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US 2011/0238365 A1Published application
Diffraction Based Overlay Linearity Testing
AssigneeNanometrics Incorporated
InventorsJie Li, Zhuan Liu, Silvio J. Rabello, Nigel P. Smith
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Abstract
An empirical diffraction based overlay (eDBO) measurement of an overlay error is produced using diffraction signals from a plurality of diffraction based alignment pads from an alignment target. The linearity of the overlay error is tested using the same diffraction signals or a different set of diffraction signals from diffraction based alignment pads. Wavelengths that do not have a linear response to overlay error may be excluded from the measurement error.
Claims16
A method comprising:
- illuminating a target with incident radiation, the target having a plurality of diffraction based alignment pads;
- detecting signals diffracted from each of the plurality of diffraction based alignment pads after the incident radiation interacts with the plurality of diffraction based alignment pads;
- testing a linearity of an overlay error using the signals;
- and
- determining an empirical diffraction based overlay measurement of the overlay error using the signals.
2 more elements
An apparatus for comprising:
- a radiation source that produces radiation to be incident on a plurality of diffraction based overlay alignment pads of a target;
- a detector that detects signals diffracted from the plurality of diffraction based overlay alignment pads after the radiation interacts with the plurality of diffraction based overlay alignment pads;
- and
- a computer coupled to receive the signals detected by the detector;
- and
- a computer-usable medium having computer-readable program code embodied therein for causing the computer to perform acts of:
- testing a linearity of an overlay error using the signals;
- and
- determining an empirical diffraction based overlay measurement of the overlay error of the target using the signals.
6 more elements
Dependencies are inferred from the claim text.