Online Calibration of CD-SEM Magnification Based on Nanolattice Pitch Wafer Standard

In semiconductor manufacturing, the critical dimension scanning electron microscope (CD-SEM) is a high-precision device used for the online measurement of chip feature size. The measurement results directly affect the evaluation of device electrical performance parameters and the judgment of circuit product reliability. However, there is still a lack of special measuring standards and calibration specifications for evaluating the measurement characteristics of CD-SEM. As a result, most calibrators refer to the JJF 1916-2021 Calibration Specification for Scanning Electron Microscopes (SEM) for online measurement of length indication errors in practice. The essence of using the nanolattice pitch standard to calibrate the CD-SEM magnification is to observe the measured image and obtain the pitch result by setting various instrument parameters and multiple pitches under different magnification conditions. Subsequently, the measured pitch result is compared to the certificate value of the standard to determine whether the instrument status is normal and whether the measurement accuracy meets process requirements. In this paper, we discuss an online calibration method of CD-SEM magnification based on the 100 nm nanolattice pitch wafer standard and introduce the measurement principle. We then describe the uncertainty analysis and conformity decision method of results under specific magnification with specific examples. Additionally, we briefly introduce three problems of the calibration process, such as the deterioration of the wafer standard, the noise of the measuring instrument, and contamination caused by an improper operational program. Finally, we summarize corresponding solutions, which have some reference value for future research on the online calibration of integrated circuit nano-parameters measurement equipment.