Overlay measurement method, apparatus, and device, and storage medium

Abstract

An overlay measurement method, apparatus, and device, and a storage medium, relating to the technical field of lithography. The method is applied to a controller of an imaging overlay measurement device, and comprises: in response to a test instruction, acquiring a preset number of test positions corresponding to one diaphragm among at least one diaphragm (S110); controlling the diaphragm to sequentially move to each test position to perform overlay measurement on a wafer under test to respectively acquire a device error of the imaging overlay measurement device at each test position (S120); according to the impact of a change in the test position on the device error, determining, for the wafer under test, a corresponding target diaphragm position at which the device error is minimal (S130); and adjusting the diaphragm to the target diaphragm position, and controlling the imaging overlay measurement device to perform overlay measurement on an overlay mark in the wafer under test (S140). According to the method, apparatus, and device, overlay measurement is performed on the wafer under test when an error introduced by the diaphragm is minimal, thereby improving the accuracy of overlay measurement.

Description

A method, apparatus, device and storage medium for overlay measurement.

[0001] This application claims priority to Chinese Patent Application No. 2024119312297, filed on December 26, 2024, entitled "A method, apparatus, device and storage medium for overlay measurement", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of photolithography technology, and more specifically, to an overlay measurement method, apparatus, device, and storage medium. Background Technology

[0003] In photolithography, overlay error is a crucial parameter for measuring overlay accuracy, and it can be measured using imaging overlay measurement equipment. The measurement method of this equipment involves illuminating the overlay marks or markings on the wafer using apertures of different apertures, measuring these markings, and determining the overlay error based on the alignment error between the overlay marks of the current photolithographic layer and the previous photolithographic layer. The position and angle of the aperture control the direction of light propagation and the incident range, ensuring uniform and sufficient illumination in the measurement area. This facilitates the imaging system capturing a clear image of the overlay marks, improving measurement accuracy.

[0004] To ensure the accuracy of imaging overlay measurements, the position of each aperture needs to be pre-calibrated to ensure that the center of the aperture is located at the center of the illumination optical path, thus achieving optimal measurement conditions. For example, during the equipment integration and assembly stage, the position of each aperture is calibrated offline using optical methods. However, due to factors such as optomechanical drift and differences in the wafer measurement process, the pre-calibrated aperture position may not guarantee that the center of the aperture is always located at the center of the illumination optical path. Furthermore, the optimal aperture position may differ for different measurement objects. Therefore, the aperture position calibrated during integration and assembly may not be applicable to all measurement objects, leading to a decrease in the accuracy of overlay measurements.

[0005] Therefore, there is an urgent need for a method to determine the optimal measurement position of the positioning aperture, so that the imaging overlay measurement equipment can reach the optimal measurement state in each measurement and improve the accuracy of overlay measurement. Summary of the Invention

[0006] The following is a summary of the detailed description of this application. This summary is not intended to limit the scope of the claims. This application provides an overlay measurement method, apparatus, device, and storage medium, and adopts the following technical solutions:

[0007] The first aspect of this application provides a scaling measurement method applied to a controller of an imaging scaling measurement device, the imaging scaling measurement device including at least one aperture, and the scaling measurement method comprising:

[0008] In response to a test command, obtain a preset number of test positions corresponding to one of the at least one apertures;

[0009] The control aperture is moved sequentially to each test position to perform overlay measurement on the wafer under test. The equipment error of the imaging overlay measurement device at each test position is obtained. The equipment error characterizes the error introduced by the change of aperture position.

[0010] Based on the impact of changes in the test position on equipment error, determine the target aperture position corresponding to the wafer under test;

[0011] Adjust the aperture to the target aperture position and control the imaging overlay measurement device to perform overlay measurement on the overlay marks in the wafer to be measured.

[0012] In one possible implementation, the target aperture position corresponding to the wafer under test is determined based on the impact of changes in the test position on equipment error, including:

[0013] For each test position and the corresponding device error, a fitting is performed to obtain the objective function for the wafer under test. The objective function characterizes the functional relationship between the test position and the device error for the wafer under test.

[0014] The test position corresponding to the minimum value of the objective function is set, and this is determined as the target aperture position for the wafer under test.

[0015] In one possible implementation, the control aperture is sequentially moved to each test position to perform overlay measurements on the wafer under test, and the equipment error of the imaging overlay measurement device at each test position is obtained, including:

[0016] The control aperture is moved sequentially to each test position to perform overlay measurement on the wafer under test, and the overlay error corresponding to each test position is obtained. The overlay error includes the overlay mark offset data corresponding to the wafer under test when the rotation angle is 0° and 180°, respectively.

[0017] Based on the overlay error corresponding to each test position, determine the corresponding equipment error for each test position.

[0018] In one possible implementation, the device error corresponding to each test position is determined based on the overlay error corresponding to each test position, including:

[0019] From the overlay error corresponding to the test position, obtain the first offset corresponding to each overlay mark to be measured in the wafer under test when the rotation angle is 0°, and the second offset corresponding to each overlay mark to be measured in the wafer under test when the rotation angle is 180°.

[0020] Based on the difference between the first offset and the second offset corresponding to the overlay mark to be measured, the initial equipment error corresponding to the overlay mark to be measured being placed at the test position is determined;

[0021] The average value of the initial equipment error corresponding to each measurement mark placed at the test position is determined as the equipment error corresponding to the test position.

[0022] In one possible implementation, obtaining the test position of a preset number of apertures corresponding to at least one aperture includes:

[0023] Obtain the pre-calibrated initial position of one of the at least one apertures;

[0024] The initial position is adjusted according to the preset step distance to obtain a preset number of test positions.

[0025] A second aspect of this application provides a scaling measurement device, which is used as a controller for an imaging scaling measurement device. The imaging scaling measurement device includes at least one aperture. The scaling measurement device includes:

[0026] The test position acquisition unit is used to acquire a preset number of test positions corresponding to one of the at least one apertures in response to a test command.

[0027] The error acquisition unit is used to control the aperture to move sequentially to each test position to perform overlay measurement on the wafer under test, and to acquire the equipment error of the imaging overlay measurement equipment at each test position. The equipment error characterizes the error introduced by the change of aperture position.

[0028] The target position determination unit is used to determine the target aperture position corresponding to the wafer under test based on the influence of the change in the test position on the equipment error.

[0029] The control measurement unit is used to adjust the aperture to the target aperture position and control the imaging overlay measurement device to perform overlay measurement on the overlay marks in the wafer to be measured.

[0030] In one possible implementation, the target location determination unit includes:

[0031] The data fitting subunit is used to fit each test position and the corresponding device error to obtain the objective function for the wafer under test. The objective function characterizes the functional relationship between the test position and the device error for the wafer under test.

[0032] The target position determination sub-unit is used to determine the test position corresponding to the minimum value of the objective function as the target aperture position of the wafer under test.

[0033] In one possible implementation, the error acquisition unit includes:

[0034] The overlay error acquisition subunit is used to control the aperture to move sequentially to each test position to perform overlay measurement on the wafer under test, and to acquire the overlay error corresponding to each test position. The overlay error includes: the overlay mark offset data corresponding to the wafer under test when the rotation angle is 0° and 180° respectively.

[0035] The equipment error determination subunit is used to determine the equipment error corresponding to each test position based on the overlay error corresponding to each test position.

[0036] A third aspect of this application provides an overlay measuring device, comprising at least one processor and a memory connected to the processor, wherein:

[0037] Memory is used to store computer programs;

[0038] The processor is used to execute computer programs to enable the overlay measuring device to implement the overlay measuring method of the first aspect or any implementation thereof.

[0039] A fourth aspect of this application provides a computer storage medium carrying one or more computer programs. When these programs are executed by an overlay measuring device, the device is enabled to implement the overlay measuring method described in the first aspect or any implementation thereof.

[0040] As can be seen from the above technical solutions, the overlay measurement method provided in this application, in response to the test command of the wafer under test, moves the aperture to multiple test positions and measures the error introduced by the device at each test position. Since only the position of the aperture changes in the imaging overlay measurement device, the error introduced by the device is assumed to be the error introduced by the change of the aperture position. Based on the influence of the change of the aperture position on the device error, the aperture position with the smallest device error is determined as the target position corresponding to the wafer under test.

[0041] By positioning the aperture of the imaging overlay measurement equipment to the target position, overlay measurements are performed on the wafer under test with minimal error introduced by the aperture, thus improving the accuracy of the overlay measurement. Furthermore, based on the measurement results of the wafer under test, this application adjusts the aperture position to make the target aperture position more suitable for the wafer under test. Therefore, if the wafer measured by the imaging overlay measurement equipment is replaced, this application can individually position the optimal aperture for the wafer, improving the flexibility of the imaging overlay measurement equipment. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 is a schematic diagram of the aperture provided in an embodiment of this application;

[0044] Figure 2 is a flowchart illustrating an overlay measurement method provided in an embodiment of this application.

[0045] Figure 3 is a schematic diagram of the process of controlling the position of the aperture for overlay measurement according to an embodiment of this application;

[0046] Figure 4 is a schematic diagram of the structure of a cross-cutting measuring device provided in an embodiment of this application;

[0047] Figure 5 is a schematic diagram of the structure of an overlay measuring device provided in an embodiment of this application. Detailed Implementation

[0048] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0049] To adapt to different lighting environments or imaging requirements, imaging overlay measurement equipment is typically equipped with illumination aperture stops of different specifications. Referring to Figure 1, a schematic diagram of the aperture stops provided in this embodiment typically shows three specifications: large, medium, and small. During the overlay measurement process, different aperture stops are switched according to requirements, and the aperture stops are moved to the corresponding calibration positions. However, during the switching and moving of aperture stops, optomechanical drift caused by mechanical structure displacement, temperature changes, and air disturbances may prevent the imaging overlay measurement equipment from always guaranteeing optimal measurement performance at the calibration position. Furthermore, since the optimal illumination aperture stop position differs for different wafers under test, and the calibration position is not necessarily the optimal position for the current wafer under test, the imaging overlay measurement equipment cannot achieve the optimal measurement state for the wafer under test at the calibration position, resulting in lower accuracy of the measurement results.

[0050] To address the aforementioned technical problems, this application provides an overlay measurement method applied to the controller of an imaging overlay measurement device. The controller can control each aperture in the moving imaging overlay measurement device, wherein the imaging overlay measurement device is configured with at least one aperture to meet different measurement requirements.

[0051] Referring to Figure 2, a flowchart illustrating an overlay measurement method provided in this embodiment of the application is used to describe the overlay measurement method applied to a controller. Specifically, the process includes the following steps:

[0052] Step S110: In response to the test command, obtain the preset number of test positions corresponding to one of the at least one apertures.

[0053] It is understandable that although the imaging overlay measurement device is configured with multiple apertures, only one aperture is needed in actual measurement. Therefore, in response to the measurement command, a target aperture that is suitable for the current lighting environment and meets the measurement requirements is determined from the multiple apertures. In the embodiments of this application, steps S110-S140 are all adjustments to the target aperture.

[0054] This application embodiment finds the optimal measurement position for the aperture and determines multiple test positions for aperture calibration. By adjusting the aperture among multiple test positions, the measurement effect of the imaging overlay measurement device under different test positions is observed, so as to determine the position with the best test effect or measurement state from many test positions.

[0055] Optionally, obtaining a preset number of test positions corresponding to the aperture includes: obtaining a pre-calibrated initial position corresponding to the aperture; adjusting the initial position according to a preset step distance to obtain a preset number of test positions.

[0056] Referring to Figure 1, it includes three aperture stops of different sizes. The X and Y planes are the planes in which the aperture stops are located, and the Z direction is the light transmission direction, i.e., the optical axis direction. During the optical integration and adjustment stage of the imaging overlay equipment, the initial position of each aperture stop is calibrated. For example, the initial position of the large aperture stop is set to (X0...). Large Y0 Large The initial position of the middle aperture stop is set to (X0). Middle Y0 Middle The initial position of the small aperture stop is set to (X0). Small Y0 Small ).

[0057] In this embodiment, a small-aperture aperture is used as the target aperture. Based on the initial position of the small-aperture aperture, multiple test positions are determined according to a preset step distance. The number of test positions can be set according to the required accuracy of aperture position adjustment. If a highly accurate optimal aperture position needs to be located, as many test positions as possible can be determined. Conversely, if the accuracy requirement for the optimal aperture position is not high, the number of test positions can be reduced accordingly. Similarly, the step distance can be set. If the preset number is large, the step distance can be appropriately reduced to avoid the test positions after multiple adjustments exceeding the adjustable range of the aperture.

[0058] Based on this, refer to the following formula (1) to determine the coordinates of each test position based on the initial position.

[0059] Among them, (X) Start ,Y Start ), (X end ,Y end ) represent the starting and ending coordinates of the test position, respectively; nx and ny represent the number of unidirectional test positions of the small aperture stop in the X and Y directions, respectively, which is 1 / 2 of the total number of test positions; Stepx and Stepy are the step distances of the small aperture stop in the X and Y directions, respectively. It can be understood that the coordinates of the test position between the starting and ending coordinates can be obtained by changing the value of n in formula (1), but the replaced value must be a positive integer not exceeding n.

[0060] Based on this, multiple test positions of the aperture to be adjusted can be obtained.

[0061] Step S120: Control the aperture to move sequentially to each test position to perform overlay measurement on the wafer under test, and obtain the equipment error of the imaging overlay measurement device at each test position.

[0062] Based on the multiple test positions of the aperture obtained in step S110, the aperture is adjusted to move to each test position, and the imaging overlay measurement device is controlled to perform overlay measurement on the wafer under test at each test position. Specifically, the test positions of the aperture can be adjusted sequentially according to the positional relationship between the test position and the initial position, or the coordinate order from the starting coordinate to the ending coordinate determined in step S110, so as to ensure that no test positions are missed.

[0063] In this embodiment, the measurement status of the device is evaluated by the error introduced by the imaging overlay measurement device at each test position. Since only the aperture position changes in the imaging overlay measurement device, the error introduced by the device can be understood as the error caused by the change in the aperture position.

[0064] Understandably, if you want to test the error introduced by the imaging overlay test equipment, you need to compare the overlay measurement results of the wafer under test at 0° and 180°. Theoretically, the overlay measurement results of the wafer under test at 0° and 180° should be consistent, or the deviation between the overlay measurement results of the wafer under test at 0° and 180° should not exceed a certain threshold. Deviations exceeding the threshold can be understood as errors introduced by the equipment.

[0065] Based on this, the embodiments of this application not only control the measurement of the overlay measurement results corresponding to each test position, but also control the measurement of the overlay measurement results corresponding to 0° and 180° of the wafer under test at each test position.

[0066] In one possible implementation, the control aperture is moved sequentially to each test position to perform overlay measurement on the wafer under test, and the overlay error corresponding to each test position is obtained. The overlay error includes: the overlay mark offset data corresponding to the wafer under test when the rotation angle is 0° and 180° respectively; based on the overlay error corresponding to each test position, the corresponding equipment error for each test position is determined.

[0067] Specifically, referring to Figure 3, a flowchart illustrating the process of controlling the aperture position for overlay measurement according to an embodiment of this application, the process of controlling aperture movement for overlay measurement is explained. First, the aperture is moved to the initial position. Using the initial position as the starting point, overlay measurements are performed on the wafers under test at 0° and 180° respectively, obtaining overlay data or overlay values, i.e., the overlay measurement results. After completing the measurement at the initial position, it is determined whether all test positions have been measured. If the determination result is no, the aperture is moved to the next test position, and overlay measurements are performed on the wafers under test at 0° and 180° respectively. Based on this, until all test positions have been measured, the aperture movement is stopped. Based on all the obtained overlay measurement results, the equipment error corresponding to each test position is determined.

[0068] Further, based on the overlay error corresponding to each test position, the corresponding equipment error for each test position is determined, including: obtaining from the overlay error corresponding to the test position the first offset corresponding to each overlay mark to be measured in the wafer under test when the rotation angle is 0°, and the second offset corresponding to each overlay mark to be measured in the wafer under test when the rotation angle is 180°; determining the initial equipment error corresponding to the overlay mark to be measured at the test position based on the difference between the first offset and the second offset; and determining the average value of the initial equipment error corresponding to each overlay mark to be measured at the test position as the equipment error corresponding to the test position.

[0069] It is understandable that the overlay value obtained by the imaging overlay measurement equipment from the wafer under test is the overlay accuracy (OVL), which is the overlay offset between two different layers on the wafer. Based on this, from the overlay measurement results corresponding to each test position, the first offset of 0° and the second offset of 180° measured at that test position are obtained for the wafer under test. It is also understandable that the wafer under test typically contains multiple overlay marks. During overlay measurement, each overlay mark is measured, and the resulting overlay measurement result contains the overlay value corresponding to each mark. Therefore, from the overlay measurement results corresponding to a test position, the first offset of 0° and the second offset of 180° for each overlay mark at that test position can be obtained.

[0070] Furthermore, based on the first offset of 0° and the second offset of 180° for each overlay mark of the wafer under test placed at each test position, the initial equipment error corresponding to the overlay mark to be measured at the test position is determined, specifically, as shown in the following formula (2).

[0071] Among them, (x i ,y i ) represents the coordinates of the test position, and k represents the k-th overlay mark among all overlay marks on the wafer under test; Indicates in (x i ,y i The test position is set, and the initial equipment error corresponds to the kth overlay mark; Indicates in (x i ,y i The test position is set at the first offset of 0° from the k-th overlay mark; Indicates in (x i ,y iThe test position is set to a second offset of 180° from the k-th set of markings. It is understood that the offset in this embodiment is a vector, meaning the signs of the true OVL values ​​at 0° and 180° are opposite. The device error TIS remains unchanged; adding the two achieves the effect of subtracting the offsets. Therefore, the first offset OVL_0 of a set of markings at 0° = true OVL value + TIS, and the second offset OVL_180 of the same set of markings at 180° = -true OVL value + TIS. Based on this, and The sum of these two values ​​is twice the equipment error TIS.

[0072] Furthermore, referring to the following formula (3), the average value of the initial equipment error corresponding to all overlay marks at the test position is used as the equipment error introduced by the change of aperture position when the test position is lowered.

[0073] Where n is the total number of overlay marks on the wafer to be tested, TIS_M xi,yi It means (x) i ,y i The test position corresponds to the equipment error.

[0074] Step S130: Determine the target aperture position corresponding to the wafer under test based on the influence of the change in the test position on the equipment error.

[0075] Step S140: Adjust the aperture to the target aperture position and control the imaging overlay measurement device to perform overlay measurement on the overlay marks in the wafer to be measured.

[0076] It is understood that this application embodiment quantifies the measurement state of the imaging overlay measurement equipment using equipment error. The larger the equipment error, the worse the equipment measurement state at the current test position. Based on this, the equipment errors corresponding to all test positions are statistically analyzed, and the impact of changes in test position on equipment error is summarized. For example, the equipment error corresponding to a test position further away from the initial position is smaller, which indicates that the further the aperture is from the initial position, the better the corresponding equipment measurement state. Based on this, within the allowable movement range of the aperture, the test position with the smallest equipment error is determined as the target aperture position for measuring the wafer under test.

[0077] In one possible implementation, the target aperture position corresponding to the wafer under test is determined based on the influence of the change in the test position on the equipment error. This includes: fitting each test position and the corresponding equipment error to obtain an objective function for the wafer under test, whereby the objective function characterizes the functional relationship between the test position and the equipment error for the wafer under test; and determining the test position corresponding to the minimum value of the objective function as the target aperture position for the wafer under test.

[0078] Set (x) for all the above test locations. i ,y i ), and the corresponding device error TIS_M at each test location. xi,yi Data fitting is performed to obtain a functional expression that characterizes the influence relationship between the test position and the equipment error, i.e., the objective function, as shown in equation (4). TIS_M xi,yi =f(x) i ,y i ).....................................(4)

[0079] Optionally, the objective function can be fitted into a two-variable quadratic function as shown in (5) to facilitate the determination of the minimum value of the equipment error from the objective function, thereby determining the test position of the aperture corresponding to the imaging overlay measurement equipment in the best measurement state, which is then used as the target aperture position.

[0080] Wherein, K0, K1, K2, K3, K4, and K5 represent the coefficients, and the specific values ​​of the coefficients can be determined based on the data fitting results.

[0081] Furthermore, based on the objective function of equation (5), TIS_M is solved. xi,yi The test position corresponding to the minimum value is set to (x) i ,y i The test position is set as the target aperture position. When the aperture is at this position, the measurement state of the imaging overlay measurement equipment is optimal. The aperture is moved to the target aperture position, at which point the imaging overlay measurement equipment officially begins overlay measurement on the wafer under test.

[0082] In summary, the overlay measurement method provided in this application, in response to a test command for the wafer under test, moves the aperture to multiple test positions and measures the error introduced by the device at each test position. Since only the aperture position changes in the imaging overlay measurement device, the error introduced by the device is assumed to be the error introduced by the change in aperture position. Based on the influence of the aperture position change on the device error, the aperture position with the smallest device error is determined as the target position corresponding to the wafer under test.

[0083] By positioning the aperture of the imaging overlay measurement equipment to the target position, overlay measurements are performed on the wafer under test with minimal error introduced by the aperture, thus improving the accuracy of the overlay measurement. Furthermore, based on the measurement results of the wafer under test, this application adjusts the aperture position to make the target aperture position more suitable for the wafer under test. Therefore, if the wafer measured by the imaging overlay measurement equipment is replaced, this application can individually position the optimal aperture for the wafer, improving the flexibility of the imaging overlay measurement equipment.

[0084] The overlay measuring device provided in the embodiments of this application is described below. The overlay measuring device described below can be referred to in correspondence with the overlay measuring method described above.

[0085] First, referring to Figure 4, the overlay measurement device applied to the controller of the imaging overlay measurement equipment will be introduced. As shown in Figure 4, the overlay measurement device may include:

[0086] The test position acquisition unit 100 is used to acquire a preset number of test positions corresponding to one of the at least one apertures in response to a test command.

[0087] The error acquisition unit 200 is used to control the aperture to move sequentially to each of the test positions to perform overlay measurement on the wafer under test, and to acquire the equipment error of the imaging overlay measurement device at each of the test positions. The equipment error represents the error introduced by the change of the aperture position.

[0088] The target position determination unit 300 is used to determine the target aperture position corresponding to the wafer under test based on the influence of the change of the test position on the equipment error.

[0089] The control measurement unit 400 is used to adjust the aperture to the target aperture position and control the imaging overlay measurement device to perform overlay measurement on the overlay marks in the wafer to be measured.

[0090] In one possible implementation, the target location determination unit 300 includes:

[0091] The data fitting subunit is used to fit each of the test positions and the corresponding device errors to obtain the objective function corresponding to the wafer under test. The objective function characterizes the functional relationship between the test positions and the device errors corresponding to the wafer under test.

[0092] The target position determination subunit is used to determine the test position corresponding to the minimum value of the objective function as the target aperture position of the wafer under test.

[0093] In one possible implementation, the error acquisition unit 200 includes:

[0094] The overlay error acquisition subunit is used to control the aperture to move sequentially to each of the test positions to perform overlay measurement on the wafer under test, and to acquire the overlay error corresponding to each of the test positions. The overlay error includes: the overlay mark offset data corresponding to the wafer under test when the rotation angle is 0° and 180°, respectively.

[0095] The equipment error determination subunit is used to determine the equipment error corresponding to each test position based on the overlay error corresponding to each test position.

[0096] In one possible implementation, the device error determination subunit includes:

[0097] The offset acquisition subunit is used to acquire, from the overlay error corresponding to the test position, the first offset corresponding to each overlay mark to be measured in the wafer under test when the rotation angle is 0°, and the second offset corresponding to each overlay mark to be measured in the wafer under test when the rotation angle is 180°.

[0098] The initial equipment error determination subunit is used to determine the initial equipment error corresponding to the placement of the overlay mark to be measured at the test position based on the difference between the first offset and the second offset corresponding to the overlay mark to be measured.

[0099] The equipment error determination subunit is used to determine the average value of the initial equipment error corresponding to each of the measured overlay marks placed at the test position as the equipment error corresponding to the test position.

[0100] In one possible implementation, the test location acquisition unit 100 includes:

[0101] The initial position acquisition subunit is used to acquire the pre-calibrated initial position corresponding to the aperture.

[0102] The position adjustment subunit is used to adjust the initial position according to a preset step distance to obtain a preset number of test positions.

[0103] In summary, the overlay measurement method provided in this application, in response to a test command for the wafer under test, moves the aperture to multiple test positions and measures the error introduced by the device at each test position. Since only the aperture position changes in the imaging overlay measurement device, the error introduced by the device is assumed to be the error introduced by the change in aperture position. Based on the influence of the aperture position change on the device error, the aperture position with the smallest device error is determined as the target position corresponding to the wafer under test.

[0104] The aperture of the imaging overlay measurement device is positioned at the target location. Overlay measurements are performed on the wafer under test with minimal error introduced by the aperture, improving the accuracy of the overlay measurement. Furthermore, based on the measurement results of the wafer under test, the aperture position is adjusted to make the target aperture position more suitable for the wafer under test. Therefore, if the wafer measured by the imaging overlay measurement device is replaced, this application can individually position the optimal aperture for the wafer, improving the flexibility of the imaging overlay measurement device. The overlay measurement device provided in this application can be applied to overlay measurement equipment.

[0105] Figure 5 shows a schematic diagram of the structure of the overlay measurement device. Referring to Figure 5, the structure of the overlay measurement device may include: at least one processor 10, at least one memory 20, at least one communication bus 30 and at least one communication interface 40.

[0106] In this embodiment, the number of processor 10, memory 20, communication bus 30 and communication interface 40 is at least one, and processor 10, memory 20 and communication interface 40 communicate with each other through communication bus 30.

[0107] The processor 10 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application.

[0108] The memory 20 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0109] The memory stores a program, and the processor can call the program stored in the memory. The program is used to implement the various processing steps in the aforementioned overlay measurement method.

[0110] This application also provides a computer storage medium that can store a program suitable for execution by a processor, the program being used to implement the various processing flows in the aforementioned overlay measurement method.

[0111] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For device-type embodiments, since they are basically similar to the method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0112] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0113] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0114] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for overlay measurement, wherein, A controller for an imaging overlay measurement device, the imaging overlay measurement device including at least one aperture, the overlay measurement method comprising: In response to a test command, a preset number of test positions corresponding to one of the at least one apertures are obtained; The aperture is controlled to move sequentially to each of the test positions to perform overlay measurement on the wafer under test, and the equipment error of the imaging overlay measurement device at each of the test positions is obtained respectively. The equipment error represents the error introduced by the change of the aperture position. Based on the impact of the change in the test position on the equipment error, the target aperture position corresponding to the wafer under test is determined; Adjust the aperture to the target aperture position and control the imaging overlay measurement device to perform overlay measurement on the overlay marks in the wafer to be tested.

2. The overlay measurement method according to claim 1, wherein, The step of determining the target aperture position corresponding to the wafer under test based on the influence of the change in the test position on the equipment error includes: For each test location and the corresponding device error, a target function is obtained for the wafer under test. The target function characterizes the functional relationship between the test location and the device error for the wafer under test. The test position corresponding to the minimum value of the objective function is set and determined as the target aperture position corresponding to the wafer under test.

3. The overlay measurement method according to claim 1, wherein, The control method involves sequentially moving the aperture to each of the test positions to perform overlay measurements on the wafer under test, and acquiring the equipment error of the imaging overlay measurement device at each of the test positions, including: The aperture is controlled to move sequentially to each of the test positions to perform overlay measurement on the wafer under test, and the overlay error corresponding to each of the test positions is obtained. The overlay error includes: the overlay mark offset data corresponding to the wafer under test when the rotation angle is 0° and 180°, respectively. Based on the overlay error corresponding to each test position, the equipment error corresponding to each test position is determined.

4. The overlay measurement method according to claim 3, wherein, The determination of the equipment error corresponding to each test position based on the overlay error corresponding to each test position includes: From the overlay error corresponding to the test position, obtain the first offset corresponding to each overlay mark to be measured in the wafer under test when the rotation angle is 0°, and the second offset corresponding to each overlay mark to be measured in the wafer under test when the rotation angle is 180°. Based on the difference between the first offset and the second offset corresponding to the overlay mark to be measured, the initial equipment error corresponding to the overlay mark to be measured being placed at the test position is determined; The average value of the initial device error corresponding to each of the measured overlay marks placed at the test position is determined as the device error corresponding to the test position.

5. The overlay measurement method according to claim 1, wherein, The step of obtaining a preset number of test positions corresponding to one of the at least one apertures includes: Obtain the pre-calibrated initial position of one of the at least one apertures; The initial position is adjusted according to the preset step distance to obtain a preset number of test positions.

6. A measuring device for overlay, wherein, It should be configured as a controller for an imaging overlay measurement device, the imaging overlay measurement device including at least one aperture, the overlay measurement device including: The test position acquisition unit is configured to acquire a preset number of test positions corresponding to one of the at least one apertures in response to a test command. The error acquisition unit is configured to control the aperture to move sequentially to each of the test positions to perform overlay measurement on the wafer under test, and to acquire the equipment error of the imaging overlay measurement device at each of the test positions. The equipment error represents the error introduced by the change of the aperture position. The target position determination unit is configured to determine the target aperture position corresponding to the wafer under test based on the influence of the change of the test position on the device error; The control measurement unit is configured to adjust the aperture to the target aperture position and control the imaging overlay measurement device to perform overlay measurement on the overlay marks in the wafer under test.

7. The overlay measuring device according to claim 6, wherein, The target location determination unit includes: The data fitting subunit is configured to fit each of the test locations and the corresponding device errors to obtain an objective function for the wafer under test, wherein the objective function characterizes the functional relationship between the test locations and the device errors for the wafer under test. The target position determination subunit is configured to be the test position corresponding to the minimum value of the objective function, and is determined to be the target aperture position corresponding to the wafer under test.

8. The overlay measuring device according to claim 6, wherein, The error acquisition unit includes: The overlay error acquisition subunit is configured to control the aperture to move sequentially to each of the test positions to perform overlay measurement on the wafer under test, and acquire the overlay error corresponding to each of the test positions. The overlay error includes: the overlay mark offset data corresponding to the wafer under test when the rotation angle is 0° and 180°, respectively. The equipment error determination subunit is configured to determine the equipment error corresponding to each test position based on the overlay error corresponding to each test position.

9. A measuring device for overlay, wherein, It includes at least one processor and a memory connected to the processor, wherein: The memory is used to store computer programs; The processor is used to execute the computer program so that the overlay measuring device can implement the overlay measuring method as described in any one of claims 1 to 5.

10. A computer storage medium, wherein, The storage medium carries one or more computer programs that, when executed by the overlay measuring device, enable the overlay measuring device to implement the overlay measuring method as described in any one of claims 1 to 5.

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