Germanium Doped Czochralski Silicon

Abstract

Due to the development of higher integrity electronic devices, it is required to improve the quality of Czochralski (CZ) silicon. On one hand, voids at the near-surface of wafers degrade gate oxide integration (GOI) of MOS devices and therefore reduce the yield of devices. On the other hand, it is a trend for the oxygen concentration of CZ silicon used for ultra large scale integrated circuits (ULSI) to become lower, so it will be difficult to form oxygen precipitates and create gettering sites in the bulk for undesirable metallic contaminants on silicon wafers. In addition, with increasing the diameter of wafers, the dislocations due to higher thermal stress and gravitational stress will generate easily, therefore it is desirable to enhance the mechanical property of wafers. As an important consist for the novel “impurity engineering” for CZ silicon materials (Chen et al., 2010; Chen & Yang, 2009; Yang et al., 2009), the behaviors of germanium in CZ silicon have attracted considerable attention in recent years, which was invented by our group. Compared to normal dopant elements, germanium doping will not induce electrical centers such as shallow thermal donors due to its equivalent electrons with silicon. Furthermore, the solubility of germanium in silicon is so large that germanium doping will not have influence on the growth of CZ silicon, if germanium concentration is lower than 1019 cm-3. And, it is believed that germanium doping in CZ silicon could be much easier to control, so that the influences of germanium doping to the properties of CZ silicon wafers could be adjusted”. Recently, we have investigated the effect of germanium with concentration of 1015-1019 cm-3 on the mechanical stress, the formation of oxygen-related donors, oxygen precipitation and void defects in CZ silicon materials. It has been established that the mechanical strength of silicon wafers could be improved by germanium doping, which benefits the improved production yield of wafers (Chen et al., 2008). It is also found that germanium suppresses thermal donors (TDs) and new donors (NDs), which benefits the stable electrical property of wafers (Cui et al., 2006; Li et al., 2004b). More importantly, germanium has been found to suppress the formation of crystal originated particles (COPs) related to void defects, which can be annihilated easily during high temperature treatments (Chen et al., 2007a; Yang et al., 2002). Meanwhile, the enhancement of oxygen precipitation can be obtained by germanium doping ( Chen et al., 2009; Chen et al., 2006a; Chen et al., 2006b; Li et al., 2004a), and therefore internal gettering (IG) capability could be improved (Chen et al., 2007b; Chen et al., 2007c). Up to now, ascribing to the novel properties induced from germanium atoms, it