A multi-layer film structure non-destructive testing device and method

Abstract

The application belongs to the technical field of thin film structure detection, and specifically discloses a multi-layer thin film structure nondestructive testing device and method. The device comprises a three-dimensional imaging detection module, a beam splitter, a broadband light source unit, a reference arm, a sample arm and a spectrum measurement unit arranged around the beam splitter according to a preset optical path. The beam splitter divides the linear light beam emitted by the broadband light source unit into two light beams. One light beam scans the multi-layer thin film structure to be detected through the sample arm to form signal light, and the other light beam forms reference light through the reference arm. The spectrum measurement unit collects the reference light and signal light of each sampling point of each layer of the multi-layer thin film structure to be detected in the scanning process of the sample arm, and generates corresponding interference spectrum information. The three-dimensional imaging detection module performs three-dimensional imaging detection on the multi-layer thin film structure to be detected based on the interference spectrum information of all the sampling points. The application can improve the spatial resolution of multi-layer thin film structure detection while achieving nondestructive testing effect.

Description

Technical Field

[0001] This application belongs to the field of thin film structure testing technology, and more specifically, relates to a non-destructive testing device and method for multilayer thin film structures. Background Technology

[0002] Multilayer thin film structures are important functional materials in modern industry, with applications spanning semiconductors, optoelectronics, new energy, biomedicine, and many other fields. With the continuous development of manufacturing processes, thin film devices are evolving towards higher performance, miniaturization, and multifunctionality, which places higher demands on the quality inspection of thin film structures.

[0003] Currently, among existing methods for detecting multilayer thin film structures, bright-field / dark-field microscopy is the most basic surface detection method. Although simple to operate, it can only observe the surface morphology of the thin film sample and cannot obtain information on the internal layer structure. Transmission electron microscopy (TEM) can observe the cross-sectional structure of the thin film, but it requires the preparation of extremely thin sample slices, which is destructive to the thin film sample. Ultrasonic detection can provide information about the internal structure of the sample, but it usually requires a coupling agent, which may contaminate or damage the thin film sample. Moreover, due to the wavelength limitation of sound waves, its spatial resolution is difficult to reach the micrometer level. The above methods play an important role in the field of thin film detection, but they all have certain limitations, especially in the non-destructive, high-resolution imaging of complex multilayer thin film structures, which still needs breakthroughs.

[0004] Therefore, how to better detect multilayer thin film structures has become a technical problem that the industry urgently needs to solve. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this application is to better realize the detection of multilayer thin film structures, and to solve the problems of low spatial resolution and damage to thin film samples in the existing multilayer thin film structure detection methods.

[0006] To achieve the above objectives, in a first aspect, this application provides a non-destructive testing device for multilayer thin film structures, comprising:

[0007] The system includes a three-dimensional imaging detection module, a beam splitter, and a broadband light source unit, a reference arm, a sample arm, and a spectral measurement unit arranged around the beam splitter according to a preset optical path. The three-dimensional imaging detection module is connected to the spectral measurement unit. The optical path formed by the broadband light source unit, the reference arm, and the sample arm is used to form a detection line beam on the surface of the multilayer thin film structure to be tested and on the reference surface in the reference arm.

[0008] The beam splitter is used to split the line beam emitted from the broadband light source unit into two line beams. One line beam is scanned by the sample arm to form signal light at each sampling point on the line beam, and the other line beam is formed by the reference arm to form reference light at each sampling point.

[0009] The spectral measurement unit is used to collect reference light and signal light at each sampling point on the line beam that detects each layer of the multilayer thin film structure under test during the scanning process of the sample arm, and generate corresponding interference spectral information.

[0010] The three-dimensional imaging detection module is used to perform three-dimensional imaging detection on the multilayer thin film structure under test based on the interference spectral information of all the acquired sampling points.

[0011] Optionally, the sample arm includes an objective lens arranged in sequence and a displacement lifting stage for fixing the multilayer thin film structure to be tested; the three-dimensional imaging detection module is connected to the displacement lifting stage;

[0012] The objective lens is used to acquire the signal light at the sampling points on the multilayer thin film structure under test.

[0013] The displacement lifting platform is used to adjust the scanning position of the multilayer thin film structure under the control of the three-dimensional imaging detection module, so as to generate signal light for each sampling point of each layer of the multilayer thin film structure under test.

[0014] Optionally, the spectral measurement unit includes a mirror group and an imaging spectrometer arranged sequentially;

[0015] The lens group is used to form a primary imaging optical path with the objective lens, so as to perform primary imaging at the entrance of the imaging spectrometer using the reference light and signal light at each of the sampling points;

[0016] The imaging spectrometer is used to acquire the interference spectral information corresponding to the primary imaging information transmitted from the mirror group.

[0017] Optionally, the imaging spectrometer includes an entrance slit, a collimating beam expander, a diffraction grating, a focusing lens group, and a two-dimensional array detector arranged sequentially.

[0018] The entrance slit is used to restrict stray light unrelated to the primary imaging information from entering the imaging spectrometer;

[0019] The collimator expander is used to collimate the reference light and signal light beams after passing through the entrance slit in the horizontal direction.

[0020] The diffraction grating is used to diffract and disperse the parallel beams of the reference light and the signal light transmitted from the collimator and expander.

[0021] The focusing lens group is used to focus light of different wavelengths transmitted from the diffraction grating onto the two-dimensional array detector to form a spectral image, and to compensate for the optical aberrations of the spectral image. The size of the spectral image is controlled by setting the effective focal length.

[0022] The two-dimensional array detector is used to acquire interference spectral information of the spectral image in multiple fields of view.

[0023] Optionally, the focusing lens group includes three double-film lenses arranged in sequence, wherein the optical power of the three double-film lenses is positive, negative, and positive in sequence.

[0024] Optionally, the reference arm includes an achromatic lens, an attenuator, and a reference mirror arranged sequentially; the position of the reference mirror is fixed.

[0025] The achromatic lens is used to form a focused reference line spot on the reference mirror, while compensating for the dispersion of the broadband light source.

[0026] The attenuator is used to attenuate the light intensity of the beam transmitted from the achromatic lens, thereby reducing the light intensity of the reference arm and matching the light intensity of the reference arm with that of the sample arm.

[0027] The reference mirror is used to reflect the light beam transmitted from the attenuator to form reference light for each sampling point of each layer of the multilayer thin film structure under test.

[0028] Optionally, the broadband light source unit includes a broadband light source, an optical fiber collimator, and a cylindrical lens arranged sequentially.

[0029] Broadband light sources are used to provide light sources within a target spectral range;

[0030] The fiber collimator is used to collimate and adjust the beam transmitted from the broadband light source.

[0031] The cylindrical lens is used to shape the collimated beam from the fiber collimator into a line beam, which is then transmitted to the beam splitter.

[0032] Secondly, this application provides a testing method applied to any of the aforementioned nondestructive testing devices for multilayer thin film structures, comprising:

[0033] Obtain the interference spectrum information of each sampling point of each layer of the multilayer thin film structure under test;

[0034] Three-dimensional tomographic image data with reflection intensity information is generated based on the interference spectral information of each of the sampling points;

[0035] Based on the three-dimensional tomographic image data of each sampling point, determine the reflection intensity scanning information corresponding to each sampling point;

[0036] The multilayer thin film structure under test is subjected to three-dimensional imaging detection using the reflection intensity scanning information corresponding to each sampling point.

[0037] Optionally, the multilayer thin film structure under test is a flexible printed circuit board, and the step of performing three-dimensional imaging detection on the multilayer thin film structure under test using the reflection intensity scanning information corresponding to each sampling point includes:

[0038] Based on the reflection intensity scanning information corresponding to each sampling point of the flexible printed circuit board, the maximum reflection intensity information and the second maximum reflection intensity information of the reflection intensity scanning information corresponding to each sampling point within the target depth range are determined.

[0039] Based on the maximum reflection intensity information and the second maximum reflection intensity information corresponding to each sampling point, the height map data corresponding to each sampling point is determined;

[0040] Using the height map data and spatial plane coordinates corresponding to each sampling point, a three-dimensional point cloud image of the flexible printed circuit board is generated to detect structural defects in each layer of the flexible printed circuit board.

[0041] Optionally, the multilayer thin-film structure to be tested is a display screen; the step of performing three-dimensional imaging detection on the multilayer thin-film structure to be tested using the reflection intensity scanning information corresponding to each sampling point includes:

[0042] Gaussian filtering is performed on the reflection intensity scanning information corresponding to each sampling point of each layer of the display screen to obtain each processed reflection intensity scanning information.

[0043] Based on the processed reflection intensity scanning information of each layer of the display screen, the interface positioning imaging result of each layer of the display screen is determined.

[0044] Based on the interface positioning imaging results, interface defects are detected in each layer of the display screen structure.

[0045] Overall, the technical solutions provided in this application have the following advantages compared with the prior art:

[0046] This application provides a non-destructive testing device and method for multilayer thin film structures. The device includes a three-dimensional imaging detection module, a beam splitter, and a broadband light source unit, a reference arm, a sample arm, and a spectral measurement unit arranged around the beam splitter. By employing spectral domain optical coherence tomography, the introduced broadband light source, sample arm, and reference arm perform linear scanning detection of the multilayer thin film structure under test. The reference arm can provide linear reference light with a wide spectral range, and the sample arm can scan the multilayer thin film structure under test to provide linear signal light with a wide spectral range. Combined with the spectral information of the interference signal between the reference light from the reference arm and the signal light from the sample arm, which is captured in real time by the spectral measurement unit, more detailed information about the interior of the multilayer thin film structure under test can be quickly captured, generating a high-quality three-dimensional image for detection. By performing a Fourier transform on the spectral domain interference signal to determine the reflection depth within the multilayer thin film structure sample, a spatial resolution at the micrometer level can be achieved. This achieves non-contact, rapid, and non-destructive testing while improving the spatial resolution of multilayer thin film structure detection. Attached Figure Description

[0047] Figure 1 This is one of the structural schematic diagrams of the non-destructive testing device for multilayer thin film structures provided in the embodiments of this application;

[0048] Figure 2 This is the second schematic diagram of the non-destructive testing device for multilayer thin film structures provided in the embodiments of this application;

[0049] Figure 3 This is a schematic diagram of the imaging spectrometer provided in the embodiments of this application;

[0050] Figure 4 This is a schematic flowchart of the detection method of the non-destructive testing device for multilayer thin film structures provided in the embodiments of this application;

[0051] Figure 5 (a) is a schematic diagram of the optical path of the device provided in this application scanning the metal pads on the FPC; (b) is a schematic diagram of the optical path of the device provided in this application scanning the solder mask layer on the FPC without embedded wires; (c) is a schematic diagram of the optical path of the device provided in this application scanning the solder mask layer on the FPC with embedded wires.

[0052] Figure 6 This is a schematic diagram of the structure of the electronic device provided in the embodiments of this application.

[0053] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0054] 1 is a three-dimensional imaging detection module; 2 is a beam splitter; 3 is a broadband light source unit; 31 is a broadband light source; 32 is an optical fiber collimator; 33 is a cylindrical lens; 4 is a reference arm; 41 is an achromatic lens; 42 is an attenuator; 43 is a reference mirror; 5 is a sample arm; 51 is an objective lens; 52 is a displacement stage; 521 is a displacement stage; 522 is a lifting stage; 6 is a spectral measurement unit; 61 is a lens group; 62 is an imaging spectrometer; 621 is an entrance slit; 622 is a collimating beam expander; 623 is a diffraction grating; 624 is a focusing lens group; 625 is a two-dimensional array detector; 6241 is a doublet lens; 6242 is a doublet lens; 6243 is a doublet lens. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0056] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0057] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0058] The embodiments of this application are described below with reference to the accompanying drawings.

[0059] Figure 1 This is one of the structural schematic diagrams of the non-destructive testing device for multilayer thin film structures provided in the embodiments of this application, such as... Figure 1 As shown, the device includes:

[0060] The three-dimensional imaging detection module 1, the beam splitter 2, and the broadband light source unit 3, the reference arm 4, the sample arm 5, and the spectral measurement unit 6 arranged around the beam splitter 2 according to the preset optical path; the three-dimensional imaging detection module 1 is connected to the spectral measurement unit 6; the optical path formed by the broadband light source unit, the reference arm and the sample arm is used to form a detection line beam on the surface of the multilayer thin film structure to be tested and the reference surface in the reference arm.

[0061] Beam splitter 2 is used to split the line beam emitted from broadband light source unit 3 into two line beams. One line beam is scanned by sample arm 5 to form signal light at each sampling point on the line beam, and the other line beam is formed by reference arm 4 to form reference light at each sampling point.

[0062] The spectral measurement unit 6 is used to collect reference light and signal light at each sampling point on the line beam of each layer of the multilayer thin film structure under test during the scanning process of the sample arm 5, and generate corresponding interference spectral information.

[0063] The three-dimensional imaging detection module 1 is used to perform three-dimensional imaging detection on the multilayer thin film structure under test based on the interference spectral information of all acquired sampling points.

[0064] Specifically, in the embodiments of this application, the broadband light source unit can provide a linear light source beam with a wide spectral range. The broadband light source unit, reference arm, sample arm, and spectral measurement unit are arranged around the beam splitter according to a pre-designed optical path, such that the light outlet of the broadband light source unit is aligned with one side of the beam splitter, the light inlets of the reference arm and sample arm are respectively aligned with the light outlets of the two split beams of the beam splitter, and the light inlet of the spectral measurement unit is aligned with the light outlet of the other side of the beam splitter. This allows the multi-wavelength line beam emitted by the broadband light source unit to be split into two line beams after passing through the beam splitter and transmitted to the reference arm and sample arm respectively.

[0065] Among them, the broadband light source unit, the reference arm, and the sample arm all have the function of beam shaping. The optical path formed by the three can form a detection line beam on the surface of the multilayer thin film structure under test and the reference surface in the reference arm.

[0066] One line beam can enter the sample arm, and by controlling the sample arm, the multi-wavelength beam can penetrate the multi-layer thin film structure under test to perform tomographic scanning on the multi-layer thin film structure under test. The scattering of the multi-layer thin film structure under test forms a wide-spectrum signal light at each sampling point on the line beam. The other line beam can enter the reference arm, and after reflection inside the reference arm, it forms a wide-spectrum reference light at each sampling point on the line beam.

[0067] In the embodiments of this application, the multilayer thin film structure to be tested refers to a multilayer thin film structure sample used for structural testing, which can be disposed in a sample arm. Specifically, it can include various transparent or semi-transparent multilayer thin film materials, such as flexible printed circuit boards (FPCs), liquid crystal displays (LCDs), etc.

[0068] Optionally, the reference arm and the sample arm can be designed to be symmetrical in structure. This can reduce the phase mismatch problem caused by the dispersion mismatch between the two arms, reduce the broadening of the signal in the spectral domain, and improve the accuracy of depth measurement in subsequent three-dimensional imaging detection of thin film structures.

[0069] Furthermore, the reference light and signal light at each sampling point on the line beam probing the multilayer thin film structure under test are acquired in real time, and the reference light and signal light at each sampling point on each probe line beam are coherently superimposed through the internal spectral measurement optical path structure to generate the interference spectral information corresponding to each sampling point, thereby capturing the detailed information inside the multilayer thin film structure under test.

[0070] Furthermore, by connecting to the three-dimensional imaging detection module, the spectral measurement unit can send the interference spectral information of each sampling point generated in real time to the three-dimensional imaging detection module for processing. The three-dimensional imaging detection module then performs three-dimensional imaging analysis and structural detection on each layer of the multilayer thin film structure under test.

[0071] It should be noted that, in addition to performing non-destructive testing of multilayer thin film structures, the device in this application embodiment can also measure the three-dimensional surface morphology of general objects.

[0072] The non-destructive testing device for multilayer thin film structures according to this application includes a three-dimensional imaging detection module, a beam splitter, and a broadband light source unit, a reference arm, a sample arm, and a spectral measurement unit disposed around the beam splitter. By employing spectral domain optical coherence tomography, the device uses the introduced broadband light source, sample arm, and reference arm to perform linear scanning detection on the multilayer thin film structure under test. The reference arm can provide linear reference light with a wide spectral range, and the sample arm can scan the multilayer thin film structure under test to provide linear signal light with a wide spectral range. Combined with the spectral information of the interference signal between the reference light from the reference arm and the signal light from the sample arm, which is captured in real time by the spectral measurement unit, more detailed information about the interior of the multilayer thin film structure under test can be quickly captured, generating a high-quality three-dimensional image for detection. By using interference to determine the depth of photon reflection within the multilayer thin film structure sample, a spatial resolution at the micrometer level can be achieved. This achieves a non-contact, rapid, and non-destructive testing effect while improving the spatial resolution of multilayer thin film structure detection.

[0073] Figure 2 This is the second schematic diagram of the non-destructive testing device for multilayer thin film structures provided in the embodiments of this application, as shown below. Figure 2 As shown, in the embodiments of this application, the broadband light source unit 3 may include a broadband light source 31, an optical fiber collimator 32 and a cylindrical lens 33 arranged sequentially.

[0074] The broadband light source 31 is used to provide a light source within the target spectral range;

[0075] Fiber optic collimator 32 is used to collimate and adjust the beam transmitted from the broadband light source;

[0076] Cylindrical lens 33 is used to shape the collimated beam from the fiber collimator into a line beam, so as to transmit the line beam to the beam splitter.

[0077] Specifically, in the embodiments of this application, the broadband light source unit can employ broadband light sources, such as SLED broadband light sources and ultra-wideband light sources, which have characteristics such as wide spectrum, weak temporal coherence, high power, and high efficiency, and are widely used in optical sensing, biomedical imaging, and other fields. Among them, the spectral bandwidth of SLED broadband light sources is typically in the target spectral range of 6nm to 100nm, while ultra-wideband light sources can achieve continuous spectral output exceeding 400nm.

[0078] In the embodiments of this application, the main function of the fiber optic collimator is to collimate and adjust the beam emitted from the broadband light source after transmission through the fiber optic cable, so that it can be received and processed more accurately by other optical elements.

[0079] In the embodiments of this application, the cylindrical lens has the characteristics of unidirectional focusing and divergence, and can focus parallel incident light rays onto a single line. Arranging a cylindrical lens behind a broadband light source can reshape the collimated beam from the fiber optic collimator into a line beam, thus meeting the requirements of the device for linear beam detection.

[0080] It should be noted that, in the embodiments of this application, the broadband light source unit can provide continuous low-coherence light within a certain wavelength range along the direction of the emitted beam from the broadband light source unit. In the vertical direction, the light (such as...) Figure 2 The light rays (shown as dashed lines in the diagram) are refracted by the lens in the broadband light source unit, thus changing their propagation direction and causing the light rays to focus. In the horizontal direction, the cylindrical lens does not cause the light rays to deflect because the refractive force of the cylindrical lens is mainly concentrated in the vertical direction where its radius of curvature is located, while there is no refractive force in the horizontal direction. Therefore, the light rays maintain their original propagation direction.

[0081] The apparatus of this application embodiment, by utilizing a broadband light source, an optical fiber collimator, and a cylindrical lens to construct a broadband light source unit, can improve the beam signal transmission quality and efficiency of the light source used for thin film scanning detection. At the same time, by shaping the light source beam, it is beneficial to improve the quality of subsequent thin film sample scanning imaging.

[0082] It should be noted that, as Figure 2 As shown in the embodiments of this application, by introducing a reflector, the optical path can be folded, the volume of the system can be compressed, and the measurement system can be miniaturized.

[0083] Continue to refer to Figure 2In the embodiments of this application, the sample arm 5 includes an objective lens 51 arranged in sequence, and a displacement lifting stage 52 for fixing the multilayer thin film structure to be tested; the three-dimensional imaging detection module 1 is connected to the displacement lifting stage 52.

[0084] Objective lens 51 is used to acquire signal light from sampling points on the multilayer thin film structure under test;

[0085] The displacement lifting stage 52 is used to adjust the scanning position of the multilayer thin film structure under test under the control of the three-dimensional imaging detection module 1, so as to form the signal light of each sampling point of each layer of the multilayer thin film structure under test.

[0086] Specifically, in the embodiments of this application, the displacement lifting stage 52 may include a displacement stage 521 for moving the multilayer thin film structure under test in the XY plane and a lifting stage 522 for moving the multilayer thin film structure under test in the Z axis.

[0087] In the embodiments of this application, during the scanning process performed by the sample arm, the objective lens first guides the other beam transmitted by the beam splitter to irradiate the multilayer thin film structure sample to be tested set on the displacement lifting stage. The light is reflected by the sample surface to form signal light, and the objective lens can acquire the signal light of the sampling point on the multilayer thin film structure to be tested.

[0088] Furthermore, in the embodiments of this application, the displacement stage, under the control of the three-dimensional imaging detection module, adjusts the scanning position of the multilayer thin film structure under test. Specifically, through the control of the three-dimensional imaging detection module, the test area of ​​the multilayer thin film structure under test can be moved into the scanning field of view. Simultaneously, by controlling the Z-axis displacement stage, the position of the outer surface of the multilayer thin film structure sample under test is moved to a position with a positive optical path difference near the focal plane of the system, avoiding autocorrelation signals. Then, by controlling the displacement stage in the XY plane, the multilayer thin film structure under test is moved in a specific direction, thereby achieving optical scanning of the multilayer thin film structure under test. The scanning signal is used to form signal light at each sampling point of each layer of the multilayer thin film structure under test.

[0089] The apparatus of this application embodiment uses a displacement stage to scan multilayer thin film structure samples, which can ensure the accuracy of the depth between different B-Scan signals in the scanning signal.

[0090] Reference Figure 2 In the embodiments of this application, the reference arm 4 includes an achromatic lens 41, an attenuator 42 and a reference mirror 43 arranged sequentially; the position of the reference mirror 43 is fixed.

[0091] The achromatic lens 41 is used to form a focused reference line spot on the reference mirror 43, while compensating for the dispersion of the broadband light source.

[0092] The attenuator 42 is used to attenuate the light intensity of the light beam transmitted from the achromatic lens 41, so as to reduce the light intensity of the reference arm and match the light intensity of the reference arm and the sample arm.

[0093] Reference mirror 43 is used to reflect the light beam transmitted from attenuator 42 to form reference light for each sampling point of each layer of the multilayer thin film structure under test.

[0094] Specifically, in the embodiments of this application, a reference arm can be constructed using a second achromatic lens, an attenuator, and a reference mirror arranged sequentially. The achromatic lens is primarily used to form a focused reference line spot on the reference mirror, while simultaneously compensating for the dispersion of the broadband light source to improve subsequent imaging quality.

[0095] Furthermore, the attenuator is used to reduce the light intensity of the beam transmitted from the achromatic lens, thereby reducing the light intensity of the reference arm and matching the light intensity of the reference arm with that of the sample arm.

[0096] The reference mirror is primarily used to reflect light in the reference optical path. It reflects the beam from the attenuator to form a reference beam, which then interferes with the signal light reflected from the multilayer thin-film sample. By providing a reflected optical path of known length, the reference mirror allows the device to accurately measure reflected light at different depths within the sample and generate high-resolution cross-sectional images. It should be noted that typical Spectral Domain-Optical Coherence Tomography (SD-OCT) systems adjust the optical path difference between the two arms by adjusting the position of the reference mirror.

[0097] Unlike traditional structures, in this embodiment, by fixing the position of the reference mirror, the mechanical structures used to adjust the optical path difference between the reference arm and the sample arm are placed on the sample arm. This ensures that the spectrum generated by the reference mirror in the imaging spectrometer remains unchanged. This setting makes the spectral calibration results stable, and light of the same wavelength will always interfere at a fixed position on the image plane without shifting, further improving the quality of subsequent scanning imaging.

[0098] Continue to refer to Figure 2 and Figure 3 As shown, in the embodiments of this application, the spectral measurement unit 6 may include a mirror group 61 and an imaging spectrometer 62 arranged sequentially.

[0099] The lens group 61 is used to form a primary imaging optical path with the objective lens 51, so as to perform primary imaging at the entrance of the imaging spectrometer using the reference light and signal light at each sampling point;

[0100] The imaging spectrometer 62 is used to acquire the interference spectral information corresponding to the primary imaging information transmitted from the mirror group 61.

[0101] Specifically, in the embodiments of this application, the spectral measurement unit can consist of a mirror assembly and an imaging spectrometer. The mirror assembly, positioned in front of the imaging spectrometer, serves two purposes: firstly, it receives reference light and signal light transmitted from the beam splitter, and its lens combination organizes the two types of beams to meet the spectrometer's beam requirements; secondly, it images the reference light and signal light beams onto the spectrometer's entrance slit in a single imaging pass, ensuring the spectrometer accurately captures the spectral information of the spectral domain signal in the single imaging data. This optimizes the performance of the entire spectral imaging system and improves the accuracy and reliability of the final measurement.

[0102] Figure 3 This is a schematic diagram of the imaging spectrometer provided in the embodiments of this application, as shown below. Figure 3 As shown, the imaging spectrometer 62 includes an entrance slit 621, a collimating beam expander 622, a diffraction grating 623, a focusing lens group 624, and a two-dimensional array detector 625 arranged sequentially.

[0103] The entrance slit 621 is used to limit stray light that is not related to the primary imaging information from entering the imaging spectrometer;

[0104] The collimator expander 622 is used to collimate the reference light and signal light beams adjusted by the entrance slit 621 in the horizontal direction;

[0105] The diffraction grating 623 is used to diffract and disperse the parallel beam of reference light and the parallel beam of signal light transmitted from the straight beam expander 622.

[0106] The focusing lens group 624 is used to focus light of different wavelengths transmitted from the diffraction grating 623 onto the two-dimensional array detector 625 to form a spectral image, and to compensate for the optical aberrations of the spectral image. The size of the spectral image is controlled by setting the effective focal length.

[0107] The two-dimensional array detector 625 is used to acquire interference spectral information of spectral images across multiple fields of view.

[0108] Specifically, in the embodiments of this application, the imaging spectrometer can be composed of an entrance slit, a collimating beam expander, a diffraction grating, a focusing lens group, and a two-dimensional array detector arranged sequentially. The entrance slit allows adjustment of the incident direction and width of the reference light and signal light transmitted from the lens group, ensuring that only light from specific directions can pass through, thereby reducing interference from stray light unrelated to primary imaging information. Furthermore, adjusting the slit width controls the light flux entering the spectrometer, thus ensuring the spectrometer's resolution.

[0109] The main function of the collimator and beam expander is to collimate the reference light and signal light beams after they have been adjusted by the entrance slit in the horizontal direction. Through collimation, the measurement accuracy and stability of the spectrometer can be significantly improved.

[0110] The diffraction grating primarily functions as a spectral divider, separating the signal light and reference light into their respective spectral lines. This allows for diffraction and dispersion of the parallel beams of reference and signal light transmitted from the beam expander. The performance of the diffraction grating directly affects the spectral resolution and measurement range of the spectrometer.

[0111] The focusing lens group is mainly used to focus light of different wavelengths transmitted from the diffraction grating onto the two-dimensional array detector to form a clear spectral image. It compensates for optical aberrations such as spherical aberration and transverse chromatic aberration present in the spectral image, further improving image quality. Furthermore, the size of the spectral image can be controlled by setting the effective focal length.

[0112] The two-dimensional array detector is a device capable of detecting and recording the intensity of light signals. In an imaging spectrometer, it receives the spectral image after it has been split by a diffraction grating and corrected by a focusing lens group. The detector converts the received light signal into an electrical signal, performs data processing and analysis, and obtains the interference spectral information of the spectral image in multiple fields of view.

[0113] The apparatus of this application embodiment, based on spectral domain OCT, employs parallel spectral domain interferometry. On the one hand, by introducing a focusing lens group to balance and correct optical aberrations such as spherical aberration and transverse chromatic aberration in the spectral image, the imaging quality during the detection process can be greatly improved. On the other hand, through the parallel spectral domain interferometry measurement optical path structure, interference spectral information of multiple sampling points of the thin film sample on the line field of view can be acquired simultaneously. Therefore, only one-dimensional scanning is required, enabling faster imaging and greatly improving the scanning measurement speed of the system.

[0114] Based on the above embodiments, as an optional embodiment, the focusing lens group 624 may include three double-lens arranged sequentially, namely double-lens 6241, double-lens 6242, and double-lens 6243, wherein the optical power of the three double-lens is positive, negative, and positive, respectively. By optimizing the curvature radius and spacing of the three lenses and selecting appropriate materials, it is possible to simultaneously correct and compensate for various aberrations present in a single image while meeting the imaging size requirements.

[0115] Specifically, in the embodiments of this application, by introducing three achromatic lenses (with optical powers of positive and negative in sequence) into the imaging spectrometer to replace the commonly used single lens, the added negative lens can simultaneously balance the field curvature in the spectral direction and the field of view, further improving the imaging effect during the detection process.

[0116] It should be noted that traditional line-field spectral domain OCT systems, in terms of both imaging performance optimization and spectral calibration, only assume that the ideal point object in different fields of view is located on the front focal plane of the collimating lens, treating the imaging spectrometer as an independent component for optimization. However, in actual systems, the front focal plane is not an ideal point object, but rather a primary image of the sample under test. This will cause the system optimization results to deviate from the actual situation.

[0117] In the embodiments of this application, the front-end telecentric optical path (achromatic lens 41 + lens group 61) and the rear-end imaging spectrometer are optimized as a complete imaging system. It should also be noted that the single-sided lens in this embodiment can actually represent a lens group, not just a single lens.

[0118] The following describes the testing method of the nondestructive testing device for multilayer thin film structures provided in this application. The testing method described below can be referred to in correspondence with the nondestructive testing device for multilayer thin film structures described above.

[0119] Figure 4 The flowchart of the detection method of the nondestructive testing device for multilayer thin film structures provided in this application embodiment can be applied to any of the aforementioned nondestructive testing devices for multilayer thin film structures. It is understood that the main execution component of this method is the three-dimensional imaging detection module, such as... Figure 4 As shown, the method includes:

[0120] Step S1: Obtain the interference spectrum information of each sampling point of each layer of the multilayer thin film structure under test;

[0121] Step S2: Generate three-dimensional tomographic image data with reflection intensity information based on the interference spectral information of each sampling point;

[0122] Step S3: Based on the three-dimensional tomographic image data of each sampling point, determine the reflection intensity scanning information corresponding to each sampling point;

[0123] Step S4: Using the reflection intensity scanning information corresponding to each sampling point, perform three-dimensional imaging detection on the multilayer thin film structure under test.

[0124] Specifically, in the embodiments of this application, in step S1, the sample to be tested is fixed on the XY displacement stage, and the test area of ​​the multilayer thin film structure to be tested is moved into the scanning field of view. The Z-axis lifting stage is controlled to move the sample to a position with positive optical path difference near the focal plane, avoiding the autocorrelation signal. The sample arm is used to scan the multilayer thin film structure sample to be tested in the X direction. With each step, the interference spectrum information of all sampling points in the line field is recorded. In this way, the three-dimensional imaging detection module can obtain the interference spectrum information of each sampling point of each layer of the multilayer thin film structure to be tested.

[0125] Further, in step S2, after the scanning is completed, based on the interference spectral information of each sampling point, the spectra of all sampling points are interpolated to the uniform wavenumber domain, and then a fast Fourier transform is performed to obtain three-dimensional tomographic image data with reflection intensity information, which can be represented as T[i,j,γ], where i is the index of A-Scans in each B-Scans in the scanning signal, and j and γ are the indices of B-Scans and axial depth values, respectively.

[0126] Further, in step S3, the line field-of-view intensity is normalized based on the 3D tomographic image data of each sampling point. Specifically, considering the non-uniform illumination of the line spot, in order to make the intensity threshold effective for different field-of-view points, the intensity of the aforementioned 3D tomographic image data needs to be normalized first. Using the pre-measured light intensity distribution S[i] along the line field-of-view direction, the maximum value S is found. max Next, calculate the normalization coefficient C[i] = S max / S[i]. Then, normalizing the reflection intensity distribution of the three-dimensional tomographic image data T[i,j,γ] yields the normalized result T. n [i,j,γ]=C[i]·T[i,j,γ].

[0127] Furthermore, by traversing all sampling points, the reflection intensity scan information A-Scan signal corresponding to each sampling point can be determined, which can be expressed as f[z] γ ] = T n [i o ,j0,γ].

[0128] Furthermore, in step S4, using the reflection intensity scanning information A-Scan signal corresponding to each sampling point, a targeted detection strategy is adopted according to the type of the multilayer thin film structure to be tested, and three-dimensional imaging detection is performed on the multilayer thin film structure to be tested.

[0129] The non-destructive testing method for multilayer thin film structures in this application employs spectral domain optical coherence tomography (optical coherence tomography). It utilizes a broadband light source, a sample arm, and a reference arm to perform linear scanning detection on the multilayer thin film structure under test. The reference arm provides linear reference light, while the sample arm scans the structure to provide linear signal light. A spectral measurement unit captures the spectral information of the interference signal between the reference arm and the sample arm in real time. This method generates two-dimensional tomographic or three-dimensional images of the multilayer thin film structure under test without axial scanning, and provides micron-level spatial resolution. It achieves non-contact, high-resolution, rapid, and non-destructive testing, applicable to various transparent or semi-transparent multilayer thin film materials.

[0130] Based on the above embodiments, as an optional embodiment, the multilayer thin film structure to be tested is an FPC; using the reflection intensity scanning information corresponding to each sampling point, three-dimensional imaging detection of the multilayer thin film structure to be tested is performed, including:

[0131] Based on the reflection intensity scanning information corresponding to each sampling point of each layer of the FPC structure, the maximum and second maximum reflection intensity information of the reflection intensity scanning information corresponding to each sampling point in the target depth range are determined.

[0132] Based on the maximum and submaximum reflection intensity information corresponding to each sampling point, the height map data corresponding to each sampling point is determined;

[0133] Using the height map data and spatial plane coordinates corresponding to each sampling point, a three-dimensional point cloud image of the flexible printed circuit board is generated to detect defects in each layer of the FPC structure.

[0134] It should be noted that FPC is a typical multilayer film structure sample. For FPC samples containing only a solder resist layer, a conductor layer, and a substrate layer, the following algorithm can perform high-resolution imaging of the internal circuit structure of the FPC, which can then be used for detection and analysis. This allows for the early detection and correction of manufacturing or process defects, such as poor soldering, material delamination, and abnormal conductive paths, providing crucial information for quality monitoring during the FPC manufacturing process.

[0135] Specifically, after acquiring the volumetric tomography image data and determining the A-Scan signal of the reflection intensity scan information corresponding to each sampling point, the following steps are performed for the scenario where the multilayer thin film structure under test is an FPC:

[0136] Step S101: Using the scanning information of each reflection intensity, find the maximum reflection intensity information and the second maximum reflection intensity information.

[0137] Specifically, iterating through all sampling points, for each A-Scan signal: f[z] γ ] = Tn [i o [j0,γ], find the maximum and second maximum peaks within the target depth range including the solder mask surface and the metal conductor, that is, determine the maximum reflection intensity information f[z] of the reflection intensity scan information corresponding to each sampling point within the target depth range. α and submaximum reflection intensity information f[z β ].

[0138] Where z represents the optical path difference between the sample arm and the reference mirror, i.e., the depth coordinates, which is an equally spaced array determined by the sampling rate and sampling interval of the uniform wavenumber domain; α and β are the indices corresponding to the depth coordinates.

[0139] Step S102: Perform peak analysis and height map calculation.

[0140] Specifically, in this embodiment, the surface areas of FPC types are divided into two main categories: the first category is the area not covered by the solder mask, which is generally the exposed pads; the second category is the area covered by the solder mask. The area covered by the solder mask is further divided into two categories based on whether there is a metal conductor underneath.

[0141] Figure 5 (a) is a schematic diagram of the optical path of the device provided in this application scanning the metal pads on the FPC; (b) is a schematic diagram of the optical path of the device provided in this application scanning the solder mask layer on the FPC without embedded conductors; (c) is a schematic diagram of the optical path of the device provided in this application scanning the solder mask layer on the FPC with embedded conductors. Figure 5 As shown in (a), at the solder pad, due to the strong reflection of the exposed metal, a single peak with high intensity and high signal-to-noise ratio can be generated; in the remaining areas covered with solder resist, due to the absorption of the protective layer, the signal-to-noise ratio is weaker than that of the former.

[0142] like Figure 5 As shown in (c), if a conductor is present below, the strong reflection from the copper foil causes the A-Scan signal to typically have two peaks, corresponding to the interface between the conductor and the solder mask, and the outer surface of the solder mask, respectively. Figure 5 As shown in (b), in areas without conductors, only the reflected signal from the outer surface of the solder mask can generally be detected. Based on the above analysis, for each sampling point, the maximum reflection intensity information f[z] is... α and submaximum reflection intensity information f[z β The following four conditions can be used to classify different situations and assign values ​​to the heightmap:

[0143] (1) If f[z α If ]≥τ1, then H trace [i0,j0]=z α ;

[0144] (2) If τ2 <f[z α If ] < τ1, then H mask [i0,j0]=z α ;

[0145] (3) If f[z β ]≥τ2,|z α -z β |∈[t min ,t max ], then H mask [i0,j0]=max{z α ,z β}, H trace [i0,j0]=min{z α ,z β};

[0146] (4) If none of the above conditions are met, it is judged as an outlier and is not recorded.

[0147] Among them, H trace and H mask These represent the height maps of the upper surface of the internal circuitry of the FPC and the outer surface of the solder mask, respectively. η represents the minimum threshold ratio where the two peaks are on the same order of magnitude, τ1 represents the minimum reflection intensity threshold of the pad metal, and τ2 represents the minimum reflection intensity threshold classified as a reflection peak rather than noise. [t] min ,t max The value represents the range of optical path difference between the surface of the solder mask and the upper surface of the conductor. All of the above parameters can be determined by experimental data.

[0148] Step S103: Calculate the sub-pixel height value.

[0149] Specifically, to achieve more accurate height extraction, the sub-pixel height values ​​are recalculated using the Energy Center of Gravity Method (ECCM) in the A-Scan signal corresponding to each sampling point on the height map, instead of directly taking discrete height values. This process can be represented as follows:

[0150]

[0151] The value of d is generally taken as 2.

[0152] Step S104: Generate a 3D point cloud map.

[0153] Specifically, based on the known scanning step size and actual lateral resolution of the system, each sampled data point is assigned spatial plane coordinates in real space, namely X and Y coordinate values, which are then combined with the depth information calculated in step S103. It can generate 3D point cloud maps of each layer of the FPC structure. During the process, noise points are filtered out using point cloud denoising algorithms. By changing the position of the XY displacement stage and repeating the scanning operation, the topographic information between FPC regions can be stitched together.

[0154] Step S105: Perform structural defect detection on each layer of the FPC.

[0155] After obtaining the visualized internal circuit diagram of the FPC, we can combine manual screening, traditional image processing, machine learning, or collect a sufficient dataset to use deep learning to perform FPC quality inspection and check whether there are structural defects in the multi-layer structure of the FPC.

[0156] The method in this application embodiment analyzes the peak reflection intensity by utilizing the reflection intensity scanning information corresponding to each sampling point of each layer of the FPC structure to obtain the height map data corresponding to each sampling point, thereby generating a three-dimensional point cloud image of each layer of the FPC structure. This method can effectively achieve quality inspection of each layer of the FPC structure, with good imaging quality and high detection efficiency.

[0157] Based on the above embodiments, as an optional embodiment, the multilayer thin film structure to be tested is a display screen; using the reflection intensity scanning information corresponding to each sampling point, three-dimensional imaging detection of the multilayer thin film structure to be tested is performed, including:

[0158] Gaussian filtering is applied to the reflection intensity scan information corresponding to each sampling point of each layer of the display screen to obtain each processed reflection intensity scan information.

[0159] Based on the processed reflection intensity scanning information, the interface positioning imaging results of each layer of the display screen are determined.

[0160] Interface defects are detected in each layer of the display screen based on the interface positioning imaging results.

[0161] Specifically, in the embodiments of this application, after acquiring the volume tomography image data and determining the reflection intensity scanning information A-Scan signal corresponding to each sampling point, the following steps are specifically performed for the scenario where the multilayer thin film structure under test is a display screen:

[0162] Step S201: Perform signal preprocessing.

[0163] Specifically, after acquiring volumetric tomography image data, assuming the i-th A-Scan signal is represented as A i (z), i.e., A i(z)=f[z γ ] = T n [i o ,j0,γ].

[0164] Where z represents the coordinate in the depth direction, i = 1, 2, 3, ..., N, and N is the number of sampling points. Each A-Scan signal is processed by Gaussian filtering, and the resulting reflection intensity scan information S is obtained. i (z), that is:

[0165] S i (z)=A i (z)*G(z,σ);

[0166] Where G(z,σ) is the Gaussian kernel function, which can be expressed as:

[0167]

[0168] Step S202: Perform interface positioning.

[0169] Specifically, the preprocessed signal S is processed according to the following formula. i (z) Perform peak detection, i.e.:

[0170]

[0171] Among them, P i Let λ be the set of peak locations detected in the i-th A-Scan signal, and let λ represent the threshold coefficient.

[0172] Step S203: Perform multi-signal fusion.

[0173] Specifically, clustering and fusing the peak positions of different A-Scans can be represented as follows:

[0174] D j,k =|P j -P k |,j,k∈[1,N]

[0175] When D j,k If the distance is less than δ, then they are considered to belong to the same interface, where δ is the distance threshold.

[0176] According to the above formula, the interface positioning and imaging results of each layer of the display screen can be determined.

[0177] Further, in step S204, layer characteristic analysis is performed to determine the thickness parameters.

[0178] Specifically, for a layered structure formed by two adjacent interfaces, its thickness T is defined. m :

[0179]

[0180] in, This represents the average depth of the m-th interface.

[0181] The smoothness estimation function F of interface m m It can be represented as:

[0182]

[0183] The uniformity evaluation function for interface m can be expressed as:

[0184]

[0185] Step S205: Perform interface defect detection to determine the defects.

[0186] The defect feature vector can be defined as follows:

[0187] V m =[E m U m ,T m ];

[0188] Interface m can be determined to have a defect when any of the following conditions are met:

[0189] F m >F threshold ;

[0190] U m >U threshold ;

[0191] |T m -T ref |>T threshold ;

[0192] Among them, F threshold U threshold and T threshold These are respectively represented as the flatness estimation function threshold, the uniformity evaluation function threshold, and the thickness threshold, which can be determined based on the actual measured structural parameters of the display screen.

[0193] The method of this application embodiment performs Gaussian filtering on the reflection intensity scanning information corresponding to each sampling point of each layer structure of the display screen, and performs interface positioning imaging on each layer structure of the display screen based on the processed reflection intensity scanning information to perform quality detection on each layer structure of the display screen. This method can effectively achieve quality detection on each layer structure of the display screen, with good imaging quality and high detection efficiency.

[0194] Based on the methods in the above embodiments, this application provides an electronic device, such as... Figure 6 As shown, the electronic device may include a processor 610, a communications interface 620, a memory 630, and a communication bus 640, wherein the processor 610, the communications interface 620, and the memory 630 communicate with each other via the communication bus 640. The processor 610 can call logical instructions in the memory 630 to execute the methods in the above embodiments.

[0195] Furthermore, the logical instructions in the aforementioned memory 630 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application.

[0196] Based on the methods in the above embodiments, this application provides a computer-readable storage medium storing a computer program that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0197] Based on the methods in the above embodiments, this application provides a computer program product that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0198] It is understood that the processor in the embodiments of this application can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. A general-purpose processor can be a microprocessor or any conventional processor.

[0199] The method steps in this application embodiment can be implemented in hardware or by a processor executing software instructions. The software instructions can consist of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can reside in an ASIC.

[0200] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0201] It is understood that the various numerical designations used in the embodiments of this application are merely for the convenience of description and are not intended to limit the scope of the embodiments of this application.

[0202] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0203] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after connection. "Rotary connection" refers to a connection where the components can rotate relative to each other after connection. "Sliding connection" refers to a connection where the components can slide relative to each other after connection. The directional terms mentioned in the embodiments of this application, such as "top," "bottom," "inner," "outer," "left," and "right," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0204] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0205] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A testing method applied to a non-destructive testing device for multilayer thin film structures, characterized in that, The device includes: The system includes a three-dimensional imaging detection module, a beam splitter, and a broadband light source unit, a reference arm, a sample arm, and a spectral measurement unit arranged around the beam splitter according to a preset optical path. The three-dimensional imaging detection module is connected to the spectral measurement unit. The optical path formed by the broadband light source unit, the reference arm, and the sample arm is used to form a detection line beam on the surface of the multilayer thin film structure to be tested and on the reference surface in the reference arm. The beam splitter is used to split the line beam emitted from the broadband light source unit into two line beams. One line beam is scanned by the sample arm to form signal light at each sampling point on the line beam, and the other line beam is formed by the reference arm to form reference light at each sampling point. The spectral measurement unit is used to collect reference light and signal light at each sampling point on the line beam that detects each layer of the multilayer thin film structure under test during the scanning process of the sample arm, and generate corresponding interference spectral information. The three-dimensional imaging detection module is used to perform three-dimensional imaging detection on the multilayer thin film structure under test based on the interference spectral information of all the acquired sampling points. The method includes: Obtain the interference spectrum information of each sampling point of each layer of the multilayer thin film structure under test; Three-dimensional tomographic image data with reflection intensity information is generated based on the interference spectral information of each of the sampling points; Based on the three-dimensional tomographic image data of each sampling point, determine the reflection intensity scanning information corresponding to each sampling point; The three-dimensional imaging detection of the multilayer thin film structure under test is performed using the reflection intensity scanning information corresponding to each sampling point. The step of using the reflection intensity scanning information corresponding to each sampling point to perform three-dimensional imaging detection of the multilayer thin film structure under test includes: Based on the reflection intensity scanning information corresponding to each sampling point of the multilayer thin film structure under test, the maximum reflection intensity information and the second maximum reflection intensity information of the reflection intensity scanning information corresponding to each sampling point within the target depth range are determined. Based on the maximum reflection intensity information and the second maximum reflection intensity information corresponding to each sampling point, the height map data corresponding to each sampling point is determined; Subpixel height values ​​are extracted from the peak values ​​of the A-Scan signal in the heightmap data corresponding to each sampling point to obtain the corresponding depth information. Based on the depth information and spatial plane coordinates, a three-dimensional point cloud image of the multilayer thin film structure under test is generated to detect structural defects in each layer of the multilayer thin film structure under test. The step of determining the height map data corresponding to each sampling point based on the maximum reflection intensity information and the second maximum reflection intensity information corresponding to each sampling point includes: By using the ratio of the maximum reflection intensity information to the second maximum reflection intensity information corresponding to each sampling point and the preset minimum threshold ratio, the height map of each layer of the multilayer thin film structure under test is classified and judged to determine the height map data corresponding to each sampling point.

2. The detection method according to claim 1, characterized in that, The sample arm includes objective lenses arranged in sequence and a displacement lifting stage for fixing the multilayer thin film structure to be tested; the three-dimensional imaging detection module is connected to the displacement lifting stage. The objective lens is used to acquire the signal light at the sampling points on the multilayer thin film structure under test. The displacement lifting platform is used to adjust the scanning position of the multilayer thin film structure under the control of the three-dimensional imaging detection module, so as to generate signal light for each sampling point of each layer of the multilayer thin film structure under test.

3. The detection method according to claim 2, characterized in that, The spectral measurement unit includes a mirror assembly and an imaging spectrometer arranged sequentially. The lens group is used to form a primary imaging optical path with the objective lens, so as to perform primary imaging at the entrance of the imaging spectrometer using the reference light and signal light at each of the sampling points; The imaging spectrometer is used to acquire the interference spectral information corresponding to the primary imaging information transmitted from the mirror group.

4. The detection method according to claim 3, characterized in that, The imaging spectrometer includes an entrance slit, a collimating beam expander, a diffraction grating, a focusing lens group, and a two-dimensional array detector arranged sequentially. The entrance slit is used to restrict stray light unrelated to the primary imaging information from entering the imaging spectrometer; The collimator expander is used to collimate the reference light and signal light beams after passing through the entrance slit in the horizontal direction. The diffraction grating is used to diffract and disperse the parallel beams of the reference light and the signal light transmitted from the collimator and expander. The focusing lens group is used to focus light of different wavelengths transmitted from the diffraction grating onto the two-dimensional array detector to form a spectral image, and to compensate for the optical aberrations of the spectral image. The size of the spectral image is controlled by setting the effective focal length. The two-dimensional array detector is used to acquire interference spectral information of the spectral image in multiple fields of view.

5. The detection method according to claim 4, characterized in that, The focusing lens group includes three double-film lenses arranged in sequence, with the optical power of the three double-film lenses being positive, negative, and positive, respectively.

6. The detection method according to claim 1, characterized in that, The reference arm includes an achromatic lens, an attenuator, and a reference mirror arranged sequentially; the position of the reference mirror is fixed. The achromatic lens is used to form a focused reference line spot on the reference mirror, while compensating for the dispersion of the broadband light source. The attenuator is used to attenuate the light intensity of the beam transmitted from the achromatic lens, thereby reducing the light intensity of the reference arm and matching the light intensity of the reference arm with that of the sample arm. The reference mirror is used to reflect the light beam transmitted from the attenuator to form reference light for each sampling point of each layer of the multilayer thin film structure under test.

7. The detection method according to any one of claims 1-6, characterized in that, The broadband light source unit includes a broadband light source, an optical fiber collimator, and a cylindrical lens arranged in sequence. Broadband light sources are used to provide light sources within a target spectral range; The fiber collimator is used to collimate and adjust the beam transmitted from the broadband light source. The cylindrical lens is used to shape the collimated beam from the fiber collimator into a line beam, which is then transmitted to the beam splitter.

8. The detection method according to claim 1, characterized in that, The multilayer thin-film structure to be tested includes a flexible printed circuit board.

9. The detection method according to claim 1, characterized in that, The multilayer thin-film structure under test is a display screen; the step of performing three-dimensional imaging detection on the multilayer thin-film structure under test using the reflection intensity scanning information corresponding to each sampling point includes: Gaussian filtering is performed on the reflection intensity scanning information corresponding to each sampling point of each layer of the display screen to obtain each processed reflection intensity scanning information. Based on the processed reflection intensity scanning information of each layer of the display screen, the interface positioning imaging result of each layer of the display screen is determined. Based on the interface positioning imaging results, interface defects are detected in each layer of the display screen structure.

Images