Abstract
This report discusses subjects and countermeasures in order to apply the stripe pattern projection technique to the automatic focusing equipment used in microscopes. The effects of wafer circuit patterns, wafer defocus and illumination system on the detected signal wave of the projected stripe pattern are analyzed. A technique to minimize the detection error of the stripe pattern contrast by eliminating the influence of the circuit pattern on the stripe pattern image is described. Also, an illumination technique to secure a uniform stripe pattern image and a detection technique to improve contrast detection accuracy are discussed. Using these techniques, a repeatability of ± 0.6μm (3σ) and an accuracy of ±1.0μm (3σ) in automatic focusing have been achieved.
