Alignment mark structure with moire fringe, detection method and system

Abstract

The application discloses a registration mark structure with moire fringes, a detection method and a system, and relates to the technical field of precise optical measurement. The registration mark structure comprises a first registration mark structure and a second registration mark structure arranged in pairs, wherein a first grating area and a fourth grating area along a first direction, a second grating area and a fifth grating area along a second direction, and a third grating area and a sixth grating area of a third direction with a first direction and a second direction projection component are arranged; and multi-direction moire fringes are formed by superimposing corresponding grating areas. The detection method comprises the following steps: detecting a moire fringe image, determining a first displacement, a second displacement and a third displacement; and utilizing additional measurement information provided by the third displacement to verify or jointly calculate the displacements based on the projection relationship between the first displacement and the second displacement. The application provides additional direction constraint information by utilizing the third direction grating, and improves the reliability and stability of the registration measurement result.

Description

Technical Field

[0001] This application relates to the field of precision optical measurement technology, and more specifically, to alignment mark structures with moiré fringes, detection methods, and systems. Background Technology

[0002] In wafer bonding, 3D advanced packaging and photolithography overlay processes, precise alignment of the upper and lower layers is required. Existing alignment technologies typically include traditional image-based alignment, geometric mark alignment based on cross or frame patterns, and moiré fringe alignment based on periodic grating superposition.

[0003] Existing moiré fringe alignment marker structures commonly include single-direction dual-grating structures and flip-type centrosymmetric grating structures. These structures have the following problems: First, single-direction gratings mainly respond to displacement in one direction, and their ability to express two-dimensional displacement components is limited. Often, multiple independent markers or an expanded imaging field of view are needed to obtain complete two-dimensional displacement information. Second, some improved schemes use mutually orthogonal X-direction and Y-direction gratings to simultaneously acquire displacement in two directions. However, in practical applications, the alignment region is often affected by factors such as particle contamination, photoresist inhomogeneity, and local signal distortion, leading to unreliable measurement results from one direction of the grating. The system may then treat erroneous displacement values ​​as valid data output and use them for subsequent alignment control, thereby affecting alignment accuracy and product yield.

[0004] Therefore, how to verify the detection results of the alignment mark structure and improve the detection accuracy and precision of the system has become an urgent problem to be solved. Summary of the Invention

[0005] This application provides an alignment mark structure, detection method, and system with moiré fringes, relating to the field of precision optical measurement technology. By setting an alignment mark structure, two-dimensional alignment measurement is achieved while providing an independent cross-verification channel for the measurement results, overcoming the defect of orthogonal grating schemes that easily output unreliable displacement results when local signal distortion occurs. The specific technical solution is as follows: In a first aspect, a alignment mark structure with moiré fringes is provided. This alignment mark structure is applied in an optical inspection system, which includes a device under test (DUT). The DUT has a first substrate and a second substrate disposed along the light propagation path in the optical inspection system. The alignment mark structure includes a first alignment mark structure disposed on the first substrate and a second alignment mark structure disposed on the second substrate. The first and second alignment mark structures are arranged in pairs along the light propagation path. The first alignment mark structure includes a first grating region, a second grating region, and a third grating region. Grating lines in the first grating region are arranged along a first direction, grating lines in the second grating region are arranged along a second direction, and grating lines in the third grating region are arranged along a third direction. The third direction has projection components of the first and second directions. The second alignment mark structure includes a fourth grating region corresponding to the first grating region, a fifth grating region corresponding to the second grating region, and a sixth grating region corresponding to the third grating region. When the second alignment mark structure and the first alignment mark structure are superimposed, the corresponding grating regions superimpose to form moiré fringes.

[0006] Secondly, a method for detecting alignment mark structures with moiré fringes is provided, applied to the host equipment of an optical inspection system. The optical inspection system includes: a light-emitting device, an optical inspection device, a device under test, and the host equipment; an optical path for light propagation is provided between the light-emitting device and the optical inspection device; the device under test includes a first substrate and a second substrate, which are disposed on the optical path and have an alignment mark structure as described in the first aspect. The alignment mark structure includes: a first alignment mark structure, a second alignment mark structure, a first grating region, a second grating region, a third grating region, a fourth grating region, a fifth grating region, and a sixth grating. The detection method includes: acquiring a moiré fringe image formed by superimposing a first alignment mark structure and a second alignment mark structure in the propagation direction of the optical path based on an optical detection device; acquiring a first displacement determined by superimposing a first grating region and a fourth grating region, a second displacement determined by superimposing a second grating region and a fifth grating region, and a third displacement determined by superimposing a third grating region and a sixth grating region based on the moiré fringe image; the third displacement along the third direction has projection components of the first displacement along the first direction and the second displacement along the second direction; verifying the first displacement and the second displacement based on the third displacement to obtain a verification result; and outputting the verification result.

[0007] It should be noted that the third-direction moiré fringes and their corresponding third displacement generated by the superposition of the third and sixth grating regions can be used not only for cross-validation of the first and second displacements, but also for joint calculation of actual displacements, correction or fitting reconstruction of alignment detection results, and detection and compensation of rotational mismatch of the marked structure. This application does not limit the specific use of the third-direction displacement information.

[0008] Thirdly, a system for detecting alignment mark structures with moiré fringes is provided, comprising: a light-emitting device; an optical detection device, wherein an optical path for light propagation is provided between the light-emitting device and the optical detection device; a device under test, comprising a first substrate and a second substrate, the first substrate and the second substrate being disposed on the optical path, having an alignment mark structure as described in the first aspect, the alignment mark structure comprising: a first alignment mark structure, a second alignment mark structure, a first grating region, a second grating region, a third grating region, a fourth grating region, a fifth grating region, and a sixth grating region; and a host device, comprising the following modules: an image acquisition module, used to acquire images based on the optical detection device. A moiré fringe image formed by superimposing a first alignment mark structure and a second alignment mark structure in the propagation direction of the optical path; a displacement determination module, used to obtain a first displacement determined by superimposing a first grating region and a fourth grating region, a second displacement determined by superimposing a second grating region and a fifth grating region, and a third displacement determined by superimposing a third grating region and a sixth grating region based on the moiré fringe image; the third displacement along the third direction has projection components of the first displacement along the first direction and the second displacement along the second direction; a displacement verification module, used to verify the first displacement and the second displacement based on the third displacement to obtain a verification result; and a control output module, used to output the verification result.

[0009] Existing moiré fringe alignment techniques typically obtain displacement components in two directions using orthogonal gratings. The alignment mark structure of this application is applied in an optical inspection system. The optical inspection system includes a device under test (DUT), which has a first substrate and a second substrate disposed along the light propagation path. The alignment mark structure includes a first alignment mark structure disposed on the first substrate and a second alignment mark structure disposed on the second substrate. The first and second alignment mark structures are arranged in pairs along the light propagation path. The first alignment mark structure includes a first grating region, a second grating region, and a third grating region. The grating lines in the first grating region are arranged along a first direction, the grating lines in the second grating region are arranged along a second direction, and the grating lines in the third grating region are arranged along a third direction. The third direction has projection components of both the first and second directions. The second alignment mark structure includes a fourth grating region corresponding to the first grating region, a fifth grating region corresponding to the second grating region, and a sixth grating region corresponding to the third grating region. When the second alignment mark structure and the first alignment mark structure are superimposed, the corresponding grating regions overlap to form moiré fringes. This application's solution adds a third grating region with projection components in the first and second directions to the marker structure, so that the resulting moiré fringes provide a third displacement containing composite projection information of the first and second displacements. Based on the consistency of the projection of this third displacement with the first and second displacements, cross-validation of orthogonal measurement results can be performed. This is beneficial in cases of abnormal conditions such as local marker contamination, insufficient image contrast, or unidirectional grating signal distortion, by promptly identifying unreliable displacement data through deviation verification, avoiding alignment failure due to misuse of incorrect displacement values, and overall improving the stability, reliability, and automation level of alignment measurement. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the optical detection system and alignment measurement optical path provided in the embodiments of this application; Figure 2 This is a schematic diagram illustrating the upper and lower layer arrangement and superposition relationship of the first alignment marker structure and the second alignment marker structure provided in the embodiments of this application; Figure 3 This is a schematic diagram of the multi-directional grating moiré fringe alignment mark structure provided in the embodiments of this application; Figure 4 This is a schematic diagram illustrating the principle of moiré fringe formation provided in the embodiments of this application; Figure 5 This is a schematic diagram of the stripe change after displacement in the first direction, provided in an embodiment of this application; Figure 6 This is a schematic diagram of the stripe change after displacement in the second direction, provided in an embodiment of this application; Figure 7 This is a flowchart of a detection method with a moiré fringe alignment marker structure provided in an embodiment of this application; Figure 8 This is a schematic diagram of the first-direction stripes and the signal extraction result after image processing provided in the embodiments of this application; Figure 9 This is a schematic diagram of the experimental signal extraction for different displacement conditions provided in the embodiments of this application; Figure 10 This is a schematic diagram showing the projection relationship between the first and second displacement components in a third direction, as provided in the embodiments of this application. Figure 11 This is a schematic diagram of a detection system with a moiré fringe alignment mark structure provided in an embodiment of this application. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0013] Example 1: Alignment marking structure of multi-directional moiré fringes.

[0014] Figure 1 This is a schematic diagram of the optical detection system and alignment measurement optical path provided in the embodiments of this application. Figure 1 As shown, the optical inspection system includes a light-emitting device, an optical inspection device, a device under test (DUT), and a host device (not shown in the figure). The light-emitting device uses an infrared laser emitter (NIR Laser) 1 as a near-infrared light source, which can emit near-infrared light capable of penetrating silicon-based wafers. The optical inspection device includes an infrared camera (NIR Camera) 2, a tube lens 3, an objective lens 4, an aperture 5, and a laser beam expander 6. An optical path 7 for light propagation is formed between the light-emitting device and the optical inspection device. That is, the infrared laser emitter 1, infrared camera 2, tube lens 3, objective lens 4, aperture 5, and laser beam expander 6 together constitute the optical path 7 that transmits light through the wafer. The DUT is placed on this optical path 7, and the light passes through the DUT via the optical path 7 and is captured by the infrared camera 2.

[0015] In this embodiment, the device under test includes a first substrate 8 (such as a first wafer) and a second substrate 9 (such as a second wafer). The first substrate 8 is fixedly disposed on the optical path 7, and the second substrate 9 is supported by a programmable motorized stage 10, enabling the second wafer to be finely adjusted. The first substrate 8 and the second substrate 9 are arranged parallel to each other along the optical path propagation direction in a bonding posture. The first substrate 8 has a first alignment mark structure 81 at the point where light passes through, and the second substrate 9 has a second alignment mark structure 91 at the point where light passes through.

[0016] Figure 2 This is a schematic diagram illustrating the upper and lower layer arrangement and superposition relationship of the first alignment marker structure and the second alignment marker structure provided in the embodiments of this application. For example... Figure 2 As shown, the first substrate 8 is a first wafer (Wafer 1), and a first alignment mark structure 81 (Mark 1) is prepared on the surface of the first wafer. The second substrate 9 is a second wafer (Wafer 2), and a second alignment mark structure 91 (Mark 2) is prepared on the surface of the second wafer. The first alignment mark structure 81 and the second alignment mark structure 91 are aligned in a plane perpendicular to the optical path direction.

[0017] In the embodiments of this application, each alignment mark structure is composed of periodic grating lines. The grating lines can be metal lines, dielectric lines, etched trenches, phase-type structures, transmittance modulation structures, or reflectance modulation structures, and are fabricated by processes such as photolithography and metal stripping, and have good absorption / reflection contrast in the near-infrared band.

[0018] Figure 3 This is a schematic diagram of the multi-directional grating moiré fringe alignment mark structure provided in an embodiment of this application. For example... Figure 3 As shown, taking the first alignment mark structure 81 as an example, the first alignment mark structure 81 includes three functional regions: a first grating region arranged along a first direction (denoted as the X direction), a second grating region arranged along a second direction (denoted as the Y direction), and a third grating region arranged along a third direction (denoted as the Y direction). Figure 3 The third grating region is arranged at a 45° angle. Correspondingly, the second alignment mark structure 91 also includes a fourth grating region arranged along the X direction, a fifth grating region arranged along the Y direction, and a sixth grating region arranged at a 45° angle.

[0019] In this embodiment, to ensure that moiré fringes in three directions can be synchronously captured by the optical detection device within the same imaging field of view, the relative positions of each grating region within the first alignment mark structure region, and their corresponding positions within the second alignment mark structure region, are pre-designed based on the camera's field of view. That is, based on the imaging field of view of the optical detection device, the positions of the first, second, and third grating regions within the first alignment mark structure region, and the positions of the fourth, fifth, and sixth grating regions within the second alignment mark structure region, are determined, so that the corresponding grating regions superimpose to form moiré fringes that are captured by the same imaging field of view of the optical detection device. Figure 3 As shown, the alignment mark structure arranges the X-direction grating, Y-direction grating, and 45° oblique grating in a ring within a compact area with the center of the alignment mark structure as the reference, in order to ensure that the moiré fringes of the three grating areas superimposed can be completely captured within the same camera field of view.

[0020] In this application, the specific layout of the grating regions is not strictly limited. The first, second, and third grating regions can be arranged with the center of the first alignment mark structure as a reference, for example, using any one of the following arrangements: circular, quadrant, or radial. The arrangement of the fourth, fifth, and sixth grating regions corresponds one-to-one with the first, second, and third grating regions in the first alignment mark structure. By compactly arranging the multi-directional grating regions around the mark center, more measurement directions can be integrated within a limited alignment mark area, while ensuring that multiple sets of moiré fringes generated by superposition fall within the same imaging field of view of the optical detection device.

[0021] In some embodiments, the first, second, and third grating areas can be arranged in a quadrant layout, that is, the marking area is divided into four quadrants, with each grating area occupying three quadrants, and the grating lines of each area arranged along the corresponding direction. In other embodiments, a radial arrangement can also be used, that is, each grating area is arranged sequentially along a ray direction with the center of the mark as the origin. These layout methods can all achieve compact integration of multi-directional gratings and all fall within the protection scope of this application.

[0022] In some implementations, a seventh grating region can be added to the first alignment mark structure, arranged along the fourth direction (e.g., obliquely at 135°), and a corresponding eighth grating region can be set in the second alignment mark structure. The two are superimposed to form moiré fringes along the 135° direction, further increasing the number of verification channels.

[0023] In some implementations, the third direction includes multiple oblique directions, not limited to a 45° oblique arrangement. The third direction can be set to 30°, 60°, 120° or other gratings that are not parallel to the X or Y direction, as long as the grating of the third direction can provide additional displacement projection information different from the X and Y directions.

[0024] Figure 4 This is a schematic diagram illustrating the principle of moiré fringe formation provided in an embodiment of this application. For example... Figure 4 As shown, the corresponding grating regions in the first alignment mark structure 81 and the second alignment mark structure 91 are designed to have similar but not identical periods in order to form moiré fringes that are sensitive to minute displacements.

[0025] In this embodiment of the application, the periodic grating lines of the grating region (i.e., the first grating region, the second grating region, or the third grating region) in the first alignment mark structure 81 are configured with a first period (e.g., 9). In the second alignment marker structure 91, the periodic grating lines corresponding to the grating region (i.e., the fourth, fifth, or sixth grating region, corresponding to the first, second, or third grating region) are configured as the second period (e.g., 10). When near-infrared light passes through the first alignment mark structure 81 and the second alignment mark structure 91 in sequence, the upper and lower grating regions are superimposed on the optical path. Due to the difference between the first period and the second period, the transmission intensity of the superimposed region forms a low-frequency moiré fringe pattern with alternating bright and dark areas.

[0026] For example, Figure 4 Taking the first grating region and the fourth grating region arranged along the first direction as an example, the first period of the grating lines in the first grating region and the second period of the grating lines in the fourth grating region 9 respectively and 10 The periodicity of the moiré fringes produced by superposition It can be calculated to be approximately 90. The resulting moiré fringe direction is consistent with the arrangement direction of the grid lines before superposition, and the moiré fringe period is... Much larger than the first cycle Or the second cycle This allows the minute relative displacement between the first and second substrates along the first direction to be amplified into a phase shift of moiré fringes. Similarly, moiré fringes are generated by superimposing the second and fifth grating regions arranged along the second direction, and the third and sixth grating regions arranged along the third direction, in the same manner. These fringes are used to detect the relative displacement between the first and second substrates along the second direction, and to verify the relative displacement between the first and second directions, respectively. This optical modulation difference is not limited to a period difference, but can also be at least one of a phase difference, local offset, linewidth difference, duty cycle difference, or angular difference.

[0027] Figure 5 This is a schematic diagram of the stripe change after displacement in the first direction, provided in an embodiment of this application; Figure 6 This is a schematic diagram of the stripe change after displacement in the second direction, provided in an embodiment of this application; Figure 5 and Figure 6 The changes in moiré fringes after the first and second base layers move in the first and second directions can be shown respectively.

[0028] In this embodiment, when the detection system detects a first substrate (such as a first wafer) and a second substrate (such as a second wafer), the light-emitting device first generates near-infrared illumination. After the light passes through the first and second wafers along the optical path, it carries the superimposed information of two alignment marker structures into the infrared camera. The infrared camera acquires a moiré fringe image containing three superimposed regions: a first superimposed region formed by the superposition of a first grating region and a fourth grating region (including moiré fringes in the X direction), a second superimposed region formed by the superposition of a second grating region and a fifth grating region (including moiré fringes in the Y direction), and a third superimposed region formed by the superposition of a third grating region and a sixth grating region (including moiré fringes in the 45° direction). The relative positions of each grating region on the wafer are fixed, and the imaging positions of the three superimposed regions on the camera sensor are also fixed and within the same frame, thus achieving synchronous capture.

[0029] In this embodiment, the moiré fringes generated by the superposition of the third and sixth grating regions are used to obtain displacement information in the third direction. This third-direction displacement can be used to verify the consistency of the projection of the first and second displacements, or it can serve as an additional measurement channel to participate in fitting the actual displacement, or it can be used to identify and compensate for unidirectional measurement errors caused by local defects in the markings, thereby further improving the robustness and accuracy of the measurement system.

[0030] Example 2: Method for detecting alignment marker structure of multi-directional moiré fringes.

[0031] This embodiment details the method flow for displacement detection and cross-validation using the alignment mark structure of Embodiment 1. This method is executed by a host device, which acquires a moiré fringe image from an infrared camera and verifies the detection results through image processing and displacement calculation steps. Specifically, the host device executes the detection method as follows: based on an optical detection device, it acquires a moiré fringe image formed by the superposition of a first alignment mark structure and a second alignment mark structure along the propagation direction of the optical path; based on the moiré fringe image, it acquires a first displacement determined by the superposition of a first grating region and a fourth grating region, a second displacement determined by the superposition of a second grating region and a fifth grating region, and a third displacement determined by the superposition of a third grating region and a sixth grating region; it verifies the first and second displacements based on the third displacement to obtain a verification result; and it outputs the verification result.

[0032] Figure 7 This is a flowchart of a detection method with a moiré fringe alignment marker structure provided in an embodiment of this application, as shown below. Figure 7 As shown, the detection method includes the following steps S101-S105: S101, Image Preprocessing.

[0033] In this embodiment, three superimposed sub-images can be extracted from the moiré fringe image, and an image processing flow can be performed. The image processing flow includes at least extracting fringe features from the moiré fringe image. For example, by using a two-dimensional Fourier transform, a bandpass filter is used in the frequency domain to retain the frequency components corresponding to the moiré fringe period, filter out high-frequency grating noise and low-frequency background inhomogeneity, and then an inverse Fourier transform is performed to obtain the enhanced fringe image.

[0034] S102, Stripe parameter extraction.

[0035] In the embodiments of this application, Figure 8 This is a schematic diagram of the first-direction stripes and the signal extraction result after image processing provided in the embodiments of this application, as shown below. Figure 8 As shown, taking the first superimposed region in the first direction (i.e., the X direction) as an example, the light intensity is detected along the direction perpendicular to the moiré fringes to obtain a one-dimensional grayscale distribution curve. The horizontal axis of this grayscale distribution curve represents the pixel distance from the origin in the image, and the vertical axis represents the light intensity. The envelope of the grayscale distribution curve approximates a sine wave. By employing methods such as sine function fitting or Fast Fourier Transform (FFT) phase extraction, the first optical modulation difference of the current fringe is determined, including its phase, peak position, and fringe centerline position. Similarly, the second optical modulation difference is extracted from the superimposed region in the second direction (i.e., the Y direction), and the third optical modulation difference is extracted from the superimposed region in the third direction (i.e., the 45° oblique direction).

[0036] S103, Displacement Calculation.

[0037] In this embodiment, the phase change of the moiré fringes is related to the relative displacement of the first alignment mark structure and the second alignment mark structure. For example, assuming each phase in the initial alignment state is a reference phase (which can be pre-calibrated or obtained from a reference image), the displacement components in the current state are calculated to obtain the first displacement. Correspondingly, the second displacement can be calculated. and the third displacement .

[0038] In the embodiments of this application, Figure 9 This is a schematic diagram of the experimental signal extraction for different displacement conditions provided in the embodiments of this application, as shown below. Figure 9 As shown, the extracted signals have different characteristics for different displacement conditions. The horizontal axis in the figure represents the distance from the origin (pixel), and the vertical axis represents the light intensity (...). The figure shows the signals of the extracted grayscale distribution curves under displacements of 0 nm, 100 nm, and 200 nm. By analyzing the optical modulation differences of different signals (such as the center line position), the relative displacement relationship between the first and second alignment marker structures is established, which is then used to calculate the first displacement. Second displacement and the third displacement For example, the displacement is obtained by multiplying the phase change of the moiré fringes of the corresponding superimposed region by a calibration factor, which is related to the equivalent period of the moiré fringes of the corresponding grating.

[0039] S104, Displacement verification.

[0040] In this embodiment, the actual displacement is cross-validated using the projection geometry of the oblique grating. The third displacement, determined by the superposition of the third and sixth grating regions, provides independent measurement information different from the first and second directions. This third displacement can be used to verify the projection consistency of orthogonal measurement results. Furthermore, when the grating signal quality deteriorates in a certain direction, the third displacement can be combined with the displacement in another direction with better measurement quality to reconstruct the displacement component in the damaged direction through projection relationship or interpolation, thus achieving redundant and complementary displacement information.

[0041] Figure 10 This is a schematic diagram illustrating the projection relationship between the first and second displacement components in a third direction, as provided in the embodiments of this application. Figure 10 As shown, a coordinate system is set up, with the X-axis as the first direction, the Y-axis as the second direction, and the 45° oblique direction as the third direction. According to projection geometry, the first displacement... The theoretical projected displacement in the third direction should be: Second displacement The theoretical projected displacement in the third direction should be: The theoretical verification displacement of the third party upward. .

[0042] In this embodiment of the application, the third displacement actually measured Displacement should be verified against theory. Ideally, they should be consistent. However, considering system noise and minor manufacturing errors, a certain range of deviation is permissible. For example, the host device can calculate the third displacement. Displacement should be verified against theory. The deviation value is calculated and compared with a preset threshold (e.g., based on the system's detection accuracy). If the deviation value does not exceed the preset threshold, a verification result indicating the reliability of the alignment measurement is generated, and the first displacement is... Second displacement As a reliable two-dimensional displacement value output; if the deviation value exceeds the preset threshold, a verification result indicating an abnormal alignment measurement is generated, indicating that the grating signal in at least one direction may be interfered with, and the measurement result cannot be directly accepted.

[0043] In some implementations, the host device can immediately trigger an exception handling mechanism when the verification result is abnormal. For example, the first displacement calculated in this operation can be discarded. Second displacement The optical detection device is then controlled to re-acquire the moiré fringe image for retesting; alternatively, the first displacement is corrected or eliminated based on historical data and statistical characteristics. and / or second displacement Simultaneously, a prompt signal indicating abnormal verification results is generated through the human-machine interface or communication interface, informing the operator of the presence of marking defects or image anomalies, and prompting them to check the marked area.

[0044] S105, Result Output and Alignment Control.

[0045] In this embodiment, the host device outputs the verification result and corresponding displacement data. The second base layer (such as the second wafer) is connected to the motor platform, and the host device can output the displacement value based on the reliable verification result. , The system generates motion control commands to drive the motor stage to move along the X and Y directions, thereby achieving automatic alignment of the second substrate relative to the first substrate (such as the first wafer). When the verification result is abnormal, the alignment operation can be paused and await further processing.

[0046] Based on steps S101-S105 above, this embodiment of the application introduces a 45° oblique grating region, adding an independent verification information channel to the original orthogonal alignment measurement. Thus, when signal distortion occurs in a grating region in a certain direction due to local contamination or manufacturing defects, this distortion will disrupt the first displacement. Second displacement With the third displacement The projected geometric consistency between the two values ​​ensures that the calculated deviation exceeds a preset threshold and is captured by the verification process. This prevents the system from using incorrect displacement values ​​for alignment, improving the robustness and alignment accuracy of the detection system.

[0047] It should be understood that, as mentioned above Figure 7 The steps in the flowcharts are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise explicitly stated herein, there is no strict order in which these steps are performed; they can be executed in other orders. Furthermore, as mentioned above... Figure 7 The flowchart may include at least some steps or stages. These steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least some of the steps or stages in other steps.

[0048] Example 3: Alignment Marking Structure Detection System for Multidirectional Moiré Fringe.

[0049] Figure 11 This is a schematic diagram of a detection system with a moiré fringe alignment mark structure provided in an embodiment of this application. Figure 11 As shown, the detection system 100 with a moiré fringe alignment mark structure includes: a light-emitting device 110, an optical detection device 120, a device under test 130, and a host device 140.

[0050] The light-emitting device 110 is used to provide a light source for detecting a structure with moiré stripe alignment marks.

[0051] The optical detection device 120 and the light-emitting device 110 are provided with an optical path for light propagation, which is used to acquire the moiré fringe image after passing through the device under test 130.

[0052] The device under test 130 is disposed on the optical path and includes a first substrate and a second substrate, which are arranged parallel to each other along the propagation direction of the optical path. A first alignment mark structure is disposed on the first substrate and a second alignment mark structure is disposed on the second substrate. The first alignment mark structure includes a first grating area arranged along a first direction, a second grating area arranged along a second direction, and a third grating area arranged along a third direction. The second alignment mark structure includes a fourth grating area arranged along the first direction, a fifth grating area arranged along the second direction, and a sixth grating area arranged along a third direction. The first grating area and the fourth grating area are aligned, the second grating area and the fifth grating area are aligned, and the third grating area and the sixth grating area are aligned. The third direction has projection components of the first direction and the second direction.

[0053] Host device 140 includes the following modules: Image acquisition module 141 is used to acquire a moiré fringe image formed by superimposing the first alignment mark structure and the second alignment mark structure in the propagation direction of the optical path based on the optical detection device 120. The displacement determination module 142 is used to obtain a first displacement determined by the superposition of the first grating region and the fourth grating region, and a second displacement determined by the superposition of the second grating region and the fifth grating region, based on the moiré fringe image. The displacement verification module 143 is used to obtain the third displacement determined by the superposition of the third grating area and the sixth grating area, and to verify the first displacement and the second displacement based on the third displacement to obtain the verification result. The control output module 144 is used to output the verification results and optionally control the motor platform carrying the second base layer.

[0054] It is understood that the functional division between the modules / devices illustrated in the embodiments of this application is merely illustrative and does not constitute a functional limitation on the detection system 100 with the moiré fringe alignment mark structure. In other embodiments of this application, the detection system 100 with the moiré fringe alignment mark structure may also employ different modules or combinations of multiple modules to implement the functions of the detection system 100 with the moiré fringe alignment mark structure.

[0055] In the embodiments of this application, based on the foregoing embodiments, the tag structure, modulation difference and verification method provided in this application can be implemented in a variety of alternative forms, making the solution of this application widely applicable.

[0056] In some implementations, the setting angle of the third direction is not limited to 45° and 135°, but also includes any direction other than parallel to the X-axis or Y-axis, such as 30°, 60°, 120°, or any other direction that does not parallel to the X-axis or Y-axis, as long as it has non-zero projection components in both the X and Y directions. When other angles are selected... At that time, theoretical verification displacement The calculation formula becomes: The advantage of choosing 45° is that its symmetry makes the projection coefficients equal, which simplifies the calculation and balances the sensitivity to displacement components in all directions.

[0057] In some implementations, when the single oblique grating is expanded into a grating group containing multiple angles (such as 45° and 135°), more diverse projection constraint equations can be formed, further enhancing the fault tolerance and correction capability of the alignment measurement results.

[0058] In the embodiments of this application, in the method of obtaining relative displacement based on optical modulation differences, the superposition of the first alignment mark structure and the second alignment mark structure to form moiré fringes does not necessarily mean that different grating periods must be used. In some embodiments, corresponding grating regions in the upper and lower layers can also use the same period, but a preset phase difference or local offset is introduced; in some embodiments, a small angle can be formed between the grating line directions of the first alignment mark structure and the second alignment mark structure based on a small rotation difference, and a rotational moiré fringe is formed after superposition, the displacement sensitivity of which is related to the angle; in some embodiments, a duty cycle difference can also be used, such as the ratio of the line width to the gap width of the first grating being different from the ratio of the line width to the gap width of the second grating, and a detectable intensity fringe is generated after superposition. Therefore, the optical modulation difference in the embodiments of this application can refer to any structural design that can cause the transmission / reflection functions of the upper and lower grating units to be not completely consistent and form superimposed moiré fringes.

[0059] In some implementations, the number of grating regions in each alignment mark structure may not be limited to three sets. For example, in addition to the X, Y and oblique gratings, a second oblique direction grating region may be added to provide a fourth observation channel for further redundancy verification or estimation of rotation components.

[0060] In some implementations, the image processing flow for extracting displacement can employ Fourier transform filtering, one-dimensional grayscale curve fitting, sine fitting, phase calculation, peak and valley detection, cross-correlation, or other equivalent image processing methods.

[0061] In some implementations, the displacement calculation based on displacement extraction algorithms is not limited to Fourier filtering and sine fitting; fringe centerline detection can also be used. For example, the bright band centerline of the moiré fringe can be extracted by threshold segmentation to track its positional changes; or a cross-correlation algorithm can be used to perform two-dimensional correlation matching between the real-time image and the reference image to find the maximum correlation displacement; or a machine learning regression model can be used to output displacement values ​​from the image region, etc.

[0062] In some embodiments, the materials used to fabricate the alignment mark structure, besides metal layers, can also be etched trenches, dielectric film steps, transmittance modulation patterns, etc., as long as sufficient contrast can be generated in the target wavelength band. The alignment method provided in this application is applicable to various scenarios such as infrared transmission wafer alignment, visible light reflection masking, wafer alignment, substrate stack alignment, and double-sided marking alignment of transparent substrates. In reflective applications, the light-emitting device and the optical detection device are located on the same side of the object under test, and illumination is achieved through a semi-transparent mirror or coaxial illumination. The first alignment mark and the second alignment mark are located on different object surfaces, and moiré fringe information is equivalently formed through reflection superposition or image registration.

[0063] In summary, the core of this application lies in providing a moiré alignment mark structure that integrates multi-directional (at least two orthogonal directions and one oblique direction) gratings, and by obtaining the displacement response of superimposed moiré fringes in each direction, utilizing the projection constraint relationship between the third-direction displacement and the orthogonal components, achieving redundancy complementarity, result verification, and anomaly identification of the measurement results.

[0064] Those skilled in the art will understand that implementing all or part of the processes in the foregoing embodiments can be accomplished by a computer program instructing related hardware. This program can be stored in a computer-readable storage medium, and when executed, it can include the processes described in the foregoing method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as readable storage devices or random access memory, magnetic disks, or optical disks.

[0065] In summary, the above description is merely an embodiment of the technical solution of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made based on the disclosure of this application should be included within the scope of protection of this application.

Claims

1. A alignment mark structure with moiré fringes, characterized in that, The alignment mark structure is applied in an optical inspection system, which includes a device under test. The device under test has a first base layer and a second base layer disposed on the light propagation path of the optical inspection system. The alignment mark structure includes a first alignment mark structure disposed on the first base layer and a second alignment mark structure disposed on the second base layer. The first alignment mark structure and the second alignment mark structure are arranged in pairs along the direction of the light propagation path. The first alignment mark structure includes a first grating area, a second grating area, and a third grating area. The grating lines in the first grating area are arranged along a first direction, the grating lines in the second grating area are arranged along a second direction, and the grating lines in the third grating area are arranged along a third direction. The third direction has projection components of the first direction and the second direction. The second alignment mark structure includes a fourth grating area corresponding to the first grating area, a fifth grating area corresponding to the second grating area, and a sixth grating area corresponding to the third grating area; When the second alignment mark structure is superimposed on the first alignment mark structure, the corresponding grating regions are superimposed to form moiré fringes.

2. The structure according to claim 1, characterized in that, The first grating region, the second grating region, and the third grating region are arranged with the center of the first alignment mark structure as a reference, in any one of the following ways: circular arrangement, quadrant arrangement, or radial arrangement. The arrangement of the fourth, fifth, and sixth grating regions corresponds one-to-one with the first, second, and third grating regions in the first alignment mark structure.

3. The structure according to claim 1, characterized in that, The first direction and the second direction are perpendicular to each other, and the third direction is located in the plane containing the first direction and the second direction, so that the third direction has projection components of the first direction and the second direction.

4. The structure according to claim 1, characterized in that, The optical modulation difference includes at least one of the following: period difference, phase difference, local offset, linewidth difference, duty cycle difference, or angle difference between the grating lines in the first grating region, the second grating region, and the third grating region and the grating lines in the corresponding fourth grating region, the fifth grating region, and the sixth grating region.

5. The structure according to claim 1, characterized in that, Based on the imaging field of view of the optical detection device, the positions of the first grating area, the second grating area, and the third grating area within the first alignment mark structure area, and the positions of the fourth grating area, the fifth grating area, and the sixth grating area within the second alignment mark structure area are determined, such that the corresponding grating areas superimpose to form moiré fringes that are captured by the same imaging field of view of the optical detection device.

6. The structure according to any one of claims 1-5, characterized in that, The first alignment mark structure also includes a seventh grating region, which is arranged along a fourth direction; the fourth direction has projection components of the first direction and the second direction; The second alignment mark structure also includes an eighth grating region, which is arranged along the fourth direction; When the first alignment mark and the second alignment mark are superimposed on each other, the seventh grating region overlaps with the eighth grating region to form moiré fringes along the fourth direction.

7. A method for detecting alignment marker structures with moiré fringes, characterized in that, A host device for an optical inspection system, the optical inspection system comprising: a light-emitting device, an optical inspection device, a device under test, and the host device; an optical path for light propagation is provided between the light-emitting device and the optical inspection device; the device under test comprises a first substrate and a second substrate, the first substrate and the second substrate being disposed on the optical path, and having an alignment mark structure as described in any one of claims 1-6, the alignment mark structure comprising: a first alignment mark structure, a second alignment mark structure, a first grating region, a second grating region, a third grating region, a fourth grating region, a fifth grating region, and a sixth grating region; the inspection method comprises: Based on the optical detection device, a moiré fringe image is obtained by superimposing the first alignment mark structure and the second alignment mark structure in the propagation direction of the optical path; The first displacement determined by the superposition of the first grating region and the fourth grating region, the second displacement determined by the superposition of the second grating region and the fifth grating region, and the third displacement determined by the superposition of the third grating region and the sixth grating region are obtained from the moiré fringe image; the third displacement along the third direction has projection components of the first displacement along the first direction and the second displacement along the second direction; The first displacement and the second displacement are verified based on the third displacement to obtain the verification result; Output the verification result.

8. The method according to claim 7, characterized in that, The step of verifying the first displacement and the second displacement based on the third displacement to obtain the verification result includes: Calculate the projection components of the first displacement and the second displacement along the third direction to obtain the theoretical verification displacement; Calculate the deviation between the third displacement and the theoretical verification displacement; If the deviation does not exceed the preset threshold, a verification result indicating the reliability of the alignment measurement is generated; If the deviation exceeds the preset threshold, a verification result indicating an abnormal alignment measurement is generated. The verification result indicating an abnormal alignment measurement is used to indicate the correction or elimination of the first displacement and the second displacement.

9. The method according to claim 7, characterized in that, The first displacement, the second displacement, and the third displacement are calculated by the moiré fringe after an image processing procedure, which includes at least extracting fringe features from the moiré fringe image.

10. A system for detecting alignment marker structures with moiré fringes, characterized in that, include: Light-emitting device; An optical detection device, wherein an optical path for light propagation is provided between the light-emitting device and the optical detection device; The device under test includes a first substrate and a second substrate, the first substrate and the second substrate being disposed on the optical path, and having an alignment mark structure as described in any one of claims 1-6, the alignment mark structure including: a first alignment mark structure, a second alignment mark structure, a first grating region, a second grating region, a third grating region, a fourth grating region, a fifth grating region and a sixth grating region; The host device includes the following modules: An image acquisition module is used to acquire a moiré fringe image formed by superimposing the first alignment mark structure and the second alignment mark structure in the propagation direction of the optical path, based on an optical detection device. The displacement determination module is used to obtain, based on the moiré fringe image, a first displacement determined by the superposition of the first grating area and the fourth grating area, a second displacement determined by the superposition of the second grating area and the fifth grating area, and a third displacement determined by the superposition of the third grating area and the sixth grating area; the third displacement along a third direction has projection components of the first displacement along a first direction and the second displacement along a second direction; The displacement verification module is used to verify the first displacement and the second displacement based on the third displacement, and obtain the verification result; The control output module is used to output the verification result.

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