Overlay error detection

A method for detecting misalignment of two structures placed next to each other with respect to a reference plane, comprising:

• providing a beam of radiation to illuminate a portion of each of the two structures;
• collecting radiation from the illuminated portion of each of the two structures and directing the collected radiation from each structure to a corresponding detector through a corresponding one of two apertures;
• determining a misalignment between the structures from outputs of the detectors;
• and
• causing relative motion between the apertures and detectors on one hand and the two structures on the other, or between the beam on one hand and the two structures on the other.

An imaging apparatus for detecting misalignment of two periodic structures placed next to each other with respect to a reference plane, comprising:

• a source providing a beam of radiation illuminating the two periodic structures along directions that are substantially normal or near normal to the reference plane;
• an array of detectors;
• optics collecting radiation from the two structures and directing the collected radiation to form images of at least portions of the two structures on the array of detectors which provide outputs, wherein the image of the portion(s) of one of the two structures is substantially distinct from the image of the portion(s) of the remaining one of the two structures;
• and
• a processor determining a misalignment between the structures from a phase difference between the outputs of the detectors.

An apparatus for detecting misalignment of two structures placed next to each other with respect to a reference plane, comprising:

• a source providing a beam of radiation to illuminate a portion of each of the two structures;
• one or more detectors;
• two apertures;
• optics collecting radiation from the illuminated portion of each of the two structures and directing the collected radiation from each structure to a corresponding detector through a corresponding one of the two apertures, causing the corresponding detector to provide an output;
• a processor determining a misalignment between the structures from output(s) of the detector(s);
• and
• an instrument causing relative motion between the apertures and detectors on one hand and the two structures on the other, or between the beam on one hand and the two structures on the other.

An imaging apparatus for detecting misalignment of two structures on two different planes and placed next to each other with respect to a reference plane, comprising:

• a source providing a beam of radiation illuminating the two structures;
• a detector array with one or more detectors;
• optics collecting radiation from the two structures and directing the collected radiation to form images of at least portions of the two structures on the detector array, wherein the one or more detectors provide outputs, and the two structures are at different distances from said optics, said optics having a numerical aperture in the range of about 0.1 to 0.9, wherein the image of the portion(s) of one of the two structures is substantially distinct from the image of the portion(s) of the remaining one of the two structures;
• and
• a processor determining a misalignment between the structures from outputs of the detectors without requiring more than a single measurement using said optics.

An imaging method for detecting misalignment of two structures on two different planes and placed next to each other with respect to a reference plane, comprising:

• providing a beam of radiation illuminating the two structures;
• providing a detector array with one or more detectors;
• using optics to collect radiation from the two structures and direct the collected radiation to form images of at least portions of the two structures on the detector array, wherein the one or more detectors provide outputs, and the optics is at different distances from the two structures, said optics having a numerical aperture in the range of about 0.1 to 0.9, wherein the image of the portion(s) of one of the two structures is substantially distinct from the image of the portion(s) of the remaining one of the two structures;
• and
• determining a misalignment between the structures from outputs of the detectors without requiring more than a single measurement using said optics.

An imaging apparatus for detecting misalignment of two structures placed next to each other with respect to a reference plane, comprising:

• a source providing a beam of radiation illuminating the two structures;
• one or more detectors having an integration time less than 10 milliseconds;
• optics collecting radiation from the two structures and directing the collected radiation to form images of at least portions of the two structures on the one or more detectors which provide outputs, wherein the image of the portion(s) of one of the two structures is substantially distinct from the image of the portion(s) of the remaining one of the two structures;
• and
• a processor determining a misalignment between the structures from outputs of the detectors.

An imaging apparatus for detecting misalignment of two structures placed next to each other with respect to a reference plane, comprising:

• a source providing pulses of radiation illuminating the two structures, wherein at least one of the pulses has a pulse width less than 10 milliseconds;
• one or more detectors;
• optics collecting radiation from the two structures and directing the collected radiation to form images of at least portions of the two structures on the one or more detectors which provide outputs, wherein the image of the portion(s) of one of the two structures is substantially distinct from the image of the portion(s) of the remaining one of the two structures;
• and
• a processor determining a misalignment between the structures from outputs of the detectors.

An imaging apparatus for detecting misalignment of two structures placed next to each other with respect to a reference plane, comprising:

• a source providing pulses of radiation illuminating the two structures, wherein at least one of the pulses has a pulse width less than 10 milliseconds;
• one or more detectors;
• optics collecting radiation from the two structures and directing the collected radiation to the one or more detectors which provide outputs;
• and
• a processor determining a misalignment between the structures from outputs of the detectors, said source comprising a mechanical shutter with aperture time of less than about 10 milliseconds.

An integrated processing and imaging apparatus for processing a sample having two structures on two different planes, comprising:

• (a) an imaging system for detecting misalignment of the two structures placed next to each other with respect to a reference plane, said system comprising:
• a source providing a beam of radiation illuminating the two structures;
• optics collecting radiation from the two structures and directing the collected radiation to one or more detectors of a detector array to form images of at least portions of the two structures on the detectors, which provide outputs, wherein the image of the portion(s) of one of the two structures is substantially distinct from the image of the portion(s) of the remaining one of the two structures, wherein the optics is at different distances from the two structures;
• and
• a processor determining a misalignment between the structures from outputs of the detectors, wherein said optics has a numerical aperture such that said misalignment is determinable without performing more than a single measurement using said optics;
• and
• (b) a processing system processing said sample, said processing system responsive to the misalignment for adjusting a processing parameter.

An imaging method for detecting misalignment of two periodic structures placed next to each other with respect to a reference plane, comprising:

• providing radiation to illuminate the two periodic structures;
• imaging radiation from the two structures on an array of detectors to form an image of at least portions of each of the two structures on the array, causing the detectors to convert images of said portions to signal outputs, wherein the image of the portion(s) of one of the two structures is substantially distinct from the image of the portion(s) of the remaining one of the two structures;
• and
• determining a misalignment between the structures by comparing said image of portion(s) of one of the two structures, or an image derived therefrom, to said image of portion(s) of the other one of the two structures, or an image derived therefrom, in signal outputs of the detectors.

An imaging apparatus for detecting misalignment of two periodic structures placed next to each other with respect to a reference plane, comprising:

• a source providing radiation illuminating the two periodic structures;
• an array of detectors;
• optics imaging radiation from the two structures on an array of detectors to form an image of at least portions of the two structures on the array, causing the detectors to convert images of said portions to signal outputs, wherein the image of the portion(s) of one of the two structures is substantially distinct from the image of the portion(s) of the remaining one of the two structures;
• and
• a processor determining a misalignment between the structures by comparing said image of portion(s) of one of the two structures, or an image derived therefrom, to said image of portion(s) of the other one of the two structures, or an image derived therefrom, in signal outputs of the detectors.

An imaging method for detecting misalignment of two periodic structures placed next to each other with respect to a reference plane, comprising:

• providing radiation to illuminate the two periodic structures;
• imaging radiation from the two structures on an array of detectors to form an image of at least portions of each of the two structures on the array, causing the detectors to convert images of said portions to signal outputs, wherein the image of the portion(s) of one of the two structures is substantially distinct from the image of the portion(s) of the remaining one of the two structures;
• and
• determining a misalignment between the structures by comparing information in said image of portion(s) of one of the two structures to information in said image of portion(s) of the other one of the two structures in signal outputs of the detectors without requiring any interference effects.

An imaging apparatus for detecting misalignment of two periodic structures placed next to each other with respect to a reference plane, comprising:

• a source providing radiation illuminating the two periodic structures;
• an array of detectors;
• optics imaging radiation from the two structures on an array of detectors to form an image of at least portions of the two structures on the array, causing the detectors to convert images of said portions to signal outputs, wherein the image of the portion(s) of one of the two structures is substantially distinct from the image of the portion(s) of the remaining one of the two structures;
• and
• a processor determining a misalignment between the structures by comparing information in said image of portion(s) of one of the two structures to information in said image of portion(s) of the other one of the two structures in signal outputs of the detectors without requiring any interference effects.