Automatic focusing method, system and apparatus, and computer program product

Abstract

The present disclosure relates to the technical field of precision manufacturing. Provided are an automatic focusing method, system and apparatus, and a computer program product. The automatic focusing method involved in the present disclosure comprises: controlling a first motion module and a second motion module of an objective table to move in a first direction and a second direction, respectively, such that the objective table reaches a first target position in the first direction and a second target position in the second direction; controlling a third motion module of the objective table to move in a third direction, such that starting from a scanning start position in the third direction, the objective table moves one or more times in the third direction, wherein the amount of displacement of each movement is a preset step pitch; and controlling the third motion module to move in the third direction, such that the objective table reaches a focusing position, wherein the focusing position is determined from among the positions corresponding to the one or more times of movement in the third direction.

Description

An auto-focusing method, system, apparatus and computer program product TECHNICAL FIELD

[0001] The present application relates to the field of precision manufacturing technology, and in particular, to an auto-focusing method, system, apparatus and computer program product. BACKGROUND

[0002] In the field of precision manufacturing technology, imaging technology is often used to determine error information of an object to be processed (in some embodiments, also referred to as an object to be photographed). Specifically, in order to accurately measure error data, the object to be processed needs to be accurately focused to obtain a high-definition image, and then image processing technology is used to obtain error data of the object to be processed. As can be seen, whether the object to be processed can be accurately focused will affect the processing quality and efficiency.

[0003] Therefore, some embodiments of the present application provide an auto-focusing method, system, apparatus and computer program product to improve focusing accuracy and efficiency.

[0004] SUMMARY

[0005] One or more embodiments of the present application provide an auto-focusing method, comprising: controlling a first motion module and a second motion module of a carrier table to move in a first direction and a second direction respectively, so that the carrier table reaches a first target position in the first direction and a second target position in the second direction; controlling a third motion module of the carrier table to move in a third direction, so that the carrier table moves one or more times in the third direction from a scanning starting position in the third direction, and a displacement of each movement is a preset step distance; controlling the third motion module to move in the third direction, so that the carrier table reaches a focusing position; the focusing position is determined from positions corresponding to one or more movements in the third direction; wherein the carrier table is used to carry an object to be photographed; the third direction is consistent with a focusing direction of a photographing device located above the carrier table, the first direction and the second direction are located in the same plane, and the plane is perpendicular to the third direction.

[0006] According to the method of some embodiments of the present application, the first direction is perpendicular to the second direction; and the preset step distance is not more than 20 nm or not more than 10 nm.

[0007] According to the method of some embodiments of the present application, the second motion module is stacked on the first motion module, the third motion module is stacked on the second motion module, and the carrier table is arranged on the third motion module.

[0008] According to the method of some embodiments of the present application, the first movement module of the object table is controlled to move in the first direction so that the object table reaches the first target position in the first direction, comprising: obtaining the first target position in the first direction; generating a first driving signal based on the first target position through the first PIV control loop; outputting the first driving signal to the first movement module to control the movement of the first movement module until the difference between the measured position of the object table in the first direction and the first target position is less than the first preset error window.

[0009] The second movement module of the object table is controlled to move in the second direction so that the object table reaches the second target position in the second direction, comprising: obtaining the second target position in the second direction; generating a second driving signal based on the second target position through the second PIV control loop; outputting the second driving signal to the second movement module to control the movement of the second movement module until the difference between the measured position of the object table in the second direction and the second target position is less than the second preset error window.

[0010] According to the method of some embodiments of the present application, when the first movement module and the second movement module of the object table are controlled to move in the first direction and the second direction respectively so that the object table reaches the first target position in the first direction and the second target position in the second direction, the method further comprises: obtaining the movement parameters of the first movement module and / or the second movement module; determining the impact compensation parameters based on the movement parameters; generating a third driving signal based on at least the impact compensation parameters; outputting the third driving signal to the third movement module to control the change of the measured position of the object table in the third direction to be less than the third preset error window.

[0011] According to the method of some embodiments of the present application, when the first movement module and the second movement module of the object table are controlled to move in the first direction and the second direction respectively so that the object table reaches the first target position in the first direction and the second target position in the second direction, the method further comprises: obtaining the scanning start position in the third direction; obtaining the movement parameters of the first movement module and / or the second movement module; determining the impact compensation parameters based on the movement parameters; generating a fourth driving signal based on the scanning start position and the impact compensation parameters through the third PIV control loop; outputting the fourth driving signal to the third movement module to control the movement of the third movement module until the difference between the measured position of the object table in the third direction and the scanning start position is less than the third preset error window.

[0012] According to the method of some embodiments of the present application, the movement parameters include acceleration and / or acceleration change rate.

[0013] According to the method of some embodiments of the present application, the impact compensation parameter is calculated based on the following formula: Uz=Kx(ACCx+Xd×JKx×Ct)+Ky(ACCy+Yd×JKy×Ct); wherein Uz is the impact compensation parameter, Kx and Ky are respectively a first preset proportional coefficient and a second preset proportional coefficient, ACCx and ACCy are respectively an acceleration of the first motion module and an acceleration of the second motion module, Xd and Yd are respectively a first preset motion direction factor and a second preset motion direction factor, JKx and JKy are respectively an acceleration change rate of the first motion module and an acceleration change rate of the second motion module, and Ct is a preset control period.

[0014] According to the method of some embodiments of the present application, the third driving signal is generated based at least on the impact compensation parameter, comprising: generating the third driving signal based on the measured position of the object table in the third direction and the impact compensation parameter by a third PIV control loop.

[0015] According to the method of some embodiments of the present application, the input signal of the current loop in the third PIV control loop comprises the impact compensation parameter.

[0016] According to the method of some embodiments of the present application, after the first motion module and the second motion module of the object table are controlled to move in the first direction and the second direction respectively so that the object table reaches the first target position in the first direction and the second target position in the second direction, the method further comprises: controlling the third motion module to move in the third direction so that the object table reaches a scanning start position in the third direction; and controlling the third motion module to move in the third direction so that the object table reaches the scanning start position in the third direction, comprising: obtaining the scanning start position in the third direction; generating a fifth driving signal based on the scanning start position by a third PIV control loop; and outputting the fifth driving signal to the third motion module to control the third motion module to move until the difference between the measured position of the object table in the third direction and the scanning start position is less than a third preset error window.

[0017] According to the method of some embodiments of the present application, the third motion module of the object table is controlled to move in the third direction so that the object table moves one or more times in the third direction from the scanning start position in the third direction, wherein one movement comprises: determining a scanning target position based on the measured position of the object table before the one movement and a preset step distance; generating a sixth driving signal based on the scanning target position by a third PIV control loop; and outputting the sixth driving signal to the third motion module to control the third motion module to drive the object table to complete the one movement in the third direction; or comprises: determining a scanning target position based on the scanning start position and a preset step distance; generating a sixth driving signal based on the scanning target position by a third PIV control loop; and outputting the sixth driving signal to the third motion module to control the third motion module to drive the object table to complete the one movement in the third direction.

[0018] The method according to some embodiments of the present application further comprises: determining the focus position of the object table from the position corresponding to the one or more movements in the third direction; determining the focus position of the object table from the position corresponding to the one or more movements in the third direction comprises: obtaining the focus signal of the focus sensor on the object to be photographed at the position corresponding to the one or more movements; determining the position corresponding to the focus signal satisfying the preset condition as the focus position; the focus sensor is located above the object table, and the focus direction of the focus sensor is consistent with the focus direction of the photographing device; wherein the preset condition comprises that the signal intensity of the focus signal is greater than a set intensity threshold.

[0019] The method according to some embodiments of the present application further comprises: obtaining the measurement position of the object table in the first direction, the second direction and the third direction respectively after controlling the third movement module to move in the third direction so that the object table reaches the focus position; determining the first position error value of the measurement position of the object table in the first direction and the first target position; determining the second position error value of the measurement position of the object table in the second direction and the second target position; determining the third position error value of the measurement position of the object table in the third direction and the focus position; determining that the focusing is completed when the first position error value does not exceed the first preset error window, the second position error value does not exceed the second preset error window and the third position error value does not exceed the third preset error window.

[0020] One or more embodiments of the present application further provide an automatic focusing system, comprising: a planar motion control module configured to control a first movement module and a second movement module of an object table to move in a first direction and a second direction respectively, so that the object table reaches a first target position in the first direction and a second target position in the second direction; a focal plane search control module configured to control a third movement module of the object table to move in a third direction, so that the object table moves in the third direction one or more times from a scanning starting position in the third direction, and the displacement of each movement is a preset step distance; a focus movement control module configured to control the third movement module to move in the third direction, so that the object table reaches a focus position; the focus position is determined from the position corresponding to the one or more movements in the third direction; wherein the object table is configured to carry an object to be photographed; the third direction is consistent with the focus direction of a photographing device located above the object table, the first direction and the second direction are located in the same plane, and the plane is perpendicular to the third direction.

[0021] One or more embodiments of the present application further provide an automatic focusing device, comprising a storage medium and a processor, the storage medium stores computer instructions, and the processor is configured to execute at least part of the computer instructions to implement the method according to some embodiments of the present application.

[0022] The one or more embodiments of the present application further provide a computer program product comprising computer instructions or a computer program, which, when executed by a processor, can implement the method of some embodiments of the present application.

[0023] The beneficial effects that the embodiments of the present application can bring include but are not limited to: (1) first moving the object table in the plane of the first direction and the second direction to make the imaging area of the photographed object enter the imaging field of view of the photographing device, and then making the object table finely scan in the third direction for multiple times at a preset step distance, so that the photographed object can reach a better focusing position, effectively improving the accuracy and speed of the focusing process; (2) using a PIV control loop to generate a driving signal, which can simultaneously realize position control and speed control, so that the object table can quickly and smoothly reach the target position in the corresponding direction; (3) before the scanning motion, the object table reaches the scanning starting position in the third direction, effectively saving the scanning time; (4) impact compensation control is performed on the third motion module while the first motion module and / or the second motion module are moving, which can effectively reduce the oscillation of the third motion module or the object table in the third direction, and shorten the corresponding setting time; (5) the step distance of the scanning motion is set to be within 20 nm, which effectively improves the scanning precision and helps to find the best focusing position or focal plane in the focusing direction; (6) after the object table reaches the focusing position, the arrival of each motion module is confirmed again, which helps to ensure that the photographed object accurately stays at the focusing position when the photographing device is imaging; (7) the arrival of each motion link is detected during the focusing process, which can timely find the deficiencies of the equipment or algorithm and make adjustments, ensuring the focusing efficiency. It should be noted that different embodiments can produce different beneficial effects, and in different embodiments, the beneficial effects that can be produced can be any one or a combination of the above, or any other beneficial effects that can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0024] The present application will be further illustrated in the form of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. The same reference numbers in the drawings represent the same structures or steps.

[0025] FIG. 1 is a structural schematic diagram of a focusing device according to some embodiments of the present application.

[0026] FIG. 2 is an exemplary flowchart of an auto-focusing method according to some embodiments of the present application.

[0027] FIG. 3 is a structural schematic diagram of a PIV control loop according to some embodiments of the present application.

[0028] FIG. 4 is a schematic diagram of an impact compensation control flow according to some embodiments of the present application.

[0029] FIG. 5 is a structural schematic diagram of a PIV control loop, according to some embodiments of the present application.

[0030] FIG. 6 is an exemplary block diagram of an auto-focusing system, according to some embodiments of the present application. DETAILED DESCRIPTION

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the embodiments will be described in detail below with reference to the accompanying drawings. Obviously, the following description is some examples or embodiments of the present application, and for those skilled in the art, without creative labor, the technical solutions or means disclosed in the present application can also be applied to other scenarios according to the technical content.

[0032] It should be understood that the "system", "device", "unit" and / or "module" used in the present application is a method for distinguishing different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the words can be replaced by other expressions.

[0033] Unless otherwise specified, the technical terms of components, elements, etc. described in the present application are not specified by the singular, and can also include the plural. Generally, the terms "include", "contain" and the like only indicate the inclusion of the steps, elements or components explicitly identified, and these steps, elements and components do not constitute an exclusive list, and the method or device described can also include other steps or components.

[0034] Flowcharts are used in the present application to illustrate the operation steps performed by the device or system of the related embodiments, but the order used to describe these steps should not be understood as a limitation on the execution order of the steps, unless otherwise specified. Those skilled in the art can adjust the execution order of these steps according to the knowledge information conveyed by the embodiments of the present application, and the adjustment includes but is not limited to the reversal of the sequence, the combination of multiple steps and the splitting of a step.

[0035] In the field of precision manufacturing technology, it is important to determine the error information of the object being processed. For example, in the production process of semiconductor chips, the target circuit pattern needs to be made on the substrate such as silicon wafer, wafer, etc. Specifically, a layer of highly photosensitive glue is coated on the surface of the substrate, and then a specific light (such as ultraviolet light, deep ultraviolet light, and extreme ultraviolet light) is used to irradiate the substrate surface through a mask containing the target circuit pattern information. The glue irradiated by the light will react, so that after development, the irradiated area will have a different effect from the non-irradiated area, thereby "copying" the target circuit image to the substrate. In order to improve the integration of chips, multiple circuit layers are often arranged in semiconductor chips. For this purpose, a lithography process is often used to make circuit patterns on different layers of the substrate. For example, a first layer of mask is used to expose the substrate, and then a second layer of mask is used to expose the substrate again. The projection of the first layer pattern formed on the substrate by the first layer mask and the second layer pattern formed on the substrate by the second layer mask in a certain direction of the substrate (such as the direction perpendicular to the plane of the substrate) should be accurately overlaid together, so as to be consistent with the final target circuit pattern. However, in actual production, there may be errors between the actual pattern formed on the substrate and the target pattern, such as the relative positional deviation between the projection of the first layer pattern and the second layer pattern, which can be understood as a lithography error or a processing error.

[0036] In order to improve production efficiency, it is necessary to measure and control the processing error information. In some embodiments, the error information of the object being processed can be determined by imaging technology. Specifically, a high-resolution camera is used to accurately focus on the object being processed to obtain a high-definition image, and image processing technology is used to process the image to obtain the error data of the object being processed. As can be seen, whether the object being processed can be accurately focused will affect the processing quality and efficiency.

[0037] Figure 1 is a structural schematic diagram of a focusing device according to some embodiments of the present application. As shown in Figure 1, the focusing device 100 includes a first motion module 101, a second motion module 102, a third motion module 103, and a stage 104. Above the stage 104 can be disposed a photographing device (not shown in the figure) and other auxiliary focusing devices, such as a focusing sensor 106. The stage 104 is used to carry an object 105 to be photographed, and in some embodiments, the stage 104 and the object 105 to be photographed can be collectively regarded as a load. The three motion modules are used to drive the stage 104 to move in three different directions, so as to move the stage 104 to an appropriate focusing position. The appropriate focusing position can be a position at which the object 105 to be photographed is on the focal plane of the photographing device, or a position at which the object 105 to be photographed is near the focal plane of the photographing device. The focal plane refers to a plane that passes through the external focal point of the photographing device and is perpendicular to the principal axis of the photographing device. Proper arrangement of the focusing device can enable the stage 104 to keep its plane parallel to the focal plane during movement. In some embodiments, the third motion module 103 is capable of moving in a third direction, which is consistent with the focusing direction of the photographing device above the stage. The focusing direction refers to a straight line direction that can intersect the focal plane of the photographing device, for example, the focusing direction can be consistent with or parallel to the principal axis of the photographing device. For example, the third direction can be the vertical direction in Figure 1. The first motion module 101 and the second motion module 102 are capable of moving in a first direction and a second direction, respectively. The first direction and the second direction are in the same plane, and specifically, can be in a plane that is perpendicular to the third direction. For example, the first direction can be the left-right direction in Figure 1, and the second direction can be the in-out direction of the figure relative to the paper, i.e., the second direction is perpendicular to the first direction.

[0038] In some embodiments, a motion module (e.g., the first motion module 101, the second motion module 102, or the third motion module 103) can include a driver, a power device, and a motion component. The driver is configured to receive a driving signal or a control instruction of a control device, and output a corresponding voltage signal or a current signal. The power device is configured to receive the voltage signal or the current signal, and convert it into mechanical energy. The power device can be an electric machine, such as a linear motor, a servo motor, a stepper motor, a voice coil motor, an ultrasonic motor, etc. The motion component is configured to move in a preset direction (e.g., the first direction, the second direction, or the third direction) under the driving of the power device. As an example, the motion component can include a rotating wheel, a sliding block, etc., which can move under the driving of the power device. In some embodiments, a plurality of motion modules can be stacked, for example, one motion module is arranged on another motion module. Taking FIG. 1 as an example, the second motion module 102 can be stacked on the first motion module 101, and the third motion module 103 can be stacked on the second motion module 102. The object table 104 can be arranged on the third motion module 103, and can be fixed on the third motion module 103. As shown in FIG. 1, a track can be arranged on the workbench in the first direction, and the motion component of the first motion module 101 can move and stop on the track. The second motion module 102 can move and stop relative to the first motion module 101. As an example, a sliding rail can be fixed on the upper surface of the first motion module 101 in the second direction, and the motion component of the second motion module 102 can slide along the sliding rail in the second direction. The third motion module 103 can move and stop relative to the second motion module 102. As an example, a support can be arranged on the second motion module 102, the extension direction of the support is consistent with the third direction, a track is arranged on the support, and the motion component of the third motion module 103 can move up and down along the track. The three motion modules move in the corresponding directions, and the object table 104 can focus on different regions of the surface of the photographed object 105.

[0039] When the photographed object 105 is at a position on the focal plane or within a certain distance from the focal plane, the photographing device can capture a high-definition image of the photographed object 105, which will help improve the accuracy of the obtained processing error. At present, in the field of precision manufacturing, the depth of field of the high-magnification lens of the photographing device is generally in the micron to sub-micron level. When the movement accuracy of the focusing equipment movement module is limited, it may not be possible to achieve high-precision focusing. For example, the movement step of the movement module is large, for example, the movement step is 200 nm. If the preferred focusing position (including the position of the object table when the photographed object is on the focal plane or within a certain distance from the focal plane) is distributed within 200 nm in the focusing direction, it is difficult to move the photographed object on the object table to the best focal plane position, and further difficult to capture a higher definition image. Alternatively, due to the limited movement accuracy of the movement module, the movement module may need to move back and forth in the corresponding movement direction multiple times in order to find a better focusing position, further causing the problem of slow focusing, which limits the production efficiency of the whole machine.

[0040] To this end, some embodiments of the present application propose an auto-focusing method to improve the focusing accuracy and / or focusing speed.

[0041] FIG. 2 is an exemplary flowchart of an auto-focusing method provided by some embodiments of the present application. In some embodiments, the flow 200 shown in FIG. 2 can be executed by a control device, such as a lower computer, to control the movement of the object table, such as to control the movement of the movement module shown in FIG. 1 to drive the movement of the object table 104. Specifically, the flow 200 can be implemented by an auto-focusing system 600 deployed on the control device. As shown in FIG. 2, the flow 200 can include the following steps.

[0042] Step 210, control the first movement module and the second movement module of the object table to move in the first direction and the second direction respectively, so that the object table reaches the first target position in the first direction and the second target position in the second direction. In some embodiments, step 210 can be implemented by a planar motion control module 610.

[0043] In some embodiments, the first target position and the second target position can be determined based on the region on the photographed object to be focused or imaged. Taking a wafer (or a silicon wafer) as the photographed object as an example, a two-dimensional coordinate system is established with the center of the wafer as the origin, and the center point of the region to be focused can be (25, 25) (unit: millimeter, mm). In this way, the first target position and the second target position can be determined so that when the first movement module and the second movement module drive the object table to reach the first target position in the first direction and the second target position in the second direction respectively, the point (25, 25) on the wafer is translated to the imaging field of view or the main optical axis of the photographing device.

[0044] The PIV control loop combines a position control (position loop) and a speed control (speed loop). The position loop adopts proportional (P) control, and the speed loop adopts proportional-integral (PI) control. Since the PIV control loop considers both position error and speed error, the position control is performed while the speed control is performed, and thus the tuning control effect of the PIV control loop is better. FIG. 3 is a structural schematic diagram of the PIV control loop in some embodiments of the present application. As shown in FIG. 3, the PIV control loop includes an innermost current loop, a middle speed loop, and an outermost position loop. The input signal of the position loop includes a target position and a measured position, and the position loop generates a position loop output signal based on the error between the target position and the measured position. The input signal of the speed loop includes the position loop output signal and a speed feedback signal, and the speed loop generates a speed loop output signal based on the error between the position loop output signal and the speed feedback signal. The speed feedback signal can be a measured speed or can be calculated based on the measured position. As an example, the speed feedback signal can be obtained by differentiating or differentiating (s operator in FIG. 3) the measured position at multiple time points. The input signal of the current loop includes the speed loop output signal and a current feedback signal, and the current loop generates a current loop output signal based on the error between the speed loop output signal and the current feedback signal. The current loop output signal is also the driving signal of the PIV control loop. The current feedback signal can reflect the size of the driving current output by the driver to the power device, and can be obtained by a current sampling circuit (such as a sampling resistor, a sampling inductor, etc.). The current has better sensitivity to system changes, and the introduction of the current loop control in the PIV control loop can better control the speed and adjust the load matching.

[0045] In some embodiments, the PIV control loop can also introduce a speed feedforward signal and an acceleration feedforward signal. The input signal of the speed loop can also include the speed feedforward signal, and the speed loop can generate the speed loop output signal based on the error between the superposition result of the position loop output signal and the speed feedforward signal and the speed feedback signal. The superposition can be summation in arithmetic operation, or can be further weighted summation, arithmetic average, or other fusion methods. Similarly, the input signal of the current loop can also include the acceleration feedforward signal, and the current loop can generate the current loop output signal based on the error between the superposition result of the speed loop output signal and the acceleration feedforward signal and the current feedback signal. In some embodiments, the speed feedforward signal and the acceleration feedforward signal can be determined by multiple debugging of the PIV control loop, for example, the speed feedforward signal and the acceleration feedforward signal can be adjusted to obtain their optimal values according to the control effect of the PIV control loop on the motion module. When the PIV control loop is put into use, the values of the speed feedforward signal and the acceleration feedforward signal can remain constant.

[0046] In view of the excellent speed control capability of the PIV control loop, in some embodiments, the first driving signal can be generated by the first PIV control loop based on the first target position and output to the first motion module. In some embodiments, the first driving signal is first input to a driver in the first motion module, and the driver outputs a control current signal or a control voltage signal to a power device of the first motion module based on the first driving signal. The power device converts electrical energy into mechanical energy, and finally drives the moving part of the first motion module to move in the first direction until the measured position of the stage in the first direction is within a first preset error window from the first target position. The measured position of the stage in the first direction can be obtained by an optical encoder, a grating ruler or the like sensor. The grating ruler can obtain higher precision position information. The first preset error window can be determined according to the control precision. For example, the first preset error window can be 50 nm, 20 nm, 10 nm or less. In some embodiments, when it is detected that the measured position of the stage in the first direction is within the first preset error window from the first target position and lasts for a preset time length, it can be determined that the stage or the first motion module has moved to the position in the first direction. At this time, the PIV control loop can set the first driving signal to zero to stop the first motion module or continuously output the first driving signal to stably control the position of the stage in the first direction within the first preset error window from the first target position. The preset time length can be 50-100 control periods, and the control period can be 0.3 ms, 0.2 ms, 0.8 ms, 1 ms or 2 ms, etc. If the stage cannot stably enter the first preset error window from the first target position (hereinafter referred to as the first preset error window of the first target position) or the time for the stage to move from the initial position in the first direction to stably enter the first preset error window of the first target position exceeds a time threshold, it can be determined that the positioning is timed out. At this time, the staff can be notified to check and repair the motion module and the like, or the motion control algorithm can be debugged. It is not difficult to understand that the motion module can quickly and stably drive the stage to enter the preset error window of the target position, which will help to greatly shorten the time for the stage to move during focusing, and thus improve the focusing speed. Appropriately setting the time threshold for determining whether the positioning is timed out will help to improve the yield. For example, the aforementioned time threshold can be set to 200 ms, 170 ms, 120 ms, etc.

[0047] In some embodiments, the second driving signal can be generated by the second PIV control loop based on the second target position and output to the second motion module. The measured position of the object table in the second direction can be obtained by a sensor such as an optical encoder, a grating ruler, etc. The generation of the second driving signal by the second PIV control loop based on the second target position is similar to that of the first PIV control loop, and more details can be found in the foregoing description, which will not be repeated here. The specific values of the second preset error window, the preset time length corresponding to the second direction, and the time threshold can be the same as or different from the corresponding values of the first motion module. For example, the first preset error window is 15 nm, and the second preset error window is 12 nm.

[0048] It should be understood that the prefixes "first", "second", "third", etc. in the present application are mainly used for differentiation in expression, and should not be regarded as a substantial limitation on the subsequent terms or technical features.

[0049] The PIV control loop can control the motion module in position and speed, so that the motion of the motion module is more stable, and at the same time, the whole setting time can be effectively shortened, and the phenomenon of timeout after reaching the position can be avoided.

[0050] In step 220, the third motion module of the object table is controlled to move in the third direction, so that the object table moves one or more times in the third direction from the scanning start position in the third direction, and the displacement of each movement is a preset step distance. In some embodiments, step 220 can be implemented by the focal plane search control module 620.

[0051] In some embodiments, when the first motion module and the second motion module drive the object table to reach the first target position in the first direction and the second target position in the second direction respectively, it means that the region to be focused on the wafer enters the imaging field of view of the shooting device, at this time, the object table needs to be moved in the third direction, i.e. the focusing direction, to find a better focusing position. The scanning start position can be the position where the scanning motion starts, i.e. the position of the object table in the third direction when it reaches the first target position and the second target position. In other embodiments, the scanning start position can also be the starting position of a plurality of possible focusing positions in the third direction. More details about this can be found in the following description. The plurality of possible focusing positions can correspond to a region in the third direction, also known as a scanning region.

[0052] The third motion module needs to drive the object table to find the focus position from the scanning start position through one or more motions (or one scanning motion). The one scanning motion makes the object table move in the third direction by a preset step distance. The size of the preset step distance affects the scanning resolution, and the number of scanning motions can be determined according to the distribution area of the focus position in the third direction and the preset step distance. When the preset step distance is large, the time consumption of the object table traversing the scanning area is shortened, but the focus position may not be found in one traversal, so the object table may need to traverse the scanning area from the scanning start position multiple times, increasing the focus time. The most likely situation is that even after multiple traversals, the preset step distance of the scanning motion cannot make the object table reach the better focus position. When the preset step distance is set too small, the number of scanning motions will increase significantly, which will still make the scanning time relatively long and increase the time of the focusing process. Therefore, the preset step distance can be appropriately selected to find the better focus position in less time. In some embodiments, the preset step distance can be 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, etc.

[0053] In some embodiments, the third PIV control loop can generate a driving signal to control the third motion module to move in the third direction. For one scanning motion, the scanning target position can be determined based on the scanning start position and the preset step distance. Specifically, the scanning target position can be the sum of the scanning start position and the preset step distance. The third PIV control loop generates a sixth driving signal based on the scanning target position, and outputs the sixth driving signal to the third motion module to control the third motion module to drive the object table to complete one scanning motion in the third direction. The working principle of the third PIV control loop can be referred to the description of FIG. 3. For multiple scanning motions, for the first scanning motion, the scanning target position can be determined based on the scanning start position and the preset step distance, and the third PIV control loop generates a sixth driving signal based on the scanning target position, and outputs the sixth driving signal to the third motion module to control the third motion module to drive the object table to complete the first scanning motion in the third direction. In subsequent scanning motions, the scanning target position is determined based on the measured position of the object table before the motion and the preset step distance, and the third PIV control loop generates a sixth driving signal based on the scanning target position, and outputs the sixth driving signal to the third motion module to control the third motion module to drive the object table to complete the current motion in the third direction. In this way, the preset number of scanning motions are completed.

[0054] After the third movement module drives the object table to complete a scanning movement, a focusing operation can be performed to determine the focusing position from the positions corresponding to one or more scanning movements. In some embodiments, the step can be implemented by the focusing position determination module 640. The position corresponding to the scanning movement can be the position of the object table in the third direction after completing the current scanning movement. In some embodiments, the focusing operation can be performed by a shooting device located above the object table or by a focusing sensor located above the object table. The object table can obtain a focusing signal from the shooting device or the focusing sensor after completing each scanning movement, and record the position corresponding to the current scanning movement and the focusing signal. Taking the focusing sensor as an example, the focusing sensor can emit a signal, such as a laser signal or an infrared signal, for focusing along the focusing direction towards the wafer surface. The emitted signal is reflected on the wafer surface, and the focusing sensor receives the reflected signal and obtains the intensity of the reflected signal as the intensity of the focusing signal. The greater the intensity of the focusing signal, the closer the current position of the object table to the focal plane. In order to enable the focusing signal to accurately reflect the focusing effect of the shooting device, the position of the focusing sensor can be adjusted so that the emission path and reflection path of the focusing signal are consistent or parallel with the main optical axis of the shooting device, and the plane where the light-emitting hole of the focusing sensor is located is coplanar with the plane where the lens of the shooting device is located.

[0055] When the object table completes a preset number of scanning movements, the focusing signal that meets the preset condition can be determined from the focusing signals corresponding to the scanning movements, and the position corresponding to the focusing signal is determined as the focusing position. As an example, the preset condition can include that the signal intensity of the focusing signal is greater than a set intensity threshold. For example, the positions corresponding to the focusing signals with signal intensities greater than the set intensity threshold among the plurality of focusing signals can be determined as the focusing position, or the focusing signal with the maximum signal intensity among the plurality of focusing signals can be compared with the set intensity threshold, and when the maximum signal intensity is greater than the set intensity threshold, the position corresponding to the focusing signal with the maximum signal intensity is determined as the focusing position.

[0056] In step 230, the third movement module is controlled to move in the third direction so that the object table reaches the focusing position. In some embodiments, step 230 can be implemented by the focusing movement control module 630.

[0057] As described above, the focus position can be determined from the positions corresponding to the one or more scanning motions. When the focus position is determined, the stage can have moved to another position in the third direction, and thus the third motion module needs to be controlled again to move the stage to the focus position. Specifically, a seventh driving signal can be generated based on the focus position by the third PIV control loop, and output to the third motion module to control the third motion module to move until the difference between the measured position of the stage in the third direction and the focus position is within the third preset error window. The working principle of the third PIV control loop can refer to the description of FIG. 3 above, where the target position is the focus position, and the measured position is the measured position of the stage in the third direction, which can be obtained by an optical encoder, a grating ruler, or the like. The third preset error window can be determined according to the control accuracy, and the third preset error window can be the same as or different from the first preset error window, for example, the third preset error window can be smaller. In some embodiments, when it is detected that the difference between the measured position of the stage in the third direction and the scanning start position is within the third preset error window and lasts for a preset time length, it can be determined that the stage or the third motion module is moved to the position in the third direction, and at this time the third PIV control loop can set the seventh driving signal to zero to stop the third motion module or continuously output the seventh driving signal to control the position of the stage in the third direction to be within the third preset error window from the focus position. The preset time length can be 50-100 control periods (such as the control period of the control device), and the control period can be 0.3 ms, 0.2 ms, 0.8 ms, 1 ms, or 2 ms, etc. If the stage cannot stably enter the third preset error window from the focus position or the time from the start of the focus motion of the stage in the third direction to the final stable entry into the third preset error window from the focus position is too long, it can be determined that the positioning is timed out. At this time, the staff can be notified to check and repair the motion module and the like, or the motion control algorithm can be debugged.

[0058] When the third motion module drives the stage to move to the focus position or within the third preset error window from the focus position, the imaging device can be controlled to complete an imaging operation to obtain an image of the object to be photographed, such as a wafer.

[0059] In some optional embodiments, the flow 200 can further include a focus completion determining step, which can be implemented by the focus completion determining module 650. The focus completion determining step can be performed after the object table reaches the focus position or enters the third preset error window thereof, and can specifically include: acquiring the measured position of the object table in the first direction, the second direction, and the third direction, respectively; determining a first position error value of the measured position of the object table in the first direction and the first target position; determining a second position error value of the measured position of the object table in the second direction and the second target position; determining a third position error value of the measured position of the object table in the third direction and the focus position; and determining that the focus is completed when the first position error value does not exceed the first preset error window, the second position error value does not exceed the second preset error window, and the third position error value does not exceed the third preset error window. At this time, the imaging device can be controlled to complete an imaging operation to obtain an image of the object to be photographed, such as a wafer. If at least one of the first position error value, the second position error value, and the third position error value exceeds the corresponding preset error window, the corresponding motion module can be moved again by the PIV control loop to attempt to drive the object table to the target position in the corresponding direction. If the object table is difficult to stably enter the error window of the corresponding target position or takes too much time to enter the error window of the corresponding target position, an alarm signal can be generated to notify the staff to intervene. Specifically, the staff can overhaul the motion module or debug the motion control method.

[0060] Since the three motion modules can be difficult to be ideally decoupled from each other in structure or transmission relationship, when part of the motion modules move, they can impact or interfere with other motion modules, so that the object table can deviate from the target position in some directions. For example, when the object table reaches the focus position in the third direction, it can deviate from the first target position in the first direction. Through the focus completion determining step, the imaging device can obtain a high-definition image of the object to be photographed in an accurate focus state.

[0061] As described above, in other embodiments, the scanning starting position can also be the starting position of the possible focus positions in the third direction. For example, the object table can gradually rise (approach the imaging device) from the scanning starting position to reach the focus position, or the object table can gradually descend (move away from the imaging device) from the scanning starting position to reach the focus position. The scanning starting position can be estimated in advance according to the outer focus position of the imaging device. By estimating the scanning starting position, the number of scanning movements of the object table can be reduced, thereby shortening the time for finding a better focus position and improving the yield.

[0062] In some optional embodiments, the flow 200 can further include controlling the third motion module to move in the third direction so that the object table reaches the scanning start position in the third direction. This step can be performed between the step 210 and the step 220, or simultaneously with the step 210.

[0063] In some embodiments, after the first motion module and the second motion module drive the object table to reach the first target position in the first direction and the second target position in the second direction respectively, the third motion module is controlled to move in the third direction so that the object table reaches the scanning start position in the third direction. Specifically, a fifth driving signal can be generated by a third PIV control loop based on the scanning start position, and the fifth driving signal is output to the third motion module to control the movement of the third motion module until the difference between the measured position of the object table in the third direction and the scanning start position is not more than a third preset error window. The working principle of the third PIV control loop can be referred to the description of FIG. 3 above, where the target position is the scanning start position, and the measured position is the measured position of the object table in the third direction, which can be obtained by sensors such as photoelectric encoders, grating scales, etc. The third preset error window can be determined according to the control accuracy, and the third preset error window can be the same as or different from the first preset error window, for example, the third preset error window can be smaller. In some embodiments, when it is detected that the difference between the measured position of the object table in the third direction and the scanning start position is not more than the third preset error window and lasts for a preset time length, it can be determined that the object table or the third motion module is moved to the position in the third direction, at this time, the PIV control loop can set the third driving signal to zero so that the third motion module stops or continuously output the third driving signal to stably control the stopping position of the object table in the third direction within the third preset error window from the scanning start position. The preset time length can be 50-100 control periods, and the control period can be 0.3 ms, 0.2 ms, 0.8 ms, 1 ms or 2 ms, etc. If the object table cannot stably enter the third preset error window of the scanning start position or the time from the initial position of the object table in the third direction to the final stable entry into the third preset error window of the scanning start position is too long, it can be determined that the positioning is timed out. At this time, the staff can be notified to check and repair the motion module and other equipment, or the motion control algorithm can be debugged.

[0064] Since the three motion modules can be difficult to idealize decoupling from each other in structure or transmission relationship, and the structure of the third motion module can be relatively more precise and smaller in mass than the first and second motion modules, the impact of the first and / or second motion modules on the third motion module when moving can be greater, and thus the third motion module can slide back and forth (also known as oscillation) around its current position when it starts to move in the third direction to drive the stage to the scanning starting position or complete the first scanning movement. This affects the subsequent motion control, for example, increasing the setting time of the third motion module. Therefore, in some optional embodiments, the process 200 further includes impact compensation control of the third motion module.

[0065] In some embodiments, the impact compensation control of the third motion module is performed at the same time as step 210. FIG. 4 is an impact compensation control process 211 according to some embodiments of the present application, which can be implemented by the impact compensation control module 660 in some embodiments. The process 211 can specifically include the following steps.

[0066] Step 2111, obtaining a motion parameter of the first motion module and / or the second motion module.

[0067] In some embodiments, the motion parameter can include acceleration or acceleration change rate or a combination of the two. As an example, the measured positions of the stage at multiple time points in the first direction can be obtained, and the acceleration of the first motion module in the first direction can be calculated by performing second-order differentiation on the measured positions at multiple time points, and the acceleration change rate of the first motion module in the first direction can be calculated by performing third-order differentiation on the measured positions at multiple time points. As another example, the acceleration of the first motion module in the first direction can be directly obtained by an acceleration sensor, and the acceleration change rate of the first motion module in the first direction can be calculated by performing first-order differentiation on the measured acceleration at multiple time points. In still other embodiments, the motion parameter of the motion module can be directly obtained from its driver by the control device. Taking the second motion module as an example, the output signal of its driver contains the acceleration and acceleration change rate of its moving part or stage in the second direction, and the driver can send the acceleration and acceleration change rate of the second motion module to the control device for control operation.

[0068] Step 2112, determining an impact compensation parameter based on the motion parameter.

[0069] In some embodiments, the impact compensation parameter can be calculated based on formula (1). Uz = Kx(ACCx + Xd x JKx x Ct) + Ky(ACCy + Yd x JKy x Ct) (1).

[0070] In the formula, Uz is the impact compensation parameter. Kx and Ky are respectively a preset first proportional coefficient and a second proportional coefficient, which can be obtained by debugging the motion module according to actual conditions in some embodiments. For details, refer to the relevant description below. ACCx and ACCy are respectively the acceleration of the first motion module and the acceleration of the second motion module. Xd and Yd are respectively a preset first motion direction factor and a second motion direction factor, which can be respectively determined according to the acceleration direction of the first motion module in the first direction and the acceleration direction of the second motion module in the second direction. As an example, if the acceleration ACCx of the first motion module is positive, Xd is 1, and otherwise -1. If the acceleration ACCy of the second motion module is positive, Yd is 1, and otherwise -1. JKx and JKy are respectively the acceleration change rate of the first motion module and the acceleration change rate of the second motion module. Ct is a preset control period, which can be the control period of the control device, and its value is determined by the control device itself and is a constant. As an example, the specific value of the control period can be 0.5ms, 0.25ms, etc.

[0071] The acceleration change rate multiplied by time is acceleration, so the data in the formula (1) in the bracket is all of acceleration. The formula (1) aims to obtain the acceleration in the first direction and the second direction, and generate impact compensation for the third motion module based on this. It should be understood that the formula (1) is only an example of calculating the impact compensation parameter. In other embodiments, only the first term or the second term of the formula (1) can be retained to calculate the impact compensation parameter. In still other embodiments, the acceleration or the acceleration change rate in the formula (1) can be omitted, and so on. Such modifications should be considered as embodiments disclosed in the present application, and the formula (1) should not be considered as the only means to calculate the impact compensation parameter.

[0072] In step 2113, a third driving signal is generated based at least on the impact compensation parameter.

[0073] In some embodiments, the third driving signal can be positively correlated with the impact compensation parameter.

[0074] In some embodiments, the third driving signal can be generated based on the measured position of the object table in the third direction and the impact compensation parameter simultaneously by a third PIV control loop. FIG. 5 is a schematic diagram of a structure of a PIV control loop according to some embodiments of the present application. As shown in FIG. 5, the PIV control loop includes a current loop in the innermost layer, a velocity loop in the middle layer, and a position loop in the outermost layer. In some embodiments, the input signals of the PIV control loop can further include a velocity feedforward signal and an acceleration feedforward signal. The related descriptions of the current loop, the velocity loop, the position loop, the velocity feedforward signal, and the acceleration feedforward signal can be found in FIG. 3, which will not be repeated here. Compared with FIG. 3, the PIV control loop shown in FIG. 5 further includes an impact compensation parameter. Specifically, the impact compensation parameter can be one of the input signals of the current loop. The current loop can generate the third driving signal based on the error between the superimposition result of the velocity loop output signal and the impact compensation parameter and the current feedback signal. The specific manner of superimposition can be found in the related description in FIG. 3, which will not be repeated here.

[0075] The impact compensation parameter can offset the impact of the first motion module and / or the second motion module on the third motion module to some extent. Outputting the third driving signal to the third motion module can control the change of the measured position of the object table in the third direction to be no more than the third preset error window. The measured position reflects the current position of the object table in the third direction. That is, when the first motion module and / or the second motion module move, the third driving signal can maintain the object table at the original position in the third direction as much as possible, effectively avoiding the impact of the object table in the third direction. When the object table needs to move in the third direction, it can quickly and stably enter the motion state, saving the time consumption of the focusing process.

[0076] The following describes how to obtain the values of the correlation coefficients in formula (1) in some embodiments in combination with the debugging process of the motion module. In some embodiments, the numerical range of Kx and Ky is [e -5 , e -3 ] respectively. Taking Kx as an example, a small value can be set for Kx, such as e -5 . At this time, the values of other parameters in formula (1) remain unchanged. The oscillation of the third motion module or the object table in the third direction is observed when the third driving signal generated based on the impact compensation parameter controls the third motion module. When the oscillation is large, Kx can be adjusted to twice the original value, i.e. 2 × e -5 . The oscillation of the third motion module or the object table in the third direction is observed again. If the vibration is still starting to decrease, the value of Kx can be doubled again, i.e. 2 × 2 × e -5Similarly, until the oscillation of the third motion module or the stage in the third direction is large again, at this time, the current Kx value can be reduced, for example, to 1 / 2 of the original value, and the oscillation of the third motion module or the stage in the third direction is observed again, and so on, to find the preferred value of Kx; or, the value of Kx that makes the oscillation minimum among the values of Kx can be taken as the final value of Kx. The process of determining the value of Ky can be similar to that of Kx. Of course, in some embodiments, the values of Kx and Ky can also be jointly adjusted.

[0077] As mentioned before, in some alternative embodiments, the step of controlling the third motion module to move in the third direction to make the stage reach the scanning start position in the third direction in the flow 200 can be performed simultaneously with the step 210, and at this time, the step performed simultaneously with the step 210 can also include the aforementioned impact compensation control. In some embodiments, the flow can be implemented by the impact compensation control module 660, which can specifically include the following steps.

[0078] Obtaining the scanning start position in the third direction.

[0079] Obtaining the motion parameters of the first motion module and / or the second motion module. For specific description of this step, please refer to the step 2111, which will not be repeated here.

[0080] Determining the impact compensation parameters based on the motion parameters. For specific description of this step, please refer to the step 2112, which will not be repeated here.

[0081] Generating a fourth driving signal based on the scanning start position and the impact compensation parameters by the third PIV control loop. For specific description of this step, please refer to the step 2113, which will not be repeated here.

[0082] The fourth driving signal is output to the third motion module to control the third motion module to move until the measured position of the object table in the third direction is within a third preset error window from the scanning start position. In some embodiments, when it is detected that the measured position of the object table in the third direction is within the third preset error window from the scanning start position for a preset time duration, it can be determined that the object table or the third motion module has moved to the position in the third direction. At this time, the PIV control loop can set the third driving signal to zero to stop the third motion module or continuously output the third driving signal to stably control the position of the object table in the third direction within the third preset error window from the scanning start position. The preset time duration can be 50-100 control cycles, and the control cycle can be 0.3 ms, 0.2 ms, 0.8 ms, 1 ms, or 2 ms, etc. The impact compensation parameter is introduced during the control of the movement of the object table in the third direction to the scanning start position, which can effectively eliminate the impact of the first motion module and / or the second motion module on the third motion module when the three motion modules move simultaneously, so that the object table can quickly and smoothly reach the scanning start position or within the third preset error window, effectively shortening the setting time. In some embodiments, the time duration of the movement of the object table from the stationary state to the scanning start position can also be detected. If the object table cannot stably enter the third preset error window from the scanning start position or the time taken by the object table to stably enter the third preset error window from the initial position in the third direction is too long, it can be determined that the positioning is timed out. At this time, the staff can be notified to check and maintain the motion module and other equipment, or the motion control algorithm can be debugged.

[0083] In some embodiments, the time duration of the entire focusing process can also be detected. If the total time duration of the movement of the object table from the stationary state (e.g., the time when step 210 starts to execute) to the final focusing position exceeds the set time duration, it can also be determined that the positioning is timed out. At this time, the staff can be notified to check and maintain the motion module and other equipment, or the motion control algorithm can be debugged. In this way, the motion time duration of the corresponding motion module can be monitored at each motion link, and the equipment or algorithm can be updated in a timely manner to ensure the accuracy and timeliness of the focusing and improve the yield.

[0084] FIG. 6 is an exemplary block diagram of an autofocus system according to some embodiments of the present application. As shown in FIG. 6, the autofocus system 600 can include a planar motion control module 610, a focal plane search control module 620, and a focusing motion control module 630.

[0085] The planar motion control module 610 is configured to control the first motion module and the second motion module of the object table to move in the first direction and the second direction, respectively, so that the object table reaches the first target position in the first direction and the second target position in the second direction.

[0086] The focal plane search control module 620 is configured to control the third movement module to move the objective table in the third direction, so that the objective table moves in the third direction from a scanning start position in the third direction for one or more times, and each time the displacement is a preset step distance. In some embodiments, the focal plane search control module 620 is further configured to control the third movement module to move in the third direction after the objective table reaches the first target position in the first direction and the second target position in the second direction, so that the objective table reaches the scanning start position in the third direction.

[0087] The focusing movement control module 630 is configured to control the third movement module to move in the third direction, so that the objective table reaches a focusing position; the focusing position is determined from the position corresponding to the one or more times of movement in the third direction.

[0088] In some optional embodiments, the auto-focusing system 600 can further include a focusing position determination module 640 configured to determine the focusing position of the objective table from the position corresponding to the one or more times of movement in the third direction.

[0089] In some optional embodiments, the auto-focusing system 600 can further include a focusing completion determination module 650 configured to, after the objective table reaches the focusing position: acquire a measured position of the objective table in the first direction, the second direction and the third direction respectively; determine a first position error value of the measured position of the objective table in the first direction and the first target position; determine a second position error value of the measured position of the objective table in the second direction and the second target position; determine a third position error value of the measured position of the objective table in the third direction and the focusing position; and determine that the focusing is completed when the first position error value does not exceed a first preset error window, the second position error value does not exceed a second preset error window, and the third position error value does not exceed a third preset error window.

[0090] In some alternative embodiments, the autofocus system 600 can further comprise a shock compensation control module 660 configured to, when the first movement module and the second movement module are moved in the first direction and the second direction respectively to make the stage reach the first target position in the first direction and the second target position in the second direction: acquire a movement parameter of the first movement module and / or the second movement module; determine a shock compensation parameter based on the movement parameter; generate a third driving signal based on at least the shock compensation parameter; and output the third driving signal to the third movement module to control a variation of a measured position of the stage in the third direction to be within a third preset error window. In some alternative embodiments, the shock compensation control module 660 is configured to, when the first movement module and the second movement module are moved in the first direction and the second direction respectively to make the stage reach the first target position in the first direction and the second target position in the second direction: acquire a scanning start position in the third direction; acquire a movement parameter of the first movement module and / or the second movement module; determine a shock compensation parameter based on the movement parameter; generate a fourth driving signal based on the scanning start position and the shock compensation parameter by a third PIV control loop; and output the fourth driving signal to the third movement module to control the third movement module to move until a difference between the measured position of the stage in the third direction and the scanning start position is within the third preset error window.

[0091] Further details of the modules can be found in the descriptions of FIGS. 2-5, which will not be repeated here. It should be understood that the system and its modules shown in FIG. 6 can be implemented in various ways. For example, in some embodiments, the system and its modules can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented by special logic; the software part can be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or a specially designed hardware. Those skilled in the art can understand that the above-mentioned method and system can be implemented using computer executable instructions and / or control codes contained in a processor, such as a carrier medium, a memory of a programmable device, etc. The system and its modules of the present application can not only be implemented by hardware circuits such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., but also by software, for example, executed by various types of processors, and also by a combination of the above-mentioned hardware circuits and software (e.g., firmware).

[0092] It should be noted that the above description of the system and its modules is for the convenience of description only, and does not limit the application to the scope of the embodiments. It can be understood that, for those skilled in the art, after understanding the principles of the system, various modules can be combined to form a subsystem connected with other modules, or some modules can be split to obtain more modules or multiple units under the module. Such variations are within the scope of the present application.

[0093] The above has described the basic concept, and it is obvious that the above detailed disclosure is only an example for those skilled in the art, and does not constitute a limitation on the application. Although it is not explicitly stated here, those skilled in the art can make various modifications, improvements and corrections to the application. Such modifications, improvements and corrections are taught in the application, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of the application.

Claims

1. An auto-focusing method characterized by, The method comprises: controlling a first motion module and a second motion module of a carrier platform to move in a first direction and a second direction respectively, so that the carrier platform reaches a first target position in the first direction and a second target position in the second direction; controlling a third motion module of the carrier platform to move in a third direction, so that the carrier platform moves in the third direction one or more times from a scanning starting position in the third direction, and each movement has a preset step distance; controlling the third motion module to move in the third direction, so that the carrier platform reaches a focusing position; the focusing position is determined from the one or more positions corresponding to the movement in the third direction; wherein the carrier platform is used to carry a photographed object; the third direction is consistent with a focusing direction of a photographing device located above the carrier platform; the first direction and the second direction are located in the same plane, and the plane is perpendicular to the third direction.

2. The method of claim 1, wherein, The first direction and the second direction are perpendicular; the preset step distance is not more than 20nm or not more than 10nm.

3. The method of claim 1, wherein, The second motion module is stacked on the first motion module, the third motion module is stacked on the second motion module, and the carrier platform is arranged on the third motion module.

4. The method of claim 1, wherein, controlling a first motion module of a carrier platform to move in a first direction, so that the carrier platform reaches a first target position in the first direction, comprising: obtaining the first target position in the first direction; generating a first driving signal based on the first target position through a first PIV control loop; outputting the first driving signal to the first motion module to control the movement of the first motion module, until the difference between the measured position of the carrier platform in the first direction and the first target position is not more than a first preset error window; controlling a second motion module of the carrier platform to move in a second direction, so that the carrier platform reaches a second target position in the second direction, comprising: obtaining the second target position in the second direction; generating a second driving signal based on the second target position through a second PIV control loop; outputting the second driving signal to the second motion module to control the movement of the second motion module, until the difference between the measured position of the carrier platform in the second direction and the second target position is not more than a second preset error window.

5. The method of claim 1, wherein, In the process of controlling a first motion module and a second motion module of a carrier platform to move in a first direction and a second direction respectively, so that the carrier platform reaches a first target position in the first direction and a second target position in the second direction, the method further comprises: obtaining the motion parameters of the first motion module and / or the second motion module; determining impact compensation parameters based on the motion parameters; generating a third driving signal based on at least the impact compensation parameters; outputting the third driving signal to the third motion module to control the change of the measured position of the carrier platform in the third direction to be not more than a third preset error window.

6. The method of claim 1, wherein, The method further comprises: acquiring a scanning start position in the third direction; acquiring motion parameters of the first motion module and / or the second motion module; determining an impact compensation parameter based on the motion parameters; generating a fourth driving signal based on the scanning start position and the impact compensation parameter by a third PIV control loop; outputting the fourth driving signal to the third motion module to control the third motion module to move until a difference between a measured position of the object table in the third direction and the scanning start position is less than a third preset error window.

7. The method according to claim 5 or 6, characterized in that, The motion parameters include acceleration and / or acceleration change rate.

8. The method of claim 7, wherein, The impact compensation parameter is calculated based on the following formula: Uz=Kx(ACCx+Xd×JKx×Ct)+Ky(ACCy+Yd×JKy×Ct); wherein Uz is the impact compensation parameter, Kx and Ky are preset first and second proportional coefficients respectively, ACCx and ACCy are acceleration of the first motion module and acceleration of the second motion module respectively, Xd and Yd are preset first and second motion direction factors respectively, JKx and JKy are acceleration change rate of the first motion module and acceleration change rate of the second motion module respectively, and Ct is a preset control period.

9. The method of claim 5, wherein, The method further comprises: generating a third driving signal based on the measured position of the object table in the third direction and the impact compensation parameter by a third PIV control loop.

10. The method according to claim 6 or 9, characterized in that, The input signal of a current loop in the third PIV control loop includes the impact compensation parameter.

11. The method of claim 1 or 5, wherein, The method further comprises: controlling the third motion module to move in the third direction to make the object table reach the scanning start position in the third direction; The controlling the third motion module to move in the third direction to make the object table reach the scanning start position in the third direction comprises: acquiring the scanning start position in the third direction; generating a fifth driving signal based on the scanning start position by a third PIV control loop; outputting the fifth driving signal to the third motion module to control the third motion module to move until a difference between a measured position of the object table in the third direction and the scanning start position is less than a third preset error window.

12. The method of claim 1, wherein, The controlling the third motion module to move in the third direction to make the object table reach the scanning start position in the third direction comprises: determining a scanning target position based on the measured position of the object table before the first movement and the preset step distance; generating a sixth driving signal based on the scanning target position through a third PIV control loop; outputting the sixth driving signal to the third movement module to control the third movement module to drive the object table to complete a movement in the third direction; or comprising: determining a scanning target position based on the scanning start position and the preset step distance; generating a sixth driving signal based on the scanning target position through a third PIV control loop; outputting the sixth driving signal to the third movement module to control the third movement module to drive the object table to complete a movement in the third direction.

13. The method of claim 1, wherein, further comprising: determining a focusing position of the object table from the position corresponding to the one or more movements in the third direction; the determining of the focusing position of the object table from the position corresponding to the one or more movements in the third direction comprises: obtaining a focusing signal of the photographed object by a focusing sensor when the object table is at the position corresponding to the one or more movements; determining the position corresponding to the focusing signal meeting a preset condition as the focusing position; the focusing sensor is located above the object table, and a focusing direction of the focusing sensor is consistent with a focusing direction of the photographing device; wherein the preset condition comprises that a signal intensity of the focusing signal is greater than a set intensity threshold.

14. The method of claim 1, wherein, after the control of the third movement module to move in the third direction to make the object table reach the focusing position, further comprising: obtaining a measured position of the object table in the first direction, the second direction and the third direction, respectively; determining a first position error value of the measured position of the object table in the first direction and the first target position; determining a second position error value of the measured position of the object table in the second direction and the second target position; determining a third position error value of the measured position of the object table in the third direction and the focusing position; determining that the focusing is completed when the first position error value does not exceed a first preset error window, the second position error value does not exceed a second preset error window, and the third position error value does not exceed a third preset error window.

15. An autofocus system, characterized by comprising: a planar motion control module configured to control a first movement module and a second movement module of an object table to move in a first direction and a second direction, respectively, to make the object table reach a first target position in the first direction and a second target position in the second direction; a focal plane search control module configured to control a third movement module of the object table to move in a third direction to make the object table move one or more times in the third direction from a scanning start position in the third direction, and a displacement of each movement is a preset step distance; a focusing motion control module configured to control the third movement module to move in the third direction to make the object table reach a focusing position, and the focusing position is determined from a position corresponding to the one or more movements in the third direction. The third direction is consistent with a focusing direction of a shooting device located above the object table. The first direction and the second direction are located in the same plane, and the plane is perpendicular to the third direction.

16. An auto-focusing device, comprising a storage medium and a processor, the storage medium storing computer instructions, and the processor being configured to execute at least part of the computer instructions to implement the method according to any one of claims 1-14.

17. A computer program product, comprising computer instructions or a computer program, when at least part of the computer instructions or the computer program is executed by a processor, the computer program product is capable of implementing the method according to any one of claims 1-14. ​

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