Profiling of carriers in a 3D flash memory cell with nanometer-level resolution using scanning nonlinear dielectric microscopy

This work used scanning nonlinear dielectric microscopy to profile the distributions of carriers in channels and floating gate structures less than 10 nm in size within a three dimensional flash memory cell. An exceptionally sharp diamond probe tip (having a radius of less than 5 nm) was employed so as to obtain extremely high spatial resolution, and this technique was found to provide high contrast images of floating gates. The minimum spatial resolution obtainable from this apparatus was determined to be less than 1.9 nm. In addition, the present study demonstrated that variations in the diffusion lengths of N-type impurities between channels were less than 21 nm. The present study establishes an extremely helpful means of optimizing the performance and failure analysis of flash memory cells and similar devices.