Electrical and reliability improvement in polyoxide by fluorine implantation

We show that the incorporation of fluorine into the oxide grown on polysilicon (polyoxide) not only improves the electrical characteristics (i.e., lower leakage current, higher electrical breakdown field), but also improves the reliability (lower electron trapping rate, larger Qbd). This improvement is believed to be due to the stress relaxation of the polyoxide and smoother polysilicon/polyoxide interface by the fluorine incorporation. The optimum fluorine dose (2× 1014) shows the best characteristics such as Ebd over 12 MVcm and Qbd ∼2 C cm2. However, excessive fluorination (1× 1015) seems to result in performance degradation due to the generation of nonbridging oxygen centers.