| 摘要 |
<p>A system for monitoring wafer surface topography during a lithographic process is described that includes projection optics that illuminate a portion of the wafer surface. The system further includes at least one off-axis wafer surface gauge (502) that monitors wafer surface height relative to the projection optics as well as at least one backplane gauge (503) that monitors wafer position relative to a backplane (121). The system also includes a filter (505, 506) that translates time-domain measurements of off-axis wafer surface gauge (502) and the backplane gauge (503) into space-domain measurements. A coordinate transformer (510) is included that transforms the space-domain measurements into a single coordinate system. A computational element that combines the space-domain measurements with a focus set-point (516) to determine correction data is also included together with a delay line (516) for storing the correction data until the wafer has moved a predetermined distance.</p> |
