, α, is α≈8.4×10^-28dyn·cm³, and the time variation of the apparent diffusion coefficient D in a time interval can be expressed as a exponential function.