Metrology system, position determination method, metrology method, and storage medium

Abstract

The application discloses a metrology system, a position determination method, a metrology method and a storage medium, and belongs to the technical field of semiconductor detection. The metrology system comprises: a light beam constraint component configured to spatially constrain an illumination light beam, the light beam constraint component being capable of changing the angular distribution of the illumination light beam when the light beam constraint component is moved; an imaging optical path component comprising an image sensor and an objective lens; and a processor configured to: determine a first target position of the light beam constraint component in a first direction based on a plurality of first displacement data sets and a plurality of second displacement data sets corresponding to the plurality of first displacement data sets obtained by moving the light beam constraint component in the first direction; and determine a second target position of the light beam constraint component in a second direction based on a plurality of third displacement data sets and a plurality of fourth displacement data sets corresponding to the plurality of third displacement data sets obtained by moving the light beam constraint component in the second direction, with the light beam constraint component being in the first target position. The application adjusts the position of the light beam constraint component to optimize the telecentricity.

Description

Technical Field

[0001] This invention relates to the field of semiconductor testing technology, specifically to a measurement system, a position determination method, a measurement method, and a storage medium. Background Technology

[0002] In semiconductor manufacturing, image-based overlay (IBO) measurement is commonly used for overlay measurements. This method uses a microscopic imaging system to image the mark under test with high fidelity and low distortion, and then calculates the relevant values ​​using a symmetry algorithm. During measurement, when the depth of focus of the microscopic imaging system is sufficient to simultaneously image the current layer and the preceding layer, the SG (Single Grab) mode is typically used, i.e., imaging both layers of marks simultaneously at a single focal height. However, due to design and manufacturing tolerances and system assembly errors, the microscopic imaging system cannot achieve perfect telecentricity. Imperfect telecentricity leads to a deterioration in measurement TIS (Tool Induced Shift) and TMU (Total Measurement Uncertainty). Summary of the Invention

[0003] To address the problems existing in the prior art, this application provides a measurement system, a position determination method, a measurement method, and a storage medium. By determining the position of the beam constraint component, the telecentricity is optimized, thereby optimizing TIS and TMU. The technical solution is as follows:

[0004] On the one hand, a measurement system is provided, including:

[0005] The stage is used to support the measurement target;

[0006] Light source assembly, used to emit a beam of illumination;

[0007] A beam constraint component is used to spatially constrain the illumination beam. When the beam constraint component is moved, it can change the angular distribution of the illumination beam.

[0008] An imaging optical path assembly includes an image sensor and an objective lens; the imaging optical path assembly is used to perform optical imaging of the measurement target carried on the stage through the objective lens, and to transmit the imaged light signal to the image sensor, the image sensor being used to convert the light signal into an electrical signal;

[0009] A drive assembly for driving the stage to move relative to the objective lens;

[0010] Processor, used for:

[0011] Based on the multiple first displacement data sets and the corresponding multiple second displacement data sets obtained by moving the beam constraint component in the first direction, the first target position of the beam constraint component in the first direction is determined.

[0012] When the beam constraint component is in the first target position, based on multiple third displacement data sets and corresponding multiple fourth displacement data sets obtained by moving the beam constraint component in the second direction, the second target position of the beam constraint component in the second direction is determined, wherein the second direction is perpendicular to the first direction.

[0013] Optionally, the processor is further configured to:

[0014] The beam constraint component is controlled to move in a first direction, such that the beam constraint component is sequentially positioned in multiple different first test positions in the first direction;

[0015] At each first test position, the stage carrying the measurement target and the objective lens are controlled to move relative to each other in the vertical direction to obtain the first displacement data set and the corresponding second displacement data set.

[0016] Optionally, the processor determines a first target position of the beam constraint component in the first direction based on a plurality of first displacement data sets obtained by moving the beam constraint component in the first direction and a corresponding plurality of second displacement data sets, including:

[0017] For each first test position, the centroid is determined based on its corresponding first displacement data set and corresponding second displacement data set;

[0018] Based on multiple telecentricities, the first target position of the beam constraint component in the first direction is determined.

[0019] Optionally, the processor determines the first target position of the beam constraint component in the first direction based on multiple telecentricities, including:

[0020] A first reference curve is obtained based on multiple centroids and the first test positions corresponding to the multiple centroids;

[0021] The first test position corresponding to the smallest centroid in the first reference curve is determined as the first target position.

[0022] Optionally, the measurement target includes multiple measurement modules arranged at intervals. At each first test position, the processor controls the stage carrying the measurement target and the objective lens to move relative to each other in the vertical direction, acquiring a first displacement data set and a corresponding second displacement data set, including:

[0023] Record multiple different first relative distances between the objective lens and the stage in the vertical direction as the first displacement data set;

[0024] For each measurement module: obtain the offset of the imaging position on the image sensor corresponding to each first relative distance as the second displacement data subgroup corresponding to the measurement module;

[0025] The set of multiple second displacement data subgroups is taken as the second displacement data group.

[0026] Optionally, for each first test position, the processor determines the centroid based on its corresponding first displacement data set and corresponding second displacement data set, including:

[0027] For each measurement module: Determine the initial centroid based on the first displacement data group and the second displacement data subgroup corresponding to the measurement module;

[0028] The centroid is determined based on multiple initial centroids.

[0029] Optionally, the processor determines the initial centroid based on the first displacement data group and the second displacement data subgroup corresponding to the measurement module, including:

[0030] For each first relative distance in the first displacement data group: the ratio of the second displacement data corresponding to the first relative distance in the second displacement data subgroup of the measurement module to the first relative distance is determined as the initial sub-centrocentrism;

[0031] The average value of multiple initial sub-centroids is determined as the initial centroid.

[0032] Optionally, before determining the second target position of the beam constraint component in the second direction based on a plurality of third displacement data sets and corresponding plurality of fourth displacement data sets obtained by the movement of the beam constraint component in the second direction, the processor is further configured to:

[0033] When the beam constraint component is in the first target position, the beam constraint component is controlled to move in the second direction, so that the beam constraint component is in a plurality of different second test positions in the second direction in sequence.

[0034] At each second test position, the third displacement data set and its corresponding fourth displacement data set are acquired by controlling the relative movement of the stage carrying the measurement target and the objective lens in the vertical direction.

[0035] Optionally, the processor determines the second target position of the beam constraint component in the second direction based on a plurality of third displacement data sets and corresponding plurality of fourth displacement data sets obtained by the movement of the beam constraint component in the second direction, including:

[0036] For each second test position, a distribution value is determined based on its corresponding third displacement data set and corresponding fourth displacement data set. The distribution value is used to indicate the distribution of the telecentricity vector of the beam constraint component at that second test position.

[0037] Based on multiple distribution values, the second target position of the beam constraint component in the second direction is determined.

[0038] Optionally, the processor determines the second target position of the beam constraint component in the second direction based on multiple distribution values, including:

[0039] Based on the plurality of distribution values ​​and the second test positions corresponding to the plurality of distribution values, a second reference curve is obtained;

[0040] The second test position corresponding to the smallest distribution value in the second reference curve is determined as the second target position.

[0041] Optionally, the measurement target includes multiple measurement modules arranged at intervals. At each second test position, the processor controls the stage carrying the measurement target and the objective lens to move relative to each other in the vertical direction, acquiring a third displacement data set and a corresponding fourth displacement data set, including:

[0042] Record multiple different second relative distances between the objective lens and the stage in the vertical direction as the third displacement data set;

[0043] For each measurement module: the offset component of the imaging position on the image sensor corresponding to each second relative distance is obtained as the fourth displacement data subgroup;

[0044] The set of multiple fourth displacement data subgroups is taken as the fourth displacement data group.

[0045] Optionally, for each second test position, the processor determines a distribution value based on its corresponding third displacement data set and corresponding fourth displacement data set, including:

[0046] For each measurement module: Based on the third displacement data group and the fourth displacement data subgroup corresponding to the measurement module, determine the centroid vector corresponding to the measurement module;

[0047] The distribution value is determined based on the sum of the telecentricity vectors of the multiple measurement modules.

[0048] Optionally, each fourth displacement data in the fourth displacement data group includes a first offset direction component and a second offset direction component. The processor determines the telecentricity vector corresponding to the measurement module based on the third displacement data group and the fourth displacement data subgroup corresponding to the measurement module, including:

[0049] A first correspondence is determined based on the third displacement data group and multiple first offset direction components, and a second correspondence is determined based on the third displacement data group and multiple second offset direction components;

[0050] Fit the first correspondence to determine the first component, and fit the second correspondence to determine the second component;

[0051] The vector formed by the first component and the second component is determined as the telecentricity vector corresponding to the measurement module.

[0052] Optionally, the beam confinement assembly includes an aperture stop.

[0053] On the other hand, a position determination method is provided, applied to a measurement system including a beam constraint component; the method includes:

[0054] Based on the multiple first displacement data sets and the corresponding multiple second displacement data sets obtained by moving the beam constraint component in the first direction, the first target position of the beam constraint component in the first direction is determined.

[0055] When the beam constraint component is in the first target position, based on multiple third displacement data sets and corresponding multiple fourth displacement data sets obtained by moving the beam constraint component in the second direction, the second target position of the beam constraint component in the second direction is determined, wherein the second direction is perpendicular to the first direction.

[0056] On the other hand, a measurement method is provided, the method being applied to a measurement system including a beam constraint component; the method includes:

[0057] According to the position determination method described above, a first target position and a second target position of the beam constraint component are determined, and the beam constraint component is adjusted to the position corresponding to the first target position and the second target position.

[0058] The target to be measured is subjected to overlay measurement.

[0059] On the other hand, a computer-readable storage medium is provided, wherein a computer program is stored therein, and when the computer program is executed by a processor, it implements the steps of the position determination method or measurement method described above.

[0060] On the other hand, a computer program product containing instructions is provided, which, when executed on a computer, cause the computer to perform the steps of the position determination method or measurement method described above.

[0061] The technical solution provided in this application can bring at least the following beneficial effects:

[0062] Based on the first and second displacement data sets, the first target position of the beam constraint component in the first direction is determined. Then, with the beam constraint component in the first target position, the second target position of the beam constraint component in the second direction is determined based on the third and fourth displacement data sets. This allows for precise determination of the beam constraint component's position. Since the position of the beam constraint component determines whether perfect telecentricity can be achieved, adjusting its position optimizes the telecentricity of the measurement system, thus avoiding fixed image shifts due to imperfect telecentricity and optimizing TIS and TMU. Furthermore, the measurement band of the illumination beam can be acquired, allowing for determination of the beam constraint component's position in different bands. This enables telecentricity optimization for different measurement bands, reducing measurement errors between different bands. Attached Figure Description

[0063] Figure 1 This is a schematic diagram of the structure of a measurement system provided in an embodiment of this application;

[0064] Figure 2 This is a schematic diagram of another measurement system provided in an embodiment of this application;

[0065] Figure 3 This is a schematic diagram of another measurement system provided in an embodiment of this application;

[0066] Figure 4 A Kohler lighting method provided in an embodiment of this application;

[0067] Figure 5 A schematic diagram of a measurement target provided for an embodiment of this application;

[0068] Figure 6 A schematic diagram of a first reference curve provided for an embodiment of this application;

[0069] Figure 7 A flowchart illustrating a location determination method provided in an embodiment of this application;

[0070] Figure 8 This is a flowchart of a measurement method provided in an embodiment of this application. Detailed Implementation

[0071] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of this application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to this application are not shown or described in the specification. This is to avoid obscuring the core parts of this application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0072] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0073] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0074] Before providing a detailed explanation of the measurement system, position determination method, and measurement method provided in the embodiments of this application, the application scenarios of the embodiments of this application will be introduced first.

[0075] In semiconductor manufacturing, certain multilayer structures stacked on semiconductors require specific alignment precision (overlay precision) to ensure normal circuit function. IBO (Integrated Bias) is a mainstream overlay measurement method. This method uses a microscopic imaging system to perform high-fidelity, low-distortion imaging of the target mark, and then calculates relevant values ​​using a symmetry algorithm. For different measurement targets and film systems, this microscopic imaging system needs to use different measurement bands to optimize image clarity; commonly used measurement bands cover the spectrum from ultraviolet to near-infrared light. For common measurement targets, there are two parts of the mark located in the current layer and the preceding layer, with the height difference between the two layers determined by the film thickness. In measurement, when the depth of focus of the microscopic imaging system allows for simultaneous imaging of both the current and preceding layers, the SG (Single Grab) mode is typically used. This means that both layers of the mark are imaged simultaneously at a single focusing height. Compared to the DG (Double Grab) mode, which images the two layers of the mark separately, this method achieves faster measurement speeds and reduces errors caused by system drift.

[0076] However, due to factors such as design and manufacturing tolerances and system assembly errors, perfect telecentricity cannot be achieved in microscopic imaging systems. In SG mode, both the current and previous layers typically have some degree of defocus. Since the system's telecentricity is coupled with the amount of defocus, it leads to image shift. This image shift is usually reflected in the measurement TIS in semiconductor metrology processes, and TIS is one of the contributors to TMU (Transmission Measurement Unit). Therefore, imperfect telecentricity of the system will lead to a deterioration in both measurement TIS and TMU. Furthermore, due to process requirements, the measurement band is adjusted according to the type of semiconductor, typically covering the entire visible and near-infrared bands. However, due to chromatic aberration in the system, differences in telecentricity may occur in different bands, thus affecting the measurement results across different bands.

[0077] Based on this, embodiments of this application provide a measurement system capable of optimizing the telecentricity of the measurement system, thereby optimizing TIS and TMU and reducing measurement errors. Furthermore, by optimizing different bands separately, the differences in measurement results across different bands can be reduced.

[0078] Please refer to Figure 1 , Figure 1This is a schematic diagram of a measurement system provided in an embodiment of this application. The measurement system includes: a stage 1 for carrying a measurement target; a light source assembly 2 for emitting an illumination beam; a beam constraint assembly 3 for spatially constraining the illumination beam, which, when moved, can change the angular distribution of the illumination beam; an imaging optical path assembly 4, including an image sensor 41 and an objective lens 42; the imaging optical path assembly 4 is used to perform optical imaging on the measurement target carried by the stage 1 through the objective lens 42, and transmit the imaged light signal to the image sensor 41, which converts the light signal into an electrical signal; a driving assembly 5 for driving the stage 1 and the objective lens 42 to move relative to each other; and a processor 6 for: determining a first target position of the beam constraint assembly 3 in a first direction based on multiple first displacement data sets and corresponding multiple second displacement data sets obtained by moving the beam constraint assembly 3 in a first direction; and, when the beam constraint assembly 3 is in the first target position, determining a second target position of the beam constraint assembly 3 in a second direction based on multiple third displacement data sets and corresponding multiple fourth displacement data sets obtained by moving the beam constraint assembly 3 in a second direction, wherein the second direction is perpendicular to the first direction.

[0079] Among them, the stage 1 can move, and the movement of the stage 1 will drive the measurement target it carries to move. Thus, in the subsequent process, the first displacement data group, the second displacement data group, the third displacement data group and the fourth displacement data group related to the measurement target can be acquired.

[0080] In some embodiments, the stage 1 can move along the scanning direction, thereby causing the measurement target it carries to move along the scanning direction, so that the measurement device can scan the entire surface of the measurement target.

[0081] In some embodiments, the scanning direction can be the X-axis direction, the Y-axis direction, or a planar direction defined by the X-axis and Y-axis (e.g., the horizontal direction or the horizontal plane direction).

[0082] In some embodiments, the stage 1 can move along the optical axis of the objective lens, thereby causing the carried measurement target or reference object to move along the optical axis of the objective lens. For example, the optical axis of the objective lens can be the Z-axis direction (e.g., the vertical direction).

[0083] Therefore, in some embodiments, the stage 1 can move along the Z-axis direction (e.g., the vertical direction) to move the carried measurement target or reference object along the Z-axis direction (e.g., the vertical direction).

[0084] It should be noted that the measurement target in the embodiments of this application can be semiconductor products such as wafers and chips. Since the stacked multi-layer structure needs to meet specific overlay accuracy to ensure the normal function of the circuit, it is necessary to perform overlay measurement to control the quality of the product.

[0085] The light source assembly 2 can emit an illumination beam, which can be projected onto the measurement target carried by the stage 1 after passing through the beam constraint assembly 3 and the objective lens. The light formed by the surface reflection and scattering of the measurement target is then collected by the objective lens and incident on the detection sensor.

[0086] In some embodiments, the light source component 2 may be any one of LED, xenon lamp, mercury lamp, halogen lamp, laser lamp, laser plasma lamp, or laser-driven white light source lamp, so the illumination beam may be white light, colored light, or laser.

[0087] The beam constraint component 3 is positioned after the light source component 2, so that after the light source component 2 emits an illumination beam, the illumination beam can pass through the beam constraint component 3. The beam constraint component 3 can be moved, and when the beam constraint component 3 is moved, the angular distribution of the illumination beam can be changed, thereby changing the angle of the illumination beam on the measurement target.

[0088] In some embodiments, telecentrism is typically quantified as the angle between the principal ray of the illumination beam and the optical axis in object space (or image space). If this angle is 0, then the telecentrism is 0, which is perfect telecentrism; if this angle is not 0, then the telecentrism is not 0, and telecentrism error exists. The principal ray is defined as the ray in the illumination beam that passes through the center of the beam constraint component 3. Therefore, the position of the beam constraint component 3 determines the angle at which the illumination beam passes through the center of the beam constraint component 3 to reach the imaging plane. Thus, the direction of the principal ray depends on the position of the beam constraint component 3; therefore, to achieve perfect telecentrism, the position of the beam constraint component 3 needs to be accurately determined.

[0089] In some embodiments, please refer to Figure 2 The beam constraining component 3 includes an aperture stop 31. The aperture stop 31 can constrain the illumination beam, and therefore, when the aperture stop 31 is moved, the angle of the illumination beam can be changed.

[0090] Additionally, in some embodiments, such as Figure 3 As shown, aperture stop 31 can be aperture stop 311.

[0091] It should be noted that the above description is based on the beam constraint component 3 including the aperture 31. Alternatively, in application, the beam constraint component 3 may be other components. This application does not limit this.

[0092] In some embodiments, the imaging optical path assembly 4 is used to image the measurement target carried by the stage 1. In some specific embodiments, the imaging optical path assembly 4 is used to perform optical imaging of the measurement target carried by the stage 1 through the objective lens 42, and transmit the imaged light signal to the image sensor 41, which is used to convert the light signal into an electrical signal.

[0093] Understandably, the imaging optical path assembly 4 may include other components in addition to the image sensor 41 and the objective lens 42, such as other optical devices disposed in the optical path between the image sensor 41 and the objective lens 42, such as collimating lenses or even filters, beam splitters, etc.

[0094] In some embodiments, the driving component 5 is used to drive the stage 1 and the objective lens 42 to move relative to each other. Specifically, the driving component 5 can drive the stage 1 to move while the objective lens 42 remains stationary, or the driving component 5 can drive the objective lens 42 to move while the stage 1 remains stationary, or the driving component 5 can drive both the stage 1 and the objective lens 42 to move.

[0095] For example, the drive assembly 5 can drive the stage 1 and the objective lens 42 to move relative to each other along the scanning direction. This can be achieved by the drive assembly 5 driving the stage 1 to move in the vertical direction while the objective lens 42 remains stationary, or by the drive assembly 5 driving the objective lens 42 to move in the vertical direction while the stage 1 remains stationary, or by the drive assembly 5 driving the stage 1 to move and driving the objective lens 42 to move so that the two can move relative to each other in the vertical direction.

[0096] In some embodiments, the driving component 5 can also drive the beam constraint component 3 to move. For example, the driving component 5 can drive the beam constraint component 3 to move along the optical axis, or it can drive the beam constraint component 3 to move in a direction perpendicular to the optical axis.

[0097] Among them, the drive component 5 can be implemented based on drive components such as piezoelectric motors, servo motors, and DD motors.

[0098] As described above, achieving perfect telecentricity requires accurately determining the position of the beam constraint component 3. Therefore, the processor 6 needs to determine the first target position of the beam constraint component 3 in the first direction based on multiple first displacement data sets and corresponding multiple second displacement data sets, and determine the second target position of the beam constraint component 3 in the second direction based on multiple third displacement data sets and corresponding multiple fourth displacement data sets obtained by moving the beam constraint component 3 in the second direction.

[0099] In some embodiments, before determining the first target position, the processor 6 needs to acquire multiple first displacement data sets and corresponding multiple second displacement data sets.

[0100] In some embodiments, the processor 6 can control the beam constraint component 3 to move in a first direction, so that the beam constraint component 3 is in a plurality of different first test positions in the first direction in sequence; at each first test position, by controlling the stage 1 carrying the measurement target and the objective lens 42 to move relative to each other in the vertical direction, a first displacement data set and a second displacement data set corresponding to each other are acquired.

[0101] As an example, if the first direction is the optical axis direction, then the processor 6 can control the beam constraint component 3 to move along the optical axis direction, so that the beam constraint component 3 is in multiple different first test positions in the optical axis direction in sequence.

[0102] In some embodiments, please refer to Figure 4 , Figure 4 This is a Kohler illumination method in which a beam constraint component (such as an aperture stop) is placed in a position conjugate to the light source component. Because chromatic aberration may exist between different measurement wavelengths, the position conjugate to the light source will vary depending on the measurement wavelength. Therefore, adjusting the position of the beam constraint component 3 along the optical axis ensures that the illumination beam satisfies the conjugate relationship under different measurement wavelengths. Furthermore, adjusting the beam constraint component 3 along the optical axis maximizes the uniformity of the illumination beam and minimizes the overall telecentricity of the measurement system.

[0103] It should be noted that the above description is based on the first direction as the optical axis direction. Alternatively, in application, the first direction can also be perpendicular to the optical axis direction. This application does not limit this aspect.

[0104] In some embodiments, the telecentricity measurement of the measurement system can be achieved by optical imaging of the measurement target. Therefore, in order to optimize the telecentricity in the subsequent process, the processor 6 can control the stage 1 carrying the measurement target and the objective lens 42 to move relative to each other in the vertical direction when the beam constraint component 3 is in each different first test position. That is, the distance between the measurement target and the objective lens 42 in the vertical direction is changed to obtain the first displacement data set and the second displacement data set corresponding to the first displacement data set.

[0105] Continuing from the above description, since the first displacement data set and the second displacement data set are displacement data sets obtained by the processor 6 controlling the beam constraint component 3 to move in the first direction, the processor 6 can determine the first target position of the beam constraint component 3 in the first direction after determining the first displacement data set and the second displacement data set.

[0106] In some embodiments, in order to determine the precise second target position in subsequent processes, the beam constraint component 3 needs to be positioned at the first target position in the first direction when determining the second target position.

[0107] In some embodiments, before determining the second target position, the processor 6 needs to acquire multiple third displacement data sets and corresponding multiple fourth displacement data sets.

[0108] In some embodiments, when the beam constraint component 3 is in the first target position, the processor 6 can control the beam constraint component 3 to move in the second direction, so that the beam constraint component 3 is in a plurality of different second test positions in the second direction in sequence. Then, at each second test position, by controlling the stage 1 carrying the measurement target and the objective lens 42 to move relative to each other in the vertical direction, a third displacement data set and a fourth displacement data set corresponding to each other are acquired.

[0109] The second direction is perpendicular to the first direction. Therefore, when the first direction is the optical axis direction, the second direction can be a direction perpendicular to the optical axis. When the first direction is perpendicular to the optical axis, the second direction can be a direction perpendicular to the optical axis.

[0110] As an example, if the first direction is the optical axis direction and the second direction is perpendicular to the first direction, the processor 6 can control the beam constraint component 3 to move along the direction perpendicular to the optical axis, so that the beam constraint component 3 is in multiple different second test positions in the direction perpendicular to the optical axis.

[0111] In some embodiments, by adjusting the position of the beam constraint component 3 along a direction perpendicular to the optical axis, the angular distribution of the illumination beam on the surface of the object under test (such as a wafer) can be changed, thereby changing the overall telecentricity of the measurement system.

[0112] Continuing from the above description, similar to the first test position, when the beam constraint component 3 is in each different second test position, it is also necessary to change the vertical distance between the measurement target and the objective lens 42 in order to obtain the third displacement data set and the fourth displacement data set corresponding to the third displacement data set.

[0113] Since the third and fourth displacement data sets are displacement data sets obtained by the processor 6 controlling the beam constraint component 3 to move in the second direction, the processor 6 can determine the second target position of the beam constraint component 3 in the second direction after determining the third and fourth displacement data sets.

[0114] In this embodiment, the processor 6 first determines the first target position of the beam constraint component 3 in the first direction. Then, with the beam constraint component 3 in the first target position, it determines the second target position of the beam constraint component 3 in the second direction. This allows for precise determination of the position of the beam constraint component 3. Since the position of the beam constraint component 3 determines whether perfect telecentricity can be achieved, adjusting the position of the beam constraint component 3 can optimize the telecentricity of the measurement system. This avoids the occurrence of fixed image offsets due to imperfect telecentricity. Image offsets are misread as overlay errors, which increases TIS. As a systematic error, TIS directly contributes to TMU, ultimately leading to TMU deterioration. This achieves optimization of both TIS and TMU.

[0115] In some embodiments, the processor 6 is further configured to acquire the measurement band corresponding to the illumination beam, thereby the first target position and the second target position of the beam constraint component 3 currently determined are the positions of the beam constraint component 3 that can achieve perfect telecentricity under the measurement band.

[0116] In addition, in some embodiments, the processor 6 can also store the correspondence between the measurement band and the position of the beam constraint component 3. Thus, in subsequent processes, if the measurement band of the illumination beam is the measurement band that stores the position of the beam constraint component 3, the position of the beam constraint component 3 can be directly determined from the correspondence, thereby improving measurement efficiency.

[0117] In some embodiments, the processor 6 can acquire the measurement band corresponding to the illumination beam before controlling the beam constraint component 3 to move in the first direction. That is, the processor 6 can initially acquire the measurement band corresponding to the illumination beam. Thus, after acquiring the measurement band, it can first determine whether the position of the beam constraint component 3 corresponding to the same measurement band is stored in the correspondence. If the position of the beam constraint component 3 corresponding to the same measurement band is stored, the stored position of the beam constraint component 3 can be directly determined as the current position where the beam constraint component 3 needs to be. If it is not stored, the steps of determining the first target position and the second target position of the beam constraint component 3 are then executed, thereby reducing the number of repeated executions and improving measurement efficiency.

[0118] It should be noted that the above description assumes that the processor 6 acquires the measurement band corresponding to the illumination beam before controlling the beam constraint component 3 to move in the first direction. Alternatively, in application, the measurement band corresponding to the illumination beam can also be acquired after the second target position of the beam constraint component 3 in the second direction is determined. That is, the measurement band is acquired after the position of the beam constraint component 3 is determined. This application embodiment does not limit this.

[0119] In some embodiments, the measurement band of the illumination beam can be determined based on the results of ARO (Auto Recipe Optimization).

[0120] This application embodiment can determine the position of the beam constraint component 3 under different wavebands by acquiring the measurement waveband of the illumination beam, thereby optimizing the telecentricity for different measurement wavebands and reducing the measurement error between different measurement wavebands.

[0121] Next, we will first describe in detail the process by which the processor 6 determines the first target position of the beam constraint component 3:

[0122] In some embodiments, the measurement target includes a plurality of measurement modules arranged at intervals. At each first test position, the processor 6 can record a plurality of different first relative distances between the objective lens 42 and the stage 1 in the vertical direction as a first displacement data set. Moreover, for each measurement module, the offset of the imaging position on the image sensor 41 corresponding to each first relative distance is obtained as a second displacement data subset. Then, the set of a plurality of second displacement data subsets is used as a second displacement data set to obtain the first displacement data set and the corresponding second displacement data set.

[0123] As an example, the multiple spaced measurement modules included in the measurement target can be as follows: Figure 5 As shown, from Figure 5 As can be seen, the multiple measurement modules in this measurement target are arranged at certain intervals.

[0124] As described above, the processor 6 can control the beam constraint component 3 to move in the first direction, thereby enabling the beam constraint component 3 to be in multiple different first test positions sequentially in the first direction. In order to obtain the first displacement data set and the second displacement data set corresponding to different first test positions in the subsequent process, at each first test position, the processor 6 can control the stage 1 and the objective lens 42 to move relative to each other in the vertical direction, thereby changing the first relative distance between the stage 1 and the objective lens 42 in the vertical direction, and thus changing the object distance, that is, the distance between the target and the objective lens 42 in the vertical direction, and recording multiple different first relative distances between the objective lens 42 and the stage 1 in the vertical direction, and using these multiple different first relative distances as the first displacement data set corresponding to the first test position.

[0125] As an example, assuming the current test position is X, the processor 6 can first control the stage 1 and the objective lens 42 to move relative to each other in the vertical direction, and record multiple different first relative distances as d1X, d2X, d3X, and d4X. Therefore, the set of d1X, d2X, d3X, and d4X can be used as the first displacement data set corresponding to the first test position X. As another example, assuming the current test position is Y, the processor 6 can first control the stage 1 and the objective lens 42 to move relative to each other in the vertical direction, and record multiple different first relative distances as d1Y, d2Y, d3Y, and d4Y. The set of d1Y, d2Y, d3Y, and d4Y can be used as the first displacement data set corresponding to the first test position Y. Thus, it is possible to determine the first displacement data sets corresponding to multiple different first test positions.

[0126] As described above, the measurement target includes measurement modules arranged at intervals. The center position of each measurement module can be optically imaged. Since the center positions of different measurement modules are not the same, the imaging position at different center positions may shift during measurement due to the first relative distance between the objective lens 42 and the stage 1 in the vertical direction. Therefore, for each measurement module, it is necessary to obtain the offset of the imaging position on the image sensor 41 corresponding to each first relative distance as a second displacement data subgroup.

[0127] As an example, suppose there is a measurement module 1 at the first test position X, and the first displacement data group includes d1, d2, d3, and d4. Then, it is necessary to obtain the imaging position offset corresponding to d1, that is, the offset of the imaging position of the measurement module 1 when the first relative distance between the stage 1 and the objective lens 42 in the vertical direction is d1, and this offset is △d1A. Obtain the imaging position offset corresponding to d2, that is, the offset of the imaging position of the measurement module 1 when the first relative distance between the stage 1 and the objective lens 42 in the vertical direction is d2, and this offset is △d2A. And so on, obtain the offset △d3A corresponding to the measurement module 1 when the first relative distance is d3, and obtain the offset △d4A corresponding to the measurement module 1 when the first relative distance is d4. Thus, the set of △d1A, △d2A, △d3A, and △d4A can be used as the fourth displacement data subgroup corresponding to the measurement module 1.

[0128] Similarly, other measurement modules in the measurement target also need to determine their corresponding second displacement data subgroups according to the above steps. As an example, measurement module 2 can use △d1B, △d2B, △d3B, and △d4B as its corresponding second displacement data subgroups, where △d1B is the offset of measurement module 2 at the first relative distance d1; △d2B is the offset of measurement module 2 at the first relative distance d2; △d3B is the offset of measurement module 2 at the first relative distance d3; △d4B is the offset of measurement module 2 at the first relative distance d4, and so on, to determine the second displacement data subgroups corresponding to measurement modules 3, 4, and others.

[0129] In some embodiments, the first relative distance between the stage 1 and the objective lens 42 can be changed at a constant speed, and the image sensor 41 can be triggered to acquire images at certain time intervals during the movement, and the offset corresponding to different first relative distances can be determined from the acquired images.

[0130] In some embodiments, after determining the second displacement data subgroup corresponding to each measurement module at different first test positions, the set of the multiple second displacement data subgroups can be used as the second displacement data group.

[0131] Continuing from the above description, after determining the first displacement data group corresponding to multiple different first test positions and the second displacement data group corresponding to the first displacement data group, the first target position of the beam constraint component 3 in the first direction can be determined based on the multiple first displacement data groups and the multiple second displacement data groups.

[0132] In some embodiments, the processor 6 may determine the first target position of the beam constraint component 3 in the first direction by the following steps (1)-(2);

[0133] (1) For each first test position, the centroid is determined based on its corresponding first displacement data set and corresponding second displacement data set.

[0134] As an example, assuming the current test position is X, the centroid of the first test position X needs to be determined based on the first displacement data set and the second displacement data set corresponding to the first test position X. Similarly, assuming the current test position is Y, the centroid of the first test position Y needs to be determined based on the first displacement data set and the second displacement data set corresponding to the first test position Y.

[0135] In some embodiments, since the imaging positions of different measurement modules have different offsets, the second displacement data subgroups corresponding to different measurement modules may differ. Therefore, in order to determine the accurate telecentricity corresponding to each first test position in the subsequent process, for each measurement module, the processor 6 needs to determine the initial telecentricity corresponding to the measurement module based on the first displacement data group and the second displacement data subgroup corresponding to the measurement module, and then determine the telecentricity based on the multiple initial telecentricities.

[0136] At each first test position, the first displacement data set corresponding to the multiple measurement modules in the measurement target is the same, but the second displacement data subsets corresponding to different measurement modules are different. Therefore, for each of the multiple measurement modules, the processor 6 needs to determine the initial telecentricity corresponding to the measurement module based on the first displacement data set corresponding to the first test position and the second displacement data subset corresponding to the measurement module at the first test position.

[0137] In some embodiments, determining the initial telecentricity based on the first displacement data group and the second displacement data subgroup corresponding to the measurement module includes: for each first relative distance in the first displacement data group: determining the ratio of the second displacement data corresponding to the first relative distance in the second displacement data subgroup of the measurement module to the first relative distance as the initial sub-telecentricity; and then determining the average value of multiple initial sub-telecentricities as the initial telecentricity.

[0138] In other words, each measurement module has a corresponding initial sub-centrocentrism at different first relative distances. To determine the initial sub-centrocentrism, as an example, assume the first displacement data set is d1, d2, d3, and d4, and the second displacement data sub-set of the measurement module is Δd1, Δd2, Δd3, and Δd4. Here, Δd1 is the second displacement data in the second displacement data sub-set of the measurement module corresponding to the first relative distance d1, Δd2 is the second displacement data in the second displacement data sub-set of the measurement module corresponding to the first relative distance d2, Δd3 is the second displacement data in the second displacement data sub-set of the measurement module corresponding to the first relative distance d3, and Δd4 is the second displacement data in the second displacement data sub-set of the measurement module corresponding to the first relative distance d4. Therefore, for each first relative distance in the first displacement data group, its corresponding initial sub-telecentricity can be determined: the initial sub-telecentricity corresponding to the first relative distance d1 is the ratio of Δd1 to d1, the initial sub-telecentricity corresponding to the first relative distance d2 is the ratio of Δd2 to d2, the initial sub-telecentricity corresponding to the first relative distance d3 is the ratio of Δd3 to d3, and the initial sub-telecentricity corresponding to the first relative distance d4 is the ratio of Δd4 to d4. Thus, multiple initial sub-telecentricities corresponding to this measurement module can be obtained.

[0139] In some embodiments, after determining a plurality of initial sub-telecentricities corresponding to the measurement module, in order to improve the accuracy of determining the final determined telecentricity, the average value of the plurality of initial sub-telecentricities can be determined as the initial telecentricity corresponding to the measurement module.

[0140] It should be noted that the above description uses the average of multiple initial sub-centroids as the initial centroid. Alternatively, in application, the median, weighted average, or other values ​​of these multiple initial sub-centroids can also be used to determine the initial centroid. This application does not limit this approach.

[0141] In some embodiments, the plurality of measurement modules can also be divided into different regions to determine the regional telecentricity. As an example, please refer to... Figure 5 It can Figure 5 Measurement modules 1 (marked with the number 1), 2 (marked with the number 2), 5 (marked with the number 5), and 6 (marked with the number 6) are divided into a measurement region. The average of the initial telecentricity corresponding to each of the measurement modules is determined as the regional telecentricity of this region. Similarly, the following can be used... Figure 5 Measurement module 3 (the black-filled box marked with the number 3), measurement module 4 (the black-filled box marked with the number 4), measurement module 7 (the black-filled box marked with the number 7), and measurement module 8 (the black-filled box marked with the number 8) are divided into a measurement area and their corresponding regional telecentricity is determined. Thus, the telecentricity corresponding to each first test position can be determined based on the obtained regional telecentricity.

[0142] Continuing from the previous description, after determining the initial telecentricity corresponding to each of the multiple measurement modules, the telecentricity of each first test position can be determined based on the multiple initial telecentricities.

[0143] In some embodiments, to eliminate measurement noise, the average of the plurality of initial telecentricities can be determined as the telecentricity corresponding to the first test position. As an example, assuming that at the first test position X, the initial sub-telecentricities corresponding to the four measurement modules in the measurement target are t1, t2, t3 and t4 respectively, then the telecentricity corresponding to the first test position X is the average of t1, t2, t3 and t4.

[0144] It should be noted that the above example illustrates the determination of the centroid as the average of the multiple initial centroids. Alternatively, in application, the median, weighted average, or other values ​​among the multiple initial centroids can also be used to determine the centroid. This application does not limit this approach.

[0145] (2) Based on multiple telecentricities, determine the first target position of the beam constraint component 3 in the first direction.

[0146] In some embodiments, the processor 6 may determine the first target position of the beam constraint component 3 in the first direction by the following steps ab;

[0147] a. Based on multiple centroids and the first test positions corresponding to these multiple centroids, a first reference curve is obtained;

[0148] As an example, please refer to Figure 6 , Figure 6 This is a schematic diagram of a first reference curve provided in an embodiment of this application. Figure 6 As can be seen from the data, the first test position corresponding to the centroid T1 is the first test position X, the first test position corresponding to the centroid T2 is the first test position Y, the first test position corresponding to the centroid T3 is the first test position Z, and the first test position corresponding to the centroid T4 is the first test position V.

[0149] b. Determine the first test position corresponding to the smallest centroid in the first reference curve as the first target position.

[0150] As an example, please refer to Figure 6 ,from Figure 6 As can be seen, the centroids from smallest to largest are T1, T2, T3, and T4, meaning that T1 is closest to the perfect centroid (i.e., closest to 0). Therefore, the first test position X corresponding to T1 can be determined as the first target position.

[0151] It should be noted that the above explanation uses the first reference curve to determine the first target position. Alternatively, in application, the first target position can be determined based on multiple centroids in other ways.

[0152] Next, the process by which the processor 6 determines the second target position of the beam constraint component 3 will be described in detail:

[0153] In some embodiments, the measurement target includes multiple measurement modules arranged at intervals. At each second test position, the processor 6 controls the stage 1 carrying the measurement target and the objective lens 42 to move relative to each other in the vertical direction, thereby acquiring a third displacement data set and a corresponding fourth displacement data set. This includes: recording multiple different second relative distances between the objective lens 42 and the stage 1 in the vertical direction as the third displacement data set; and for each measurement module: acquiring the offset component of the imaging position on the image sensor 41 corresponding to each second relative distance as the fourth displacement data sub-set, and then combining the collection of multiple fourth displacement data sub-sets as the fourth displacement data set to obtain the third displacement data set and the corresponding second displacement data set.

[0154] As an example, the multiple spaced measurement modules included in the measurement target can be as follows: Figure 5 As shown, from Figure 5 As can be seen, the multiple measurement modules in this measurement target are arranged at certain intervals.

[0155] As described above, the processor 6 can control the beam constraint component 3 to move in the second direction, thereby enabling the beam constraint component 3 to be in multiple different second test positions in the second direction sequentially. In order to obtain the third displacement data set and the fourth displacement data set corresponding to different second test positions in the subsequent process, at each second test position, the processor 6 can control the stage 1 and the objective lens 42 to move relative to each other in the vertical direction, thereby changing the second relative distance between the stage 1 and the objective lens 42 in the vertical direction, and thus changing the object distance, that is, the distance between the target and the objective lens 42 in the vertical direction, and recording multiple different second relative distances between the objective lens 42 and the stage 1 in the vertical direction, and using these multiple different second relative distances as the third displacement data set corresponding to the second test position.

[0156] As an example, assuming the current test position is U, the processor 6 can first control the stage 1 and the objective lens 42 to move relative to each other in the vertical direction, and record multiple different second relative distances as d1U, d2U, d3U, and d4U. Therefore, the set of d1U, d2U, d3U, and d4U can be used as the third displacement data set corresponding to the second test position U. As another example, assuming the current test position is V, the processor 6 can first control the stage 1 and the objective lens 42 to move relative to each other in the vertical direction, and record multiple different second relative distances as d1V, d2V, d3V, and d4V. Therefore, the set of d1V, d2V, d3V, and d4V can be used as the third displacement data set corresponding to the second test position V. Thus, it is possible to determine the third displacement data sets corresponding to multiple different second test positions.

[0157] As described above, the measurement target includes measurement modules arranged at intervals. The center position of each measurement module can be optically imaged. Since the center positions of different measurement modules are not the same, the imaging position at different center positions may shift during measurement due to the second relative distance between the objective lens 42 and the stage 1 in the vertical direction. Therefore, for each measurement module, it is necessary to obtain the offset component of the imaging position on the image sensor 41 corresponding to each second relative distance as a fourth displacement data subgroup.

[0158] As an example, assuming the current test position is at the second test position U, there is a measurement module 1, and the third displacement data group includes d1, d2, d3, and d4, then it is necessary to obtain the imaging position offset component corresponding to d1, that is, the offset component of the imaging position of the measurement module 1 when the second relative distance between the stage 1 and the objective lens 42 in the vertical direction is d1, and this offset component is (△d1Ax, △d1Ay). Then, obtain the imaging position offset component corresponding to d2, that is, the offset of the imaging position of the measurement module 1 when the second relative distance between the stage 1 and the objective lens 42 in the vertical direction is d2. The offset components are (△d2Ax, △d2Ay), and so on. The offset components (△d3Ax, △d3Ay) corresponding to the measurement module 1 when the second relative distance is d3 are obtained, and the offset components (△d4Ax, △d4Ay) corresponding to the measurement module 1 when the second relative distance is d4 are obtained. Thus, the set of (△d1Ax, △d1Ay), (△d2Ax, △d2Ay), (△d3Ax, △d3Ay) and (△d4Ax, △d4Ay) can be used as the fourth displacement data subgroup corresponding to the measurement module 1.

[0159] Similarly, other measurement modules in the measurement target also need to follow the above steps to determine their corresponding fourth displacement data subgroup. As an example, the fourth displacement data subgroup of measurement module 2 can be (△d1Bx, △d1By), (△d2Bx, △d2By), (△d3Bx, △d3By), and (△d4Bx, △d4By), where (△d1Bx, △d1By) is the offset component of measurement module 2 when the second relative distance is d1; (△d2Bx, △d2By) is the offset component of measurement module 2 when the second relative distance is d2; (△d3Bx, △d3By) is the offset component of measurement module 2 when the second relative distance is d3; (△d4Bx, △d4By) is the offset component of measurement module 2 when the first relative distance is d4, and so on. The fourth displacement data subgroups corresponding to measurement module 3, measurement module 4, and other measurement modules can be determined by analogy.

[0160] In some embodiments, the second relative distance between the stage 1 and the objective lens 42 can be changed at a constant speed, and the image sensor 41 can be triggered to acquire images at certain time intervals during the movement, and the offset components corresponding to different second relative distances can be determined from the acquired images.

[0161] In some embodiments, after determining the fourth displacement data subgroup corresponding to each measurement module at different second test positions, the set of the multiple fourth displacement data subgroups can be used as the fourth displacement data group.

[0162] Continuing from the above description, after determining the third displacement data set corresponding to multiple different second test positions and the fourth displacement data set corresponding to the third displacement data set, the second target position of the beam constraint component 3 in the second direction can be determined based on the multiple third displacement data sets and the multiple fourth displacement data sets.

[0163] In some embodiments, the processor 6 determines the second target position of the beam constraint component 3 in the second direction based on the third displacement data set and the fourth displacement data set, including the following steps (1)-(2):

[0164] (1) For each second test position, a distribution value is determined based on its corresponding third displacement data set and corresponding fourth displacement data set. The distribution value is used to indicate the distribution of the telecentricity vector of the beam constraint component 3 at the second test position.

[0165] As an example, assuming the current test position is the second test position U, the distribution value of the second test position U needs to be determined based on the third displacement data set and the fourth displacement data set corresponding to the second test position U. Similarly, assuming the current test position is the second test position Y, the distribution value of the second test position Y needs to be determined based on the third displacement data set and the fourth displacement data set corresponding to the second test position Y.

[0166] In some embodiments, since the imaging positions of different measurement modules have different offsets, the fourth displacement data subgroups corresponding to different measurement modules may differ. Therefore, in order to determine the accurate distribution value corresponding to each second test position in the subsequent process, for each measurement module, the processor 6 needs to determine the telecentricity vector corresponding to the measurement module based on the third displacement data group and the fourth displacement data subgroup corresponding to the measurement module. Then, the sum of the telecentricity vectors of multiple measurement modules is determined as the distribution value.

[0167] At each second test position, the third displacement data set corresponding to multiple measurement modules in the measurement target is the same, but the fourth displacement data subset corresponding to different measurement modules may be different. Therefore, for each of the multiple measurement modules, the processor 6 needs to determine the telecentricity vector corresponding to the measurement module based on the third displacement data set corresponding to the second test position and the fourth displacement data subset corresponding to the measurement module at the second test position.

[0168] In some embodiments, as can be seen from the above, each fourth displacement data in the fourth displacement data group includes a first offset direction component (such as X-direction offset) and a second offset direction component (such as Y-direction offset). The processor 6 can determine the telecentricity vector corresponding to the measurement module through the following steps ac.

[0169] a. Determine a first correspondence based on the third displacement data set and multiple first offset direction components, and determine a second correspondence based on the third displacement data set and multiple second offset direction components.

[0170] In some embodiments, the first correspondence is used to indicate the relationship between the offset amount in the first offset direction and the change in the second relative distance. That is, by using the third displacement data group and multiple first offset direction components, the corresponding change in the offset amount in the first offset direction can be obtained when the second relative distance changes.

[0171] As an example, suppose the third displacement data group includes d1, d2, d3, and d4, and the multiple first offset direction components are △d1Ax, △d2Ax, △d3Ax, and △d4Ax, respectively. Here, △d1Ax is the component of the first offset direction when the second relative distance is d1, △d2Ax is the component of the first offset direction when the second relative distance is d2, △d3Ax is the component of the first offset direction when the second relative distance is d3, and △d4Ax is the component of the first offset direction when the second relative distance is d4. Then the data points included in the first correspondence are (d1, △d1Ax), (d2, △d2Ax), (d3, △d3Ax), and (d4, △d4Ax).

[0172] In some embodiments, the second correspondence is used to indicate the relationship between the offset of the second offset direction and the change of the second relative distance. That is, by using the third displacement data group and multiple second offset direction components, the corresponding change of the offset of the second offset direction when the second relative distance changes can be obtained.

[0173] As an example, suppose the third displacement data group includes d1, d2, d3, and d4, and the multiple second offset direction components are △d1Ay, △d2Ay, △d3Ay, and △d4Ay, where △d1Ay is the component of the second offset direction at the second relative distance d1, △d2Ay is the component of the second offset direction at the second relative distance d2, △d3Ay is the component of the second offset direction at the second relative distance d3, and △d4Ay is the component of the second offset direction at the second relative distance d4. Then the data points included in the second correspondence are (d1, △d1Ay), (d2, △d2Ay), (d3, △d3Ay), and (d4, △d4Ay).

[0174] b. Fit the first correspondence to determine the first component, and fit the second correspondence to determine the second component.

[0175] In some embodiments, since the offset component obtained from a single measurement contains errors, directly determining the first component based on the first offset direction component corresponding to a single measurement and its corresponding second relative distance, or directly determining the second component based on the second offset direction component corresponding to a single measurement and its corresponding second relative distance, may lead to inaccurate centroid vectors subsequently determined due to noise in the single measurement and the possibility of fixed offsets in the system. Therefore, after determining the first correspondence, it is necessary to fit the first correspondence to determine the first component, and to fit the second correspondence to determine the second component.

[0176] The purpose of fitting the first correspondence is to find a linear relationship that minimizes the error of the multiple data points included in the first correspondence to this linear relationship. The slope of this linear relationship is the first component.

[0177] Similarly, the purpose of fitting the second correspondence is to find a linear relationship that minimizes the error of the multiple data points included in the second correspondence to this linear relationship. The slope of this linear relationship is the second component.

[0178] It should be noted that existing or future technologies can be used to fit the first correspondence and the second correspondence. For example, the existing least squares method can be used to fit the first correspondence to obtain the first component. The fitting process will not be described in detail in the embodiments of this application.

[0179] c. The vector formed by the first and second components is determined as the telecentricity vector corresponding to the measurement module.

[0180] As an example, assuming the first component is determined to be Kx and the second component is determined to be Ky, then (Kx, Ky) can be determined as the telecentricity vector corresponding to the measurement module.

[0181] In some embodiments, each measurement module needs to determine its corresponding telecentricity vector through the above steps ac, thereby obtaining multiple telecentricity vectors.

[0182] After determining the telecentricity vectors corresponding to the multiple measurement modules, in order to determine the distribution of telecentricity at each second test position of the beam constraint component 3, i.e., to determine the telecentricity symmetry, it is also necessary to determine the distribution value corresponding to each test position.

[0183] In some embodiments, the distribution value can be determined based on the sum of the telecentricity vectors of the plurality of measurement modules. As an example, assuming the current location is a second test position U, and the determined telecentricity vectors are (Kx1, Ky1), (Kx2, Ky2), (Kx3, Ky3), and (Kx4, Ky4), then the sum vector of these four telecentricity vectors can be determined first. The sum of Kx1, Kx2, Kx3, and Kx4 is Kx, and the sum of Ky1, Ky2, Ky3, and Ky4 is Ky. Therefore, the sum vector is (Kx, Ky), and the distribution value can be the modulus of the sum vector. Similarly, the distribution values ​​corresponding to other second test positions can be determined using the above steps, thus obtaining the distribution values ​​corresponding to each of the plurality of second test positions.

[0184] In some embodiments, the plurality of measurement modules can also be divided into different regions to determine the regional telecentricity. As an example, please refer to... Figure 5 It can Figure 5 Measurement modules 1, 2, 5, and 6 are divided into a measurement region, and the average value of the distribution values ​​corresponding to each module is determined as the regional distribution value of that region. Similarly, the distribution values ​​of the region can be... Figure 5 Measurement modules 3, 4, 7 and 8 are divided into a measurement area and their corresponding area distribution values ​​are determined. Thus, the distribution value corresponding to each second test position can be determined based on the obtained multiple area distribution values.

[0185] (2) Based on multiple distribution values, determine the second target position of the beam constraint component 3 in the second direction.

[0186] In some embodiments, the smaller the distribution value, the more symmetrical the telecentricity distribution. Therefore, the second test position corresponding to the smallest distribution value can be determined as the second target position of the beam constraint component 3 in the second direction.

[0187] In some embodiments, in order to intuitively determine the second target position, the processor 6 can also obtain a second reference curve based on multiple distribution values ​​and the second test positions corresponding to the multiple distribution values, and then determine the second test position corresponding to the smallest distribution value in the second reference curve as the second target position.

[0188] This embodiment first determines the first target position of the beam constraint component in the first direction based on the first and second displacement data sets. Then, with the beam constraint component in the first target position, the second target position of the beam constraint component in the second direction is determined based on the third and fourth displacement data sets. This allows for precise determination of the beam constraint component's position. Since the position of the beam constraint component determines whether perfect telecentricity can be achieved, adjusting the position of the beam constraint component optimizes the telecentricity of the measurement system, thereby avoiding fixed image shifts due to imperfect telecentricity and thus optimizing TIS and TMU. Furthermore, the measurement band of the illumination beam can be acquired, thereby determining the position of the beam constraint component in different bands. This allows for telecentricity optimization for different measurement bands, reducing measurement errors between different measurement bands.

[0189] Next, a location determination method provided by an embodiment of this application will be explained.

[0190] Figure 7 This is a flowchart illustrating a position determination method provided in an embodiment of this application. The method is applied to a measurement system, which includes a beam constraint assembly. Please refer to... Figure 7 The method includes the following steps:

[0191] Step 701: Based on the multiple first displacement data sets and the corresponding multiple second displacement data sets obtained by moving the beam constraint component in the first direction, determine the first target position of the beam constraint component in the first direction.

[0192] Step 702: When the beam constraint component is in the first target position, based on the multiple third displacement data sets and the corresponding multiple fourth displacement data sets obtained by moving the beam constraint component in the second direction, determine the second target position of the beam constraint component in the second direction, wherein the second direction is perpendicular to the first direction.

[0193] The detailed process of steps 701 to 702 above has been described in detail above and will not be repeated here. Please refer to the relevant content above.

[0194] First, the first target position of the beam constraint component in the first direction is determined based on the first and second displacement data sets. Then, with the beam constraint component in the first target position, the second target position of the beam constraint component in the second direction is determined based on the third and fourth displacement data sets. This allows for precise determination of the beam constraint component's position. Since the position of the beam constraint component determines whether perfect telecentricity can be achieved, adjusting the position of the beam constraint component can optimize the telecentricity of the measurement system, thereby avoiding fixed image offsets caused by imperfect telecentricity and thus optimizing TIS and TMU.

[0195] Figure 8 This is a flowchart of a measurement method provided in an embodiment of this application. The method is applied to a measurement system, which includes a beam constraint component. Please refer to... Figure 8 The method includes the following steps:

[0196] Step 801: Determine the first target position and the second target position of the beam constraint component according to any of the above embodiments, and adjust the beam constraint component to the position corresponding to the first target position and the second target position.

[0197] Step 802: Perform overlay measurement on the target to be tested.

[0198] It should be noted that existing or future technologies can be used to perform overlay measurement on the target under test, but this application will not elaborate on this aspect in the embodiments.

[0199] The embodiments of this application optimize the position of the beam constraint component to achieve perfect telecentricity, thereby improving the accuracy of the measurement.

[0200] Those skilled in the art will understand that all or part of the functions of the various methods in the above embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, which may include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to achieve the above functions. For example, the program can be stored in the memory of a device, and when the program in the memory is executed by the processor, all or part of the above functions can be achieved. In addition, when all or part of the functions in the above embodiments are implemented by computer programs, the program can also be stored in a server, another computer, disk, optical disk, flash drive, or external hard drive, etc., and can be downloaded or copied to the memory of a local device, or the system of the local device can be updated. When the program in the memory is executed by the processor, all or part of the functions in the above embodiments can be achieved.

[0201] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A measurement system, characterized in that, include: The stage is used to support the measurement target; Light source assembly, used to emit a beam of illumination; A beam constraint component is used to spatially constrain the illumination beam. When the beam constraint component is moved, it can change the angular distribution of the illumination beam. An imaging optical path assembly includes an image sensor and an objective lens; the imaging optical path assembly is used to perform optical imaging of the measurement target carried on the stage through the objective lens, and to transmit the imaged light signal to the image sensor, the image sensor being used to convert the light signal into an electrical signal; A drive assembly for driving the stage to move relative to the objective lens; Processor, used for: Based on the multiple first displacement data sets and the corresponding multiple second displacement data sets obtained by moving the beam constraint component in the first direction, the first target position of the beam constraint component in the first direction is determined. When the beam constraint component is in the first target position, based on multiple third displacement data sets and corresponding multiple fourth displacement data sets obtained by moving the beam constraint component in the second direction, the second target position of the beam constraint component in the second direction is determined, wherein the second direction is perpendicular to the first direction.

2. The measurement system as described in claim 1, characterized in that, Before determining the first target position of the beam constraint component in the first direction based on multiple first displacement data sets and corresponding multiple second displacement data sets obtained by the beam constraint component moving in the first direction, the processor is further configured to: The beam constraint component is controlled to move in a first direction, such that the beam constraint component is sequentially positioned in multiple different first test positions in the first direction; At each first test position, the stage carrying the measurement target and the objective lens are controlled to move relative to each other in the vertical direction to obtain the first displacement data set and the corresponding second displacement data set.

3. The measurement system as described in claim 2, characterized in that, The processor determines a first target position of the beam constraint component in the first direction based on multiple first displacement data sets and corresponding multiple second displacement data sets obtained by moving the beam constraint component in the first direction, including: For each first test position, the centroid is determined based on its corresponding first displacement data set and its corresponding second displacement data set; Based on multiple telecentricities, the first target position of the beam constraint component in the first direction is determined.

4. The measurement system as described in claim 3, characterized in that, The processor determines the first target position of the beam constraint component in the first direction based on multiple telecentricities, including: A first reference curve is obtained based on multiple centroids and the first test positions corresponding to the multiple centroids; The first test position corresponding to the smallest centroid in the first reference curve is determined as the first target position.

5. The measurement system as described in claim 4, wherein the measurement target comprises a plurality of measurement modules arranged at intervals, and the processor, at each first test position, controls the stage carrying the measurement target and the objective lens to move relative to each other in the vertical direction to acquire a first displacement data set and a second displacement data set corresponding to each other, including: Record multiple different first relative distances between the objective lens and the stage in the vertical direction as the first displacement data set; For each measurement module: obtain the offset of the imaging position on the image sensor corresponding to each first relative distance as the second displacement data subgroup corresponding to the measurement module; The set of multiple second displacement data subgroups is taken as the second displacement data group.

6. The measurement system as described in claim 5, characterized in that, For each first test position, the processor determines the centroid based on its corresponding first displacement data set and corresponding second displacement data set, including: For each measurement module: Determine the initial centroid based on the first displacement data group and the second displacement data subgroup corresponding to the measurement module; The centroid is determined based on multiple initial centroids.

7. The measurement system as described in claim 6, characterized in that, The processor determines the initial centroid based on the first displacement data group and the second displacement data subgroup corresponding to the measurement module, including: For each first relative distance in the first displacement data group: the ratio of the second displacement data corresponding to the first relative distance in the second displacement data subgroup of the measurement module to the first relative distance is determined as the initial sub-centrocentrism; The average value of multiple initial sub-centroids is determined as the initial centroid.

8. The measurement system as described in claim 1, characterized in that, Before determining the second target position of the beam constraint component in the second direction based on multiple sets of third displacement data and corresponding multiple sets of fourth displacement data obtained by the movement of the beam constraint component in the second direction, the processor is further configured to: When the beam constraint component is in the first target position, the beam constraint component is controlled to move in the second direction, so that the beam constraint component is in a plurality of different second test positions in the second direction in sequence. At each second test position, the third displacement data set and its corresponding fourth displacement data set are acquired by controlling the relative movement of the stage carrying the measurement target and the objective lens in the vertical direction.

9. The measurement system as described in claim 8, characterized in that, The processor determines the second target position of the beam constraint component in the second direction based on multiple sets of third displacement data and corresponding multiple sets of fourth displacement data obtained by the movement of the beam constraint component in the second direction, including: For each second test position, a distribution value is determined based on its corresponding third displacement data set and corresponding fourth displacement data set. The distribution value is used to indicate the distribution of the telecentricity vector of the beam constraint component at that second test position. Based on multiple distribution values, the second target position of the beam constraint component in the second direction is determined.

10. The measurement system as described in claim 9, characterized in that, The processor determines the second target position of the beam constraint component in the second direction based on multiple distribution values, including: Based on the plurality of distribution values ​​and the second test positions corresponding to the plurality of distribution values, a second reference curve is obtained; The second test position corresponding to the smallest distribution value in the second reference curve is determined as the second target position.

11. The measurement system as described in claim 10, characterized in that, The measurement target includes multiple measurement modules arranged at intervals. At each second test position, the processor controls the stage carrying the measurement target and the objective lens to move relative to each other in the vertical direction, acquiring a third displacement data set and a corresponding fourth displacement data set, including: Record multiple different second relative distances between the objective lens and the stage in the vertical direction as the third displacement data set; For each measurement module: the offset component of the imaging position on the image sensor corresponding to each second relative distance is obtained as the fourth displacement data subgroup; The set of multiple fourth displacement data subgroups is taken as the fourth displacement data group.

12. The measurement system as described in claim 11, characterized in that, For each second test position, the processor determines a distribution value based on its corresponding third displacement data set and corresponding fourth displacement data set, including: For each measurement module: Based on the third displacement data group and the fourth displacement data subgroup corresponding to the measurement module, determine the centroid vector corresponding to the measurement module; The distribution value is determined based on the sum of the telecentricity vectors of the multiple measurement modules.

13. The measurement system as described in claim 12, characterized in that, Each fourth displacement data in the fourth displacement data group includes a first offset direction component and a second offset direction component. The processor, based on the third displacement data group and the fourth displacement data subgroup corresponding to the measurement module, determines the telecentricity vector corresponding to the measurement module, including: A first correspondence is determined based on the third displacement data group and multiple first offset direction components, and a second correspondence is determined based on the third displacement data group and multiple second offset direction components; Fit the first correspondence to determine the first component, and fit the second correspondence to determine the second component; The vector formed by the first component and the second component is determined as the telecentricity vector corresponding to the measurement module.

14. The measurement system as described in claim 1, characterized in that, The beam confinement assembly includes an aperture stop 31.

15. A method for determining a location, characterized in that, The method is applied to a measurement system, the measurement system including a beam constraint assembly; the method includes: Based on the multiple first displacement data sets and the corresponding multiple second displacement data sets obtained by moving the beam constraint component in the first direction, the first target position of the beam constraint component in the first direction is determined. When the beam constraint component is in the first target position, based on multiple third displacement data sets and corresponding multiple fourth displacement data sets obtained by moving the beam constraint component in the second direction, the second target position of the beam constraint component in the second direction is determined, wherein the second direction is perpendicular to the first direction.

16. A measurement method, characterized in that, The method is applied to a measurement system, the measurement system including a beam constraint component; the method includes: According to the method of claim 15, a first target position and a second target position of the beam constraint component are determined, and the beam constraint component is adjusted to a position corresponding to the first target position and the second target position; The target to be measured is subjected to overlay measurement.

17. A computer-readable storage medium, characterized in that, The medium stores a computer program that can be executed by a processor to implement the method as described in any one of claims 15-16.

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