| Summary: | 博士 === 長庚大學 === 電子工程學研究所 === 96 === The influence of interface segregation on dopant distribution near the silicon surface is very important for shallow junction and silicon-on-insulator (SOI) devices. This dissertation focuses on the phosphorus dose loss induced by the interface segregation. Modeling of phosphorus segregation at the interface was established based on results of experiments and simulation. Because dose loss is controlled by transient enhanced diffusion during low-temperature annealing, samples were cycled between additional implantation of Si+ and annealing at 800°C to study the kinetic associated with phosphorus trapping at the interface. The maximum percentage dose loss decreases as the dose of implanted phosphorus increases. The influence of arsenic background doping on the phosphorus dose loss was also investigated.
The balance of phosphorus trapping and detrapping at the interface was investigated by samples implanted by phosphorus at doses of 21013 and 71013 cm-2 during isothermal annealing at high temperatures. Phosphorus is lost at the beginning of annealing and then partially recovered in silicon. For samples implanted at 71013 cm-2, two recovery stages of trapped phosphorus reveals two interface segregation mechanisms. For samples implanted at 21013 cm-2, only a slow recovery was observed. The slow recovery can be simulated by using the conventional interface trap model. This dissertation proposes an interface clustering model for the fast dose recovery with a nearly constant surface concentration in samples implanted at 71013 cm-2. The interface clustering model assumes clustering reactions between phosphorus atoms at the interface. The conventional interface trap model considers phosphorus trapping by individual interface defects. By combining the proposed interface clustering model into the conventional interface trap model, the transient phosphorus loss can be simulated successfully. Detrapping experiments were performed at different annealing temperatures to extract the segregation energy of each segregation model. The segregation energy of the interface trap model is much higher than that of the interface clustering model.
Finally, phosphorus dose loss in a SOI structure was investigated. In this experiment, the saturation of phosphorus dose loss was monitored by the sheet resistance during annealing of 900oC. The two Si/SiO2 interfaces of the SOI structure do not show evident difference in phosphorus segregation.
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