Dual-channel detection system based on radial gradient graded ground glass and control method

Abstract

The application provides a double-channel detection system based on radial gradient gradual frosted glass and a control method, relates to the fields of semiconductor manufacturing and precision measurement technology, and comprises a tunable laser light source, a beam splitter, a beam steering module, a multi-axis motion platform, radial gradient gradual frosted glass, a beam position monitoring module, a double-channel power monitoring module, an imaging and spectrum detection module and a central control module, wherein the tunable laser light source and the beam splitter are located on the same optical axis, the beam steering module is arranged on the exit side of the beam splitter, the multi-axis motion platform is connected with the radial gradient gradual frosted glass, the beam position monitoring module is connected with the radial gradient gradual frosted glass, the double-channel power monitoring module and the imaging and spectrum detection module are located on the light exit paths of the first decoherence light beam and the second decoherence light beam, and the central control module is electrically connected with the beam steering module, the multi-axis motion platform, the beam position monitoring module, the double-channel power monitoring module and the imaging and spectrum detection module.

Description

Technical Field

[0001] This invention relates to the fields of semiconductor manufacturing and precision measurement technology, and in particular to a dual-channel detection system and control method based on radial gradient frosted glass. Background Technology

[0002] Optical inspection of semiconductor devices refers to acquiring key information such as the device's geometry, surface condition, and material properties through optical means without contacting the device under test. It is a crucial metrology step ensuring the yield and reliability of advanced packaging and manufacturing processes. As chip structures become increasingly complex and device dimensions continue to shrink, the demand for rapid, high-precision inspection of the front and back, and even multiple sides, of wafers and chips on production lines is growing, placing higher demands on the stability, repeatability, and automation level of inspection systems. Dual-channel optical inspection technology, through the simultaneous illumination and acquisition of two beams of light, can obtain more information per unit time, making it particularly suitable for the simultaneous measurement of both sides of a device and possessing significant application value in industrial inspection.

[0003] Chinese Patent CN109507117B discloses a micro-nano imaging detection experimental device based on photoacoustic beam shaping, including a dye laser source, a forward scanning probe based on nonlinear photonic crystal beam shaping, a first reflecting mirror, a three-dimensional electric platform, a beam expander, a frosted glass, a coupling fluid, a lifting stage, a sample cell, a transducer, a backward tracking probe with embedded wavefront control, a lock-in amplifier, a data acquisition unit, and a computer. This experimental device can effectively operate in a label-free detection mode with complex photoacoustic field modulation and adaptive wavefront control. The computer is connected to the dye laser source, the forward scanning probe with beam shaping, the three-dimensional electric platform, the transducer, the forward scanning probe with beam shaping, and the lock-in amplifier via signal lines. However, the above solution relies solely on a fixed optical path and passive optical components to maintain long-term stability of beam power and spatial position, making it difficult to compensate for light source output fluctuations and optical path drift in a timely manner, resulting in insufficient measurement consistency and reliability of the device in continuous operation scenarios. Therefore, it is essential to provide a dual-channel detection system and control method based on radially gradient frosted glass to improve the measurement consistency and reliability of optical device detection. Summary of the Invention

[0004] In view of this, the present invention proposes a dual-channel detection system and control method based on radial gradient frosted glass to improve the measurement consistency and reliability of optical device detection.

[0005] This invention provides a dual-channel detection system based on radially gradient ground glass, comprising a tunable laser source, a beam splitter, a beam steering module, a multi-axis motion platform, radially gradient ground glass, a beam position monitoring module, a dual-channel power monitoring module, an imaging and spectral detection module, and a central control module. The tunable laser source and the beam splitter are located on the same optical axis. The beam splitter is used to split the detection laser emitted by the tunable laser source into a first channel beam and a second channel beam. The beam steering module is disposed on the exit side of the beam splitter; the beam steering module is used to adjust the propagation direction of the second channel beam. The multi-axis motion platform is connected to the radial gradient gradient frosted glass and is used to adjust the position and orientation of the radial gradient gradient frosted glass relative to the first channel beam and the second channel beam. The radial gradient gradient frosted glass is used to perform scattering decoherence processing on the first channel beam and the second channel beam respectively to obtain a first decoherent beam and a second decoherent beam. The beam position monitoring module is connected to the radially gradient ground glass. The beam position monitoring module is used to acquire the illumination positions of the first decoherent beam and the second decoherent beam on the radially gradient ground glass, and output a first electrical signal corresponding to the illumination position. The dual-channel power monitoring module and the imaging and spectral detection module are both located on the light output paths of the first decoherent beam and the second decoherent beam. The dual-channel power monitoring module is used to monitor the optical power of the first decoherent beam and the second decoherent beam and output a second electrical signal corresponding to the optical power. The imaging and spectral detection module is used to perform imaging and / or optical measurement on the sample irradiated by the first decoherent beam and the second decoherent beam to obtain a third electrical signal. The central control module is electrically connected to the beam steering module, the multi-axis motion platform, the beam position monitoring module, the dual-channel power monitoring module, and the imaging and spectral detection module. The central control module is used to receive the first electrical signal, the second electrical signal, and the third electrical signal, and to send control commands to the multi-axis motion platform and the beam steering module to adjust the attitude of the radial gradient ground glass to complete beam alignment.

[0006] Based on the above technical solutions, preferably, the surface roughness of the radially gradient frosted glass changes continuously or in a stepwise manner along the radial direction, and the radially gradient frosted glass forms multiple rings with different optical scattering characteristics from the central smooth region to the edge rough region.

[0007] Based on the above technical solutions, preferably, the dual-channel power monitoring module includes a first power monitoring unit, a first beam splitter, a second beam splitter, and a second power monitoring unit, wherein, The first beam splitter and the beam splitter are located on the same optical axis. The first beam splitter is used to reflect part of the first decoherent beam to the first power monitoring unit and transmit the remaining first decoherent beam to the imaging and spectral detection module. The first power monitoring unit is used to receive the first decoherent beam and detect the optical power of the first decoherent beam. The second beam splitter and the beam steering module are located on the same optical axis. The second beam splitter is used to reflect part of the second decoherent beam to the second power monitoring unit and transmit the remaining second decoherent beam to the imaging and spectral detection module. The second power monitoring unit is used to receive the second decoherent beam and detect the optical power of the second decoherent beam.

[0008] More preferably, the imaging and spectral detection module includes a first imaging detection unit, a first detection region, a second imaging detection unit, and a second detection region, wherein, The first beam splitter, the beam splitter, and the first detection area are located on the same optical axis. The first imaging detection unit images the sample in the first detection area through the first decoherent beam and generates a spectral signal corresponding to the first decoherent beam. The second beam splitter, the beam steering module, and the second detection area are located on the same optical axis. The second imaging detection unit images the sample in the second detection area through the second decoherent beam and generates a spectral signal corresponding to the second decoherent beam.

[0009] More preferably, the central control module calculates the real-time illumination coordinates and corresponding polar coordinate parameters of the first channel beam and the second channel beam on the radially gradient frosted glass based on the first electrical signal output by the beam position monitoring module, compares the real-time illumination coordinates with a preset target position to obtain the position drift, and calculates the optical power ratio between the first decoherent beam and the second decoherent beam based on the second electrical signal output by the dual-channel power monitoring module, and compares the optical power ratio with the target power ratio to obtain the power deviation.

[0010] More preferably, when the power deviation is greater than a preset deviation threshold, the central control module controls the multi-axis motion platform to adjust the position of the radial gradient frosted glass, so that the irradiation position of the first channel beam and / or the second channel beam moves between rings of different roughness, thereby increasing or decreasing the scattering attenuation of the corresponding beam.

[0011] More preferably, when the position drift is greater than a preset drift threshold, the central control module controls the beam steering module, the first beam splitter, and the second beam splitter to reverse the incident angle of the first channel beam and / or the second channel beam, so as to bring the spot positions of the first channel beam and the second channel beam back to the preset target point.

[0012] More preferably, the central control module stores a parameter database corresponding to the sample to be tested. The parameter database stores roughness ring parameters and frosted glass rotation speed parameters corresponding to different sample types. The roughness ring parameters include the radial position range of the ring, the target optical power ratio, and the target speckle suppression level.

[0013] More preferably, when the first detection area and the second detection area load the sample to be tested, they retrieve the corresponding roughness ring parameters and frosted glass rotation speed parameters from the parameter database according to the sample to be tested, so as to drive the multi-axis motion platform to move the radial gradient gradient frosted glass to the corresponding ring position, and set the rotation speed of the radial gradient gradient frosted glass to obtain the power distribution result for the sample to be tested.

[0014] A second aspect of this application provides a control method for a dual-channel detection system based on radially gradient ground glass, the control method comprising: A tunable laser source is controlled to emit a detection laser, and the detection laser is split into a first channel beam and a second channel beam by a beam splitter. The propagation direction of the second channel beam is adjusted using a beam steering module, so that the first channel beam and the second channel beam are incident on the radially gradient frosted glass along a predetermined optical path; The multi-axis motion platform is driven to adjust the position and orientation of the radial gradient gradient frosted glass relative to the first channel beam and the second channel beam, so that the first channel beam and the second channel beam undergo scattering and decoherence processing in the radial gradient gradient frosted glass, respectively, to obtain the first decoherent beam and the second decoherent beam. The beam position monitoring module obtains the irradiation positions of the first and second decoherent beams on the radially gradient ground glass, outputs a first electrical signal corresponding to the irradiation position, and detects the optical power of the first and second decoherent beams according to the dual-channel power monitoring module, and outputs a second electrical signal corresponding to the optical power. In the imaging and spectral detection module, the first and second decoherent beams are used to image and / or perform optical measurements on the sample to obtain a third electrical signal. The central control module receives the first electrical signal, the second electrical signal, and the third electrical signal, and sends control commands to the multi-axis motion platform and the beam steering module to adjust the posture of the radial gradient frosted glass and / or the propagation direction of the second channel beam in real time to complete the beam alignment.

[0015] The dual-channel detection system and control method based on radial gradient frosted glass provided by this invention have the following advantages over the prior art: (1) By using radially gradient frosted glass to scatter and decoherentize the two beams, coherence spots and interference fringes can be effectively suppressed, improving imaging quality and the signal-to-noise ratio and accuracy of spectral measurements. The beam position monitoring module and the dual-channel power monitoring module monitor the illumination position and optical power of the two decoherent beams in real time and feed them back to the central control module, enabling the system to achieve adaptive compensation in terms of position and power, ensuring the consistency and comparability of the detection conditions of the two channels. At the same time, the imaging and spectral detection modules can simultaneously or switchably perform imaging and optical measurements on the sample, and can complete the acquisition of structural and spectral information on the same platform, reducing equipment redundancy, improving system integration and application flexibility. The multi-axis motion platform and radial gradient design enable the frosted glass to achieve optimized scattering characteristics for beams with different incident angles and spatial positions. It can be adaptively adjusted according to the actual sample, spot size and working distance, thereby improving the measurement consistency and reliability of optical device detection.

[0016] (2) By continuously or stepwise changing the surface roughness in the radial direction, multiple rings with different scattering intensities and scattering angles are formed in the radial direction. This allows the beam to move between different rings or cover different radii, so that the degree of decoherence, the uniformity of the light spot and the scattering angle can be selected and adjusted to meet different imaging and spectral detection requirements. At the same time, the smooth central region provides weaker scattering, which can suppress some coherent spots while ensuring resolution and imaging details. The rough edge region provides stronger scattering, which is beneficial to further weaken coherence, homogenize the light intensity distribution and reduce interference fringes and spot noise, thereby improving the uniformity of sample illumination and the signal-to-noise ratio and stability of the spectral signal. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1A schematic diagram of the framework of the dual-channel detection system based on radial gradient ground glass provided by the present invention; Figure 2 This is a schematic diagram of the structure of the radial gradient frosted glass provided by the present invention.

[0019] Explanation of reference numerals in the attached figures: 1. Tunable laser source; 2. Beam splitter; 3. Beam steering module; 4. Multi-axis motion platform; 5. Radial gradient ground glass; 6. Beam position monitoring module; 7. Dual-channel power monitoring module; 71. First power monitoring unit; 72. First beam splitter; 73. Second beam splitter; 74. Second power monitoring unit; 8. Imaging and spectral detection module; 81. First imaging detection unit; 82. First detection area; 83. Second imaging detection unit; 84. Second detection area; 9. Central control module. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0022] refer to Figure 1 This invention provides a dual-channel detection system based on radially gradient ground glass, comprising a tunable laser source 1, a beam splitter 2, a beam steering module 3, a multi-axis motion platform 4, radially gradient ground glass 5, a beam position monitoring module 6, a dual-channel power monitoring module 7, an imaging and spectral detection module 8, and a central control module 9. The tunable laser source 1 and the beam splitter 2 are located on the same optical axis. The beam splitter 2 is used to split the detection laser emitted by the tunable laser source 1 into a first channel beam and a second channel beam.

[0023] In this embodiment, as Figure 1 As shown, the tunable laser source 1 is used to output continuous or quasi-continuous laser light with adjustable wavelength and / or frequency. The emitted beam of the tunable laser source 1 is collimated and shaped before propagating along a predetermined optical path. A beam splitter 2 is fixedly installed at a predetermined position on the emitted optical path of the tunable laser source 1, with its beam splitting center coaxial with the emitted optical axis of the tunable laser source 1. This means that the tunable laser source 1 and the beam splitter 2 are located on the same optical axis, allowing the detection laser emitted by the tunable laser source 1 to be incident on the incident surface of the beam splitter 2 in a perpendicular or near-perpendicular manner. The beam splitter 2 can be a non-polarizing beam splitter, a polarizing beam splitter, or other equivalent beam splitting element, used to split the incident detection laser into a first channel beam and a second channel beam output along different propagation directions. The first channel beam is the transmitted light from the beam splitter 2, and the second channel beam is the reflected light from the beam splitter 2 (or vice versa). This provides two stable laser sources for subsequent dual-channel decoherence processing and imaging / spectral detection while maintaining the power utilization rate of the incident light.

[0024] The beam steering module 3 is located on the exit side of the beam splitter 2 and is used to adjust the propagation direction of the second channel beam.

[0025] The multi-axis motion platform 4 is connected to the radial gradient gradient frosted glass 5 and is used to adjust the position and orientation of the radial gradient gradient frosted glass 5 relative to the first channel beam and the second channel beam. The radial gradient gradient frosted glass 5 is used to perform scattering and decoherence processing on the first channel beam and the second channel beam respectively to obtain the first decoherence beam and the second decoherence beam.

[0026] In this embodiment, the multi-axis motion platform 4 can perform precise translation in the horizontal and vertical directions and can rotate at a small angle around at least two spatial axes, thereby realizing the position and attitude adjustment of the radial gradient frosted glass 5 in three-dimensional space.

[0027] The first and second channel beams are incident on the same working surface of the radially gradient frosted glass 5 along a predetermined optical path. By adjusting the translation of the multi-axis motion platform 4, the illumination positions of the two beams on the frosted glass surface fall within the target radial position range of the radial gradient region. By adjusting the pitch, deflection, and other angles of the platform, the two beams pass through the frosted glass at the desired incident angle, thereby controlling the position of the light spot behind the optical path and the beam overlap, and achieving precise spatial alignment of the two channel beams.

[0028] The radially gradient frosted glass 5 has a gradually changing scattering intensity distribution along the radial direction. Light beams incident at different radii will experience varying degrees of scattering and phase perturbation when passing through this frosted glass. The first and second channel beams undergo multiple scatterings and phase randomization within their respective regions. The originally highly spatially coherent laser beams are transformed into quasi-uniform, low-coherence extended light fields, forming the first and second decoherent beams. By adjusting the motion parameters of the multi-axis motion platform 4, the incident positions and path lengths of the two beams on the frosted glass can be changed, allowing the two decoherent beams to achieve the desired speckle suppression, spot size, and energy distribution.

[0029] like Figure 2 As shown, the surface roughness of the radially gradient frosted glass 5 changes continuously or in a stepwise manner along the radial direction. The radially gradient frosted glass 5 forms multiple rings with different optical scattering properties from the smooth central region to the rough edge region.

[0030] In this embodiment, by continuously or stepwise varying the surface roughness radially, multiple annular zones with different scattering intensities and scattering angles are formed radially. This allows the beam to be moved between different annular zones or cover different radii, enabling selectability and adjustment of the degree of decoherence, beam uniformity, and scattering angle to meet different imaging and spectral detection requirements. Simultaneously, the smooth central region provides weaker scattering, which can suppress some coherent spots while ensuring resolution and imaging detail; the rough edge region provides stronger scattering, which is beneficial for further weakening coherence, homogenizing the light intensity distribution, and reducing interference fringes and spot noise, thereby improving sample illumination uniformity and the signal-to-noise ratio and stability of the spectral signal. By changing the beam's illumination position on the radially gradient frosted glass 5 using the multi-axis motion platform 4, it is possible to quickly switch or combine different annular zones, achieving adaptive optimization under different sample types, working distances, and optical power conditions. This expands the system's applicability and improves the consistency and repeatability of detection results.

[0031] Furthermore, the working surface of the radially gradient frosted glass 5 is divided into multiple concentric annular regions along the radial direction with the rotation axis as the center, and the surface roughness Ra of each annular region increases monotonically from the inside to the outside. Each annular region can achieve different surface roughness levels through processes such as chemical etching, sandblasting, sputtering deposition, and then fine polishing, thereby forming multi-level scattering regions with different scattering intensities and scattering angle distributions on the same substrate.

[0032] The surface of the radially gradient frosted glass 5 has at least five functional rings formed radially in sequence. These five functional rings, from the inside out, are the first ring, the second ring, the third ring, the fourth ring, and the fifth ring. The arithmetic mean roughness Ra range of these five functional rings and their corresponding main application scenarios are as follows: The first ring is located outside the central smooth region, with Ra ranging from 0.05 to 0.15 μm. This ring provides weak scattering and high transmittance, making it suitable for weak signal detection, fine structural observation of extremely thin transparent films or low-absorption materials, and maintaining spatial resolution and contrast as much as possible while suppressing some speckle.

[0033] The Ra range of the second ring is 0.20–0.35 μm. This ring further weakens the spatial coherence of the laser while ensuring high imaging clarity, making it suitable for monitoring thin film processes such as low-reflectivity dielectric films, high-precision film thickness measurement, and photoresist, and helps to reduce the influence of interference fringes on the thickness inversion results.

[0034] The Ra range of the third ring is 0.45–0.75 μm. This ring provides moderate scattering and a relatively uniform illumination spot, making it suitable for routine wafer inspection, comprehensive measurements of multilayer film stacks, and other scenarios, achieving a balance between suppressing speckle noise and ensuring measurement throughput.

[0035] The Ra range of the fourth ring is 0.90–1.50 μm. This ring has strong scattering ability and a large scattering angle distribution, making it suitable for detection scenarios with high reflectivity metal layers and strong speckle suppression requirements, such as macroscopic appearance inspection of patterned wafers and defect detection in metal interconnect areas. It can significantly reduce stripes and bright spots caused by strong reflection and multiple interference.

[0036] The fifth ring is located on the outermost radial side, with an Ra range of 1.80–2.50 μm. This ring exhibits significant scattering attenuation of incident light and near-Lambertian outgoing characteristics, enabling strong light attenuation and highly uniform surface light source illumination. It is suitable for applications such as photovoltaic device detection, low-power illumination of highly reflective samples, and applications requiring strict control of the light power received by the sample.

[0037] During use, the central control module 9 can select the corresponding ring number based on the pre-stored process formula in the parameter database, combined with the type of sample to be tested, surface reflection characteristics, and target speckle suppression level. It then drives the multi-axis motion platform 4 to move the illumination position of the first channel beam and / or the second channel beam to the radial position range of the corresponding ring. For samples with high power or high reflectivity, the fourth or fifth ring with a larger outer roughness can be preferentially selected to obtain stronger scattering and power attenuation. For samples requiring high-resolution imaging or weak signal measurement, the first or second ring with a smaller inner roughness is preferred to balance resolution and speckle suppression effect.

[0038] Furthermore, for the same sample under test, multiple rings can be switched or adjacent rings can be combined for illumination depending on the different testing tasks. For example, on the same wafer, the third ring can be used for rapid macroscopic defect screening first, and then the first or second ring can be switched to perform high-resolution re-inspection of suspected defect areas. Through the above-mentioned multi-ring roughness gradation design, the radial gradient gradient frosted glass 5 can meet the needs of various applications such as weak signal detection, conventional wafer inspection, and high-reflectivity sample inspection on the same optical platform, further improving the adaptability and detection efficiency of the dual-channel inspection system.

[0039] The beam position monitoring module 6 is connected to the radial gradient ground glass 5. The beam position monitoring module 6 is used to obtain the irradiation positions of the first decoherent beam and the second decoherent beam on the radial gradient ground glass 5, and output a first electrical signal corresponding to the irradiation position.

[0040] The beam position monitoring module 6 includes any one of a position-sensitive detector (PSD), a four-quadrant detector, or a vision camera, used to acquire the spot image or position signal of the first channel beam and the second channel beam after passing through the radially gradient frosted glass 5.

[0041] The dual-channel power monitoring module 7 and the imaging and spectral detection module 8 are both located on the light output paths of the first and second decoherent beams. The dual-channel power monitoring module 7 is used to monitor the optical power of the first and second decoherent beams and output a second electrical signal corresponding to the optical power. The imaging and spectral detection module 8 is used to perform imaging and / or optical measurement on the sample irradiated by the first and second decoherent beams to obtain a third electrical signal.

[0042] In this embodiment, the dual-channel power monitoring module 7 includes a first power monitoring unit 71, a first beam splitter 72, a second beam splitter 73, and a second power monitoring unit 74, wherein... The first beam splitter 72 and the beam splitter 2 are located on the same optical axis. The first beam splitter 72 is used to reflect part of the first decoherent beam to the first power monitoring unit 71 and transmit the remaining first decoherent beam to the imaging and spectral detection module 8. The first power monitoring unit 71 is used to receive the first decoherent beam and detect the optical power of the first decoherent beam. The second beam splitter 73 and the beam steering module 3 are located on the same optical axis. The second beam splitter 73 is used to reflect part of the second decoherent beam to the second power monitoring unit 74 and transmit the remaining second decoherent beam to the imaging and spectral detection module 8. The second power monitoring unit 74 is used to receive the second decoherent beam and detect the optical power of the second decoherent beam.

[0043] In this embodiment, the imaging and spectral detection module 8 includes a first imaging detection unit 81, a first detection area 82, a second imaging detection unit 83, and a second detection area 84, wherein, The first beam splitter 72, the beam splitter 2, and the first detection area 82 are located on the same optical axis. The first imaging detection unit 81 images the sample in the first detection area 82 through the first decoherent beam and generates a spectral signal corresponding to the first decoherent beam. The second beam splitter 73, the beam steering module 3, and the second detection area 84 are located on the same optical axis. The second imaging detection unit 83 images the sample in the second detection area 84 through the second decoherent beam and generates a spectral signal corresponding to the second decoherent beam. The samples placed in the first detection area 82 and the second detection area 84 can be wafers and chips.

[0044] By using the first beam splitter 72 and the second beam splitter 73 to extract only portions of the first and second decoherent beams to the corresponding power monitoring units, online and independent monitoring of the optical power of the two beams is achieved. This ensures the stability and traceability of the illumination power without significantly affecting the imaging and spectral detection of the main optical path. The first beam splitter 72 is coaxial with the beam splitter 2, and the second beam splitter 73 is coaxial with the beam steering module 3, ensuring a strict correspondence between the power monitoring position and the imaging / spectral detection position, accurately reflecting the actual optical power incident on their respective detection areas. The first imaging detection unit 81 and the second imaging detection unit 83 respectively image the first detection area 82 and the second detection area 84 and generate spectral signals. This allows for simultaneous or rapid alternation of detection of two areas (such as wafer and chip, or different areas on the same wafer), improving detection throughput and system utilization. The first beam splitter 72 – beam splitter 2 – first detection area 82 and the second beam splitter 73 – beam steering module 3 – second detection area 84 are designed on the same optical axis to reduce optical aberrations and eccentricity errors, improve imaging clarity and spatial registration accuracy, and facilitate the precise positioning and comparison of defects, microstructures, etc.

[0045] Furthermore, both the dual-channel power monitoring module 7 and the imaging and spectral detection module 8 are arranged along the light exit paths of the first and second decoherent beams, and are sequentially arranged along the beam propagation direction. After exiting the radially gradient frosted glass 5, the first and second decoherent beams first enter the dual-channel power monitoring module 7. Within this module, a portion of the optical power is split off by the first beam splitter 72 and the second beam splitter 73, respectively, and guided to the first power monitoring unit 71 and the second power monitoring unit 74 for detection. The first power monitoring unit 71 and the second power monitoring unit 74 convert the real-time optical power of the first and second decoherent beams into a second electrical signal corresponding to the magnitude of the optical power, and output the second electrical signal to the central control module 9 for calculating the dual-channel optical power ratio and power deviation, thereby realizing real-time monitoring and feedback control of the dual-channel optical power.

[0046] The remaining first and second decoherent beams after passing through the dual-channel power monitoring module 7 continue to propagate along the predetermined optical path and are incident on the imaging and spectral detection module 8, forming an illumination spot at the sample position to irradiate the sample under test. The imaging and spectral detection module 8, through imaging detection units and optical detectors set on the two beam paths, acquires and separates the reflected light, transmitted light, and / or scattered light of the sample. On the one hand, it forms two-dimensional or three-dimensional imaging information of the sample surface; on the other hand, it obtains the spectral signals corresponding to the two decoherent beams. Finally, it outputs a third electrical signal corresponding to the sample imaging results and spectral characteristic parameters, which is sent to the central control module 9 for sample state discrimination, measurement result analysis, and correlation processing with beam position and optical power information.

[0047] The central control module 9 is electrically connected to the beam steering module 3, the multi-axis motion platform 4, the beam position monitoring module 6, the dual-channel power monitoring module 7, and the imaging and spectral detection module 8, respectively. The central control module 9 is used to receive the first electrical signal, the second electrical signal, and the third electrical signal, and to send control commands to the multi-axis motion platform 4 and the beam steering module 3 to adjust the attitude of the radial gradient gradient frosted glass 5 to complete the beam alignment.

[0048] In this embodiment, the central control module 9 stores a parameter database corresponding to the sample to be tested. The parameter database stores roughness ring parameters and frosted glass rotation speed parameters corresponding to different sample types. The roughness ring parameters include the radial position range of the ring, the target optical power ratio, and the target speckle suppression level.

[0049] Furthermore, the central control module 9 calculates the real-time illumination coordinates and corresponding polar coordinate parameters of the first channel beam and the second channel beam on the radially gradient ground glass 5 based on the first electrical signal output by the beam position monitoring module 6, and compares the real-time illumination coordinates with the preset target position to obtain the position drift amount. Based on the second electrical signal output by the dual-channel power monitoring module 7, it calculates the optical power ratio between the first decoherent beam and the second decoherent beam, and compares the optical power ratio with the target power ratio to obtain the power deviation.

[0050] When the power deviation exceeds the preset deviation threshold, the central control module 9 controls the multi-axis motion platform 4 to adjust the position of the radial gradient frosted glass 5, so that the irradiation position of the first channel beam and / or the second channel beam moves between rings of different roughness, thereby increasing or decreasing the scattering attenuation of the corresponding beam.

[0051] In one example, when the power ratio of the first decoherent beam to the second decoherent beam in the two channels deviates from the set value (e.g., 1:1), the lower power beam is moved to a smoother ring (with less attenuation) or the higher power beam is moved to a coarser ring (with greater attenuation) by moving the frosted glass, thus dynamically compensating for the light source attenuation and the change in the splitting ratio.

[0052] When the position drift exceeds the preset drift threshold, the central control module 9 controls the beam steering module 3, the first beam splitter 72, and the second beam splitter 73 to reverse the incident angle of the first channel beam and / or the second channel beam, so as to bring the spot positions of the first channel beam and the second channel beam back to the preset target point.

[0053] In one example, when the beam position is detected to deviate from the preset target point, it is quickly corrected by adjusting the angle of the incident mirror in the beam steering module 3, or by coordinating the adjustment of the position of the radial gradient ground glass 5 to compensate, so as to ensure the long-term alignment stability of the measurement optical path.

[0054] When the sample to be tested is loaded into the first detection area 82 and the second detection area 84, the corresponding roughness ring parameters and frosted glass rotation speed parameters are retrieved from the parameter database according to the sample to be tested. This drives the multi-axis motion platform 4 to move the radial gradient gradient frosted glass 5 to the corresponding ring position, and sets the rotation speed of the radial gradient gradient frosted glass 5 to obtain the power distribution result for the sample to be tested.

[0055] Furthermore, during the detection process, the beam position monitoring module 6 continuously or periodically acquires the real-time position coordinates and light intensity signals of the first channel beam and the second channel beam on the radially gradient frosted glass 5. These real-time position coordinates and light intensity signals are then transmitted to the central control module 9, enabling the central control module 9 to calculate the position drift, the current power ratio, and the deviation from the target power ratio. The above can be expressed as:

[0056] Δr A =r A -r A0 Dth A =θ A -θ A0 Rcurrent=P A / P B ΔR=Rcurrent-Rtarget in, Δr A This indicates the radial displacement of the first channel beam. r A This indicates the radial coordinates of the first channel beam illuminating the radially gradient frosted glass 5 at the current moment. r A0 This represents the radial coordinates of the first channel beam on the radial gradient frosted glass 5 in the initial state. Dth A This indicates the angular drift of the first channel beam in the azimuth direction. i A This indicates the current polar coordinates of the first channel beam on the radial gradient frosted glass 5. i A0 This represents the polar coordinates of the first channel beam on the radial gradient frosted glass 5 in the initial state. Rcurrent Indicates the current power ratio. P A This represents the optical power of the first decoherent beam. P B This indicates the optical power of the current second decoherent beam. Rtarget This indicates the pre-set target power ratio. ΔR This indicates the deviation between the current power ratio and the target power ratio.

[0057] In one example, the central control module makes decisions based on a preset strategy: If | ΔR Preset deviation threshold d If so, it is determined to be a power imbalance. Adjust the radial position of the radial gradient frosted glass 5. If ΔR If the power ratio is greater than 0 (i.e., the first channel beam is relatively too strong), then the multi-axis motion platform 4 is controlled to move along a specific direction, so that the first channel beam illuminates a rougher ring, i.e., increasing the attenuation of the first channel beam, or so that the second channel beam illuminates a smoother ring. Through closed-loop iteration, the current power ratio is adjusted. Rcurrent Return to target power ratio Rtarget nearby.

[0058] If the positional drift exceeds a preset drift threshold, it is determined to be beam alignment drift. The beam incident angle is adjusted first, and the fast-reflecting mirror in the beam steering module 3 is controlled to generate a reverse angular deflection, pushing the spot of the second channel beam back to the original target point. This method has a fast response speed and is used to correct high-frequency or sudden drifts. For slow, cumulative drifts, fine-tuning of the radial gradient frosted glass 5 position can also be used as an auxiliary method.

[0059] When a new sample is loaded or the measurement area is switched, the system can actively move the radial gradient frosted glass 5 to the corresponding optimal roughness ring zone according to the preset process formula and call the pre-stored experience data, and set an appropriate rotation speed.

[0060] After making the adjustments, monitor the new position and power values ​​again to verify the control effect. If the expected results are not achieved, repeat the adjustment process until the spot state stabilizes within the allowable tolerance range.

[0061] Under stable conditions, the system performs normal dual-channel detection tasks. Simultaneously, the central control module records drift data and effective compensation parameters at different times and under different environmental parameters (temperature), which are used to optimize the control process and achieve a certain degree of predictive compensation.

[0062] In this embodiment, the radially gradient frosted glass 5 is used to scatter and decohere the two beams, which can effectively suppress coherence spots and interference fringes, improve imaging quality and the signal-to-noise ratio and accuracy of spectral measurements. The beam position monitoring module 6 and the dual-channel power monitoring module 7 monitor the illumination position and optical power of the two decoherent beams in real time and feed them back to the central control module 9, enabling the system to achieve adaptive compensation in terms of position and power, ensuring the consistency and comparability of the detection conditions of the two channels. At the same time, the imaging and spectral detection module 8 can simultaneously or switchably perform imaging and optical measurements on the sample, and can complete the acquisition of structural and spectral information on the same platform, reducing equipment redundancy and improving system integration and application flexibility. The multi-axis motion platform 4 and the radial gradient design enable the frosted glass to achieve optimized scattering characteristics for beams with different incident angles and spatial positions. It can be adaptively adjusted according to the actual sample, spot size and working distance, thereby improving the measurement consistency and reliability of optical device detection.

[0063] Based on the above system, this application discloses a control method for a dual-channel detection system based on radial gradient ground glass. The control method includes: S1, control the tunable laser source 1 to emit a detection laser, and split the detection laser into a first channel beam and a second channel beam through the beam splitter 2; S2, the propagation direction of the second channel beam is adjusted by the beam steering module 3, so that the first channel beam and the second channel beam are incident on the radial gradient frosted glass 5 along the predetermined optical path. S3, drive the multi-axis motion platform 4 to adjust the position and orientation of the radial gradient gradient frosted glass 5 relative to the first channel beam and the second channel beam, so that the first channel beam and the second channel beam undergo scattering and decoherence processing in the radial gradient gradient frosted glass 5 respectively, and obtain the first decoherent beam and the second decoherent beam. S4, based on the beam position monitoring module 6, the irradiation positions of the first and second decoherent beams on the radially gradient ground glass 5 are obtained, and the first electrical signal corresponding to the irradiation position is output. The optical power of the first and second decoherent beams is detected by the dual-channel power monitoring module 7, and the second electrical signal corresponding to the optical power is output. The first and second decoherent beams are used to image and / or perform optical measurements on the sample in the imaging and spectral detection module 8 to obtain the third electrical signal. S5, the central control module 9 receives the first electrical signal, the second electrical signal and the third electrical signal, and sends control commands to the multi-axis motion platform 4 and the beam steering module 3 to adjust the posture of the radial gradient frosted glass 5 and / or the propagation direction of the second channel beam in real time to complete the beam alignment.

[0064] In this embodiment, after startup or sample change, the central control module 9 drives the multi-axis motion platform 4 to move the radially gradient gradient frosted glass 5 to a preset calibration position. Simultaneously, the beam steering module 3 controls the light to illuminate a specific target point (e.g., two points symmetrical about the rotation axis) on the radially gradient gradient frosted glass 5. The initial beam position and initial power value measured by the beam position monitoring module 6 are recorded, and the target power ratio is set. The specific target point refers to the ideal coordinate point on the radially gradient gradient frosted glass 5 when the frosted glass is in the calibration position, where the first channel beam and the second channel beam illuminate. This is the target position of the first channel beam and the second channel beam on a two-dimensional plane, typically in polar coordinates (…). r 0, i 0) indicates that the first channel beam and the second channel beam are symmetrical about the rotation axis of the radially gradient frosted glass 5 and are located at the center or optimal linear region of the position-sensitive detector (PSD).

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-channel detection system based on radially gradient frosted glass, characterized in that, The system includes a tunable laser source (1), a beam splitter (2), a beam steering module (3), a multi-axis motion platform (4), a radially gradient ground glass (5), a beam position monitoring module (6), a dual-channel power monitoring module (7), an imaging and spectral detection module (8), and a central control module (9). The tunable laser source (1) and the beam splitter (2) are located on the same optical axis. The beam splitter (2) is used to split the detection laser emitted by the tunable laser source (1) into a first channel beam and a second channel beam. The beam steering module (3) is disposed on the exit side of the beam splitter (2), and the beam steering module (3) is used to adjust the propagation direction of the second channel beam; The multi-axis motion platform (4) is connected to the radial gradient gradient frosted glass (5) and is used to adjust the position and orientation of the radial gradient gradient frosted glass (5) relative to the first channel beam and the second channel beam. The radial gradient gradient frosted glass (5) is used to perform scattering decoherence processing on the first channel beam and the second channel beam respectively to obtain the first decoherence beam and the second decoherence beam. The beam position monitoring module (6) is connected to the radial gradient ground glass (5). The beam position monitoring module (6) is used to acquire the irradiation positions of the first decoherent beam and the second decoherent beam on the radial gradient ground glass (5), and output a first electrical signal corresponding to the irradiation position. The dual-channel power monitoring module (7) and the imaging and spectral detection module (8) are both located on the light output paths of the first decoherent beam and the second decoherent beam. The dual-channel power monitoring module (7) is used to monitor the optical power of the first decoherent beam and the second decoherent beam, and output a second electrical signal corresponding to the optical power. The imaging and spectral detection module (8) is used to perform imaging and / or optical measurement on the sample irradiated by the first decoherent beam and the second decoherent beam to obtain a third electrical signal. The central control module (9) is electrically connected to the beam steering module (3), the multi-axis motion platform (4), the beam position monitoring module (6), the dual-channel power monitoring module (7), and the imaging and spectral detection module (8), respectively. The central control module (9) is used to receive the first electrical signal, the second electrical signal, and the third electrical signal, and to send control commands to the multi-axis motion platform (4) and the beam steering module (3) to adjust the attitude of the radial gradient ground glass (5) to complete the beam alignment.

2. The dual-channel detection system based on radially gradient frosted glass as described in claim 1, characterized in that, The surface roughness of the radially gradient frosted glass (5) changes continuously or in a stepwise manner along the radial direction, and the radially gradient frosted glass (5) forms multiple rings with different optical scattering characteristics from the central smooth region to the edge rough region.

3. The dual-channel detection system based on radially gradient frosted glass as described in claim 2, characterized in that, The dual-channel power monitoring module (7) includes a first power monitoring unit (71), a first beam splitter (72), a second beam splitter (73), and a second power monitoring unit (74), wherein, The first beam splitter (72) and the beam splitter (2) are located on the same optical axis. The first beam splitter (72) is used to reflect part of the first decoherent beam to the first power monitoring unit (71) and transmit the remaining first decoherent beam to the imaging and spectral detection module (8). The first power monitoring unit (71) is used to receive the first decoherent beam and detect the optical power of the first decoherent beam. The second beam splitter (73) and the beam steering module (3) are located on the same optical axis. The second beam splitter (73) is used to reflect part of the second decoherent beam to the second power monitoring unit (74) and transmit the remaining second decoherent beam to the imaging and spectral detection module (8). The second power monitoring unit (74) is used to receive the second decoherent beam and detect the optical power of the second decoherent beam.

4. The dual-channel detection system based on radially gradient frosted glass as described in claim 3, characterized in that, The imaging and spectral detection module (8) includes a first imaging detection unit (81), a first detection area (82), a second imaging detection unit (83), and a second detection area (84), wherein, The first beam splitter (72), the beam splitter (2), and the first detection area (82) are located on the same optical axis. The first imaging detection unit (81) images the sample in the first detection area (82) through the first decoherent beam and generates a spectral signal corresponding to the first decoherent beam. The second beam splitter (73), the beam steering module (3), and the second detection area (84) are located on the same optical axis. The second imaging detection unit (83) images the sample in the second detection area (84) through the second decoherent beam and generates a spectral signal corresponding to the second decoherent beam.

5. The dual-channel detection system based on radially gradient frosted glass as described in claim 3, characterized in that, The central control module (9) calculates the real-time illumination coordinates and corresponding polar coordinate parameters of the first channel beam and the second channel beam on the radial gradient ground glass (5) based on the first electrical signal output by the beam position monitoring module (6), and compares the real-time illumination coordinates with the preset target position to obtain the position drift amount. Based on the second electrical signal output by the dual-channel power monitoring module (7), it calculates the optical power ratio between the first decoherent beam and the second decoherent beam, and compares the optical power ratio with the target power ratio to obtain the power deviation.

6. The dual-channel detection system based on radially gradient frosted glass as described in claim 5, characterized in that, When the power deviation is greater than the preset deviation threshold, the central control module (9) controls the multi-axis motion platform (4) to adjust the position of the radial gradient frosted glass (5), so that the irradiation position of the first channel beam and / or the second channel beam moves between rings of different roughness, thereby increasing or decreasing the scattering attenuation of the corresponding beam.

7. The dual-channel detection system based on radially gradient frosted glass as described in claim 5, characterized in that, When the position drift is greater than the preset drift threshold, the central control module (9) controls the beam steering module (3), the first beam splitter (72) and the second beam splitter (73) to reverse the incident angle of the first channel beam and / or the second channel beam, so as to bring the spot positions of the first channel beam and the second channel beam back to the preset target point.

8. The dual-channel detection system based on radially gradient frosted glass as described in claim 4, characterized in that, The central control module (9) stores a parameter database corresponding to the sample to be tested. The parameter database stores roughness ring parameters and frosted glass rotation speed parameters corresponding to different sample types. The roughness ring parameters include the radial position range of the ring, the target optical power ratio, and the target speckle suppression level.

9. The dual-channel detection system based on radially gradient frosted glass as described in claim 8, characterized in that, When the first detection area (82) and the second detection area (84) load the sample to be tested, they call the corresponding roughness ring parameters and frosted glass rotation speed parameters from the parameter database according to the sample to be tested, so as to drive the multi-axis motion platform (4) to move the radial gradient gradient frosted glass (5) to the corresponding ring position, and set the rotation speed of the radial gradient gradient frosted glass (5) to obtain the power distribution result for the sample to be tested.

10. The control method for a dual-channel detection system based on radially gradient ground glass according to any one of claims 1 to 9, characterized in that, The control method includes: The tunable laser source (1) is controlled to emit a detection laser, and the detection laser is split into a first channel beam and a second channel beam by a beam splitter (2). The propagation direction of the second channel beam is adjusted by the beam steering module (3) so that the first channel beam and the second channel beam are incident on the radial gradient frosted glass (5) along a predetermined optical path; The multi-axis motion platform (4) is driven to adjust the position and orientation of the radial gradient gradient frosted glass (5) relative to the first channel beam and the second channel beam, so that the first channel beam and the second channel beam undergo scattering and decoherence processing in the radial gradient gradient frosted glass (5) respectively, and the first decoherence beam and the second decoherence beam are obtained. The beam position monitoring module (6) obtains the irradiation positions of the first decoherent beam and the second decoherent beam on the radial gradient ground glass (5), outputs a first electrical signal corresponding to the irradiation position, and detects the optical power of the first decoherent beam and the second decoherent beam according to the dual-channel power monitoring module (7), and outputs a second electrical signal corresponding to the optical power. The imaging and spectral detection module (8) uses the first decoherent beam and the second decoherent beam to perform imaging and / or optical measurement on the sample to obtain a third electrical signal. The central control module (9) receives the first electrical signal, the second electrical signal, and the third electrical signal, and sends control commands to the multi-axis motion platform (4) and the beam steering module (3) to adjust the posture of the radial gradient frosted glass (5) and / or the propagation direction of the second channel beam in real time to complete the beam alignment.

Images