Nondestructive multi-layer cross-section-like focused ion beam imaging

Abstract

A system includes a processor in electronic communication with a structured light assembly and an imaging assembly. The structured light assembly is configured to project a structured light pattern onto a workpiece, wherein the workpiece is a multi-layer structure. The imaging assembly is configured to capture a plurality of structured light images of the workpiece, wherein each of the plurality of structured light images is captured if the imaging assembly is focused at a different height relative to the workpiece. The processor is configured to generate a cross-sectional image of the workpiece based on the plurality of structured light images received from the imaging assembly.

Description

[0001] Cross-reference of related applications

[0002] This application claims priority to provisional patent application No. 63 / 546,250, filed on October 30, 2023, the disclosure of which is hereby incorporated by reference. Technical Field

[0003] This disclosure relates to inspection systems, and more specifically to the inspection of transparent semiconductor components in electronic manufacturing. Background Technology

[0004] The evolution of the electronics manufacturing industry places increasingly higher demands on production management, and specifically on measurement and inspection systems. Critical dimensions continue to shrink, and the industry needs to reduce the time required to achieve high-volume, high-value production. Minimizing the total time from detecting a production problem to resolving it maximizes the return on investment for electronics manufacturers.

[0005] Inspection processes are used at every step of electronics manufacturing to detect defects in wafers, electronic devices, or circuits, enabling higher throughput and thus higher profits. Inspection has always been a vital part of manufacturing electronic devices such as integrated circuits (ICs), flat panel displays (e.g., organic light-emitting diode-on-silicon (OLEDoS) display panels), and printed circuit boards (PCBs), including assembled PCBs. However, as feature sizes shrink, inspection becomes even more critical for the successful manufacture of acceptable electronic devices because even small defects can cause device and assembly failures. For example, with smaller feature sizes, the detection of smaller defects has become necessary because even relatively small defects can cause undesirable aberrations in the device.

[0006] Even for transparent multilayer structures, inspection processes may struggle to detect internal defects (e.g., between layers). Some existing methods rely on a focused ion beam (FIB) that strikes the workpiece while capturing an image. However, FIB is destructive to the workpiece because it drills deeper into the workpiece for imaging.

[0007] Therefore, a non-destructive method for detecting internal defects is needed. Summary of the Invention

[0008] Embodiments of this disclosure provide a method comprising projecting a structured light pattern onto a workpiece, wherein the workpiece is a multi-layered structure. The method may further comprise capturing a plurality of structured light images of the workpiece using an imaging assembly, each of the plurality of structured light images being captured while the imaging assembly is focused at a different depth of focus relative to the workpiece. The method may further comprise generating a cross-sectional image of the workpiece based on the plurality of structured light images.

[0009] According to embodiments of this disclosure, the plurality of structured light images may include at least 100 images captured at different depths of focus.

[0010] According to embodiments of this disclosure, the workpiece may be placed on a stage, and capturing the plurality of structured light images of the workpiece using the imaging assembly may include: moving the stage to adjust the distance of the imaging assembly relative to the workpiece; and capturing the structured light image of the workpiece at each distance using the imaging assembly to obtain a plurality of structured light images at different depths of focus.

[0011] According to embodiments of this disclosure, generating the cross-sectional image of the workpiece based on the plurality of structured light images may include: defining a cross section passing through the workpiece, wherein the cross section intersects with each of the plurality of structured light images; determining a focus fraction for each pixel of the plurality of structured light images intersecting the cross section, wherein the focus fraction corresponds to the reflection of the structured light pattern reflected by the workpiece at a corresponding depth of focus; and combining the focus fraction of each pixel in the cross section to generate the cross-sectional image of the workpiece.

[0012] According to embodiments of this disclosure, combining the focus score of each pixel in the cross-section to generate the cross-sectional image of the workpiece may include: comparing the focus score of each pixel in the cross-section with a preset threshold, wherein the preset threshold is greater than or equal to zero; filling each pixel of the cross-section having a focus score greater than the preset threshold with a first color; and filling each pixel of the cross-section having a focus score less than the preset threshold with a second color different from the first color. The cross-sectional image may be defined by pixels having the first color and pixels having the second color.

[0013] According to embodiments of this disclosure, combining the focus fraction of each pixel in the cross section to generate the cross-sectional image of the workpiece may further include: classifying each pixel of the cross section having a focus fraction greater than the preset threshold as being at the interface between layers of the multilayer structure; and assigning the first color based on the classification of the interface between the layers.

[0014] According to embodiments of this disclosure, the workpiece may be a flat panel display.

[0015] Another embodiment of this disclosure provides a non-transitory computer-readable storage medium including instructions stored thereon, which, when executed by a processor, cause the processor to: control a structured light assembly to project a structured light pattern onto a workpiece, wherein the workpiece is a multi-layered structure; control an imaging assembly to capture a plurality of structured light images of the workpiece, wherein each of the plurality of structured light images is captured with the imaging assembly focused at a different height relative to the workpiece; and generate a cross-sectional image of the workpiece based on the plurality of structured light images received from the imaging assembly.

[0016] According to an embodiment of this disclosure, the workpiece can be placed on a stage, and the processor can further cause the processor to: send instructions to move the stage to adjust the distance of the imaging assembly relative to the workpiece; and use the imaging assembly at each distance to capture a structured light image of the workpiece to obtain multiple structured light images at different depths of focus.

[0017] According to embodiments of this disclosure, the processor may further cause to: define a cross section passing through the workpiece, wherein the cross section intersects each of the plurality of structured light images; determine a focus fraction for each pixel of the plurality of structured light images intersecting the cross section, wherein the focus fraction corresponds to the reflection of the structured light pattern reflected by the workpiece at a corresponding depth of focus; and combine the focus fraction of each pixel in the cross section to generate the cross-sectional image of the workpiece.

[0018] According to embodiments of this disclosure, the processor may further cause to: compare the focus score of each pixel in the cross-section with a preset threshold, wherein the preset threshold is greater than or equal to zero; fill each pixel of the cross-section having a focus score greater than the preset threshold with a first color; and fill each pixel of the cross-section having a focus score less than the preset threshold with a second color different from the first color. The cross-sectional image is defined by pixels having the first color and pixels having the second color.

[0019] According to embodiments of this disclosure, the processor may further: classify each pixel of the cross section having a focus score greater than the preset threshold as being at the interface between layers of the multilayer structure; and assign the first color based on the classification of the interface between the layers.

[0020] Another embodiment of this disclosure provides a system including a structured light assembly, an imaging assembly, and a processor in electronic communication with the structured light assembly and the imaging assembly. The structured light assembly can be configured to project a structured light pattern onto a workpiece, wherein the workpiece is a multi-layered structure. The imaging assembly can be configured to capture a plurality of structured light images of the workpiece, each of the plurality of structured light images being captured with the imaging assembly focused at a different height relative to the workpiece. The processor can be configured to generate a cross-sectional image of the workpiece based on the plurality of structured light images received from the imaging assembly.

[0021] According to embodiments of the present disclosure, the workpiece may be placed on a stage, and the processor may be further configured to: send instructions to move the stage to adjust the distance of the imaging assembly relative to the workpiece; and capture structured light images of the workpiece at each distance using the imaging assembly to obtain the plurality of structured light images at different depths of focus.

[0022] According to embodiments of this disclosure, the processor may be further configured to: define a cross section passing through the workpiece, wherein the cross section intersects each of the plurality of structured light images; determine a focus fraction for each pixel of the plurality of structured light images intersecting the cross section, wherein the focus fraction corresponds to the reflection of the structured light pattern reflected by the workpiece at a corresponding depth of focus; and combine the focus fraction of each pixel in the cross section to generate the cross-sectional image of the workpiece.

[0023] According to embodiments of this disclosure, the processor may be further configured to: compare the focus score of each pixel in the cross-section with a preset threshold, wherein the preset threshold is greater than or equal to zero; fill each pixel of the cross-section having a focus score greater than the preset threshold with a first color; and fill each pixel of the cross-section having a focus score less than the preset threshold with a second color different from the first color. The cross-sectional image may be defined by pixels having the first color and pixels having the second color.

[0024] According to embodiments of this disclosure, the processor may be further configured to: classify each pixel of the cross section having a focus score greater than the preset threshold as being at the interface between layers of the multilayer structure; and assign the first color based on the classification of the interface between the layers. Attached Figure Description

[0025] For a more complete understanding of the nature and purpose of this disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, wherein:

[0026] Figure 1 A diagram of a system according to an embodiment of the present disclosure;

[0027] Figure 2 This is a perspective view of an exemplary workpiece disclosed herein;

[0028] Figure 3A yes Figure 2 A cross-sectional view of an exemplary workpiece;

[0029] Figure 3B The corresponding embodiment produced by the present disclosure Figure 3A Exemplary cross-sectional images of the cross-section;

[0030] Figure 4 This is a flowchart of a method according to an embodiment of the present disclosure;

[0031] Figure 5 This is a flowchart of a method according to another embodiment of the present disclosure;

[0032] Figure 6 This is a flowchart of a method according to another embodiment of the present disclosure; and

[0033] Figure 7 This is a flowchart of a method according to another embodiment of the present disclosure. Detailed Implementation

[0034] While the claimed subject matter will be described with reference to specific embodiments, other embodiments (including those not providing all the benefits and features set forth herein) are also within the scope of this disclosure. Various structural, logical, procedural, and electronic changes may be made without departing from the scope of this disclosure. Therefore, the scope of this disclosure is defined only by reference to the appended claims.

[0035] Embodiments of this disclosure provide a system 100. (See also...) Figure 1 The system 100 may include a structured light assembly 110, an imaging assembly 120, and a processor 130 that communicates electronically with the structured light assembly 110 and the imaging assembly 120.

[0036] The structured light assembly 110 can be configured to project a structured light pattern 111 onto a workpiece 101. The workpiece 101 can have a multi-layered structure. For example, such as... Figure 2As shown, workpiece 101 may include multiple layers 102, with an interface 103 between each layer. Each of the layers 102 may be transparent or translucent, allowing the structured light pattern 111 to be transmitted through workpiece 101. In some embodiments, workpiece 101 may be a flat panel display. For example, workpiece 101 may include an organic light-emitting diode (OLED) or an OLED panel on silicon. Structured light assembly 110 may include a light source and a pattern generator disposed in the optical path of the light source. The light source may be a lamp, fiber-coupled light, LED light, or a laser. The structured light pattern 111 is generated by projecting light from the light source through the pattern generator. The pattern generator may be mechanical or electronic. For example, a mechanical pattern generator may be a patterned article comprising a piece of patterned photographic film or patterned glass. An electronic pattern generator may be a liquid crystal pattern generator (LCPG) capable of generating different patterns. The patterned article or LCPG may have high contrast, regular or random patterns, translucent features, and a minimum feature size corresponding to the sampling resolution of imaging assembly 120. In some embodiments, the imaging assembly 120 may include an array of light sources that form a structured light pattern 111 without using a separate pattern generator. In any arrangement, the structured light pattern 111 generated by the structured light assembly 110 may be a grid or other pattern and is not limited herein. The structured light assembly 110 may further include one or more optical elements, such as lenses, beam splitters, mirrors, filters, microscope objectives, etc., disposed in the optical path of the light source.

[0037] Imaging assembly 120 may be configured to capture multiple structured light images 121 of workpiece 101. Imaging assembly 120 may include a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera. Each of the multiple structured light images 121 may be captured with imaging assembly 120 focused at different heights relative to workpiece 101. The difference between each depth of focus 122 may depend on the thickness of workpiece 101 and the resolution of imaging assembly 120. In some embodiments, for workpiece 101 having a thickness of tens of micrometers, the difference between each depth of focus 122 may be tens of nanometers. In other words, the difference between each depth of focus 122 may be one-hundredth, one-thousandth, or any other dimensional deviation of the thickness of workpiece 101. It should be understood that reducing the difference between each depth of focus 122 can capture more data, but can multiply the number of images required to cover the thickness of workpiece 101. In some embodiments, the multiple structured light images 121 may include at least 100 images. Depending on the maximum speed of the camera sensor in the imaging assembly 120, the imaging assembly 120 can be configured to capture images at 800 frames per second or more. The imaging assembly 120 may further include one or more optical elements, such as lenses, beam splitters, mirrors, filters, microscope objectives, etc., disposed in the optical path of the camera. The optical elements can be configured to adjust the focal length, magnification, working distance, and / or numerical aperture of the imaging assembly 120. For example, the depth of focus 122 can be set based on the arrangement of the optical elements in the imaging assembly 120. Depending on the magnification of the imaging assembly 120, the camera's field of view may cover the entire workpiece 101 or only a portion of the workpiece 101.

[0038] Processor 130 may be configured to generate a cross-sectional image 131 of workpiece 101 based on a plurality of structured light images 121 received from imaging assembly 120. For example, the cross-sectional image 131 may be generated using data corresponding to the reflection of a structured light pattern 111 on workpiece 101 at a varying depth of focus 122 from the plurality of structured light images 121. Processor 130 may include a microprocessor, microcontroller, or other device.

[0039] Processor 130 may be coupled to components of system 100 in any suitable manner (e.g., via one or more transmission media, which may include wired and / or wireless transmission media) such that processor 130 can receive output. Processor 130 may be configured to perform certain functions using the output. Inspection tools may receive instructions or other information from processor 130. Processor 130 may, as appropriate, communicate electronically with another inspection tool, measuring tool, repair tool, or review tool (not specified) to receive additional information or send instructions.

[0040] Processor 130 may be part of various systems, including personal computer systems, graphics computers, mainframe computer systems, workstations, network appliances, internet appliances, or other devices. The subsystem or system may also include any suitable processor known in the art, such as a parallel processor. Additionally, the subsystem or system may include a platform with high-speed processing and software, as a standalone or networked tool.

[0041] Processor 130 may be located in or otherwise become part of system 100 or another device. In examples, processor 130 may be part of a separate control unit or in a centralized quality control unit. Multiple processors 130 may be used to define multiple subsystems of system 100.

[0042] In practice, processor 130 can be implemented through any combination of hardware, software, and firmware. Furthermore, its functions as described herein can be performed by a single unit or divided among different components, each of which can be implemented through any combination of hardware, software, and firmware. Program code or instructions that enable processor 130 to perform various methods and functions can be stored in a readable storage medium (e.g., memory).

[0043] If system 100 comprises more than one subsystem, then different processors 130 can be coupled to each other to enable the transmission of images, data, information, instructions, etc., between the subsystems. For example, a subsystem can be coupled to an additional subsystem via any suitable transmission medium (which may include any suitable wired and / or wireless transmission medium known in the art). Two or more such subsystems can also be effectively coupled via a shared computer-readable storage medium (not shown).

[0044] Processor 130 may be configured to perform certain functions using the output of system 100 or other outputs. For example, processor 130 may be configured to send outputs to an electronic data storage unit or another storage medium. Processor 130 may be further configured as described herein.

[0045] Processor 130 may be configured according to any of the embodiments described herein. Processor 130 may also be configured to perform other functions or additional steps using the output of system 100 or using images or data from other sources.

[0046] Processor 130 can be communicatively coupled to any of the various components or subsystems of system 100 in any manner known in the art. Furthermore, processor 130 can be configured to receive and / or acquire data or information (e.g., inspection results from an inspection system (e.g., a verification tool), a remote database containing design data, and the like) from other systems via a transmission medium (which may include wired and / or wireless portions). In this manner, the transmission medium can serve as a data link between processor 130 and other subsystems of system 100 or systems external to system 100. The various steps, functions, and / or operations of system 100, as well as the methods disclosed herein, are implemented by one or more of the following: electronic circuits, logic gates, multiplexers, programmable logic devices, ASICs, analog or digital controls / switches, microcontrollers, or computing systems. Program instructions implementing the methods (e.g., the methods described herein) can be transmitted via a carrier medium or stored on a carrier medium. The carrier medium may include storage media such as read-only memory, random access memory, magnetic disk or optical disk, non-volatile memory, solid-state memory, magnetic tape, and the like. The carrier medium may include transmission media, such as wires, cables, or wireless transmission links. For example, the various steps described throughout this disclosure may be implemented by a single processor 130 (or computer subsystem), or alternatively by multiple processors 130 (or multiple computer subsystems). Furthermore, different subsystems of system 100 may comprise one or more computing or logic systems. Therefore, the foregoing description should not be construed as a limitation of this disclosure but is merely illustrative.

[0047] In some embodiments, system 100 may further include stage 105. Workpiece 101 may be mounted on stage 105. Stage 105 may be movable relative to imaging assembly 120. For example, stage 105 may include one or more actuators or motors configured to move stage 105 in a plane (e.g., in the X and Y directions) and in a depth direction (e.g., the Z direction). Processor 130 may be further configured to send instructions to move stage 105 to adjust the distance of imaging assembly 120 relative to workpiece 101, thereby changing the position of depth of focus 122 within workpiece 101. For example, stage 105 may move incrementally based on the difference between depths of focus 122 (in the Z direction) set by processor 130. Alternatively, imaging assembly 120 may be movable relative to stage 105, and imaging assembly 120 (or its optics) may move incrementally based on the difference between depths of focus 122 set by processor 130. Processor 130 may be further configured to send instructions to move stage 105 or imaging assembly 120 in the X or Y direction to scan workpiece 101 relative to imaging assembly 120. Processor 130 may be further configured to send instructions to imaging assembly 120 to capture structured light images of workpiece 101 at each distance to obtain a plurality of structured light images 121 corresponding to each depth of focus 122. In some embodiments where the field of view of the camera covers only a portion of workpiece 101, processor 130 may be further configured to send instructions to imaging assembly 120 to capture structured light images of workpiece 101 after stage 105 has moved to a different XY position at each distance in the Z direction. Each of the plurality of structured light images 121 may be transmitted to processor 130 separately after being captured, or imaging assembly 120 may transmit the plurality of structured light images 121 to processor 130 after imaging at each distance within the depth of focus 122 of workpiece 101.

[0048] In some embodiments, the processor 130 may be further configured to define a cross section 104 passing through the workpiece 101. The cross section 104 may intersect each of the plurality of structured light images 121. Figure 2As shown, section 104 may be perpendicular to workpiece 101 in both the height and width directions. However, section 104 may be angled relative to workpiece 101 and is not limited herein. The position and orientation of section 104 may be preset by processor 130 or selected by the user. For example, section 104 may be placed at a preset area of ​​interest on workpiece 101 or based on feedback from multiple structured light images 121 (e.g., where defects exist in workpiece 101). Processor 130 may be further configured to determine the focus fraction of each pixel of the multiple structured light images 121 intersected by section 104. In other words, each of the multiple structured light images 121 may be divided into a pixel array, and processor 130 may select pixels intersected by section 104 for processing. For processing efficiency, remaining pixels may be ignored, or processor 130 may also determine the focus fraction of each remaining pixel to generate a multi-layer 3D map of workpiece 101 based on the multiple structured light images 121. The focus fraction can correspond to the reflection of the structured light pattern 111 reflected by the workpiece 101 at the corresponding depth of focus 122. The processor 130 can be further configured to combine the focus fraction of each pixel in the cross section 104 to generate a cross-sectional image 131 of the workpiece 101. For example, using each pixel of a plurality of structured light images 121 and the focus fraction determined for each pixel, the processor 130 can be configured to combine each pixel into a pixel array to form the cross-sectional image 131.

[0049] In some embodiments, processor 130 may be further configured to compare the focus score of each pixel in section 104 with a preset threshold. In some embodiments, the preset threshold may be greater than zero or equal to zero. When the depth of focus 122 is at the interface 103 between layers 102 of a multilayer structure, the structured light pattern 111 is reflected by the workpiece 101 at the interface 103, and the focus score may be greater than the preset threshold. For example, the structured light pattern 111 may be reflected from the interface 103 between layers 102, and the intensity of the reflected light is detected by the imaging assembly 120. Processor 130 may be further configured to classify the type of layer 102 at interface 103 based on the focus score value being greater than the preset threshold. For example, interface 103 may reflect light differently based on the type / material of layer 102 at interface 103, thereby generating different focus scores that can be used for classification. When the depth of focus 122 is within layers 102 of a multilayer structure, the structured light pattern 111 may be reflected by or transmissive through the workpiece 101, and the focus score may be less than the preset threshold. For example, the structured light pattern 111 may be transmissive through layer 102 without reflection, thereby not being detected by the imaging assembly 120 and corresponding to a focus fraction of zero. Alternatively, the structured light pattern 111 may be partially reflected from within layer 102, but the focus fraction may be less than a preset threshold. It should be understood that, for example, the preset threshold used by the processor 130 may be calibrated for the material of the workpiece 101 under inspection based on the intensity range of the reflection detected by the imaging assembly 120.

[0050] In some embodiments, processor 130 may be further configured to fill each pixel of cross section 104 having a focus score greater than a preset threshold with a first color 132. Processor 130 may be further configured to fill each pixel of cross section 104 having a focus score less than a preset threshold with a second color 133 different from the first color 132. Cross-sectional image 131 may be defined by pixels having the first color 132 and pixels having the second color 133. Therefore, cross-sectional image 131 may illustrate the internal structure of workpiece 101 based on reflections at the interface 103 between layers 102 and the presence of any anomalies or defects within workpiece 101. In embodiments where processor 130 further classifies the interface 103 between layers 102 based on a focus score higher than a preset threshold, different classifications may correspond to different colors, and processor 130 may assign the first color 132 based on the classification of the interface 103 between layers 102. Different classifications may use different colors that can be distinguished from the first color 132 and the second color 133. Therefore, the cross-sectional image 131 can use different colors to further illustrate the different materials / classifications of the various layers 102 of the workpiece 101.

[0051] Figure 3AThis illustration shows a cross-sectional view of a workpiece 101 taken along section 104. The workpiece 101 comprises three layers 102 with interfaces 103 between them. A particle 106 is disposed within one of the interfaces 103 between two of the layers 102. Although the particle 106 is illustrated as being within one of the interfaces 103, it should be understood that the particle 106 may be disposed on top of the uppermost layer 102 or below the lowermost layer 102, and is not limited herein. The particle 106 may cause defects in the deposition of subsequent layers 102, manifesting as displacement. The particle 106 may be opaque and may be made of a different material than the layers 102 of the workpiece 101.

[0052] Figure 3B An exemplary cross-sectional image 131 of the workpiece generated by processor 130 is illustrated. Cross-sectional image 131 includes pixels of a first color 132 indicating the interface 103 between layers 102, and pixels of a second color 133 indicating regions within each layer 102. While black is used for the first color 132 and white for the second color 133, different combinations of distinguishable colors may be used and are not limited herein. Based on the pixels of the first color 132, displacement of layer 102 due to defect 106 can be seen in cross-sectional image 131. Since particles 106 may be opaque, structured light pattern 111 may not transmit through particles 106, and there may be no reflection data from the underlying layer 102 or interface 103. Therefore, these areas are shown as having pixels of the second color 133.

[0053] In some embodiments, the processor 130 may communicate electronically with the display device 140. The processor 130 may be further configured to transmit a cross-sectional image 131 to the display device 140 for display. The display device 140 may be configured to display pixels having a first color 132 and pixels having a second color 133 (and any additional colors) to form the cross-sectional image 131.

[0054] Using system 100, a cross-sectional image 131 of workpiece 101 can be generated to identify its internal structure and any defects that may exist therein. The use of structured light pattern 111 is non-destructive to workpiece 101 and can produce a cross-sectional image 131 equivalent to FIB-based imaging.

[0055] Another embodiment of this disclosure provides method 200. (See reference...) Figure 4 Method 200 may include the following steps.

[0056] In step 210, a structured light pattern is projected onto a workpiece. The workpiece may be a multi-layered structure. For example, the workpiece may include multiple layers with interfaces between each layer. Each of the layers may be transparent or translucent, allowing the structured light pattern to be transmitted through the workpiece. In some embodiments, the workpiece may be a flat panel display. For example, the workpiece may include an OLED or an OLED-on-silicon panel. The structured light pattern may be generated by a structured light assembly including a light source and a pattern generator disposed in the optical path of the light source. The light source may be a lamp, fiber-coupled light, LED light, or a laser. The structured light pattern is generated by projecting light from the light source through the pattern generator. The pattern generator may be mechanical or electronic. For example, a mechanical pattern generator may be a patterned article comprising a piece of patterned photographic film or patterned glass. An electronic pattern generator may be a liquid crystal pattern generator (LCPG) capable of generating different patterns. The patterned article or LCPG may have high contrast, regular or random patterns, translucent features, and a minimum feature size corresponding to the sampling resolution of the imaging assembly. In some embodiments, the imaging assembly may include an array of light sources that form a structured light pattern without using a separate pattern generator. In any arrangement, the structured light pattern generated by the imaging assembly may be a grid or other pattern and is not limited herein. The structured light assembly may further include one or more optical elements, such as lenses, beam splitters, mirrors, filters, microscope objectives, etc., disposed in the optical path of the light source.

[0057] In step 220, an imaging assembly is used to capture multiple structured light images of the workpiece. The imaging assembly may include a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera. Each of the multiple structured light images may be captured with the imaging assembly focused at different depths of focus relative to the workpiece. The difference between each depth of focus may depend on the thickness of the workpiece and the resolution of the imaging system. In some embodiments, for a workpiece having a thickness of tens of micrometers, the difference between each depth of focus may be tens of nanometers. In other words, the difference between each depth of focus may be one-hundredth, one-thousandth, or any other dimensional difference of the workpiece thickness. It should be understood that reducing the difference between each depth of focus can capture more data but may multiply the number of images required to cover the thickness of the workpiece. In some embodiments, the multiple structured light images may include at least 100 images. Depending on the maximum speed of the camera sensor of the imaging assembly, the imaging assembly may be configured to capture images at 800 frames per second or more. The imaging assembly may further include one or more optical elements, such as lenses, beam splitters, mirrors, filters, microscope objectives, etc., disposed in the optical path of the camera. Optical elements can be configured to adjust the focal length, magnification, working distance, and / or numerical aperture of the imaging assembly. For example, the depth of focus can be set based on the arrangement of the optical elements in the imaging assembly. Depending on the magnification of the imaging assembly, the camera's field of view can cover the entire workpiece or only a portion of it.

[0058] In some embodiments, the workpiece may be placed on a stage, and step 220 may include... Figure 5 The following steps are shown in the image.

[0059] In step 221, the stage is moved to adjust the distance of the imaging assembly relative to the workpiece. For example, the stage may include one or more actuators or motors configured to move the stage in a plane (e.g., in the X and Y directions) and in a depth direction (e.g., the Z direction). The stage may move incrementally in the Z direction based on the difference between depths of focus set by the processor. Alternatively, the imaging assembly may be moved relative to the stage to adjust the distance of the imaging assembly relative to the workpiece. It should be understood that adjusting the distance between the imaging assembly and the workpiece changes the position of the depth of focus of the imaging assembly within the workpiece. The stage may also be moved in the X or Y direction to scan the workpiece relative to the imaging assembly at each distance.

[0060] In step 222, a structured light image of the workpiece is captured at each distance using the imaging assembly to obtain multiple structured light images corresponding to each depth of focus. In some embodiments where the camera's field of view only covers a portion of the workpiece, the structured light image of the workpiece can be captured after the stage has been moved to a different XY position at each distance in the Z direction.

[0061] Return to reference Figure 4In step 230, a cross-sectional image of the workpiece is generated based on multiple structured light images. For example, the cross-sectional image can be generated using data from reflections of structured light patterns corresponding to the workpiece at varying focal depths from multiple structured light images.

[0062] In some embodiments, step 230 may include Figure 6 The following steps are shown in the image.

[0063] In step 231, a cross section is defined through the workpiece. The cross section may intersect each of the multiple structured light images. The position and orientation of the cross section relative to the workpiece are not limited herein. The position and orientation of the cross section may be preset by the processor or selected by the user. For example, the cross section may be placed at a preset area of ​​interest on the workpiece or based on feedback from multiple structured light images (e.g., where defects exist in the workpiece).

[0064] In step 232, a focus fraction is determined for each pixel of the plurality of structured light images whose cross-sections intersect. In other words, each of the plurality of structured light images can be divided into a pixel array, and pixels whose cross-sections intersect can be selected for processing. For processing efficiency, the remaining pixels can be ignored, or the focus fraction of the remaining pixels can be determined to generate a multi-layer 3D image of the workpiece. The focus fraction can correspond to the reflection of the structured light pattern reflected by the workpiece at the corresponding depth of focus.

[0065] In step 233, the focus fraction of each pixel in the cross-section is combined to generate a cross-sectional image of the workpiece. For example, each pixel can be combined into a pixel array to form a cross-sectional image using each pixel of multiple structured light images and the focus fraction determined for each pixel.

[0066] In some embodiments, step 233 may include Figure 7 The following steps are shown in the image.

[0067] In step 233a, the focus score of each pixel in the cross-section is compared with a preset threshold. In some embodiments, the preset threshold may be greater than zero or equal to zero. When the depth of focus is at the interface between layers of a multilayer structure, the structured light pattern is reflected by the workpiece at the interface, and the focus score may be greater than the preset threshold. For example, the structured light pattern may be reflected from the interface between layers, and the intensity of the reflected light may be detected by the imaging assembly. When the depth of focus is within a layer of a multilayer structure, the structured light pattern may be reflected by the workpiece or may be transmitted through the workpiece, and the focus score may be less than the preset threshold. For example, the structured light pattern may be transmitted through the layer and not reflected, thereby not being detected by the imaging assembly, corresponding to a focus score of zero. Alternatively, the structured light pattern may be partially reflected from within the layer, but the focus score may be less than the preset threshold. It should be understood that, for example, the preset threshold may be calibrated for the material of the workpiece being inspected based on the range of intensity of the reflection detected by the imaging assembly.

[0068] In step 233b, each pixel in the cross-section with a focus score greater than a preset threshold is classified as an interface between layers in a multi-layered structure. Different types of layers can be classified based on the focus score value being greater than the preset threshold. For example, interfaces can reflect light differently based on the type / material of the layer at the interface, thereby generating different focus scores that can be used for classification.

[0069] In step 233c, a first color is assigned based on the classification of the interfaces between the layers in the multilayer structure. Different colors can be used to identify different types and materials of the layers at the interfaces. Therefore, a first color can be assigned based on the classification of the layers at the interfaces.

[0070] In step 233d, each pixel of the cross section with a focus score greater than a preset threshold is filled with the first color.

[0071] In step 233e, each pixel of the cross-section having a focus score less than a preset threshold is filled with a second color different from the first color. Therefore, the cross-sectional image can be defined by pixels having the first color and pixels having the second color. In embodiments where additional values ​​are assigned, each value can correspond to a different color distinguishable from the first and second colors. Thus, the cross-sectional image can illustrate the internal structure of the workpiece based on reflections at the interfaces between layers and the presence of any anomalies or defects within the workpiece. In embodiments where interfaces between layers can be classified based on focus scores higher than a preset threshold, different classifications can use different colors distinguishable from the first and second colors. Therefore, the cross-sectional image can use different colors to further illustrate the different materials / classifications of the various layers of the workpiece.

[0072] Using method 200, a cross-sectional image of the workpiece can be generated to identify its internal structure and any defects that may exist therein. The use of structured light patterns is non-destructive to the workpiece and can produce a cross-sectional image equivalent to FIB-based imaging.

[0073] Another embodiment of this disclosure provides a non-transitory computer-readable storage medium. The storage medium may include instructions stored thereon that, when executed by a processor, cause the processor to perform method 200. For example, the processor may be processor 130 of system 100.

[0074] Although this disclosure has been described with respect to one or more specific embodiments, it will be understood that other embodiments of this disclosure may be made without departing from the scope of this disclosure. Therefore, this disclosure is to be considered limited only by the appended claims and their reasonable interpretation.

Claims

1. A method comprising: A structured light pattern is projected onto a workpiece, wherein the workpiece is a multi-layered structure; An imaging assembly is used to capture multiple structured light images of the workpiece, each of which is captured when the imaging assembly is focused at a different depth of focus relative to the workpiece. and A cross-sectional image of the workpiece is generated based on the multiple structured light images.

2. The method of claim 1, wherein the plurality of structured light images comprises at least 100 images captured at different depths of focus.

3. The method of claim 1, wherein the workpiece is placed on a stage, and the imaging assembly is used to capture the plurality of structured light images of the workpiece, comprising: The stage is moved to adjust the distance between the imaging assembly and the workpiece; and The imaging assembly is used at each distance to capture structured light images of the workpiece to obtain multiple structured light images at different depths of focus.

4. The method of claim 1, wherein generating the cross-sectional image of the workpiece based on the plurality of structured light images comprises: Define a cross section passing through the workpiece, wherein the cross section intersects with each of the plurality of structured light images; Determine the focus fraction of each pixel of the plurality of structured light images intersecting the cross sections, wherein the focus fraction corresponds to the reflection of the structured light pattern reflected by the workpiece at a corresponding depth of focus; and The focus fraction of each pixel in the cross section is combined to generate the cross-sectional image of the workpiece.

5. The method of claim 4, wherein combining the focus fraction of each pixel in the cross-section to generate the cross-sectional image of the workpiece comprises: The focus score of each pixel in the cross section is compared with a preset threshold, wherein the preset threshold is greater than or equal to zero; Fill each pixel of the cross section with a focus score greater than the preset threshold with a first color; and Fill each pixel of the cross section with a focus score less than the preset threshold with a second color different from the first color; The cross-sectional image is defined by pixels having the first color and pixels having the second color.

6. The method of claim 5, wherein combining the focus fraction of each pixel in the cross-section to generate the cross-sectional image of the workpiece further comprises: Each pixel of the cross section having a focus score greater than the preset threshold is classified as being located at the interface between the layers of the multilayer structure. and The first color is assigned based on the classification of the interfaces between layers.

7. The method according to claim 1, wherein the workpiece is a flat panel display.

8. A non-transitory computer-readable storage medium comprising instructions stored thereon, the instructions causing the processor to: Controlling a structured light assembly to project a structured light pattern onto a workpiece, wherein the workpiece is a multi-layered structure; An imaging assembly is controlled to capture multiple structured light images of the workpiece, each of which is captured while the imaging assembly is focused at different heights relative to the workpiece; and A cross-sectional image of the workpiece is generated based on the plurality of structured light images received from the imaging assembly.

9. The storage medium of claim 8, wherein the plurality of structured light images comprises at least 100 images captured at different depths of focus.

10. The storage medium of claim 8, wherein the workpiece is placed on a stage, and further causes the processor to: Send a command to move the stage to adjust the distance of the imaging assembly relative to the workpiece; and The imaging assembly is used at each distance to capture structured light images of the workpiece to obtain multiple structured light images at different depths of focus.

11. The storage medium of claim 8, wherein the processor is further induced to: Define a cross section passing through the workpiece, wherein the cross section intersects with each of the plurality of structured light images; Determine the focus fraction of each pixel of the plurality of structured light images intersecting the cross sections, wherein the focus fraction corresponds to the reflection of the structured light pattern reflected by the workpiece at a corresponding depth of focus; and The focus fraction of each pixel in the cross section is combined to generate the cross-sectional image of the workpiece.

12. The storage medium of claim 11, wherein the processor is further caused to: The focus score of each pixel in the cross section is compared with a preset threshold, wherein the preset threshold is greater than or equal to zero; Fill each pixel of the cross section with a focus score greater than the preset threshold with a first color; and Fill each pixel of the cross section with a focus score less than the preset threshold with a second color different from the first color; The cross-sectional image is defined by pixels having the first color and pixels having the second color.

13. The storage medium of claim 12, wherein the processor is further caused to: Each pixel of the cross section having a focus score greater than the preset threshold is classified as being located at the interface between the layers of the multilayer structure; and The first color is assigned based on the classification of the interfaces between layers.

14. A system comprising: A structured light assembly configured to project a structured light pattern onto a workpiece, wherein the workpiece is a multi-layered structure; An imaging assembly configured to capture multiple structured light images of the workpiece, each of which is captured when the imaging assembly is focused at a different height relative to the workpiece; and A processor that communicates electronically with the structured light assembly and the imaging assembly, wherein the processor is configured to generate a cross-sectional image of the workpiece based on the plurality of structured light images received from the imaging assembly.

15. The system of claim 14, wherein the plurality of structured light images comprises at least 100 images captured at different depths of focus.

16. The system of claim 14, wherein the workpiece is placed on a stage, and the processor is further configured to: Send a command to move the stage to adjust the distance of the imaging assembly relative to the workpiece; and The imaging assembly is used at each distance to capture structured light images of the workpiece to obtain the plurality of structured light images at different depths of focus.

17. The system of claim 14, wherein the processor is further configured to: Define a cross section passing through the workpiece, wherein the cross section intersects with each of the plurality of structured light images; Determine the focus fraction of each pixel of the plurality of structured light images intersecting the cross sections, wherein the focus fraction corresponds to the reflection of the structured light pattern reflected by the workpiece at a corresponding depth of focus; and The focus fraction of each pixel in the cross section is combined to generate the cross-sectional image of the workpiece.

18. The system of claim 17, wherein the processor is further configured to: The focus score of each pixel in the cross section is compared with a preset threshold, wherein the preset threshold is greater than or equal to zero; Fill each pixel of the cross section with a focus score greater than the preset threshold with a first color; and Fill each pixel of the cross section with a focus score less than the preset threshold with a second color different from the first color; The cross-sectional image is defined by pixels having the first color and pixels having the second color.

19. The system of claim 18, wherein the processor is further configured to: Each pixel of the cross section having a focus score greater than the preset threshold is classified as being located at the interface between the layers of the multilayer structure; and The first color is assigned based on the classification of the interfaces between layers.

20. The system of claim 14, wherein the workpiece is a flat panel display.

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