Differential confocal microscopy for edge contour detection and location

In order to realize high-efficiency and high-accuracy edge contours detection and location for micro structures such as photolithographic mask, a differential confocal microscopy (DCM) for edge contour detection and location is proposed and verified by simulation analysis and experiments. The proposed method has an axial response characteristic of zero-cross step trigger at focal point. Utilizing the step trigger characteristic, the proposed method can realize the real-time sample edge contour imaging in the form of binary image, and greatly improve the efficiency of edge contour detection. Theoretical analysis and computer simulations show that the proposed method can precisely detect and locate the edge contour without being affected by edge shape and direction, and has the ability of suppressing the interference caused by multiplicative and additive noise. Experimental results indicate that period measurement difference of 5 μm-period atomic force microscope standard step between the proposed method and atomic force microscope is only 2 nm. So the proposed method can be used for the real time, precise and rapid industrial edge contour inspection for microstructures.