Advanced spectroscopic methods for probing in-gap defect states in amorphous SiNx

High-k dielectric materials and silicon nitride (SiNx) with large bandgap are increasingly utilized in various memory devices. Specifically, non-volatile NAND flash memory devices employ charge trap states to distinguish between 0 and 1. Despite abundant previous research, our comprehension of the exact nature of these defects, such as their energy positions within the gap, remains unsatisfactory. Here, we present a refined experimental methodology to elucidate the in-gap defect states and the band gaps in amorphous SiNx thin films. Our approach integrates high-resolution reflection electron energy loss spectroscopy (REELS) and spectroscopic ellipsometry (SE) for comprehensive analysis. We investigated two different SiNx films prepared by plasma-enhanced chemical vapor deposition and sputtering. Our analysis revealed several distinct in-gap states and determined band gap energies. This approach not only provide advanced spectroscopic methods to characterize the defect electronic states in SiNx, but also applicable to other large band gap semiconductors or dielectrics to predict device-level characteristics for future devices. [1]