Direct charge measurements to read back stored data in nonvolatile memory devices using scanning capacitance microscopy

This paper describes a methodology for reading back electrical charges from nonvolatile memory (NVM)-based flash devices. These devices were programmed to store charges in the floating gates of the transistors. The primary goal is to identify and read back these static charges in the form of logic levels of “1 bit (1b)” and “0 bit (0b)” without destroying the data. Scanning capacitance microscopy (SCM) with ∼15 nm spatial resolution was used to directly probe the data stored in the floating gate transistors. SCM measures the on-site programmed charges in flash memory devices as transistor charges of ON/OFF or 1b/0b. Qualitative variation of charge carriers has also been observed. Both the sample preparation and SCM probing methods are also discussed. An application has been demonstrated on a Texas Instruments based microcontroller unit with embedded 512 KB nor flash devices.