Impact of hydrogen plasma treatment on fluorine-contained silicon nitride films

It has been suggested that the trap energy level in silicon nitride (SiN) films becomes shallow due to hydrogen and fluorine incorporation, which causes a charge migration in the MONOS memory cells and deteriorates the data retention characteristics. To solve these issues, we have proposed the hydrogen plasma treatment and demonstrated the reduction of the shallow trap density consequent to the removal of hydrogen from SiN films. In this study, the hydrogen plasma treatment is applied to the fluorine-contained SiN films. The results show that deepening of the trap energy level contributing to hole current, decreasing of the shallow trap density contributing to charging and the fluorine concentration near at the SiN surface. These results are regarded to be due to the removal of fluorine in the SiN film through the reaction with hydrogen radicals (H*) during the hydrogen plasma treatment.