A metrology machine

Abstract

The application discloses a kind of metrology machine, belong to integrated circuit technical field, the metrology machine includes: metrology optical system, magnetic levitation wafer workstation and at least three gratings;Metrology optical system and grating are located in the upper of magnetic levitation wafer workstation;The position of metrology optical system is fixed;Grating is arranged along the circumferential direction of metrology optical system;Magnetic levitation wafer workstation includes magnetic levitation workstation, wafer chuck and at least three position sensor readheads;Wafer chuck and position sensor readhead are arranged on the surface of magnetic levitation workstation close to metrology optical system;Position sensor readhead is arranged along the circumferential direction of wafer chuck;When measuring wafer, each grating and the light signal interaction of corresponding one position sensor readhead with grating is carried out to measure the position information of magnetic levitation wafer workstation.The application can accurately control magnetic levitation wafer workstation to realize 6 degrees of freedom motion, to reduce transmission error, improve motion accuracy.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and in particular to a measurement machine. Background Technology

[0002] Currently, overlay measurement systems consist of two main components: a measurement optical system and a wafer stage. For example... Figure 1 As shown, the measuring optical system 01 moves along the Y direction at a speed of 1 m / s and an acceleration of 10 m / s². 2 The wafer stage 02 moves along the X direction at a speed of 2 m / s and an acceleration of 30 m / s². 2 When the measurement optical system 01 and the wafer stage 02 are aligned, the overlay marks on the entire wafer can be measured. Traditional overlay measurement systems have an XY direction MA (Moving Average) of <0.6μm and an XY direction MSD (Moving Standard Deviation) of <1.3μm. Currently, overlay machines use series linear motors and direct-drive motors to achieve the planar movement of the measurement optical system 01 and the wafer stage 02. However, this structure is complex, and the series configuration is prone to signal errors, making it difficult to improve accuracy. Furthermore, the movement of the measurement optical system 01 impacts the precision optical system, causing measurement deviations to increase over time, requiring periodic precision adjustments. Therefore, reducing transmission errors, improving motion accuracy, and lowering measurement deviations are technical problems that those skilled in the art need to solve. Summary of the Invention

[0003] The purpose of this application is to provide a measuring instrument that reduces transmission errors, improves motion accuracy, and reduces measurement deviations.

[0004] To achieve the above objectives, this application provides a measurement apparatus, including: a measurement optical system, a magnetically levitated wafer stage, and at least three gratings;

[0005] The measurement optical system and the grating are located above the magnetically levitated wafer stage; the position of the measurement optical system is fixed; the grating is arranged along the circumferential direction of the measurement optical system.

[0006] The magnetic levitation wafer stage includes a magnetic levitation stage, a wafer chuck, and at least three position sensor read heads; the wafer chuck and the position sensor read heads are disposed on the surface of the magnetic levitation stage near the measurement optical system; the position sensor read heads are disposed along the circumferential direction of the wafer chuck.

[0007] During wafer measurement, each grating and a corresponding position sensor read head interact with optical signals to measure the position information of the magnetically levitated wafer stage.

[0008] Optionally, the measurement equipment includes: four gratings and four position sensor readouts; each grating is centrally symmetrical about the measurement optical system; each position sensor readout is centrally symmetrical about the wafer chuck.

[0009] Optionally, the measurement equipment further includes: a wafer junction grating; the wafer junction grating is disposed on one side of the two gratings near the magnetic levitation wafer stage;

[0010] During the wafer handover, the two gratings near the magnetic levitation wafer stage interact with the two position sensor read heads near the gratings via optical signals. The wafer handover position grating interacts with one of the remaining two position sensor read heads via optical signals to measure the position information of the magnetic levitation wafer stage.

[0011] Optionally, the magnetic levitation worktable includes a worktable motor, a permanent magnet, and a base; the worktable motor is equipped with an electromagnet; the base is located below the worktable motor; the permanent magnet is disposed on the surface of the base near the worktable motor; the size of the permanent magnet is greater than or equal to the size of the motion area of ​​the worktable motor.

[0012] Optionally, the permanent magnet includes a plurality of S-pole permanent magnets and a plurality of N-pole permanent magnets; the S-pole permanent magnets and the N-pole permanent magnets are arranged alternately.

[0013] Optionally, a zero-position mark is provided on the surface of the grating near the magnetically levitated wafer stage.

[0014] Optionally, calibration marks are provided on the surface of the magnetically levitated wafer stage near the measurement optical system.

[0015] Optionally, the calibration marks include any one or more of alignment marks, micro-diffraction-based overlay marks, micro-diffraction-based focusing marks, and critical dimension marks.

[0016] Optionally, the calibration mark is disposed between the position sensor read head and the wafer chuck.

[0017] Optionally, the measurement optical system is embedded in the main substrate; the main substrate is fixed on the overall frame; the grating is arranged on the surface of the main substrate near the magnetic levitation wafer stage along the circumferential direction of the measurement optical system.

[0018] Obviously, this application replaces the traditional series linear motor and direct drive motor with a magnetic levitation wafer stage while keeping the measurement optical system stationary. It uses gratings to control the position sensor read heads on the magnetic levitation wafer stage. Based on the principle of grating diffraction, it can measure the precise position information of the magnetic levitation wafer stage in six degrees of freedom, thereby accurately controlling the magnetic levitation wafer stage to achieve six degrees of freedom of movement, thus reducing transmission errors and improving motion accuracy. At the same time, it can avoid measurement deviation caused by the measurement optical system being in motion, thereby reducing measurement deviation. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 A schematic diagram showing the movement directions of the measurement optical system and the wafer stage in a traditional overlay measurement system;

[0021] Figure 2 A structural diagram of a measuring machine provided in an embodiment of this application;

[0022] Figure 3 A schematic diagram showing the layout of the electromagnets in the workbench motor provided in this embodiment of the application;

[0023] Figure 4 This is a schematic diagram of the layout of the permanent magnet provided in an embodiment of this application;

[0024] Figure 5 This is a schematic diagram of the layout of calibration marks provided in an embodiment of this application;

[0025] Figure 6 This is a schematic diagram showing the positional relationship between the magnetically levitated wafer stage and the grating provided in an embodiment of this application.

[0026] Figure 7 A bottom view of the measurement optical system and grating provided in an embodiment of this application;

[0027] Figure 8 This is a schematic diagram illustrating the optical signal interaction between the position sensor reader and the grating when moving along the X or Y direction, as provided in an embodiment of this application.

[0028] Figure 9 This is a schematic diagram illustrating the optical signal interaction between the position sensor read head and the grating when moving along the Z direction, as provided in an embodiment of this application.

[0029] The annotations in the attached figures are explained as follows:

[0030] 01- Measurement optical system in traditional overlay measurement system; 02- Wafer stage in traditional overlay measurement system;

[0031] 1-Measuring optical system;

[0032] 211-Stage motor; 2111-Electromagnet; 212-Permanent magnet; 213-Base; 22-Wafer chuck; 23-Position sensor read head; 231-First position sensor read head; 232-Second position sensor read head; 233-Third position sensor read head; 234-Fourth position sensor read head; 241-Alignment mark; 242-Micro-diffraction-based overlay mark; 243-Micro-diffraction-based focusing mark; 244-Critical dimension mark;

[0033] 3-Grating; 31-First grating; 32-Second grating; 33-Third grating; 34-Fourth grating;

[0034] 4-Wafer Interchange Grating;

[0035] 5-Main baseboard; 6-Complete frame. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] Please refer to Figure 2 , Figure 2 This is a structural diagram of a measurement apparatus provided in an embodiment of this application. The measurement apparatus may include: a measurement optical system 1, a magnetically levitated wafer stage, and at least three optical gratings 3;

[0038] The measurement optical system 1 and the grating 3 are located above the magnetically levitated wafer stage; the position of the measurement optical system 1 is fixed; the grating 3 is set along the circumferential direction of the measurement optical system 1.

[0039] The magnetic levitation wafer stage includes a magnetic levitation stage, a wafer chuck 22, and at least three position sensor read heads 23; the wafer chuck 22 and the position sensor read heads 23 are disposed on the surface of the magnetic levitation stage near the measurement optical system 1; the position sensor read heads 23 are disposed along the circumferential direction of the wafer chuck 22.

[0040] When measuring the wafer, each grating 3 and a corresponding position sensor read head 23 interact with optical signals to measure the position information of the magnetically levitated wafer stage.

[0041] It should be noted that in this embodiment, the grating 3 and the position sensor read head 23 correspond one-to-one, and the grating 3 only interacts with the corresponding position sensor read head 23 via optical signals. The optical signal interaction process is as follows: within the region corresponding to the grating 3, the position sensor read head 23 emits reference light and measurement light towards the corresponding grating 3. After diffraction by the grating 3, the reference light and measurement light generate positive and negative first-order light, which is reflected back to the position sensor read head 23 by the grating 3. The generated positive and negative first-order light interferes in the position sensor read head 23 to form measurement interference light and reference interference light. The measurement interference light and reference interference light are input into the photoelectric conversion unit to be converted into measurement interference electrical signals and reference interference electrical signals, and then input to the electronic signal processing unit to resolve the position information of the magnetically levitated wafer stage.

[0042] This embodiment does not limit the specific number of gratings 3 and position sensor read heads 23, as long as it ensures that the position information of the six degrees of freedom (X, Y, Z, Rx, Ry, Rz) of the magnetic levitation wafer stage can be measured. For example, to ensure more accurate position information, the measurement equipment in this embodiment may include: four gratings 3 and four position sensor read heads 23; each grating 3 is symmetrical about the center of the measurement optical system 1; each position sensor read head 23 is symmetrical about the center of the wafer chuck 22. Furthermore, during wafer handover, i.e. when the magnetic levitation wafer stage moves along the... Figure 7 To obtain precise position information of the magnetically levitated wafer stage during wafer handover and thus accurately control its movement, the measurement equipment in this embodiment may further include a wafer handover position grating 4. The wafer handover position grating 4 is positioned on one side of the two gratings 3 near the magnetically levitated wafer stage. During wafer handover, the two gratings 3 near the magnetically levitated wafer stage interact with two position sensor readheads 23 near the gratings 3 via optical signals, and the wafer handover position grating 4 interacts with one of the remaining two position sensor readheads 23 via optical signals to measure the position information of the magnetically levitated wafer stage. It should be noted that which of the remaining two position sensor readheads 23 is specifically controlled by the wafer handover position grating 4 can be determined based on its specific position.

[0043] This embodiment does not limit the specific structure of the magnetic levitation stage, as long as the magnetic levitation wafer stage can achieve magnetic levitation motion. For example, the magnetic levitation stage may include a stage motor 211, a permanent magnet 212, and a base 213; the stage motor 211 is equipped with an electromagnet 2111; the base 213 is located below the stage motor 211; the permanent magnet 212 is disposed on the surface of the base 213 near the stage motor 211; the size of the permanent magnet 212 is greater than or equal to the size of the movement area of ​​the stage motor 211. It should be noted that when the electromagnet 2111 in the stage motor 211 is energized, a Lorentz force is generated between it and the permanent magnet 212 on the base 213, and the magnetic levitation wafer stage is driven to move based on this Lorentz force. This embodiment does not limit the specific arrangement of the electromagnets 2111 in the workbench motor 211, as long as it ensures that the electromagnets 2111 in the workbench motor 211 can have magnetism after being energized. For example, the electromagnets 2111 can be arranged in a meandering manner, such as... Figure 3 As shown. This embodiment does not limit the specific structure of the permanent magnet 212, as long as the permanent magnet 212 can maintain its magnetism for a long time. For example, to facilitate the control of the movement direction of the magnetic levitation wafer stage, the permanent magnet 212 may include multiple S-pole permanent magnets 212 and multiple N-pole permanent magnets 212; the S-pole permanent magnets 212 and the N-pole permanent magnets 212 are arranged alternately, such as... Figure 4 As shown.

[0044] This embodiment does not limit the specific fixing method of the measurement optical system 1, as long as the position of the measurement optical system 1 can be fixed. For example, the measurement optical system 1 can be embedded in the main substrate 5; the main substrate 5 is fixed on the frame 6. Furthermore, in this embodiment, the grating 3 can be arranged on the surface of the main substrate 5 near the magnetic levitation wafer stage along the circumferential direction of the measurement optical system 1.

[0045] Furthermore, in this embodiment, a zero-position mark can be provided on the surface of the grating 3 near the magnetic levitation wafer stage. It should be noted that grating interferometry is a relative measurement method, requiring knowledge of the absolute position; therefore, a zero position must be defined. In this embodiment, a zero-position mark is etched on the grating 3, and this mark serves as the absolute zero position. Based on this absolute zero position, the position in the absolute coordinate system can be measured.

[0046] Furthermore, in this embodiment, calibration marks can be provided on the surface of the magnetic levitation wafer stage near the measurement optical system 1. It should be noted that the measurement optical system 1 may have drift problems such as control motor movement deviation and light wavelength offset, which can reduce the accuracy of overlay measurements. After adding calibration marks to the magnetic levitation wafer stage, the measurement optical system 1 can identify the calibration marks and obtain the corresponding performance parameters (e.g., overlay values, optimal focal position, critical dimension values, etc.). The obtained performance parameters are compared with standard performance parameters. When it is detected that the obtained performance parameters are not within the standard performance parameter range, the measurement optical system 1 is corrected until the obtained performance parameters are within the standard performance parameter range, thereby achieving monitoring and calibration of the performance of the measurement optical system 1, and ensuring the accuracy of overlay measurements. This embodiment does not limit the specific number or type of calibration marks. For example, calibration marks may include any one or more of the following: alignment marks 241, micro-diffraction-based overlay marks 242, micro-diffraction-based focusing marks 243, and critical dimension marks 244. It should be noted that the alignment mark 241 allows for confirmation of the tilt of the magnetically levitated wafer stage; the micro-diffraction based overlay (uDBO) mark 242, the micro-diffraction based focus (uDBF) mark 243, and the critical dimension (CD) mark 244, among other marks, allow for confirmation and calibration of the machine's performance. Before each measurement of the product, the measurement optical system 1 identifies the calibration marks. Different performance parameters are obtained by identifying different calibration marks. By determining whether these performance parameters are within the standard performance parameter range, it is determined whether the measurement optical system 1 needs to be calibrated. This embodiment does not limit the specific location of the calibration marks, as long as the measurement optical system 1 can recognize them. For example, the calibration marks can be placed between the position sensor read head 23 and the wafer chuck 22.

[0047] Based on the above embodiments, this application replaces the traditional series linear motor and direct drive motor with a magnetic levitation wafer stage while keeping the measurement optical system 1 stationary. A grating 3 is used to control the position sensor read heads 23 on the magnetic levitation wafer stage. Based on the diffraction principle of the grating 3, the precise position information of the six degrees of freedom of the magnetic levitation wafer stage can be measured, thereby accurately controlling the magnetic levitation wafer stage to achieve six degrees of freedom of movement, thus reducing transmission errors and improving motion accuracy. At the same time, it can avoid measurement deviation caused by the measurement optical system 1 being in motion, thereby reducing measurement deviation.

[0048] Another measurement apparatus provided in this application embodiment may include: a measurement optical system 1, a magnetically levitated wafer stage, four gratings 3 and a wafer junction grating 4;

[0049] The measurement optical system 1 and the grating 3 are located above the magnetic levitation wafer stage; the position of the measurement optical system 1 is fixed; the grating 3 is set along the circumferential direction of the measurement optical system 1; each grating 3 is symmetrical about the center of the measurement optical system 1; the wafer junction grating 4 is set on one side of the two gratings 3 near the magnetic levitation wafer stage.

[0050] The magnetic levitation wafer stage includes a magnetic levitation stage, a wafer chuck 22, and four position sensor read heads 23. Calibration marks are provided on the surface of the magnetic levitation wafer stage near the measurement optical system 1. The wafer chuck 22 and the position sensor read heads 23 are disposed on the surface of the magnetic levitation stage near the measurement optical system 1. The position sensor read heads 23 are arranged along the circumferential direction of the wafer chuck 22. Each position sensor read head 23 is symmetrical about the center of the wafer chuck 22.

[0051] When measuring the wafer, each grating 3 and a position sensor read head 23 corresponding to the grating 3 interact with optical signals to measure the position information of the magnetic levitation wafer stage;

[0052] During wafer handover, the two gratings 3 near the magnetic levitation wafer stage interact with the two position sensor read heads 23 near the gratings 3, respectively, and the wafer handover position grating 4 interacts with one of the remaining two position sensor read heads 23 to measure the position information of the magnetic levitation wafer stage.

[0053] Based on the above embodiments, this application replaces the traditional series linear motor and direct drive motor with a magnetic levitation wafer stage while keeping the measurement optical system 1 stationary. A grating 3 controls the position sensor read heads 23 on the magnetic levitation wafer stage. During wafer measurement and wafer handover, the precise position information of the magnetic levitation wafer stage (6 degrees of freedom) can be measured based on the diffraction principle of the grating 3. This allows for precise control of the magnetic levitation wafer stage to achieve 6 degrees of freedom movement, thereby reducing transmission errors and improving motion accuracy. Simultaneously, it avoids measurement deviations caused by the measurement optical system 1 being in motion, thus reducing measurement deviations. Furthermore, by adding calibration marks to the magnetic levitation wafer stage, online monitoring and calibration of the performance of the measurement optical system 1 can be achieved, ensuring the accuracy of overlay measurements.

[0054] The working principle of the above-mentioned measuring machine is explained below with specific examples.

[0055] Please refer to Figure 2 , Figure 2This is a structural diagram of a measurement machine provided in an embodiment of this application. The measurement machine includes: a measurement optical system 1, a magnetically levitated wafer stage, four gratings 3 (including a first grating 31, a second grating 32, a third grating 33, and a fourth grating 34), a wafer junction grating 4, a main substrate 5, and a frame 6.

[0056] The measurement optical system 1 and the grating 3 are located above the magnetic levitation wafer stage; the measurement optical system 1 is embedded in the main substrate 5; the main substrate 5 is fixed on the frame 6; the grating 3 is arranged on the lower surface of the main substrate 5 along the circumferential direction of the measurement optical system 1; each grating 3 is symmetrical about the center of the measurement optical system 1; the wafer junction grating 4 is arranged on one side of the fourth grating 34.

[0057] The magnetic levitation wafer stage includes a magnetic levitation stage, a wafer chuck 22, and four position sensor read heads 23 (including a first position sensor read head 231, a second position sensor read head 232, a third position sensor read head 233, and a fourth position sensor read head 234). The wafer chuck 22 and the position sensor read heads 23 are disposed on the upper surface of the magnetic levitation wafer stage. The upper surface of the magnetic levitation wafer stage is provided with calibration marks (including alignment marks 241, micro-diffraction-based overlay marks 242, micro-diffraction-based focusing marks 243, and critical dimension marks 244). The calibration marks are disposed between the position sensor read heads 23 and the wafer chuck 22, such as... Figure 5 As shown; the position sensor read head 23 is arranged along the circumferential direction of the wafer chuck 22; each position sensor read head 23 is symmetrical about the center of the wafer chuck 22; the magnetic levitation stage includes a stage motor 211, a permanent magnet 212 and a base 213; an electromagnet 2111 is provided in the stage motor 211; the base 213 is located below the stage motor 211; the permanent magnet 212 is arranged on the upper surface of the base; the permanent magnet 212 covers the entire motion area of ​​the magnetic levitation wafer stage.

[0058] Please refer to Figure 6 , Figure 6 This diagram illustrates the positional relationship between the magnetically levitated wafer stage and the grating provided in this embodiment. During wafer measurement, the first position sensor reader 231 on the magnetically levitated wafer stage interacts with the first grating 31 within its region; the second position sensor reader 232 interacts with the second grating 32 within its region; the third position sensor reader 233 interacts with the third grating 33 within its region; and the fourth position sensor reader 234 interacts with the fourth grating 34 within its region. This is a four-reader control mode to measure the position information of the magnetically levitated wafer stage. In this embodiment, the speed of the magnetically levitated wafer stage can reach 1.5 m / s, and the acceleration can reach 35 m / s².2 The MA in the XY direction is less than 2.5 nm, and the MSD in the XY direction is less than 5.0 nm. Compared with traditional overlay measurement systems, the control accuracy is improved by 300 times at similar speeds.

[0059] Please refer to Figure 7 , Figure 7 This is a bottom view of the measurement optical system and grating provided in an embodiment of this application. During wafer handover, the second position sensor read head 232 on the magnetically levitated wafer stage interacts with the first grating 31 in the region of the first grating 31, the third position sensor read head 233 interacts with the fourth grating 34 in the region of the fourth grating 34, and the fourth position sensor read head 234 interacts with the wafer handover position grating 4 in the region of the wafer handover position grating 4, in order to measure the position information of the magnetically levitated wafer stage.

[0060] Please refer to Figure 8 and Figure 9 , Figure 8 This is a schematic diagram illustrating the optical signal interaction between the position sensor reader and the grating when moving along the X or Y direction, as provided in an embodiment of this application. Figure 9 This is a schematic diagram illustrating the optical signal interaction between the position sensor read head and the grating during movement along the Z-direction, as provided in an embodiment of this application. Each position sensor read head 23 contains two measurement beams (including a first measurement beam A and a second measurement beam B) and a reference beam C. Within the region corresponding to the grating 3, the position sensor read head 23 emits the reference beam and the measurement beam towards the corresponding grating 3. After diffraction by the grating 3, the reference beam and the measurement beam generate positive and negative first-order beams, which are then reflected back to the position sensor read head 23 by the grating 3. The position information of the magnetically levitated wafer stage can be determined based on the generated positive and negative first-order beams. Figure 8 and Figure 9 As shown, if the light moves along the horizontal direction (X, Y direction), the positive and negative first-order light information are the same; if it moves along the vertical direction (Z direction), the positive and negative first-order light information are opposite.

[0061] This document uses specific examples to illustrate the principles and implementation methods of this application. The various embodiments are progressive, with each embodiment focusing on its differences from others. Similar or identical parts between embodiments can be referred to interchangeably. The descriptions of the embodiments above are merely illustrative of the method and core ideas of this application. For those skilled in the art, various improvements and modifications can be made to this application without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this application.

[0062] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

Claims

1. A measuring machine, characterized in that, include: Measurement optical system, magnetic levitation wafer stage and four gratings; The measurement optical system and the grating are located above the magnetically levitated wafer stage; the position of the measurement optical system is fixed; the grating is arranged along the circumferential direction of the measurement optical system; each grating is symmetrical about the center of the measurement optical system. The magnetic levitation wafer stage includes a magnetic levitation stage, a wafer chuck, and four position sensor read heads; the wafer chuck and the position sensor read heads are disposed on the surface of the magnetic levitation stage near the measurement optical system; the position sensor read heads are disposed along the circumferential direction of the wafer chuck; each of the position sensor read heads is symmetrical about the center of the wafer chuck. During wafer measurement, each grating and a corresponding position sensor read head interact with optical signals to measure the position information of the magnetically levitated wafer stage. It also includes: a wafer junction grating; the wafer junction grating is disposed on one side of the two gratings near the magnetic levitation wafer stage; During the wafer handover, the two gratings near the magnetic levitation wafer stage interact with the two position sensor read heads near the gratings via optical signals. The wafer handover position grating interacts with one of the remaining two position sensor read heads via optical signals to measure the position information of the magnetic levitation wafer stage.

2. The measuring machine according to claim 1, characterized in that, The magnetic levitation worktable includes a worktable motor, a permanent magnet, and a base; the worktable motor is equipped with an electromagnet; the base is located below the worktable motor; the permanent magnet is disposed on the surface of the base near the worktable motor; the size of the permanent magnet is greater than or equal to the size of the motion area of ​​the worktable motor.

3. The measuring machine according to claim 2, characterized in that, The permanent magnet includes multiple S-pole permanent magnets and multiple N-pole permanent magnets; the S-pole permanent magnets and the N-pole permanent magnets are arranged alternately.

4. The measuring machine according to claim 1, characterized in that, The grating has a zero-position mark on its surface near the magnetic levitation wafer stage.

5. The measuring machine according to claim 1, characterized in that, The magnetic levitation wafer stage has calibration marks on its surface near the measurement optical system.

6. The measuring machine according to claim 5, characterized in that, The calibration marks include any one or more of the following: alignment marks, micro-diffraction-based overlay marks, micro-diffraction-based focusing marks, and critical dimension marks.

7. The measuring machine according to claim 5, characterized in that, The calibration mark is positioned between the position sensor read head and the wafer chuck.

8. The measuring machine according to claim 1, characterized in that, The measurement optical system is embedded in the main substrate; the main substrate is fixed on the overall frame; the grating is arranged on the surface of the main substrate near the magnetic levitation wafer stage along the circumferential direction of the measurement optical system.

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