Design and control of an optical alignment system using a parallel XXY stage and four CCDs for micro pattern alignment

Recently, as the requirements of manufacture or inspection of semiconductor, MEMS, LED, LCD, touch panel and so on, vision servo and multi-Degree-of-Freedoms (DOF) alignment/compensation stage are integrated for high precise alignment. The general alignment method uses two CCDs to capture the image of the pattern, and the central positions of the pattern on the CCD are determined using computer, DSP or microprocessor etc. In this paper, the proposed system includes four CCDs, two alignment objects and a novel design three-DOF parallel stage. The alignment displacements represented δ_x, δ_y and δ_Θ are analyzed using forward kinematic analysis. A novel design three-DOF parallel stage called XXY stage uses to move the alignment displacement. Experiment results show that resolution of the used CCD is about 7 μm per pixel and the linear and angular positioning repeatability of the XXY stage are better than 1 μm and 20 arcsec. Alignment error is about ±1 pixel. Time of three times alignment is about 1.25 second.