US-12619162-B2 - Extra tall target metrology

US12619162B2US 12619162 B2US12619162 B2US 12619162B2US-12619162-B2

Abstract

A metrology system includes an imaging system. The imaging system may include an objective lens. The metrology system may include one or more detectors. The metrology system may include an objective positioning stage structurally coupled to the objective lens and configured to adjust a focal plane of at least one of the one or more detectors via movement along an optical axis of the metrology system. The metrology system may include one or more proximity sensors configured to measure lateral positions of a stage element as the objective positioning stage moves along the optical axis. The metrology system may be configured to determine a metrology measurement associated with a target on a sample using the images and lateral positions of the stage element when implementing a metrology recipe.

Inventors

Yoram Uziel
Ariel Hildesheim
Alexander Novikov
Amnon Manassen
Etay Lavert
Ohad Bachar
Yoav Grauer

Assignees

KLA CORPORATION

Dates

Publication Date: 20260505
Application Date: 20220407

Claims (20)

1 . A metrology system comprising: an objective lens; one or more detectors; an objective positioning stage structurally coupled to the objective lens and configured to adjust a focal plane of at least one of the one or more detectors via movement along an optical axis, the metrology system comprising the optical axis; and one or more proximity sensors configured to measure lateral positions of a stage element as the objective positioning stage moves along the optical axis, the lateral positions measured relative to the optical axis and in directions orthogonal to the optical axis when the objective positioning stage is at each of two or more objective locations, wherein the metrology system is configured to capture images of two or more focal planes via movement of the objective positioning stage to two or more objective locations along the optical axis, each focal plane of the two or more focal planes at an axial position along the optical axis of the metrology system and orthogonal to the optical axis, wherein at least two of the two or more focal planes are separated by an axial focal distance apart that is greater than a depth of field provided by the objective lens, wherein the metrology system is configured to determine a metrology measurement associated with a target on a sample using the images and the lateral positions of the stage element when the objective positioning stage is at the two or more objective locations when implementing a metrology recipe, the target including features on the two or more focal planes according to the metrology recipe, wherein determining the metrology measurement comprises compensating for at least one of lateral shift or tilt of the objective positioning stage between the two or more objective locations using the measured lateral positions.
2 . The system of claim 1 , wherein determining the metrology measurement associated with the target on the sample using the images and the lateral positions comprises: determining the metrology measurement based on a relative location of the features on the two or more focal planes using the images; and correcting the metrology measurement by compensating for lateral shifts of the objective positioning stage between the two or more objective locations.
3 . The system of claim 1 , wherein the objective positioning stage is further configured to adjust at least one of a lateral position or a tilt of the objective lens, wherein determining the metrology measurement associated with the target on the sample using the images and the lateral positions comprises: adjusting at least one of the lateral position or the tilt of the objective lens using the objective positioning stage based on the lateral positions of the objective positioning stage to align fields of view of the images captured at the two or more objective locations within a selected tolerance prior to capturing the images; and determining the metrology measurement based on a relative location of the features on the two or more focal planes using the images.
4 . The system of claim 1 , wherein the objective positioning stage comprises at least one of a fine stage or a coarse stage, wherein the fine stage is structurally coupled to the objective lens, the objective positioning stage configured to allow for a fine movement of the fine stage along the optical axis corresponding to a fine adjustment of the focal plane of the one or more detectors, wherein the coarse stage is structurally coupled to at least one of the fine stage or the objective lens, the objective positioning stage configured to allow for a coarse movement of the coarse stage along the optical axis corresponding to a coarse adjustment of the focal plane of the one or more detectors, wherein a maximum focal plane adjustment distance of the objective positioning stage comprises at least one of a maximum fine adjustment of the fine stage or a maximum coarse adjustment of the coarse stage.
5 . The system of claim 1 , wherein, in accordance with the metrology recipe, at least one of two or more layers of the sample comprise one or more 3D NAND features.
6 . The system of claim 1 , wherein the metrology system is configured to image wafer to wafer (W2W) bonded samples and the sample, in accordance with the metrology recipe, is a W2W bonded sample.
7 . The system of claim 1 , wherein the metrology system is configured to image die to wafer (D2W) bonded samples and the sample, in accordance with the metrology recipe, is a D2W bonded sample.
8 . The system of claim 1 , wherein the metrology system is configured to image using at least one of: different illumination polarizations, different illumination numerical apertures, different illumination angles, or different illumination wavelength ranges.
9 . The system of claim 1 , wherein the one or more detectors comprise a first detector and a second detector, wherein the first detector is configured to capture first detector images at a first focal plane and the second detector is configured to capture second detector images at a second focal plane.
10 . The metrology system of claim 1 , wherein the metrology system is an overlay metrology system, the metrology measurement is an overlay error, the target is an overlay target, and the features are overlay features, according to the metrology recipe.
11 . The system of claim 3 , wherein the objective positioning stage is configured to adjust at least one of a lateral position or a tilt of the objective lens via an adjustment stage.
12 . The system of claim 11 , wherein the adjustment stage is at least one of a fine adjustment stage or a coarse adjustment stage, wherein the fine adjustment stage is operationally and structurally coupled to and configured to adjust at least one of a lateral position or a tilt of at least one of a fine stage or the objective lens, wherein the coarse adjustment stage is operationally and structurally coupled to and configured to adjust at least one of a lateral position or a tilt of a coarse stage.
13 . The system of claim 4 , wherein the objective positioning stage comprises the fine stage, wherein the fine stage is structurally supported radially about the optical axis by two or more thin flexure arms configured to allow for the fine movement of the fine stage along the optical axis, and constrain a lateral translation and a tilt of the fine stage relative to the optical axis when adjusting the focal plane of the one or more detectors.
14 . The system of claim 4 , wherein the stage element is the fine stage such that the one or more proximity sensors are configured to measure the lateral positions of the fine stage as the objective positioning stage moves along the optical axis.
15 . The system of claim 4 , wherein the objective positioning stage is configured to allow for the maximum fine adjustment of the fine stage to be at least 50 microns.
16 . The system of claim 4 , wherein the objective positioning stage comprises the fine stage and a fine stage drive, the fine stage drive operationally coupled to the fine stage and configured to provide for the fine movement of the fine stage along the optical axis corresponding to the fine adjustment of the focal plane.
17 . The system of claim 4 , wherein the objective positioning stage comprises the coarse stage and a coarse stage drive operationally coupled to the coarse stage and configured to provide for the coarse movement of the coarse stage along the optical axis corresponding to the coarse adjustment of the focal plane.
18 . The system of claim 4 , wherein the objective positioning stage is configured to allow for the maximum focal plane adjustment distance to be at least 2000 microns.
19 . The system of claim 4 , wherein determining the metrology measurement associated with the target on the sample using the images and the lateral positions comprises: determining a calibration of a repeatable lateral shift and/or tilt of the fine stage.
20 . The system of claim 13 , wherein the two or more thin flexure arms are located in a parallelogram configuration.

Description

TECHNICAL FIELD The present disclosure relates generally to metrology and, more particularly, to alignment of metrology systems. BACKGROUND In wafer manufacturing, metrology is the field of measurements and may include overlay metrology, critical dimension metrology, and the like. In the manufacture of wafers, with an increasing number of layers and/or increasing individual layer height (e.g., 3D NAND, die-to-wafer (D2W), wafer-to-wafer (W2W), and the like) comes an increasing height range between layers and/or features of interest. Traditional metrology systems may not have the focal plane adjustment distances needed to image multiple layers and/or features at increasingly higher distances from each other while keeping within alignment tolerances of the imaging system. Further, a metrology system may need to be close to a target feature but may not have the speed and/or height adjustment range needed to move out of the way when moving to the next, significantly taller target feature. Overlay control is the control of the pattern-to-pattern alignment of multiple layers necessary. Image-based overlay metrology may typically include determining relative overlay error (e.g., misalignment error) between two or more layers of interest on a sample (e.g., wafer) based on relative imaged positions of features of an overlay target in the different layers of interest. Therefore, it may be desirable to have systems and methods to address the above shortfalls. SUMMARY A metrology system for tall metrology is disclosed in accordance with one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the system includes an objective lens. In another illustrative embodiment, the system includes one or more detectors. In another illustrative embodiment, the system includes an objective positioning stage structurally coupled to the objective lens and configured to adjust a focal plane of at least one of the one or more detectors via movement along an optical axis, the metrology system including the optical axis. In another illustrative embodiment, the system includes one or more proximity sensors configured to measure lateral positions of a stage element as the objective positioning stage moves along the optical axis. In another illustrative embodiment, the metrology system is configured to capture images of two or more focal planes via movement of the objective positioning stage to two or more objective locations along the optical axis, each focal plane of the two or more focal planes at an axial position along the optical axis of the metrology system and orthogonal to the optical axis. In another illustrative embodiment, at least two of the two or more focal planes are separated by an axial focal distance apart that is greater than a depth of field provided by the objective lens. In another illustrative embodiment, the metrology system is configured to determine a metrology measurement associated with a target on a sample using the images and lateral positions of the stage element when the objective positioning stage is at the two or more objective locations when implementing a metrology recipe, the target including features on the two or more focal planes according to the metrology recipe. A metrology system for tall metrology with air bearings is disclosed in accordance with one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the system includes a coarse stage of an objective positioning stage, the coarse stage structurally supported radially about the optical axis by one or more air bearings configured to allow for a longitudinal movement of the coarse stage along the optical axis, and constrain a lateral translation and a tilt of the coarse stage relative to the optical axis when adjusting a focal plane of one or more detectors. A method for tall overlay metrology is disclosed in accordance with one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the method includes receiving lateral positions of a stage element of a metrology system obtained from one or more proximity sensors, the lateral positions measured relative to an optical axis. In another illustrative embodiment, the metrology system is configured to adjust a focal position of at least one of one or more detectors of the metrology system, where the metrology system is configured to capture images of two or more focal planes via movement of an objective positioning stage to two or more objective locations along the optical axis, each focal plane of the two or more focal planes at an axial position along the optical axis of the metrology system and orthogonal to the optical axis, where at least two of the two or more focal planes are separated by an axial focal distance apart that is greater than a depth of field provided by an objective lens. In another illustrative embodiment, the method includes receiving the images of the two or more foca