Micro Defects In Heavily Phosphorus-doped Czochralski Silicon

The heavily doped Czochralski (Cz) silicon could not only eliminate the "latch-up" effect of small feature size CMOS devices, but also effectively reduces the energy loss, therefore is extensively applied as a substrate material of epitaxial silicon wafers. Oxygen precipitates and voids are prominent microdefects in Czochralski (Cz) silicon, which have a significant impact on the yield of device manufacture therefore great efforts have been paid on them. Heavily phosphorus (P)-doped Cz silicon is technologically important for epitaxial silicon wafers. However, up to now, few investigations on oxygen precipitation (OP) and microdefects in heavily P-doped Cz silicon have been reported. In this paper, the oxygen precipitation behaviour, the elimination of the void defects and the oxygen diffusivity in the heavily P-doped CZ silicon are systematically discussed. The results are shown as follows:(1) Study on the oxygen precipitiation bahaviour and the effect of Ge co-doping. The Result shows that the oxygen precipitation could nucleate effetively in the heavily P-doped CZ silicon at the temperature of 650℃,800℃and 900℃, and most remarkable at the temperature of 650℃. Besides,the Ge co-doping at level of 1020cm"3 supress the OP but increase the size of OP in the heavily P-doped CZ silicon. The reason could be the overhigh level co-doping of Ge which results in the overcompensation of lattice stress.(2) Study on the rapid thermal annealing (RTA) and the OP formation on the annihilation of the voids. The results indicates that RTA at temperature of 1200℃and higher can signally and rapidly annihilate the voids defects in the heavliy P-doped CZ silcion in Ar, O2 and N2 atomsphere. And the RTA at 1200℃/90s in Ar atomsphere is an optimized condition for the annihilation of voids. Moreover, it was found that the significant OP resulting from the two-step anneal of 650℃/8 h+1000℃/16 h could also cause the substantial annihilation of voids in heavily P-doped Cz silicon. The study also shows that the Ge co-doping at the level of 1020cm"3 surpress the annihilation of the voids in the heavily P-doped CZ silcon.(3) Study on the oxygen out-diffusion behaviour in the heavily P-doped CZ silicon by Secondary Ion Mass Spectroscope (SIMS) at temperature range from 800℃to 1200℃. The results shows that the oxygen diffusion is significantly surpressed in the heavliy P-doped CZ silicon compared with the lightly P-doped CZ silicon. And the Ge co-doping plays a promotive role on oxygen diffusion at temperatures lower than 1000℃but plays a surpessive role at 1000℃and higher. Finally,the formula of oxygen diffusivity at temperature range from 800℃to 1200℃appropriate for the heavily P-doped CZ silicon is presented.