| 摘要 |
PURPOSE: An alignment sensor is provided to improve alignment in wafers and reticle, regardless of treatment variables. CONSTITUTION: The alignment sensor includes a stationary reference grating for receiving electromagnetic radiation from a coherent light source and a movable wafer grating. Two beams separated from the light source is provided by a beam splitter. One beam is directed toward the stationary reference grating to collect the diffraction order, and the other beam from the beam splitter is directed toward a movable wafer grating. The collected diffraction order from the movable wafer grating is collected and made to interfere with the diffraction order of the stationary reference grating, to cause a phase shift for indicating movement or non-alignment of the wafer. Regardless of the variables for wafer treatment, multi-channel having individual wavelength or color is used for optimizing the detection and alignment.
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