In-line SIMS: A Key Tool for Characterizing Epitaxy Processes in Nanosheet Device Fabrication
By Yaguang Zhu, Li Xiang, Daniel Lewellyn, Sarah Okada, Paul Isbester, Stefan Schoeche, Katherine Sieg, Daniel Schmidt, Mohsen Nasseri, Shogo Mochizuki, and Marinus Hopstaken
Secondary-Ion Mass Spectrometry (SIMS) is a critical analytical technique for characterizing thin films, dopant concentrations, implants and trace elements. Nanosheet gate-all-around transistors, particularly those using SiGe epitaxy in their construction, rely heavily on precise control of Ge concentration, interface abruptness, and dopant profiles. However, variations in local deposition and diffusion conditions, especially within 3D device structures pose challenges to process control. High-temperature processes can also induce elemental diffusion, impacting device performance.
This paper presents a successful lab-to-fab transition of SIMS, with Statistical Process Control (SPC) based on in-line SIMS data. In-line SIMS offers advantages over traditional lab-based SIMS, including automated handling, high throughput, and compatibility with small area measurements on product wafers. These features enable fast turn-around times, reduced scrap, increased yield, and the ability to continue processing measured wafers within the manufacturing line.
In this work, we demonstrate the utility of in-line SIMS in several production scenarios, including monitoring epitaxy tool stability on monitor wafers, characterizing Ge diffusion in multi-layer stacks during high-temperature annealing, and measuring implant and dopant profiles on both blanket and patterned wafers. Furthermore, we discuss the application of in-line SIMS to characterize S/D epitaxy in a fully integrated nanosheet gate-all-around transistor architecture, comparing results with off-line SIMS and alternative methods.
Overall, this study showcases the benefits of in-line SIMS for real-time process monitoring and control in semiconductor device manufacturing, highlighting its potential to enhance device performance and yield.
BIOGRAPHY
Sarah Okada has worked in leadership roles in the semiconductor industry for over 25 years focusing on
product management, marketing, and technical sales of substrate and device manufacturing
equipment. Ms. Okada started in the semiconductor industry in 1995 in the applications development
group at Strasbaugh, a supplier of CMP and grinding equipment. In 2013, she was promoted to director
of sales and marketing for Strasbaugh where she incorporated marketing and sales best practices to
develop a new brand for Strasbaugh and launched a successful new grinding product. Ms. Okada was
key in the acquisition of Strasbaugh’s technology for Revasum in 2016, where she served as VP of
marketing and product management and launched the industry’s first fully automated SiC substrate
polisher. Since joining Nova in November 2020, Ms. Okada has been leading work on the SIMS-based
METRION platform as Product Marketing Director. Ms. Okada holds a bachelor’s degree in Marketing
and Finance from the University of Oregon.