Pupil Detection Device

Abstract

The present invention relates to a pupil detection device, comprising a housing which defines an inner cavity. A first through hole is formed in the housing. Outside the inner cavity, there are a covering window, a first bracket, a lens group, a second bracket and a scintillating crystal. The first bracket is fixed to the housing, the lens group is fixed to the first bracket, the second bracket is fixed to the lens group, a second through hole is provided on the second bracket, and the scintillating crystal is fixed to the second bracket and covers the second through hole; the covering window is fixed to the housing and / or the first bracket and covers the first through hole. A camera is provided in the inner cavity and is fixedly connected to the housing; the scintillating crystal, the second through hole, the lens group, the covering window, the first through hole and the camera are arranged in sequence along the light transmission direction. The scintillating crystal is used to convert EUV light into fluorescence, the lens group is used to magnify and image the fluorescence on the scintillating crystal, and the camera is used to capture an image of the fluorescence on the scintillating crystal. The pupil detection device of the present invention can work normally in a vacuum environment and detect EUV light.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing and detection, and more particularly to a pupil detection device. Background Art

[0002] In the lithography process, a mask (also known as a reticle) is a very critical component, whose main function is to accurately transfer the designed pattern onto a semiconductor wafer, thereby forming tiny and precise circuit structures on the wafer surface. As the chip node shrinks, higher requirements are also put forward for the size of defects inspected in the mask.

[0003] Using a synchrotron radiation source as an EUV (extreme ultraviolet light) source can generate high-brightness and high-energy extreme ultraviolet light. A high-brightness light source can improve the signal-to-noise ratio of mask defect detection, enabling the system to have better sensitivity and resolution when detecting tiny defects. Multiple synchrotron radiation devices at home and abroad have carried out research on EUV mask defect detection systems, and existing synchrotron radiation devices all adopt the method of Fourier synthesis illumination to improve the resolution of mask defect imaging.

[0004] Off-axis illumination is a typical Fourier synthesis method. Usually, an MEMS (microelectromechanical system) galvanometer is used for angular scanning, and an ellipsoidal mirror is used for focusing. The center point of the MEMS galvanometer is located at the first focus of the ellipsoidal mirror, then the scanning beam generated by the MEMS mirror converges to the second focus of the ellipsoidal mirror, and the plane where this focus is located is the mask plane. Using the MEMS galvanometer for angular scanning can make the incident angle of the light deviate from the optical axis to enhance the high-frequency components of the illumination system, achieving the purpose of enhancing the resolution of the EUV mask defect detection system. By programming and designing to control the angular scanning of the MEMS galvanometer, enabling the beam to scan on the pupil plane along a certain trajectory, various different types of illumination patterns (such as annular illumination, bipolar illumination, quadrupole illumination, etc.) can be created, so that the EUV mask defect detection system can more flexibly meet the detection requirements for different defects.

[0005] To ensure the performance of the pupil and enable the EUV mask defect detection system to achieve high-resolution imaging of mask defects, it is necessary to diagnose the synthesized illumination pattern and its parameters such as light intensity uniformity, coherence factor, and incident angle. The existing detectors for collecting pupil images use image sensors such as CCD or CMOS cameras, which generally cannot be directly used in a vacuum environment better than 1e-7 torr. The finished vacuum cameras are expensive, large in size, and very difficult to install. Ordinary industrial cameras cannot work directly in a vacuum environment. Firstly, it is difficult to dissipate heat through conventional convection and conduction heat dissipation methods in a vacuum, mainly relying on thermal radiation to dissipate heat, with low heat dissipation efficiency and easy to be damaged. Secondly, industrial cameras themselves will release gas, damaging the vacuum environment of the EUV mask defect detection system. Thirdly, the spectral response range of most industrial cameras is from 350nm to 1000nm, not including the EUV band.

[0006] Therefore, it is very necessary to develop a pupil detection device that can work normally in a vacuum environment for the EUV mask defect detection system to improve the imaging resolution of the EUV mask defect detection system. Summary of the Invention

[0007] The purpose of the present invention is to provide a pupil detection device that can work normally in a vacuum environment and collect the pupil image of the EUV mask defect detection system.

[0008] Based on the above purpose, the present invention provides a pupil detection device, including a housing, the housing defining an inner cavity, the housing being provided with a first through hole, outside the inner cavity there are a covering window, a first bracket, a lens group, a second bracket, and a scintillation crystal, the first bracket being fixed to the housing, the lens group being fixed to the first bracket, the second bracket being fixed to the lens group, the second bracket being provided with a second through hole, the scintillation crystal being fixed to the second bracket and covering the second through hole; the covering window is fixed to the housing and / or the first bracket and covers the first through hole, a camera is provided in the inner cavity, the camera being fixedly connected to the housing; the scintillation crystal, the second through hole, the lens group, the covering window, the first through hole, and the camera are arranged in sequence along the light transmission direction, the scintillation crystal is used to convert EUV light into fluorescence, the lens group is used to magnify and image the fluorescence on the scintillation crystal, and the camera is used to capture the image of the fluorescence on the scintillation crystal.

[0009] Furthermore, the lens group is detachably connected to the first bracket and the second bracket respectively, so as to adjust the distance between the lens group and the camera by adjusting the relative position between the lens group and the first bracket, and to adjust the distance between the lens group and the scintillation crystal by adjusting the relative position between the lens group and the second bracket.

[0010] Furthermore, the lens group is an achromatic lens group.

[0011] Furthermore, the top of the camera is fixedly connected to the housing, and a thermal pad is filled between the bottom of the camera and the inner wall of the housing.

[0012] Furthermore, a temperature sensor is provided at the bottom of the camera.

[0013] Furthermore, a conversion circuit board is also provided in the inner cavity, and the conversion circuit board includes a wire-to-board connector and a DB15 connector. The wire-to-board connector is electrically connected to the camera through a first wire, and is electrically connected to the temperature sensor through a second wire. A DB15 interface is provided on the outer shell, and the DB15 connector is plugged into the DB15 interface.

[0014] Furthermore, the material of the scintillation crystal is Ce:YAG, and the material of the cover window is sapphire.

[0015] Furthermore, a mark is engraved on the upper surface of the scintillation crystal.

[0016] Furthermore, a sealing ring is provided between the cover window and the shell.

[0017] Furthermore, it is applied to an EUV mask defect detection system, which includes a galvanometer, a reflector, an ellipsoidal reflector, a three-dimensional motion control console and a vacuum chamber, wherein the galvanometer, the reflector, the ellipsoidal reflector and the three-dimensional motion control console are all located in the vacuum chamber, the galvanometer is used to make EUV light emit at different angles, the reflector is used to reflect the EUV light emitted from the galvanometer onto the ellipsoidal reflector, and the ellipsoidal reflector is used to focus the EUV light onto one of the focal points of the ellipsoidal reflector, and the horizontal plane where the focus is located is used as the mask plane; the pupil detection device is arranged on the three-dimensional motion control console and is located directly below the mask plane.

[0018] The pupil detection device of the present invention can work in a vacuum chamber with a vacuum degree better than 1e-7torr, and detect the synthetic illumination mode in the EUV mask defect detection system. The design is compact and no structural modification of the EUV mask defect detection device is required for installation and use. The operating temperature of the camera is monitored by a temperature sensor to avoid damage due to excessive temperature, thereby improving the reliability of the pupil detection device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a stereoscopic diagram of a pupil detection device according to an embodiment of the present invention after a scintillation crystal is removed;

[0020] Figure 2 The right view of the pupil detection device according to an embodiment of the present invention;

[0021] Figure 3 is Figure 2 the A-A sectional view of;

[0022] Figure 4 The structural schematic diagram of the adapter circuit board of the pupil detection device according to an embodiment of the present invention;

[0023] Figure 5 The schematic diagram when the pupil detection device according to an embodiment of the present invention is applied to an EUV mask defect detection system;

[0024] Figure 6 The schematic diagram of the principle for the pupil detection device according to an embodiment of the present invention to detect the incident angle of EUV light. Specific embodiments

[0025] The following combines the accompanying drawings to give the preferred embodiments of the present invention and describes them in detail.

[0026] As Figure 1 , Figure 2 and Figure 3 shown, an embodiment of the present invention provides a pupil detection device, including a housing 100, a covering window 200, a first bracket 310, a lens group 320, a second bracket 330, a scintillating crystal 400 and a camera 500. The housing 100 defines an inner cavity 110. A first through hole 120 is formed on the housing 100. The covering window 200, the first bracket 310, the lens group 320, the second bracket 330 and the scintillating crystal 400 are located outside the inner cavity 110. The first bracket 310 is fixed on the housing 100. The lens group 320 is fixed on the first bracket 310. The second bracket 330 is fixed on the lens group 320. A second through hole 331 is provided on the second bracket 330. The scintillating crystal 400 is fixed on the second bracket 330 and covers the second through hole 331. The covering window 200 is fixed to the housing 100 and / or the first bracket 310 and covers the first through hole 120. The camera 500 is located in the inner cavity 110 and is fixedly connected to the housing 100; the scintillating crystal 400, the second through hole 331, the lens group 320, the covering window 200, the first through hole 120 and the camera 500 are arranged in sequence along the light transmission direction. The scintillating crystal 400 is used to receive EUV light and convert the EUV light into fluorescence detectable by the camera 500 (i.e., fluorescence in the visible light band). The fluorescence is sequentially received by the camera 500 after passing through the lens group 320, the covering window 200 and the first through hole 120. The lens group 320 is used to magnify and image the light spot on the scintillating crystal 400. The camera 500 is used to capture an image of the light spot on the scintillating crystal 400.

[0027] In some embodiments, the distances between the lens group 320 and the camera 500 and between the lens group 320 and the scintillation crystal 400 are set to be adjustable. By adjusting these two distances, the focusing of the lens group 320 can be achieved, so that the object-side focal plane of the lens group 320 coincides with the upper surface of the scintillation crystal 400, and the image-side focal plane of the lens group 320 coincides with the image sensor of the camera 500. Specifically, the lens group 320 can be detachably connected to the first bracket 310 and the second bracket 330 respectively. By adjusting the relative position between the lens group 320 and the first bracket 310, the distance between the lens group 320 and the camera 500 can be adjusted, and by adjusting the relative position between the second bracket 330 and the lens group 320, the distance between the lens group 320 and the scintillation crystal 400 can be adjusted.

[0028] In some embodiments, the lens group 320 is an achromatic lens group, which is used to minimize chromatic aberration and spherical aberration.

[0029] In some embodiments, the top of the camera 500 (the side where the image sensor is located) is fixedly connected to the housing 100, and a thermal pad 600 is filled between the bottom of the camera 500 (the side where the chip is located) and the inner wall of the housing 100 (i.e., the bottom plate) for conducting the heat of the camera 500 to the housing 100 through the thermal pad 600 and then dissipating it outward by the housing 100, thereby improving the heat dissipation efficiency. Exemplarily, the thermal pad 600 can be a silicone pad with a thickness of 3 mm, a thermal conductivity of 13 W / (m·K), and a temperature resistance range of -40~+200 °C. The thermal pad 600 is insulated, compression-resistant, and sticky. The thermal pad 600 can be multiple pieces and stacked between the camera 500 and the housing 100 to form a certain extrusion to increase the structural stability. Within the allowable range of space, the bottom plate of the housing 100 can be designed to be larger to increase the heat radiation area and improve the heat dissipation efficiency.

[0030] In some embodiments, a temperature sensor 700 can be provided at the bottom of the camera 500 for monitoring the operating temperature of the camera 500. The temperature sensor 700 can be arranged between the camera 500 and the thermal pad 600.

[0031] In some embodiments, the scintillation crystal 400 can be Ce:YAG, that is, cerium-doped yttrium aluminum garnet. The size of the scintillation crystal 400 can be selected according to needs. For example, a scintillation crystal with a thickness of 300 μm and a diameter of 15 mm can be selected. The scintillation crystal 400 can be pasted on the upper surface of the second bracket 330 with silver glue.

[0032] A mark may be pre-engraved on the upper surface of the scintillation crystal 400. For example, a laser may be used to engrave a line with a width of 50 um at a distance of 2.5 mm from the center point of the scintillation crystal 400. The mark is used to adjust the focal length of the lens group 320. Specifically, when adjusting the distance between the lens group 320, the scintillation crystal 400 and the camera 500, the clarity of the mark on the upper surface of the scintillation crystal 400 captured by the camera 500 may be observed at the same time. When the image of the mark is clear in the field of view of the camera 500 and the width is the magnification of the lens group 320*50 um, it indicates that the adjustment is in place, and the lens group 320 may be fixed to the first bracket 310 and the second bracket 330.

[0033] The lens group 320 may be a 2x magnification lens group with an effective aperture of 9.5 mm and an applicable wavelength range of 400-700 nm.

[0034] In some embodiments, the cover window 200 can be made of Al2O3 sapphire. Sapphire is second only to diamond in hardness in nature, with a Mohs hardness of 9 and a melting point of 2050°C. It will not release gas or undergo thermal expansion at high temperatures and can remain stable under vacuum conditions, making it an ideal observation window material for vacuum devices. The cover window 200 can be circular, with a diameter of 25 mm and a thickness of 3 mm, and is polished on both sides. After EUV light excitation, the main emission peak of the fluorescence emitted by the scintillation crystal 400 is about 550 nm, and the light transmittance of sapphire to this wavelength is greater than 80%.

[0035] In some embodiments, the camera 500 is a board-level CMOS camera, model BFS-U3-32S4-BD2, with a pixel size of 3.45um and a pixel number of 2048x1536. Combined with the lens group 320, the field of view of the camera 500 is 3.5mm×2.6mm, and the theoretical spatial resolution is about 1.73um. The bottom of the camera 500 is the side where the main control chip is located. The main control chip is the main heating device of the camera 500, and the operating temperature range is 0~50℃.

[0036] In some embodiments, a switching circuit board 800 is further provided in the inner cavity 110. Figure 4As shown, the adapter circuit board 800 includes a wire-to-board connector 810 and a DB15 connector 820. The wire-to-board connector 810 is electrically connected to the camera 500 through a first wire 830 and to the temperature sensor 700 through a second wire 840. There is also a DB15 interface 130 on the housing 100, and the DB15 connector 820 is inserted into the DB15 interface for mating connection. The adapter circuit board 800 is used to convert the signals of the wire-to-board connector 810 into the signals of the standard DB15 connector 820, and then lead them out to the outside of the inner cavity 110 through the DB15 interface 130 on the housing 100. The DB15 interface 130 can be connected to a host computer (not shown in the figure) outside the inner cavity 110 to control the camera 500 and process its image data through the host computer.

[0037] In some embodiments, a sealing ring 210 can be provided between the cover window 200 and the housing 100 for sealing. The housing 100 can be composed of multiple detachable parts connected to each other, and the connection parts between the detachable parts can also be sealed, so that the inner cavity 110 is formed into a sealed cavity.

[0038] As Figure 5 As shown, the pupil detection device of the embodiment of the present invention is applied to an EUV mask defect detection system to detect the pupil of the EUV mask defect detection system. The EUV mask defect detection system includes a galvanometer 910, a mirror 920, an ellipsoidal mirror 930, a zone plate 940, and a CCD (Charge Coupled Device) detector 950. EUV light is incident on the galvanometer 910, and the galvanometer 910 is used for angular scanning so that the incident EUV light exits at different angles. The mirror 920 and the ellipsoidal mirror 930 collect the exiting light beam and focus it on one of the foci of the ellipsoidal mirror 930. The horizontal plane where this focus is located is the mask plane 960. When performing defect detection, a mask plate (not shown in the figure) is placed on the mask plane 960. The EUV light irradiates the mask plate and is reflected by the mask plate. The zone plate 940 is used to magnify the reflected light of the mask plate and project it onto the CCD detector 950 for imaging. Whether there are defects on the mask plate can be determined through the image detected by the CCD detector 950. Before scanning the mask plate, it is necessary to first use the pupil detection device to detect the illumination mode of the EUV mask defect detection system. The distribution of the direct transmitted light below the mask plane 960 and the reflected light reflected from the mask plate is equivalent. Therefore, the pupil detection device can be used to image the direct transmitted light below the mask plane 960, and thus the distribution information of the reflected light on the zone plate 940 can be indirectly obtained.

[0039] The EUV mask defect detection system further includes a three-dimensional motion console 970. The pupil detection device is placed on the three-dimensional motion console 970 and is located directly below the mask surface 960. The three-dimensional motion console 970 can move the pupil detection device in the X direction (the X direction is perpendicular to the YZ plane), in the Y direction, and in the Z direction. The X-direction motion range is 100 mm, the Y-direction motion range is 100 mm, and the Z-direction motion range is 40 mm.

[0040] The EUV mask defect detection system further includes a vacuum chamber 980. The galvanometer 910, the mirror 920, the ellipsoidal mirror 930, the zone plate 940, the CCD detector 950, the three-dimensional motion console 970, and the pupil detection device are all located inside the vacuum chamber 980. The DB15 interface 130 of the pupil detection device can be connected to the DB15 interface on the vacuum chamber 980 using a vacuum cable, and then connected to the temperature controller 991, the USB3.0 interface 992, and the galvanometer controller 993 through the DB15 interface on the vacuum chamber 980. The temperature controller 991 is used to connect to the temperature sensor 700 to monitor the operating temperature of the camera 500 and prevent the camera 500 from being damaged due to overheating for a long time. The USB3.0 interface 992 is used to connect to the data cable of the camera 500 to transmit the image data of the camera 500 to the host computer 994 through USB3.0. The galvanometer controller 993 is used to connect to the external trigger signal line of the camera 500 to input an external trigger acquisition signal to the camera 500 to achieve synchronous acquisition of pupil detection and galvanometer scanning.

[0041] When performing pupil detection, the three-dimensional motion console 970 can be used to move the pupil detection device into the optical path and make the pupil image observed by the camera 500 located at the center of the field of view. When the three-dimensional motion console 970 moves the pupil detection device in the Z direction, the pattern of the pupil image detected by the pupil detection device is related to the distance between the pupil detection device and the mask surface 960. When the upper surface of the scintillation crystal 400 coincides with the mask surface 960, as the galvanometer 910 scans, the pupil image I0 is an unchanged light spot. When the pupil detection device is at a certain distance away from the mask surface 960, the light beam is no longer focused and presents a pattern consistent with the scanning trajectory of the galvanometer 910, as shown by the pupil image I1. As the pupil detection device moves further away from the mask surface 960, the pupil image becomes larger, the distance between adjacent light beams becomes farther, and the scanning beam trajectory becomes clearer, as shown by the pupil image I2.

[0042] The relationship between the size of the pupil and the incident angle range and defocus distance of the light beam at the mask surface 960 is as follows:

[0043]

[0044] Wherein, h is the distance between the upper surface of the scintillating crystal 400 and the mask surface 960 in the Z direction. When h is equal to the focal length of the zone plate 940, the pupil detected by the pupil detection device at this time is equal in size to the pupil at the zone plate 940. is the minimum incident angle in the current illumination mode, is the maximum incident angle, and S is the maximum size of the pupil at the current h distance. When the size of S exceeds the field of view of the pupil detection device, the pupil detection device can be horizontally moved by the three-dimensional motion control console 970 to collect images of multiple regions, and then the images of each region are stitched together to obtain a complete pupil image. Specifically, when the size of the pupil image is greater than the field of view of the pupil detection device, the image observed by the pupil detection device is only a part of the complete pupil image, and the images collected by the pupil detection device at different positions are different parts of the complete pupil image. Therefore, stitching them together gives the complete pupil image.

[0045] The pupil detection device of the embodiment of the present invention can also detect the incident angle of the light beam at the mask surface 960, and the measurement principle is as Figure 6 shown. First, two pupil images are collected. One is the pupil image at a defocus distance of 0 (i.e., the distance between the scintillating crystal 400 and the mask surface 960) (which can be called the mask surface pupil image), and the other is the pupil image at a defocus distance of h (which can be called the defocus surface pupil image). In order to distinguish the positions of two adjacent light beams, h can satisfy the following relational expression:

[0046]

[0047] Wherein, is the minimum incident angle of the light beam at the mask surface, is the minimum angle between two adjacent light beams in the current scanning mode, d is the diameter of the EUV light spot, and M is the magnification of the lens group 320. Exemplarily, the diameter of the EUV light spot is 30um, M is 2, =2mrad, then h is at least 7.5mm.

[0048] Extract the center positions of each light spot in the two pupil images. Denote the center coordinates of the light spots in the mask surface pupil image as (x0, y0), and the center coordinates of the light spots in the defocus surface pupil image as (x i , y i ) (i is a positive integer representing the serial number of the light spot, i ∈ [0, N - 1], and N is the number of light spots in the defocus surface pupil image), s is the horizontal distance between two light spots, and the incident angle of each light beam at the mask surface is calculated as follows:

[0049]

[0050] The method for collecting pupil images of the pupil detection device according to the embodiment of the present invention includes the following steps:

[0051] S1: Provide the pupil detection device in the above embodiment and install it on the three-dimensional motion console 970 of the EUV mask defect detection system;

[0052] S2: Set the galvanometer 910 to deflect only by an angle so that the EUV light deflects to the central angle in the pre-scanning mode;

[0053] S3: Move the pupil detection device into the optical path through the three-dimensional motion console 970 so that the upper surface of the scintillation crystal 400 coincides with the mask surface 960;

[0054] S4: Open the camera acquisition software and slowly move the pupil detection device hmm along the Z-axis. During the movement, continuously move the pupil detection device horizontally so that the image of the light spot is always located at the center of the image;

[0055] S5: Set the exposure time of image acquisition according to the scanning rate and the number of scanning points of the galvanometer 910;

[0056] Exposure time = k × number of scanning points / scanning rate.

[0057] k is an integer. If the image signal is relatively weak, the exposure time can be increased by an integer multiple;

[0058] S6: Set the scanning trajectory of the galvanometer 910 and drive the galvanometer 910 to scan;

[0059] S7: Whenever the galvanometer 910 starts to scan the first angle of the preset pattern, make the galvanometer controller 993 output a pulse signal, set the trigger mode of the camera 500 to the external trigger mode, and collect and save the image;

[0060] S8: Stop the galvanometer scanning and set the polarization angle of the galvanometer to the central angle;

[0061] S9: Slowly move the three-dimensional motion console along the Z-axis by a total of h mm so that the upper surface of the scintillation crystal 400 coincides with the mask surface 960, adjust the exposure time to a suitable value to avoid overexposure of the image, set the trigger mode of the camera 500 to the internal trigger mode, and collect and save the image.

[0062] The pupil detection device according to the embodiment of the present invention can work in a vacuum chamber with a vacuum degree better than 1e-7 torr, detect the synthetic illumination mode in the EUV mask defect detection system, has a compact design, and does not require structural modification of the EUV mask defect detection device for installation and use; the working temperature of the camera 500 is monitored through the temperature sensor 700 to avoid damage due to excessive temperature, improving the reliability of the pupil detection device.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various changes can be made to the above embodiments of the present invention. That is, all simple, equivalent changes and modifications made in accordance with the claims and the content of the specification of the present invention application fall within the scope of protection of the claims of the present invention patent. Those not described in detail in the present invention are all conventional technical contents.

Claims

1. An EUV mask defect detection system, characterized in that, The pupil detection device comprises a shell, the shell defines an inner cavity, a first through hole is formed on the shell, a cover window, a first bracket, a lens group, a second bracket and a scintillation crystal are arranged outside the inner cavity, the first bracket is fixed to the shell, the lens group is fixed to the first bracket, the second bracket is fixed to the lens group, a second through hole is formed on the second bracket, the scintillation crystal is fixed to the second bracket and covers the second through hole; the cover window is fixed to the shell and / or the first bracket and covers the first through hole, a camera is arranged in the inner cavity, and the camera is fixedly connected to the shell; the scintillation crystal, the second through hole, the lens group, the cover window, the first through hole and the camera are arranged in sequence along the light transmission direction, the scintillation crystal is used to convert EUV light into fluorescence, the lens group is used to amplify and image the fluorescence on the scintillation crystal, and the camera is used to capture an image of the fluorescence on the scintillation crystal; The lens group is detachably connected to the first bracket and the second bracket respectively, so that the distance between the lens group and the camera can be adjusted by adjusting the relative position between the lens group and the first bracket, and the distance between the lens group and the scintillation crystal can be adjusted by adjusting the relative position between the lens group and the second bracket; The EUV mask defect detection system also includes a galvanometer, a reflector, an ellipsoid reflector, a three-dimensional motion console and a vacuum chamber, wherein the galvanometer, the reflector, the ellipsoid reflector and the three-dimensional motion console are all located in the vacuum chamber, the galvanometer is used to make EUV light emit at different angles, the reflector is used to reflect the EUV light emitted from the galvanometer onto the ellipsoid reflector, and the ellipsoid reflector is used to focus the EUV light onto one of the focal points of the ellipsoid reflector, and the horizontal plane where the focal point is located is used as the mask surface; the pupil detection device is arranged on the three-dimensional motion console and is located directly below the mask surface; the three-dimensional motion console moves the pupil detection device relative to the mask surface so that the camera collects the pupil image of the mask surface and the pupil image of the defocused surface; the camera is connected to a galvanometer controller located outside the vacuum chamber, and the galvanometer controller is used to input an external trigger acquisition signal to the camera to realize the synchronous acquisition of pupil detection and galvanometer scanning; The incident angle of the light beam at the mask surface is determined according to the mask surface pupil image and the through-focus surface pupil image.

2. The EUV mask defect detection system according to claim 1, wherein, The lens group is an achromatic lens group.

3. The EUV mask defect detection system according to claim 1, wherein The top of the camera is fixedly connected to the housing, and a thermal pad is filled between the bottom of the camera and the inner wall of the housing.

4. The EUV mask defect detection system according to claim 1, characterized in that, A temperature sensor is provided at the bottom of the camera.

5. The EUV mask defect detection system according to claim 4, wherein A transfer circuit board is also provided in the inner cavity, and the transfer circuit board includes a wire-to-board connector and a DB15 connector. The wire-to-board connector is electrically connected to the camera through a first wire, and is electrically connected to the temperature sensor through a second wire. A DB15 interface is provided on the outer shell, and the DB15 connector is plug-connected to the DB15 interface.

6. The EUV mask defect detection system according to claim 1, characterized in that, The material of the scintillation crystal is Ce:YAG, and the material of the covering window is sapphire.

7. The EUV mask defect detection system according to claim 1, wherein, Marks are engraved on the upper surface of the scintillation crystal.

8. The EUV mask defect detection system according to claim 1, wherein A sealing ring is provided between the covering window and the housing.

Images