Advanced spectroscopic methods for probing in-gap defect states in amorphous SiNx for charge trap memory applications

Silicon nitride (SiN x ) serves as the charge trap layer in current 3D NAND flash memory devices. The precise formation mechanism and electronic structure of localized defect trap states in SiN x remain elusive. Here, we present a refined experimental methodology to elucidate the in-gap defect states and the band gaps in amorphous SiN x thin films. Our approach integrates high-resolution reflection electron energy loss spectroscopy (REELS) and spectroscopic ellipsometry (SE) for comprehensive analysis. By systematical analysis, we aim to provide a robust method for determining in-gap electronic states in SiN x . We investigated two different SiN x 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 SiN x , but also applicable to other large band gap semiconductors or dielectrics to predict device-level characteristics for future devices. • We investigated the band gaps and in-gap defect states of amorphous SiN x using two spectroscopic methods. • REELS revealed the band gaps and in-gap defect states near the conduction band. • Spectroscopic ellipsometry precisely detected the small in-gap defect states. • Our methods provide guidance for device-level characteristics of charge trap memory.