Height Measurement Using High-Precision Atomic Force Microscope Scanner Combined with Laser Interferometers

概要

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We have developed a high-precision atomic force microscope (AFM) for measuring fine pattern structures for semiconductor process evaluation. Three-axis ultrahigh-resolution displacement sensors using modularized laser interferometers were built into an AFM scanner combined with piezoactuators, elastic parallel-plate structures and an on-axis optical microscope. A newly designed symmetrical layout of the optical path of homodyne interferometers and a digital signal processor (DSP) enabled highly stable measurements of the mechanical displacements of the tip of an AFM scanner. As a result of their ultrafine positioning capabilities, a resolution of the displacement sensors of 0.05 nm was achieved. The periodic error of laser waves was compensated by employing DSP-based processing. Thus, a wide linearity range from 0.1 to 1000 nm was demonstrated and a one-sigma repeatability of 0.25 nm was obtained by measuring reference samples of 50 and 1000 nm step heights. Finally, micro-roughness with a 0.1 nm height, a GaAs atomic step with a 0.3 nm height, patterns with high aspect ratios, and resist patterns were clearly observed using an interferometer displacement signal.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2006-11-15