Lithography machine displacement measurement system

Abstract

This invention discloses a lithography machine displacement measurement system, comprising a mask stage six-DOF displacement measurement subsystem, a grating mounting plate six-DOF displacement measurement subsystem, and a workpiece stage six-DOF displacement measurement subsystem. These subsystems are used to measure the spatial pose of the mask stage relative to the main substrate, the spatial pose of the first grating mounting plate relative to the projection lens / alignment sensor, and the spatial pose of the workpiece stage relative to the first grating mounting plate, respectively. On the one hand, this invention employs a unified electronic counting module and a unified clock reference signal within the hardware board, effectively mitigating time delays between systems and solving the problem of asynchronous relative displacement measurement between components. On the other hand, it uses a unified light source signal and detector, reducing system errors caused by factors such as light source wavelength perturbations and improving the accuracy of relative displacement measurement between components within the same displacement measurement subsystem and between components across displacement measurement subsystems.

Description

Technical Field

[0001] This invention relates to the field of grating measurement technology, and more particularly to a displacement measurement system for a lithography machine. Background Technology

[0002] In the field of modern ultra-precision machining and measurement, the precise relative spatial poses between components within precision instruments are crucial for the normal operation of the system and the realization of high-precision machining or measurement functions. For example, in the high-end equipment manufacturing industry, taking the working principle of ASML lithography machines as an example, during the lithography process, to ensure lithography accuracy, the positional accuracy of the measuring stage and exposure stage of the lithography machine needs to reach the nanometer level, and precise positioning of the six-degree-of-freedom spatial poses of the lithography mask stage and the workpiece stage of the lithography machine must be achieved.

[0003] Commonly used spatial pose measurement techniques include optical and non-optical measurement techniques. Non-optical measurement techniques generally have a measurement accuracy not exceeding the micrometer level; therefore, in the field of ultra-precision machining, non-optical measurement techniques often fail to meet the required measurement accuracy. Optical measurement techniques commonly use laser interferometers and grating rulers or encoders. Both laser interferometry and grating measurement methods can achieve nanometer-level measurement accuracy. However, in practical applications, such as in high-end lithography machines, laser interferometers are often limited by environmental factors, and their measurement accuracy does not meet the requirements. Therefore, grating measurement technology is used in the displacement measurement system of lithography machines.

[0004] In existing lithography machines, multiple displacement measurement systems exist, each operating independently. These systems utilize multiple lasers to provide light source signals and multiple electronic counting modules. Consequently, the clock reference signals between these systems are inconsistent, and the data processing systems are not synchronized. This results in the inability to synchronize the measurement of the relative spatial pose between components in each displacement measurement system. Furthermore, the inconsistent light source signals, which serve as the measurement reference for the grating ruler detector, lead to significant displacement measurement errors between systems due to variations in wavelength. This severely impacts measurement accuracy, and with the increasing precision of lithography, this measurement method no longer meets current accuracy requirements.

[0005] Furthermore, in existing technologies, the detector types used in various displacement measurement systems within a lithography machine are not entirely the same. For example, in the mask stage displacement measurement system, a hybrid measurement method using capacitive sensors and grating interferometers is employed. The accuracy of this method is far lower than that of a method using a uniform grating interferometer. In the grating mounting plate displacement measurement system, a hybrid method using heterodyne and homodyne grating interferometers is employed, and the incident laser types used in the heterodyne and homodyne grating interferometers are different. Similarly, different light sources introduce varying degrees of wavelength perturbation, leading to displacement measurement errors within the system. Therefore, the measurement accuracy of this method also fails to meet more advanced measurement requirements. Summary of the Invention

[0006] To alleviate the technical problem that the inconsistency between the laser signal source and electronic counting module in the displacement measurement system of a lithography machine leads to asynchronous displacement measurements between different systems and large displacement measurement errors between systems, making it difficult for existing technologies to meet higher measurement requirements, this invention provides a displacement measurement system for a lithography machine, comprising:

[0007] A lithography machine displacement measurement system, comprising:

[0008] The mask stage six-degree-of-freedom displacement measurement subsystem is used to obtain the six-degree-of-freedom displacement of the mask stage relative to the main substrate;

[0009] A six-DOF displacement measurement subsystem for grating mounting plate is used to obtain the six-DOF displacement of the pre-processing grating mounting plate relative to the alignment sensor and the exposure grating mounting plate relative to the projection lens.

[0010] The workpiece stage six-degree-of-freedom displacement measurement subsystem is used to obtain the six-degree-of-freedom displacement of the workpiece stage relative to the first grating mounting plate, which includes a pre-processing grating mounting plate and an exposure grating mounting plate.

[0011] Laser 101 is used to simultaneously provide input light to each displacement measurement subsystem and send a reference signal to the electronic counting module;

[0012] The fiber optic beam splitter 102 is used to split the single input light of the laser into multiple input lights for each displacement measurement subsystem.

[0013] Optical fiber 103 is used to transmit the input light and return light signals of each displacement measurement subsystem, and the optical fiber length of each displacement measurement subsystem is the same.

[0014] The electronic counting module 104 converts the reference signal into a reference clock signal for the electronic counting module, and processes the return signals of each displacement measurement subsystem based on the unified reference clock signal, thereby synchronously obtaining the six-degree-of-freedom displacement of each subsystem.

[0015] Optionally, the laser 101 is a dual-frequency laser, including a single-frequency semiconductor laser source, a laser frequency stabilization unit, an acousto-optic modulator unit, a laser beat frequency unit, and an optical fiber transmission and collimation unit. The input light of each displacement measurement subsystem includes two lasers with a stable frequency difference. The two lasers are transmitted to the detector of the displacement measurement subsystem through optical fiber 103 and an optical fiber beam splitter.

[0016] Optionally, the electronic counting module 104 includes a phase card component and a calculation card component. The phase card component includes an optical fiber input interface, a photoelectric conversion module, an analog-to-digital conversion module, a filtering module, an FPGA unit, and a bus interface. The calculation card component includes a data interface and an FPGA unit.

[0017] Optionally, the photoelectric conversion module is used to convert the reflected light signal and the reference signal into electrical signals. The reflected light signal is converted into displacement using a displacement calculation method, and the reference signal is converted into a reference clock signal for the electronic counting module via a PLL circuit.

[0018] The phase card component calculates the phase difference between the measurement signal output by the detector and the reference signal output by the laser. Based on a unified reference clock signal, the phase difference is input to the calculation card component to be converted into a displacement measurement value. The displacement measurement value is used to perform a six-degree-of-freedom calculation to synchronously obtain the six-degree-of-freedom displacement of each subsystem.

[0019] Optionally, the detector is a grating interferometer or a grating encoder. Either detector includes a reading head and a grating that cooperates with the reading head. The reading head includes an optical mirror group and an incident / return signal receiver.

[0020] The optical lens group is used to generate laser interference signals, and the incident / return signal receiver is used to provide input signals and receive output interference signals.

[0021] Optionally, the grating that cooperates with the reading head in the six-degree-of-freedom displacement measurement subsystem of the mask stage is a one-dimensional grating of planar reflection / diffraction or a two-dimensional planar grating, and is connected to both sides of the grating mounting plate of the mask stage by means of plugging, van der Waals force or gluing.

[0022] Optionally, in the six-degree-of-freedom displacement measurement subsystem of the grating mounting plate, the grating that cooperates with the reading head is a two-dimensional planar reflection / diffraction grating, located between the first grating mounting plate and the projection lens / alignment sensor, and fixedly connected to the projection lens / alignment sensor.

[0023] Optionally, the grating that cooperates with the reading head in the six-degree-of-freedom displacement measurement subsystem of the workpiece stage is a two-dimensional planar reflection / diffraction grating, and is fixed to the lower surface of the first grating mounting plate by van der Waals force or adhesive bonding.

[0024] Optionally, the fiber optic cable from the input light of each displacement measurement subsystem to the detector has the same length, and the fiber optic cable from the detector to the electronic counting module has the same length.

[0025] On the one hand, this invention adopts a unified electronic counting module and uses a unified clock reference signal within the hardware board, which can effectively alleviate the time delay problem between systems and solve the problem of not being able to synchronously measure the relative displacement between components. On the other hand, it adopts a unified light source signal and detector, which can reduce system errors caused by factors such as light source wavelength disturbances and improve the accuracy of relative displacement measurement between components within the same displacement measurement subsystem and between components across displacement measurement subsystems. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the optical fiber route and system assembly of the lithography machine displacement measurement system provided in an embodiment of the present invention;

[0027] Figure 2-1 This is a top view of the grating layout of the six-degree-of-freedom displacement measurement subsystem for the mask stage provided in an embodiment of the present invention;

[0028] Figure 2-2 This is a side view of the grating layout of the six-degree-of-freedom displacement measurement subsystem for the mask stage provided in an embodiment of the present invention;

[0029] Figure 3-1 This is a top view of the detector reading head layout of the six-degree-of-freedom displacement measurement subsystem of the mask stage provided in an embodiment of the present invention;

[0030] Figure 3-2 This is a side view of the detector reading head layout of the six-degree-of-freedom displacement measurement subsystem of the mask stage provided in an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the splicing of the preprocessing grating and the exposure grating in the six-degree-of-freedom displacement measurement subsystem of the workpiece stage provided in this embodiment of the invention;

[0032] Figure 5 This is a schematic diagram of the detector distribution in the six-degree-of-freedom displacement measurement subsystem of the workpiece stage provided in an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the workpiece stage motion process in the six-degree-of-freedom displacement measurement subsystem of the workpiece stage provided in an embodiment of the present invention;

[0034] Figure 7 A schematic diagram of the detector distribution in which the scale grating plane is at a 90-degree angle to the x-axis direction in the six-degree-of-freedom displacement measurement subsystem of the grating mounting plate provided in an embodiment of the present invention.

[0035] Figure 8This is a schematic diagram of the detector distribution in the six-degree-of-freedom displacement measurement subsystem of the grating mounting plate provided in this embodiment of the invention, where the plane of the scale grating is at a 90-degree angle to the y-axis.

[0036] Icons: 101-Laser; 102-Fiber beam splitter; 103-Fiber optic cable; 104-Electronic counting module; 200-Mask stage; 210-Mask stage first planar grating; 220-Mask stage second planar grating; 301-Detector 1; 302-Detector 2; 303-Detector 3; 400-Main substrate; 410-Alignment sensor; 420-Projection lens; 501-Detector 4; 502-Detector 5; 503-Detector 6; 504-Detector 7; 505-Detector 8; 506-Detector 9; 601-Pre-processing grating mounting plate; 602-Exposure grating mounting plate; 710-Pre-processing grating; 720-Exposure grating; 730-Extension grating; 801-Detector 10; 802-Detector 11; 803-Detector 12; 804-Detector 13; 900-Workpiece stage. Detailed Implementation

[0037] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The lithography machine displacement measurement system in this embodiment, such as Figure 1 As shown, the system includes a six-DOF displacement measurement subsystem for a mask stage, a six-DOF displacement measurement subsystem for a grating mounting plate, a six-DOF displacement measurement subsystem for a workpiece stage, a laser 101, an optical fiber beam splitter 102, an optical fiber 103, and an electronic counting module 104. The laser 101 simultaneously provides input light of a specific wavelength and power to each displacement measurement subsystem and sends a reference signal to the electronic counting module. The optical fiber beam splitter 102 splits the single-path input light from the laser into multiple paths. The optical fiber 103 transmits the input light and return light signals of each displacement measurement subsystem and connects all components of that subsystem. The electronic counting module 104 processes the return light signal containing displacement information. The lithography machine displacement measurement system comprises thirteen identical detectors, each with a two-DOF displacement measurement function.

[0039] The laser in this embodiment is based on an internal clock signal that triggers pulse output. It can emit laser light at a fixed frequency. For example, the two laser beams with a fixed frequency difference, 120MHz and 100MHz, are output to the detector's reading head; the reference signal output to the electronic counting module is 40MHz. Since all subsystems use the same laser, the light output from the laser can be simultaneously transmitted to each displacement measurement subsystem.

[0040] In this system, the optical fiber lengths of each displacement measurement subsystem are the same. Specifically, the optical fiber lengths from the input light to the detector are the same for each displacement measurement subsystem, and the optical fiber lengths from the detector to the electronic counting module are also the same.

[0041] The reference signal enters the electronic counting module and is converted into a reference clock signal by the photoelectric conversion module of the electronic counting module. The electronic counting module processes the return signals containing displacement information of each subsystem based on the unified reference clock signal, thereby simultaneously obtaining the six degrees of freedom displacement of each subsystem. The displacement calculation method refers to the displacement calculation of the system that performs displacement measurement through a laser / grating interferometer, using steps including filtering, mixing, CORDIC algorithm, and unwinding. Each subsystem uses this displacement calculation method. The lithography machine displacement measurement system provided in this embodiment uses multiple sets of detectors to measure the displacement measurement values ​​of the mask stage 200 relative to the main substrate 400, the displacement measurement values ​​of the first grating mounting plate relative to the projection lens / alignment sensor, and the displacement measurement values ​​of the workpiece stage 900 relative to the first grating mounting plate. Then, it performs six degrees of freedom displacement calculation to obtain the spatial pose of the mask stage 200 relative to the main substrate 400, the first grating mounting plate relative to the projection lens / alignment sensor, and the workpiece stage 900 relative to the first grating mounting plate. Furthermore, the relative spatial pose of the workpiece stage relative to the projection lens / alignment sensor can be obtained. It should be noted that the number of detectors required in this embodiment mentioned above is determined by the measurement system, but the method of the present invention is not limited to the number of detectors; similarly, the number of displacement measurement subsystems is not limited to a specific value, and multiple displacement measurement subsystems are applicable.

[0042] The mask stage six-degree-of-freedom displacement measurement subsystem includes a mask stage grating mounting plate and two planar gratings. The grating mounting plate is fixed on the mask stage 200 of the lithography machine. The two planar gratings are the first planar grating 210 and the second planar grating 220. The gratings are planar reflection / diffraction type one-dimensional gratings or two-dimensional planar gratings, and are connected to both sides of the grating mounting plate by interlocking, van der Waals forces, or adhesive bonding. The mask stage six-degree-of-freedom displacement measurement subsystem uses the method of Chinese Patent No. CN113758428A to obtain the six-degree-of-freedom spatial pose of the mask stage 200. In the mask stage six-degree-of-freedom displacement measurement subsystem, the laser 101 provides a light source signal to the detector through the fiber beam splitter 102 and the fiber 103. The detector transmits the signal containing displacement information to the electronic counting module 104 for information processing through the fiber 103. In this system, three detectors (detector 1 301, detector 2 302, and detector 3 303) combined with the first planar grating 210 and the second planar grating 220 of the mask stage can measure six displacement values. These six displacement values ​​can be used to construct a set of spatial pose calculation equations, which are then used by the electronic counting module 104 to calculate the six-degree-of-freedom spatial pose of the mask stage. Figures 2-1 to 3-2 As shown, this is one form of a first planar grating 210 and a mask stage second planar grating 220. The first planar grating 210 includes a first region 211 and a second region 212.

[0043] Among them, the workpiece stage six-degree-of-freedom displacement measurement subsystem Figure 4 This is a schematic diagram of the splicing of the preprocessing grating and the exposure grating in the six-degree-of-freedom displacement measurement subsystem of the workpiece stage provided in this embodiment of the invention;

[0044] Figure 5 This is a schematic diagram of the detector distribution in the six-degree-of-freedom displacement measurement subsystem of the workpiece stage provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the workpiece stage movement process in the six-DOF displacement measurement subsystem provided in this embodiment of the invention. The six-DOF displacement measurement subsystem includes a pre-processing position grating mounting plate 601, an exposure position grating mounting plate 602, and pre-processing position gratings 710 and 720 mounted thereon. Each of the pre-processing position gratings 710 and 720 includes a U-shaped grating. The subsystem also includes a workpiece stage 900 and detection mechanisms spaced apart on the surface of the workpiece stage 900. When the workpiece stage moves horizontally from the pre-processing position to the exposure position, the detection mechanism only needs to pass through a narrow slit between the exposure position grating and the pre-processing position grating to complete the measurement. Specifically, the six-DOF displacement measurement subsystem uses the method described in Chinese Patent No. CN113804112A to obtain the six-DOF displacement of the workpiece stage.

[0045] In the six-DOF displacement measurement subsystem of the workpiece stage, the laser 101 provides a light source signal to the detector through the optical fiber 103 and the optical fiber beam splitter 102. The detector transmits the signal containing displacement information to the electronic counting module 104 for information processing through the optical fiber 103. In this system, four detectors (detector 10 801, detector 11 802, detector 12 803, and detector 13 804), combined with the preprocessing position grating mounting plate 601 (corresponding to the preprocessing position grating 710), the exposure position grating mounting plate 602 (corresponding to the exposure position grating 720), the preprocessing position grating 710, the exposure position grating 720, and the extension grating 730, can measure six displacement values. These six displacement values ​​can be used to construct a set of spatial pose calculation equations, which are then solved by the electronic counting module 104 to calculate the six-DOF spatial pose of the workpiece stage 900.

[0046] The six-degree-of-freedom displacement measurement subsystem of the grating mounting plate uses two sets of detectors to measure six sets of displacement parameters of the first grating mounting plate relative to the projection lens / alignment sensor, and then performs six-degree-of-freedom displacement calculation to obtain the spatial pose of the first grating mounting plate relative to the projection lens 410 / alignment sensor 420.

[0047] This six-DOF displacement measurement subsystem for the grating mounting plate includes a preprocessing position measurement subsystem and an exposure position measurement subsystem. For example... Figure 7 , Figure 8 As shown, the preprocessing position measurement subsystem includes a preprocessing position grating mounting plate 601, and the exposure position measurement subsystem includes an exposure position grating mounting plate 602. The preprocessing position grating mounting plate 601 and the exposure position grating mounting plate 602 are collectively referred to as the first grating mounting plate.

[0048] The preprocessing position measurement subsystem and the exposure position measurement subsystem are respectively installed on the exposure position grating mounting plate and the preprocessing position grating mounting plate. Each measurement subsystem includes three detectors: detector 4 (501), detector 5 (502), detector 6 (503), detector 7 (504), detector 8 (505), and detector 9 (506). Each detector has two degrees of freedom for measurement: a planar displacement parallel to the upper surface of the grating mounting plate and a displacement perpendicular to the upper surface of the grating mounting plate (though the displacement can be non-perpendicular).

[0049] After extracting six sets of displacement information from the measurement signal from the detector, a six-degree-of-freedom (DOF) equation is constructed, and the six-DOF displacement is calculated to obtain the spatial pose of the first grating mounting plate relative to the projection lens / alignment sensor. Specifically, the six-DOF displacement measurement subsystem for the grating mounting plate uses the method described in Chinese Patent No. 2022105022764 to obtain the six-DOF displacement of the grating mounting plate.

[0050] like Figure 1As shown, laser 101 outputs two laser beams with a stable frequency difference. These two laser beams are split into 13 equal beams by fiber beam splitter 102, serving as reference and measurement beams respectively. These beams are transmitted via fiber optic cable 103 to the reading heads of detectors in the three displacement measurement subsystems. The measurement beam, after passing through the measurement path, is incident on the grating and forms diffracted light. The diffracted light and the reference beam are combined to generate a measurement signal. Due to the relative displacement between the grating and the reading head, the grating Doppler effect occurs, causing corresponding changes in the frequency and phase of the measurement signal. The light in the reference path does not pass through the grating, so its phase and frequency remain unchanged. The measurement signal is transmitted via fiber optic cable to the phase card component. By comparing it with the reference signal, the phase difference between the two can be calculated. The displacement measurement value can be obtained using the relationship between phase and displacement. After extracting six or eight sets of displacement information and performing six-degree-of-freedom displacement calculations, the spatial pose of the mask stage relative to the main substrate, the spatial pose of the first grating mounting plate relative to the projection lens / alignment sensor, and the spatial pose of the workpiece stage relative to the first grating mounting plate can be obtained. Furthermore, the spatial pose of the workpiece stage relative to the projection lens / alignment sensor can be obtained.

[0051] Based on the above measurement principles, on the one hand, the laser 101 serves as the sole light source for the three displacement measurement subsystems. Maintaining consistent wavelength and frequency as measurement reference parameters effectively reduces the impact of the environment on measurement accuracy. The optical transmission time includes the time delay from the laser sending the optical signal to the detector, and from the detector to the electronic counting module. This time delay is determined by the fiber length; therefore, maintaining consistent fiber length across all subsystems eliminates this delay. On the other hand, the laser 101 also provides a reference clock signal for the electronic counting module 104. The three displacement measurement subsystems use a unified reference clock as a time reference, providing a prerequisite for synchronous measurement across multiple displacement measurement subsystems. Furthermore, using a unified type of detector not only ensures consistent signal response time but also maintains consistent information processing time delay in the electronic counting module 104 due to consistent detector signal processing algorithms, ultimately guaranteeing synchronous measurement functionality for the displacement measurement system. The lithography machine displacement measurement system proposed in this invention is not limited to the embodiments described herein; it is applicable to multiple measurement systems employing a unified grating interferometer detector, laser interferometer detector, or other detectors based on similar principles.

[0052] In summary, the lithography machine displacement measurement system provided by this invention, in the embodiments provided by this invention, includes a set of detectors arranged between the mask stage and the main substrate, two sets of detectors arranged between the first grating mounting plate and the projection lens / alignment sensor, and a set of detectors arranged between the workpiece stage and the first grating mounting plate. The laser transmits incident light with frequency difference to each detector. The incident light passes through the lens group of the reading head to generate a return signal containing displacement information, thereby obtaining the displacement measurement value. Each detector can measure the displacement measurement value in two directions at the corresponding measurement point. Each set of detectors can obtain six or eight sets of displacement measurement values. These six or eight sets of displacement values ​​can be used to form a system of equations to perform six-degree-of-freedom displacement calculation, thereby obtaining the spatial pose of the mask stage relative to the main substrate, the spatial pose of the first grating mounting plate relative to the projection lens / alignment sensor, and the spatial pose of the workpiece stage relative to the first grating mounting plate. In this invention, the three displacement measurement subsystems adopt a unified signal light source and detector, which not only realizes the synchronous measurement of the relative spatial pose between the internal components of the lithography machine (mask stage, main substrate, projection lens / alignment sensor, first grating mounting plate, workpiece stage), but also improves the measurement accuracy of the spatial pose of the components, especially the relative spatial pose accuracy between components across subsystems.

[0053] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications are all within the protection scope of the claims of the present invention.

Claims

1. A displacement measurement system for a lithography machine, characterized in that, include: The mask stage six-degree-of-freedom displacement measurement subsystem is used to obtain the six-degree-of-freedom displacement of the mask stage relative to the main substrate; A six-DOF displacement measurement subsystem for grating mounting plate is used to obtain the six-DOF displacement of the pre-processing grating mounting plate relative to the alignment sensor and the exposure grating mounting plate relative to the projection lens. The workpiece stage six-degree-of-freedom displacement measurement subsystem is used to obtain the six-degree-of-freedom displacement of the workpiece stage relative to the first grating mounting plate, which includes a pre-processing grating mounting plate and an exposure grating mounting plate. A laser (101) is used to simultaneously provide input light to each displacement measurement subsystem and send a reference signal to the electronic counting module; Fiber optic beam splitter (102) is used to split the single input light of the laser into multiple input lights for each displacement measurement subsystem; Optical fiber (103) is used to transmit the input light and return light signals of each displacement measurement subsystem, and the optical fiber length of each displacement measurement subsystem is the same. The electronic counting module (104) converts the reference signal into a reference clock signal for the electronic counting module, and processes the return signals of each displacement measurement subsystem based on the unified reference clock signal, thereby synchronously obtaining the six-degree-of-freedom displacement of each subsystem.

2. The lithography machine displacement measurement system according to claim 1, characterized in that, The laser (101) is a dual-frequency laser, including a single-frequency semiconductor laser source, a laser frequency stabilization unit, an acousto-optic modulator unit, a laser beat frequency unit, and an optical fiber transmission and collimation unit. The input light of each displacement measurement subsystem includes two lasers with a stable frequency difference. The two lasers are transmitted to the detector of the displacement measurement subsystem through an optical fiber (103) and an optical fiber beam splitter.

3. The lithography machine displacement measurement system according to claim 2, characterized in that, The electronic counting module (104) includes a phase card component and a calculation card component. The phase card component includes an optical fiber input interface, a photoelectric conversion module, an analog-to-digital conversion module, a filtering module, an FPGA unit, and a bus interface. The calculation card component includes a data interface and an FPGA unit.

4. The lithography machine displacement measurement system according to claim 3, characterized in that, The photoelectric conversion module is used to convert the reflected light signal and the reference signal into electrical signals. The reflected light signal is converted into displacement using a displacement calculation method, and the reference signal is converted into a reference clock signal for the electronic counting module via a PLL circuit. The phase card component calculates the phase difference between the measurement signal output by the detector and the reference signal output by the laser. Based on a unified reference clock signal, the phase difference is input to the calculation card component to be converted into a displacement measurement value. The displacement measurement value is used to perform a six-degree-of-freedom calculation to synchronously obtain the six-degree-of-freedom displacement of each subsystem.

5. The lithography machine displacement measurement system according to claim 2, characterized in that, The detector is a grating interferometer or a grating encoder. Each detector includes a reading head and a grating that cooperates with the reading head. The reading head includes an optical mirror group and an incident / return signal receiver. The optical lens group is used to generate laser interference signals, and the incident / return signal receiver is used to provide input signals and receive output interference signals.

6. The lithography machine displacement measurement system according to claim 1, characterized in that, The grating that works with the reading head in the six-degree-of-freedom displacement measurement subsystem of the mask stage is a one-dimensional grating of planar reflection / diffraction type or a two-dimensional planar grating, and is connected to both sides of the grating mounting plate of the mask stage by means of plugging, van der Waals force or gluing.

7. The lithography machine displacement measurement system according to claim 1, characterized in that, The grating in the six-degree-of-freedom displacement measurement subsystem of the grating mounting plate is a two-dimensional planar reflection / diffraction grating that works with the reading head. It is located between the first grating mounting plate (601 / 602) and the projection lens / alignment sensor (410 / 420), and is fixedly connected to the projection lens / alignment sensor.

8. The lithography machine displacement measurement system according to claim 1, characterized in that, The grating that works with the reading head in the six-degree-of-freedom displacement measurement subsystem of the workpiece stage is a two-dimensional planar reflection / diffraction grating, and is fixed to the lower surface of the first grating mounting plate (601 / 602) by van der Waals force or adhesive bonding.

9. The lithography machine displacement measurement system according to claim 1, characterized in that, The fiber optic cables from the input light to the detector are of the same length in each displacement measurement subsystem, and the fiber optic cables from the detector to the electronic counting module are of the same length.

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