The use of the atomic force microscope (AFM) for step height and pitch measurements in industrial applications is rapidly increasing. To compare the results obtained by different instruments and to achieve high accuracy, the scales of an AFM must be calibrated. Perhaps the most convenient and most appropriate method is the use of a calibration standard. In order to calibrate AFM standards using an AFM, we have built the calibrated AFM (C-AFM). The new setup is shown in Fig. 1. It has metrology traceable to the wavelength of light for all three axes. After several improvements of the design and the calibration procedure, we estimate the combined standard uncertainty to be ((2.1 nm)^2 + (0.06%)^2)^(1/2) for pitch and ((0.23 nm)^2 + (1.06%)^2)^(1/2) for step height measurements. To demonstrate the performance of the C-AFM, step height (from 8 nm to 180 nm) and pitch measurements (from 200 nm to 20 mm) on commercially available calibration artifacts were taken. After optimizing the measurement procedure, the results of the step height measurement showed an excellent repeatability and agreed well with the values obtained by stylus measurements. In addition, we are measuring single atomic steps of the Si(111) surface to investigate the possibility of using such samples as step height standards in the subnanometer range. The C-AFM measurements of pitch on several samples have been compared with a metrology optical microscope system at NIST, and the observed agreement was well within the combined standard uncertainties.
Proceedings Title: Proceedings of 2nd Seminar on Quantitative Microscopy, , PTB Report F-30, K. Hasche, W. Mirande, and G. Wilkening, Editors
Conference Location: PTB Braunschweig, GE
Pub Type: Conferences
metrology, pitch, scanning force microscope, step height