Extraction and Analysis of Interface States in 50-nm nand Flash Devices

A method to extract the interface states (Nit) located in the center area (center Nit) and the Nit located in the corner region (corner Nit) of NAND Flash devices is presented in this paper. This Nit extraction method is based on a careful combination of charge-pumping current data, technology computer-aided-design simulation results, and the “control gate (CG)-modulated corner effect,” where “CG-modulated corner effect” refers to the fact that the electron density in the corner region of the transistor is greatly affected by the bias applied to CG. Using this Nit extraction method, the amounts of center Nit and corner Nit of a given NAND Flash device can be analyzed. In addition, among devices with various widths of active area, the narrower width device showing worse corner Nit can be demonstrated. Furthermore, the generation of center Nit and corner Nit for a device under program/erase cycle stress is explored. Our Nit extraction method will be useful to analyze not only the characteristics of fresh NAND Flash devices but also the reliability of aged NAND Flash devices.