An autofocus system

Abstract

An autofocus system includes (a) an illumination path configured to illuminate a sample with an emitted beam to form a plurality of point array groups on the sample, the point array groups including an upstream point array group formed on a first side of an imaging region and a downstream point array group formed on the other side of the imaging region; and (b) a collection path including (b.1) a first segment comprising a first spherical telescope, a first field curvature compensator, a first prism, and a first collimating relay substantially composed of a first relay input spherical lens and a first relay output spherical lens; (b.2) a second segment comprising a second spherical telescope, a second field curvature compensator, a second prism, and a second collimating relay substantially composed of a second relay input spherical lens and a second relay output spherical lens; and (b.3) a sharing module.

Description

Technical Field

[0001] This application claims the benefit and priority of U.S. Patent Application No. 18 / 762,566, filed July 2, 2024, entitled “Autofocus System Including Multiple Collection Path Segments and Sharing Modules,” which is incorporated herein by reference in its entirety. Background Technology

[0002] In high-volume optical inspection systems, autofocus plays a crucial role in ensuring accurate and efficient inspection processes. These systems are designed to inspect samples, such as wafers or photomasks, at high speeds to detect defects or anomalies.

[0003] A major challenge these systems face is maintaining consistent focus over large areas of the sample surface. Samples may vary in thickness, curvature, or surface topography, which can affect the focal plane. Without autofocus, the inspection system may struggle to maintain optimal focus, leading to inaccurate or incomplete inspection results.

[0004] There is an increasing need for an efficient and accurate autofocus system and method. Utility Model Content

[0005] An autofocus system and a method as shown in this application are provided.

[0006] A method for autofocusing by an autofocus system is provided, the method comprising: (a) illuminating a sample with an emitted beam to form a plurality of dot array groups on the sample, wherein the dot array groups include an upstream dot array group formed on a first side of an imaging region and a downstream dot array group formed on the other side of the imaging region; (b) collecting the collected beam emitted from the sample along a collection path including an entrance pupil; (c) focusing the collected beam along a first axis while imaging the entrance pupil along a second axis to provide the beam for optical processing; (d) generating a detection signal representing the optically processed beam; and (e) determining the focus state of an evaluation beam affecting the imaging region.

[0007] An autofocus system is provided, comprising (a) an illumination path configured to illuminate a sample with an emitted beam to form a plurality of point arrays on the sample, the point arrays including an upstream point array group formed on a first side of an imaging region and a downstream point array group formed on the other side of the imaging region; (b) a controller; and (c) a collection path, comprising (c.1) a first segment including a first spherical telescope, a first field curvature compensator, a pair of first prisms, and a first collimation relay substantially consisting of a first relay input spherical lens and a first relay output spherical lens; and (c.2) a second segment including a second spherical telescope, a second field curvature compensator, and a pair of first prisms. A second prism, and a second collimating relay consisting essentially of a second relay input spherical lens and a second relay output spherical lens; (c.3) a shared module configured to (i) receive a first collected beam and a second collected beam, (ii) optically process the first collected beam to provide a first segment, each first collected beam having a pair of first rays, and (iii) optically process the second collected beam to provide a second segment, each second collected beam having a pair of second rays; and a sensor along the first and second branches and configured to generate a detection signal indicating the light output from the first segment and the light output from the second segment. Attached Figure Description

[0008] The subject matter considered as an embodiment is specifically pointed out and explicitly stated at the end of the specification. However, the embodiments, whether in terms of organization or operation, together with their samples, features and advantages, are best understood by referring to the following detailed description, which should be read in conjunction with the accompanying drawings.

[0009] Figure 1 Examples of autofocus systems and related evaluation systems are shown; Figure 2 This shows instances of samples and the points formed on them; Figure 3 An example is shown of a mask with an off-axis slit and the effect of the wavefront on the light rays emitted from the mask; Figure 4 An example of the optical processing applied to the slits of the mask is shown; Figure 5 An example of distance-based focus sensing is shown; Figure 6 Examples of at least some components of an autofocus system are shown; Figure 7 Examples of at least some components of an autofocus system are shown; Figure 8 Examples of at least some components of an autofocus system are shown; Figure 9Examples of at least some components of an autofocus system are shown; Figure 10 Examples of at least some components of an autofocus system are shown; Figure 11 Examples of at least some components of an autofocus system are shown; Figure 12 Examples of at least some components of an autofocus system are shown; Figure 13 An instance of a splitter is shown; Figure 14 Examples of at least some components of an autofocus system are shown; Figure 15 Examples of at least some components of an autofocus system are shown; Figure 16 Examples of at least some components of an autofocus system are shown; Figure 17 Examples of at least some components of an autofocus system are shown; Figure 18 Examples of points formed on the sensor are shown; Figure 19 Examples of at least some components of an autofocus system are shown; Figure 20 This demonstrates an instance of a method; Figure 21 This describes an instance of a method; and Figure 22 This illustrates an instance of a method.

[0010] It should be understood that, for the sake of simplicity and clarity, the components shown in the figures are not necessarily drawn to scale. For example, the dimensions of some components may be exaggerated relative to others for clarity. Furthermore, component symbols may be repeated in different figures when deemed appropriate to indicate corresponding or similar components. Detailed Implementation

[0011] Optical systems, particularly those used in large field-of-view and high numerical aperture (NA) imaging applications such as inspection tools, face the significant challenge of maintaining performance while managing complexity. These systems often require sophisticated optical components to achieve the desired magnification and resolution, covering a wide field of view. However, the high NA required to achieve such performance typically necessitates complex optical layouts, which can introduce distortion and reduce transmitted intensity. This becomes especially problematic when the sample or the specimen being inspected is sensitive to the intensity and quality of illumination.

[0012] Existing solutions typically involve using multiple lenses and compensating optics to correct field curvature and other aberrations. While useful, these methods often increase complexity and sensitivity to alignment and manufacturing tolerances. Furthermore, the introduction of numerous optics can lead to reduced transmission intensity due to light loss at each interface, which is particularly detrimental in applications where the sample cannot withstand high-intensity illumination—as increased illumination intensity is required to compensate for the significant loss. Moreover, the complexity of these systems often results in greater susceptibility to mid-range misalignment and manufacturing variations, which can impair optical performance and necessitate more stringent and costly production controls.

[0013] This system addresses these and other problems by providing a simplified optical solution that separates the field of view and utilizes field segmentation to achieve a near-diffraction-limited point array. The system includes a mask (in...) Figure 1 The standard designation is 110), which has double slits (in Figure 1 (Illustrated as 112), the mask maintains the original optical axis and uses only an off-center slit to preserve optical performance. In doing so, the system introduces only field curvature, which can be effectively managed using simple window-based optical path compensation techniques—for example, a first field curvature compensator 144 and a second field curvature compensator 174, which are segmented optical components (see...). Figure 14 The elegance of this solution lies in the reduction of system complexity, which allows the system to achieve a high level of performance with reduced sensitivity to tolerances. The system design integrates a smaller number of lenses, which not only enhances transmission intensity but also improves sensitivity without damaging the sample.

[0014] In addition, the system's beam splitter (in) Figure 1 Operating with a universal optical axis (indicated by 130°), it minimizes overlap between adjacent fields of view and allows samples to be illuminated in a staggered array of dots. This innovative autofocus and field segmentation method represents a significant advancement, providing a simpler, more robust, and efficient solution for high-NA and large-field-of-view imaging systems.

[0015] In the field of aerial imaging, practitioners frequently encounter challenges related to the limited field of view (FOV) captured by lithography systems. Traditionally, methods for extending the FOV typically involve placing multiple cameras adjacent to each other. This configuration aims to extract the maximum FOV from the scene while minimizing the number of optical relays required. However, such an arrangement can lead to increased complexity, cost, and size of the imaging apparatus, as well as potential alignment problems between individual camera units.

[0016] Existing solutions for enhancing the field of view (FOV) in aerial imaging tools typically require a large number of repetitive optical components, which can be cumbersome and economically inefficient. Furthermore, using multiple cameras to cover a wider area introduces complexity in image processing and stitching, potentially impacting overall image quality. Additionally, the multiple optical relays required to focus on each camera can further complicate system design and reduce imaging efficiency.

[0017] This system addresses these challenges by introducing a splitter strategically positioned near the image plane downstream of the mask. The FLS effectively separates the field of view onto the wafer or mask without requiring additional optical relays to feed the image into the camera. By utilizing the relatively small numerical aperture (NA) in the image space, the system minimizes field-of-view separation on the wafer or lithography mask. The system also determines the optimal location for separating the field of view from the intermediate image, ensuring that light is not cut off, which typically requires the use of a bladed mirror. This innovative approach allows for capturing an extended FOV with minimal optical component repetition, simplifying imaging system design and reducing associated costs.

[0018] According to one embodiment, an autofocus system is provided, comprising: an illumination path configured to illuminate a sample with a light beam to form a plurality of dot arrays on the sample, the sample including a first set of dot arrays formed on a first side of an imaging region and a second set of dot arrays formed on another side of the imaging region; a sensor; a controller; a collection path including an inlet pupil and configured to collect a collection light beam emitted from the sample and to focus the collection light beam along a first axis while imaging the inlet pupil along a second axis to provide a light beam for optical processing; wherein the sensor is configured to generate a detection signal representing the optically processed light beam; and wherein the controller is configured to determine the focus state of an evaluation light beam impacting the imaging region.

[0019] The imaging area is provided using aerial lighting.

[0020] According to one embodiment, the controller is configured to generate a preliminary automatic estimate of the future focus state of the evaluation beam when it reaches a defined position of a first set of point arrays.

[0021] According to one embodiment, the controller is configured to update the initial autofocus estimate within the time it takes to approach the imaging area to a defined position.

[0022] According to one embodiment, the first set of point arrays includes a first point array, a second point array, and a third point array.

[0023] According to one embodiment, the second set of point arrays includes a fourth point array, a fifth point array, and a sixth point array.

[0024] According to one embodiment, each of the plurality of point arrays and the first set of point arrays are offset along a first axis and a second axis.

[0025] According to one embodiment, each point array is a linear point array.

[0026] According to one embodiment, the optically processed beam forms a pair of points on each of a plurality of point arrays, wherein the distance between each pair of points indicates the focus state associated with the corresponding point array.

[0027] According to one embodiment, the controller is configured to ignore detection signals based on sample elements illuminated by at least a portion of the illumination beam.

[0028] According to one embodiment, the controller is configured to determine at least one of the pitch angle and roll angle of the emitted beam.

[0029] Figure 20 An example of an autofocus method 500 for an autofocus system (10) is described, the method comprising: a. Illuminate the sample using an emitting beam 510 to form a plurality of dot arrays on the sample, wherein the dot arrays include a first set of dot arrays formed on a first side of the imaging region and a second set of dot arrays formed on the other side of the imaging region.

[0030] b. Collect the 520 beam emitted from the sample along the collection path containing the inlet pupil.

[0031] c. Focus the collected beam along the first axis 530, while imaging the inlet pupil along the second axis to provide the beam for optical processing.

[0032] d. Generate a detection signal of 540 representing the optical processing beam.

[0033] e. Determine the focus state of the evaluation beam in the 550 impact imaging region. The detection signal indicates the focus state at multiple locations on the sample—forming a multidimensional array with two or more locations on multiple axes—and originates from different sides of the imaging region, thus making it straightforward to infer the focus state of the evaluation beam.

[0034] f. Respond to the focus status 590. The response may include changing the focus status of the evaluation system.

[0035] According to one embodiment, the method includes generating a preliminary autofocus estimate of the future focus state of an evaluation beam, the estimate being obtained when the evaluation beam reaches a defined position of a first set of point arrays.

[0036] According to one embodiment, the method includes updating the initial autofocus estimate as the device approaches a defined position that reaches the imaging region.

[0037] According to one embodiment, the first set of point arrays includes a first point array, a second point array, and a third point array.

[0038] According to one embodiment, the second set of point arrays includes a fourth point array, a fifth point array, and a sixth point array.

[0039] According to one embodiment, all the multiple point arrays and the first set of point arrays are staggered on the first and second axes. This staggering on the two axes reduces the number of segmentation components required for separation between the multiple point arrays.

[0040] According to one embodiment, each point array is a linear point array.

[0041] According to one embodiment, the optically processed beam forms a pair of points in each plurality of point arrays, wherein the distance between each pair of points indicates the focus state associated with the corresponding point array.

[0042] According to one embodiment, method 500 includes ignoring sample element detection signals based on at least a portion of the emitted light beam illumination.

[0043] According to one embodiment, step 540 includes determining at least one of the pitch angle and roll angle of the emitting beam.

[0044] According to one embodiment, an autofocus system is provided, comprising: a. An illumination path configured to illuminate the sample with an emitted beam, forming multiple point arrays on the sample, including a first set of point arrays formed on one side of the imaging region and a second set of point arrays formed on the other side of the imaging region.

[0045] b. Controller.

[0046] c. A collection path configured to receive a first collection beam and a second collection beam from the sample. The collection path includes: i. A mask located at the inlet pupil, the mask comprising a pair of off-axis slits for truncating each collected beam to provide a pair of rays for each collected beam.

[0047] ii. A splitter configured to (i) direct a first ray associated with a first collected beam to a first branch, and (ii) direct a ray associated with a second collected beam to a second branch.

[0048] iii. A sensor, extending along a first branch and a second branch, and configured to receive a pair of points in each plurality of point arrays, wherein the distance between each pair of points indicates a focus state associated with the respective point array. The optical axis of the first branch is oriented relative to the optical axis of the second branch.

[0049] According to one embodiment, the controller is configured to receive at least one sensor detection signal from a first sensor and a second sensor, and determine the focus state of the evaluation beam. According to another embodiment, the controller is configured to change the focus of the evaluation system by controlling one or more engines that set the focus of the evaluation system, for example, by moving a lens or other optical component of the evaluation system, changing the position of the evaluation system, changing the position of the sample, etc.

[0050] According to one embodiment, the first branch includes a first spherical telescope, a first field curvature compensator, and a first collimation relay.

[0051] According to one embodiment, the second branch includes a second spherical telescope, a second field curvature compensator, and a second collimation relay.

[0052] According to one embodiment, the first field curvature compensator, unlike a lens, is essentially composed of a first segmented optical assembly comprising segments with different refractive indices. The first segmented optical assembly is located at a position with a very small (discrete) field of view associated with the light rays.

[0053] According to one embodiment, the second field curvature compensator differs from the lens and is essentially composed of a second segmented optical assembly, which includes segments with different refractive indices.

[0054] According to one embodiment, both the first and second segmented optical components are located at positions with very small light-related fields of view.

[0055] According to one embodiment, the first ray includes a pair of first central rays (in) Figure 12 The middle label is 66-2, 67-2) and two pairs of first marginal rays (the first pair of marginal rays (in Figure 12 The middle markings are 66-1 and 67-1) and the second pair of edge rays (in Figure 12 The first field curvature compensator is essentially composed of (i) the first segment of the first refractive index (in Figure 14 (i) The segment is indicated as 144-1), which is propagated by a pair of first central rays, and (ii) the second segment with a second refractive index (in Figure 14 (Illustrated as 144-2), the segment propagates through two pairs of first edge rays, wherein the first refractive index is different from the second refractive index.

[0056] According to one embodiment, the second ray includes a pair of second central rays (in...) Figure 12 The middle label is 68-2, 69-2) and two pairs of marginal rays (including the first pair of marginal rays (in Figure 12 The middle label is 68-1, 69-1) and the second pair of edge rays (in Figure 12 The winning designation is indicated as 68-3 or 69-3).

[0057] According to one embodiment, the second-stage curvature compensator (in...) Figure 14 The segment marked 174 is essentially composed of a first segment (174-1) of a first refractive index, which propagates through a pair of second central rays (including a third pair of marginal rays 68-2 and a fourth pair of marginal rays 69-2), and a second segment of a second refractive index (in... Figure 14 (Illustrated as 174-2), the segment propagates through two pairs of edge rays, wherein the first refractive index and the second refractive index are different.

[0058] According to one embodiment, the first spherical telescope is configured to provide a reduced image of the inlet pupil (the reduction magnification may be between six and twelve or equal to ten or any other value) on the focal plane of the output lens of the first spherical telescope.

[0059] According to one embodiment, the second spherical telescope is configured to provide a reduced image of the inlet pupil on the focal plane of the output lens of the second spherical telescope.

[0060] According to one embodiment, the first collimation relay includes a first relay input spherical lens and a first relay output spherical lens.

[0061] According to one embodiment, the second collimation relay includes a second relay input spherical lens and a second relay output spherical lens.

[0062] According to one embodiment, the autofocus system includes a pair of first prisms located on the focal plane of the output lens of a first spherical telescope.

[0063] According to one embodiment, the autofocus system includes a pair of second prisms located on the focal plane of the output lens of a second spherical telescope. The pair of second prisms causes the rays of the first pair of light rays to move away from each other.

[0064] According to one embodiment, the autofocus system includes a first collimation relay motion mechanism configured to change the distance between a first relay input spherical lens and a first relay output spherical lens.

[0065] According to one embodiment, the first collimation relay motion mechanism moves the first relay output spherical lens and also moves the first sensor to maintain the distance between the first relay output spherical lens and the first sensor. According to one embodiment, the first collimation relay motion mechanism includes a first motor.

[0066] According to one embodiment, the autofocus system includes a second collimation relay motion mechanism configured to change the distance between a second relay input spherical lens and a second relay output spherical lens.

[0067] According to one embodiment, the second collimation relay motion mechanism moves the second relay output spherical lens and the second sensor to maintain the distance between the second relay output spherical lens and the second sensor. According to one embodiment, the second collimation relay motion mechanism includes a second motor.

[0068] According to one embodiment, different distances between the relay input spherical lens and the relay output spherical lens result in different trade-offs between the dynamic range and sensitivity of the autofocus system. A larger dynamic range is associated with lower sensitivity. Different distances are associated with different effective focal lengths of the collimating relay.

[0069] According to one embodiment, the different distances between the first relay input spherical lens and the first relay output spherical lens are related to the different effective focal lengths of the first collimating relay.

[0070] According to one embodiment, the first collimation relay is essentially composed of a first relay input spherical lens and a first relay output spherical lens.

[0071] The relay includes a relay input spherical lens and a relay output spherical lens. These lenses have defects or aberrations that cause the optical power at different points on any relay spherical lens to differ. These different optical powers also introduce residual optical power along the secondary axis of any relay spherical lens. According to one embodiment, the optical power value at a point on the relay spherical lens is related to the spatial relationship between the center of the relay spherical lens and that point. Optical power is related to magnification.

[0072] According to one embodiment, the first collimating repeater exhibits primary optical power on the main axis, and when a beam of tilted light (off-axis light) is received—the light is oriented relative to the main axis and the collimating axis of the collimating repeater—the tilted light strikes a point located outside the center of the repeater's spherical lens (off-center point) and exhibits optical power on both axes.

[0073] The tilted light portion is caused by the non-zero angle between the optical axis formed between the mask and the splitter and the optical axes of the first and second branches.

[0074] According to one embodiment, the autofocus system includes a selectable depth-of-field unit configured to select a reference focal plane for the autofocus system.

[0075] According to one embodiment, the selectable depth-of-field unit includes a first selectable depth-of-field unit—the unit can be selectively placed inside or outside the first branch. According to one embodiment, the first selectable depth-of-field unit is a first window, which can be selectively placed inside the first spherical telescope. When placed inside the first spherical telescope, the depth of field of the first branch is located at a first position; while when placed outside the first spherical telescope, the depth of field of the first branch is located at a second position different from the second position.

[0076] According to one embodiment, the selectable depth-of-field unit includes a second selectable depth-of-field unit—the unit can be selectively placed inside or outside the second branch. According to one embodiment, the second selectable depth-of-field unit is a second window, which can be selectively placed inside the second spherical telescope. When placed inside the second spherical telescope, the depth of field of the second branch is located at a third position; while when placed outside the second spherical telescope, the depth of field of the second branch is located at a fourth position different from the first position.

[0077] Figure 21 An example of an autofocus method 501 of an autofocus system (10) is shown, the method comprising: a. Illuminate the sample (510) with a light beam (30) to form a plurality of dot arrays (40) on the sample, wherein the dot arrays include a first set of dot arrays (42) formed on a first side of the imaging region (39) and a second set of dot arrays (44) formed on the other side of the imaging region (39).

[0078] b. Collect (520) the collected beam emitted from the sample along the collection path containing the inlet pupil.

[0079] c. Focus (530) the collected beam along the first axis (91) while simultaneously image the inlet pupil along the second axis (92) to provide the beam for optical processing.

[0080] d. Generate (540) to represent the detection signal (100) of the optically processed beam.

[0081] e. Determine (550) the focus state of the evaluation beam (38) that affects the imaging area (39).

[0082] f. Respond to the focus status (590). The response may include changing the focus status of the evaluation system.

[0083] According to one embodiment, steps 510-550 are repeated multiple times at different time points.

[0084] According to one embodiment, step 540 is followed by step 560, which generates a preliminary autofocus estimate of the future focus state obtained when the evaluation beam reaches the defined position of the first set of point arrays. Step 560 may be included in step 590.

[0085] For example—assuming the sample is scanned, causing the first set of dot arrays to precede the evaluation beam—then the initial autofocus estimate might be based on focus information embedded in the first set of dot arrays. The initial autofocus estimate might be equal to the focus state reflected by the first set of dot arrays—or it might be different from the focus state reflected by the first set of dot arrays.

[0086] For example—assuming the sample is scanned, causing the second dot array to precede the evaluation beam—then the initial autofocus estimate might be based on focus information embedded in the second dot array. The initial autofocus estimate might be equal to the focus state reflected by the second dot array—or it might differ from the focus state reflected by the second dot array.

[0087] According to one embodiment, method 501 includes step 570, updating the preliminary autofocus estimate at the time when the proximity imaging region (39) reaches a defined position. Step 570 may be included in step 590.

[0088] The update may be based on the focus state of the imaging region (or the focus of any dot array group) obtained in one or more iterative steps 510-550 after providing an initial autofocus estimate.

[0089] See Figure 2 ,For example, Figure 2 The right side shows the status of sample 99 and the first and second set of dot arrays at a certain point in time. At this time, a preliminary autofocus estimate is made for the focus state of imaging region 39 based on the focus information embedded in the first set of dot arrays. Step 570 may update the preliminary autofocus estimate before imaging region 39 reaches the specific position of the first set of dot arrays (at the time point). Figure 2 The left side shows that imaging region 39 has reached the specific location of the first set of point arrays (at the time point mentioned).

[0090] According to one embodiment, all the multiple point arrays (40) and the first set of point arrays (42) are offset along the first axis (91) and the second axis (92).

[0091] According to one embodiment, some or all of the point arrays are linear point arrays.

[0092] According to one embodiment, some or all of the point arrays are nonlinear point arrays.

[0093] According to one embodiment, the optically processed beam forms a pair of points for each plurality of point arrays, wherein the distance between each pair of points (on the sensor plane) represents the focus state associated with the respective point array.

[0094] According to one embodiment, step 550 includes ignoring detection signals (100) based on sample elements that are at least partially illuminated by the emitted beam (30). Ignoring may be based on design information or other information indicating sample regions (e.g., highly dense logic component regions) that would provide low signal-to-noise ratio signals and / or diffraction signals when illuminated.

[0095] According to one embodiment, step 550 includes determining at least one of the pitch angle and roll angle of the emitted beam. Either of these angles can be detected by comparing focus information from different point arrays.

[0096] According to one embodiment, at least one of method 500 and method 501 includes adjusting the distance between optical components in the collection path of the evaluation system to optimize the focus state of the evaluation beam.

[0097] According to one embodiment, adjusting the distance between optical components includes moving a lens or mirror in the collection path of the evaluation system.

[0098] According to one embodiment, the method includes adjusting the intensity of the emission beam used by the evaluation system to optimize the focus state of the evaluation beam.

[0099] According to one embodiment, adjusting the beam intensity of the evaluation system includes controlling the power of the light source or adjusting the aperture of the illumination path of the evaluation system.

[0100] According to one embodiment, at least one of method 500 and method 501 includes determining the depth of field of the autofocus system based on the focus state of the evaluation beam.

[0101] According to one embodiment, at least one of method 500 and method 501 includes adjusting the position of the imaging region according to a determined depth of field.

[0102] According to one embodiment, at least one of method 500 and method 501 includes compensating for aberrations in the collection path to improve the focus state of the evaluation beam 38.

[0103] According to one embodiment, aberration compensation includes adjusting the position or shape of one or more optical components in the collection path of the evaluation system.

[0104] According to one embodiment, at least one of methods 500 and 501 includes determining a focus pointer based on a detection signal to quantitatively evaluate the focus state of the light beam. The focus pointer may indicate focus along any axis, relative focus error between light beams, etc.

[0105] According to one embodiment, step 590 includes adjusting the focus state of the evaluation beam according to a determined focus index.

[0106] According to one embodiment, step 590 includes capturing an image of a sample by an evaluation system associated with the autofocus system, the image being based on the focus state of the evaluation beam.

[0107] According to one embodiment, step 590 includes analyzing the captured images to extract information about the sample.

[0108] According to one embodiment, step 590 includes adjusting the position or orientation of the sample based on the focus state of the evaluation beam.

[0109] According to one embodiment, step 590 includes determining a focus error signal based on the detection signal (100) to provide feedback for adjusting the focus state of the evaluation beam.

[0110] According to one embodiment, step 590 includes using a focus error signal to control the position or movement of one or more optical components of the evaluation system.

[0111] According to one embodiment, an autofocus system (10) is provided, the system comprising: a. An illumination path configured to illuminate the sample with an emitted beam, forming multiple point arrays on the sample, including a first set of point arrays formed on a first side of the imaging region and a second set of point arrays formed on the other side of the imaging region.

[0112] b. Controller.

[0113] c. Collection path, including: i. A first branch, the first branch comprising a first spherical telescope, a first field curvature compensator, a pair of first prisms, and a first collimating relay consisting essentially of a first relay input spherical lens and a first relay output spherical lens.

[0114] ii. The second branch, comprising a second spherical telescope, a second field curvature compensator, a pair of second prisms, and a second collimating relay consisting essentially of a second relay input spherical lens and a second relay output spherical lens; iii. A shared module configured to (i) receive a first collected beam and a second collected beam, (ii) perform optical processing on the first collected beam to provide it to a first segment, each first collected beam having a pair of first rays, and (iii) perform optical processing on the second collected beam to provide it to a second segment, each second collected beam having a pair of second rays; d. A sensor, which is located along a first branch and a second branch and is configured to generate a detection signal indicating light output from the first branch and light output from the second branch.

[0115] According to one embodiment, the shared module includes a mask located at the inlet pupil, the mask including a pair of off-axis slits for cutting off each collected beam to provide a pair of rays for each collected beam.

[0116] According to one embodiment, the sharing module further includes a splitter configured to (i) direct a first ray associated with a first collected beam to a first branch, and (ii) direct a ray associated with a second collected beam to a second branch.

[0117] According to one embodiment, the first collimation relay exhibits primary optical power along the main axis and residual optical power along the secondary axis.

[0118] According to one embodiment, the autofocus system includes a selectable depth-of-field unit configured to select a reference focal plane for the autofocus system.

[0119] According to one embodiment, the selectable depth-of-field unit includes a first window selectively positioned within a first spherical telescope and a second window selectively positioned within a second spherical telescope.

[0120] According to one embodiment, a system is provided, comprising: a. An illumination path configured to illuminate a sample using an emitted light beam, forming a plurality of point arrays on the sample, the sample including a first set of point arrays formed on a first side of the imaging region and a second set of point arrays formed on the other side of the imaging region.

[0121] b. Sensors.

[0122] c. Controller.

[0123] d. A collection path configured to receive a first collection beam and a second collection beam from the sample. The collection path includes: i. A mask located at the inlet pupil, the mask comprising a pair of off-axis slits for truncating each collected beam to provide a pair of rays for each collected beam; ii. A splitter comprising an optical splitting assembly including (i) a first reflecting surface configured to guide a first ray associated with a first collected beam into a first branch, and (ii) a second reflecting surface oriented relative to the first reflecting surface and configured to guide a ray associated with a second collected beam into a second branch. The first and second reflecting surfaces are located at positions (a) outside the image plane and (b) where there is separation between the first and second ray rays.

[0124] According to one embodiment, the optical segmentation component is a prism.

[0125] According to one embodiment, the prism is a knife-edge right-angle prism.

[0126] According to one embodiment, the shape and position of the optical segmentation component are designed to prevent vignetting of any first or second light rays.

[0127] According to one embodiment, the shape and position of the optical segmentation component are located at the position furthest from the intermediate image plane, wherein neither the first ray nor the second ray is truncated by the prism.

[0128] According to one embodiment, the divider includes a housing and a mechanical interface connected to the housing and the optical dividing assembly.

[0129] According to one embodiment, the housing includes an input opening, a first light output opening, and a second light output opening.

[0130] Figure 22 This is an embodiment of a method (600) for field manipulation, the method comprising: a. Irradiate (610) the sample with an emitting beam to form multiple dot arrays on the sample, including a first set of dot arrays formed on a first side of the imaging region and a second set of dot arrays formed on the other side of the imaging region.

[0131] b. Collect (620) the first and second collection beams from the sample.

[0132] c. Each collected beam is truncated (630) using a mask (110) located in the inlet pupil, wherein the mask (110) includes a pair of off-axis slits (112) to provide a pair of rays for each collected beam.

[0133] d. The first portion (640) of the first ray guiding system associated with the first collecting beam uses the first reflective surface of an optical segmentation assembly located outside the reflective surface position on the intermediate image plane. The first portion may be a first branch or any other portion not used for autofocus.

[0134] e. A second reflective surface of the optical segmentation assembly is used to orient a second portion (650) of the second light guiding system associated with the second collected beam, wherein the second reflective surface is aligned with the first reflective surface. The second portion may be a second branch or any other portion not used for autofocus.

[0135] According to one embodiment, steps 640 and 650 are based on the separation between the first ray and the second ray at the reflective surface position.

[0136] According to one embodiment, steps 610-650 are used in an autofocus measurement system.

[0137] According to one embodiment, steps 610-650 are used for other non-autofocus purposes.

[0138] According to one embodiment, the optical segmentation component is a prism.

[0139] According to one embodiment, the prism is a knife-edge right-angle prism.

[0140] According to one embodiment, the method includes shaping and positioning optical segmentation components to prevent peripheral light shading of the first and second rays.

[0141] According to some embodiments, the method includes shaping and positioning optical segmentation components at the location furthest from the intermediate image plane to ensure that no first or second ray is cut by the prism.

[0142] According to some embodiments, the method includes connecting a mechanical interface to the housing and the optical segmentation assembly of the segmenter (130).

[0143] Figure 1 An embodiment of an autofocus system 10 and an evaluation system 11 is demonstrated, wherein the evaluation system utilizes the autofocus system 10 to maintain an evaluation beam at a desired focus position on a sample 99. The evaluation system 11 includes an evaluation illumination 11, an evaluation system beam splitter 14, and an evaluation sensor 13. The evaluation system outputs an evaluation beam 38 that passes through a first dichroic mirror 24 and is focused by an objective lens 19, striking the sample 99 to form a return beam. This return beam is collected by the objective lens 19 and guided by the first dichroic mirror 24 to the evaluation system beam splitter 14, and then to the evaluation sensor 13.

[0144] The first dichroic mirror 24 and the objective lens 19 are also used by the autofocus system 10.

[0145] The autofocus system 10 includes an autofocus (AF) illumination unit 19, an initial lens 21, an illumination / collection beam splitter 22, a third lens 23, a mask 110 (with a slit 112), a splitter 130, a first lens 125, a first branch 140, a first sensor 50-1, a second lens 126, a second branch 170, and a second sensor 50-2.

[0146] The first branch 140 includes a first spherical telescope 142, a first field curvature compensator 144, and a first collimation relay 146.

[0147] The second branch 170 includes a second spherical telescope 172, a second field curvature compensator 174, and a second collimation relay 176.

[0148] Figure 1The first conjugate surface 111 and the first conjugate surface 113 of the mask pupil are shown.

[0149] Figure 2 Displays sample 99 and multiple point arrays at two different time points.

[0150] Multiple point arrays include a first set of point arrays 42 and a second set of point arrays 44, which are staggered on the first axis 91 and the second axis 92.

[0151] The first set of point arrays 42 includes the first point array 42-1, the second point array 42-2, and the third point array 42-3.

[0152] The second set of dot arrays 44 includes the fourth dot array 44-1, the fifth dot array 44-2, and the sixth dot array 44-3.

[0153] Figure 3 The diagram illustrates the relationship between the focused state of the collected beam arriving at mask 110 with wavefront 31 and the light rays from slits 112, which are off-axis slits. When focused, wavefront 31 is parallel to the mask, and the light rays passing through the slits are parallel to each other and perpendicular to the mask. When out of focus, the wavefront is either convex (wavefront 32) or concave (wavefront 33), and the light rays passing through the slits are oriented relative to each other and not perpendicular to the mask.

[0154] Figure 4 The diagram illustrates how the slit 112 of mask 110 converts each of the first and second set of point arrays into a pair of spaced-apart rays. For index values ​​x between 1 and 3, point array 42-x is converted into ray pairs 46-x and 47-x, and point array 44-x is converted into ray pairs 48-x and 49-x.

[0155] The distance between rays of a single ray pair behind mask 110 indicates the focus state associated with the ray pair. Figure 4 The display shows the first distance D1 45-1 between the first rays 46-1 and 47-1, the second distance D2 45-2 between the second rays 46-2 and 47-2, the third distance D3 45-3 between the third rays 46-3 and 47-3, the fourth distance D4 45-4 between the fourth rays 48-1 and 49-1, the fifth distance D5 45-5 between the fifth rays 48-2 and 49-2, and the sixth distance D6 45-6 between the sixth rays 48-3 and 49-3.

[0156] Figure 4 It also shows a reduced image 51 of the inlet pupil on the focal plane of the output lens of the first spherical telescope.

[0157] Figure 5This demonstrates the effect of the wavefront of light on the focal plane of the output lens of the spherical telescope on the sensing of the light by the sensor.

[0158] The focusing stage should be determined based on the distance between the light rays illuminating the sensor. When the wavefront 1031 is parallel to the sensor, the distance clearly indicates the focus state. When the wavefront 1032 is concave or convex 1033, the distance may be blurred, depending on the focus position relative to the light rays. To solve the blurring problem, the light rays are spaced apart by using a prism or a pair of prisms.

[0159] Figure 6-8 Figures 9-18 show an autofocus system or components of an autofocus system with a fixed collimation relay. Figure 9 An autofocus system with a collimation relay motion mechanism is shown, the motion mechanism being configured to change the distance between the relay input spherical lens and the relay output spherical lens of the collimation relay. According to one embodiment, Figure 6-8 All autofocus systems, including those from 9 to 18, include a collimation relay mechanism.

[0160] Figure 6 and 7 The display autofocus system includes an imported pupil 80, a mask 110, a splitter 130, a first lens 125, a second lens 126, a first spherical telescope input lens 142-1, a first selectable depth-of-field unit 203-1, a first field curvature compensator 144, a first spherical telescope output lens 142-2, a first prism 145, a first relay input spherical lens 146-1, a first relay output spherical lens 146-1, a first sensor 50-1, a second spherical telescope input lens 172-1, a second selectable depth-of-field unit 203-2, a second field curvature compensator 174, a second spherical telescope output lens 172-2, a second prism 175, a second relay input spherical lens 176-1, a second relay output spherical lens 176-1, and a second sensor 50-2.

[0161] Figure 8 The upper part shows an autofocus system with a first selectable depth-of-field unit 203-1 in the first branch 140 and a second selectable depth-of-field unit 203-2 in the second branch 170.

[0162] Figure 8 The lower part shows the autofocus system, which has a first selectable depth-of-field unit 203-1 outside the first branch 140 and a second selectable depth-of-field unit 203-2 outside the second branch 170.

[0163] Depth of field is determined by moving the second selectable depth of field unit and the first selectable depth of field unit, while the other optical components of the first and second branches remain stationary, which improves the accuracy of the autofocus system.

[0164] Figure 9 The image shows the autofocus system at two points in time—and at two different distances between the collimating relay lenses.

[0165] The autofocus system includes: a. The first lower folding mirror 222-5 and the first upper folding mirror 222-4 are located between the first relay input spherical lens 146-1 and the first relay output spherical lens 146-2.

[0166] b. The second upper folding mirror 222-6 and the second lower folding mirror 222-7 are located between the second relay input spherical lens 176-1 and the second relay output spherical lens 176-2.

[0167] c. The first collimation relay motion mechanism 202-1 is configured to change the distance between the first relay input spherical lens 146-1 and the first relay output spherical lens 146-2.

[0168] d. The second collimation relay motion mechanism 202-2 is configured to change the distance between the second relay input spherical lens 176-1 and the second relay output spherical lens 176-2.

[0169] Figure 8 The autofocus system allows for continuous variation of the effective focal length of the collimation relay.

[0170] Figure 10 and Figure 11 An example is illustrated with mask 110, first mirror 125, second mirror 126, first spherical telescope input lens 142-1 and second spherical telescope input lens 172-1. Two pairs of light rays are separated by splitter 130. The first mirror 125 deflects light rays pairs 66-2 and 67-2, and the second mirror 126 deflects light rays pairs 68-2 and 69-2.

[0171] Figure 12 The slit 112 of the mask 110 converts each of the first and second set of point arrays into a pair of spaced rays, forming split points on the splitter 130. For an exponent value x between 1 and 3, point array 42-x is converted into a pair of rays forming split points 66-x and 67-x, while point array 44-x is converted into a pair of rays forming split points 68-x and 69-x.

[0172] Figure 13A divider 130A is described, comprising an optical dividing assembly (e.g., a prism 133) including a first reflecting surface 131 and a second reflecting surface 132. The divider 130A also includes a housing 134 and a mechanical interface. The housing includes an upper portion 135, an input opening 136, a first light output opening 137, and a second light output opening 138.

[0173] Figure 14 and Figure 15 The optical processing of light pairs by various components of the first and second branches is explained.

[0174] exist Figure 14 The various components include a first spherical telescope input lens 142-1, a first selectable depth-of-field unit 203-1, a first field curvature compensator including a first segment 144-1 and a second segment 144-2, a first spherical telescope output lens 142-2, a first prism 145 and a first relay input spherical lens 146-1, a second spherical telescope input lens 172-1, a second selectable depth-of-field unit 203-2, a second field curvature compensator 174 including a third segment 174-1 and a fourth segment 174-2, a second spherical telescope output lens 172-2, a second prism 175 and a second relay input spherical lens 176-1.

[0175] exist Figure 15 The various components include a first field curvature compensator 144, a first spherical telescope output lens 142-2, a first prism 145, a first relay input spherical lens 146-1, a first relay output spherical lens 146-1, a first sensor 50-1, a second field curvature compensator 174, a second spherical telescope output lens 172-2, a second prism 175, a second relay input spherical lens 176-1, a second relay output spherical lens 176-1, and a second sensor 50-2.

[0176] Figure 14 and Figure 15 The first pair of rays 401 (including) is shown Figure 4 First pair of rays 46-1 and 47-1), second pair of rays 402 (including Figure 4 The second pair of rays 46-2 and 47-2), and the third pair of rays 403 (including Figure 4 The third pair of rays 46-3 and 47-3), and the fourth pair of rays 411 (including Figure 4 The fourth pair of rays 48-1 and 49-1), and the fifth pair of rays 412 (including Figure 4 The fifth pair of rays 48-2 and 49-2) and the sixth pair of rays 413 (including Figure 4 The sixth ray (48-3 and 49-3).

[0177] Figure 16The optical processing of light pairs by various components of the first and second branches is shown.

[0178] These components include a first selectable depth-of-field unit 203-1, a first field curvature compensator 144, a first spherical telescope output lens 142-2, a first prism 145, and a first relay input spherical lens 146-1.

[0179] Figure 16 The first rays 46-1 and 47-1, the first pair of rays 401, the second rays 46-2 and 47-2, the second pair of rays 402, the third rays 46-3 and 47-3, and the third pair of rays 403 are shown.

[0180] Figure 17 The optical processing of light pairs by various components of the first and second branches is shown.

[0181] These components include a first spherical telescope output lens 142-2, a first prism 145, a first relay input spherical lens 146-1, and a first relay output spherical lens 146-2. Virtual line 1463 illustrates the propagation of second rays 46-2 and 47-2.

[0182] Figure 17 Display first rays 46-1 and 47-1. The first rays are located on a virtual line, which is oriented relative to the main axis 1462 of the collimation relay and relative to the secondary axis 1461 of the collimation relay, and bears the main optical power of the collimation relay.

[0183] Figure 18 The light beams are displayed as points of impact on the first sensor 50-1 and the second sensor 50-2.

[0184] The first light rays 66-1 and 67-1 form a first point 281-1 and a second point 281-2 on the first pair of pixels of the first sensor 50-1, and the spacing between these pixels is the distance DS1 271 of the first sensor.

[0185] The second light pairs 66-2 and 67-2 form the third point 282-1 and the fourth point 282-2 on the second pair of pixels of the first sensor 50-1. The spacing between these pixels is the distance DS2 272 between the second sensors.

[0186] The third light rays 66-3 and 67-3 form the fifth point 283-1 and the sixth point 283-2 on the third pair of pixels of the first sensor 50-1. The spacing between these pixels is the distance DS3 273 from the third sensor.

[0187] The fourth light rays 68-1 and 69-1 form the seventh point 284-1 and the eighth point 284-2 on the fourth pair of pixels of the second sensor 50-2. The spacing between these pixels is the distance of the fourth sensor DS4 274.

[0188] The fifth light rays 68-2 and 69-2 form the ninth point 285-1 and the tenth point 285-2 on the fifth pair of pixels of the second sensor 50-2. The spacing between these pixels is the distance of the fifth sensor DS5 275.

[0189] The sixth ray pairs 68-3 and 69-3 form the eleventh point 286-1 and the twelfth point 286-2 on the sixth pair of pixels of the second sensor 50-2. The distance between these pixels is the sixth sensor distance DS6 276.

[0190] These sensors indicate the focus status.

[0191] Figure 19 This shows an example of an autofocus system, including: a. A first turntable having a set of first spherical telescope output lenses (collectively referred to as 351), which are distinguished from each other by their different focal lengths to provide different sensitivities for the autofocus system.

[0192] b. A second turntable having a set of second spherical telescope output lenses (collectively referred to as 352), which are distinguished from each other by their different focal lengths to provide different sensitivities for the autofocus system.

[0193] Any reference to the sensor should be applied to either the first sensor or the second sensor.

[0194] Any reference for light should be applied accordingly to the beam.

[0195] Any reference to a ray should be applied accordingly to the point formed by the ray.

[0196] Any reference for a beam should be applied accordingly to the light ray.

[0197] Any reference to the beam should be applied accordingly to the point formed by the beam.

[0198] In the foregoing detailed description, numerous specific details are set forth to provide a full understanding of the disclosed embodiments.

[0199] However, those skilled in the art will understand that the presently disclosed embodiments can be implemented without these specific details. In other instances, known methods, procedures, and components have not been described in detail to avoid obscuring the presently disclosed embodiments.

[0200] The subject matter considered as a disclosed embodiment is specifically pointed out and explicitly claimed at the end of the specification. However, the disclosed embodiments, both in terms of organization and operation, together with their objectives, features, and advantages, are most readily understood by reference to the following detailed description, which should be consulted with the appendix. Figure 1 Start reading.

[0201] It should be understood that, for the sake of simplicity and clarity, the elements shown in the diagrams may not be drawn to scale. For example, the size of some elements may be exaggerated relative to others to improve clarity. Furthermore, component symbols may be repeated in the diagrams where appropriate to indicate corresponding or similar elements.

[0202] Because most of the embodiments shown in this disclosure can be implemented using optical components and circuits known to those skilled in the art, the basic concepts upon which the embodiments of this disclosure rely will not be explained in detail, nor will they obscure or distract attention from the teachings of this disclosure.

[0203] Any references to the methods in this specification shall apply accordingly to systems capable of performing the methods.

[0204] Any references to the system in this specification shall apply accordingly to methods that may be performed by said system.

[0205] The term "and / or" indicates additional or alternating meanings. For example, A and / or B means only A, only B, or A and B.

[0206] Numerous specific details have been set forth in the foregoing description in order to provide a thorough understanding of embodiments of this disclosure.

[0207] However, those skilled in the art will understand that present embodiments can be implemented without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail to avoid obscuring embodiments of this disclosure.

[0208] The subject matter of this disclosure is specifically pointed out and explicitly stated at the end of the specification. However, embodiments of this disclosure, both in their organization and manner of operation, together with their objects, features, and advantages, are best understood by referring to the following detailed description, which, together with the accompanying... Figure 1 Start reading.

[0209] Please understand that, for the sake of simplicity and clarity, the components shown in the diagrams are not necessarily drawn to scale. For example, the dimensions of some components may be exaggerated relative to others for clarity. Furthermore, component symbols may be repeated in the diagram where appropriate to indicate corresponding or similar components.

[0210] In the foregoing specification, embodiments of this disclosure have been described with reference to specific examples. However, it will be apparent that various modifications and alterations can be made thereto without departing from the broader spirit and scope of the appended claims.

[0211] Furthermore, the terms “front,” “back,” “top,” “bottom,” “above,” “below,” and similar terms used in the description and claims are for descriptive purposes only and are not necessarily used to describe permanent relative positions. It is understood that the terms used are interchangeable where appropriate, and therefore the embodiments described in this disclosure may operate, for example, in orientations different from those shown or otherwise described herein.

[0212] For any reference to the terms “including” or “having” or “comprising”, they shall generally apply to “consisting of” and / or shall generally apply to “consisting substantially of”.

[0213] However, other modifications, changes, and alternatives are also possible. Therefore, the instructions and illustrations should be considered illustrative rather than restrictive.

[0214] In the claims, any reference symbols placed in parentheses should not be construed as limiting the claims. The use of the word “comprising” does not exclude the presence of other components or steps besides those listed in the claims. Furthermore, the use of “a” or “an” herein is defined as one or more. Additionally, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed as implying that the use of the indefinite article “a” or “an” to introduce other claim components limits the specific claim containing the introduced claim component to embodiments containing only one such component, even if the claim also includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same applies to the use of definite articles. Unless otherwise stated, terms such as “first” and “second” are used only to arbitrarily distinguish the components described by these terms. Therefore, these terms are not necessarily intended to indicate the time or other priority of these components. The fact that certain measures are listed in mutually different claims does not mean that a combination of these measures cannot be used advantageously.

[0215] While certain embodiments have been shown and described herein, many modifications, substitutions, alterations, and equivalents will appear to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and alterations, and fall within the true spirit and scope of the described embodiments.

Claims

1. An autofocus system, characterized in that, The autofocus system includes: An illumination path is configured to illuminate a sample with an emitted beam, forming multiple point array groups on the sample, the point array groups including an upstream point array group formed on a first side of the imaging region and a downstream point array group formed on the other side of the imaging region; Controller; Collection paths include: The first branch includes a first spherical telescope, a first field curvature compensator, a pair of first prisms, and a first collimating relay composed of a first relay input spherical lens and a first relay output spherical lens; The second branch includes a second spherical telescope, a second field curvature compensator, a second prism, and a second collimating relay consisting of a second relay input spherical lens and a second relay output spherical lens. A shared module configured to (i) receive a first collected beam and a second collected beam, (ii) optically process the first collected beam to provide it to a first branch, each first collected beam paired with a first ray, and (iii) optically process the second collected beam to provide it to a second branch, each second collected beam paired with a second ray; and a sensor along the first branch and the second branch and configured to generate a detection signal indicating the light output from the first branch and the light output from the second branch.

2. The autofocus system of claim 1, wherein the shared module includes a mask located at the inlet pupil, the mask including an off-axis slit for cutting off each collected beam to provide each collected beam with light.

3. The autofocus system according to any one of the preceding claims, wherein the sharing module further includes a beam splitter configured to (i) direct a first ray associated with the first collected beam to the first branch, and (ii) direct a ray associated with the second collected beam to the second branch.

4. The autofocus system according to claim 1, wherein the first collimator displays the primary optical power along the main axis and the residual optical power along the secondary axis.

5. The autofocus system of claim 1, further comprising a selectable depth-of-field unit configured to select a reference focal plane of the autofocus system.

6. The autofocus system of claim 5, wherein the selectable depth-of-field unit comprises a first window selectively placed within the first spherical telescope and a second window selectively placed within the second spherical telescope.

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