Patterning Wafer Defect Detection System and Method Based on Dual-Frequency Comb Spatiotemporal Coding

Abstract

The present invention discloses a patterned wafer defect detection system and method based on dual-comb spatio-temporal coding. The system includes: a dual-comb light source module, a spatial coding illumination module, a time programming control module, a signal acquisition and processing module, and a data analysis and processing module. The data analysis and processing module receives the restored three-dimensional topography information of the surface of the wafer to be measured, analyzes it, extracts defect-related features, establishes a mapping relationship between spectral features and defects, and identifies the surface defects of the wafer to obtain corresponding defect types and position information. The present invention adopts a wafer defect detection technology based on dual-comb spatio-temporal coding, uses dual-comb interference technology to achieve fast scanning and parallel detection, and greatly improves the detection efficiency. The present invention can obtain the absolute distance information of the wafer surface, and feeding this result back to the precision air-bearing motion platform can eliminate the autofocus optical path system and the feedback control part, improve the detection efficiency, and reduce the volume, complexity and cost of the entire wafer detection system.

Description

Technical Field

[0001] The present invention relates to the field of image technology, and particularly to a patterned wafer defect detection system and method based on dual-comb spatio-temporal coding. Background Art

[0002] As semiconductor processes continue to advance to 3 nm and more advanced processes, the structure of chips has become increasingly complex and three-dimensional, which poses higher challenges to defect detection technology. In these advanced processes, the structure on the wafer surface not only has a continuously shrinking lateral dimension but also an increasing aspect ratio in the vertical direction, resulting in the inability of traditional two-dimensional planar detection methods to meet the increasingly refined process control requirements.

[0003] Traditional two-dimensional detection technologies face many challenges, such as the cumbersome, time-consuming, and inefficient process of manual microscope detection, and the inability of optical planar imaging technology to provide depth information. Currently, the industry generally adopts scanning electron microscopes to scan and detect the entire wafer to obtain complete three-dimensional topography data of the wafer surface. However, this method has problems such as high detection costs, low efficiency, and is prone to causing electron beam damage to the wafer surface. Therefore, it is mainly applicable to offline defect detection with low efficiency requirements.

[0004] In view of this, in advanced processes, developing a new detection method that can quickly and accurately obtain the three-dimensional topography information of defects, while taking into account detection efficiency and sensitivity, is of crucial significance for improving the yield of chip manufacturing and reducing production costs. This new method not only needs to be able to accurately locate defects but also should provide detailed three-dimensional topography data for process optimization and quality control. Summary of the Invention

[0005] The present invention aims at the disadvantages in the prior art and provides a patterned wafer defect detection system and method based on dual-comb spatio-temporal coding.

[0006] To solve the above technical problems, the present invention is solved by the following technical solutions:

[0007] A patterned wafer defect detection system based on dual-comb spatio-temporal coding, comprising:

[0008] A dual-comb light source module that provides a signal optical comb and a reference optical comb;

[0009] A spatial encoding illumination module, comprising a spatial coupling unit, a dispersion beam splitting unit, a beam expanding unit, an encoding unit and an illumination receiving unit. The spatial coupling unit receives a signal optical comb and converts it into spatial light. The dispersion beam splitting unit performs multi-beam interference on the spatial light and longitudinally separates it, and then performs lateral dispersion expansion and enters the beam expanding unit. The encoding unit forms a two-dimensional spatial encoding light field. The illumination unit receives the two-dimensional spatial encoding light field and irradiates it on the surface of the wafer to form a reflection signal;

[0010] A time programming control module synchronously locks the reflection signal and a reference optical comb to form a time programming optical comb pair, measures the absolute distance information based on the time programming optical comb pair, and controls the relative time delay amount between the time programming optical comb pairs to form time domain beat frequency signals with different repetition frequencies;

[0011] A signal acquisition and processing module acquires the time domain beat frequency signals and extracts the spectral intensity information of the radio frequency comb, performs phase taking and phase unwrapping calculations on the spectral intensity information, obtains the phase information and combines it with the spectral intensity information to obtain the restored three-dimensional topography information of the wafer surface;

[0012] A data analysis and processing module receives the restored three-dimensional topography information of the surface of the wafer to be measured, identifies the defects on the wafer surface through a defect recognition model to obtain the corresponding defect types and spectral information, and determines the positions of the defects on the wafer surface based on a preset mapping relationship.

[0013] As an implementable manner, the spatial coupling unit includes a collimator, and the dispersion beam splitting unit includes a first beam splitter and a second beam splitter;

[0014] After passing through a circulator and a collimator, the signal optical comb is incident on the first beam splitter to form a first beam of light and a second beam of light;

[0015] The first beam of light forms a reflected light through a reference mirror as a distance reference. The second beam of light enters the beam expanding unit, passes through the encoding unit to form a two-dimensional spatial encoding light field and then irradiates on the wafer surface to form a reflection signal. The reflection signal successively enters the beam expanding unit, the circulator and the second beam splitter. The second beam splitter divides the reflection signal into a first reflection signal and a second reflection signal, and the first reflection signal enters an optical time phase discriminator.

[0016] As an implementable manner, the encoding unit successively includes a cylindrical lens, a virtual imaging phased array, a lens and a blazed grating. The second beam of light enters the beam expanding unit and then successively passes through the cylindrical lens, the virtual imaging phased array, the lens and the blazed grating to form a two-dimensional spatial encoding light field and form a reflection signal;

[0017] The virtual imaging phased array includes a first mirror and a second mirror. The reflectivity of the first mirror is 95%, the reflectivity of the second mirror is 99.9%, the distance between the first mirror and the second mirror is 1.686 mm, and the surface form accuracies of the first mirror and the second mirror are respectively ;

[0018] The number of rulings of the blazed grating is 1600 lines, and the diffraction efficiency is greater than 95%;

[0019] The free spectral range of the virtual imaging phased array is expressed as follows:

[0020]

[0021] Wherein, represents the free spectral range, represents the refractive index of the material, represents the incident angle of light with wavelength incident on the virtual imaging phased array, represents the wavelength, represents the time.

[0022] As an implementable embodiment, it further includes a beam splitting and combining unit, and the beam splitting and combining unit includes a third beam splitter and a combiner;

[0023] The third beam splitter divides the reference optical frequency comb into a first path of light and a second path of light. The first path of light enters the optical time discriminator and performs time discrimination with the first reflection signal through the optical time discriminator to obtain the absolute distance information of the entire wave packet;

[0024] The combiner receives the second path of light and the second reflection signal to form a time-domain beat frequency signal.

[0025] As an implementable embodiment, the time programming control module includes a digital locking controller, an optical time discriminator, and a dual optical frequency comb mutual scanning controller. The digital locking controller locks the key parameters of the time programming optical frequency comb pair to a common time reference, measures and then locks the repetition frequency and carrier envelope offset frequency of the time programming optical frequency comb pair;

[0026] The dual optical frequency comb mutual scanning controller adjusts the phase parameters of the programmable optical frequency comb to synchronize the reference optical frequency comb with the reflection signal and establish a programmable control phase relationship, obtaining the relative time delay amount between the reference optical frequency comb and the reflection signal;

[0027] The relative time delay amount is expressed as follows:

[0028]

[0029] Wherein, represents the relative time delay amount between the reference optical frequency comb and the signal optical frequency comb, and N represents the number of comb teeth, respectively represent the initial phases of the reference optical comb and the signal optical comb, respectively represent the phases of the Nth comb teeth of the reference optical comb and the signal optical comb, represents the repetition frequency of the optical comb.

[0030] As an implementable mode, it further includes a precision motion control module and an automatic loading and unloading module;

[0031] The precision motion control module controls the position of the wafer to be measured, and the automatic loading and unloading module clamps the wafer to be measured and places it on the precision air-bearing platform to realize automatic wafer loading and unloading.

[0032] As an implementable mode, for collecting the time-domain beat frequency signal, extracting the spectral intensity information of the radio frequency comb through Fourier transform; obtaining the phase information through phase unwrapping calculation, including the following steps:

[0033] Obtain the time-domain beat frequency signal, perform Fourier transform on the time-domain beat frequency signal to obtain the spectral intensity information of the radio frequency spectrum;

[0034] Perform phase extraction processing and unwrapping operation on the radio frequency spectrum to obtain the phase curve of the radio frequency spectrum, process the phase curve and the absolute position information of the wave packet to obtain the absolute position information of the two-dimensional space encoded optical field region, and combine the spectral intensity information to obtain the restored three-dimensional topography of the wafer surface;

[0035] Based on the restored three-dimensional topography of the wafer surface, calibrate the corresponding relationship between the spectral frequency and the spatial position to obtain the mapping relationship;

[0036] Among them, the time-domain beat frequency signal , is expressed as follows:

[0037]

[0038] 、 respectively represent the electric fields of the signal optical comb and the reference optical comb, represents the beat frequency, that is, the repetition frequency difference between the reference light and the signal light, represents the phase information, represents the phase difference, represents the time;

[0039] Perform Fourier transform on the time-domain beat frequency signal , to obtain the radio frequency spectrum, which is expressed as follows:

[0040]

[0041] Among them, represents the frequency domain index, represents the total number of sampling points, represents the imaginary unit, represents the th sampling point of the time-domain beat frequency signal, represents the th sampling point. Each comb tooth corresponds to a different position in the two-dimensional spectral space coding region, and the intensity reflects the reflectivity at that position. Combining the comb tooth interval and the free spectral range FSR of the spectroscopic device to segment the spectrum, an intensity image of the illuminated area is obtained;

[0042] Performing a phase-taking process and an unwrapping operation on the radio frequency spectrum, which is expressed as follows:

[0043]

[0044]

[0045] represents rounding down, , represents the phase after unwrapping;

[0046] The mapping relationship is expressed as follows:

[0047]

[0048] Among them, represents the spatial coordinate, respectively represent the spatial coordinate positions, represents the proportionality coefficient, represents the optical wavelength, represents the offset.

[0049] As an implementable manner, the restored three-dimensional topography information of the surface of the wafer to be measured is received and analyzed, and defect-related features are extracted, including the following steps:

[0050] Differencing the restored three-dimensional topography of the wafer to be measured in the current area with the restored three-dimensional topography of the wafer in the adjacent area to obtain random defects on the wafer surface, and determining the shape information and position information of the random defects through the random defects;

[0051] By differencing the restored three-dimensional topography of the wafer to be measured with the topography of the standard sample, systematic defects on the surface of the wafer to be measured are obtained, and the shape information and position information of the systematic defects are determined based on the systematic defects;

[0052] The random defects on the wafer surface are expressed as follows:

[0053]

[0054] The systematic defects on the surface of the wafer to be measured are expressed as follows:

[0055]

[0056] Among them, respectively represent the position coordinates of each point on the wafer to be measured, represents the spectral intensity information at the corresponding point, is the weight function of adjacent regions, represents the restored three-dimensional topography, represents the restored three-dimensional topography of the wafer in the adjacent region, represents random defects on the wafer surface, represents the topography of the standard sample, represents systematic defects on the surface of the wafer to be measured, represents the wavelength-dependent calibration coefficient, represents the wavelength.

[0057] As an implementable manner, identifying the defects on the wafer surface to obtain the corresponding defect types includes the following steps:

[0058] Obtain the normal wafer image and the spectral data of various defect types, and the spectral data of various defect types include surface scratches, particle contamination, bridging, and pattern missing;

[0059] Perform category marking on various defect types to form a marked data set;

[0060] Construct a defect recognition pre-training model and train it based on the marked data set, and adjust the parameters based on the loss function, and then obtain the defect recognition model. Among them, the defect recognition pre-training model is constructed based on a convolutional neural network capable of extracting local spatial features;

[0061] Based on transfer learning, fuse geometric features and spectral features; based on the mapping relationship, map the spatial position of the spectral data to the actual wafer coordinates, and mark the defect area according to the defect classification result after spectral processing;

[0062] The loss function is expressed as follows:

[0063]

[0064] Among them, represents the number of defect categories, is the regularization coefficient, are the true label and the prediction result respectively, represents the defect type data, represents the phase offset.

[0065] A method for detecting patterned wafer defects based on dual-comb spatio-temporal coding, implemented by a system for detecting patterned wafer defects based on dual-comb spatio-temporal coding. The system includes a dual-comb light source module, a spatial coding illumination module, a time programming control module, a signal acquisition and processing module, and a data analysis and processing module, and includes the following steps:

[0066] Obtain the signal optical comb and the reference optical comb provided by the dual-comb light source module;

[0067] The spatial coupling unit receives the signal optical comb and converts it into spatial light. The dispersion and splitting unit performs multi-beam interference on the spatial light and longitudinally separates it, and then performs lateral dispersion expansion and enters the beam expansion unit. The coding unit forms a two-dimensional spatial coding light field, and the illumination unit receives the two-dimensional spatial coding light field and irradiates it on the wafer surface to form a reflection signal;

[0068] Synchronously lock the reflection signal and the reference optical comb to form a time-programmed optical comb pair. Based on the time-programmed optical comb pair and perform time measurement to obtain absolute distance information, and control the relative time delay amount between the time-programmed optical comb pairs to form time-domain beat frequency signals with different repetition frequencies;

[0069] The signal acquisition and processing module acquires the time-domain beat frequency signal and extracts the spectral intensity information of the radio frequency comb, performs phase extraction and phase unwrapping calculations on the spectral intensity information, obtains the phase information and combines it with the spectral intensity information to obtain the restored three-dimensional topography information of the wafer surface;

[0070] The data analysis and processing module receives the restored three-dimensional topography information of the surface of the wafer to be measured and identifies the wafer surface defects through a defect recognition model to obtain the corresponding defect types and spectral information, and determines the positions of the wafer surface defects based on a preset mapping relationship.

[0071] Due to the adoption of the above technical solutions, the present invention has significant technical effects:

[0072] Optical frequency combs, as ultra-precise "optical rulers" in the time domain and frequency domain, have become ideal light sources for precision measurement. They not only have the accuracy traceable to the frequency reference, but also have the ability of multi-channel multiplexing, which is the basis for realizing high-throughput parallel optical detection. Optical frequency combs cover a wide spectral range, from ultraviolet to infrared and even terahertz bands. The broadband characteristics allow simultaneous detection of various types of material defects. At the same time, using the precise time-frequency correspondence relationship of optical frequency combs, the positions of defects can be accurately located and their sizes or depths can be quantified. Whether it is surface scratches, contamination or internal structural discontinuities, a comprehensive assessment can be carried out.

[0073] The present invention applies dual-comb spatio-temporal coding to wafer defect detection. By using the dual-comb spatio-temporal coding technology, rapid scanning and parallel detection are realized, significantly improving the detection efficiency; while increasing the detection bandwidth, the equipment cost is reduced.

[0074] The present invention can obtain the absolute distance information of the wafer surface. Feeding this result back to the precision air-bearing motion platform can eliminate the autofocus optical path system, thereby improving the detection efficiency and reducing the volume, complexity, and cost of the entire wafer detection system. By combining the spatio-temporal coding technology with the wide-spectrum characteristics of the optical frequency comb, it is possible to flexibly adjust the detection strategy according to different types of wafers and defect characteristics, and detect various types of defects, including surface scratches, particle contamination, pattern defects, etc., with strong flexibility.

[0075] It also combines machine learning algorithms to intelligently analyze the spectrum, realizing automated defect identification, classification, and localization. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0077] Figure 1 is a schematic diagram of the overall framework of the system of the present invention;

[0078] Figure 2 is a schematic diagram of the overall process of the method of the present invention;

[0079] Figure 3 is a schematic diagram of a patterned wafer defect detection system based on dual optical frequency comb spatio-temporal coding of the present invention;

[0080] Figure 4 is a schematic diagram of the spatial coding illumination module in a patterned wafer defect detection system based on dual optical frequency comb spatio-temporal coding of the present invention;

[0081] Figure 5 is Figure 4 a schematic diagram of the generated two-dimensional light spot;

[0082] Figure 6 is a schematic diagram of the spatial coding illumination light spot scanning in a patterned wafer defect detection method based on dual optical frequency comb spatio-temporal coding of the present invention;

[0083] Figure 7 is a schematic diagram of the time programming control in a patterned wafer defect detection system based on dual optical frequency comb spatio-temporal coding of the present invention;

[0084] Figure 8 is a schematic diagram of the decoding and processing flow of the dual optical frequency comb interference signal in the data analysis and processing module in a patterned wafer defect detection method based on dual optical frequency comb spatio-temporal coding of the present invention;

[0085] Figure 9 It is a schematic diagram of the differential extraction and processing flow of defect feature signals in the data analysis and processing module of the patterned wafer defect detection method based on dual-comb spatio-temporal coding of the present invention;

[0086] Figure 10 It is a schematic diagram of the intelligent defect classification and positioning process in the data analysis and processing module of the patterned wafer defect detection method based on dual-comb spatio-temporal coding of the present invention. Specific embodiments

[0087] The present invention will be further described in detail below in conjunction with embodiments. The following embodiments are explanations of the present invention, and the present invention is not limited to the following embodiments.

[0088] Embodiment 1:

[0089] A patterned wafer defect detection system based on dual-comb spatio-temporal coding includes a dual-comb light source module, a spatial coding illumination module, a time programming control module, a signal acquisition and processing module, and a data analysis and processing module;

[0090] The dual-comb light source module provides a signal optical comb and a reference optical comb;

[0091] The spatial coding illumination module includes a spatial coupling unit, a dispersion spectroscopy unit, a beam expansion unit, a coding unit, and an irradiation and reception unit. The spatial coupling unit receives the signal optical comb and converts it into spatial light. The dispersion spectroscopy unit performs multi-beam interference on the spatial light and longitudinally separates it, and then performs lateral dispersion expansion and enters the beam expansion unit. The coding unit forms a two-dimensional spatial coding light field. The irradiation unit receives the two-dimensional spatial coding light field and irradiates it on the wafer surface to form a reflection signal. Among them, the reflection signal has the reflectivity and depth information of the wafer surface;

[0092] The time programming control module includes a digital lock controller, an optical time phase discriminator, and a dual-comb mutual sweep controller. The digital lock controller synchronizes and locks the reflection signal and the reference optical comb to form a time programming optical comb pair. The optical time phase discriminator receives the time programming optical comb pair and performs time measurement to obtain absolute distance information. The dual-comb mutual sweep controller controls the relative time delay amount between the time programming optical comb pairs to form a time-domain beat frequency signal with different repetition frequencies;

[0093] The signal acquisition and processing module acquires the time-domain beat frequency signal, extracts the spectral intensity information of the radio frequency comb through Fourier transform, performs phase extraction and phase unwrapping calculations on the spectral intensity information, obtains the phase information, and combines it with the spectral intensity information to obtain the restored three-dimensional topography information of the wafer surface;

[0094] The data analysis and processing module receives the restored three-dimensional topography information of the surface of the wafer to be tested, and uses a defect recognition model to identify the defects on the wafer surface to obtain the corresponding defect types and spectral information. Based on a preset mapping relationship, the positions of the defects on the wafer surface are determined. Among them, the defect-related features include geometric features, spectral features, and reflection and absorption features.

[0095] In the actual operation process, the detection system used is as Figure 3 shown, including a dual-comb mutual scanning controller 1, a reference optical comb 2, a digital locking controller 3, a signal optical comb 4, a third optical fiber beam splitter 5, an optical time phase discriminator 6, an optical fiber combiner 7, a second optical fiber beam splitter 8, an optical fiber circulator 9, a collimator 10, a first optical fiber beam splitter 11, a reference mirror 12, an expanding system 13, a photodetector 14, a two-dimensional spectral space encoding module 15, a programmable gate array 16, an objective lens 17, a computer 18, a precision air-bearing motion platform 19, and a robotic arm 20. Here, the optical fiber beam splitter is the beam splitter mentioned, and the optical fiber combiner is the combiner mentioned.

[0096] The provided signal optical comb 4 is the signal light. After receiving the signal optical comb 4, it enters the optical fiber circulator 9 and then is output as spatial light through the collimator 10. The spatial light is split into two beams of light by the first optical fiber beam splitter 11. One beam of light forms a reflected light after passing through the reference mirror 12 and returns along the original path. The other beam of light enters the two-dimensional spectral space encoding module 15 through the expanding system 13 to form a two-dimensional spatial encoded light field, and then is focused by the objective lens 17 and irradiated on the wafer to be tested to form a reflected signal. The reflected signal enters the second optical fiber beam splitter 8 through the optical fiber circulator 9 and is split into two beams of light. One beam of light (i.e., the reflected signal) enters the optical time phase discriminator 6, and the other beam of light enters the photodetector 14 through the optical fiber combiner 7. The provided reference optical comb 2 is the detection light. After receiving the reference optical comb 2, it is split into two beams of light by the third optical fiber beam splitter 5. One beam of light enters the optical time phase discriminator 6, and the other beam of light enters the photodetector 14 through the optical fiber combiner 7.

[0097] The optical time phase discriminator 6 receives one beam of reflected signal and one beam of light to obtain an attosecond-precision time phase discrimination , and then obtains the high-precision absolute position information of the wafer , which is expressed as follows:

[0098]

[0099] Among them, represents the time phase discrimination, represents the absolute position information, represents the speed of light, the signal light and the detection light form a beat frequency signal on the photodetector 14, down-convert the optical frequency signal to the radio frequency band, and collect the beat frequency time-domain signal through the photodetector 14 , after entering the programmable gate array 16, Fourier transform, phase extraction, and phase unwrapping calculations are performed to obtain phase information, which is combined with spectral intensity information to obtain the restored three-dimensional topography information of the wafer surface, and then input into the computer 18.

[0100] By combining the absolute distance information of the optical time discriminator 6 and the relative position information of each part of the entire coding area obtained by the programmable gate array 16 in the computer 18, the three-dimensional object topography of the coding area can be quickly and accurately reconstructed, realizing accurate identification and positioning of defects.

[0101] By controlling the precision air-bearing motion platform 19 to drive the wafer to move, rapid and high-precision scanning of the wafer surface can be achieved. The absolute position information of the wafer calculated by the computer 18 can be used to determine whether the wafer is located at the focal position of the objective lens 17. Scanning in the Z direction by the displacement platform can ensure that the wafer is always located at the objective lens focus during the scanning process.

[0102] In one embodiment, the time-programmable optical frequency comb meets the following requirements: a fiber mode-locked femtosecond optical frequency comb is selected, with a repetition frequency of 100 MHz, a central wavelength of 780 nm after passing through the frequency doubling module, and a spectral range of 15 nm. The output pulse of the optical frequency comb , the pulse envelope , where and respectively represent the phase offset and time offset of the optical frequency comb pulse, represents the offset phase, represents the th pulse complex amplitude. By using two phase-locked loops, arbitrary settings of and can be achieved. represents time, represents the carrier envelope, represents the reciprocal of the repetition frequency, and i represents the imaginary unit.

[0103] The digital lock controller uses phase-locked loop (PLL) technology to lock the key parameters of the two optical frequency combs to a common reference source (such as a CW laser), measures the repetition frequencies and the carrier envelope offset frequency of the two optical frequency combs. One optical frequency comb is used as the master optical frequency comb, and the other is used as the slave optical frequency comb. The parameters of the slave optical frequency comb are adjusted through the dual optical frequency comb cross-scan controller to synchronize it with the master optical frequency comb and establish a stable phase relationship, thereby achieving coherence between the two optical frequency combs and establishing an accurate frequency relationship, providing a stable frequency reference, eliminating system drift, finally obtaining a stable dual optical frequency comb system, achieving sub-hertz frequency accuracy, and thus performing high-precision spectral measurement.

[0104] The optical time discriminator is a polarization-maintaining fiber-based Mach-Zehnder interferometer, which can accurately identify the time difference between two pulses, thereby obtaining high-precision distance position information.

[0105] The two-dimensional spectral space encoding module is composed of optical dispersion elements, such as Figure 4 and Figure 5 As shown, in one embodiment, it includes a cylindrical lens 301, a VIPA 302, a lens 303, and a grating 304. Figure 4 in represents the incident angle of light with a wavelength of incident on the virtual imaging phased array. The VIPA can be used as a longitudinal dispersion spectroscope element. The reflectivities of the two mirrors in the cavity are 95% and 99.9% respectively. The distance between the two mirrors is 1.686 mm, and the surface accuracy is . Preferably, a blazed grating can be used as a transverse spectroscope device, with 1600 lines per millimeter and a diffraction efficiency > 95%.

[0106] The dual optical frequency comb mutual scanning controller is used to achieve precise control of the repetition frequencies of the two optical frequency combs, so as to realize a measurement with a flexible selection of the dual optical frequency comb spectral acquisition mode as shown in Figure 7 .

[0107] The precision air-bearing motion platform 19 uses a marble base to reduce the conduction of low-frequency vibrations. An anti-vibration device is arranged under the base, including but not limited to foundation reinforcement and foundation vibration isolation; the base is supported by air-bearing vibration isolation supports and an active vibration isolation platform above it to ensure that the influence of vibrations at sensitive frequencies during measurement is within a reasonable range. An air-bearing guide rail is provided on the air-bearing vibration isolation support. The wafer is driven by the output power of a linear motor and moves along the air-bearing guide rail, greatly reducing the friction of the platform movement and effectively improving the positioning accuracy and movement smoothness. In one embodiment, the precision air-bearing motion platform meets the following requirements: repeat positioning accuracy: ±50 nm / 300 mm, horizontal straightness: ±0.1 μm / 300 mm, vertical straightness: ±0.1 μm / 300 mm, positioning jitter: ±5 nm.

[0108] The robotic arm 20 is located directly in front of the precision air-bearing motion platform and is used to clamp the wafer to be detected and quickly and smoothly place the wafer accurately on the precision air-bearing motion platform to achieve automatic wafer loading and unloading. The robotic arm 20 can rotate over a large range, move vertically over a long distance, and extend in length to meet the requirement of moving the wafer to be measured from the production line cassette to the precision air-bearing motion platform.

[0109] Embodiment 2:

[0110] A method for detecting patterned wafer defects based on dual-comb spatio-temporal coding, realized by a system for detecting patterned wafer defects based on dual-comb spatio-temporal coding. The system includes a dual-comb light source module, a spatial coding illumination module, a time programming control module, a signal acquisition and processing module, and a data analysis and processing module. As Figure 2 shown, it includes the following steps:

[0111] S100. Obtain the signal optical comb and the reference optical comb provided by the dual-comb light source module;

[0112] S200. The spatial coupling unit receives the signal optical comb and converts it into spatial light. The dispersion and splitting unit performs multi-beam interference on the spatial light and longitudinally separates it, and then performs lateral dispersion expansion and enters the beam expansion unit. The coding unit forms a two-dimensional spatial coding light field. The illumination receiving unit receives the two-dimensional spatial coding light field and irradiates it on the wafer surface to form a reflection signal, where the reflection signal has the reflectivity and depth information of the wafer surface;

[0113] S300. The digital lock controller synchronizes and locks the reflection signal and the reference optical comb to form a time-programmed optical comb pair. The optical time discriminator receives the time-programmed optical comb pair and performs time measurement to obtain the absolute distance information. The dual-comb mutual sweep controller controls the relative time delay amount between the time-programmed optical comb pairs to form a time-domain beat frequency signal with different repetition frequencies;

[0114] S400. The signal acquisition and processing module acquires the time-domain beat frequency signal, extracts the spectral intensity information of the radio frequency comb through Fourier transform, performs phase extraction and phase unwrapping calculations on the spectral intensity information, obtains the phase information and combines it with the spectral intensity information to obtain the restored three-dimensional topography information of the wafer surface;

[0115] S500. The data analysis and processing module receives the restored three-dimensional topography information of the surface of the wafer to be measured and identifies the defects on the wafer surface through a defect recognition model to obtain the corresponding defect types and spectral information. Based on the preset mapping relationship, the positions of the defects on the wafer surface are determined, where the defect-related features include geometric features, spectral features, and reflection and absorption features.

[0116] In the actual operation process, it can be realized through the following steps, specifically:

[0117] Step 1: Place the wafer to be measured on the precision air-bearing platform based on the automatic loading module. The specific steps are as follows: Take out the wafer to be measured in the wafer cassette through the robotic arm, and after steps such as grasping, rotating, lifting, and telescoping, quickly and steadily place it on the measurement table of the precision air-bearing motion platform.

[0118] Step 2: Through the linkage of the spatial coding illumination module and the precision air-bearing motion platform, perform area scanning detection on the wafer to be measured, specifically including:

[0119] 1) First, ensure that the detection device is correctly installed and calibrated, and adjust the position of the wafer to be measured so that it is within the range of two-dimensional spectral spatial encoding illumination.

[0120] 2) The provided signal optical comb 4 serves as the signal light. After receiving the signal optical comb 4, it enters the fiber optic circulator 9 and then is output as spatial light through the collimator 10. The spatial light is split into two beams by the first fiber optic beam splitter 11. One beam forms a reflected light after passing through the reference mirror 12 and returns along the original path, and the other beam enters the two-dimensional spectral spatial encoding module 15 through the beam expansion system 13 to form a two-dimensional spatial encoded light field, which can be understood as the two-dimensional light spot shown here. Then, it is focused by the objective lens 17 and irradiates the wafer to be measured to form a reflected signal. Figure 5 6) After the reflected light returns along the original path and is received by the fiber optic circulator 9, it is split into two beams by the second fiber optic beam splitter 8. One beam enters the optical time discriminator 6, and the other beam enters the fiber optic combiner 7.

[0121] 3) After the reflected light returns along the original path and is received by the fiber optic circulator 9, it is split into two beams by the second fiber optic beam splitter 8. One beam enters the optical time discriminator 6, and the other beam enters the fiber optic combiner 7.

[0122] 4) After the output light of the reference optical comb 2 passes through the fiber optic beam splitter 1, one beam enters the optical time discriminator 6 to perform time discrimination with the returned light of the signal optical comb 4, thereby obtaining the high-precision absolute distance information of the entire wave packet. The absolute distance information is fed back to the precision air-bearing motion platform 19 through the computer 18 for automatic focusing in the vertical direction. The other beam forms a time-domain beat frequency signal on the photodetector 14 through the fiber optic combiner 7 and the other returned signal of the signal optical comb 4.

[0123] Step 3: Through the signal acquisition and processing module, collect the dual-comb time-domain interference signal, and extract the radio frequency spectrum intensity and phase information. As shown below, specifically: Figure 8 as follows:

[0124] 31) The time-domain beat frequency signal obtained in Step 2 is stored and processed by the programmable gate array 16.

[0125] 32) After the dual-comb time-domain interference signal undergoes Fourier transform (FFT), a radio frequency spectrum is obtained. Each tooth of the comb corresponds to a different position in the two-dimensional spectral spatial encoding region, and its intensity reflects the reflectivity of that position. By combining the comb tooth interval and the free spectral range FSR of the beam splitting device to perform spectral segmentation processing, the intensity image of the illumination region can be obtained, that is, the spectral intensity information can be obtained. The number of horizontal and vertical pixels of the image is determined by the free spectral range of the beam splitting device. Preferably, VIPA is selected as the beam splitting element, and its free spectral range is , the repetition frequency of the optical comb , the bandwidth , the number of horizontal pixels , the number of vertical pixels . The total number of pixels , that is, a single field of view consists of 90,000 parallel imaging foci, greatly improving the detection throughput.

[0126] 33) Perform phase extraction and phase unwrapping operations on the radio frequency spectrum to obtain the phase curve of the radio frequency spectrum, which reflects the relative position information of different points in the two-dimensional spectral spatial encoding region, that is, the depth information of different points. Combine with the absolute position information of the wave packet obtained in step 202 , and the absolute position information of the entire two-dimensional spectral spatial encoding region can be obtained , combined with the spectral intensity information obtained in the previous step , the three-dimensional topography of the wafer surface can be restored .

[0127] 34) Use a single-frequency laser and a standard resolution target (USAF 1951) to calibrate the correspondence between the spectral frequency and the spatial position.

[0128] Step Four: Take the difference between the test results and the results of the adjacent region and the standard sample to extract random defect and systematic defect information. The specific steps are as follows:

[0129] 41) By taking the difference between the three-dimensional topography test results of the wafer to be measured and the adjacent region , extract the shape and position information of the random defects on the wafer surface ; ;

[0130] 42) By taking the difference between the three-dimensional topography test results of the wafer to be measured and the standard sample , extract the shape and position information of the systematic defects on the wafer surface ; .

[0131] Step Five: Through the analysis of the spectral data, extract the corresponding relationship between the geometric features (such as depth, size, shape, etc.) and spectral features (such as waveform, abnormal peaks, etc.) related to the defects. The results are as Figure 9 shown. The specific steps include:

[0132] 51) Collect spectral data of normal wafer samples and various defects including surface scratches, particle contamination, bridging, pattern missing, etc.;

[0133] 52) Perform category marking on different defect types to ensure the balance of the dataset;

[0134] 53) Divide the training set (70%), validation set (20%) and test set (10%) to avoid data leakage.

[0135] Step 6: Based on methods such as machine learning and deep learning, establish the mapping relationship between spectral features and defects through learning a large number of labeled samples, and achieve fast automatic identification, classification, and localization of defects. As Figure 10 shown, the specific steps include:

[0136] 61) Select a convolutional neural network (CNN) suitable for extracting local spatial features for construction and training;

[0137] 62) Use the test set to evaluate the accuracy, precision, and confusion matrix of the model;

[0138] 63) Use transfer learning, pre-train on ImageNet and then fine-tune to improve the classification accuracy. Fuse geometric features and spectral features to enhance the learning ability;

[0139] 64) Map the spatial position of the spectral data to the actual wafer coordinates. Mark the defect area according to the defect classification result after spectral processing.

[0140] Based on methods such as machine learning and deep learning, combined with the established mapping relationship, and combined with the dataset collected in this solution, it is not only possible to identify and classify various types of defects, including surface scratches, particle contamination, pattern defects, etc., but also obtain the specific position information on the wafer to be tested according to the mapping relationship. That is to say, this application can obtain accurate defect classification and position information, providing accurate data for some subsequent work.

[0141] 65) After the above steps are completed, move the wafer to the next scanning area according to the preset scanning direction as Figure 6 shown. The advantage of this scanning method is that it can achieve dense paving scanning of the wafer surface. Repeat steps 2 to 6 until the detection of the corresponding wafer is completed.

[0142] All changes and modifications made without departing from the spirit and scope of the present invention, all equivalent technical solutions also fall within the scope of the present invention.

[0143] Each embodiment in this specification is described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same and similar parts among the embodiments can be referred to each other.

[0144] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, an apparatus, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0145] The present invention is described with reference to the flowcharts and / or block diagrams of methods, terminal devices (systems), and computer program products according to the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing terminal devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing terminal devices generate a device for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or a plurality of flows and / or blocks

[0146] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing terminal device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in Figure 1 one or more of the flows Figure 1 or a plurality of flows and / or blocks

[0147] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device, such that a series of operation steps are executed on the computer or other programmable terminal device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable terminal device provide steps for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or a plurality of flows and / or blocks

[0148] It should be noted that:

[0149] The phrase "an embodiment" or "embodiments" mentioned in the specification means that the specific features, structures, or characteristics described in connection with the embodiments are included in at least one embodiment of the present invention. Therefore, the phrases "an embodiment" or "embodiments" that appear throughout the specification do not necessarily all refer to the same embodiment.

[0150] In addition, it should be noted that for the specific embodiments described in this specification, the shapes, names, etc. of the components can be different. Any equivalent or simple changes made according to the structure, features, and principles described in this invention patent concept are included in the protection scope of this invention patent. Those skilled in the technical field to which this invention pertains can make various modifications, supplements, or use similar methods for substitution to the specific embodiments described, as long as they do not deviate from the structure of this invention or exceed the scope defined by this claims, they should all fall within the protection scope of this invention.

Claims

1. A patterned wafer defect detection system based on dual-comb spatiotemporal encoding, characterized in that: include: Dual-comb light source module, providing signal light comb and reference light comb; The spatial coding illumination module includes a spatial coupling unit, a dispersion spectrometer, a beam expansion unit, a coding unit and an illumination receiving unit. The spatial coupling unit receives the signal light comb and converts it into spatial light. The dispersion spectrometer performs multi-beam interference on the spatial light and separates it longitudinally and then performs transverse dispersion expansion before entering the beam expansion unit. The coding unit forms a two-dimensional spatial coding light field. The illumination receiving unit receives the two-dimensional spatial coding light field and irradiates it on the wafer surface to form a reflection signal. The spatial coupling unit includes a collimator, and the dispersion splitting unit includes a first beam splitter and a second beam splitter; After passing through the circulator and the collimator, the signal light comb is incident on the first beam splitter to form a first beam of light and a second beam of light; The first beam of light passes through a reference mirror to form reflected light as a distance reference. The second beam of light enters a beam expansion unit and passes through a coding unit to form a two-dimensional spatial coded light field, which is then irradiated on the surface of the wafer to form a reflected signal. The reflected signal enters the beam expansion unit, the circulator, and the second beam splitter in sequence. The second beam splitter divides the reflected signal into a first reflected signal and a second reflected signal. The first reflected signal enters an optical time phase detector. It also includes a light splitting and beam combining unit, which includes a third beam splitter and a beam combiner; The third beam splitter splits the reference light comb into a first light path and a second light path. The first light path enters the optical time phase detector and is time-phased with the first reflected signal through the optical time phase detector to obtain the absolute distance information of the entire wave packet. The beam combiner receives the second light and the second reflected signal, thereby forming a time domain beat signal; A time programming control module receives the reflected signal and synchronizes the reflected signal with a reference optical comb to form a time programming optical comb pair, performs time measurement based on the time programming optical comb pair to obtain absolute distance information, controls the relative time delay between the time programming optical comb pairs, and forms a time domain beat frequency signal with different repetition frequencies; The time programming control module includes a digital locking controller, an optical time phase detector and a dual optical comb mutual scanning controller. The digital locking controller locks the key parameters of the time programming optical comb pair to a common time reference, measures the repetition frequency and carrier envelope offset frequency of the time programming optical comb pair, and then locks them; The dual optical comb mutual scanning controller adjusts the phase parameters of the programmable optical comb, so that the reference optical comb is synchronized with the reflected signal and a programmable controllable phase relationship is established, thereby obtaining the relative time delay between the reference optical comb and the reflected signal; The relative time delay is expressed as follows: in, represents the relative time delay between the reference optical comb and the signal optical comb, N represents the number of comb teeth, , represent the initial phases of the reference optical comb and the signal optical comb respectively, , represent the phase of the Nth comb tooth of the reference light comb and the signal light comb respectively, represents the repetition frequency of the optical comb; The signal acquisition and processing module collects the time-domain beat frequency signal and extracts the spectral intensity information of the RF comb, performs phase extraction and unwrapping calculations on the spectral intensity information, obtains the phase information and combines it with the spectral intensity information to obtain the restored three-dimensional morphology information of the wafer surface; The data analysis and processing module receives the restored three-dimensional morphology information of the wafer surface to be tested and identifies the defects on the wafer surface through the defect recognition model to obtain the corresponding defect types and spectral information, and determines the location of the defects on the wafer surface based on the preset mapping relationship.

2. The patterned wafer defect detection system based on dual-comb spatiotemporal encoding according to claim 1, characterized in that: The encoding unit includes a cylindrical lens, a virtual imaging phased array, a lens and a blazed grating in sequence. The second light beam enters the beam expansion unit and then passes through the cylindrical lens, the virtual imaging phased array, the lens and the blazed grating in sequence to form a two-dimensional spatial encoding light field and a reflection signal. The virtual imaging phased array includes a first mirror and a second mirror, wherein the reflectivity of the first mirror is 95%, the reflectivity of the second mirror is 99.9%, the distance between the first mirror and the second mirror is 1.686 mm, and the surface accuracy of the first mirror and the second mirror is respectively ; The number of lines of the blazed grating is 1600, and the diffraction efficiency is greater than 95%; The free spectral range of the virtual imaging phased array is expressed as follows: in, The self-expression is represented by the spectral range, represents the refractive index of the material, The wavelength is The incident angle of the light incident on the virtual imaging phased array, represents the wavelength, Indicates time.

3. The patterned wafer defect detection system based on dual-comb spatiotemporal encoding according to claim 1, characterized in that: It also includes precision motion control module and automatic loading and unloading module; The precision motion control module controls the position of the wafer to be tested, and the automatic loading and unloading module clamps the wafer to be tested and places the wafer to be tested on the precision air floating platform to realize automatic loading and unloading.

4. The patterned wafer defect detection system based on dual-optical comb spatiotemporal encoding according to claim 1, characterized in that: The method of collecting the time domain beat frequency signal and extracting the spectral intensity information of the radio frequency comb; and obtaining the phase information by performing phase unwrapping calculation comprises the following steps: Acquire a time-domain beat frequency signal, and perform Fourier transform on the time-domain beat frequency signal to obtain spectral intensity information of a radio frequency spectrum; Perform phase processing and unwrapping operations on the RF spectrum to obtain the phase curve of the RF spectrum. Process the phase curve and the absolute position information of the wave packet to obtain the absolute position information of the two-dimensional spatially encoded light field area, and combine it with the spectral intensity information to obtain the restored three-dimensional morphology of the wafer surface. Based on the restored three-dimensional morphology of the wafer surface, the correspondence between the spectral frequency and the spatial position is calibrated to obtain a mapping relationship; Wherein, the time domain beat frequency signal , which is expressed as follows: , denote the electric fields of the signal light comb and the reference light comb respectively, It represents the beat frequency, i.e. the difference in repetition frequency between the reference light and the signal light. Represents phase information, represents the phase difference, represents a proportional relationship and ignores constant factors, Indicates time; The time domain beat frequency signal is Fourier transformed , the RF spectrum is obtained, which is expressed as follows: in, represents the frequency domain index, represents the total number of sampling points, represents the imaginary unit, The beat frequency signal in the time domain is represented by sampling points, Indicates Sampling points, each comb tooth corresponds to a different position in the two-dimensional spectral spatial encoding area, and the intensity reflects the reflectivity of the position. The spectrum is segmented by combining the comb tooth interval and the free spectrum region (FSR) of the spectrometer to obtain the intensity image of the illumination area. The RF spectrum is subjected to phase processing and unwrapping operation, which is expressed as follows: Indicates rounding down. , Indicates the phase after unwrapping; The mapping relationship is expressed as follows: in, represents the spatial coordinates, Represent the spatial coordinate positions, represents the proportionality coefficient, represents the wavelength of light, Indicates the offset.

5. The patterned wafer defect detection system based on dual-comb spatiotemporal encoding according to claim 1, characterized in that: The method of receiving and analyzing the restored three-dimensional morphology information of the surface of the wafer to be tested and extracting defect-related features includes the following steps: Performing differential processing on the restored three-dimensional morphology of the wafer to be tested in the current area and the restored three-dimensional morphology of the wafer in the adjacent area to obtain random defects on the wafer surface, and determining shape information and position information of the random defects through the random defects; By performing differential processing on the restored three-dimensional morphology of the wafer to be tested and the morphology of the standard sample, the surface system defects of the wafer to be tested are obtained; The random defects on the surface of the wafer to be tested are expressed as follows: The system defects on the surface of the wafer to be tested are expressed as follows: in, Respectively represent the position coordinates of each point on the wafer to be measured, represents the spectral intensity information at the corresponding point, is the adjacent region weight function, Represents the restoration of the three-dimensional shape, The restored 3D topography of the wafer representing the adjacent area, Indicates random defects on the wafer surface. Represents the standard sample morphology, Indicates the system defects on the surface of the wafer to be tested. represents the wavelength-dependent calibration coefficient, Indicates wavelength.

6. The patterned wafer defect detection system based on dual-optical comb spatiotemporal encoding according to claim 1, characterized in that: The method of identifying the surface defects of the wafer to obtain the corresponding defect types includes the following steps: Acquire normal wafer images and spectral data of various defect types, including surface scratches, particle contamination, bridging, and pattern loss; Mark various defect types into categories to form a labeled data set; Constructing a defect recognition pre-training model and training it based on a labeled data set, and adjusting parameters based on a loss function, thereby obtaining a defect recognition model, wherein the defect recognition pre-training model is constructed based on a convolutional neural network capable of extracting local spatial features; Based on transfer learning, the geometric features are integrated with the spectral features. Based on the mapping relationship, the spatial position of the spectral data is mapped to the actual wafer coordinates, and the defect area is marked according to the defect classification results after spectral processing. The loss function is expressed as follows: in, represents the number of defect categories, is the regularization coefficient, , Represent the true label and the predicted result respectively. Indicates defect type data, Indicates the phase offset.

7. A method for patterned wafer defect detection based on dual-optical comb spatiotemporal coding implemented by the system according to any one of claims 1 to 6, comprising the following steps: Obtaining a signal light comb and a reference light comb provided by a dual light comb light source module; The spatial coupling unit receives the signal light comb and converts it into spatial light, which then enters the beam expansion unit. The dispersion splitting unit performs multi-beam interference on the spatial light and separates it longitudinally, and then performs transverse dispersion expansion. The coding unit forms a two-dimensional spatial coded light field. The irradiation receiving unit receives the two-dimensional spatial coded light field and irradiates it on the wafer surface to form a reflected signal. The reflected signal and the reference optical comb are synchronously locked to form a time-programmed optical comb pair, and the absolute distance information is obtained by time measurement based on the time-programmed optical comb pair, and the relative time delay between the time-programmed optical comb pairs is controlled to form a time-domain beat frequency signal with different repetition frequencies; The signal acquisition and processing module acquires the time-domain beat frequency signal and extracts the spectral intensity information of the radio frequency comb, performs phase extraction and unwrapping calculation on the spectral intensity information, obtains the phase information and combines it with the spectral intensity information to obtain the restored three-dimensional morphology information of the wafer surface; The data analysis and processing module receives the restored three-dimensional morphological information of the wafer surface to be tested and identifies the defects on the wafer surface through the defect recognition model to obtain the corresponding defect types and spectral information, and determines the locations of the defects on the wafer surface based on the preset mapping relationship.

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