Multi-degree-of-freedom displacement measurement system based on two-dimensional grating

Abstract

The present invention proposes a multi-degree-of-freedom displacement measurement system based on a two-dimensional grating, comprising a reading module and a two-dimensional grating respectively arranged on a moving part and an active part, wherein the reading module comprises two groups of first displacement sensors arranged along a first direction, two groups of second displacement sensors arranged along a second direction, and a distance sensor located at the physical center of the first sensor and the second sensor. The present invention solves the problem that a multi-channel sensing reading system needs to be independently installed in a traditional multi-degree-of-freedom measurement system, and can achieve precise measurement of displacement, rotation amount, and displacement in four degrees of freedom directions perpendicular to the two-dimensional plane. By arranging a distance sensor, the optimal reading spacing position between the reading module and the two-dimensional grating can be directly adjusted and determined, which simplifies the process of installation and debugging of the traditional two-dimensional grating and reduces the technical difficulty of its debugging.

Description

Technical Field

[0001] The present invention relates to the field of photolithography equipment, and in particular to a multi-degree-of-freedom displacement measurement system based on a two-dimensional grating. Background Art

[0002] In the precision machinery, aerospace, automobile manufacturing, optical processing, semiconductor manufacturing, 3C and other industries, the requirements of precision manufacturing technology, the core technology of which is the demand for the ability to accurately measure the displacement of moving parts of high-end equipment. In modern measurement systems, whether it is precision coordinate position measurement or motion process control, at least two-dimensional precise measurement of the system workbench in two orthogonal directions (such as: X and Y axes) is required. In terms of implementation, one-dimensional measuring elements or devices are usually used in several directions of the workbench to achieve it. In terms of structural form, a stacking method is used to complete the two-degree-of-freedom direction measurement device of the system, that is, multi-degree-of-freedom motion control requires the same number of motion platforms to be superimposed. This combination of workbenches leads to the inevitable Abbe error factor brought by the measuring components on different planes; the inconsistency of the precision characteristics of the measuring components assembled by multiple separate components is also the main factor affecting the accuracy of the workbench.

[0003] Internationally, a practical two-dimensional grating measurement system was first introduced by Heidenhain of Germany. With an orthogonal grid grating structure and an integrated reading method, it realizes the synchronous measurement of displacements in two orthogonal directions in a two-dimensional plane, effectively solving the problems of large Abbe errors and inconsistent measurement accuracy in two directions. Due to its obvious advantages in installation and use, the two-dimensional grating measurement system has been successfully applied in the NXT 1950i lithography machine of ASML, the world's leading lithography machine company, replacing the laser interferometer and improving the overlay accuracy of this model of lithography machine in the X and Y directions to 1.5nm and 1.6nm.

[0004] At present, the two-dimensional grating measurement system has the following two problems in practical application:

[0005] (1) The two-dimensional workbench needs to simultaneously monitor and obtain error test data such as the platform's movement on the orthogonal plane, the straightness of the movement, and the amount of vertical runout, and then perform error compensation through the analysis system to improve movement accuracy.

[0006] (2) The motion control requirements of the ultra-precision workbench include not only the orthogonal directions within the plane, but also the linear motion and other rotational motion control perpendicular to the orthogonal plane direction.

[0007] The above two technical problems are the main difficulties that currently limit the application of two-dimensional grating measurement systems. Summary of the invention

[0008] In order to solve the above problems, the present invention proposes a multi-degree-of-freedom displacement measurement system based on two-dimensional grating.

[0009] The main contents of the present invention include:

[0010] A multi-degree-of-freedom displacement measurement system based on a two-dimensional grating is used to measure the displacement between a fixed component and a moving component, and comprises a reading module and a two-dimensional grating, wherein the reading module and the two-dimensional grating are respectively arranged on the fixed component and the moving component; the reading module comprises an X-direction displacement sensor unit for measuring the displacement in the X direction, a Y-direction displacement sensor unit for measuring the displacement in the Y direction, and a distance sensor for measuring the displacement in the Z direction between the fixed component and the moving component; the X-direction displacement sensor unit comprises two groups of first displacement sensors, and the two groups of the first displacement sensors are arranged along a first direction; the Y-direction displacement sensor unit comprises two groups of second displacement sensors, and the two groups of the second displacement sensors are arranged along a second direction; the first direction and the second direction are perpendicular to each other, and the distance sensor is located at the intersection of the connecting line of the two groups of first displacement sensors and the connecting line of the two groups of second displacement sensors; the two-dimensional grating is used as the measurement basis of the X-direction displacement sensor unit and the Y-direction displacement sensor unit and the reflection surface of the measuring light of the distance sensor.

[0011] Preferably, the distance between the two groups of the first displacement sensors and the distance sensor is the same, denoted as d1; the distance between the two groups of the second displacement sensors and the distance sensor is the same, denoted as d2; wherein d1 is equal to d2 or d1 is not equal to d2.

[0012] Preferably, the reading module includes a reading housing, the X-axis displacement sensor unit, the Y-axis displacement sensor unit and the distance sensor are all arranged on the lower surface of the reading housing, and the reading module is fixedly mounted on the moving part or the fixed part through the reading housing.

[0013] Preferably, the reading module further comprises an information processing unit, and the information processing unit is connected to the X-direction displacement sensor unit, the Y-direction displacement sensor unit and the distance sensor.

[0014] Preferably, the information processing unit includes a sensor subdivision module, an X-direction displacement accuracy compensation module, a Y-direction displacement accuracy compensation module, a rotation angle calculation module and a data interface module; the sensor subdivision module converts the signals transmitted by the X-direction displacement sensor unit, the Y-direction displacement sensor unit and the distance sensor into corresponding digital pulse signals, and transmits the corresponding digital pulse signals to the X-direction accuracy compensation module and the Y-direction accuracy compensation module, respectively; the X-direction accuracy compensation module and the Y-direction accuracy compensation module output standard digital pulse signals, which are then output through the data interface module; the sensor subdivision module is connected to the rotation angle calculation module, converts the signals transmitted by the X-direction displacement sensor unit and the Y-direction displacement sensor unit, and inputs them into the rotation angle calculation module, which outputs the rotation angle through the data interface module after the rotation angle calculation.

[0015] Preferably, the information processing unit is an integrated chip including an FPGA chip, a high-speed AD conversion chip and an ARM processor.

[0016] Preferably, the information processing unit is disposed in the reading housing or is connected to the X-direction displacement sensor unit, the Y-direction displacement sensor unit and the distance sensor through a cable.

[0017] Preferably, the two-dimensional grating includes a grating plate, the grating plate includes a grating substrate and a reflective film layer arranged on the grating substrate, the grating substrate is made of glass, stainless steel, copper, aluminum alloy or zero expansion material; the reflective film layer is an uneven groove structure or a convex structure.

[0018] Preferably, the two-dimensional grating further comprises a mounting platform, a mounting groove is provided at the center of the mounting platform, and the grating sheet is fixedly arranged in the mounting groove by the mounting fixture.

[0019] Compared with the prior art, the multi-degree-of-freedom displacement measurement system based on two-dimensional grating proposed in the present invention has the following effective effects through the arrangement of X-direction displacement sensor units, Y-direction displacement sensor units and distance sensors:

[0020] (1) It makes up for the deficiency that traditional two-dimensional gratings can only measure displacement within a two-dimensional plane, and realizes multi-degree-of-freedom measurement including displacement within a two-dimensional plane, rotation, and displacement perpendicular to the two-dimensional plane, greatly expanding the application scope of two-dimensional gratings;

[0021] (2) By arranging two groups of first displacement sensors and two groups of second displacement sensors in two orthogonal first directions and second directions respectively, not only can displacement data support be provided for the calculation of the rotation amount, but also error compensation between the two groups of first displacement sensors and between the two groups of second displacement sensors can be achieved, thereby effectively improving the accuracy of displacement measurement in a two-dimensional plane;

[0022] (3) By deploying distance sensors, not only can distance measurement perpendicular to the two-dimensional plane displacement be achieved, but also the distance between the reading module and the two-dimensional grating can be adjusted to the optimal reading position based on the displacement data, thereby reducing the difficulty of debugging and improving the signal quality and displacement measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of a reading module of the present invention;

[0025] Figure 3 It is a structural schematic diagram of the reading housing of the present invention;

[0026] Figure 4 A schematic diagram of data processing of the information processing unit of the present invention;

[0027] Figure 5 This is a schematic diagram of the rotation amount calculation of the present invention;

[0028] Figure 6 is a schematic structural diagram of a reflective film layer in one embodiment;

[0029] Figure 7 FIG. 4 is a schematic diagram of the structure of a reflective film layer in another embodiment. DETAILED DESCRIPTION

[0030] The technical solution protected by the present invention is described in detail below with reference to the accompanying drawings.

[0031] See also Figures 1 to 7 The present invention proposes a multi-degree-of-freedom displacement measurement system based on a two-dimensional grating, which is used to measure the displacement between a fixed component and a moving component. Specifically, the measurement system includes a reading module 01 and a two-dimensional grating 03, wherein the reading module 01 and the two-dimensional grating 03 are respectively arranged on the fixed component and the moving component, that is, in one embodiment, the reading module 01 is arranged on the moving component, and the two-dimensional grating 03 is arranged on the fixed component. In another embodiment, the reading module 01 is fixedly arranged on the fixed component, and correspondingly, the two-dimensional grating 03 is fixedly arranged on the moving component. The displacement between the moving component and the fixed component is calculated through the data of the reading module 01 and the two-dimensional grating 03.

[0032] The reading module 01 in the displacement measuring device of the present invention includes an X-direction displacement sensor unit for measuring X-direction displacement, a Y-direction displacement sensor unit for measuring Y-direction displacement, and a distance sensor 31 for measuring Z-direction displacement between a fixed component and a moving component; Figure 2 The X-direction displacement sensor unit comprises two groups of first displacement sensors (11, 12), and the two groups of first displacement sensors (11, 12) are arranged along a first direction; the Y-direction displacement sensor unit comprises two groups of second displacement sensors (21, 22), and the two groups of second displacement sensors (21, 22) are arranged along a second direction; wherein the first direction and the second direction are perpendicular to each other. In this embodiment, the first direction may be the Y direction, and the second direction may be the X direction. Furthermore, the distance sensor 31 is located at a physical center M of the X-direction displacement sensor unit and the Y-direction displacement sensor unit, that is, the distance sensor 31 is arranged at the intersection of a line connecting the two groups of first displacement sensors (11, 12) and a line connecting the two groups of second displacement sensors (21, 22), that is, the distance between the two groups of first displacement sensors (11, 12) and the distance sensor 31 is the same, and the distance between the two groups of second displacement sensors (21, 22) and the distance sensor 31 is the same.

[0033] The distance between the two groups of the first displacement sensors and the distance sensor is recorded as d1; the distance between the two groups of the second displacement sensors and the distance sensor is recorded as d2; in one embodiment, d1 is equal to d2, that is, the distance between the first displacement sensor and the distance sensor is the same as the distance between the second sensor and the distance sensor, the first displacement sensor and the second displacement sensor are respectively located at the diagonals of a square, and the distance sensor is located at the center of the square; in other embodiments, the distance between the first displacement sensor and the distance sensor may be different from the distance between the second sensor and the distance sensor, that is, d1 may not be equal to d2.

[0034] In one embodiment, see Figure 1 and Figure 3 The reading module includes a reading shell, which is surrounded by an upper shell 71 and a lower shell 72. The upper shell 71 and the lower shell 72 are fixed by fixing screws 73 arranged at diagonals, and the X-axis displacement sensor unit, the Y-axis displacement sensor unit and the distance sensor 31 are all arranged on the lower surface of the reading shell. The reading module 01 is fixedly installed on the moving part or the fixed part through the reading shell, such as opening fixing threaded holes 74 on the other two diagonals of the reading shell to fix the reading module to the moving part or the moving part.

[0035] In this embodiment, please refer to Figure 1 and Figure 2 The reading module 01 also includes an information processing unit 02, wherein the information processing unit 02 is connected to the X-direction displacement sensor unit, the Y-direction displacement sensor unit and the distance sensor. Specifically, in one embodiment, the information processing unit 02 can be arranged in a reading housing, or can be arranged separately from the X-direction sensor unit, the Y-direction sensor unit and the distance sensor and arranged in a separate housing. At this time, the two are connected and data is transmitted through a cable 06, which is conducive to the miniaturization of the reading module.

[0036] Specifically, the information processing unit 02 includes a sensor subdivision module 41, an X-axis displacement accuracy compensation module 51, a Y-axis displacement accuracy compensation module 52, a rotation angle calculation module 53 and a data interface module 54; wherein, please combine Figure 4 The sensor subdivision module 41 can convert the 1Vpp measurement signal transmitted by each sensor into a subdivided TTL signal according to the accuracy requirement, that is, the two groups of first displacement sensors (11, 12), the two groups of second displacement sensors (21, 22) and the distance sensor 31 are connected to the sensor subdivision module 41, and the sensor subdivision module 41 converts the transmitted signal 1Vpp into corresponding digital pulse signals TTL respectively; then transmits the corresponding digital pulse signals TTL to the X-axis accuracy compensation module 51 and the Y-axis accuracy compensation module 52 respectively, that is, the sensor subdivision module 41 is connected to the X-axis accuracy compensation module 51 and the Y-axis accuracy compensation module 52, and at the same time, the signal transmitted by the distance sensor 31 is processed and directly output as Z-axis displacement data through the data interface module 54; in addition, the distance sensor 31 can not only realize the distance measurement perpendicular to the two-dimensional plane displacement, but also can adjust the spacing between the reading module and the two-dimensional grating to the optimal reading position according to its displacement data, thereby reducing the debugging difficulty and improving the signal quality and displacement measurement accuracy.

[0037] The digital pulse signal TTL corresponding to the first displacement sensor output by the sensor subdivision module 41 is input to the X-axis precision compensation module 51. Similarly, the digital pulse signal TTL corresponding to the second displacement sensor output by the sensor subdivision module is output to the Y-axis precision compensation module. Subsequently, the X-axis precision compensation module 51 and the Y-axis precision compensation module 52 output standard digital pulse signals and then output the X-axis displacement data and the Y-axis displacement data respectively through the data interface module 54.

[0038] At the same time, the sensor subdivision module 41 is connected to the rotation angle calculation module 53, and converts the signals transmitted from the X-direction displacement sensor unit and the Y-direction displacement sensor unit and inputs them into the rotation angle calculation module 53, that is, the 1Vpp signals of the first displacement sensor and the second displacement sensor are processed into corresponding digital pulse signals TTL by the sensor subdivision module, and then input into the rotation angle calculation module 53 together. After the rotation angle calculation, the rotation angle calculation module 53 outputs the data through the data interface module 54 to obtain the rotation angle data.

[0039] In one embodiment, the information processing unit is an integrated chip including an FPGA chip, a high-speed AD conversion chip and an ARM processor; wherein the sensor segmentation module 41 can use an existing segmentation chip or be implemented by building a segmentation algorithm into the FPGA.

[0040] The two-dimensional grating serves as the measurement basis of the X-axis displacement sensor unit and the Y-axis displacement sensor unit and the reflection surface of the measurement light of the distance sensor. Specifically, the two-dimensional grating includes a grating sheet 03, and the grating sheet 03 includes a grating substrate 81 and a reflective film layer 82 arranged on the grating substrate, wherein the material of the grating substrate 81 is a metal material such as glass, stainless steel, copper, aluminum alloy, or a zero-expansion material, such as the grating substrate 81 can be ordinary soda-lime glass, optical glass, and quartz glass, and the zero-expansion material includes a zero-expansion metal material, a zero-expansion microcrystalline glass, or a zero-expansion ceramic, etc.; and the reflective film layer 82 is an uneven groove structure or a convex structure, please refer to Figure 6 and Figure 7 .

[0041] Please refer to Figure 2 The two-dimensional grating also includes a mounting platform 04 , a mounting groove is provided at the center of the mounting platform 04 , and the grating sheet 03 is fixedly arranged in the mounting groove by the mounting fixture 05 .

[0042] One process for calculating the moving and fixed parts using the present invention is as follows:

[0043] Please refer to Figure 5 , assuming that the reading module 01 is relative to the grating plate 03 by A(X A , Y A ) moves to point B(X B , Y B ), the coordinate points of the two sets of first displacement sensors (11,21) are respectively (X xa , Y xa )、(X' xa , Y' xa ) changes to (Xxb , Y xb )、(X' xb , Y' xb ), and at the same time, the coordinate points of the two sets of second displacement sensors (21, 22) are respectively (X ya , Y ya )、(X' ya , Y' ya ) changes to (X yb , Y yb )、(X' yb , Y' yb ). In this process, the relative rotation amount θ between the reading module 01 and the grating sheet 03 can be calculated by the following formula:

[0044]

[0045] It can also be calculated by the following formula:

[0046]

[0047] Finally, all the measurement and calculation data are output by the data interface module 54 in the information processing unit 02 as X-direction displacement data, Y-direction displacement data, Z-direction displacement data and rotation angle data according to the needs of the equipment driving components, thereby realizing multi-degree-of-freedom measurement.

[0048] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A multi-degree-of-freedom displacement measurement system based on two-dimensional grating, used to measure the displacement between a fixed part and a moving part, characterized in that: It comprises a reading module and a two-dimensional grating, wherein the reading module and the two-dimensional grating are respectively arranged on a fixed component and a moving component; the reading module comprises an X-direction displacement sensor unit for measuring displacement in the X direction, a Y-direction displacement sensor unit for measuring displacement in the Y direction, and a distance sensor for measuring displacement in the Z direction between the fixed component and the moving component; the X-direction displacement sensor unit comprises two groups of first displacement sensors, and the two groups of the first displacement sensors are arranged along a first direction; the Y-direction displacement sensor unit comprises two groups of second displacement sensors, and the two groups of the second displacement sensors are arranged along a second direction; the first direction and the second direction are perpendicular to each other, and the distance sensor is located at the intersection of the connecting line of the two groups of first displacement sensors and the connecting line of the two groups of second displacement sensors; the two-dimensional grating is used as the measurement basis of the X-direction displacement sensor unit and the Y-direction displacement sensor unit and the reflection surface of the measuring light of the distance sensor; The distances between the two groups of the first displacement sensors and the distance sensor are the same, which is denoted as d1; the distances between the two groups of the second displacement sensors and the distance sensor are the same, which is denoted as d2; wherein d1 is equal to d2 or d1 is not equal to d2; The reading module includes a reading housing, the X-axis displacement sensor unit, the Y-axis displacement sensor unit and the distance sensor are all arranged on the lower surface of the reading housing, and the reading module is fixedly mounted on the moving part or the fixed part through the reading housing; The reading module further includes an information processing unit, which is connected to the X-direction displacement sensor unit, the Y-direction displacement sensor unit and the distance sensor; The information processing unit includes a sensor subdivision module, an X-direction displacement accuracy compensation module, a Y-direction displacement accuracy compensation module, a rotation angle calculation module and a data interface module; the sensor subdivision module converts the signals transmitted by the X-direction displacement sensor unit, the Y-direction displacement sensor unit and the distance sensor into corresponding digital pulse signals, and transmits the corresponding digital pulse signals to the X-direction displacement accuracy compensation module and the Y-direction displacement accuracy compensation module respectively; the X-direction displacement accuracy compensation module and the Y-direction displacement accuracy compensation module output standard digital pulse signals and then output them through the data interface module; the sensor subdivision module is connected to the rotation angle calculation module, converts the signals transmitted by the X-direction displacement sensor unit and the Y-direction displacement sensor unit and then inputs them into the rotation angle calculation module, and the rotation angle calculation module outputs the signals through the data interface module after the rotation angle calculation.

2. The multi-degree-of-freedom displacement measurement system based on two-dimensional grating according to claim 1 is characterized in that: The information processing unit is an integrated chip including an FPGA chip, a high-speed AD conversion chip and an ARM processor.

3. The multi-degree-of-freedom displacement measurement system based on two-dimensional grating according to claim 1 is characterized in that: The information processing unit is arranged in the reading housing or connected with the X-direction displacement sensor unit, the Y-direction displacement sensor unit and the distance sensor through a cable.

4. The multi-degree-of-freedom displacement measurement system based on two-dimensional grating according to claim 1, characterized in that: The two-dimensional grating includes a grating sheet, which includes a grating substrate and a reflective film layer arranged on the grating substrate. The grating substrate is made of glass, stainless steel, copper, aluminum alloy or zero-expansion material; the reflective film layer is an uneven groove structure or a convex structure.

5. The multi-degree-of-freedom displacement measurement system based on two-dimensional grating according to claim 4 is characterized in that: The two-dimensional grating also includes a mounting platform, a mounting groove is provided at the center of the mounting platform, and the grating sheet is fixed in the mounting groove by a mounting fixture.

Images