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US 4,686,531 AGranted
Capacitance height gage applied in reticle position detection system for electron beam lithography apparatus
AssigneeControl Data Corporation
InventorsJohn R. Shambroom, Alan P. Sliski
Life of this patent
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Abstract
A capacitance height gage for positioning the reticle of an electron beam lithography apparatus. The gage includes a hybrid circuit substrate carrying four measuring and two reference capacitor circuits. Each has a driven plate, the four measuring plates disposed opposite the object surface to be measured, and the two reference plates disposed on the top of the substrate. Two ground plates are disposed a predetermine distance from the reference driven plates. The object surface comprises the ground plate for the four measuring driven plates. The reference plates calibrate the measuring plates.
Claims12
A capacitance height gage for detecting the position of an object surface, comprised of:
- a hybrid substrate supported proximately to said object surface;
- a reference capacitor circuit supported on said substrate, said circuit including a reference capacitor having capacitor plates separated by a nominal distance, said reference capacitor having a capacitance, said reference capacitance circuitry generating a reference capacitance signal representative of said capacitance of said reference capacitor;
- a signal source circuit providing a driving signal;
- said driving signal being controlled by said reference capacitor signal;
- said reference capacitor circuit being driven by said driving signal;
- a measuring capacitor circuit supported on said substrate, said measuring capacitor circuit including a sensor plate supported on said substrate opposite to said object surface, said sensor plate and said object surface comprising a measuring capacitor whereby the capacitance of said measuring capacitor varies as the separation between said sensor plate and said object surface varies, said measuring capacitor circuitry generating a measuring capacitor signal representative of said capacitance of said measuring capacitor, said measuring capacitor circuit being driven by said driving signal;
- means for comparing said measuring capacitor signal with a reference signal, including means for generating a measurement signal representative of said comparison, said measurement signal representing the deviation in plate separation of said sensor plate and said object surface of said measuring capacitor from said nominal distance;
- said reference caacitor plates and said measuring capacitor sensor plate and said object surface being separated by a dielectric, said dielectric being comprised of the measuring environment in which said hybrid substrate is located whereby said dielectric of said reference capacitor changes in the same respects as said dielectric of said measuring capacitor as said measuring environment varies;
- and
- a plurality of sensor plates driven by said driving signal and disposed on the bottom of said substrate opposite to said object surface said sensor plates and said object surface comprising a plurality of measuring capacitors, each of said measuring capacitors having an associated measuring capacitor circuit for generating a measuring capacitor signal for each measuring capacitor, said comparing means comparing each of said measuring capacitor signals with said reference signal to generate a measurement signal for each of said measuring capacitors, said measuring signal representing the deviation in plate separation of each of said measuring capacitors from said nominal distance.
7 more elements
A capacitance height gage for detecting the position of an object surface, comprised of:
- a hybrid substrate supported proximately to said object surface;
- at least one reference capacitor circuit supported on said substrate, said circuit including a reference capacitor having capacitor plates separated by a nominal distance, said reference capacitor having a capacitance, said reference capacitance circuitry generating a reference capacitance signal representative of said capacitance of said reference capacitor;
- a signal source circuit providing a driving signal;
- said driving signal being controlled by said reference capacitor signal;
- said reference capacitor circuit being driven by said driving signal;
- a measuring capacitor circuit supported on said substrate, said measuring capacitor circuit including a sensor plate supported on said substrate opposite to said object surface, said sensor plate and said object surface comprising a measuring capacitor whereby the capacitance of said measuring capacitor varies as the separation between said sensor plate and said object surface varies, said measuring capacitor circuitry generating a measuring capacitor signal representative of said capacitance of said measuring capacitor, said measuring capacitor circuit being driven by said driving signal;
- means for comparing said measuring capacitor signal with a reference signal, including means for generating a measurement signal representative of said comparison, said measurement signal representing the deviation in plate separation of said sensor plate and said object surface of said measuring capacitor from said nominal distance;
- said reference capacitor plates and said measuring capacitor sensor plate and said object surface being separated by a dielectric, said dielectric being comprised of the measuring environment in which said hybrid substrate is loacted whereby said dielectric of said reference capacitor changes in the same respects as said dielectric of said measuring capacitor as said measuring environment varies;
- and
- means for heating said substrate and for maintaining said substrate at a selected temperature greater than the ambient temperature of the measuring environment.
7 more elements
A capacitance height gage comprising means for providing a plurality of alternating current signals half of which are out of phase with the other half;
- a plurality of measuring plates mounted on a surface, each one driven by one of said alternating current signals to thereby induce a net zero current in an object surface adjacent the measuring plates;
- and means responsive to the capacitance of the measuring plates for determining the distance of the object surface from the measuring plates.
Dependencies are inferred from the claim text.