Capacitors play an essential role in dynamic random-access memory (DRAM) devices. With continuous DRAM device scaling, critical dimension measurements and elemental analysis of capacitor structures becomes more critical. Here, we present an automated TEM metrology and EDS characterization workflow for plan view DRAM capacitors. We utilized a Metrios 6 (Scanning) Transmission Electron Microscope ((S)TEM) equipped with an Ultra-X Energy Dispersive X-Ray Spectroscopy (EDS) detector to obtain high-quality analytical information of DRAM capacitors. The large solid angle of the Ultra-X detector provides approximately 3-4 times more x-ray counts than the previous generation Dual-X detector. Further, we show Ultra-X detector can characterize the elemental composition even on layers as thin as ~1 nm using low electron doses. Additionally, we demonstrate that the extended EDS acquisition induces elemental diffusion and structural alterations, leading to a ~4% reduction in the radius of certain DRAM layers. These findings underscore the importance of controlling the electron dose during imaging to ensure accurate, reliable, and reproducible CD measurements.
Fab metrology and defect inspection workflows have reached an inflection point with the introduction of gate-all-around (GAA) and high aspect ratio memory structures. Few existing inspection and metrology tools can match the sub-surface imaging and analytical capability provided by (Scanning) Transmission Electron Microscopy ((S)TEM). Fully automated (S)TEM workflows are becoming a necessity for the industry to deliver high volume metrology reference data. This atomic scale data must be available with fast turnaround and must also be statistically valid to speed up learning cycles. In this study, we present (S)TEM metrology characterization of advanced GAA and 3D NAND devices by an automated MetriosTM TEM. We introduce an internal machine learning-based modeling algorithm to address the challenges of recognizing GAA devices with process variations and provide faster access to highly accurate TEM reference metrology data. We present automated EDS characterization of beam-sensitive ONO layers, which is a key challenge in 3D NAND device metrology, enabled by a new generation of EDS detector with a high collection efficiency. We also present results on (S)TEM metrology during process monitoring of GAA devices with a higher level of TEM automation.
New materials and designs in complex 3D architectures in logic and memory devices have raised complexity in S/TEM metrology. In this paper, we report about a newly developed, automated, scanning transmission electron microscopy (STEM) based, energy dispersive X-ray spectroscopy (STEM-EDS) metrology method that addresses these challenges. Different methodologies toward repeatable and efficient, automated STEM-EDS metrology with high throughput are presented: we introduce the best known auto-EDS acquisition and quantification methods for robust and reliable metrology and present how electron exposure dose impacts the EDS metrology reproducibility, either due to poor signalto-noise ratio (SNR) at low dose or due to sample modifications at high dose conditions. Finally, we discuss the limitations of the STEM-EDS metrology technique and propose strategies to optimize the process both in terms of throughput and metrology reliability.
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