Lithographic apparatus, device manufacturing methods, and computer-readable storage medium
AssigneeASML Netherlands BVV.
InventorsAndre Jeunink, Frank Commissaris, Vera Lemmen
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Abstract
The change in a property of a lithographic apparatus, in a preferred embodiment the change in magnification of the projection system due to lens heating effects, is predicted and when the change since the last time an alignment process was performed is greater than a threshold, an additional alignment process is carried out. A realignment is triggered when the predictive correction, and hence the error in it, becomes larger than a desired maximum. This avoids unnecessary realignments but ensures that an alignment does occur when likely errors are out of permitted ranges.
Claims18
A lithographic projection apparatus comprising:
- an illuminator configured to provide a projection beam of radiation;
- a support configured to hold a patterning device, the patterning device configured to pattern the projection beam according to a desired pattern;
- a substrate table configured to hold a substrate;
- a projection system configured to project the patterned beam onto a target portion of the substrate;
- an alignment system;
- a predictive control system configured to generate a control signal to effect a compensation for a time-varying property of a part of said apparatus;
- and
- a comparator configured to compare said control signal to a threshold and generate a trigger signal when said control signal is greater than said threshold,
- wherein said alignment system is configured to perform an alignment process in response to said trigger signal.
A device manufacturing method using a lithographic projection apparatus, the method comprising:
- providing a substrate that is at least partially covered by a layer of radiation-sensitive material;
- providing a projection beam of radiation using an illuminator;
- using a patterning device to endow the projection beam with a pattern in its cross-section;
- projecting the patterned beam of radiation onto a target portion of the layer of radiation-sensitive material using a projection system;
- predicting a value of a time-varying property of a part of said apparatus at the time of a particular exposure;
- applying a compensatory adjustment on the basis of said predicted value during said particular exposure;
- detecting when said predicted value exceeds a threshold;
- and
- in response to a detection that said predicted value exceeds said threshold, carrying out an alignment process.
A computer-readable storage medium having stored thereon a computer program executable in the control system of a lithographic projection apparatus, said computer program comprising instructions to perform:
- predicting a value of a time-varying property of a part of said apparatus at the time of a particular exposure;
- applying a compensatory adjustment on the basis of said predicted value during said particular exposure;
- detecting when said predicted value exceeds a threshold;
- and
- in response to a detection that said predicted value exceeds said threshold, carrying out an alignment process.
A lithographic projection apparatus comprising:
- an illuminator configured to provide a projection beam of radiation;
- a support configured to hold a patterning device, the patterning device configured to pattern the projection beam according to a desired pattern;
- a substrate table configured to hold a substrate;
- a projection system having a magnification configured to project the patterned beam onto a target portion of the substrate;
- an alignment system configured to align a substrate held on said substrate table;
- a predictive control system configured to generate a control signal to effect a compensation for change in said magnification of said projection system due to heating of elements thereof;
- and
- a comparator configured to compare the change in said control signal since the last time an alignment process was performed to a threshold and generate a trigger signal when said change in said control signal is greater than said threshold,
- wherein said alignment system is configured to perform an alignment process in response to said trigger signal.
A lithographic projection apparatus comprising:
- an illuminator for providing a projection beam of radiation;
- a support for holding a patterning device, the patterning device serving to pattern the projection beam according to a desired pattern;
- a substrate table for holding a substrate;
- a projection system for projecting the patterned beam onto a target portion of the substrate;
- an alignment system for aligning a substrate held on said substrate table;
- means for generating a control signal to effect a compensation for a time-varying property of a part of said apparatus;
- and
- means for comparing said control signal to a threshold and generating a trigger signal when said control signal is greater than said threshold,
- wherein said alignment system is configured to perform an alignment process in response to said trigger signal.
Dependencies are inferred from the claim text.