INTENSITY IMBALANCE CALIBRATION ON AN OVERFILLED BIDIRECTIONAL MARK

摘要

The present disclosure describes various aspects of systems, apparatuses, and methods for correcting the detected positions of alignment targets disposed on a substrale, particularly when a spot size of the light used to detect the alignment targets at least partially overfills each of the alignment targets, such as is the case when the alignment targets include a combined bidirectional (CB) alignment mark. The present disclosure further describes various aspects of systems, apparatuses, and methods for aligning the substrate using the corrected data to ensure accurate exposure of one or more patterns on the substrate. In some aspects, the present disclosure describes a metrology system. The metrology system can include an illumination system configured to generate and direct light to be diffracted from first and second alignment targets. The second alignment target can be oriented differently than the first alignment target. The metrology system can further include a detection system configured to receive first and second diffracted light beams diffracted from respective ones of the first and second alignment targets and to generate a measurement signal therefrom. The measurement signal can include a combined intensity signal including combined intensity values corresponding to the first and second diffracted light beams diffracted from the first and second alignment targets, respectively. The metrology system can further include a controller configured to fit the combined intensity signal using a set of templates to determine a set of weight values. The controller can be further configured to determine, based on the set of templates and the set of weight values, first and second intensity sub-signals including first and second intensity values corresponding to the first and second diffracted light beams. The controller can be further configured to determine first and second intensity imbalance signals based on the first and second intensity sub-signals. The controller can be further configured to determine a set of corrections (e.g., two corrections (X and Y) per color per polarization) to the measurement signal based on the first and second intensity imbalance signals.