APPLICATION OF NEAR-FIELD OPTICS TO CRITICAL DIMENSION METROLOGY

Scanned-probe microscopes often have difficulty measuring absolute len gths due to nonlinearities in the piezo elements used to scan the tip. We have developed a method which allows for calibrated scanning of a near-field optical aperture. This method allows for point-by-paint cor rection for piezo nonlinearities such as hysteresis and creep by imagi ng the light emanating from a near-field probe onto a position sensiti ve detector. We have used this principle to fabricate a microscope wit h 20 nm accuracy in tip position. With further improvements, we believ e single nanometer accuracy is possible. (C) 1997 American Institute o f Physics.