Method and apparatus for inspection and metrology
AssigneeASML Netherlands B.V.
InventorSietse Thijmen Van Der Post
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Abstract
A method and apparatus for optical metrology is disclosed. There is disclosed, for example, a method involving a radiation intensity distribution for a target measured using an optical component at a gap from the target, the method including calculating a correction factor for the variation of radiation intensity of the radiation intensity distribution as a function of variation of the distance of the gap.
Claims20
A method involving a radiation intensity distribution for a target measured using an optical component at a gap from the target, the method comprising:
- calculating a correction factor for the variation of radiation intensity of the radiation intensity distribution as a function of variation of the distance of the gap, the correction factor configured to correct a measured radiation intensity distribution after it has been measured and/or to correct a radiation intensity distribution that is calculated.
A method, comprising:
- for a given target structure, calculating a second-order derivative tensor for dependence of radiation intensity on a gap between the target structure and an optical element;
- determining a statistical variance of a gap variation distribution over a measurement period;
- and
- determining a variation in radiation intensity for the target structure based on the statistical variance and the second-order derivative tensor.
A method comprising:
- for a given target structure, calculating a second-order derivative tensor for dependence of radiation intensity on a gap between the target structure and an optical element;
- evaluating statistical variance of a gap variation distribution for a measurement period of the target structure, the gap variation distribution being based on a measured gap signal;
- and
- evaluating a mean radiation intensity variation across a pupil as a function of variation of the gap based on the second-order derivative tensor and the statistical variance of the gap variation distribution.
A non-transitory computer program product comprising machine-readable instructions for causing a processor to cause performance of a method involving a radiation intensity distribution for a target measured using an optical component at a gap from the target, the method comprising calculating a correction factor for the variation of radiation intensity of the radiation intensity distribution as a function of variation of the distance of the gap, the correction factor configured to correct a measured radiation intensity distribution after it has been measured and/or to correct a radiation intensity distribution that is calculated.
Dependencies are inferred from the claim text.