CD-SEM calibration with TEM to reduce CD measurement error

In this paper, we will describe why the calibration process between CD-SEM and transmission electron microscopy (TEM) was performed. TEM is considered to be a unique solution such that we could obtain CD and sidewall angle accurately. TEM has the merit of having good resolution, but the measurement is performed over small segments of device features. The CD measurement error related to line edge roughness (LER) was also investigated in order to avoid the degradation in the accuracy of TEM measurement of CD. Many efforts were performed to reduce the uncertainty in TEM measurement of CD. The amount of the uncertainty related to TEM CD measurement was approximately 5nm. We could obtain the linear relationship between CD-SEM and TEM measurements of CD of logic gate lines ranging from 0.12 mum to 0.20 mum. The average CD measured using TEM was 15nm lower than the CD measured with CD-SEM at poly silicon etched profile which had the sidewall angle of 86*. Such difference is unacceptable in the CD measurement. The CD measurement error could be compensated with the modification of the measurement algorithms. The reproducibility of CD measurement for various algorithms was also investigated. It was shown that TEM measurement of CD could be applicable for the calibration with CD-SEM measurement to control various processes with different sidewall angles.