The Application Research of Focus Probe Technique for Edge Detection and Linewidth Measurement of Microsteps

The edge detection of micro/nano-scaled microstructures is difficult to achieve by conventional microscopes due to the sensitivity to the property of measured surface and the effect of diffraction limit. This thesispresents a new technique by using a blue-ray DVD pick-up head as the focus sensor in association with a nanopositioning stage. The measurement method of edge detection is based on the principle of total reflection energy. This new method, the total reflection energy will be maximal when the substrate surface is on the focus point of the probe. It will be gradually reduced when the focused beam scans across the edge. From the theoretical analysis, the edge position is found right on the centerline of the focused beam and this position can be directly detected by the nanopositioning stage to the resolution of 1 nm. Using linear curve characteristic, the value of step-height can be calculated. Experimental results show that the uncertainty of measured edge position, and linewidth are all within ±35 nm (±2σ). The proposed technique is simple in principle and easy to setup. This technique can overcome the conventional diffraction limit of optical microscope and is possible for in-situ measurement.