| 摘要 |
PURPOSE:To detect signals regarding edges before and behind a mark as mutually separate piece edge signals and to improve the detection precision of the mark position by reducing the diameter of a scanning laser beam and thickening a mark pattern. CONSTITUTION:A mask 1 is almost stacked on a wafer 2; the beam diameter of the scanning laser beam L is denoted as (d) and the scanning-directional width D of an alignment mark M is denoted as D=2d-3d. When the laser beam makes a scan along a laser scanning track l, scattered light with an impulsive waveform appears at two points, i.e. edges (m) and (m') before and behind the alignment mark M. Parts which vary irregularly owing to the interference of the reflected light IR of the wafer 2 are waveform parts at the outside of the alignment mark M, i.e. the leading edge of an output signal Sl and the trailing edge of an output signal Sr. Namely, the leading edge of the output signal S5 and the trailing edge of the output signal Sr are relatively stable because the light intensity of the reflected light Ir is small, so they are used as amrk position detection information. |
