Effects Of Rapid Thermal Annealing On Germanium-doped Czochralski Silicon

The ever-smaller feature size of integrated circuit imposes on increasingly stringent requirements on the defect control and internal gettering (IG) capability of Czochralski (CZ) silicon wafers. For the larger diameter CZ silicon wafers, the oxygen concentration is reduced to a certain extent. Moreover, the thermal budget for the manufacturing of contemporary IC featuring super-shallow junction is significantly lowered. The two regards as mentioned above are not favorable for oxygen precipitation and therefore the internal gettering (IG) capability for CZ silicon wafers so that the traditional IG process is challenged. On the other hand, the larger diameter CZ silicon wafers imposes on increasingly requirements on the mechanical properties. Under the circumstance, the germanium-doped CZ (GCZ) silicon has been gotten more attention due to its novel properties. At the same time, IG process based on the vacancy introduced by rapid thermal annealing (RTA) also gets more attentions. But until now, there are few investigation in the effect of RTA on the GCZ silicon, and the mechanism for the effect of vacancies on oxygen precipitation in GCZ silicon needs to be further studied.In this dissertation, the minority carrier lifetime and the oxygen precipitation behavior in germanium doped CZ silicon. Moreover, the mechanisms for the effect of germanium and vacancy on oxygen precipitation have reasonably exploited. Furthermore, the effect of RTA pretreatment on the IG process in GCZ silicon wafers has been discussed. Listed below are the most important results achieved in this work.(1) The effect of RTA on the minority carrier lifetime in GCZ silicon has been investigated. It is found the minority carrier lifetime in GCZ silicon is strongly reduced by RTA treatment, and with increasing temperature, the minority carrier lifetime reduced quickly. This indicates that this reduction is due to crystal defects and the strong light radialization induced during the RTA step.(2) The effect of vacancies introduced by RTA on the oxygen precipitation in GCZ silicon has been investigated. It is observed that the RTA-induced vacancies in GCZ silicon enhanced the nucleation for oxygen precipitation most significantly at 750 to 850℃. The oxygen precipitation in silicon is enhanced by both the vacancies introduced during RTA pretreatment and the doping of germanium. Especially, we find that the enhancement effect of vacancies on the precipitation of oxygen is larger than that of germanium atoms. Moreover, it is found that oxygen precipitation could be enhanced when the nucleating temperature is between 650 and 750℃or higher than 1050℃. Oxygen precipitation is suppressed when the nucleating temperature is in the range from 850 to 950℃. We suggest that these phenomena have relation to the reaction between germanium atoms and vacancy complexes. The mechanism for the interaction between vacancies and germanium atoms in CZ silicon is elucidated.(3) The influences of the RTA pretreatment on the IG ability in GCZ silicon have been investigated. It is found that there are high density of bulk micro-defects (BMDs) and the appropriate width of DZ zone when the RTA temperature is higher than 1200℃. When RTA under N2 ambient, the vacancies can injected to the wafer bulk from surface, so the DZ zone could not create beneath the surface.(4) The IG processes for extension heavy germanium-doping (HGCZ) silicon wafer based on the conventional furnace anneal (CFA) and rapid thermal anneal (RTA) have been developed. It is found that the oxygen precipitation in HGCZ silicon would be delayed after the annealing 800℃/4h+1000℃/16h with RTA pretreatment. When the "delay effect" disappears, one-step RTA can enhance the oxygen precipitation strongly.