A device and method for detecting mask surface photoresist particles

Abstract

This invention relates to the detection of photoresist particles, specifically to a detection device and method for photoresist particles on the surface of a photomask. A beam splitter divides a combined beam into two paths: a reference beam and a measurement beam. A reference reflector reflects the reference beam back to the beam splitter along its original path. A measurement objective focuses the measurement beam onto the photoresist layer on the photomask surface. The measurement beam, carrying surface information, returns to the beam splitter and interferes with the reference beam. A photodetector array receives the interference signal, converts the interference intensity distribution into an interference image, and sends it to a signal processing unit for processing. The signal processing unit receives the interference image, reconstructs the three-dimensional morphology of the photomask surface, automatically identifies photoresist particles, generates a detection report, and periodically performs system self-calibration. The technical solution provided by this invention effectively overcomes the shortcomings of existing technologies in accurately and efficiently detecting photoresist particles on the surface of photomasks.

Description

Technical Field

[0001] This invention relates to the detection of photoresist particles, specifically to a device and method for detecting photoresist particles on the surface of a photomask. Background Technology

[0002] Before photolithography, a layer of photoresist exists on the surface of the photomask. The laser lithography beam acts on the photoresist and forms a specific pattern through subsequent wet processing. Particles on the surface of the photoresist can block the beam from reaching the photoresist surface, causing defects in the micro-pattern, increasing the difficulty of subsequent maintenance, and even causing the photomask to be scrapped.

[0003] Currently, most mainstream photomask manufacturers rely on employees to visually inspect the photoresist surface for particles, using red spotlights at specific angles to examine the particles and then removing them with an air gun. This manual inspection method has many drawbacks, such as the risk of particles falling from personnel, potential for human error in missing particles, and the inability to accurately detect some particles in the photoresist. Therefore, a new photoresist particle detection solution for photomask surfaces needs to be designed. Summary of the Invention

[0004] (a) Technical problems to be solved In view of the above-mentioned shortcomings of the prior art, the present invention provides a detection device and method for photoresist particles on the surface of a photomask, which can effectively overcome the shortcomings of the prior art in that it is difficult to accurately and efficiently detect photoresist particles on the surface of a photomask.

[0005] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: A device for detecting photoresist particles on the surface of a photomask includes the following components: A dual-wavelength laser source that emits two laser beams of different wavelengths; A beam combiner combines two laser beams into one beam. The two-dimensional scanning galvanometer can be rapidly deflected around the X and Y axes to achieve two-dimensional scanning of the combined beam on the mask surface; A beam splitter divides the combined beam into two paths: one is a reference beam, and the other is a measurement beam. The reference beam mirror reflects the reference beam back to the beam splitter along the original path; The measurement objective focuses the measurement beam onto the photoresist layer on the surface of the mask. The measurement beam carries the surface information and returns to the beam splitter, where it interferes with the reference beam. The photodetector array receives interference signals, converts the interference light intensity distribution into an interference image, and sends it to the signal processing unit for processing. The signal processing unit receives interference images, reconstructs the three-dimensional morphology of the mask surface, automatically identifies photoresist particles, generates inspection reports, and periodically performs system self-calibration.

[0006] Preferably, the dual-wavelength laser source includes a first laser source and a second laser source, wherein the first laser source is a He-Ne laser with a wavelength of 632nm and the second laser source is a semiconductor laser with a wavelength of 660nm.

[0007] Preferably, it further includes a mask support unit for supporting and driving the mask to move in the Y direction, the mask support unit including a support platform and a drive motor; A Y-axis movable platform is slidably connected to the support platform. Pin column lifting channels are evenly distributed inside the support platform and the Y-axis movable platform. Pin columns that provide temporary support when loading the mask are installed inside the pin column lifting channels. Multiple air-bearing nozzles are evenly distributed on the Y-axis movable platform to form an air-bearing nozzle array, which is used to form an air film between the mask and the Y-axis movable platform. A flexible clamp is fixed to the edge of the Y-axis movable platform to prevent the mask from horizontally drifting on the air film. A lead screw is fixed on the drive shaft of the drive motor, and the Y-axis moving platform is threadedly connected to the lead screw.

[0008] Preferably, the loading process of the mask includes: When the mask is not loaded, the pin pillars are in the raised state; An external robotic arm slowly places the mask onto the pin post. After the robotic arm moves away, the pin post, carrying the mask, slowly descends. When the pin column descends to the specified height, the air flotation nozzle ejects compressed air to form an air film between the mask and the Y-axis moving stage; When the mask and the Y-axis moving stage reach a specified distance, the flexible gripper begins to clamp the side of the mask to prevent the mask from drifting horizontally on the air film. The pin column descends into the support platform to prevent movement restrictions on the Y-axis moving platform.

[0009] Preferably, the photodetector array is a high-sensitivity CMOS camera array, and the photodetector array and the X-direction crossbridge have an air-float-filled contact gap for movement along the X-direction.

[0010] Preferably, the signal processing unit has the following functions: Data acquisition and synchronization control: Receives interference images and maintains real-time communication with the light source controller, galvanometer controller, and mask support unit controller to ensure that the interference data of each pixel corresponds precisely to its spatial coordinates; Phase calculation and 3D reconstruction: Extract phase information from the interference light intensity distribution, calculate the absolute height, and reconstruct the 3D morphology of the mask surface; Particle identification: Based on the three-dimensional morphology of the mask surface, the height, size and position of photoresist particles are identified, and the type is determined according to the three-dimensional morphological characteristics. Data storage and report output: Save interference images, particle identification results and particle distribution maps, generate detection reports, and store them in association with the mask ID; System calibration and error compensation: The test report is sent to the back-end particle cleaning unit, and the system self-calibration is performed regularly to compensate for measurement errors caused by environmental vibration, temperature drift and optical system distortion.

[0011] Preferably, the signal processing unit extracts phase information from the interference light intensity distribution, calculates the absolute height, and reconstructs the three-dimensional morphology of the mask surface, including: S11, Equivalent Wavelength Combination: The laser wavelengths emitted by the first laser source and the second laser source are respectively... , ,and and Similarly, an equivalent wavelength can be synthesized using two-wavelength interference. : ; equivalent wavelength Much larger and equivalent wavelength The corresponding phase change range covers the maximum optical path difference that may be caused by the height of the photoresist particles, thus solving the phase ambiguity problem and realizing unambiguous measurement of the height of the photoresist particles; S12, Height Calculation: Collect data separately. , The corresponding interference signals are used to calculate their respective envelope phases. , The composite phase is calculated using the phase difference method. Then the height distribution h(x,y) on the mask surface is: ; The algorithm described above can accurately reconstruct the three-dimensional morphology of the mask surface and accurately determine the photoresist particles based on the height threshold and lateral dimension.

[0012] A method for detecting photoresist particles on the surface of a photomask includes the following steps: S1. The photodetector array is aligned with the surface of the mask. While moving back and forth along the X-axis transverse bridge, it performs optical detection on the photoresist particles on the surface of the mask. The area on the surface of the mask detected by one X-axis movement is recorded as the X-axis detection scanning area. S2. After the photodetector array completes one X-axis movement along the X-axis transverse bridge, the Y-axis moving stage moves one step along the Y-axis under the action of the drive motor and lead screw. In order to avoid missed scans, there is a scanning overlap area between adjacent X-axis detection scanning areas. S3. Repeat S1 and S2 until the photoresist particle detection of the entire mask is completed. S4. The photodetector array receives the interference signal, converts the interference light intensity distribution into an interference image, and sends it to the signal processing unit for processing. S5. The signal processing unit extracts phase information from the interference light intensity distribution, calculates the absolute height, reconstructs the three-dimensional morphology of the mask surface, identifies the height, size and position of the photoresist particles based on the three-dimensional morphological characteristics, determines the type of the particles, saves the interference image, particle identification results and particle distribution map, generates a detection report, and sends the detection report to the back-end particle cleaning unit for processing.

[0013] Preferably, the signal processing unit extracts phase information from the interference light intensity distribution, calculates the absolute height, and reconstructs the three-dimensional morphology of the mask surface, including: S11, Equivalent Wavelength Combination: The laser wavelengths emitted by the first laser source and the second laser source are respectively... , ,and and Similarly, an equivalent wavelength can be synthesized using two-wavelength interference. : ; equivalent wavelength Much larger and equivalent wavelength The corresponding phase change range covers the maximum optical path difference that may be caused by the height of the photoresist particles, thus solving the phase ambiguity problem and realizing unambiguous measurement of the height of the photoresist particles; S12, Height Calculation: Collect data separately. , The corresponding interference signals are used to calculate their respective envelope phases. , The composite phase is calculated using the phase difference method. Then the height distribution h(x,y) on the mask surface is: ; The algorithm described above can accurately reconstruct the three-dimensional morphology of the mask surface and accurately determine the photoresist particles based on the height threshold and lateral dimension.

[0014] (III) Beneficial Effects Compared with the prior art, the detection device and method for photoresist particles on the surface of a photomask provided by the present invention have the following advantages: 1) Red light, which is insensitive to photoresist, is used as the light source, and dual-wavelength interference detection is adopted to avoid the drawbacks of traditional visual inspection of photoresist particles. While ensuring detection accuracy, the possibility of plate contamination is reduced. 2) The design of using air-floating nozzles to form an air film to lift the plate material fundamentally avoids the situation of direct contact causing damage or scratches to the mask surface; 3) It can store the height, size and position information of photoresist particles, and can compare back-end defects with detection signals, providing a data reference for improving back-end particle cleaning solutions. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0016] Figure 1 This is a schematic diagram of the device structure of the present invention; Figure 2 This is a top view of the mask support unit in this invention. Figure 3 This is a side view of the mask support unit in this invention. Figure 4 This is a schematic diagram showing the photodetector array moving in coordination with the Y-axis moving platform in this invention. Figure 5 This is a schematic diagram of the scanning overlap region in this invention; Figure 6 This is a schematic diagram illustrating the detection principle of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] The following describes the specific components of the photoresist particle detection device on the mask surface provided by the present invention, using specific examples (such as...). Figure 1 (As shown) and its technical effects. The device components include: A dual-wavelength laser source that emits two laser beams of different wavelengths; Beam combiner 3 combines two laser beams into one beam; The two-dimensional scanning galvanometer 4 can be rapidly deflected around the X and Y axes to achieve two-dimensional scanning of the combined beam on the mask surface; 5 beam splitter prism (50:50 splitting ratio) splits the combined beam into two paths, one for reference and the other for measurement. The reference light reflector 6 (a plane reflector, mounted on a precision displacement stage, used for initial phase zeroing) reflects the reference beam back to the beam splitter 5 along the original path; The measuring objective lens 7 focuses the measuring beam onto the photoresist layer 10 on the surface of the mask 11. The measuring beam carries the surface information and returns to the beam splitter 5, interfering with the reference beam. The photodetector array 8 receives the interference signal and converts the interference light intensity distribution into an interference image, which is then sent to the signal processing unit 9 for processing. Signal processing unit 9 receives interference images, reconstructs the three-dimensional morphology of the mask surface, automatically identifies photoresist particles, generates inspection reports, and periodically performs system self-calibration.

[0019] I. Dual-wavelength laser source The dual-wavelength laser source (due to the sensitivity of photoresist to white light, a dual-wavelength red laser source is adopted based on its photosensitive characteristics) includes a first laser source 1 and a second laser source 2. The first laser source 1 adopts a He-Ne laser with a wavelength of 632nm, and the second laser source 2 adopts a semiconductor laser with a wavelength of 660nm.

[0020] II. Mask Plate Bearing Unit Given the dimensions of the G8.5 photomask, it is required to minimize bending deformation of the large-size material during photoresist particle inspection to avoid damage such as top scratches and abrasions on the back of the photomask. Therefore, the following design was implemented: Figure 2 and Figure 3 The mask plate carrier unit 13 is shown.

[0021] The mask support unit 13 is used to support and drive the mask 11 to move in the Y direction. The mask support unit 13 includes a support platform 21 and a drive motor 20. A Y-axis movable platform 22 is slidably connected to the support platform 21. Pin column lifting channels 19 are evenly distributed inside the support platform 21 and the Y-axis movable platform 22. Pin columns 17 (with a flexible surface) are provided inside the pin column lifting channels 19 to provide temporary support when loading the mask 11. Multiple air float nozzles 16 are evenly distributed on the Y-axis movable platform 22 to form an air float nozzle array, which is used to form an air film between the mask 11 and the Y-axis movable platform 22. A flexible clamp 14 is fixed to the edge of the Y-axis movable platform 22 to prevent the mask 11 from drifting horizontally on the air film. A lead screw 18 is fixed on the drive shaft of the drive motor 20, and the Y-axis moving platform 22 is threadedly connected to the lead screw 18.

[0022] In the above technical solution, the air film formed by the air flotation nozzle is a micron-thick air film that lifts the mask 11 as a whole, counteracts the bending deformation caused by gravity, and achieves completely non-contact support, fundamentally eliminating the occurrence of damage or scratches on the back of the mask.

[0023] Meanwhile, in order to prevent the mask 11 from drifting horizontally under the air-bearing support, a flexible clamp 14 is fixed on the edge of the Y-direction moving platform 22. The flexible clamp 14 only contacts the chamfered edge or side of the mask 11, and does not contact the back or graphic area.

[0024] In the technical solution of this application, the loading process of mask 11 includes: When mask 11 is not loaded, pin 17 is in the raised state; The external robotic arm slowly places the mask 11 onto the pin 17. After the robotic arm moves away, the pin 17 slowly descends with the mask 11. When the pin 17 descends to the specified height, the air flotation nozzle 16 sprays compressed air to form an air film between the mask 11 and the Y-axis moving stage 22. When the mask 11 and the Y-axis moving stage 22 reach a specified distance, the flexible clamp 14 begins to clamp the side of the mask to prevent the mask 11 from drifting horizontally on the air film. Pin 17 descends into the support platform 21 to prevent movement restriction on the Y-axis moving platform 22.

[0025] III. Photodetector Array The photodetector array 8 uses a high-sensitivity CMOS camera array. The photodetector array 8 and the X-direction cross bridge 15 are connected by an air-float filling of the contact gap (which can avoid hard mechanical contact during movement and reduce vibration) so as to move smoothly along the X direction.

[0026] IV. Signal Processing Unit The functions of signal processing unit 9 include: Data acquisition and synchronization control: Receives interference images and maintains real-time communication with the light source controller, galvanometer controller, and mask support unit controller to ensure that the interference data of each pixel corresponds precisely to its spatial coordinates; Phase calculation and 3D reconstruction: Extract phase information from the interference light intensity distribution, calculate the absolute height, and reconstruct the 3D morphology of the mask surface; Particle identification: Based on the three-dimensional morphology of the photomask surface, the height, size and position of photoresist particles are identified, and the type of particles is determined according to their three-dimensional morphological characteristics (such as residual adhesive, dust, adhesive surface protrusion, adhesive surface damage, etc.). Data storage and report output: Save interference images, particle identification results and particle distribution maps, generate detection reports, and store them in association with the mask ID; System calibration and error compensation: The test report is sent to the back-end particle cleaning unit, and the system self-calibration is performed regularly to compensate for measurement errors caused by environmental vibration, temperature drift and optical system distortion.

[0027] This invention employs the principle of dual-wavelength interferometry to solve the phase ambiguity problem in single-wavelength interferometry, thereby achieving absolute measurement of the height (or thickness) of photoresist particles.

[0028] Specifically, signal processing unit 9 extracts phase information from the interference light intensity distribution, calculates the absolute height, and reconstructs the three-dimensional morphology of the mask surface, including: S11, Equivalent Wavelength Combination: The laser wavelengths emitted by the first laser source 1 and the second laser source 2 are respectively , ,and and Similarly, an equivalent wavelength can be synthesized using two-wavelength interference. : ; equivalent wavelength Much larger and equivalent wavelength The corresponding phase change range covers the maximum optical path difference that may be caused by the height of the photoresist particles, thus solving the phase ambiguity problem and realizing unambiguous measurement of the height of the photoresist particles; S12, Height Calculation: Collect data separately. , The corresponding interference signals are used to calculate their respective envelope phases. , The composite phase is calculated using the phase difference method. Then the height distribution h(x,y) on the mask surface is: ; The algorithm described above can accurately reconstruct the three-dimensional morphology of the mask surface and accurately determine the photoresist particles based on the height threshold and lateral dimension.

[0029] Based on the aforementioned device for detecting photoresist particles on the surface of a photomask, this invention also discloses a method for detecting photoresist particles on the surface of a photomask, such as... Figure 6 As shown, it includes the following steps: S1. The photodetector array 8 is aligned with the mask surface. While reciprocating along the X-axis transverse bridge 15, it performs optical detection on the photoresist particles on the mask surface. The area on the mask surface detected in one X-axis movement is recorded as the X-axis detection scanning area (e.g., ...). Figure 4 (as shown) S2. After the photodetector array 8 completes one X-axis movement along the X-axis transverse bridge 15, the Y-axis moving platform 22 moves one step along the Y-axis under the action of the drive motor 20 and the lead screw 18 (e.g., Figure 4 As shown), to avoid missed scans, there is a scanning overlap area between adjacent X-axis detection scanning areas (e.g. Figure 5 (as shown) S3. Repeat S1 and S2 until the photoresist particle detection of the entire mask 11 is completed. S4. The photodetector array 8 receives the interference signal, converts the interference light intensity distribution into an interference image, and sends it to the signal processing unit 9 for processing. S5 and signal processing unit 9 extract phase information from the interference light intensity distribution, calculate the absolute height, reconstruct the three-dimensional morphology of the mask surface, identify the height, size and position of photoresist particles based on the three-dimensional morphology of the mask surface, and determine the type of the particles (such as residual adhesive, dust, adhesive surface protrusion, adhesive surface damage, etc.) according to the three-dimensional morphological characteristics. They save the interference image, particle identification results and particle distribution map, generate a detection report, and send the detection report to the back-end particle cleaning unit for processing.

[0030] Specifically, signal processing unit 9 extracts phase information from the interference light intensity distribution, calculates the absolute height, and reconstructs the three-dimensional morphology of the mask surface, including: S11, Equivalent Wavelength Combination: The laser wavelengths emitted by the first laser source 1 and the second laser source 2 are respectively , ,and and Similarly, an equivalent wavelength can be synthesized using two-wavelength interference. : ; equivalent wavelength Much larger and equivalent wavelength The corresponding phase change range covers the maximum optical path difference that may be caused by the height of the photoresist particles, thus solving the phase ambiguity problem and realizing unambiguous measurement of the height of the photoresist particles; S12, Height Calculation: Collect data separately. , The corresponding interference signals are used to calculate their respective envelope phases. , The composite phase is calculated using the phase difference method. Then the height distribution h(x,y) on the mask surface is: ; The algorithm described above can accurately reconstruct the three-dimensional morphology of the mask surface and accurately determine the photoresist particles based on the height threshold and lateral dimension.

[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for detecting photoresist particles on the surface of a photomask, characterized in that: Includes the following components: A dual-wavelength laser source that emits two laser beams of different wavelengths; Beam combiner (3) combines two laser beams into one beam; The two-dimensional scanning galvanometer (4) can be rapidly deflected around the X-axis and Y-axis to realize two-dimensional scanning of the combined beam on the mask surface; The beam splitter (5) splits the combined beam into two paths, one being the reference beam and the other the measurement beam. The reference light reflector (6) reflects the reference beam back to the beam splitter (5) along the original path. The measuring objective (7) focuses the measuring beam and incident it onto the photoresist layer (10) on the surface of the mask (11). The measuring beam carries the surface information and returns to the beam splitter (5), interfering with the reference beam. The photodetector array (8) receives the interference signal and converts the interference light intensity distribution into an interference image, which is then sent to the signal processing unit (9) for processing. The signal processing unit (9) receives the interference image, reconstructs the three-dimensional morphology of the mask surface, automatically identifies photoresist particles, generates a test report, and periodically performs system self-calibration.

2. The device for detecting photoresist particles on the surface of a photomask according to claim 1, characterized in that: The dual-wavelength laser source includes a first laser source (1) and a second laser source (2). The first laser source (1) uses a He-Ne laser with a wavelength of 632nm, and the second laser source (2) uses a semiconductor laser with a wavelength of 660nm.

3. The device for detecting photoresist particles on the surface of a photomask according to claim 1, characterized in that: It also includes a mask support unit (13) for carrying and driving the mask (11) to move in the Y direction, the mask support unit (13) including a support platform (21) and a drive motor (20). A Y-axis moving platform (22) is slidably connected to the support platform (21). Pin column lifting channels (19) are evenly distributed inside the support platform (21) and the Y-axis moving platform (22). Pin columns (17) that serve as temporary supports when loading the mask (11) are provided inside the pin column lifting channel (19). Multiple air-bearing nozzles (16) are evenly distributed on the Y-axis moving platform (22) to form an air-bearing nozzle array, which is used to form an air film between the mask (11) and the Y-axis moving platform (22). A flexible clamp (14) is fixed on the edge of the Y-axis moving platform (22) to prevent the mask (11) from horizontally drifting on the air film. A lead screw (18) is fixed on the drive shaft of the drive motor (20), and the Y-axis moving platform (22) is threadedly connected to the lead screw (18).

4. The device for detecting photoresist particles on the surface of a photomask according to claim 3, characterized in that: The loading process of the mask (11) includes: When the mask (11) is not loaded, the pin (17) is in the raised state; The external robotic arm slowly places the mask (11) onto the pin (17). After the robotic arm moves away, the pin (17) slowly descends with the mask (11). When the pin column (17) descends to the specified height, the air flotation nozzle (16) sprays compressed air to form an air film between the mask plate (11) and the Y-axis moving stage (22); When the mask (11) and the Y-axis moving stage (22) reach a specified distance, the flexible clamp (14) begins to clamp the side of the mask to prevent the mask (11) from drifting horizontally on the air film. The pin (17) descends into the bearing platform (21) to prevent movement restriction on the Y-axis moving platform (22).

5. The device for detecting photoresist particles on the surface of a photomask according to claim 1, characterized in that: The photodetector array (8) is a high-sensitivity CMOS camera array. The photodetector array (8) and the X-direction cross bridge (15) are connected by an air-float filling contact gap to move along the X-direction.

6. The device for detecting photoresist particles on the surface of a photomask according to claim 1, characterized in that: The functions of the signal processing unit (9) include: Data acquisition and synchronization control: Receives interference images and maintains real-time communication with the light source controller, galvanometer controller, and mask support unit controller to ensure that the interference data of each pixel corresponds precisely to its spatial coordinates; Phase calculation and 3D reconstruction: Extract phase information from the interference light intensity distribution, calculate the absolute height, and reconstruct the 3D morphology of the mask surface; Particle identification: Based on the three-dimensional morphology of the mask surface, the height, size and position of photoresist particles are identified, and the type is determined according to the three-dimensional morphological characteristics. Data storage and report output: Save interference images, particle identification results and particle distribution maps, generate detection reports, and store them in association with the mask ID; System calibration and error compensation: The test report is sent to the back-end particle cleaning unit, and the system self-calibration is performed regularly to compensate for measurement errors caused by environmental vibration, temperature drift and optical system distortion.

7. The device for detecting photoresist particles on the surface of a photomask according to claim 6, characterized in that: The signal processing unit (9) extracts phase information from the interference light intensity distribution, calculates the absolute height, and reconstructs the three-dimensional morphology of the mask surface, including: S11, Equivalent Wavelength Synthesis: The laser wavelengths emitted by the first laser source (1) and the second laser source (2) are respectively , ,and and Similarly, an equivalent wavelength can be synthesized using two-wavelength interference. : ； equivalent wavelength Much larger and equivalent wavelength The corresponding phase change range covers the maximum optical path difference that may be caused by the height of the photoresist particles, thus solving the phase ambiguity problem and realizing unambiguous measurement of the height of the photoresist particles; S12, Height Calculation: Collect data separately. , The corresponding interference signals are used to calculate their respective envelope phases. , The composite phase is calculated using the phase difference method. Then the height distribution h(x,y) on the mask surface is: ； The algorithm described above can accurately reconstruct the three-dimensional morphology of the mask surface and accurately determine the photoresist particles based on the height threshold and lateral dimension.

8. A method for detecting photoresist particles on the surface of a photomask, applicable to the photoresist particle detection device on the surface of a photomask as described in claim 1, characterized in that: Includes the following steps: S1. The photodetector array (8) is aligned with the mask surface. While moving back and forth along the X-direction transverse bridge (15), it performs optical detection on the photoresist particles on the mask surface. The area on the mask surface detected by one X-direction movement is recorded as the X-direction detection scanning area. S2. After the photodetector array (8) completes one X-direction movement along the X-direction transverse bridge (15), the Y-direction moving stage (22) moves one step along the Y-direction under the action of the drive motor (20) and the lead screw (18). In order to avoid missed scans, there is a scanning overlap area between adjacent X-direction detection scanning areas. S3. Repeat S1 and S2 until the photoresist particle detection of the entire mask (11) is completed. S4. The photodetector array (8) receives the interference signal and converts the interference light intensity distribution into an interference image, which is then sent to the signal processing unit (9) for processing. S5, Signal processing unit (9) extracts phase information from the interference light intensity distribution, calculates the absolute height, reconstructs the three-dimensional morphology of the mask surface, identifies the height, size and position of photoresist particles based on the three-dimensional morphology of the mask surface, and determines the type of the particles according to the three-dimensional morphological characteristics, saves the interference image, particle identification results and particle distribution map, generates a detection report, and sends the detection report to the back-end particle cleaning unit for processing.

9. The method for detecting photoresist particles on the surface of a photomask according to claim 8, characterized in that: The signal processing unit (9) extracts phase information from the interference light intensity distribution, calculates the absolute height, and reconstructs the three-dimensional morphology of the mask surface, including: S11, Equivalent Wavelength Synthesis: The laser wavelengths emitted by the first laser source (1) and the second laser source (2) are respectively , ,and and Similarly, an equivalent wavelength can be synthesized using two-wavelength interference. : ； equivalent wavelength Much larger and equivalent wavelength The corresponding phase change range covers the maximum optical path difference that may be caused by the height of the photoresist particles, thus solving the phase ambiguity problem and realizing unambiguous measurement of the height of the photoresist particles; S12, Height Calculation: Collect data separately. , The corresponding interference signals are used to calculate their respective envelope phases. , The composite phase is calculated using the phase difference method. Then the height distribution h(x,y) on the mask surface is: ； The algorithm described above can accurately reconstruct the three-dimensional morphology of the mask surface and accurately determine the photoresist particles based on the height threshold and lateral dimension.

Images