Photoelectric combined batch detection method and device for LED wafer

Abstract

The application belongs to the technical field of semiconductors, and discloses a photoelectric combined batch detection method and device for an LED wafer, wherein a light beam is transmitted to a spatial light modulator for pattern modulation to obtain a compressed sensing encoding pattern; the compressed sensing encoding pattern is focused on the surface of a wafer to be detected to make the wafer to be detected generate a photoluminescence signal and a photo-generated current signal; the photo-generated current signal generated by the wafer to be detected is led out through a flexible conductive layer; the photoluminescence signal generated by the wafer to be detected and the photo-generated current signal led out by the flexible conductive layer are collected; the compressed sensing encoding pattern, the collected photoluminescence signal and the photo-generated current signal are input into a compressed observation model, and a real photoelectric signal of the wafer to be detected is obtained by using a sparse signal reconstruction algorithm. Under the premise of not damaging the chip, high-speed, high-throughput, photoelectric combined batch detection of the wafer is realized.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to a method and apparatus for combined optoelectronic batch inspection of LED wafers. Background Technology

[0002] With the rapid development of micro-LED (Light Emitting Diode) technology, the inspection process in wafer manufacturing has become crucial, especially the inspection of wafer surface defects, uniformity, and luminescence characteristics. High-density, small-size micro-LED arrays place extremely high demands on the consistency of optoelectronic performance, defect control, and yield evaluation.

[0003] Current technologies primarily rely on point-to-point contact testing methods using probe stations. This requires aligning and contacting each chip individually, which is slow and cannot meet the high-throughput, rapid screening requirements of large-area wafers, resulting in low testing efficiency. This method is also prone to damage; mechanical probe contact can easily scratch microelectrodes or damage the fragile chip structure, especially on flexible substrates. Furthermore, the alignment accuracy requirements are extremely high. The spacing between Micro-LED electrodes is very small; even a tiny alignment error can lead to contact failure, affecting the reliability of the test results.

[0004] To overcome the shortcomings of contact detection, some non-contact or improved solutions have emerged, such as patent CN114280453B, which achieves non-destructive contact. However, signal reading is still a single-point serial method, which cannot simultaneously meet the requirements of high speed and high spatial resolution, and is still limited by strict alignment requirements. Another example is patent CN118937944A, which achieves non-contact excitation and optical signal acquisition. However, it can only acquire spectral signals and cannot acquire the crucial electrical signals, resulting in incomplete detection information.

[0005] Given the above background, existing technologies cannot achieve high-speed, high-throughput, optoelectronic combined (simultaneous acquisition of optical and electrical information) batch testing of Micro-LED wafers without damaging the chip. Summary of the Invention

[0006] To achieve non-destructive, high-speed, and high-throughput optoelectronic joint inspection of LED wafers, this application proposes, in a first aspect, a method for joint optoelectronic batch inspection of LED wafers, the method comprising:

[0007] The beam is transmitted to a spatial light modulator for pattern modulation to obtain a compressed sensing coded pattern.

[0008] The compressed sensing coding pattern is focused onto the surface of the wafer to be inspected, so that the wafer to be inspected generates photoluminescence signal and photocurrent signal;

[0009] The photocurrent signal generated by the wafer under test is extracted through a flexible conductive layer;

[0010] The photoluminescence signal generated by the wafer under test and the photocurrent signal derived from the flexible conductive layer are collected.

[0011] The compressed sensing coding pattern, the acquired photoluminescence signal, and the photocurrent signal are input into the compressed observation model, and the real photoelectric signal of the wafer to be tested is obtained by using a sparse signal reconstruction algorithm.

[0012] In one possible implementation, transmitting the light beam to a spatial light modulator for pattern modulation to obtain a compressed sensing coded pattern includes:

[0013] The excitation light output from the laser is obtained, and the excitation light is input into the collimating lens for adjustment to obtain a uniform parallel beam.

[0014] The parallel beam is transmitted to a spatial light modulator for pattern modulation, and a compressed sensing coded pattern is formed under the drive of a preset Hadamard compressed sensing coded sequence or Walsh compressed sensing coded sequence.

[0015] In one possible implementation, the step of deriving the photocurrent signal generated by the wafer under test through the flexible conductive layer includes:

[0016] The wafer to be tested is placed above a flexible micro / nano electrode;

[0017] Pressure is applied to the wafer to be tested through a transparent cover plate, so that the lower surface of the wafer to be tested is tightly bonded to the upper surface of the flexible micro-nano electrode;

[0018] The photogenerated current signal is transmitted through the flexible micro / nano electrode and an external current acquisition circuit to form a path and is exported. The flexible micro / nano electrode is made of flexible material and has an array of micropillar conductive structures arranged on its surface.

[0019] In one possible implementation, acquiring the photoluminescence signal and photocurrent signal generated by the wafer under test includes:

[0020] The photoluminescence signal generated by the wafer under test is collected by a ring fiber array surrounding the wafer; the collected signal is filtered to remove the excitation light and then acquired by a spectrometer.

[0021] The photocurrent signal output by the flexible conductive layer is acquired through the external current acquisition circuit.

[0022] In one possible implementation, after the step of acquiring the photoluminescence signal and photocurrent signal generated by the wafer under test, the method further includes:

[0023] The wafer to be tested is translated along a preset path, and then the process of transmitting the light beam to the spatial light modulator for pattern modulation is repeated to obtain a compressed sensing coded pattern, until all parts of the wafer to be tested have been processed.

[0024] In one possible implementation, the compressed observation model is characterized by being established in the following manner:

[0025] Based on compressed sensing theory, the following observation model is constructed using historical compressed sensing coded patterns, historical photoluminescence signals, and historical photocurrent signals:

[0026]

[0027] By combining K different encodings, a compressed observation model is constructed:

[0028]

[0029] Where λ represents wavelength, λ i For the i-th wavelength, Y k (λ) and Y(λ) i ) represents the historical photoluminescence signal and historical photocurrent signal excited by the historical compressed sensing coded pattern, M∈{0,1} K*N S is a historical compressed sensing encoding pattern. j (λ) and S(λ) i ) represents the actual photoelectric signal of the wafer, K represents the number of times the historical compressed sensing coded pattern was generated, and N represents the total number of pixels on the wafer.

[0030] In one possible implementation, the sparse signal reconstruction algorithm includes L1 norm minimization, orthogonal matching pursuit, and iterative thresholding algorithm.

[0031] Secondly, this application provides a photoelectric combined batch inspection device for LED wafers, the device comprising:

[0032] The modulation module is used to transmit the light beam to the spatial light modulator for pattern modulation to obtain a compressed sensing coded pattern.

[0033] The excitation module is used to focus the compressed sensing coding pattern onto the surface of the wafer to be inspected, so that the wafer to be inspected generates photoluminescence signal and photocurrent signal.

[0034] A conductive module is used to extract the photocurrent signal generated by the wafer under test through a flexible conductive layer;

[0035] The acquisition module is used to acquire the photoluminescence signal generated by the wafer under test and the photocurrent signal derived from the flexible conductive layer;

[0036] The reconstruction module is used to input the compressed sensing coding pattern, the acquired photoluminescence signal, and the photocurrent signal into the compressed observation model, and use a sparse signal reconstruction algorithm to obtain the real photoelectric signal of the wafer to be tested.

[0037] In one possible implementation, the modulation module is specifically used for:

[0038] The excitation light output from the laser is obtained, and the excitation light is input into the collimating lens for adjustment to obtain a uniform parallel beam.

[0039] The parallel beam is transmitted to a spatial light modulator for pattern modulation, and a compressed sensing coded pattern is formed under the drive of a preset Hadamard compressed sensing coded sequence or Walsh compressed sensing coded sequence.

[0040] In one possible implementation, the conductive module is specifically used for:

[0041] The wafer to be tested is placed above a flexible micro / nano electrode;

[0042] Pressure is applied to the wafer to be tested through a transparent cover plate, so that the lower surface of the wafer to be tested is tightly bonded to the upper surface of the flexible micro-nano electrode;

[0043] The photogenerated current signal is transmitted through the flexible micro / nano electrode and an external current acquisition circuit to form a path and is exported. The flexible micro / nano electrode is made of flexible material and has an array of micropillar conductive structures arranged on its surface.

[0044] The optoelectronic combined batch inspection method for LED wafers provided in this application transmits a light beam to a spatial light modulator for pattern modulation to obtain a compressed sensing coded pattern; the compressed sensing coded pattern is focused onto the surface of the wafer to be inspected, causing the wafer to generate photoluminescence and photocurrent signals; the photocurrent signal generated by the wafer is extracted through a flexible conductive layer; the photoluminescence signal generated by the wafer and the photocurrent signal extracted by the flexible conductive layer are collected; the compressed sensing coded pattern, the collected photoluminescence signal, and the photocurrent signal are input into a compressed observation model, and the real optoelectronic signal of the wafer is obtained using a sparse signal reconstruction algorithm. This method achieves high-speed, high-throughput, optoelectronic combined batch inspection of wafers without damaging the chip. Attached Figure Description

[0045] Figure 1 A schematic flowchart of a photoelectric combined batch inspection method for LED wafers provided in an embodiment of the present invention;

[0046] Figure 2This is a schematic diagram of the wafer bonding relationship provided in an embodiment of the present invention;

[0047] Figure 3 A schematic diagram of a photoelectric combined batch inspection system for LED wafers provided in an embodiment of the present invention;

[0048] Figure 4 This is a schematic diagram of the excitation of the wafer to be tested provided in an embodiment of the present invention. Detailed Implementation

[0049] The present invention will be described in detail below through embodiments.

[0050] With the rapid development of micro-LED (Light Emitting Diode) technology, the inspection process in wafer manufacturing has become crucial, especially the inspection of wafer surface defects, uniformity, and luminescence characteristics. High-density, small-size micro-LED arrays place extremely high demands on the consistency of optoelectronic performance, defect control, and yield evaluation.

[0051] Current technologies primarily rely on point-to-point contact testing methods using probe stations. This requires aligning and contacting each chip individually, which is slow and cannot meet the high-throughput, rapid screening requirements of large-area wafers, resulting in low testing efficiency. This method is also prone to damage; mechanical probe contact can easily scratch microelectrodes or damage the fragile chip structure, especially on flexible substrates. Furthermore, the alignment accuracy requirements are extremely high. The spacing between Micro-LED electrodes is very small; even a tiny alignment error can lead to contact failure, affecting the reliability of the test results.

[0052] To overcome the shortcomings of contact detection, some non-contact or improved solutions have emerged, such as patent CN114280453B, which achieves non-destructive contact. However, signal reading is still a single-point serial method, which cannot simultaneously meet the requirements of high speed and high spatial resolution, and is still limited by strict alignment requirements. Another example is patent CN118937944A, which achieves non-contact excitation and optical signal acquisition. However, it can only acquire spectral signals and cannot acquire the crucial electrical signals, resulting in incomplete detection information.

[0053] Given the above background, existing technologies cannot achieve high-speed, high-throughput, optoelectronic combined (simultaneous acquisition of optical and electrical information) batch testing of Micro-LED wafers without damaging the chip.

[0054] For the purpose of non-destructive optoelectronic joint testing, firstly, see... Figure 1 This application provides a method for combined optoelectronic batch inspection of LED wafers, the method comprising:

[0055] S101, the beam is transmitted to the spatial light modulator for pattern modulation to obtain a compressed sensing coded pattern.

[0056] A spatial light modulator (SLM) is a device that modulates the spatial distribution of light waves, altering their amplitude, intensity, phase, and polarization state. SLMs are key components in modern optics fields such as real-time optical information processing, adaptive optics, and optical computing. A SLM can be a Digital Micromirror Device (DMD). After the light beam enters the DMD, it is driven by a pre-defined Hadamard or Walsh compressed sensing coding sequence to deflect and form a sparse orthogonal spatial pattern. This pattern is a sequence of sparse binary patterns selected from the Hadamard or Walsh orthogonal coding matrix, with each frame corresponding to a spatially coded illumination distribution. The pattern's sparsity and orthogonality allow for spatially structured excitation of the entire wafer area while significantly reducing the number of modulation operations.

[0057] Specifically, the compressed sensing coded pattern can be obtained through the following steps.

[0058] Step 1: Obtain the excitation light output from the laser, and input the excitation light into the collimating lens for adjustment to obtain a uniform parallel beam;

[0059] Step two involves transmitting the parallel beam to a spatial light modulator for pattern modulation, thereby forming a compressed sensing coded pattern under the drive of a preset Hadamard compressed sensing coding sequence or Walsh compressed sensing coding sequence.

[0060] The laser can output a narrow-band, uniform excitation beam, which is shaped by a collimating lens to form a uniform parallel beam, and then enters the DMD for spatial modulation.

[0061] S102, the compressed sensing coding pattern is focused onto the surface of the wafer to be tested, so that the wafer to be tested generates photoluminescence signal and photocurrent signal.

[0062] The compressed sensing coded pattern described above can be clearly imaged onto the wafer surface using a focusing microscope, enabling parallel structured excitation of the entire wafer area. This allows the wafer under test to simultaneously generate photoluminescence and photocurrent signals, significantly improving excitation efficiency and signal strength. This regional structured modulation excitation method allows each frame of the compressed sensing coded pattern to simultaneously excite multiple pixel areas, generating superimposed photoluminescence and photocurrent signals, avoiding point-by-point scanning, and improving the detection signal strength and signal-to-noise ratio.

[0063] S103, the photocurrent signal generated by the wafer under test is extracted through the flexible conductive layer.

[0064] The flexible conductive layer is a micro / nano structured conductive layer with uniform resistance distribution, composed of flexible materials such as polydimethylsiloxane (PDMS) or polyimide (PI). The surface can be designed with structures such as micropillars, corrugations, or nano-pits, possessing excellent mechanical flexibility and self-adaptive capabilities. It can be non-destructively bonded to the electrodes of micro-devices to achieve stable extraction of photogenerated current signals. Specifically, it can include the following steps:

[0065] Step 1: Place the wafer to be tested above a flexible micro / nano electrode;

[0066] Step 2: Apply pressure to the wafer to be tested through a transparent cover plate to make the lower surface of the wafer to be tested fit tightly against the upper surface of the flexible micro-nano electrode;

[0067] The photogenerated current signal is transmitted through the flexible micro-nano electrode and an external current acquisition circuit to form a path. The flexible micro-nano electrode is made of flexible material and has an array of micropillar conductive structures arranged on its surface.

[0068] like Figure 2 As shown, the LED wafer body 101 is provided with electrodes 102, and the surface of the flexible micro / nano electrode 104 is provided with micropillar conductive structures 103. The flexible micro / nano electrode has good deformability and conductivity, and can adapt to the small undulations and height differences of the wafer electrode. After being pressed by a transparent cover plate, it achieves uniform adhesion to the wafer, ensuring reliable contact of uneven electrodes, realizing stable and reliable output signals, and ensuring the non-destructive nature of the contact process and the effective extraction of photocurrent signals.

[0069] S104, acquire the photoluminescence signal generated by the wafer under test and the photocurrent signal derived from the flexible conductive layer.

[0070] Synchronously acquire the photoelectric signals generated by the wafer under test, including:

[0071] Step 1: The photoluminescence signal generated by the wafer under test is collected by a ring fiber array surrounding the wafer under test; the collected signal is then filtered to remove the excitation light and acquired by a spectrometer.

[0072] Step 2: Acquire the photocurrent signal output by the flexible conductive layer through the external current acquisition circuit.

[0073] For photoluminescence signals, a ring fiber array is used to collect the signals from multiple angles. After the excitation light interference is removed by a filter, the photoluminescence signals are then collected by a spectrometer. For photocurrent signals, an external current acquisition circuit is used to collect the current or voltage signals output from the flexible conductive layer. The acquisition method of this application does not require physical contact with probes or complex alignment, avoiding electrode damage and chip surface contamination, and is not limited by chip size.

[0074] S105, the compressed sensing coding pattern, the acquired photoluminescence signal, and the photocurrent signal are input into the compressed observation model, and the real photoelectric signal of the wafer to be tested is obtained by using a sparse signal reconstruction algorithm.

[0075] The sparse signal reconstruction algorithm includes L1 norm minimization, orthogonal matching pursuit, and iterative thresholding. The calculated real photoelectric signal can represent the PL (Photoluminescence) spectrum, current / voltage, etc. of the chip within the entire wafer area, providing key data support for applications such as high-throughput yield analysis, known good product screening, and uniformity analysis. This application adopts a compressed sensing algorithm, which, through sparse orthogonal encoding, requires far fewer acquisition times than full sampling times. Only fewer excitation frames than the number of pixels are needed to reconstruct the complete photoelectric signal, significantly reducing the number of sampling frames and transmission volume of photoelectric data, improving detection efficiency, enhancing detection signal strength and signal-to-noise ratio, and is suitable for wafer testing scenarios with small chip area, high array density, and weak signals.

[0076] Compressed sensing (CS) theory has demonstrated excellent performance in signal and image reconstruction and has been applied in fields such as hyperspectral imaging, infrared imaging, terahertz imaging, and medical imaging. Its advantage lies in the fact that, under the premise of sparsity, only a small number of measurements are needed to reconstruct high-quality signals, thereby effectively reducing the system sampling rate and data processing pressure. This application utilizes a compressed sensing reconstruction algorithm to accurately reconstruct the two-dimensional spectral and electrical signal distribution of the entire wafer from a small amount of observation data under low sampling rate conditions. This significantly reduces the number of samples and the amount of data while maintaining detection efficiency and spatial coverage, significantly improving the non-destructive high-throughput detection capability of the entire wafer.

[0077] The compressed observation model is based on compressed sensing theory, taking compressed sensing encoded patterns, photoluminescence signals, and photocurrent signals as inputs, and the actual photoelectric signals of the wafer under test as outputs. The compressed observation model is established as follows:

[0078] Based on compressed sensing theory, the following observation model is constructed using historical compressed sensing coded patterns, historical photoluminescence signals, and historical photocurrent signals:

[0079]

[0080] By combining K different encodings, a compressed observation model is constructed:

[0081]

[0082] Where λ represents wavelength, λ i For the i-th wavelength, Y k (λ) and Y(λ) i ) represents the historical photoluminescence signal and historical photocurrent signal excited by the historical compressed sensing coded pattern, M∈{0,1} K*N S is a historical compressed sensing encoding pattern. j (λ) and S(λ) i ) represents the actual photoelectric signal of the wafer, K represents the number of times the historical compressed sensing coded pattern was generated, and N represents the total number of pixels on the wafer.

[0083] Under each frame of structured optical coding excitation, corresponding optical and electrical signals can be acquired. This acquisition process can establish a standard compressed observation model, where the loaded modulation pattern can be regarded as a known modulation matrix; the photoelectric response obtained from each measurement constitutes the observation vector; and the actual spectral or electrical signal distribution within the measured area can be regarded as the target image to be reconstructed. Through a certain number of optical coding excitations, a complete compressed observation model is established based on the linear relationship between the modulation matrix and the measurement results.

[0084] The optoelectronic combined batch inspection method for LED wafers provided in this application transmits a light beam to a spatial light modulator for pattern modulation to obtain a compressed sensing coded pattern; the compressed sensing coded pattern is focused onto the surface of the wafer to be inspected, causing the wafer to generate photoluminescence and photocurrent signals; the photocurrent signal generated by the wafer is extracted through a flexible conductive layer; the photoluminescence signal generated by the wafer and the photocurrent signal extracted by the flexible conductive layer are collected; the compressed sensing coded pattern, the collected photoluminescence signal, and the photocurrent signal are input into a compressed observation model, and the real optoelectronic signal of the wafer is obtained using a sparse signal reconstruction algorithm. This method achieves high-speed, high-throughput, optoelectronic combined batch inspection of wafers without damaging the chip.

[0085] Because the solution in this application involves encoding and exciting the entire wafer, acquiring photoelectric signals, and reconstructing the actual photoelectric signals of the wafer, the method further includes the following steps after step S104:

[0086] The wafer to be tested is translated along a preset path, and then the process of transmitting the light beam to the spatial light modulator for pattern modulation is repeated to obtain a compressed sensing coded pattern, until all parts of the wafer to be tested have been processed.

[0087] Understandably, the compressed sensing coded pattern has a limited illumination area and cannot illuminate the entire wafer area at once. Therefore, after acquiring photoluminescence and photocurrent signals in the current part of the wafer, the wafer needs to be moved so that the compressed sensing coded pattern can illuminate the new part of the wafer and acquire the photoluminescence and photocurrent signals in the new part of the wafer, until the entire wafer under test has been illuminated by the compressed sensing coded pattern and the photoluminescence and photocurrent signals have been acquired.

[0088] See Figure 3 The present application provides a photoelectric combined batch inspection system for LED wafers, including a laser 1, a collimating lens 2, a spatial light modulator 3, a focusing microscope 4, a transparent cover plate 5, a wafer to be inspected 6, a flexible micro-nano electrode 7, a two-dimensional stage 8, a base 9, a ring optical fiber 10, a filter 11, a spectrometer 12, a digital source meter 13, a vacuum pump 14, a vacuum connecting tube 15, and a sample chamber 16.

[0089] The laser beam output from laser 1 is shaped into a uniform parallel beam by collimating lens 2 and transmitted to spatial light modulator 3 for pattern modulation, achieving coded excitation. The spatial light modulator 3 can be a DMD, which can output a compressed sensing coded pattern under control signal drive to achieve spatial modulation. The modulated beam is reflected and perpendicularly incident on focusing microscope 4, focusing onto the wafer 6 under test within sample cavity 16. (See also...) Figure 4 This is a schematic diagram of a compressed sensing coded pattern exciting a wafer under test. The top part shows the compressed sensing coded pattern, and the bottom part shows that each pixel on the wafer under test receives the excitation of the compressed sensing coded pattern, thereby generating photoluminescence signal and photocurrent signal.

[0090] A transparent cover plate sits atop a flexible micro / nano electrode. Under the pressure of the transparent cover plate, the wafer adheres uniformly to the flexible micro / nano electrode, ensuring non-destructive contact and effective extraction of photocurrent signals. Vacuum assistance can also be used to achieve uniform adhesion between the wafer and the flexible micro / nano electrode. A vacuum pump and vacuum connection tube remove gas from the sample chamber, creating a low-pressure environment between the transparent cover plate, the wafer, and the flexible micro / nano electrode. The transparent cover plate presses the wafer and electrode together under atmospheric pressure, ensuring uniform contact, improving adhesion quality, avoiding poor contact caused by air gaps, and more effectively and reliably extracting photocurrent signals.

[0091] The photoluminescence signal acquisition section includes a ring fiber 10, a filter 11, and a spectrometer 12, used to collect photoluminescence signals. The photoluminescence signal acquisition module consists of a ring-shaped distribution of the ring fiber 10, arranged around the wafer, enabling simultaneous acquisition of photoluminescence signals from multiple angles. After the photoluminescence signal passes through the filter 11 to remove excitation light interference, it enters the spectrometer 12 for spectral acquisition. The photoluminescence signal excitation simultaneously generates a photocurrent signal, which is extracted by the flexible micro / nano electrode 7 and recorded by the digital source meter 13.

[0092] The sample chamber 16 is placed on the two-dimensional stage 8, and combined with the bottom support base 9, the platform can be precisely displaced according to the coded sampling requirements and the optical imaging field of view under the control program instructions. This ensures that the entire wafer is uniformly covered and sampled within a limited number of samplings, realizing the overall movement and regional positioning of the wafer. The platform has high positioning accuracy, which facilitates alignment with the spatially coded modulated light field, thereby enabling batch inspection of each region in conjunction with the light field coding method.

[0093] The following section will provide a detailed explanation of the optoelectronic combined batch testing process for LED wafers.

[0094] S201, Encoded Pattern Loading and Spatial Modulation Illumination.

[0095] The spatial light modulator 3 loads a pre-designed Hadamard binary coding pattern (i.e., a compressed sensing coding pattern). This pattern is sparse and orthogonal, which can significantly reduce the number of modulations while achieving spatially structured excitation of the entire wafer area. As a spatial modulation mask for the light field, it can generate photoelectric responses when applied to different pixel units on the wafer to be detected. By spatially encoding and illuminating the entire wafer area through a series of binary modulation patterns, the photoluminescence responses of multiple pixels can be superimposed and read.

[0096] S202, synchronous acquisition of spectral and electrical signals.

[0097] This application simultaneously acquires parameters such as spectra and electrical signals, supporting photoelectric collaborative analysis. Under each frame of coded excitation, the chip within the irradiated area simultaneously generates photoluminescence and photocurrent signals. The photoluminescence signal is synchronously acquired from multiple angles by a ring fiber 10, filtered by a filter 11 to remove the excitation band, and then input into a spectrometer 12 for wavelength-resolved acquisition. The electrical signal is extracted through a flexible micro / nano electrode 7 and recorded in real time by a digital source meter 13, achieving synchronous acquisition of spectrum and current. After all coded patterns are irradiated, the irradiation frequency of each pixel unit is further statistically analyzed to evaluate the spatial uniformity and coverage of the coded pattern, providing reliable prior data for subsequent compression and reconstruction. Although a single frame of excitation covers a limited area, multiple frames of irradiation can ensure that all pixel units are excited. Ultimately, the irradiation frequency of most chip pixel units is concentrated in a similar range, indicating that the acquisition method of this application provides uniform spatial coverage, providing reliable prior data for subsequent reconstruction of photoelectric signals.

[0098] S203, Platform displacement and whole-area scan.

[0099] The computer-controlled two-dimensional stage 8 moves the sample chamber 16 sequentially along a preset grid path. Upon reaching a new region, steps S201 and S202 are repeated until the entire wafer is inspected within a limited number of sampling attempts. Through a collaborative mechanism of optical field encoding and precise platform movement, the entire wafer can be covered in sections and subjected to high-throughput, non-destructive batch inspection.

[0100] S204, Establishment of the compressed observation model.

[0101] Based on compressed sensing theory, the following observation model is constructed using historical compressed sensing coded patterns, historical photoluminescence signals, and historical photocurrent signals:

[0102]

[0103] By combining K different encodings, a compressed observation model is constructed:

[0104]

[0105] Where λ represents wavelength, λ i For the i-th wavelength, Y k (λ) and Y(λ) i ) represents the historical photoluminescence signal and historical photocurrent signal excited by the historical compressed sensing coded pattern, M∈{0,1} K*N S is a historical compressed sensing encoding pattern. j (λ) and S(λ) i( ) represents the actual photoelectric signal of the wafer, K represents the number of times the historical compressed sensing coded pattern was generated, and N represents the total number of pixels on the wafer. To achieve non-destructive batch photoelectric detection of the entire wafer under inspection, reduce data acquisition pressure, and obtain high-fidelity reconstructed structures under weak signal conditions, this application introduces compressed sensing theory for multimodal data reconstruction, solving the problem of insufficient performance of traditional methods under low signal-to-noise and small array conditions.

[0106] S205, Reconstruction of real photoelectric signals.

[0107] Multiple sets of collected compressed sensing coded patterns, photoluminescence signals, and photocurrent signals are input into the compressed observation model. A sparse signal reconstruction algorithm is used to reconstruct the signal, restoring the complete spatial distribution at each wavelength with high quality from a small number of observations.

[0108] Secondly, this application provides a photoelectric combined batch inspection device for LED wafers, the device comprising:

[0109] The modulation module is used to transmit the light beam to the spatial light modulator for pattern modulation to obtain a compressed sensing coded pattern.

[0110] The excitation module is used to focus the compressed sensing coding pattern onto the surface of the wafer to be inspected, so that the wafer to be inspected generates photoluminescence signal and photocurrent signal.

[0111] A conductive module is used to extract the photocurrent signal generated by the wafer under test through a flexible conductive layer;

[0112] The acquisition module is used to acquire the photoluminescence signal generated by the wafer under test and the photocurrent signal derived from the flexible conductive layer;

[0113] The reconstruction module is used to input the compressed sensing coding pattern, the acquired photoluminescence signal, and the photocurrent signal into the compressed observation model, and use a sparse signal reconstruction algorithm to obtain the real photoelectric signal of the wafer to be tested.

[0114] In one possible implementation, the modulation module is specifically used for:

[0115] The excitation light output from the laser is obtained, and the excitation light is input into the collimating lens for adjustment to obtain a uniform parallel beam.

[0116] The parallel beam is transmitted to a spatial light modulator for pattern modulation, and a compressed sensing coded pattern is formed under the drive of a preset Hadamard compressed sensing coded sequence or Walsh compressed sensing coded sequence.

[0117] In one possible implementation, the conductive module is specifically used for:

[0118] The wafer to be tested is placed above a flexible micro / nano electrode;

[0119] Pressure is applied to the wafer to be tested through a transparent cover plate, so that the lower surface of the wafer to be tested is tightly bonded to the upper surface of the flexible micro-nano electrode;

[0120] The photogenerated current signal is transmitted through the flexible micro / nano electrode and an external current acquisition circuit to form a path and is exported. The flexible micro / nano electrode is made of flexible material and has an array of micropillar conductive structures arranged on its surface.

[0121] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0122] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the apparatus embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0123] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for combined optoelectronic batch inspection of LED wafers, characterized in that, The method includes: The beam is transmitted to a spatial light modulator for pattern modulation to obtain a compressed sensing coded pattern. The compressed sensing coding pattern is focused onto the surface of the wafer to be inspected, so that the wafer to be inspected generates photoluminescence signal and photocurrent signal; The photocurrent signal generated by the wafer under test is extracted through a flexible conductive layer; The photoluminescence signal generated by the wafer under test and the photocurrent signal derived from the flexible conductive layer are collected. The compressed sensing coding pattern, the acquired photoluminescence signal, and the photocurrent signal are input into the compressed observation model, and the real photoelectric signal of the wafer to be tested is obtained by using a sparse signal reconstruction algorithm. The step of transmitting the light beam to a spatial light modulator for pattern modulation to obtain a compressed sensing coded pattern includes: The excitation light output from the laser is obtained, and the excitation light is input into the collimating lens for adjustment to obtain a uniform parallel beam. The parallel beam is transmitted to a spatial light modulator for pattern modulation, and a compressed sensing coded pattern is formed under the drive of a preset Hadamard compressed sensing coded sequence or Walsh compressed sensing coded sequence. The step of extracting the photocurrent signal generated by the wafer under test through the flexible conductive layer includes: The wafer to be tested is placed above a flexible micro / nano electrode; Pressure is applied to the wafer to be tested through a transparent cover plate, so that the lower surface of the wafer to be tested is tightly bonded to the upper surface of the flexible micro-nano electrode; The photogenerated current signal is transmitted through the flexible micro / nano electrode and an external current acquisition circuit to form a path and is exported. The flexible micro / nano electrode is made of flexible material and has an array of micropillar conductive structures arranged on its surface.

2. The method according to claim 1, characterized in that, The acquisition of the photoluminescence signal and photocurrent signal generated by the wafer under test includes: The photoluminescence signal generated by the wafer under test is collected by a ring fiber array surrounding the wafer; the collected signal is filtered to remove the excitation light and then acquired by a spectrometer. The photocurrent signal output by the flexible conductive layer is acquired through the external current acquisition circuit.

3. The method according to claim 1, characterized in that, After the step of acquiring the photoluminescence signal and photocurrent signal generated by the wafer under test, the method further includes: The wafer to be tested is translated along a preset path, and then the process of transmitting the light beam to the spatial light modulator for pattern modulation is repeated to obtain a compressed sensing coded pattern, until all parts of the wafer to be tested have been processed.

4. The method according to claim 1, characterized in that, The compressed observation model is established in the following way: Based on compressed sensing theory, the following observation model is constructed using historical compressed sensing coded patterns, historical photoluminescence signals, and historical photocurrent signals: By combining K different encodings, a compressed observation model is constructed: Where λ represents wavelength, λ i For the i-th wavelength, Y k (λ) and Y(λ) i ) represents the historical photoluminescence signal and historical photocurrent signal excited by the historical compressed sensing coded pattern, M∈{0,1} K*N S is a historical compressed sensing encoding pattern. j (λ) and S(λ) i ) represents the actual photoelectric signal of the wafer, K represents the number of times the historical compressed sensing coded pattern was generated, and N represents the total number of pixels on the wafer.

5. The method according to claim 1, characterized in that, The sparse signal reconstruction algorithm includes L1 norm minimization, orthogonal matching pursuit, and iterative thresholding algorithm.

6. A photoelectric combined batch inspection device for LED wafers, characterized in that, The device includes: The modulation module is used to transmit the light beam to the spatial light modulator for pattern modulation to obtain a compressed sensing coded pattern. The excitation module is used to focus the compressed sensing coding pattern onto the surface of the wafer to be inspected, so that the wafer to be inspected generates photoluminescence signal and photocurrent signal. A conductive module is used to extract the photocurrent signal generated by the wafer under test through a flexible conductive layer; The acquisition module is used to acquire the photoluminescence signal generated by the wafer under test and the photocurrent signal derived from the flexible conductive layer; The reconstruction module is used to input the compressed sensing coding pattern, the acquired photoluminescence signal and the photocurrent signal into the compressed observation model, and use the sparse signal reconstruction algorithm to obtain the real photoelectric signal of the wafer to be tested. The modulation module is specifically used for: The excitation light output from the laser is obtained, and the excitation light is input into the collimating lens for adjustment to obtain a uniform parallel beam. The parallel beam is transmitted to a spatial light modulator for pattern modulation, and a compressed sensing coded pattern is formed under the drive of a preset Hadamard compressed sensing coded sequence or Walsh compressed sensing coded sequence. The conductive module is specifically used for: The wafer to be tested is placed above a flexible micro / nano electrode; Pressure is applied to the wafer to be tested through a transparent cover plate, so that the lower surface of the wafer to be tested is tightly bonded to the upper surface of the flexible micro-nano electrode; The photogenerated current signal is transmitted through the flexible micro / nano electrode and an external current acquisition circuit to form a path and is exported. The flexible micro / nano electrode is made of flexible material and has an array of micropillar conductive structures arranged on its surface.

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