Accurate topographic images using a measuring atomic force microscope

A real-time measuring atomic force microscope AFM.equipped with a high-resolution three-axis laser interferometer has been constructed. A three-sided mirror as a sample holder is placed on a three-dimensional 3D. scanner which was designed for axis-independent scanning. The mirror is scanned so that the cantilever traces the surface form. The traces of the mirror are monitored along the XrYrZ-axis independently and simultaneously by the laser interferometers and fed back to the X–Y servo-scan and Z-height control. Each interferometer unit has a four-pass optical arrangement and homodyne detection system. After the digital signal processing of the four-phase output phase-shifted by 908.from the detectors, the signal is introduced into a fringe counter, which has an electrical phase resolution of 2048. A final system resolution of 0.04 nm lr16 384.has been realized. Topographic images of a standard sample of a precisely etched grid pattern pitch and height. were taken with an without interferometric calibration. Piezo distortions along the X–Y plane caused by hysteresis or creep were almost eliminated. q1999 Elsevier Science B.V. All rights reserved.