Comparing bottom–up and top–down SI traceability approaches in dimensional nanometrology: reference material measurements using transmission electron microscopy and atomic force microscopy

Abstract The lattice spacing of Si has recently been established as the mise en pratique (MeP) of the SI definition of the metre. These developments may influence the dimensional nanometrology, particularly when implemented in the measurements of semiconductor devices through transmission electron microscopy (TEM). Unlike the conventional top–down approach to SI traceability, which relies on optical interferometry using calibrated laser frequencies, the bottom–up approach uses the Si lattice spacing within the measurement object itself to achieve accurate scaling. To determine the Si lattice spacing as the MeP, studies have validated its equivalence to the conventional top–down approach, specifically metrological atomic force microscopy (AFM), through comparative experiments, revealing no notable mismatches. However, the destructive nature of TEM sample preparation poses a critical limitation. Previous studies were unable to investigate the effect of the sample preparation process on the Si lattice spacing, leading to concerns regarding potential sources of uncertainty that could compromise the reliability of the bottom–up approach in practical applications. To address this challenge, we fabricated a reference material sample via a nondestructive process. This approach enables the evaluation of the effect of TEM sample preparation on Si lattice spacing, facilitating robust assessment of the reliability of the bottom–up approach. Furthermore, a direct comparison between the bottom–up (TEM) and top–down (metrological AFM) approaches was conducted. The results demonstrated the feasibility of the proposed approach. In particular, when comparing the measurement results for dot–dot sidewall distances obtained by the two approaches, an absolute relative difference of 0.02 % was observed on average, with a maximum of 1.08 % and a minimum of 0.14 %. The comparative measurement technique proposed in this study, which is based on nondestructive TEM sample preparation, is a fundamental evaluation technique. This technique strengthens the reliability of the bottom–up approach and extends the applicability of Si lattice spacing as the MeP of the SI definition of the metre.