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US 12,066,322 B2Granted
Single grab overlay measurement of tall targets
AssigneeKLA Corporation
InventorsAmnon Manassen, Andrew V. Hill, Yonatan Vaknin, Avner Safrani
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Abstract
An overlay metrology system may include an objective lens, illumination optics to illuminate an overlay target including a first grating with a first pitch on a first sample layer and a second grating with a second pitch on a second sample layer, where the first and second sample layers are separated by a layer separation distance greater than a depth of field of the objective lens. The system may further include collection optics with a radially-varying defocus distribution to compensate for the layer separation distance such that the first and second gratings are simultaneously in focus on the detector.
Claims40
An overlay metrology system, comprising:
- an objective lens;
- one or more illumination optics configured to direct illumination from an illumination source to an overlay target on a sample through the objective lens when implementing a metrology recipe, wherein the overlay target in accordance with the metrology recipe includes a first grating with a first pitch on a first sample layer and a second grating with a second pitch on a second sample layer, wherein the second pitch is smaller than the first pitch, wherein the first and second sample layers are separated by a layer separation distance greater than a depth of field of the objective lens;
- a detector;
- and
- one or more collection optics configured to direct at least a portion of light collected by the objective lens to the detector, wherein the metrology recipe provides that diffraction orders of the illumination by the first grating collected by the objective lens are positioned below a threshold radius in a pupil plane and diffraction orders of the illumination by the second grating collected by the objective lens are positioned above the threshold radius in the pupil plane, wherein the one or more collection optics provide a radially-varying defocus distribution to compensate for the layer separation distance, wherein the first and second gratings are simultaneously in focus on the detector;
- and
- a controller including one or more processors configured to execute program instructions causing the one or more processors to execute the metrology recipe by:
- receiving one or more images of the overlay target from the detector in which the first and second gratings are simultaneously in focus on the detector;
- and
- determining an overlay measurement between the first and second layers of the sample based on the one or more images.
7 more elements
An overlay metrology system, comprising:
- a controller communicatively coupled to an overlay metrology sub-system, the controller including one or more processors configured to execute program instructions causing the one or more processors to execute a metrology recipe by:
- receiving one or more images of an overlay target from a detector of the overlay metrology sub-system in which the first and second gratings are simultaneously in focus on the detector, wherein the overlay metrology sub-system comprises:
- an objective lens;
- one or more illumination optics configured to direct illumination from an illumination source to the overlay target on a sample through the objective lens when implementing the metrology recipe, wherein the overlay target in accordance with the metrology recipe includes a first grating with a first pitch on a first sample layer and a second grating with a second pitch on a second sample layer, wherein the second pitch is smaller than the first pitch, wherein the first and second sample layers are separated by a layer separation distance greater than a depth of field of the objective lens;
- a detector;
- and
- one or more collection optics configured to direct at least a portion of light collected by the objective lens to the detector, wherein the metrology recipe provides that diffraction orders of the illumination by the first grating collected by the objective lens are positioned below a threshold radius in a pupil plane and diffraction orders of the illumination by the second grating collected by the objective lens are positioned above the threshold radius in the pupil plane, wherein the one or more collection optics provide a radially-varying defocus distribution to compensate for the layer separation distance, wherein the first and second gratings are simultaneously in focus on the detector;
- and
- determining an overlay measurement between the first and second layers of the sample based on the one or more images.
6 more elements
An overlay metrology method, comprising:
- receiving one or more images of an overlay target on a sample from a detector of an overlay metrology sub-system, wherein the overlay target in accordance with a metrology recipe includes a first grating with a first pitch on a first sample layer and a second grating with a second pitch on a second sample layer, wherein the second pitch is smaller than the first pitch, wherein the first and second gratings are simultaneously in focus on the detector, wherein the overlay metrology sub-system comprises:
- an objective lens;
- one or more illumination optics configured to direct illumination from an illumination source to the overlay target on the sample through the objective lens when implementing the metrology recipe, wherein the first and second sample layers are separated by a layer separation distance greater than a depth of field of the objective lens;
- a detector;
- and
- one or more collection optics configured to direct at least a portion of light collected by the objective lens to the detector, wherein the metrology recipe provides that diffraction orders of the illumination by the first grating collected by the objective lens are positioned below a threshold radius in a pupil plane and diffraction orders of the illumination by the second grating collected by the objective lens are positioned above the threshold radius in the pupil plane, wherein the one or more collection optics provide a radially-varying defocus distribution to compensate for the layer separation distance, wherein the first and second gratings are simultaneously in focus on the detector;
- and
- determining an overlay measurement between the first and second layers of the sample based on the one or more images.
5 more elements
An overlay metrology target, comprising:
- a first substrate;
- a second substrate bonded to the first substrate;
- a first overlay target comprising:
- a first grating with a first pitch on one of a first sample layer or a second sample layer;
- a second grating with a second pitch on a different one of the first sample layer or the second sample layer than the first grating target, wherein features of the first and second gratings are distributed in a first direction, wherein one of the first or second sample layers corresponds to a scribe line on the second substrate and another of the first or second sample layers corresponds to a layer in a die of the first substrate;
- a second overlay target comprising:
- a third grating with the first pitch on one of the first sample layer or the second sample layer;
- a fourth grating with the second pitch on a different one of the first sample layer or the second sample layer than the third grating target, wherein features of the third and fourth gratings are distributed in a first direction.
5 more elements
Dependencies are inferred from the claim text.