STEP HEIGHT MEASUREMENT USING A SCANNING TUNNELING MICROSCOPE EQUIPPED WITH A CRYSTALLINE LATTICE REFERENCE AND INTERFEROMETER

A crystalline lattice is used as a scale with an atomic pitch which may provide a resolution as high as an x-ray interferometer when the lattice is clearly observed. The scanning tunneling microscope (STM) which uses a lattice reference for correction is more compact than a STM using a correction method which has similar resolution (i.e., interferometry). Step height measurement requires higher resolution than the linewidth measurement in the XY plane. The scheme for the correction in the XY plane requires a two-dimensional lattice image. However, the motion of the probe in the XZ plane for step height measurement does not provide the two-dimensional image needed for the lattice reference correction since the motion in the Z direction is regulated by surface profiling. To ensure the accuracy of displacement, the instrument must be calibrated by an interferometer. We have developed a new scheme for the correction of the Z directional motion using a lattice reference and an instrument designed for the scheme which has a guide mechanism for straightness of motion and is equipped with interferometers for a length standard. The possibility of step measurement using a lattice reference is demonstrated.