Rapid Thermal Transition Metal Single Crystal Silicon In Behavior Research

Transitional metals are the most important impurities in silicon. Therefore, it is important to study the behavior of these metals in crystalline silicon. Rapid thermal process (RTP) has emerged as a key manufacturing technique for the fabrication of integrated circuits on silicon. Knowledge of the influence of RTP on the behavior of metallic impurities seems greatly needed. This can not only enrich the "defect engineering" from the science point, but also benefit the internal gettering technique form the engineering view. In this paper, important transitional metals copper and nickel have been studied, and the main results are listed below.1. The effect of copper and nickel contamination on the MDZ and conventional DZ in Cz silicon wafers has been investigated by optical microscopy. After DZ formation, no matter by means of RTP or by conventional internal gettering (IG) processes, copper and nickel contamination has no effect on the DZ and can be gettered by the bulk microdefects (BMDs). Otherwise, in silicon wafers with copper and nickel contaminated initially, the MDZ could not form and many precipitates occurred in the near-surface of the sample. Based on the facts, it is suggested that it's very important to avoid the metals impurity before the formation of MDZ.2. We have investigated the impact of copper and nickel on oxygen precipitation during IG process in Cz silicon by means of FTIR. It was found that in Cz silicon interstitial copper almost had no effect on oxygen precipitation but copper precipitation remarkably enhanced oxygen precipitation; however; interstitial nickel or nickel precipitation all had no effect on oxygen precipitation. These results suggest that copper precipitation acted as the heterogeneous nucleation sites of oxygen precipitation and enhanced the oxygen precipitation, whereas nickel precipitation fitted well with the silicon matrix and had no effect on the oxygen precipitation nucleation.3. The electrical property of nickel in Fz silicon during RTP was studied. It was found that a small amount of nickel existed on the substitutional sites and was electrically active, which can introduce an acceptor level in n type Fz Si. And an obvious pn junction formed near the surface of the silicon. Otherwise, the different point defects induced by RTP during different ambient had an obvious effect on the distributing of Nis, which leaded to a different formation of pn junction. Furthermore, it was found Nis in silicon was stable.4. The recombination activity of copper in different ambient during RTP in n-type silicon and p-type silicon has been investigated. It was found by studies of minority carrier lifetime that the ambient during RTP had an obvious effect on the Cu recombination activity. In N2 ambient, Cu had the strongest effect on minority carrier lifetime in both n-type silicon and p-type silicon above copper in-diffusion temperature 800°C. It is suggested that vacancies induced by nitridation during RTP enhanced the Cu precipitation in silicon, which caused a significant drop in the minority carrier lifetime. It was also found that copper has a stronger effect on minority carrier lifetime in n-type silicon than in p-type silicon. The lifetime decreased monotonically with increasing Cu in-diffusion temperature in n-type silicon and exhibited a step-like behavior in p-type silicon at copper in-diffusion temperature above 800 °C. This result provides a confirmation of the electrostatic model of Cu precipitation in silicon.