Wafer needle mark three-dimensional shape measurement method and device

Abstract

The invention discloses a wafer needle mark three-dimensional shape measurement method and device, and relates to the field of optical measurement. The method is used for solving the problems that three-dimensional detection of wafer defects is difficult to meet the requirement for high-precision identification of microdefects, and reconstruction precision is insufficient due to phase distortion and parasitic stray light interference. The method comprises the following steps: a parallel light beam consistent with a parasitic stray light polarization state generated by reflection of an optical element interface in a light path sequentially passes through a first telecentric microscopic system and a depolarization plate beam splitter to form first reflected light and first transmission light; reflected light of a wafer to be measured and reference reflected light form orthogonal line polarization combined light through the depolarization flat plate beam splitter, the orthogonal line polarization combined light sequentially passes through the microscope objective, the depolarization splitting prism, the tube lens and the polarization splitting prism, and light intensity graphs carrying polarization states and corresponding phase information are formed on target surfaces of the two CMOS cameras. And obtaining a reference light phase diagram, a to-be-measured wafer phase diagram, real phase information of the to-be-measured wafer and needle mark depth information of the to-be-measured wafer based on the light intensity transmission equation.

Description

A method and apparatus for measuring the three-dimensional morphology of wafer pin marks Technical Field

[0001] This invention relates to the field of optical measurement, and more specifically to a method and apparatus for measuring the three-dimensional morphology of wafer pin marks. Background Technology

[0002] Wafers are the core substrate and a crucial cornerstone of the semiconductor industry's upstream supply chain, providing fundamental support for chip design and manufacturing. Micro- and nano-scale pin marks are easily generated during wafer bump interconnection and electrical testing processes. These defects significantly impact packaging quality and yield. Three-dimensional defect reconstruction technology is needed to quantitatively characterize key parameters such as defect size and depth, scientifically assess their potential impact on system optical performance, and provide a basis for improving equipment operational stability and lifespan.

[0003] Current wafer surface defect detection technologies are mainly divided into two categories: contact and non-contact. Contact detection methods offer high longitudinal resolution but suffer from limitations such as small imaging range and slow scanning speed, and are prone to causing secondary damage to components, thus they are rarely used in practical applications. Non-contact detection mainly includes electron microscopy, acoustic methods, thermal methods, and optical methods, among which optical methods have become mainstream due to their high sensitivity, high resolution, and high efficiency. Optical detection methods based on the light intensity transmission equation also have advantages such as non-interference, no need for phase untangling, low requirements for experimental environment, and simple optical structure. Existing related patented technologies mainly include: a patterned wafer defect detection scheme combining white light interferometry and atomic force microscopy; a wafer surface three-dimensional defect detection method based on multi-angle incident light; a wafer three-dimensional morphology measurement device that can perform online rapid detection; and a wafer micro-measurement system that evaluates deformation by comparing three-dimensional data before and after processing. However, the above technologies generally suffer from low detection efficiency and complex operation, making it difficult to meet the requirements of high-precision and rapid identification of micro-defects. Meanwhile, the non-ideal characteristics of optical components in the experiment will cause the laser to undergo multiple reflections, resulting in system phase distortion. In addition, the interference of parasitic stray light will significantly reduce the quality of the reconstructed image and affect the measurement accuracy.

[0004] Existing 3D wafer defect detection technologies struggle to balance detection efficiency with the high-precision identification of micro-defects. They are also susceptible to system phase distortion and parasitic stray light interference, resulting in insufficient 3D reconstruction accuracy and failing to fully meet the detection requirements of advanced packaging processes. Summary of the Invention

[0005] This invention provides a method and apparatus for measuring the three-dimensional morphology of wafer pin marks, which solves the problem that existing three-dimensional wafer defect detection methods cannot meet the requirements for high-precision identification of micro-defects, and that the reconstruction accuracy is insufficient due to phase distortion and parasitic stray light interference.

[0006] This invention provides a method for measuring the three-dimensional morphology of wafer pin marks, comprising:

[0007] Linearly polarized laser light from a laser source is modulated by a polarization modulation component to form a parallel beam with the same polarization state as the parasitic stray light reflected from the interface of optical elements in the optical path. This beam then passes sequentially through a first telecentric microscopic system composed of a converging lens and a microscope objective, and a depolarizing flat beam splitter to form a first reflected light and a first transmitted light. The first transmitted light is reflected by the wafer under test, which contains pin marks, to form the wafer under test reflected light. The first reflected light is reflected by a reference surface and modulated by a polarization conversion element to form a reference reflected light orthogonal to the polarization state of the parasitic stray light. The wafer under test and the reference surface are conjugate about the depolarizing flat beam splitter.

[0008] The reflected light from the wafer under test and the reflected light from the reference are combined into orthogonally linearly polarized beams by a depolarizing flat beam splitter. The beams then pass sequentially through the microscope objective of the first telecentric microscopy system, the depolarizing beam splitter, the tube lens of the second telecentric microscopy system, and the polarizing beam splitter. The polarizing beam splitter separates the orthogonally linearly polarized beams into two independent polarized beams. Light intensity maps carrying polarization state and corresponding phase information are formed on the target surfaces of two CMOS cameras that are conjugate with respect to the polarizing beam splitter. The two CMOS cameras move along the optical axis to acquire the focused light intensity map and the positive defocus light intensity map and the negative defocus light intensity map, respectively.

[0009] The focused light intensity map, positive defocus light intensity map, and negative defocus light intensity map are obtained based on the light intensity transmission equation and fast Fourier transform, respectively, to obtain the reference light phase map and the phase map of the wafer under test; based on the phase map of the wafer under test and the reference light phase map, the true phase information of the wafer under test and the pin mark depth information of the wafer under test are obtained.

[0010] This invention provides a wafer needle mark three-dimensional morphology measurement device, comprising a laser emission module, a polarization modulation module, a beam splitting and conjugation module, a telecentric beam splitting imaging module, a polarization separation module, a dual-camera acquisition module, and a data processing unit arranged sequentially along the optical path;

[0011] The laser emitting module is used to convert the linearly polarized laser output from the laser source into a parallel beam;

[0012] The polarization modulation module is located between the laser emission module and the beam splitting conjugation module, and is used to modulate the parallel beam into a parallel beam with the same polarization state as the parasitic stray light generated by the reflection of the optical element interface in the optical path.

[0013] The beam splitting and conjugation module includes a depolarized flat beam splitter, a polarization conversion element, and a reference plane. The depolarized flat beam splitter is used to split a parallel beam into a first reflected beam and a first transmitted beam. The polarization conversion element is disposed in the optical path of the first reflected beam and is used to modulate the first reflected beam reflected by the reference plane into a reference reflected beam orthogonal to the polarization state of the parasitic stray light. The depolarized flat beam splitter is used to combine the reflected beam of the wafer under test and the reference reflected beam. The reference plane and the wafer under test are conjugate with respect to the depolarized flat beam splitter.

[0014] The telecentric beam-splitting imaging module includes a converging lens, a microscope objective, a depolarizing beam-splitting prism, and a tube lens. The converging lens and the microscope objective form a first telecentric microscopic system, and the microscope objective and the tube lens form a second telecentric microscopic system. The depolarizing beam-splitting prism is located between the two telecentric microscopic systems. The orthogonally linearly polarized beam combined from the depolarizing flat beam splitter passes sequentially through the microscope objective of the first telecentric microscopic system, the depolarizing beam-splitting prism, and the tube lens of the second telecentric microscopic system.

[0015] The polarization separation module is located on the light-emitting side of the second telecentric microscope system and is used to separate the orthogonally linearly polarized combined beam into S-polarized light and P-polarized light with the same splitting ratio.

[0016] The dual-camera acquisition module includes a first CMOS camera and a second CMOS camera set as conjugate with respect to a polarization beam splitter, used to receive light signals corresponding to S-polarized light and P-polarized light respectively, and to acquire focused light intensity maps and positive defocus light intensity maps and negative defocus light intensity maps with equal defocus distances.

[0017] The data processing unit is used to receive the focused light intensity map, the positive defocus light intensity map, and the negative defocus light intensity map, and to solve the reference light phase map and the phase map of the wafer under test based on the light intensity transmission equation and the fast Fourier transform, so as to obtain the true phase information of the wafer under test and the needle mark depth information of the wafer under test.

[0018] This invention provides a computer device, which includes a memory and a processor. The memory stores a computer program, and when the computer program is executed by the processor, the processor performs any of the above-described wafer pin mark three-dimensional morphology measurement methods.

[0019] This invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform any of the above-described wafer pin mark three-dimensional topography measurement methods.

[0020] This invention provides a method and apparatus for measuring the three-dimensional morphology of pin marks on wafers. This method addresses the pain points in measuring the micro-nano-scale three-dimensional morphology of pin marks on semiconductor wafers by integrating precise polarization control, dual telecentric microscopy imaging, conjugate light intensity acquisition, and phase distortion elimination. It ensures that the polarization states of the object light and parasitic stray light are consistent, and the reference light is modulated to orthogonal polarization. Combined with a polarization-preserving transmission element throughout the entire process, precise separation of the polarization domain is achieved, significantly improving the purity of the measurement signal. The conjugate setting of the wafer under test and the reference plane ensures that the reference light only carries the system's distorted phase, and the inherent error is offset by phase subtraction, guaranteeing the quantitative accuracy of the pin mark depth at the micro-nano scale. The dual telecentric microscopy system is coaxially connected and equipped with high numerical... The aperture objective lens solves the problem of uneven measurement accuracy across the entire field; the dual-camera conjugate setup, coupled with a precision displacement mechanism, enables simultaneous acquisition of equidistant positive defocus intensity images and negative defocus intensity images, with no crosstalk in polarization beam splitting, providing accurate and matched intensity data for phase calculation; combining numerical difference, intensity transmission equation, and fast Fourier transform simplifies complex calculations, eliminating the need for phase unwrapping, and exhibiting high sensitivity to minute phase shifts, balancing solution efficiency and accuracy; the optical path and algorithm are highly coordinated to meet the needs of online continuous inspection; the true phase is converted into quantifiable needle mark depth values, outputting a two-dimensional depth distribution map, completely restoring the three-dimensional morphology of the needle mark, and providing comprehensive quantitative data for defect analysis and rectification. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 is a schematic flowchart of a method for measuring the three-dimensional morphology of wafer pin marks provided in an embodiment of the present invention;

[0023] Figure 2 is a schematic diagram of the structure of the wafer needle mark three-dimensional measurement device provided in an embodiment of the present invention;

[0024] In the diagram: 1-Laser source, 2-Collimating lens, 3-Polarizer, 4-Half-wave plate, 5-Converging lens, 6-Depolarizing beam splitter, 7-Microscope objective, 8-Depolarizing flat beam splitter, 9-Half-wave plate, 10-Reference plane, 11-Wafer under test, 12-Tube lens, 13-Polarizing beam splitter, 14-First CMOS (Complementary Metal-Oxide-Semiconductor) camera, 15-Second CMOS camera. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Figure 1 is a schematic flowchart of a wafer pin mark three-dimensional morphology measurement method provided by an embodiment of the present invention; Figure 2 is a schematic structural diagram of a wafer pin mark three-dimensional measurement device provided by an embodiment of the present invention. The wafer pin mark three-dimensional morphology measurement method provided by an embodiment of the present invention will be described in detail below with reference to Figures 1 and 2. As shown in Figure 1, the method includes the following steps:

[0027] Step 101: The linearly polarized laser from the laser source is modulated by a polarization modulation component to form a parallel beam with the same polarization state as the parasitic stray light generated by reflection from the interface of the optical elements in the optical path. This beam then passes sequentially through a first telecentric microscopic system composed of a converging lens and a microscope objective, and a depolarizing flat beam splitter to form a first reflected light and a first transmitted light. The first transmitted light is reflected by the wafer under test containing pin marks to form the wafer under test reflected light. The first reflected light is reflected by a reference surface and modulated by a polarization conversion element to form a reference reflected light orthogonal to the polarization state of the parasitic stray light. The wafer under test and the reference surface are conjugate about the depolarizing flat beam splitter.

[0028] Step 102: The reflected light from the wafer under test and the reflected light from the reference are combined into orthogonally linearly polarized beams by a depolarizing flat beam splitter. The beams then pass sequentially through the microscope objective of the first telecentric microscopy system, the depolarizing beam splitter, the tube lens of the second telecentric microscopy system, and the polarizing beam splitter. A light intensity map carrying polarization state and corresponding phase information is formed on the target surface of two CMOS cameras that are conjugate with respect to the polarizing beam splitter. The two CMOS cameras move along the optical axis to collect the focused light intensity map, the positive defocus light intensity map, and the negative defocus light intensity map, respectively.

[0029] Step 103: The focused light intensity map, positive defocus light intensity map, and negative defocus light intensity map are obtained based on the light intensity transmission equation and fast Fourier transform to obtain the reference light phase map and the phase map of the wafer under test, respectively; based on the phase map of the wafer under test and the reference light phase map, the true phase information of the wafer under test and the pin mark depth information of the wafer under test are obtained.

[0030] The wafer pin mark three-dimensional morphology measurement method provided in this embodiment of the invention is based on the wafer pin mark three-dimensional morphology measurement device shown in Figure 2. Before introducing the wafer pin mark three-dimensional morphology measurement method, the wafer pin mark three-dimensional morphology measurement device is first introduced based on Figure 2.

[0031] As shown in Figure 2, the device mainly includes a laser source 1, a collimating lens 2, a polarizer 3, a half-wave plate 4, a converging lens 5, a depolarizing beam splitter 6, a microscope objective 7, a depolarizing flat beam splitter 8, a quarter-wave plate 9, a reference plane 10, a wafer under test 11, a tube lens 12, a polarizing beam splitter 13, a first CMOS camera 14, and a second CMOS camera 15.

[0032] In step 101, the linearly polarized laser from the laser source is modulated by a polarization modulation component to form a parallel beam with a polarization state consistent with that of parasitic stray light generated by reflections from the interfaces of optical elements in the optical path. The polarization modulation component here includes a polarizer and a half-wave plate. In practical applications, the laser output from the laser source, after passing through a collimating lens, vibrates only along a fixed direction. However, the device shown in Figure 2 includes multiple optical elements, such as lenses, prisms, and beam splitters. Unexpected weak reflections occur at the glass-air interfaces of these optical elements, as well as parasitic light generated by diffuse reflection from the optical path support. This type of light does not participate in effective measurement and interferes with the phase and intensity signals of the wafer under test.

[0033] In this embodiment of the invention, the linearly polarized laser first passes through a polarizer, which filters out polarization components in non-target directions to obtain pure linearly polarized light with a high extinction ratio, ensuring that the light incident on the half-wave plate is linearly polarized in a single direction. Then, it passes through an angle-adjustable half-wave plate. By rotating the fast axis angle of the half-wave plate, the polarization direction of the linearly polarized light is changed until the polarization direction of the linearly polarized laser is consistent with the polarization direction of parasitic stray light in the optical path. Through the polarizer and the half-wave plate, the interference of parasitic stray light on light intensity and phase acquisition can be eliminated from the source.

[0034] As shown in Figure 2, the device includes a converging lens and a microscope objective to form a first telecentric microscopy system. The converging lens is used to couple the polarization-modulated parallel beam into the entrance pupil of the microscope objective without aberration, ensuring the uniformity and parallelism of the beam field of view and avoiding intensity imbalance and polarization distortion caused by beam convergence / divergence. The microscope objective and the tube lens together constitute a second telecentric microscopy system, the core function of which is to eliminate parallax and full field of view magnification error, providing a basis for subsequent high-precision phase measurement.

[0035] Furthermore, when the parallel beam passes through the first telecentric microscopy system to the depolarized flat beam splitter, it is split into two beams at a fixed ratio by the depolarized flat beam splitter. One beam is the first reflected light, which propagates towards the reference plane; the other beam is the first transmitted light, which propagates towards the wafer under test.

[0036] When the first transmitted light comes into contact with the surface of the wafer under test, it undergoes specular reflection. The reflected light is the reflected light from the wafer under test. During this process, the uneven morphology of the pin marks on the surface of the wafer under test will change the propagation path of the light, causing the phase of the reflected light to shift accordingly. That is, the reflected light from the wafer under test carries the three-dimensional morphological phase information of the wafer pin marks.

[0037] The first reflected light is transmitted towards the reference plane. A quarter-wave plate is placed between the reference plane and the depolarizing flat beam splitter, meaning that the first reflected light will pass through the quarter-wave plate twice, thereby achieving a precise conversion of the polarization state. The 0° linearly polarized light, which is originally co-polarized with the parasitic stray light, is modulated into 90° linearly polarized light. In this embodiment of the invention, the modulated 90° linearly polarized light is the reference reflected light, and its polarization state is perpendicular to the 0° polarization state of the parasitic stray light and the reflected light from the wafer under test in the optical path.

[0038] As shown in Figure 2, the wafer under test and the reference plane are located on opposite sides of the depolarized flat beam splitter, with identical optical path lengths to the beam splitter and symmetrical spatial positions. This means the wafer under test and the reference plane are conjugates with respect to the depolarized flat beam splitter. The purpose is to ensure perfect optical path matching between the first reflected light and the first transmitted light, preventing any additional optical path difference when the two beams return to the beam splitter, thus avoiding phase interference errors caused by optical path differences and ensuring the clarity of the intensity map.

[0039] In step 102, the reflected light from the wafer under test and the reflected light from the reference are combined into orthogonally linearly polarized beams by a depolarizing flat beam splitter, and then pass sequentially through the microscope objective of the first telecentric microscope system, the depolarizing beam splitter, the tube lens of the second telecentric microscope system, and the polarizing beam splitter.

[0040] Specifically, the reflected light from the wafer under test maintains the same linear polarization state as the parasitic stray light; the reference reflected light passes through a quarter-wave plate twice, modulating the originally linearly polarized light, which was in the same polarization state as the parasitic stray light, into linearly polarized light orthogonal to the parasitic stray light. After the two beams are combined by the depolarized flat beam splitter, they form orthogonal linearly polarized beams with matching optical path lengths and the same frequency, satisfying the coherence condition. At the same time, the depolarized flat beam splitter adopts a depolarization design, ensuring that the polarization states of the two beams remain undistorted during the beam combining process, always maintaining an orthogonal relationship of 0° and 90°.

[0041] Furthermore, the orthogonally linearly polarized combined beam passes through the microscope objective of the first telecentric microscopy system. The microscope objective collimates the orthogonally linearly polarized combined beam into a parallel beam, ensuring beam parallelism. The microscope objective employs a polarization-free distortion-free design, so the orthogonal polarization states of 0° and 90° remain unchanged after the combined beam passes through. At the same time, the first telecentric microscopy system ensures beam uniformity across the entire field of view, avoiding intensity imbalance and decreased imaging resolution caused by beam divergence.

[0042] Furthermore, the beam-splitting surface of the depolarization beam splitter is set at 45° to the propagation direction of the orthogonal linearly polarized beam combined light. After the orthogonal linearly polarized beam combined light passes through the depolarization beam splitter, its propagation direction remains unchanged. At the same time, the depolarization beam splitter adopts a depolarization design, which ensures that the splitting ratio of the S-polarized light and the P-polarized light in the orthogonal linearly polarized beam combined light is consistent, and does not change their orthogonal polarization state, ensuring that the polarization relationship between the 0° wafer-to-be-tested reflected light and the 90° reference reflected light is distortion-free.

[0043] As shown in Figure 2, the tube lens, together with the microscope objective of the first telecentric microscopy system described above, constitutes the second telecentric microscopy system. This system precisely focuses the orthogonally polarized beam combined by the depolarizing beam splitter to form an imaging beam that meets the requirements of a CMOS camera. The focal length of the tube lens in the second telecentric microscopy system is precisely matched to the microscope objective, ensuring that the orthogonally polarized beam combined is accurately incident on the subsequent polarizing beam splitter after focusing, while also guaranteeing the uniformity and distortion-free characteristics of the telecentric optical path.

[0044] After being focused by the lens of the second telecentric microscope system, the orthogonally linearly polarized beam is incident perpendicularly on the beam-splitting surface of the polarizing beam-splitting prism. The beam-splitting surface of the polarizing beam-splitting prism is set at 45° to the beam propagation direction. The purpose of this is to separate the orthogonally polarized light in the orthogonally linearly polarized beam into S-polarized light and P-polarized light of equal proportion, and guide them to the two CMOS cameras respectively. Specifically, the reference reflected light (S-polarized light) with 90° linear polarization in the orthogonally linearly polarized beam is reflected by the polarizing beam-splitting prism and incident perpendicularly on the target surface of the first CMOS camera; the wafer reflected light (P-polarized light) with 0° linear polarization in the orthogonally linearly polarized beam is transmitted by the polarizing beam-splitting prism and incident perpendicularly on the target surface of the second CMOS camera.

[0045] As shown in Figure 2, the first CMOS camera and the second CMOS camera are symmetrically distributed with the beam-splitting surface of the polarizing beam-splitting prism as the center of symmetry. The optical path distances from the target surfaces of the two cameras to the beam-splitting surfaces are completely equal, and the incident angles are completely symmetrical. Simultaneously, both cameras are located at the rear focal plane of the second telecentric microscope system lens, adapting to the telecentric optical path. Through this setup, when the separated S-polarized and P-polarized light reach the target surfaces of the two cameras, the optical path is identical, and the light intensity attenuation is consistent, avoiding acquisition signal errors caused by optical path asymmetry. Furthermore, it allows for pixel matching and field-of-view correspondence in the intensity maps acquired by the two cameras, ensuring data comparability. Moreover, combined with the telecentric optical path, it ensures clear imaging of the entire target surface of the camera, with no resolution attenuation at the edges of the field of view, adapting to micro- and nano-scale measurements of wafer pin marks.

[0046] Furthermore, the optical signal corresponding to the S-polarized light is acquired by the first CMOS camera to obtain a first intensity image carrying the optical system distortion phase information. Specifically, the first intensity image only carries the optical system distortion phase information because the reference reflected light does not pass through the wafer under test throughout the entire process, but only through optical components such as the converging lens, depolarizing beam splitter, and depolarizing flat beam splitter in the system. Therefore, its phase information only contains the overall phase distortion of the optical system, which can be used for subsequent phase subtraction to eliminate the inherent error of the system.

[0047] Furthermore, the optical signal corresponding to the P-linearly polarized light is acquired by the second CMOS camera to obtain a second intensity image carrying the true phase information of the wafer under test. Specifically, the reflected light from the wafer under test passes through all optical elements of the system and is also reflected by the surface of the wafer under test. Its phase information is superimposed with two parts: the overall distortion phase of the optical system and the micro-nano morphology phase of the pin marks on the surface of the wafer under test. This corresponds to the system distortion phase of the first intensity image, providing a basis for extracting the true morphology by phase subtraction.

[0048] In practical applications, two CMOS cameras move along the optical axis to acquire focused light intensity images, positive defocus light intensity images, and negative defocus light intensity images, respectively. The optical axis here is the imaging optical axis of the two CMOS cameras, which is parallel to the main optical axis of the second telecentric microscopy system. The two cameras move back and forth in a straight line along their own optical axis through a precision displacement adjustment mechanism with a movement accuracy of ≤1μm to ensure the accuracy of position adjustment.

[0049] In this embodiment of the invention, the two cameras move synchronously and at the same distance to avoid mismatch in the defocus intensity map caused by differences in movement, thus providing symmetrical and accurate intensity data for the subsequent phase solution of the intensity transmission equation. When the camera target surface and the back focal plane of the tube lens are completely overlapped, the image is clearest and the image details are most complete, and the acquired intensity map is the focusing reference map. Among them, the image acquired after the camera moves a fixed distance away from the polarizing beam splitter along the optical axis is a positive defocus intensity map, and the image acquired after moving the camera a fixed distance closer to the polarizing beam splitter along the optical axis is a negative defocus intensity map.

[0050] Since the two cameras receive light signals with different polarization states and different phase information, they independently acquire focused light intensity maps, positive defocus light intensity maps, and negative defocus light intensity maps, forming two independent sets of light intensity data: the first CMOS camera moves along the optical axis to acquire the first negative defocus light intensity map, the first focused light intensity map, and the first positive defocus light intensity map, while the second CMOS camera moves along the optical axis to acquire the second negative defocus light intensity map, the second focused light intensity map, and the second positive defocus light intensity map.

[0051] In step 103, the focused light intensity map, the positive defocus light intensity map, and the negative defocus light intensity map are obtained based on the light intensity transmission equation and the fast Fourier transform, respectively, to obtain the reference light phase map and the phase map of the wafer under test;

[0052] In practical applications, phase reconstruction of the light intensity transmission equation typically requires three intensity maps: one focused intensity map and two positive and negative defocus intensity maps with equal defocus distances. In this embodiment of the invention, a set of focused intensity maps and two equidistant positive and negative defocus intensity maps are obtained by acquiring data along the optical axis using a first CMOS camera and a second CMOS camera, respectively. This eliminates the need for time-division acquisition and significantly improves detection efficiency.

[0053] To improve the phase reconstruction accuracy of the wafer under test, while removing parasitic stray light, the overall phase distortion information of the optical system is obtained by solving the light intensity transfer equation algorithm using the light intensity image acquired by the first CMOS camera. Similarly, the phase information of the wafer under test with superimposed system distortion is obtained by solving the light intensity transfer equation algorithm using the light intensity image acquired by the second CMOS camera. Subtracting the phase image of the wafer under test from the overall system phase distortion information eliminates all inherent phase distortions in the system, ultimately yielding a high-precision true phase image of the wafer under test. Simultaneously, combined with the polarization modulation technique described earlier, parasitic stray light interference is completely suppressed.

[0054] Specifically, firstly, using the acquired positive defocus intensity map and negative defocus intensity map, the first-order axial differential of the first intensity and the first-order axial differential of the second intensity are calculated using the numerical difference formula, as follows:

[0055] (1)

[0056] (2)

[0057] Furthermore, the light intensity transmission equation is solved using Fast Fourier Transform. Specifically, based on the first-order axial differential of the first light intensity, the first-order axial differential of the second light intensity, and the light intensity transmission equation, and by introducing the Teague auxiliary function and the time-domain differential property, the following reference light phase diagram and the phase diagram of the wafer under test can be obtained:

[0058] (3)

[0059] (4)

[0060] In the above method, the light intensity transmission equation is as follows:

[0061] (5)

[0062] The Teague helper function is shown below:

[0063] (6)

[0064] (7)

[0065] The time-domain differential properties are shown below:

[0066] (8)

[0067] in, The first-order axial differential represents the first light intensity. This represents the light intensity signal captured by the first CMOS camera. This represents the first negative defocus intensity diagram. This represents the first positive defocus intensity diagram. The first-order axial differential represents the second light intensity. This indicates the light intensity signal acquired by the second CMOS camera. This represents the second negative defocus intensity diagram. This represents the second positive defocus intensity diagram. This indicates the defocus distance in a single defocus direction. Indicates the direction of the optical axis of the optical system. The phase diagram representing the reference light. This represents the phase diagram of the wafer under test. This represents a two-dimensional Fast Fourier Transform. This represents the two-dimensional inverse fast Fourier transform. Represents the Hamiltonian operator. This represents the Teague auxiliary function. Indicates the light intensity captured by the second CMOS camera The reciprocal, Represents pi (π). This represents the spatial frequency corresponding to the spatial coordinate X. This represents the spatial frequency corresponding to the spatial coordinate Y. Represents the imaginary unit. This represents the light intensity signal acquired by the first CMOS camera. The reciprocal, Represents any function in the spatial domain. express The m-th order differential, Indicates the incident laser wavelength. This indicates the true phase information of the wafer under test.

[0068] In this embodiment of the invention, since the reflected light from the wafer under test and the reflected light from the reference surface pass through the same optical element, they contain the same phase distortion. Therefore, phase distortion can be completely eliminated by phase subtraction to obtain the true phase information of the wafer under test, as shown below:

[0069] (9)

[0070] Furthermore, when the laser is incident perpendicularly on the surface of the wafer under test, the optical path difference of the first transmitted light propagating through the depressions / protrusions of the needle mark is converted into a phase difference. For the reflected light path in this embodiment, the first transmitted light travels back and forth through the depth region of the needle mark; therefore, the relationship between the optical path difference and the depth can be expressed as:

[0071] (10)

[0072] Combining the fundamental relationship between phase difference and optical path difference Based on the above formulas (9) and (10), the depth information of the needle marks on the wafer to be tested is obtained:

[0073] (11)

[0074] in, This represents the phase diagram of the wafer under test. Represents the reference phase diagram. This indicates the depth of the pin marks on the wafer under test. Indicates the wavelength of light from the laser source. This indicates the true phase information of the wafer under test. This indicates the optical path difference.

[0075] Furthermore, by substituting each pixel of the true phase information of the wafer under test into formula (11), the depth information of the pin marks on the wafer under test is calculated point by point, and a two-dimensional depth distribution map can be obtained. The value of each pixel in the two-dimensional depth distribution map corresponds to the depth of the pin mark at the corresponding position on the wafer. The depth of the area without pin marks is 0, and the depth of the pin mark depression is a positive value (positive or negative value, only related to the depth direction definition), which can intuitively and completely reflect the three-dimensional morphology of the wafer pin marks.

[0076] In summary, this invention provides a method and apparatus for measuring the three-dimensional morphology of pin marks on wafers. This method addresses the pain points in measuring the micro-nano scale three-dimensional morphology of pin marks on semiconductor wafers, integrating precise polarization control, dual telecentric microscopy imaging, conjugate light intensity acquisition, and phase distortion elimination. It ensures the object light and parasitic stray light have the same polarization state, modulates the reference light into orthogonal polarization, and combines a polarization-maintaining transmission element throughout the entire process to achieve precise separation of the polarization domain, significantly improving the purity of the measurement signal. The conjugate setting of the wafer under test and the reference plane ensures that the reference light only carries the system's distorted phase, and the inherent error is offset by phase subtraction, guaranteeing the quantitative accuracy of the pin mark depth at the micro-nano scale. The dual telecentric microscopy system is coaxially connected, combined with… A high numerical aperture objective lens solves the problem of uneven measurement accuracy across the entire field; a dual-camera conjugate setup paired with a precision displacement mechanism enables simultaneous acquisition of equidistant positive defocus intensity images and negative defocus intensity images, with no crosstalk in polarization beam splitting, providing accurate and matched intensity data for phase calculation; combining numerical difference, intensity transmission equations, and fast Fourier transform simplifies complex calculations, eliminates the need for phase unwrapping, and provides high sensitivity to minute phase shifts, balancing efficiency and accuracy; the optical path and algorithm are highly coordinated to meet the needs of online continuous inspection; the true phase is converted into quantifiable needle mark depth values, outputting a two-dimensional depth distribution map, completely restoring the three-dimensional morphology of the needle mark, and providing comprehensive quantitative data for defect analysis and rectification.

[0077] Based on the same inventive concept, this invention provides a wafer pin mark three-dimensional morphology measurement device. Since the principle of this device in solving the technical problem is similar to that of a wafer pin mark three-dimensional morphology measurement method, the implementation of this device can refer to the implementation of the method, and the repeated parts will not be described again.

[0078] The device includes a laser emission module, a polarization modulation module, a beam splitting and conjugation module, a telecentric beam splitting imaging module, a polarization separation module, a dual-camera acquisition module, and a data processing unit arranged sequentially along the optical path.

[0079] The laser emitting module is used to convert the linearly polarized laser output from the laser source into a parallel beam;

[0080] The polarization modulation module is located between the laser emission module and the beam splitting conjugation module, and is used to modulate the parallel beam into a parallel beam with the same polarization state as the parasitic stray light generated by the reflection of the optical element interface in the optical path.

[0081] The beam splitting and conjugation module includes a depolarized flat beam splitter, a polarization conversion element, and a reference plane. The depolarized flat beam splitter is used to split a parallel beam into a first reflected beam and a first transmitted beam. The polarization conversion element is disposed in the optical path of the first reflected beam and is used to modulate the first reflected beam reflected by the reference plane into a reference reflected beam orthogonal to the polarization state of the parasitic stray light. The depolarized flat beam splitter is used to combine the reflected beam of the wafer under test and the reference reflected beam. The reference plane and the wafer under test are conjugate with respect to the depolarized flat beam splitter.

[0082] The telecentric beam-splitting imaging module includes a converging lens, a microscope objective, a depolarizing beam-splitting prism, and a tube lens. The converging lens and the microscope objective form a first telecentric microscopic system, and the microscope objective and the tube lens form a second telecentric microscopic system. The depolarizing beam-splitting prism is located between the two telecentric microscopic systems. The orthogonally linearly polarized beam combined from the depolarizing flat beam splitter passes sequentially through the microscope objective of the first telecentric microscopic system, the depolarizing beam-splitting prism, and the tube lens of the second telecentric microscopic system.

[0083] The polarization separation module is located on the light-emitting side of the second telecentric microscope system and is used to separate the orthogonally linearly polarized combined beam into S-polarized light and P-polarized light with the same splitting ratio.

[0084] The dual-camera acquisition module includes a first CMOS camera and a second CMOS camera set as conjugate with respect to a polarization beam splitter, used to receive light signals corresponding to S-polarized light and P-polarized light respectively, and to acquire focused light intensity maps and positive defocus light intensity maps and negative defocus light intensity maps with equal defocus distances.

[0085] The data processing unit is used to receive the focused light intensity map, the positive defocus light intensity map, and the negative defocus light intensity map, and to solve the reference light phase map and the phase map of the wafer under test based on the light intensity transmission equation and the fast Fourier transform, so as to obtain the true phase information of the wafer under test and the needle mark depth information of the wafer under test.

[0086] As shown in Figure 2, the device includes a laser emission module comprising a laser source 1 and a collimating lens 2; a polarization modulation module comprising a polarizer 3 and a half-wave plate 4; a beam splitting and conjugation module comprising a depolarizing flat beam splitter 8, a quarter-wave plate 9, and a reference plane 10; a telecentric beam splitting imaging module comprising a first telecentric microscopy system and a second telecentric microscopy system, the first telecentric microscopy system comprising a depolarizing beam splitter prism 6 and a microscope objective 7, and the second telecentric microscopy system comprising a microscope objective 7 and a tube lens 12; a polarization separation module comprising a polarizing beam splitter prism 13; a dual-camera acquisition module comprising a first CMOS camera 14 and a second CMOS camera 15; and a data processing unit being a computer.

[0087] It should be understood that the units included in the above-described wafer pin mark three-dimensional topography measurement device are only a logical division based on the functions implemented by the device. In practical applications, the above units can be superimposed or separated. Furthermore, the functions implemented by the wafer pin mark three-dimensional topography measurement device provided in this embodiment correspond one-to-one with the wafer pin mark three-dimensional topography measurement method provided in the above embodiment. The more detailed processing flow implemented by this device has been described in detail in the above-described method embodiment one, and will not be described in detail here.

[0088] Another embodiment of the present invention provides a computer device, the computer device including: a processor and a scene database; the scene database is used to store computer program code, the computer program code including computer instructions; when the processor executes the computer instructions, the electronic device executes each step of the wafer pin mark three-dimensional topography measurement method shown in the above method embodiment.

[0089] Another embodiment of the present invention provides a computer-readable storage medium storing computer instructions that, when executed on a computer device, cause the computer device to perform the various steps of the wafer pin mark three-dimensional topography measurement method shown in the above method embodiment.

[0090] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for measuring the three-dimensional morphology of needle marks on a wafer, characterized in that, include: Linearly polarized laser light from a laser source is modulated by a polarization modulation component to form a parallel beam whose polarization state is consistent with that of parasitic stray light generated by reflection from the interface of optical elements in the optical path. The beam passes sequentially through a first telecentric microscopic system composed of a converging lens and a microscope objective, and a depolarizing flat beam splitter to form a first reflected light and a first transmitted light. The first transmitted light is reflected by the wafer under test containing needle marks to form the wafer under test reflected light. The first reflected light is reflected by the reference plane and modulated by the polarization conversion element to form a reference reflected light orthogonal to the polarization state of the parasitic stray light; the wafer under test and the reference plane are conjugate about the depolarizing flat beam splitter; the reflected light from the wafer under test and the reference reflected light are combined into orthogonal linearly polarized beams by the depolarizing flat beam splitter, and then pass sequentially through the microscope objective of the first telecentric microscope system, the depolarizing beam splitter, the tube lens of the second telecentric microscope system, and the polarizing beam splitter; the polarizing beam splitter separates the orthogonal linearly polarized beam into two independent polarized beams, which are then separated into two independent polarized beams. A light intensity map carrying polarization state and corresponding phase information is formed on the target surface of a CMOS camera with a polarization beam splitter conjugate. Two CMOS cameras move along the optical axis to acquire a focused light intensity map, a positive defocus light intensity map, and a negative defocus light intensity map, respectively. The focused light intensity map, the positive defocus light intensity map, and the negative defocus light intensity map are used to obtain a reference light phase map and a phase map of the wafer under test, respectively, based on the light intensity transmission equation and the fast Fourier transform. According to the phase map of the wafer under test and the reference light phase map, the true phase information of the wafer under test and the pin mark depth information of the wafer under test are obtained.

2. The method as described in claim 1, characterized in that, The second telecentric microscopy system includes a microscope objective and a tube lens; the field of view uniformity of the first telecentric microscopy system and the second telecentric microscopy system is consistent, and the microscope objective is a high numerical aperture microscope objective.

3. The method as described in claim 1, characterized in that, The polarization modulation assembly includes a polarizer and a half-wave plate; the polarization conversion element is a quarter-wave plate; the linearly polarized laser from the laser source is modulated by the polarization modulation assembly to form a parallel beam with the same polarization state as the parasitic stray light generated by reflection from the interface of the optical element in the optical path, specifically including: the linearly polarized laser from the laser source is modulated by the polarizer and the half-wave plate to form 0° linearly polarized light with the same polarization as the parasitic stray light generated by reflection from the interface of the optical element in the optical path; the first reflected light is reflected by the reference surface and modulated by the polarization conversion element to form a reference reflected light orthogonal to the polarization state of the parasitic stray light, specifically including: the first reflected light is modulated by the quarter-wave plate, reflected by the reference surface and modulated by the quarter-wave plate to form 90° linearly polarized light orthogonal to the polarization state of the parasitic stray light.

4. The method as described in claim 1, characterized in that, The process of forming a light intensity map carrying polarization state and phase information on the target surface of two CMOS cameras with conjugate polarization beam splitters specifically includes: the beam splitting surface of the polarization beam splitter is set at 45° to the propagation direction of the orthogonally linearly polarized combined beam; the polarization beam splitter splits the orthogonally linearly polarized combined beam passing through the tube lens of the second telecentric microscope system into S-polarized light and P-polarized light with the same splitting ratio; the S-polarized light is incident on the first CMOS camera and acquired to obtain a first intensity image carrying optical system distortion phase information; the P-polarized light is incident on the second CMOS camera and acquired to obtain a second intensity image carrying the true phase information of the wafer under test.

5. The method as described in claim 1, characterized in that, The focused light intensity map, positive defocus light intensity map, and negative defocus light intensity map are obtained based on the light intensity transmission equation and Fast Fourier Transform to obtain a reference light phase map and a phase map of the wafer under test, respectively. Specifically, this includes: a first CMOS camera moving along the optical axis to acquire a first negative defocus light intensity map, a first focused light intensity map, and a first positive defocus light intensity map; a second CMOS camera moving along the optical axis to acquire a second negative defocus light intensity map, a second focused light intensity map, and a second positive defocus light intensity map; the first axial derivative of the first light intensity is obtained based on numerical difference estimation; the reference light phase map is obtained based on the first axial derivative of the first light intensity, the light intensity transmission equation, and Fast Fourier Transform; the first axial derivative of the second light intensity is obtained based on numerical difference estimation; the phase map of the wafer under test is obtained based on the first axial derivative of the second light intensity, the light intensity transmission equation, and Fast Fourier Transform.

6. The method as described in claim 5, characterized in that, The first-order axial derivatives of the first light intensity and the second light intensity are shown below: The reference light phase map and the phase map of the wafer under test are shown below: in, The first-order axial differential represents the first light intensity. This represents the light intensity signal captured by the first CMOS camera. This represents the first negative defocus intensity diagram. This represents the first positive defocus intensity diagram. The first-order axial differential represents the second light intensity. This indicates the light intensity signal acquired by the second CMOS camera. This represents the second negative defocus intensity diagram. This represents the second positive defocus intensity diagram. This indicates the defocus distance in a single defocus direction. Indicates the direction of the optical axis of the optical system. The phase diagram representing the reference light. This represents the phase diagram of the wafer under test. This represents a two-dimensional Fast Fourier Transform. This represents the two-dimensional inverse fast Fourier transform. Represents the Hamiltonian operator. This represents the Teague auxiliary function. Indicates the light intensity captured by the second CMOS camera The reciprocal, Represents pi (π). This represents the spatial frequency corresponding to the spatial coordinate X. This represents the spatial frequency corresponding to the spatial coordinate Y.

7. A device for measuring the three-dimensional morphology of wafer pin marks, characterized in that, The system includes a laser emission module, a polarization modulation module, a beam splitting and conjugation module, a telecentric beam splitting and imaging module, a polarization separation module, a dual-camera acquisition module, and a data processing unit, arranged sequentially along the optical path. The laser emission module converts the linearly polarized laser light output from the laser source into a parallel beam. The polarization modulation module, located between the laser emission module and the beam splitting and conjugation module, modulates the parallel beam into a parallel beam with a polarization state consistent with that of parasitic stray light generated by reflections from the interfaces of optical elements in the optical path. The beam splitting and conjugation module includes a depolarizing flat beam splitter and a polarization converter. The system includes components and a reference plane. The depolarized flat beam splitter is used to split a parallel beam into a first reflected beam and a first transmitted beam. The polarization conversion element is disposed in the optical path of the first reflected beam and is used to modulate the first reflected beam reflected from the reference plane into a reference reflected beam orthogonal to the polarization state of the parasitic stray light. The depolarized flat beam splitter is used to combine the reflected beam from the wafer under test and the reference reflected beam. The reference plane and the wafer under test are conjugate with respect to the depolarized flat beam splitter. The telecentric beam-splitting imaging module includes a converging lens, a microscope objective, a depolarized beam-splitting prism, and a tube lens. A condenser lens and a microscope objective form a first telecentric microscopy system; the microscope objective and a tube lens form a second telecentric microscopy system; a depolarizing beam-splitter is positioned between the two telecentric microscopy systems; orthogonally linearly polarized combined beams from the depolarizing flat beam splitter pass sequentially through the microscope objective of the first telecentric microscopy system, the depolarizing beam-splitter, and the tube lens of the second telecentric microscopy system; a polarization separation module, located on the light-emitting side of the second telecentric microscopy system, separates the orthogonally linearly polarized combined beams into S-polarized light and P-polarized light with the same splitting ratio; the dual... The camera acquisition module includes a first CMOS camera and a second CMOS camera conjugate with respect to a polarization beam splitter, used to receive optical signals corresponding to S-polarized light and P-polarized light respectively, and to acquire a focused light intensity map and positive and negative defocus light intensity maps with equal defocus distances; the data processing unit is used to receive the focused light intensity map and the positive and negative defocus light intensity maps, and to solve the reference light phase map and the phase map of the wafer under test based on the light intensity transmission equation and fast Fourier transform, so as to obtain the true phase information and the pin mark depth information of the wafer under test.

8. The apparatus as claimed in claim 7, characterized in that, Both the depolarized flat beam splitter and the depolarized beam splitter prism adopt a depolarization design. The depolarized flat beam splitter is used to split a parallel beam into a first reflected light and a first transmitted light with the same splitting ratio. It is used to integrate the reflected light from the wafer under test and the reference reflected light into an orthogonally linearly polarized beam. The depolarized beam splitter prism is used to make the orthogonally linearly polarized beam propagate in a straight line along the original optical axis.

9. A computer device, characterized in that, The computer device includes a memory and a processor. The memory stores a computer program, which, when executed by the processor, causes the processor to perform the wafer pin mark three-dimensional topography measurement method as described in any one of claims 1-6.

10. A computer-readable storage medium, characterized in that, The device contains a computer program that, when executed by a processor, causes the processor to perform the wafer pin mark three-dimensional topography measurement method as described in any one of claims 1-6.

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