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US 4,539,835 AGranted
Calibration apparatus for capacitance height gauges
AssigneeControl Data Corporation
InventorsJohn R. Shambroom, Alan P. Sliski
Life of this patent
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Abstract
In an electron beam lithography apparatus a capacitance height gauge is used to determine the distance between a reticule and electron optics. In order to calibrate the capacitance gauge an optical interferometer, including a mirror are mounted on the same axis as the capacitance gauge. The mirror is moved a predetermined distance so that the movement distance measured by the capacitance gauge and the interferometer can be compared.
Claims11
An apparatus for calibrating a capacitance height gauge having a capacitive sensor, comprising:
- a base;
- a laser interferometer assembly supported by said base;
- an electrically conductive mirror movably supported on said base opposite to said laser assembly;
- a means for supporting said capacitance gauge with said sensor oppositely disposed with respect to said mirror;
- and
- a means for moving said mirror with respect to said laser interferometer, wherein said moving means positions said mirror a desired location from said sensor such that said sensor forms a capacitor with said mirror, and wherein said laser interferometer assembly is utilized to determine the distance between said sensor and said mirror, further comprising a means for obtaining an electrical reading from said capacitor comprised of said sensor and said mirror while said mirror is positioned at said desired location.
3 more elements
Dependencies are inferred from the claim text.