STEM/EDS Metrology and Statistical Analysis of 3D NAND Devices

Abstract

Process monitoring of 3D NAND flash memory devices requires critical dimension analysis at multiple heights in the memory cell channel. In the punch and plug process the etching step of the cell channel is vulnerable to deformities especially as the aspect ratio of the channel increases. Automated STEM metrology is used as a fast and accurate method of analysis to determine the channel area, circularity, and position. EDS metrology provides the dielectric layer widths of the cell, compensating for the low contrast of these layers in standard STEM imaging. Automation of the STEM image acquisition, EDS, and metrology enabled large data sets to be acquired for analysis. The results of the analysis reveal how the channel shrinks and morphs as the depth of the channel increases.