Self-Focusing SIMS Enables Quantitative Dopant Analysis in Nanoscale Silicon Devices beyond Conventional Spatial Resolution Limits

Abstract

The continuous downscaling of semiconductor devices has created a pressing need for analytical methodologies capable of enabling process control in confined volumes and sub-100 nm features. Conventional secondary ion mass spectrometry (SIMS), while highly sensitive, lacks the spatial resolution required for such applications. Nevertheless, SIMS remains a powerful tool for the analysis of small features through the self-focusing (SF) SIMS concept, which exploits the formation of cluster ions that inherently localize chemical information within the region of interest. In this study, SF-SIMS is applied to the quantification of boron in patterned samples composed of boron-doped silicon fins with widths ranging from 500 to 20 nm, embedded in boron-doped silicon oxide. By selecting cluster ions that originate exclusively from the silicon fin region, the spatial resolution limitations of conventional SIMS are overcome without compromising the sensitivity. Using this approach, a boron implant with a peak concentration of ∼9 × 1020 at/cm3 was measured in the widest fins (500 nm), in good agreement with SRIM simulations and conventional SIMS methods, while a concentration of ∼4.5 × 1020 at/cm3 was obtained for the narrowest fins (20 nm). This study establishes SF-SIMS as a reliable, rapid, and preparation-free approach for dopant quantification in nanoscale semiconductor devices down to 20 nm.