Apparatus and method for fluorescence detection in electronic devices with high bright coaxial laser illumination

Abstract

In one embodiment, a system includes a laser light source configured to emit laser light; an optical fiber coupled to the laser light source and configured to guide the laser light along an illumination path; and an illumination optical assembly disposed in the illumination path and configured to direct the laser light on a workpiece. The workpiece emits fluorescent light along an emission path based on illumination from the laser light. The system further includes a collection optical assembly disposed in the emission path and configured to separate the fluorescent light from reflected laser light; and a detector disposed in the emission path and configured to generate one or more fluorescence images based on the fluorescence.

Description

Technical Field

[0001] This disclosure relates to inspection systems, and more specifically to fluorescence imaging for the inspection of electronic devices. Background Technology

[0002] The evolution of the electronics manufacturing industry places increasingly higher demands on yield management, and specifically on metrology and inspection systems. Critical dimensions continue to shrink, but the industry needs to reduce the time spent achieving high-yield, high-value production. Minimizing the total time from detecting a yield problem to resolving it maximizes the return on investment for electronics manufacturers.

[0003] Inspection processes are used at various stages of electronics manufacturing to detect defects in wafers, electronic devices, or circuits, leading to higher yields and thus higher profits. Inspection has always been a vital part of manufacturing electronic devices, such as integrated circuits (ICs) and printed circuit boards (PCBs), including assembly PCBs. However, as feature sizes shrink, inspection becomes even more critical for successfully manufacturing acceptable electronic devices, as even small defects can cause devices and assemblies to malfunction. For example, as feature sizes decrease, detecting defects in smaller sizes has become necessary, because even relatively small defects can introduce unwanted aberrations into the device.

[0004] Some inspection processes use fluorescence imaging to detect defects on PCBs. In these techniques, PCB illumination induces fluorescence emission from the substrate, and a camera captures images of the fluorescence emission to identify defects on the PCB. Existing systems typically use LEDs to illuminate the PCB. Unless the LEDs are angled relative to the substrate, strong reflections can occur from copper or other reflective surfaces on the substrate toward the camera. However, this results in reduced illumination intensity and inefficient diffuse illumination of the substrate between high aspect ratio (HAR) structures on the PCB, and image contrast is reduced due to poor activation of fluorescence emission in these areas.

[0005] Therefore, an improved fluorescence generation and detection process suitable for PCBs with HAR structures is needed. Summary of the Invention

[0006] Embodiments of this disclosure provide a system. The system may include: a laser source configured to emit laser light; an optical fiber coupled to the laser source and configured to guide the laser light along an illumination path; and an illumination optics assembly disposed in the illumination path and configured to guide the laser light onto a workpiece. The workpiece may emit fluorescence along the emission path based on illumination from the laser light.

[0007] The system may further include: a collecting optical assembly disposed in the emission path and configured to separate the fluorescence from the reflected laser light; and a detector disposed in the emission path and configured to generate one or more fluorescence images based on the fluorescence.

[0008] In some embodiments, the illumination from the laser light may be perpendicular to the workpiece.

[0009] In some embodiments, the laser source may have a power of 1 mW to 500 W.

[0010] In some embodiments, the laser source may be a first laser source. The system may further include: a second laser source configured to emit laser light having at least one wavelength and a different polarization than the first laser source; and an optical fiber coupler configured to combine the laser light from the first laser source and the laser light from the second laser source along a common illumination path in a single optical fiber.

[0011] In some embodiments, the optical fiber may include multiple optical fibers. Each optical fiber may be configured to guide the laser light along a separate illumination path, and the illumination optics assembly may be configured to guide the laser light in each of the separate illumination paths to illuminate a separate area of ​​the workpiece.

[0012] In some embodiments, the optical fiber may be a non-circular optical fiber.

[0013] In some embodiments, the illumination optics assembly may include: a collimating lens configured to collimate the laser light in the illumination path; a homogenizer configured to homogenize the laser light in the illumination path; and an objective lens configured to guide the laser light onto the workpiece.

[0014] In some embodiments, the collecting optical assembly may include a beam splitter disposed in the emission path and configured to guide the fluorescence toward the detector and to guide the reflected laser light away from the detector.

[0015] In some embodiments, the collecting optical assembly may include a spectral filter disposed in the emission path and configured to transmit one or more wavelength bands corresponding to the fluorescence and block one or more wavelength bands corresponding to the reflected laser light.

[0016] In some embodiments, the laser light may have a wavelength of 350 nm to 450 nm.

[0017] In some embodiments, the fluorescence may have a wavelength of 400 nm to 650 nm.

[0018] In some embodiments, the workpiece may be a substrate comprising one or more structures having an aspect ratio greater than 1:1.

[0019] In some embodiments, the laser source can be spatially separated from the illumination optics assembly via the optical fiber.

[0020] Another embodiment of this disclosure provides a method comprising: emitting laser light from a laser source; guiding the laser light along an illumination path using an optical fiber coupled to the laser source; directing the laser light onto a workpiece using an illumination optics assembly; emitting fluorescence from the workpiece along an emission path based on illumination from the laser light; separating the fluorescence from reflected laser light in the emission path using a collection optics assembly; and generating one or more fluorescence images based on the fluorescence received by a detector.

[0021] In some embodiments, emitting laser light from the laser source may include: emitting laser light from a first laser source; and emitting laser light from a second laser source having at least one wavelength and a different polarization than the first laser source.

[0022] In some embodiments, guiding the laser light along the illumination path using the optical fiber coupled to the laser source may include: guiding the laser light from the first laser source using a first optical fiber coupled to the first laser source; guiding the laser light from the second laser source using a second optical fiber coupled to the second laser source; and combining the laser light from the first laser source in the first optical fiber and the laser light from the second laser source in the second optical fiber along a common illumination path in a single optical fiber using an optical fiber coupler.

[0023] In some embodiments, the optical fiber may include multiple optical fibers, and guiding the laser light along the illumination path using the optical fibers coupled to the laser source may include: guiding the laser light along multiple illumination paths using the multiple optical fibers to illuminate multiple individual areas of the workpiece.

[0024] In some embodiments, guiding the laser light onto the workpiece using the illumination optics assembly may include: collimating the laser light in the illumination path using a collimating lens; homogenizing the laser light in the illumination path using a homogenizer; and guiding the laser light onto the workpiece using an objective lens.

[0025] In some embodiments, using the collecting optical assembly to separate the fluorescence from the laser light in the emission path may include: using a beam splitter to guide the fluorescence toward the detector; and using the beam splitter to guide the reflected laser light away from the detector.

[0026] In some embodiments, using the collecting optical assembly to separate the fluorescence from the laser light in the emission path may include: using a spectral filter to transmit one or more wavelength bands corresponding to the fluorescence; and using the spectral filter to block one or more wavelength bands corresponding to the reflected laser light. Attached Figure Description

[0027] 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:

[0028] Figure 1 This is a schematic diagram of a system according to an embodiment of the present disclosure;

[0029] Figure 2 This is a cross-sectional view of an exemplary workpiece according to an embodiment of the present disclosure;

[0030] Figure 3 This is a cross-sectional view of an exemplary optical fiber according to an embodiment of the present disclosure;

[0031] Figure 4 This is a schematic diagram of two laser sources connected to a single optical fiber according to an embodiment of the present disclosure;

[0032] Figure 5 This is a schematic diagram of a single laser source connected to multiple optical fibers according to an embodiment of the present disclosure;

[0033] Figure 6 This is a schematic diagram of a system according to another embodiment of the present disclosure;

[0034] Figure 7 This is a schematic diagram of a system according to another embodiment of the present disclosure;

[0035] Figure 8 This is a flowchart of a method according to an embodiment of the present disclosure;

[0036] Figure 9 This is a flowchart of a method according to an embodiment of the present disclosure;

[0037] Figure 10 This is a flowchart of a method according to an embodiment of the present disclosure;

[0038] Figure 11 A flowchart of a method according to an embodiment of this disclosure; and

[0039] Figure 12 This is a flowchart of a method according to an embodiment of the present disclosure. Detailed Implementation

[0040] While the claimed subject matter will be described based on certain 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 solely by reference to the appended claims.

[0041] refer to Figure 1 Embodiments of this disclosure provide a system 100. System 100 may be an inspection system configured to detect defects in a workpiece 101. As used herein, workpiece 101 may be a semiconductor front-end or back-end wafer, substrate, redistribution layer, panel, or another surface seeking to be inspected for defect detection. In some embodiments, workpiece 101 may include a substrate 102 comprising one or more high aspect ratio structures 103, such as… Figure 2 As shown in the diagram. For example, the high aspect ratio structure 103 may have an aspect ratio greater than 1:1. In some examples, the aspect ratio may be at least 2:1 or up to 10:1. The high aspect ratio structure 103 may cause attenuation of light arriving at the substrate 102 from certain angles. For example, an aspect ratio of 1:1 may cause attenuation of incident light at an angle of less than 45° to the substrate 102, an aspect ratio of 2:1 may cause attenuation of incident light at an angle of less than 63° to the substrate 102, and an aspect ratio of 10:1 may cause attenuation of incident light at an angle of less than 84° to the substrate 102. Therefore, the aspect ratio of the high aspect ratio structure 103 may limit the arrival of light perpendicular to (or within the angular range relative to the normal) on the substrate 102. The workpiece 101 may be mounted on a support 105. The support 105 may be a stage having at least two degrees of freedom. For example, the support 105 may be configured to move in two in-plane directions (e.g., the xy direction). The support 105 may be further configured to rotate and / or move in an out-of-plane direction (e.g., the z-direction). The support 105 may be moved by one or more actuators or other components, and is not limited herein. Alternatively, other components of the system 100 may be movable relative to the support 105.

[0042] System 100 may include a laser source 110. For example, laser source 110 may be a laser with a power of 1 mW to 500 W. Laser source 110 may be configured to emit laser light. Laser source 110 may be configured to emit laser light continuously and / or in pulsed mode. Strong laser pulses can provide the same energy as continuous lasers and can shorten imaging time. However, in some cases, continuous lasers can avoid the potential damage to the substrate caused by strong laser pulses or saturated fluorescence from the high peak power of strong laser pulses. Alternatively, many weak laser pulses can be used to shorten imaging time compared to continuous lasers and avoid damage or saturation caused by strong laser pulses. Laser light may have a wavelength of 350 nm to 450 nm. Specific parameters of laser source 110 can be configured based on a specific application to set the power, energy, wavelength, and beam size for detecting defects on workpiece 101.

[0043] System 100 may further include an optical fiber 120 of a circular or square shape having a core size of 200 to 500 micrometers. For example, optical fiber 120 may be a square optical fiber with a core size of 375 µm × 375 µm. Optical fiber 120 may include an input end 121 and an output end 122. Optical fiber 120 may be coupled to laser source 110. For example, the input end 121 of optical fiber 120 may be coupled to laser source 110. Thus, laser light emitted by laser source 110 can travel through optical fiber 120. Optical fiber 120 may be flexible to guide laser light along a nonlinear (i.e., curved) illumination path 111. It should be understood that high-power laser source 110 may have a large size that limits its placement and configuration within system 100. Optical fiber 120 can provide discrete paths for laser light to travel within system 100 to avoid the spatial limitations of laser source 110. It should also be understood that the high-power laser source 110 can generate heat and vibration, which may affect other components of the system 100 and potentially impact the stability and accuracy of the system 100. The length of the fiber optic cable 120 allows the laser source 110 to be isolated from other components of the system 100. In other words, the fiber optic cable 120 spatially isolates the laser source 110 from the workpiece 101 and other components of the system 100. This improves heat dissipation around the laser source 110, avoids volume constraints in the optical system, and reduces vibration transmission from the laser source 110 to the system 100.

[0044] The cross-section of fiber 120 can be non-circular, such as... Figure 3As shown in the illustration. For example, optical fiber 120 may have a cross-section that is square, rectangular, elliptical, or other non-circular in shape. This non-circular fiber can disrupt the laser light as it travels through optical fiber 120, thereby improving the uniformity of the laser light illuminating workpiece 101 and reducing spot contrast. Optical fiber 120 may include a core 125 surrounded by a sheath 126. Sheath 126 may be made of a flexible material (e.g., metal or plastic) to conform to the flexibility of core 125. The sheath also protects core 125 from damage that could affect how optical fiber 120 homogenizes the laser light. In some examples, optical fiber 120 may include an optical fiber bundle comprising multiple optical fibers described herein.

[0045] In some embodiments, system 100 may include more than one laser source 110. For example, such as Figure 4 As shown, system 100 may include a first laser source 110a and a second laser source 110b. The second laser source 110b may be configured to emit laser light having at least one different wavelength and a different polarization than the first laser source 110a. For example, the first laser source 110a may emit laser light with a wavelength of 395 nm, and the second laser source 110b may emit laser light with a wavelength of 405 nm. Different wavelengths can excite different molecules used with different types of substrates and can increase the overall excitation power. Alternatively, the first laser source 110a and the second laser source 110b may emit light with the same wavelength but orthogonally polarized, which can increase (or almost double) the output power.

[0046] A first optical fiber 120a may be coupled to a first laser source 110a, and a second optical fiber 120b may be coupled to a second laser source 110b. An optical fiber coupler 115 connects the first optical fiber 120a and the second optical fiber 120b to the input of the optical fiber 120, thereby combining laser light from the first laser source 110a and the second laser source 110b along a common illumination path 111 in a single optical fiber 120. The optical fiber coupler 115 may be wavelength selective, such as a wavelength division multiplexing (WDM) device or a polarization-maintaining coupler. The system 100 may include additional laser sources connected to the optical fiber coupler 115 via corresponding optical fibers. In some embodiments, a free-space beam combiner may be used to collect laser light emitted from the first laser source 110a and the second laser source 110b without requiring connection via the first optical fiber 120a and the second optical fiber 120b. In such examples, a free-space beam combiner can combine collected laser light from a first laser source 110a and laser light from a second laser source 110b along a common illumination path 111 in a single optical fiber 120. The laser sources can be selected based on their wavelengths for detecting defects on a workpiece 101 in a particular application. By combining different wavelengths of laser light from more than one laser source 110, the workpiece 101 can be illuminated with several wavelengths, which can improve the quality of fluorescence emission and fluorescence images. The first laser source 110a and the second laser source 110b can be switched on and off to select which wavelengths of light are used to illuminate the workpiece 101. In some embodiments, laser light from one of the first laser source 110a and the second laser source 110b can be used to illuminate a portion of the workpiece 101, and laser light from the other (or both) of the first laser source 110a and the second laser source 110b can be used to illuminate other portions of the workpiece 101.

[0047] In some embodiments, system 100 may include multiple optical fibers 120. For example, such as Figure 5 As shown, each of the plurality of optical fibers 120 can be coupled to a laser source 110 and can be configured to guide laser light along a plurality of illumination paths 111. In some embodiments, there may be n illumination paths (where n ≥ 2), including a first illumination path 111a, a second illumination path 111b, and so on up to an nth illumination path 111n. Because each optical fiber 120 is flexible, each of the plurality of illumination paths 111 can diverge in a non-linear direction. Therefore, the plurality of illumination paths 111 can be configured to illuminate a single region of workpiece 101 or a single workpiece 101. The single region can be continuous or discontinuous.

[0048] In some embodiments, the system 100 may include a plurality of laser light sources 110 and a plurality of optical fibers 120 (i.e., Figure 4 and Figure 5(The examples shown herein are combinations thereof and are not limited herein.) In the examples, system 100 may not include fiber coupler 115, and first fiber 120a and second fiber 120b form a fiber bundle that defines multiple fibers 120 guiding laser light along multiple illumination paths 111. Alternatively, multiple fibers 120 connected to a single laser source 110 may form a fiber bundle.

[0049] System 100 may further include an illumination optics assembly 130. The illumination optics assembly 130 may be disposed in the illumination path 111. For example, after laser light has been guided through fiber optic 120, it may pass through the illumination optics assembly 130. The illumination optics assembly 130 may be configured to guide laser light onto workpiece 101. The laser light may be focused on workpiece 101 or workpiece 101 may be defocused. The illumination optics assembly 130 may include one or more optical elements, such as lenses, beam splitters, mirrors, filters, etc. In embodiments where multiple fibers 120 are present, the illumination optics assembly 130 may include one or more optical elements in each of the n illumination paths configured to guide laser light onto a separate area of ​​workpiece 101.

[0050] In some embodiments, the illumination optics assembly 130 may include a collimating lens 131. The collimating lens 131 may be coupled to the output of the optical fiber 120. The collimating lens 131 may be configured to collimate the laser light in the illumination path 111 after it has passed through the optical fiber 120.

[0051] The illumination optics assembly 130 may further include a homogenizer 132. The homogenizer 132 may be disposed in the illumination path 111, downstream of the collimating lens 131. The homogenizer 132 may be configured to homogenize the laser light in the illumination path 111. In some embodiments, the homogenizer 132 may include a microlens array.

[0052] The illumination optics assembly 130 may further include an objective lens 133. The objective lens 133 may be positioned in the illumination path 111, downstream of the homogenizer 132. The objective lens 133 may be configured to direct laser light onto the workpiece 101. As used herein, the term "objective lens" refers to a lens located near the workpiece 101 and used for imaging the workpiece 101, but is not limited to a particular type of lens. The area of ​​the workpiece 101 illuminated by the laser light may depend on the field of view of the objective lens 133. For example, the size of the laser-illuminated area on the workpiece 101 may be approximately 1 mm by 1 mm.

[0053] The illumination optics assembly 130 may further include a first beam splitter 134. The first beam splitter 134 may be positioned in the illumination path 111, upstream of the objective lens 133. The first beam splitter 134 may be configured to direct laser light toward the objective lens 133.

[0054] The illumination optics assembly 130 may include any other optical elements. Examples of such optical elements include, but are not limited to, polarizing components, spectral filters, spatial filters, refractive optics, reflective optics, diffractive optics, apodizers, beam splitters, apertures, and the like, which may include any suitable optical elements known in the art.

[0055] Illumination from the laser light can be perpendicular to the workpiece 101. For example, fiber optic 120 can guide illumination path 111 perpendicular to workpiece 101, and / or illumination optics assembly 130 can guide laser light onto workpiece 101 in a direction perpendicular to workpiece 101. It should be understood that illumination from the laser light can be substantially perpendicular to workpiece 101, for example, at ±45°, ±27°, or ±6° to a direction orthogonal to workpiece 101, the angular range being limited by the aspect ratio of the high aspect ratio structure 103 of workpiece 101. Therefore, for a workpiece 101 including substrate 102 and one or more high aspect ratio structures 103, the laser light will directly illuminate the substrate 102 between the HAR structures 103 to improve illumination compared to light guided from other angles.

[0056] Based on illumination from the laser light, the workpiece 101 can fluoresce, thereby emitting fluorescence along the emission path 112. Depending on the laser wavelength and the substrate composition and structure, the fluorescence will be at a wavelength longer than the laser wavelength; for example, the fluorescence spectrum may be from 400 nm to 650 nm. Although the illumination path 111 is configured such that the illumination from the laser light is perpendicular to the workpiece 101, fluorescence can be emitted from the workpiece 101 over a wide angular range, centered along the emission path 112, which may be perpendicular to the workpiece 101. Therefore, the emission path 112 refers to the direction in which fluorescence will be observed, and may or may not be the direction of strongest fluorescence. It should be understood that the illumination from the laser light may also cause the laser light to be reflected by the workpiece 101. Therefore, the emission path 112 may include both reflected laser light and fluorescence. A first beam splitter 134 may be disposed in the emission path such that some of the reflected laser light can be redirected by the first beam splitter 134, while the remaining reflected laser light and fluorescence can be transmitted through the first beam splitter 134 along the emission path 112.

[0057] System 100 may further include a collecting optical assembly 140. The collecting optical assembly 140 may be disposed in the emission path 112. For example, after fluorescence is emitted from workpiece 101 and laser light is reflected by workpiece 101, both fluorescence and reflected laser light may pass through the collecting optical assembly 140. The collecting optical assembly 140 may be configured to separate the fluorescence from the reflected laser light. For example, the fluorescence and reflected laser light may have different wavelengths, and the collecting optical assembly 140 may be configured to separate the fluorescence from the reflected laser light based on the different wavelengths of the fluorescence and reflected laser light. The collecting optical assembly 140 may include one or more optical elements, such as lenses, beam splitters, mirrors, filters, etc.

[0058] System 100 may further include detector 150, such as a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera. Detector 150 may be positioned in emission path 112, downstream of collecting optics assembly 140. Detector 150 may be configured to generate one or more fluorescence images based on fluorescence. For example, fluorescence may be directed to detector 150 after collecting optics assembly 140 separates fluorescence from reflected laser light. Thus, bright reflected laser light will not obscure the fluorescence signal, thereby producing a sharper, high-contrast fluorescence image. In some embodiments, a time delay may exist between the time when laser source 110 illuminates workpiece 101 and the time when detector 150 captures an image. For example, detector 150 may be triggered to capture an image after laser source 110 is turned off. Therefore, fluorescence emitted from workpiece 101 may last longer than reflected laser light, so less reflected laser light may need to be separated from emission path 112 before reaching detector 150.

[0059] In some embodiments, the collecting optical assembly 140 may include a spectral filter 142, such as Figure 1 As shown in the diagram, a spectral filter 142 can be disposed in the emission path 112, upstream of the detector 150. The spectral filter 142 can be a notch filter, a long-pass filter, or other types of filter. The spectral filter 142 can be configured to transmit one or more wavelength bands corresponding to fluorescence and block one or more wavelength bands corresponding to reflected laser light. For example, the spectral filter 142 can have a cut-on wavelength of 450 nm. Therefore, the spectral filter 142 can prevent bright laser light outside the fluorescence wavelength band from reaching the detector 150.

[0060] In some embodiments, the collecting optical assembly 140 may include a second beam splitter 141, such as Figure 6As shown in the diagram. A second beamsplitter 141 can be positioned in the emission path 112, between the workpiece 101 and the detector 150. The second beamsplitter 141 can be configured to guide fluorescence toward the detector 150 and guide reflected laser light away from the detector 150. For example, the second beamsplitter 141 can be configured to reflect a wavelength band corresponding to either the fluorescence or the reflected laser light, and the second beamsplitter 141 can be further configured to transmit the remaining wavelength. Thus, by selectively reflecting / transmitting wavelength bands, fluorescence and reflected laser light can be separated. The second beamsplitter 141 can guide the reflected laser light to the beam trap 143. In some examples, fluorescence from a high-fluorescence substrate can be used only with the second beamsplitter 141 (i.e., without using the spectral filter 142) to produce a high-contrast fluorescence image.

[0061] In some embodiments, the collecting optical assembly 140 may include both a second beam splitter 141 and a spectral filter 142, such as Figure 7 As shown in the diagram, a spectral filter 142 can be positioned in the emission path 112, between the second beam splitter 141 and the detector 150. It should be understood that the spectral filter 142 can attenuate reflected laser light more strongly than the second beam splitter 141. Therefore, the detector 150 can receive a clearer fluorescence band that can be used to generate a sharper, high-contrast fluorescence image.

[0062] The collecting optical assembly 140 may include any other optical elements. Examples of such optical elements include, but are not limited to, polarizing components, spectral filters, spatial filters, reflective optics, refractive optics, diffractive optics, apodizers, beam splitters, apertures, and the like, which may include any suitable optical elements of this kind known in the art.

[0063] System 100 may further include processor 160. Processor 160 may include a microprocessor, microcontroller or other device.

[0064] Processor 160 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 160 can receive output. Processor 160 may be configured to perform certain functions using the output. Inspection tools may receive instructions or other information from processor 160. Processor 160 may optionally communicate electronically with another inspection tool, metrology tool, repair tool, or auditing tool (not specified) to receive additional information or send instructions.

[0065] Processor 160 may be part of a variety of systems, including personal computer systems, graphics computers, mainframe computer systems, workstations, network appliances, Internet appliances, or other devices. Subsystems or systems may also include any suitable processor known in the art, such as a parallel processor. Additionally, subsystems or systems may include a platform with high-speed processing and software as a standalone or networked tool.

[0066] Processor 160 may be located in system 100 or another device, or otherwise be part of system 100 or another device. In examples, processor 160 may be part of a separate control unit or in a centralized quality control unit. Multiple processors 160 may be used to define multiple subsystems of system 100.

[0067] Processor 160 can be implemented in practice by 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 by any combination of hardware, software, and firmware. Program code or instructions for processor 160 to perform various methods and functions can be stored in a readable storage medium (e.g., memory).

[0068] If system 100 comprises more than one subsystem, then different processors 160 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 (several) additional subsystems via any suitable transmission medium, which may include any suitable wired and / or wireless transmission medium known in the art. Two or more of such subsystems can also be effectively coupled via a shared computer-readable storage medium (not shown).

[0069] Processor 160 may be configured to perform several functions using the output of system 100 or other outputs. For example, processor 160 may be configured to send outputs to an electronic data storage unit or another storage medium. Processor 160 may be further configured as described herein.

[0070] Processor 160 may be configured according to any of the embodiments described herein. Processor 160 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.

[0071] Processor 160 may be communicatively coupled to any of the various components or subsystems of system 100 in any manner known in the art. Furthermore, processor 160 may be configured to receive and / or acquire data or information from other systems (e.g., inspection results from an inspection system (e.g., an auditing tool), a remote database containing design data, and the like) via a transmission medium, which may include wired and / or wireless portions. In this way, the transmission medium can serve as a data link between processor 160 and other subsystems of system 100 or systems external to system 100. The various steps, functions, and / or operations of system 100 and 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) may be transmitted via 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 performed by a single processor 160 (or computer subsystem) or alternatively by multiple processors 160 (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.

[0072] The processor 160 can communicate electronically with the detector 150. For example, the processor 160 can receive one or more fluorescence images from the detector 150 via wired or wireless transmission.

[0073] The processor 160 may further communicate electronically with the support 105. For example, the processor 160 may be configured to control one or more actuators to move the support 105, thereby changing the position of the laser beam illuminating the workpiece 101.

[0074] The processor 160 may further communicate electronically with the laser source 110. For example, the processor 160 may be configured to control the laser source 110 to emit laser light (e.g., turn it on / off) and adjust parameters of the laser source 110 to adjust parameters of the generated laser light (e.g., intensity, wavelength, beam size). In some embodiments, the processor 160 may be configured to independently control the first laser source 110a, the second laser source 110b, and any additional laser source 110.

[0075] Using system 100, fluorescence detection on substrates with HAR structures can be improved. For example, laser source 110 can be used to illuminate a large area on workpiece 101 with high intensity and uniformity compared to LEDs with low power and brightness. Laser source 110 also emits a narrower spectrum of light compared to LEDs, which is more efficiently separated from emitted fluorescence. By coupling laser source 110 to optical fiber 120, laser source 110 can be isolated from workpiece 101 and other components of system 100, allowing for improved management of heat flow and ventilation. Because optical fiber 120 is flexible, illumination path 111 can be guided within the system so that illumination is coaxial with the optical axis of objective lens 133 (i.e., perpendicular to workpiece 101), which effectively illuminates between HAR structures on workpiece 101. Furthermore, collection optics assembly 140 can be configured to separate fluorescence from reflected laser light, allowing the detector to acquire a clear fluorescence image with high contrast.

[0076] Another embodiment of this disclosure provides a method 200. Method 200 can be applied to an inspection system configured to detect defects in a workpiece. As used herein, the workpiece may be a semiconductor wafer, substrate, panel, or another surface seeking to be inspected for defect detection. In some embodiments, the workpiece may include a substrate comprising one or more high aspect ratio structures. Figure 8 As shown in the figure, method 200 may include the following steps.

[0077] In step 210, laser light is emitted from a laser source. For example, the laser source may be a multimode diode laser with a power of 1 mW to 500 W. The laser source may be configured to emit laser light along an illumination path. The laser source may be configured to emit laser light continuously and / or in pulsed mode. Strong laser pulses can provide the same energy as continuous lasers and can shorten imaging time. However, in some cases, continuous lasers can avoid potential damage to the substrate from strong laser pulses or saturated fluorescence from the high peak power of strong laser pulses. Alternatively, many weak laser pulses can be used to shorten imaging time compared to continuous lasers and avoid damage or saturation caused by strong laser pulses. The laser light may have a wavelength of 350 nm to 450 nm. Specific parameters of the laser source can be configured based on a specific application to set the power, energy, wavelength, and beam size for detecting defects on a workpiece.

[0078] In step 220, an optical fiber coupled to the laser source is used to guide the laser light along the illumination path. For example, the input end of the optical fiber can be coupled to the output end of the laser source. Therefore, the laser light emitted by the laser source can travel through the optical fiber. The optical fiber can be flexible to guide the laser light along a non-linear (i.e., curved) illumination path. It should be understood that high-power laser sources can have large dimensions that limit their placement and configuration within the inspection system. The optical fiber can provide discrete paths for the laser light to travel within the inspection system, avoiding spatial limitations of the laser source. It should also be understood that high-power laser sources can generate heat or vibration, which may affect other components of the inspection system and potentially impact the system's stability and accuracy. The length of the optical fiber allows the laser source to be isolated from other components of the system. In other words, the optical fiber can spatially separate the laser source from the workpiece and other components of the system. This improves heat flow and ventilation around the laser source.

[0079] The optical fiber can have a circular or square shape with a core size of 200 to 500 micrometers. For example, the optical fiber can be a square fiber with a core size of 375 µm × 375 µm. In some embodiments, the optical fiber can be non-circular. This non-circular fiber can disrupt the laser light as it travels through the fiber, thereby improving the uniformity of the laser light illuminating the workpiece. The optical fiber may include a core surrounded by a sheath. The sheath may be made of a flexible material (e.g., metal or plastic) to conform to the flexibility of the core. The sheath also protects the fiber core from damage that could affect how the fiber homogenizes the laser light. In some examples, the optical fiber may include a bundle of optical fibers containing multiple fibers.

[0080] In step 230, an illumination optics assembly is used to guide the laser light onto the workpiece. For example, after the laser light is guided through an optical fiber, it may pass through the illumination optics assembly. The laser light may be focused on the workpiece, or the workpiece may be out of focus. The illumination optics assembly may include one or more optical elements, such as lenses, beam splitters, mirrors, filters, etc. The area of ​​the workpiece illuminated by the laser light may depend on the field of view of the objective lens. For example, the size of the laser-illuminated area on the workpiece may be approximately 1 mm by 1 mm.

[0081] Illumination from laser light can be perpendicular to the workpiece. For example, optical fibers can guide the illumination path perpendicular to the workpiece, and / or illumination optics assemblies can guide the laser light onto the workpiece in a direction perpendicular to the workpiece. It should be understood that illumination from laser light can be substantially perpendicular to the workpiece, for example, at ±45°, ±27°, or ±6° to a direction orthogonal to the workpiece, the angular range being limited by the aspect ratio of the high aspect ratio structure of the workpiece. Therefore, for a workpiece comprising a substrate and one or more high aspect ratio structures, laser light will directly illuminate the substrate between the HAR structures to improve illumination compared to light guided from other angles.

[0082] In step 240, fluorescence is emitted from the workpiece along the emission path based on illumination from the laser light. Depending on the laser wavelength and the substrate composition and structure, the fluorescence will be at a wavelength longer than the laser wavelength; for example, the fluorescence spectrum may be from 400 nm to 650 nm. Although the illumination path is configured such that the illumination from the laser light is perpendicular to the workpiece, fluorescence can be emitted from the workpiece over a wide angular range, centered along an emission path that may be perpendicular to the workpiece. Therefore, the emission path refers to the direction in which fluorescence will be observed, and may or may not be the direction in which the fluorescence is strongest. It should be understood that illumination from the laser light may also cause the laser light to be reflected by the workpiece. Therefore, the emission path may include both reflected laser light and fluorescence.

[0083] In step 250, a collecting optical assembly is used to separate the fluorescence and reflected laser light in the emission path. For example, after fluorescence is emitted from the workpiece and laser light is reflected by the workpiece, the fluorescence and reflected laser light can pass through the collecting optical assembly. In some embodiments, the fluorescence and reflected laser light may have different wavelengths, and the collecting optical assembly may be configured to separate the fluorescence and reflected laser light based on the different wavelengths of the fluorescence and reflected laser light. The collecting optical assembly may include one or more optical elements, such as lenses, beam splitters, mirrors, filters, etc.

[0084] In step 260, one or more fluorescence images are generated based on the fluorescence received by a detector (e.g., a camera based on a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS)). After the collecting optical assembly separates the fluorescence from the reflected laser light, the fluorescence can be directed to the detector. Therefore, the bright reflected laser light will not obscure the fluorescence signal, thereby producing a sharper, high-contrast fluorescence image. In some embodiments, a time delay may exist between the time the laser source illuminates the workpiece and the time the detector captures the image. For example, the detector can be triggered to capture the image after a delay of less than 1 μs after the laser source is turned off. Therefore, the fluorescence emitted from the workpiece can last longer than the reflected laser light, so that less reflected laser light may need to be separated from the emission path before reaching the detector, or filters or beam splitters may not be required to separate the light.

[0085] In some embodiments, more than one laser source may be used. For example... Figure 9 As shown in the diagram, step 210 may include the following steps.

[0086] In step 211, laser light is emitted from the first laser source.

[0087] In step 212, laser light with at least one different wavelength and different polarization than that of the first laser source is emitted from the second laser source. For example, the first laser source may emit laser light with a wavelength of 395 nm, and the second laser source may emit laser light with a wavelength of 405 nm. Different wavelengths can excite different molecules used with different types of substrates and can increase the total excitation power. Alternatively, the first and second laser sources may emit light with the same wavelength but orthogonally polarized, which can increase (or almost double) the output power.

[0088] Although Figure 9 It is noted that step 212 is performed after step 211, but it should be understood that step 212 may be performed in parallel with step 211 or before step 211, and is not limited herein.

[0089] Each laser source can be coupled to its own optical fiber. For example... Figure 10 As shown in the diagram, step 220 may include the following steps.

[0090] In step 221, the laser light from the first laser source is guided by the first optical fiber coupled to the first laser source.

[0091] In step 222, the laser light from the second laser source is guided by a second optical fiber coupled to the second laser source.

[0092] In step 223, a fiber optic coupler is used to combine the laser light exiting the first fiber and the laser light exiting the second fiber along a common illumination path into a single fiber. The fiber optic coupler can be wavelength selective, such as a wavelength division multiplexing (WDM) device.

[0093] Additional laser sources can be connected to the fiber optic coupler via corresponding optical fibers. The laser sources can be selected based on their wavelengths for detecting defects on a workpiece in a specific application. By combining laser light of different wavelengths from more than one laser source, the workpiece can be illuminated with several wavelengths, which improves the quality of fluorescence emission and fluorescence images. The first and second laser sources can be switched on and off to select which wavelengths of light are used to illuminate the workpiece. In some embodiments, laser light from one of the first and second laser sources can be used to illuminate a portion of the workpiece, while laser light from the other (or both) of the first and second laser sources can be used to illuminate other portions of the workpiece.

[0094] In some embodiments, the optical fiber may include multiple optical fibers. For example... Figure 10 As shown in the diagram, step 220 may further include the following.

[0095] In step 225, multiple optical fibers are used to guide laser light along multiple illumination paths to illuminate multiple individual regions of the workpiece. Because each fiber is flexible, each of the multiple illumination paths can diverge in a non-linear direction. Therefore, the multiple illumination paths can be configured to illuminate individual regions of the workpiece or individual parts of the workpiece. The individual regions can be continuous or discontinuous.

[0096] In some embodiments, step 225 may be performed after step 223 described above. In other words, after the laser light from the first and second laser sources is combined with the fiber optic coupler, multiple optical fibers may guide the laser light along multiple illumination paths. Alternatively, step 225 may be performed without steps 221 to 223. In other words, laser light from a single laser source may be guided by multiple optical fibers along multiple illumination paths.

[0097] In some embodiments, step 225 may be performed without step 223 as described above. In other words, the first and second optical fibers guide laser light from the first laser source and laser light from the second laser source along separate illumination paths. These optical fibers may be combined into an optical fiber bundle.

[0098] In some embodiments, step 230 may include Figure 11 The following steps are shown in the document.

[0099] In step 231, a collimating lens is used to collimate the laser light in the illumination path. The collimating lens can be coupled to the output end of the optical fiber.

[0100] In step 232, a homogenizer is used to homogenize the laser light in the illumination path. The homogenizer may be positioned in the illumination path, downstream of the collimating lens. In some embodiments, the homogenizer may include a microlens array.

[0101] In step 233, the laser beam is guided onto the workpiece using an objective lens. The objective lens can be positioned in the illumination path, downstream of the homogenizer.

[0102] In some embodiments, step 250 may include Figure 12 The following steps are shown in the document.

[0103] In step 251, a beam splitter is used to guide the fluorescence toward the detector and to guide the reflected laser light away from the detector. For example, the beam splitter may be configured to reflect a wavelength band corresponding to either the fluorescence or the reflected laser light, and may be further configured to transmit the remaining wavelengths. Thus, by selectively reflecting / transmitting wavelength bands, the fluorescence and the reflected laser light can be separated.

[0104] In step 252, a spectral filter is used to transmit one or more wavelength bands corresponding to fluorescence and to block one or more wavelength bands corresponding to reflected laser light. It should be understood that a spectral filter can attenuate reflected laser light more effectively than a beam splitter. Therefore, the detector can receive clearer fluorescence bands that can be used to generate a sharper, high-contrast fluorescence image.

[0105] Method 200 improves fluorescence detection on substrates with HAR structures. For example, a laser source can be used to illuminate large areas of a workpiece with high intensity and uniformity compared to LEDs with low power and brightness. By coupling the laser source to an optical fiber, the laser source can be isolated from the workpiece and other components of the system, allowing for improved management of heat flow and ventilation. Because the optical fiber is flexible, the illumination path can be guided within the system so that the illumination is coaxial with the optical axis of the objective (i.e., perpendicular to the workpiece), which effectively illuminates between HAR structures on the workpiece. Furthermore, the collection optics can be configured to separate the fluorescence from the reflected laser light, allowing the detector to acquire a clear fluorescence image with high contrast.

[0106] 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 system comprising: A laser source configured to emit laser light; An optical fiber coupled to the laser source and configured to guide the laser light along the illumination path; An illumination optics assembly disposed in the illumination path and configured to guide the laser light onto a workpiece, wherein the workpiece emits fluorescence along the emission path based on illumination from the laser light; An optical assembly is collected, which is placed in the emission path and configured to separate the fluorescence from the reflected laser light; and A detector, which is placed in the emission path and configured to generate one or more fluorescence images based on the fluorescence.

2. The system of claim 1, wherein the illumination from the laser light is perpendicular to the workpiece.

3. The system according to claim 1, wherein the laser source has a power of 1 mW to 500 W.

4. The system according to claim 1, wherein the laser source is a first laser source, and the system further comprises: A second laser source is configured to emit laser light having at least one wavelength and a different polarization than the first laser source; and An optical fiber coupler configured to combine laser light from the first laser source and laser light from the second laser source along a common illumination path in a single optical fiber.

5. The system of claim 1, wherein the optical fiber comprises a plurality of optical fibers, each configured to guide the laser light along a separate illumination path, and the illumination optics assembly is configured to guide the laser light in each of the separate illumination paths to illuminate a separate area of ​​the workpiece.

6. The system according to claim 1, wherein the optical fiber is a non-circular optical fiber.

7. The system of claim 1, wherein the illumination optics assembly comprises: A collimating lens configured to collimate the laser light in the illumination path; A homogenizer configured to homogenize the laser light in the illumination path; and An objective lens, configured to direct the laser light onto the workpiece.

8. The system of claim 1, wherein the collecting optical assembly comprises: A beam splitter is disposed in the emission path and configured to guide the fluorescence toward the detector and to guide the reflected laser light away from the detector.

9. The system of claim 1, wherein the collecting optical assembly comprises: A spectral filter is disposed in the emission path and configured to transmit one or more wavelength bands corresponding to the fluorescence and block one or more wavelength bands corresponding to the reflected laser light.

10. The system of claim 1, wherein the laser light has a wavelength of 350 nm to 450 nm.

11. The system of claim 1, wherein the fluorescence has a wavelength of 400 nm to 650 nm.

12. The system of claim 1, wherein the workpiece is a substrate comprising one or more structures having an aspect ratio greater than 1:

1.

13. The system of claim 1, wherein the laser source is spatially separated from the illumination optics assembly via the optical fiber.

14. A method comprising: Emitting laser light from a laser source; The laser light is guided along the illumination path using an optical fiber coupled to the laser source; The laser beam is guided onto the workpiece using an illumination optics assembly; Fluorescence is emitted from the workpiece along the emission path based on illumination from the laser light; The fluorescence is separated from the reflected laser light in the emission path using a collecting optical assembly; and One or more fluorescence images are generated based on the fluorescence received by the detector.

15. The method of claim 14, wherein the illumination from the laser light is perpendicular to the workpiece.

16. The method of claim 14, wherein: Emitting laser light from the laser source includes: Laser light is emitted from the first laser source; and The second laser source emits laser light with at least one different wavelength and different polarization than the first laser source; and Guiding the laser light along the illumination path using the optical fiber coupled to the laser source includes: The laser light from the first laser source is guided by a first optical fiber coupled to the first laser source; The laser light from the second laser source is guided using a second optical fiber coupled to the second laser source; and A fiber optic coupler is used to combine the laser light from the first laser source in the first fiber and the laser light from the second laser source in the second fiber along a common illumination path into a single fiber.

17. The method of claim 14, wherein the optical fiber comprises a plurality of optical fibers, and guiding the laser light along the illumination path using the optical fibers coupled to the laser source comprises: The laser light is guided along multiple illumination paths using the multiple optical fibers to illuminate multiple individual areas of the workpiece.

18. The method of claim 14, wherein guiding the laser light onto the workpiece using the illumination optics assembly comprises: The laser light in the illumination path is collimated using a collimating lens; The laser light in the illumination path is homogenized using a homogenizer; and The laser light is guided onto the workpiece using an objective lens.

19. The method of claim 14, wherein using the collecting optical assembly to separate the fluorescence from the laser light in the emission path comprises: A beam splitter is used to guide the fluorescence toward the detector; and The beam splitter is used to guide the reflected laser light away from the detector.

20. The method of claim 14, wherein using the collecting optical assembly to separate the fluorescence from the laser light in the emission path comprises: A spectral filter is used to transmit one or more wavelength bands corresponding to the fluorescence; and The spectral filter is used to block one or more wavelength bands corresponding to the reflected laser light.

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