Calibration of high magnification in the measurement of critical dimension by AFM and SEM

Abstract

In the measurement of critical dimension (CD) by scanning electron microscopy (SEM) and atomic force microscopy (AFM), the measured linewidths of the CD patterns are different from the real values due to the edge effect of secondary electrons and the radius and half cone angle of the tips for AFM. In order to solve this problem, a certified reference material (CRM) with a series of CD lines having different linewidth from 20 nm to 60 nm was designed to calibrate the magnification. The linewidths of the CRM could be traceably certified by high resolution scanning transmission electron microscope from the lattice constant of Si(1 1 1) plane in the Si(1 0 0) substrate. As a result, the magnification of AFM and SEM can be calibrated from the certified linewidths of the CRM. The magnification correction factors of AFM and SEM showed the relative standard uncertainties of 1.3% and 0.9%, respectively. The linewidths of the CD lines in the target samples can be traceably determined from the calibrated magnification after calibrating the instruments using the CRM and a calibration program.