Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Reexamination Certificate
2006-01-10
2006-01-10
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
C356S400000, C355S053000
Reexamination Certificate
active
06984836
ABSTRACT:
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 that monitors wafer surface height relative to the projection optics as well as at least one backplane gauge that monitors wafer position relative to a backplane. The system also includes a filter that translates time-domain measurements of off-axis wafer surface gauge and the backplane gauge into space-domain measurements. A coordinate transformer 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 to determine correction data is also included together with a delay line for storing the correction data until the wafer has moved a predetermined distance.
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Copy of International Search Report for International Application No. PCT/US 00/40635, filed Aug. 15, 2000.
Allen Stephone B.
ASML Holding N.V.
Sterne Kessler Goldstein & Fox P.L.L.C.
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