The radiation hardness of the nitrogen-fluorine implanted buried oxide layer in silicon-on-insulator materials against higher total dose irradiation

Abstract

Nitrogen (N) and fluorine (F) ions were sequentially implanted into the buried oxide (BOX) to improve the total dose radiation hardness of the BOX layer in silicon-oninsulator (SOI) materials. The radiation response of the BOX layers modified by the ion implantation was characterized by flat-band voltage shifts and trapped charge changes in the BOX, based on the capacitance-voltage (C-V) measurements on the polysilicon-BOX-semiconductor (PBS) structures fabricated on the SOI materials, before and after irradiation using Co-60 γ rays with various doses range from 0.7 to 1.7 Mrad(Si). The experimental results show that a considerably enhanced hardness for the BOX layer can be achieved by this co-implantation of nitrogen and fluorine on proper process conditions, and the radiation responses of the BOX layers are directly associated with the anneal times after nitrogen implantation. In particular, the rebound and fluctuation phenomena of the BOX radiation response were observed with increasing dose, according to the changes in the flat-band voltages, which cannot be explained in terms of the increase in radiation induced interface state density, and the related mechanisms were analyzed and discussed.