Effect of nanoclusters induced by Si implantation on total dose radiation response of a SOI wafer
Si ion implantation with subsequent annealing was used to improve the irradiation hardness of SOI wafers. The reduced negative shifts in the threshold voltage of the n-channel transistors showed that the total dose radiation hardness was remarkably enhanced by this modification process, and the pseudo-MOS method was used to test the Id–VG characteristics of the SOI samples before and after irradiation. Photoluminescence (PL) spectra demonstrated that Si nanoclusters were formed during annealing in the buried oxide of the implanted samples, which were possibly the main candidates for charge compensation. X-ray photoelectron spectroscopy (XPS) results also suggested that reduction of the threshold voltage shifts was accompanied with the formation of Si nanoclusters near the peak of the implants. Furthermore, the effect of positive charge buildup can be partly reduced as a result of the improvement on proton trapping in the bulk of the oxide due to the implantation induced nanoclusters.