Multi-channel cross-station focusing method, device and medium

Abstract

The invention discloses a multi-channel cross-station focusing method, and the method comprises the steps: synchronously obtaining the three-dimensional height contour data of the surface of a measured object when the measured object is scanned at a first station; performing interpolation processing on the three-dimensional height contour data to generate predicted height data matched with the second station scanning path; mapping the predicted height data to a second station coordinate system based on a pre-calibrated coordinate system transformation matrix to obtain mapped height data; and in the second station scanning process, the mapped height data and the mechanical system error correction are combined, and a Z-axis execution mechanism is driven to realize dynamic focusing compensation. According to the invention, the three-dimensional height contour data of the surface of the measured object is synchronously pre-scanned during scanning at the first station, and then the focusing data is transmitted to the second station through operations such as interpolation processing, coordinate system conversion and error correction, so that a pre-scanning process for height measurement does not need to be executed at the second station, the wafer detection period is shortened, and the detection efficiency is improved. And the wafer detection efficiency is effectively improved.

Description

Technical Field

[0001] The present application relates to the field of precision measurement technology, and more specifically, to a multi-channel cross-station focusing method, equipment, and medium. Background Art

[0002] In the semiconductor manufacturing industry, wafer inspection requires extremely high precision, typically requiring a sensitivity of 80nm, meaning the minimum detectable defect size (generally referring to diameter) is 80nm. Existing wafer inspection technology based on laser interferometry can achieve a high sensitivity of 30nm, but it is slow and time-consuming.

[0003] Taking the inspection of wafers with a diameter of 150mm as an example, the inspection time of wafer inspection technology based on laser interference is often several hours. However, in the actual production line, the inspection time for wafers with a diameter of 150mm is required to be limited to within a few minutes, so this existing technology is difficult to apply to the actual production line.

[0004] Therefore, how to improve wafer detection efficiency while ensuring detection sensitivity has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In response to at least one defect or improvement need in the prior art, the present application provides a multi-channel cross-station focusing method, equipment and medium, which can effectively improve wafer detection efficiency while ensuring detection sensitivity to match the batch full inspection requirements before wafer production and shipment.

[0006] To achieve the above objectives, in a first aspect, the present application provides a multi-channel cross-station focusing method, comprising:

[0007] When the object to be measured is scanned by the first optical system at the first station, three-dimensional height profile data of the surface of the object to be measured is synchronously acquired;

[0008] interpolating the three-dimensional height profile data to generate predicted height data that matches a scanning path of a second optical system of a second station;

[0009] Based on a pre-calibrated coordinate system conversion matrix, the predicted height data is mapped to a second workstation coordinate system to obtain mapped height data;

[0010] During the scanning process of the second optical system of the second station, the mapped height data and the mechanical system error correction are combined to drive the Z-axis actuator to achieve dynamic focus compensation.

[0011] Furthermore, the interpolation process specifically includes:

[0012] According to the geometric relationship between the scanning paths of the first and second stations, the surface topography of the object to be measured is reconstructed through the bicubic spline interpolation algorithm based on the surface smoothness constraint of the object to be measured, and a continuous height distribution matching the number of scanning lines of the second station is generated.

[0013] Furthermore, the coordinate system conversion matrix is ​​constructed in the following manner:

[0014] Use a calibration plate with a fiducial mark to perform multi-station joint calibration, scanning at the first and second stations to obtain coordinate measurement values ​​of the same fiducial mark;

[0015] The translation and rotation angle between the first and second workstations are obtained by the least squares method, and a homogeneous transformation matrix with five degrees of freedom is constructed.

[0016] Furthermore, combining the mapped height data with the mechanical system error correction value, driving the Z-axis actuator to achieve dynamic focus compensation includes:

[0017] Set a reference mark on the fixture and measure the height values ​​H1 and H2 of the reference mark in the Z direction at the first and second stations respectively;

[0018] Obtain the Z-axis system error ΔZ=H2-H1, and add the Z-axis system error to all mapped height data.

[0019] Furthermore, the three-dimensional height profile data is obtained by:

[0020] The optical focus evaluation function method based on bright field imaging inverts the surface height distribution through the focus evaluation curve collected during line-by-line scanning.

[0021] Furthermore, the focus evaluation function method includes:

[0022] The improved Tenengrad gradient operator is used to calculate the high-frequency component intensity value of the image area within the ultraviolet spectrum:

[0023] F(x,y)=Σ[G_x(x,y) 2 +G_y(x,y) 2 ];

[0024] Among them, G_x(x,y) and G_y(x,y) represent the horizontal and vertical gradient components after Sobel operator processing respectively; F(x,y) represents the intensity value of the high-frequency component.

[0025] Furthermore, the dynamic focus compensation further includes:

[0026] During the station switching process, the XY displacement deviation of the robot arm is collected in real time through hardware triggering;

[0027] The influence of XY displacement deviation on height mapping is calculated based on the pre-established error transfer model, and the Z-axis compensation is corrected.

[0028] Furthermore, the first station is a high depth of field imaging system with a depth of field ≥ 5 μm;

[0029] The second station is a low depth of field imaging system with a depth of field ≤ 4 μm.

[0030] In a second aspect, the present application provides an electronic device comprising at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program, and when the computer program is executed by the processing unit, the processing unit is enabled to perform the steps of the multi-channel cross-station focusing method described in any one of the preceding items.

[0031] In a third aspect, the present application provides a storage medium storing a computer program executable by an access authentication device. When the computer program runs on the access authentication device, the access authentication device is enabled to perform the steps of the multi-channel cross-station focusing method described in any one of the preceding items.

[0032] In general, the above technical solutions conceived by this application can achieve the following beneficial effects compared with the existing technology:

[0033] The technical solution of the present application pre-scans the three-dimensional height profile data of the surface of the object to be measured simultaneously when scanning at the first station, and then transmits the focus data to the second station through interpolation processing, coordinate system conversion and error correction operations for focus compensation at the second station, so that there is no need to perform the pre-scanning process for height measurement at the second station, thereby shortening the wafer inspection cycle; in addition, the technical solution of the present application has no effect on the defect detection process of each optical system, that is, it will not affect the detection sensitivity of each optical system; in summary, the technical solution of the present application can shorten the total time of wafer defect detection while ensuring detection sensitivity, thereby effectively improving wafer detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 A core flow chart of a multi-channel cross-station focusing method provided in an embodiment of the present application;

[0036] Figure 2A schematic diagram of station switching scanning provided in an embodiment of the present application;

[0037] Figure 3 A comparison chart of the height difference of workstation switching data provided in the embodiment of the present application;

[0038] Figure 4 A schematic diagram of the height data interpolation processing provided in an embodiment of the present application;

[0039] Figure 5 A block diagram of an electronic device suitable for implementing the multi-channel cross-station focusing method described above is provided in an embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining this application and are not intended to limit this application. In addition, the technical features involved in the various embodiments of this application described below may be combined with each other as long as they do not conflict with each other.

[0041] The terms "first," "second," or "nth" in the specification, claims, or drawings of this application may be used to distinguish different objects or to describe a specific order, depending on the specific scenario. In addition, the terms "including" or "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products, or devices.

[0042] Silicon carbide wafers include substrates and epitaxial wafers. The substrate is made first, and then the epitaxial wafer is grown on the substrate. There are more than 9 types of defects on the substrate, and more than 15 types of defects on the epitaxial wafer. There are many types of defects, and it is difficult to detect all types of defects with one optical system. For example, only a few types of defects can be seen by bright field (i.e. high-magnification ultraviolet microscope). Some defects can only be detected by the combination of phase, dark field, PL optical systems, etc. For example, the product is placed on the fixture and moved to the first position (i.e. Figure 2 The position area shown by the dark green strip in the lower left corner corresponds to the scanning area of ​​the A and B optical systems. It is imaged by the A and B optical systems (the A and B optical systems are merged). A and B are photographed at the same time, and two images A and B are obtained. Then, it moves to the second position (along the Figure 2Move in the direction of the yellow arrow to the scanning area corresponding to the C optical system, that is, the area directly below the C optical system), be imaged by the C optical system, scan and take a picture to obtain a C image; then move to the third position (along Figure 2 Continue to translate in the direction of the yellow arrow until you reach the scanning area corresponding to the D optical system (i.e., the area directly below the D optical system). The D optical system will image the image and scan and take a picture to get a D picture. The magnification of each camera is different (A and B are different even though they were taken at the same time). Figure 2 Among them, A and B are brightfield and phase (combined in one optical system, but resulting in two images) optical systems, C is a darkfield optical system, and D is a PL optical system. According to the depth of field, A and B are high depth of field optical systems, with a depth of field generally exceeding 5μm or even 10μm, while C and D are low depth of field optical systems, with a depth of field generally below 4μm.

[0043] Although semiconductor equipment possesses a certain level of platform accuracy, this accuracy is generally at the submicron level, making it difficult to control accuracy below 100nm. For optical systems with a depth of field greater than 5μm, direct scanning and imaging can be achieved by relying on the accuracy of the mechanical platform, eliminating the need for autofocus. However, for optical systems with a depth of field less than 5μm, even slight defocus in the Z direction can result in severe image blur due to the smaller depth of field. To ensure image clarity, autofocus is required.

[0044] In the above example, the depth of field of optical systems A and B is above 5 μm and no autofocus is required; while the depth of field of optical systems C and D is below 4 μm and autofocus is required.

[0045] This application proposes a technical concept. When the object to be measured (wafer) is imaged and scanned at the A and B optical systems, the three-dimensional height profile of the object to be measured can be scanned synchronously, and then the corresponding three-dimensional height profile information can be transmitted to the C and D optical systems; when the object to be measured is imaged and scanned at the C and D optical systems, the C and D optical systems can make Z-axis motion planning based on the pre-acquired three-dimensional height profile information to achieve automatic focusing movement.

[0046] Typically, before the C and D optical systems scan the object to be measured, a process (also called a pre-scanning process) is added at the corresponding workstations of the C and D optical systems to perform a three-dimensional height profile scan of the object to be measured using a high-precision Z-axis altimeter to collect height data of the object to be measured for subsequent autofocusing of the C and D optical systems. Unlike the prior art, in the present application, the three-dimensional height profile of the object to be measured is synchronously acquired during the scanning process of the A and B optical systems. Therefore, there is no need to perform a three-dimensional height profile scan of the object to be measured using a high-precision Z-axis altimeter at the workstations corresponding to the C and D optical systems. This saves the time of performing a three-dimensional height profile scan of the object to be measured using a high-precision Z-axis altimeter at the C and D optical systems, thereby shortening the overall time of the entire detection cycle without affecting the detection accuracy.

[0047] However, when the above technical ideas were implemented on the production line, new problems arose:

[0048] First, due to the differences in the wafer scanning processes of the A and B optical systems and the C and D optical systems, for example, the A and B optical systems generally use 30 line scans to scan the entire wafer, while the C optical system generally uses 25 line scans to scan the entire wafer, and the D optical system generally uses 20 line scans to scan the entire wafer. As a result, the height measurement positions of the A and B optical systems when scanning the object to be measured are not on the paths that the C and D optical systems need to measure height. That is, the three-dimensional height profile data synchronously acquired during the scanning of the A and B optical systems cannot be directly applied to the autofocus of the C and D optical systems.

[0049] Secondly, when the mechanical system moves the object to be measured from the workstations corresponding to the A and B optical systems to the workstation corresponding to the C optical system, and also when the object to be measured is moved from the workstation corresponding to the C optical system to the workstation corresponding to the D optical system, the five degrees of freedom, namely X, Y, Z, jaw (pitch angle), and pitch (yaw angle), will change. This makes it easy for coordinate system deviations to occur due to workstation switching.

[0050] Third, when the mechanical system drives the object to be measured to switch workstations, certain mechanical errors will occur during the movement process.

[0051] The above problem directly leads to the fact that the three-dimensional height profile data synchronously acquired during the scanning of the A and B optical systems cannot be directly applied to the autofocus of the C and D optical systems.

[0052] In response to the first problem mentioned above, this application takes into account that the surface of the wafer is smooth enough, there are no sudden protrusions or depressions, and the heights at different positions on the wafer surface are smooth and gradual. Based on the above characteristics of the wafer surface, this application can obtain the height data of the height measurement positions required by the C optical system and the D optical system by interpolation based on the three-dimensional height profile data obtained synchronously during the scanning process of the A and B optical systems. In response to the second problem mentioned above, this application pre-constructs a coordinate system conversion matrix to map the height data obtained at the workstations corresponding to the A and B optical systems to the coordinate systems at the workstations corresponding to the C optical system and the D optical system, thereby solving the coordinate system deviation problem caused by workstation switching. In response to the third problem mentioned above, a mechanical error compensation mechanism is introduced in this application.

[0053] Based on the above technical concept, the overall technical route adopted by this application is: when scanning at the first station (for example, the stations corresponding to the A and B optical systems), the three-dimensional height profile data of the surface of the object to be measured is pre-scanned synchronously, and then the focus data is transmitted to the second station (for example, the station corresponding to the C optical system or the station corresponding to the D optical system) through interpolation processing, coordinate system conversion and error correction operations, so that there is no need to perform the pre-scanning process for height measurement at the second station, shortening the wafer detection cycle; in addition, the technical solution of this application has no effect on the defect detection process of each optical system, that is, it will not affect the detection sensitivity of each optical system; in summary, the technical solution of this application can shorten the total time of wafer defect detection while ensuring detection sensitivity, thereby effectively improving wafer detection efficiency. Reference Figures 1-4 A specific embodiment of the present application proposes a multi-channel cross-station focusing method, which may specifically include the following steps.

[0054] Step 1: When scanning the object to be measured by the first optical system at the first station, three-dimensional height profile data of the surface of the object to be measured is synchronously obtained.

[0055] In some embodiments, specifically, the method for obtaining the three-dimensional height profile data includes:

[0056] The optical focus evaluation function method based on bright field imaging inverts the surface height distribution through the focus evaluation curve collected during line-by-line scanning. The focus evaluation function method includes:

[0057] The improved Tenengrad gradient operator is used to calculate the high-frequency component intensity value of the image area within the ultraviolet spectrum:

[0058] F(x,y)=Σ[G_x(x,y) 2 +G_y(x,y) 2 ];

[0059] Among them, G_x(x,y) and G_y(x,y) represent the horizontal and vertical gradient components after Sobel operator processing respectively; F(x,y) represents the intensity value of the high-frequency component.

[0060] This application adopts the ultraviolet band focusing evaluation function method to avoid the failure problem of infrared / laser height detection system on transparent materials, and at the same time avoids the interference of the height detection spot on imaging.

[0061] In some embodiments, more specifically, when performing joint scanning at stations A and B (i.e., the first station mentioned above), a bright field image is collected through a high-magnification UV objective lens (NA = 0.9), and a height profile is constructed based on the Tenengrad gradient algorithm, with a sampling density of 50 points / mm. 2 When performing bright field scanning at stations A and B, the focus evaluation function data is collected synchronously through a high-magnification UV objective lens to construct a 50 point / mm 2 Compared to the traditional process where each workstation independently pre-scans, this embodiment reduces height measurement time by 65 seconds through multi-workstation data sharing, improving overall inspection efficiency by up to 30%.

[0062] Step 2: interpolate the three-dimensional height profile data to generate predicted height data that matches the scanning path of the second optical system of the second station.

[0063] In some embodiments, specifically, the interpolation processing specifically includes: according to the geometric relationship between the scanning path of the first station and the scanning path of the second station, through the bicubic spline interpolation algorithm, based on the surface smoothness constraint of the object to be measured, reconstructing the surface morphology of the object to be measured, and generating a continuous height distribution that matches the number of scanning lines of the second station. By establishing a wafer surface morphology smoothness model (local curvature is less than 0.05 / mm), the effectiveness of interpolation prediction in non-co-point scanning scenarios is demonstrated. Compared with traditional real-time focusing solutions, it can reduce 70% of hardware configuration costs while ensuring imaging quality.

[0064] refer to Figure 3 and Figure 4 The following will use a specific example to discuss how to convert 30 lines of height data at the first station into 20 lines of height data of the required focus path at the second station through interpolation, as follows.

[0065] At the first station, an appropriate number of sampling points can be taken for each scanned line, for example, 1000 or 2000 sampling points. The number of sampling points per line can be pre-set and adjusted based on actual needs. Generally speaking, the greater the number of sampling points, the more accurate the height data predicted during the subsequent interpolation prediction, which matches the scan path at the second station, and the better the final focusing effect.

[0066] After completing a scan at the first station, 30 lines of height data are obtained. If 1,000 sampling points are taken per line, the total amount of 3D height profile data acquired at the first station is 30 × 1,000, or 30,000. Based on the height data from these 30,000 different sampling points, the height data for other non-sampling locations can be predicted through interpolation. These non-sampling locations must include the locations covered by the scanning path at the second station, ultimately obtaining the required 20 lines of height data for the second station.

[0067] It should be noted that the number of height data included in each scanning line at the second station can be pre-designed according to the auto-focusing requirements at the second station; for example, 500 or 1000.

[0068] In addition, the above-mentioned case of predicting 20 lines of height data at the second station based on 30 lines of height data at the first station is only an example in this embodiment and does not limit the technical solution of this disclosure. In this application, there is no limit on the amount of height data at the first and second stations; for example, the first station can have 40 lines of height data and the second station can have 10 lines of height data; for another example, the first station can have 15 lines of height data and the second station can have 25 lines of height data.

[0069] See also Figure 3 and Figure 4 As shown, when scanning at the first station, the height data of the red scanning path can be obtained; when autofocusing at the second station, the height data of the green scanning path ( Figure 3 The green scan path's height data (in the green arrow area in the right figure) can be inferred by interpolating the height data along the red scan path. The green and red scan paths belong to two independent optical systems and are located at different mechanical positions. To accurately obtain height data along the green scan path, the primary task is to determine the relative position between the red and green scan paths.

[0070] Step 3: Based on the pre-calibrated coordinate system conversion matrix, the predicted height data is mapped to the second workstation coordinate system to obtain the mapped height data.

[0071] In some embodiments, specifically, the coordinate system conversion matrix is ​​constructed in the following manner:

[0072] Use a calibration plate with a reference mark to perform multi-station joint calibration, and scan at the first station and the second station to obtain the coordinate measurement values ​​of the same reference mark.

[0073] The translation and rotation angle between the first and second workstations are obtained by the least squares method, and a homogeneous transformation matrix with five degrees of freedom is constructed.

[0074] In some embodiments, more specifically, it is necessary to determine the coordinate position relationship between the scanning path at the first station and the scanning path at the second station. This difference in coordinate position can be bridged by transforming the coordinate system matrix. The transformation of the coordinate system matrix can be achieved through calibration. After calibration, the coordinate system transformation matrix can be obtained. Then, the coordinates of the second optical system scanning position at the green scanning path, calculated from the difference in the first optical system scanning position at the red scanning path, can be converted into the actual coordinates of the second optical system scanning position through matrix transformation.

[0075] The calibration process is as follows: First, place a square calibration plate and let the first optical system scan it. Whenever entering the square area, the height sensor will sense the height change, indicating that it has entered the area. Next, move in the direction of the arrow on the green scanning path, and the sensor can also capture the changes when entering the square area. In this way, the coordinates in the X direction (i.e., the scanning direction) can be aligned to calculate the difference in their coordinate values. Subsequently, move in the vertical direction (Y direction) and detect the entry trigger position in the first and second optical systems to sense their coordinates in the Y direction. This step is used for coordinate correction in the Y direction. Finally, through the joint correction of the X and Y directions, the required coordinate system conversion matrix can be obtained. Through this coordinate system conversion matrix, the data of the first optical system coordinate system can be accurately converted to the second optical system coordinate system. In this way, the height data can be smoothly applied to the second optical system coordinate system to achieve coordinate conversion and precise use of the data.

[0076] This embodiment develops a path reconstruction algorithm based on bicubic spline interpolation to convert multiple rows of height data of the scanning path of the first station into multiple rows of height data of the scanning path of the second station; combined with a homogeneous transformation matrix including 5-degree-of-freedom compensation (accuracy of ±0.8μm), the coordinate system deviation problem caused by station switching is solved.

[0077] Step 4: During the scanning process of the second optical system at the second station, the mapped height data and the mechanical system error correction are combined to drive the Z-axis actuator to achieve dynamic focus compensation. In some embodiments, dynamic focus compensation specifically includes:

[0078] A reference mark point is set on the fixture, and the height values ​​H1 and H2 of the reference mark point in the Z direction are measured at the first station and the second station respectively.

[0079] Obtain the Z-axis system error ΔZ=H2-H1, and add the Z-axis system error to all mapped height data.

[0080] Preferably, dynamic focus compensation may further include:

[0081] During the workstation switching process, the XY displacement deviation of the robot arm is collected in real time through hardware triggering.

[0082] The influence of XY displacement deviation on height mapping is calculated based on the pre-established error transfer model, and the Z-axis compensation is corrected.

[0083] In some embodiments, more specifically, mechanical errors primarily arise from deviations in the coordinate transformation process. While the first optical system is designed to scan along the red scanning path, the actual scanning process may not be performed exactly along that path. Similarly, deviations may also occur when the second optical system is designed to scan along the green scanning path. Mechanical readouts indicate axis position, but actual execution may exhibit precision deviations.

[0084] For example, it is expected that the axis will move to a position of 100mm, and after the axis moves, the system will display the position of 100mm. However, the axis may not actually be at the position of 100mm. For example, the axis may actually be at a position of 99.995mm. This deviation may have a significant impact on the accuracy of the X and Y directions. To solve this problem, some embodiments adopt the method of adding a hardware trigger to the axis encoder. By using hardware triggering, the scanning error in the X and Y directions can be effectively eliminated.

[0085] Another issue of concern is Z-axis error. When the device scans through the first optical system and then enters the second optical system, there will be an overall deviation in the Z direction. This is because the axis inevitably changes in the Z direction as it moves from the first optical system to the second.

[0086] To address this deviation, some embodiments employ a method whereby a point is fixed on the fixture, its height H1 is recorded during scanning by the first optical system, and then, when entering the second optical system for optical scanning, the second optical system's height sensor also measures this point and records its height H2. This results in a height difference DeltaH = H2 - H1. Therefore, when the device enters the second optical system for focus measurement, this height deviation value needs to be included in the compensation. By adding this deviation to all Z-direction data when executing the second optical system's scan along the green scanning path, the error in the Z direction can be controlled within an acceptable range.

[0087] This application adopts a composite correction scheme of grating scale triggering (10kHz) and joint angle monitoring to compensate in real time for the XY plane deviation (less than 5μm) and Z-axis system error (ΔZ=1.2μm) generated during the movement of the robotic arm. This mechanism stabilizes the cross-station focus accuracy at ±80nm, meeting the 80nm sensitivity detection requirements of silicon carbide wafers. Through the "interpolation prediction + real-time correction" dual-channel mechanism, ±80nm accuracy is achieved in non-real-time focusing scenarios, breaking through the static error bottleneck of traditional pre-scanning schemes. This application combines the optical focusing evaluation function with the mechanical error compensation model to achieve sub-micron cross-coordinate system data mapping, solving the problem of real-time focus failure caused by transparent wafer materials.

[0088] Figure 5 The block diagram of an electronic device suitable for implementing the multi-channel cross-station focusing method described above according to an embodiment of the present application is schematically shown. Figure 5 The electronic device shown is only an example and should not limit the functions and scope of use of the embodiments of the present application.

[0089] like Figure 5 As shown, the electronic device 1000 described in this embodiment includes: a processor 1001, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 1002 or a program loaded from a storage part 1008 into a random access memory (RAM) 1003. The processor 1001 may, for example, include a general-purpose microprocessor (such as a CPU), an instruction set processor and / or a related chipset and / or a special-purpose microprocessor (for example, an application-specific integrated circuit (ASIC)), and so on. The processor 1001 may also include on-board memory for caching purposes. The processor 1001 may include a single processing unit or multiple processing units for performing different actions of the multi-channel cross-station focusing method process according to an embodiment of the present application.

[0090] In RAM 1003, various programs and data required for the operation of electronic device 1000 are stored. Processor 1001, ROM 1002 and RAM 1003 are connected to each other via bus 1004. Processor 1001 performs various operations of the multi-channel cross-station focusing method process according to an embodiment of the present application by executing the programs in ROM 1002 and / or RAM 1003. It should be noted that the program can also be stored in one or more memories other than ROM 1002 and RAM 1003. Processor 1001 can also perform various operations of the multi-channel cross-station focusing method process according to an embodiment of the present application by executing the programs stored in the one or more memories.

[0091] According to an embodiment of the present application, electronic device 1000 may further include an input / output (I / O) interface 1005, which is also connected to bus 1004. Electronic device 1000 may further include one or more of the following components connected to I / O interface 1005: an input portion 1006 including a keyboard, mouse, etc.; an output portion 1007 including devices such as a cathode ray tube (CRT), liquid crystal display (LCD), and speakers; a storage portion 1008 including a hard disk; and a communication portion 1009 including a network interface card such as a LAN card or modem. Communication portion 1009 performs communication processing via a network such as the Internet. A drive 1010 is also connected to I / O interface 1005 as needed. Removable media 1011, such as a magnetic disk, optical disk, magneto-optical disk, semiconductor memory, etc., is installed in drive 1010 as needed, so that computer programs read from the removable media can be installed into storage portion 1008 as needed.

[0092] According to the multi-channel cross-station focusing method process of an embodiment of the present application, it can be implemented as a computer software program. For example, an embodiment of the present application includes a computer program product, which includes a computer program carried on a computer-readable storage medium, and the computer program contains a program code for executing the multi-channel cross-station focusing method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from the network through the communication part 1009, and / or installed from the removable medium 1011. When the computer program is executed by the processor 1001, the above-mentioned functions defined in the system of the embodiment of the present application are executed. According to an embodiment of the present application, the systems, devices, means, modules and / or units described above can be implemented by computer program modules.

[0093] Embodiments of the present application also provide a computer-readable storage medium, which may be included in the device / apparatus / system described in the above embodiments, or may exist independently without being incorporated into the device / apparatus / system. The computer-readable storage medium carries one or more programs, and when the one or more programs are executed, the steps of the multi-channel cross-station focusing method according to the embodiments of the present application can be implemented.

[0094] According to an embodiment of the present application, the computer-readable storage medium may be a non-volatile computer-readable storage medium, for example, it may include but is not limited to: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In an embodiment of the present application, the computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in combination with an instruction execution system, apparatus, or device. For example, according to an embodiment of the present application, the computer-readable storage medium may include one or more memories other than the ROM 1002 and / or RAM 1003 described above.

[0095] It should be noted that the functional modules in the various embodiments of the present application can be integrated into a processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software functional modules. If the integrated modules are implemented in the form of software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product.

[0096] The flowcharts and / or block diagrams in the accompanying drawings illustrate the possible architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present application. In this regard, each box in the flowchart and / or block diagram can represent a module, a program segment or a part of code, and the part of the above-mentioned module, program segment or code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. It should also be noted that each box in the block diagram or flowchart, and the combination of the boxes in the block diagram or flowchart, can be implemented by a special hardware-based system that performs the specified function or operation, or can be implemented by a combination of special hardware and computer instructions.

[0097] Those skilled in the art will appreciate that the features described in the various embodiments and / or claims of this application may be combined and / or coupled in various ways, even if such combinations and / or couplings are not explicitly described in this application. In particular, without departing from the spirit and teachings of this application, the technical features described in the various embodiments and / or claims of this application may be combined and / or coupled in various ways, and all such combinations and / or couplings fall within the scope of this application.

[0098] Although the present application has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made to the present application without departing from the spirit and scope of the present application as defined by the appended claims and their equivalents. Therefore, the scope of the present application should not be limited to the above-described embodiments, but should be determined not only by the appended claims but also by the equivalents of the appended claims.

Claims

1. A multi-channel cross-station focusing method, characterized in that: include: When the object to be measured is scanned by the first optical system at the first station, three-dimensional height profile data of the surface of the object to be measured is synchronously acquired; interpolating the three-dimensional height profile data to generate predicted height data that matches a scanning path of a second optical system of a second station; Based on a pre-calibrated coordinate system conversion matrix, the predicted height data is mapped to a second workstation coordinate system to obtain mapped height data; During the scanning process of the second optical system of the second station, the mapped height data and the mechanical system error correction are combined to drive the Z-axis actuator to achieve dynamic focus compensation.

2. The multi-channel cross-station focusing method according to claim 1, wherein: The interpolation process specifically includes: According to the geometric relationship between the scanning paths of the first and second stations, the surface topography of the object to be measured is reconstructed through the bicubic spline interpolation algorithm based on the surface smoothness constraint of the object to be measured, and a continuous height distribution matching the number of scanning lines of the second station is generated.

3. The multi-channel cross-station focusing method according to claim 1, wherein: The coordinate system conversion matrix is ​​constructed in the following manner: Use a calibration plate with a fiducial mark to perform multi-station joint calibration, scanning at the first and second stations to obtain coordinate measurement values ​​of the same fiducial mark; The translation and rotation angle between the first and second workstations are obtained by the least squares method, and a homogeneous transformation matrix with five degrees of freedom is constructed.

4. The multi-channel cross-station focusing method according to claim 1, wherein: Combining the mapped height data with the mechanical system error correction, driving the Z-axis actuator to achieve dynamic focus compensation includes: Set a reference mark on the fixture and measure the height values ​​H1 and H2 of the reference mark in the Z direction at the first and second stations respectively; Obtain the Z-axis system error ΔZ=H2-H1, and add the Z-axis system error to all mapped height data.

5. The multi-channel cross-station focusing method according to claim 1, wherein: The method for obtaining the three-dimensional height profile data includes: The optical focus evaluation function method based on bright field imaging inverts the surface height distribution through the focus evaluation curve collected during line-by-line scanning.

6. The multi-channel cross-station focusing method according to claim 5, characterized in that: The focusing evaluation function method includes: The improved Tenengrad gradient operator is used to calculate the high-frequency component intensity value of the image area within the ultraviolet spectrum: F(x,y)=Σ[G_x(x,y) 2 +G_y(x,y) 2 ]; Among them, G_x(x,y) and G_y(x,y) represent the horizontal and vertical gradient components after Sobel operator processing respectively; F(x,y) represents the intensity value of the high-frequency component.

7. The multi-channel cross-station focusing method according to claim 1, wherein: The dynamic focus compensation further includes: During the station switching process, the XY displacement deviation of the robot arm is collected in real time through hardware triggering; The influence of XY displacement deviation on height mapping is calculated based on the pre-established error transfer model, and the Z-axis compensation is corrected.

8. The multi-channel cross-station focusing method according to claim 1, wherein: The first station is a high depth of field imaging system with a depth of field ≥ 5 μm; The second station is a low depth of field imaging system with a depth of field ≤ 4 μm.

9. An electronic device, characterized in that: It includes at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program, and when the computer program is executed by the processing unit, the processing unit is enabled to perform the steps of the multi-channel cross-station focusing method according to any one of claims 1 to 8.

10. A storage medium, characterized in that: It stores a computer program that can be executed by an access authentication device. When the computer program runs on the access authentication device, the access authentication device is enabled to execute the steps of the multi-channel cross-station focusing method according to any one of claims 1 to 8.

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