Abstract In this paper, the authors report their successful attempt to acquire the scanning nonlinear dielectric microscopy (SNDM) signals around the floating gate and channel structures of the 3D Flash memory device, utilizing the custom-built SNDM tool with a super-sharp diamond tip. The report includes details of the SNDM measurement and process involved in sample preparation. With the super-sharp diamond tips with radius of less than 5 nm to achieve the supreme spatial resolution, the authors successfully obtained the SNDM signals of floating gate in high contrast to the background in the selected areas. They deduced the minimum spatial resolution and seized a clear evidence that the diffusion length differences of the n-type impurity among the channels are less than 21 nm. Thus, they concluded that SNDM is one of the most powerful analytical techniques to evaluate the carrier distribution in the superfine three dimensionally structured memory devices.

Abstract The transistor structure of memory devices and other cutting-edge semiconductor devices has become extremely minute and complicated owing primarily to advances in process technology and employment of three-dimensional structures. Among the various approaches to improve the device performance and functionality, optimizing the carrier distribution is considered to be quite effective. This study focuses on scanning nonlinear dielectric microscopy (SNDM), a capacitance-based scanning probe microscopy technique. First, to evaluate SNDM's potential for high-resolution measurement, the most commonly used metal coated tip with a tip radius of 25 nm was used to measure a quite low-density impurity distribution. Then, after confirming that the SNDM's S/N ratio was sufficiently high for the smaller probe tip, an ultra-fine diamond probe tip with a nominal tip radius of lesser than 5nm as an SNDM probe tip to measure sub-20 nm node flash memory cell transistors was employed. Successful results were obtained and are reported.