A detection system and a detection method

Abstract

The application discloses a detection system and a detection method. The detection system comprises a carrier platform, an illumination assembly, and a plurality of detection channels. Each detection channel is configured with at least one detector. The plurality of detection channels comprises a first detection channel, a second detection channel, a third detection channel, and a fourth detection channel. The carrier platform is used for carrying a to-be-detected object. The illumination assembly is configured to emit a detection light beam to the to-be-detected object, and the detection light beam is scattered by the to-be-detected object to form at least one signal light beam. The plurality of detection channels are respectively configured to image and collect signal light emitted from a corresponding detection area, and generate defect detection information of the to-be-detected object according to the signal light. The coplanar four detection channels are symmetrically distributed on both sides of a target normal line, and the incident plane and the detection plane are perpendicular, so as to better match the distribution law of the scattered light intensity of different types of defects, so that the detection system has better signal light collection effect for different types of defects, and the detection precision and sensitivity are improved.

Description

Technical Field

[0001] This invention relates to the field of detection technology, and in particular to a detection system and detection method. Background Technology

[0002] Currently, surface defects of the test object are typically identified using a detection system based on scattered light imaging. For example, if a wafer has defects such as grooves, particles, or scratches, it can cause the chip fabricated from the wafer to fail. Therefore, surface defects of the wafer need to be detected before application.

[0003] In related technologies, multiple detection channels are typically used to detect the same object under test in order to obtain defect information from different angles of the object under test.

[0004] Taking semiconductor chips as an example, any contaminants (such as foreign objects or particles from the manufacturing process) or defects (such as scratches and dents) on a semiconductor chip with physical dimensions close to or larger than the final product's feature size are harmful and must be strictly monitored throughout the manufacturing process. Therefore, surface defect detection on patternless wafers has important applications in many semiconductor fields, including: product quality inspection by wafer manufacturers; incoming inspection by chip manufacturers; contamination monitoring of process equipment and processes; and equipment contamination inspection by semiconductor equipment manufacturers. The sources of different types of contamination vary. Generally, particulate bump defects mainly originate from the environment within the semiconductor equipment cavity, pit defects mainly originate from epitaxy and crystal pulling processes, and scratch defects originate from errors in the polishing process. In defect detection, obtaining information on the type of defect helps users in different fields efficiently pinpoint the source of defects, effectively reducing the number of repeated inspections required.

[0005] However, for the detection systems in related technologies, since defects such as concavity and convexity are unknown before detection, they cannot accurately detect convex and concave defects, resulting in the omission of certain defects and thus low accuracy in defect identification. Summary of the Invention

[0006] To address the aforementioned issues, this application provides a detection system and method to improve the identification range of the detection channel and increase the accuracy of defect identification.

[0007] Based on this, the following technical solution is disclosed in this application:

[0008] In a first aspect, this application proposes a detection system, which includes a carrying platform, an illumination component, and multiple detection channels located on the same detection surface. Each detection channel is equipped with at least one detector, and the multiple detection channels include a first detection channel, a second detection channel, a third detection channel, and a fourth detection channel.

[0009] The platform is used to carry the object to be tested, and the target normal of the object to be tested passes perpendicularly through the platform.

[0010] The illumination component is configured to emit a detection beam toward the object under test, the detection beam being scattered by the object under test to form at least one signal beam;

[0011] The multiple detection channels are respectively configured to collect the signal light emitted from the corresponding detection area in an imaging manner, and generate defect detection information of the object under test based on the signal light;

[0012] The first and second detection channels each have an obtuse angle with the target normal, while the third and fourth detection channels each have an acute angle with the target normal. The first and second detection channels are symmetrically distributed about the target normal, as are the third and fourth detection channels. The incident surface is perpendicular to the detection surface, which is the plane formed by the optical axis of the detection beam and the target normal.

[0013] Optionally, the detection range is the range of signal light intensity that the detection channel can recognize. The first detection range of the first detection channel is different from the second detection range of the second detection channel, and the third detection range of the third detection channel is different from the fourth detection range of the fourth detection channel.

[0014] Optionally, the first detection channel is configured with a first polarization device and / or a first attenuation device;

[0015] The second detection channel is equipped with a second polarization device and / or a second attenuation device;

[0016] The third detection channel is equipped with a third polarization device and / or a third attenuation device;

[0017] The fourth detection channel is equipped with a fourth polarization device and / or a fourth attenuation device;

[0018] The polarization parameters of the first polarization device and the second polarization device are different, and the attenuation parameters of the first attenuation device and the second attenuation device are different.

[0019] The third polarization device has different polarization parameters than the fourth polarization device, and the third attenuation device has different attenuation parameters than the fourth attenuation device.

[0020] Optionally, the illumination component is used to emit a detection beam towards the object under test to form a spot; or,

[0021] The illumination component is used to emit a detection beam to the object under test to form a line spot.

[0022] Optionally, if the illumination component is used to emit a detection beam to the object under test to form a line spot, then the detection surface is perpendicular to the long side of the line spot. Optionally, the illumination component includes a first illumination component and a second illumination component, wherein the first illumination component is configured to emit a first detection beam to the object under test along the target normal, and the second illumination component is configured to emit a second detection beam to the object under test at an oblique angle to the platform.

[0023] Secondly, this application proposes a detection method applied to the detection system described in the first aspect above, the method comprising:

[0024] Send a detection beam to the object under test;

[0025] Acquire the first signal light collected by the first detection channel, the second signal light collected by the second detection channel, the third signal light collected by the third detection channel, and the fourth signal light collected by the fourth detection channel;

[0026] Defect detection information of the object under test is generated based on the first signal light, the second signal light, the third signal light, and the fourth signal light.

[0027] Optionally, generating defect detection information of the object under test based on the first signal light, the second signal light, the third signal light, and the fourth signal light includes:

[0028] Based on the first signal light, the second signal light, the third signal light, and the fourth signal light, the signal strength ratio of the narrow channel to the wide channel is determined. The narrow channel includes the third detection channel and the fourth detection channel, and the wide channel includes the first detection channel and the second detection channel.

[0029] If the signal strength ratio is greater than the signal strength ratio threshold, defect detection information is generated to indicate that the target defect is a pit-type defect;

[0030] If the signal intensity ratio is less than the signal intensity ratio threshold, defect detection information is generated to indicate that the target defect is a protrusion-type defect. Optionally, determining the signal intensity ratio of the narrow channel to the wide channel based on the first signal light, the second signal light, the third signal light, and the fourth signal light includes:

[0031] The signal strength ratio between the narrow channel and the wide channel is determined based on the ratio of the narrow channel signal strength to the wide channel signal strength and a compensation parameter. The narrow channel signal strength is the sum of the signal strengths of the third signal light and the fourth signal light, and the wide channel signal strength is the sum of the signal strengths of the first signal light and the second signal light. The compensation parameter is used to compensate for the signal strength ratio.

[0032] Optionally, the ratio of the narrow channel signal strength to the wide channel signal strength, determined based on the ratio of the narrow channel signal strength to the wide channel signal strength and a compensation parameter, is expressed by the following formula:

[0033] ;

[0034] in, The ratio of the narrow channel signal strength to the wide channel signal strength is given. The signal intensity of the third signal light. The signal intensity of the fourth signal light. The signal intensity of the first signal light. The signal intensity of the second signal light. The compensation parameter is...

[0035] Optionally, the compensation parameter and the signal strength ratio threshold are determined in the following manner:

[0036] Obtain a first set and a second set, wherein the first set includes multiple initial compensation parameters and the second set includes multiple initial signal strength ratio thresholds;

[0037] Based on the target combination, the defect prediction values ​​of multiple test samples are determined, wherein the target combination includes an initial compensation parameter and an initial signal intensity ratio threshold.

[0038] Based on the predicted defect values ​​of the multiple test samples and the actual defect values ​​of the multiple test samples, the defect prediction accuracy of the target combination is determined.

[0039] Each combination determined by the first set and the second set is taken as the target combination, and the defect prediction accuracy of each combination is determined.

[0040] The initial compensation parameter and the initial signal strength ratio threshold in the optimal combination are respectively determined as the compensation parameter and the signal strength ratio threshold, and the optimal combination is the combination with the highest defect prediction accuracy.

[0041] Optionally, the method further includes:

[0042] Obtain the first calibration curve of the first detection channel, the second calibration curve of the second detection channel, the third calibration curve of the third detection channel, and the fourth calibration curve of the fourth detection channel;

[0043] The step of generating defect detection information for the object under test based on the first signal light, the second signal light, the third signal light, and the fourth signal light includes:

[0044] Based on the defect size indicated by the first calibration curve for the first signal light, the defect size indicated by the second calibration curve for the second signal light, the defect size indicated by the third calibration curve for the third signal light, and the defect size indicated by the fourth calibration curve for the fourth signal light, defect detection information for indicating the size of the target defect is generated.

[0045] Optionally, generating defect detection information of the object under test based on the first signal light, the second signal light, the third signal light, and the fourth signal light includes:

[0046] Determine the wide-channel signal intensity ratio based on the first signal light and the second signal light;

[0047] The narrow channel signal intensity ratio is determined based on the third signal light and the fourth signal light;

[0048] Based on the wide-channel signal strength ratio and the narrow-channel signal strength ratio, defect detection information is generated to indicate whether the target defect is a symmetrical defect. If the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is less than a first difference threshold, the target defect is a symmetrical defect. If the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect.

[0049] Optionally, generating defect detection information indicating whether the target defect is a symmetrical defect based on the wide-channel signal strength ratio and the narrow-channel signal strength ratio includes:

[0050] Determine the average of the wide channel signal strength ratio and the narrow channel signal strength ratio;

[0051] Based on the difference between the mean and 1, defect detection information is generated to indicate whether the target defect is a symmetrical defect. Specifically, if the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is less than a first difference threshold, the target defect is a symmetrical defect; if the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect. Alternatively, the maximum value of the wide-channel signal strength ratio and the narrow-channel signal strength ratio is determined.

[0052] Based on the difference between the maximum value and 1, defect detection information is generated to indicate whether the target defect is a symmetrical defect. If the difference between the wide channel signal strength ratio and the narrow channel signal strength ratio and 1 is less than a first difference threshold, the target defect is a symmetrical defect. If the difference between the wide channel signal strength ratio and the narrow channel signal strength ratio and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect.

[0053] As can be seen from the above technical solutions, this application has at least the following beneficial effects:

[0054] The detection system includes a platform, an illumination assembly, and multiple detection channels located on the same detection surface. Each detection channel is equipped with at least one detector. The detection channels include a first detection channel, a second detection channel, a third detection channel, and a fourth detection channel. The platform carries the object to be tested, and the target normal of the object passes perpendicularly through the platform. The illumination assembly is configured to emit a detection beam towards the object, which is scattered by the object to form at least one signal beam. The multiple detection channels are configured to collect the signal beam emitted from their respective detection areas in an imaging manner and generate defect detection information of the object based on the signal beam. The first and second detection channels have obtuse angles with the target normal, while the third and fourth detection channels have acute angles with the target normal. The first and second detection channels are symmetrically distributed about the target normal, as are the third and fourth detection channels. The incident surface is perpendicular to the detection surface, which is the plane formed by the optical axis of the detection beam and the target normal.

[0055] Therefore, by setting four coplanar detection channels in both acute and obtuse angle ranges, and symmetrically arranging them about the target normal, with the incident surface of the illumination component perpendicular to the detection surface, the signal light scattered by the defect exhibits good comparability and directional consistency between the symmetrical channels, providing a stable and reliable geometric basis for determining defect type and symmetry. Specifically, symmetrically arranged wide channels (such as the first and second detection channels) and narrow channels (such as the third and fourth detection channels) are located on both sides of the target normal, used to sense the signal light intensity in large and small angle directions. Combining the signal light intensity ratio at different angles, the defect type can be accurately determined as a pit or a protrusion. Furthermore, based on the signal strength relationship between similar channels (such as two wide channels or two narrow channels), the asymmetry of spatial scattering of the defect can be identified, thereby determining whether the defect is symmetrical. In addition, setting detection channels in both wide and narrow channels, i.e., collecting signal light at different angles, can further identify asymmetrical defects. Through the structural synergy and correlation of the aforementioned detection channels, the detection system not only has the ability to distinguish the types of defects, but also can finely differentiate the structural features and spatial distribution patterns of defects, thereby significantly improving the accuracy of defect identification and classification precision, avoiding missed or false detections of certain types of defects, and enhancing the accuracy of the detection system. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 A schematic diagram of an existing detection system provided in an embodiment of this application;

[0058] Figure 2 A schematic diagram of a multi-channel detection system provided in an embodiment of this application;

[0059] Figure 3 This is a schematic diagram of the structure of a detection system provided in an embodiment of this application;

[0060] Figure 4 This is a schematic diagram illustrating the detection of asymmetric defects according to an embodiment of this application;

[0061] Figure 5 This is a schematic diagram of a defect scattering field distribution provided in an embodiment of this application;

[0062] Figure 6A schematic diagram of the signal light angle of a symmetrical type defect provided in an embodiment of this application;

[0063] Figure 7 A schematic diagram of the signal light angle of an asymmetric type defect provided in an embodiment of this application;

[0064] Figure 8 This is a schematic diagram of signal light intensity curves for different defect sizes provided in the embodiments of this application;

[0065] Figure 9 A top view schematic diagram of a lighting detection system provided in an embodiment of this application;

[0066] Figure 10 This application provides a schematic diagram of a structure in which the incident surface and the detection surface are perpendicular.

[0067] Figure 11 This is a schematic diagram of the structure of the lighting assembly provided in the embodiments of this application;

[0068] Figure 12 A schematic flowchart of a detection method provided in an embodiment of this application;

[0069] Figure 13 This application provides a schematic diagram of the signal light intensity distribution of an uneven defect in a vertical collection channel.

[0070] Figure 14 This application provides a schematic diagram of the signal light intensity distribution of a symmetrical concave-convex defect.

[0071] Figure 15 This application provides a schematic diagram of the signal light intensity distribution of an asymmetric concave-convex defect.

[0072] Figure 16 A scatter plot of experimental measurement results of a wafer surface defect provided in an embodiment of this application;

[0073] Figure 17 This is a schematic diagram of a calibration curve provided for an embodiment of this application. Detailed Implementation

[0074] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While some embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this application. It should be understood that the drawings and embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0075] The detection system in the relevant technology will be described in detail below.

[0076] See Figure 1 The figure is a schematic diagram of an existing detection system provided in an embodiment of this application. Taking wafer detection as an example, related technologies typically employ a single-channel or multi-channel approach.

[0077] The single-channel method mainly uses a large NA microscopic imaging lens and sets the lens optical axis to be perpendicular to the wafer surface. This method can collect defect scattered light within a wider range of emission angles. However, the design, processing, and assembly of the objective lens are extremely difficult, and the collection of noise light generated by the roughness of the wafer substrate also increases accordingly. At the same time, scattered light from different angles is collected by the detector during imaging, making it difficult to obtain information on the angular distribution of scattered light, which makes it impossible to accurately detect protrusion-type defects and depression-type defects.

[0078] Based on this, a multi-channel approach is used, deploying multiple small NA lenses at different spatial solid angles. These multiple small NA lenses jointly collect signal light to obtain defect information. This approach is less complex to develop than traditional NA lenses. However, since multiple channels are probing the same target, at least one lens's optical axis is not perpendicular to the wafer surface. Figure 1 The image shows one of the non-vertical channels among multiple detection channels.

[0079] In multi-channel detection systems, two detection channels are typically set up (e.g., Figure 2 The wide channel W (set with one detection channel 2) and the narrow channel N (set with one detection channel 1) shown are used to collect the scattered signal light from the defects, thereby improving defect identification capabilities. To enhance detection sensitivity, these detection channels often employ detectors with small pixel sizes to reduce system noise levels and enhance response to weak scattered signals. However, defects on the surface of the object under test may not be perfectly spherical or pitted, resulting in scattered light that is not completely symmetrical with respect to the incident surface. In practice, some types of defects may be difficult to identify, leading to a high false negative rate and low accuracy and sensitivity for identifying certain defect types. For example, some protruding defects exhibit uneven scattering intensity on their left and right sides, causing the side with weaker scattering intensity to collect weaker scattered light and thus fail to detect it.

[0080] Based on this, this application provides a detection system and method. By setting four coplanar detection channels in both acute and obtuse angle ranges, and symmetrically arranging them about the target normal, and with the incident surface of the illumination component perpendicular to the detection surface, the signal light scattered by the defect exhibits good comparability and directional consistency between the symmetrical channels, providing a stable and reliable geometric basis for determining defect type and symmetry. Specifically, the symmetrically arranged wide channels (such as the first and second detection channels) and narrow channels (such as the third and fourth detection channels) are located on both sides of the target normal, used to sense the signal light intensity in large and small angle directions. Combining the signal light intensity ratio at different angles, the defect type can be accurately determined as a pit or a protrusion. Furthermore, based on the signal strength relationship between similar channels (such as two wide channels or two narrow channels), the asymmetry of spatial scattering of the defect can be identified, and the symmetry of the defect can be determined accordingly. In addition, by setting detection channels in both wide and narrow channels, i.e., collecting signal light at different angles, asymmetric defects can be further identified. Through the structural synergy and correlation of the aforementioned detection channels, the detection system not only has the ability to distinguish the types of defects, but also can finely differentiate the structural features and spatial distribution patterns of defects, thereby significantly improving the accuracy of defect identification and classification precision, avoiding missed or false detections of certain types of defects, and enhancing the accuracy of the detection system.

[0081] See Figure 3 The figure is a schematic diagram of the structure of a detection system provided in an embodiment of this application.

[0082] The detection system includes a platform (not shown in the figure), an illumination assembly, and multiple detection channels located on the same detection surface. These channels include a first detection channel (e.g., detection channel A), a second detection channel (e.g., detection channel B), a third detection channel (e.g., detection channel C), and a fourth detection channel (e.g., detection channel D). The detection system proposed in this application will be described below using an example of a system including a first detection channel, a second detection channel, a third detection channel, and a fourth detection channel.

[0083] The platform is used to carry the object to be measured, and the target normal of the object to be measured passes perpendicularly through the platform.

[0084] The illumination component is configured to emit a detection beam toward the object under test, and the detection beam is scattered by the object under test to form at least one signal beam. For example, the illumination component could be... Figure 3 Illumination A or Illumination B, where Illumination A emits detection beam 101 and Illumination B emits detection beam 102.

[0085] The lighting components include a light source, a polarization adjustment module, and a beam shaping module.

[0086] The light source mentioned in this application may include any suitable light source, such as a laser, a continuous wave (CW) laser, or a pulsed laser. Furthermore, the light source may be configured to produce light of any suitable wavelength (e.g., about 355 nm, about 266 nm, or about 193 nm).

[0087] The polarization adjustment module is used to adjust the polarization state of the light beam emitted by the light source. Specifically, the light beam emitted by the light source passes through the polarization conversion module to adjust its polarization state. For example, it can be adjusted to linearly polarized light, circularly polarized light, elliptically polarized light, left-handedly polarized light, right-handedly polarized light, etc., and can be set according to actual needs. As an example, the polarization conversion module can be an optical element such as a polarizer or a half-wave plate.

[0088] The beam shaping module can be a collimating flat-top shaping element, or it can be a freeform surface shaping element. The freeform surface shaping element can provide single-degree-of-freedom linewidth compression along the narrow side direction. The shaping module can be implemented using diffractive optical elements (DOEs), microlens arrays, prisms, etc. It can also include one-dimensional beam expanders, collimating flat-top shaping elements, freeform surface shapers, or any other suitable shaping module known in the art. As an example, the shaping module can shape a circular detection spot into a linear detection spot.

[0089] Multiple detection channels are configured to collect signal light emitted from the corresponding detection area in an imaging manner, and generate defect detection information of the test object based on the signal light. Each detection channel is equipped with at least one detector. For example, the detector can be detector 107 of detection channel A, detector 109 of detection channel B, detector 111 of detection channel C, and detector 113 of detection channel D.

[0090] As one possible implementation, the detection channel may include an objective lens and a detector. The detector is located on the light-emitting side of the objective lens. The detector may be, for example, a discrete photomultiplier tube (PMT), a charge-coupled device (CCD), a time-delay integration (TDI), a complementary metal-oxide-semiconductor (CMOS) sensor, a PMT array, an electron-bombarded CCD (EB-CCD), an electron-multiplying CCD (EM-CCD), an enhancement-mode photodiode, or an avalanche photodiode (APD) array. The objective lens collects the scattered light generated by the detection spot in the detection area, and the detector determines the signal intensity of the scattered light to determine the defect information in the detection area based on the signal intensity. Each detection channel may be equipped with one or more detectors, and the detection surface (i.e., the photosensitive surface) of the detector is parallel to the detection light. Preferably, a line detector may be selected.

[0091] This application will subsequently be subject to Figure 3 Taking the detection system as an example, specifically, the detection beam 101 emitted by illumination A coincides with the target normal, that is, the detection beam 101 emitted by illumination A also passes perpendicularly through the platform. Detection channel A is the first detection channel, detection channel B is the second detection channel, detection channel C is the third detection channel, and detection channel D is the fourth detection channel.

[0092] The first and second detection channels have obtuse angles with the target normal, while the third and fourth detection channels have acute angles with the target normal. The first and second detection channels are located on opposite sides of the target normal, as are the third and fourth detection channels.

[0093] In one possible implementation, the illumination assembly includes a first illumination assembly and a second illumination assembly. The first illumination assembly is configured to emit a first detection beam toward the object under test along the target normal, and the second illumination assembly is configured to emit a second detection beam toward the object under test at an angle relative to the platform. Figure 3 As shown, the first lighting component can be lighting A, and the second lighting component can be lighting B.

[0094] Therefore, through the above settings, the detection system can achieve the coordinated use of both vertical and oblique incident illumination methods, thereby enriching the scattering excitation conditions of the test object and improving the full coverage capability of defect detection. Specifically, the first illumination component emits a detection beam along the target normal direction, which can form a symmetrical vertical illumination field on the surface of the test object. This is suitable for exciting targets with obvious forward scattering, such as surface microparticles and shallow concave defects. This incident direction has high incident uniformity and can form a regular and strong scattering signal, which is beneficial to the signal extraction and imaging stability of subsequent detection channels.

[0095] The second illumination component emits a second detection beam at an oblique angle, causing the detection beam to be incident on the surface of the object under test at a certain angle. This beam forms oblique scattering with the structural edges or uneven interfaces of the object under test, which helps to excite asymmetric signals from defects with large surface contour changes or more significant lateral scattering (such as pit edges, protruding particle sidewalls, etc.). This incident direction significantly expands the distribution range of the signal light scattering direction, improving the detection system's response capability to different types of defects.

[0096] See Figure 4 The figure is a schematic diagram of an asymmetric defect detection method proposed in an embodiment of this application, as shown below. Figure 4 (a) Shows the results of scanning electron microscopy review (SEMReview) of some real defects. It can be seen that most defects are not perfectly spherical protrusions or pits, resulting in a non-symmetrical distribution of scattered light after deep ultraviolet laser irradiation of these imperfect defects. Figure 4 Taking the simplified modeling method shown in (b) as an example, the detection beam 102 is obliquely incident on the surface of the cuboid defect. The length, width, and height of the defect are 200 nm, 50 nm, and 50 nm, respectively. The long side of the defect makes a 45-degree angle with the illumination plane, introducing asymmetry. The far-field scattering intensity distribution of the defect is calculated by finite-difference time-domain method, as shown in the figure. Figure 4 (c) shows the asymmetric scattering field distribution results. It can be seen that the scattering field has obvious asymmetry with respect to the illumination plane. For example, the signal light intensity in the 90-degree direction is significantly stronger than that in the 270-degree direction. In reality, the signal light intensity in the 270-degree direction is also stronger than that in the 90-degree direction.

[0097] Furthermore, taking the four defect types as examples, see [link to relevant documentation]. Figure 5 This figure is a schematic diagram of a defect scattering field distribution provided in an embodiment of this application. Figure 5 (a) illustrates the scattering field distribution of a convex-type symmetric defect. Figure 5 (b) illustrates the scattering field distribution of convex asymmetric defects. Figure 5 (c) illustrates the scattering field distribution of pit-like symmetrical defects. Figure 5(d) illustrates the scattering field distribution of pit-type asymmetric defects, where the color represents the intensity of the signal light, with redder colors indicating higher intensity. The color distribution is used to indicate the directionality of signal light scattering. Figure 6 This diagram illustrates the signal light angle of a symmetrical defect, corresponding to... Figure 5 (a) and Figure 5 (c) type of defect, Figure 7 This diagram illustrates the signal light angle of an asymmetric type defect, corresponding to... Figure 5 (b) and Figure 5 (d) Defect types. The red line indicates the signal light intensity of pit-type defects at different angles, and the blue line indicates the signal light intensity of protrusion-type defects at different angles.

[0098] Depend on Figure 5 , Figure 6 and Figure 7 It can be seen that for symmetrical defects such as protrusions and pits, the signal light intensity is approximately symmetrical about the target normal (e.g., 0 degrees), and the signal light intensity of symmetrical defects such as protrusions is distributed at a larger angle. However, for asymmetrical defects such as protrusions and pits, the signal light intensity is biased towards one side of the target normal, resulting in a distribution where one side is stronger than the other.

[0099] Therefore, detection channels can be arranged in different directions (such as acute and obtuse angle directions) so that the first, second, third, and fourth detection channels can collect signal light of different intensities scattered in different directions. For example, for the direction range where the target normal has an acute angle, two detection channels can be set on both sides of the target normal; for the direction range where the target normal has an obtuse angle, two detection channels can be set on both sides of the target normal. This adapts to the signal light intensity distribution of symmetrical and asymmetrical defects, ensuring that regardless of whether the scattering direction of the defect is to the left or right, there is a detection channel in the main scattering direction. This avoids situations where, for example, only the left detection channel is set up, resulting in the signal light intensity being to the right, thus improving the defect detection rate.

[0100] This allows the four detection channels to cover the signal light distribution areas of the test object in different scattering directions. For example, the detection channel with an obtuse angle is good for collecting signal light scattered at large angles and is suitable for capturing reflection information from the edge of the defect, while the detection channel with an acute angle is better suited for capturing weaker signal light in small angle directions, thus improving the response capability to small defects.

[0101] Furthermore, if the first included angle is the angle between the first detection channel and the target normal, the second included angle is the angle between the second detection channel and the target normal, the third included angle is the angle between the third detection channel and the target normal, and the fourth included angle is the angle between the fourth detection channel and the target normal, then the difference between the first included angle and the second included angle is less than the first difference threshold, and the difference between the third included angle and the fourth included angle is less than the first difference threshold. Under the approximately symmetrical detection channel structure, the difference in signal light intensity received by different detection channels can be used to construct the difference and ratio of signal light intensity, thereby determining the symmetry and concavity / convexity of the defect. This will be explained in detail in the subsequent method embodiments and will not be repeated here.

[0102] The first difference threshold is a preset tolerance parameter used to limit the maximum allowable range of the angle difference between the detection channels located on both sides of the target normal. The first difference threshold can be determined by system design parameters, imaging symmetry requirements or experimental calibration results, and is used to ensure the approximate symmetry between the first and second detection channels, as well as the approximate symmetry between the third and fourth detection channels.

[0103] For example, if the third angle between the third detection channel and the target normal is 35 degrees and the fourth angle between the fourth detection channel and the target normal is 38 degrees, then the difference between the third and fourth angles is 3 degrees. If this difference is lower than the preset first difference threshold (e.g., 5°), then the structural requirement of "approximate symmetry" is considered to be met.

[0104] In one possible implementation, the first and second detection channels are symmetrically distributed about the target normal, and the third and fourth detection channels are also symmetrically distributed about the target normal. By achieving a strictly symmetrical arrangement of the detection channels in the structure, each detection channel can have completely equivalent reception conditions for the scattering direction of the same type of defect. This allows for more precise construction of parameters used to indicate defect detection information, such as the ratio of signal light intensities and the differences in signal light intensities, thereby improving the accuracy of detecting the symmetry and concavity / convexity of defects.

[0105] The detection surface is a plane formed by the optical axes of the detection channels, and the incident surface is a plane formed by at least one detection beam. Multiple detection channels are located on the same detection surface, and the detection surface and the incident surface are approximately perpendicular. Specifically, taking the fifth included angle as the angle between the detection surface and the incident surface, and the sixth included angle as the angle between the optical axis of the detection channel and the long side of the line spot as an example, the difference between the fifth included angle and the vertical angle (90 degrees) is less than the second difference threshold, and the difference between the sixth included angle and the vertical angle is less than the second difference threshold.

[0106] The second difference threshold is a preset tolerance parameter used to limit the maximum allowable range of difference between the fifth and sixth included angles and the vertical angle, respectively. The second difference threshold can be determined based on the measured spot utilization rate to ensure the approximate perpendicularity of the detection surface and the incident surface. This ensures that the geometric path of the signal light scattered by the defect is consistent between each detection channel, reducing the large deviation in signal light intensity collected by the detection channels on both sides of the target detection due to the inconsistency of geometric paths caused by the intersection of the incident surface and the detection surface. This improves the detection accuracy.

[0107] In one possible implementation, the incident surface and the detection surface are perpendicular to each other. By strictly defining the perpendicularity, the geometric path consistency of the signal light collected by the detection channel is further improved, thereby increasing the detection accuracy.

[0108] As can be seen from the above technical solution, by setting four coplanar detection channels in both acute and obtuse angle ranges, and symmetrically arranging them about the target normal, and with the incident surface of the illumination component perpendicular to the detection surface, the signal light scattered by the defect exhibits good comparability and directional consistency between the symmetrical channels, providing a stable and reliable geometric basis for determining the defect type and symmetry. Specifically, the symmetrically arranged wide channels (such as the first and second detection channels) and narrow channels (such as the third and fourth detection channels) are located on both sides of the target normal, used to sense the signal light intensity in large and small angle directions. Combining the signal light intensity ratio at different angles, the defect type can be accurately determined as a pit or a protrusion. Furthermore, based on the signal strength relationship between similar channels (such as two wide channels or two narrow channels), it is also possible to identify whether the spatial scattering of the defect is asymmetrical, and thereby determine whether the defect is a symmetrical defect. In addition, by setting detection channels in both wide and narrow channels, i.e., collecting signal light at different angles, asymmetrical defects can be further identified. Through the structural synergy and correlation of the aforementioned detection channels, the detection system not only has the ability to distinguish the types of defects, but also can finely differentiate the structural features and spatial distribution patterns of defects, thereby significantly improving the accuracy of defect identification and classification precision, avoiding missed or false detections of certain types of defects, and enhancing the accuracy of the detection system.

[0109] In related technologies, small-pixel detectors have relatively low full-well electron capacity, making them prone to saturation when receiving strong signal light, which in turn limits the recognition range of the detection channel. For example, the defect size distribution on a wafer may vary greatly, and defects of different sizes will produce scattered light with significantly different intensities. When the signal light corresponding to a large defect exceeds the detection range of the detection channel itself, full-well overflow or signal truncation may occur, resulting in a significant reduction in the accuracy of wafer defect size recognition. The detection range is the range of signal light intensity that the detection channel can recognize. The detection range can be determined by the lowest light intensity that the detection channel can detect and the number of full-well electrons in the detector. The lowest light intensity that the detection channel can detect can be determined by multiple parameters such as detector shot noise, dark noise, haze noise (background noise), and the signal-to-noise ratio threshold for defect detection.

[0110] Based on this, this application proposes a specific implementation method for extending the detection range of a detection system. Specifically, the first detection range of the first detection channel and the second detection range of the second detection channel are different, and the third detection range of the third detection channel and the fourth detection range of the fourth detection channel are different.

[0111] The following example illustrates one method for expanding the detection range. By constructing a near-field physical scattering model based on the finite-time difference method, the near-field distribution of defect scattering is obtained by solving the three-dimensional Maxwell's equations. Furthermore, a joint simulation of near-field optics and imaging optics is achieved based on Debye integral ray tracing, yielding the scattered light intensity curves of the W channel (a wide channel used to indicate the large direction of the detection channel, such as the first and second detection channels) under different defect sizes.

[0112] See Figure 8 This figure is a schematic diagram of signal light intensity curves under different defect sizes according to an embodiment of this application. If the first detection channel (detection channel A) and the second detection channel (detection channel B) use the same lens and detector, and their polarization and attenuation configurations are identical, the detection ranges of the two detection channels are completely consistent. If the first detection channel can detect defects within the size A1~A2, and the defect scattering intensity ratio of A2 / A1 is M1, then by setting the attenuation factor of the second detection channel to M2, the defect size that the second detection channel can detect can be adjusted to B1~B2. In this way, the detection range of the W channel or N channel (narrow channels, used to indicate small-direction detection channels, such as the third and fourth detection channels) can be extended from A1~A2 to A1~B2, resulting in a significant improvement in detection range.

[0113] As one possible implementation, the first, second, third, and fourth detection ranges are set based on the signal light intensity range corresponding to the defect size of the object under test. For example, the first and second detection ranges may or may not overlap, and the third and fourth detection ranges may or may not overlap. For example, as... Figure 8 As shown, if the test object has very few defects within the size range of A2-B1, the first detection range and the second detection range can be set to have no overlapping parts within the size range of A2-B1.

[0114] As one possible implementation, if the first lower limit and the first upper limit are determined based on the first and second detection ranges, and the second lower limit and the second upper limit are determined based on the third and fourth detection ranges, then the first lower limit can be less than the detection lower threshold, the first upper limit can be greater than the detection upper threshold, the second lower limit can be less than the detection lower threshold, and the second upper limit can be greater than the detection upper threshold. This allows the detection system to cover a wider range and identify more types and sizes of defects.

[0115] In one possible implementation, the four detection channels can each employ independent detection or attenuation configurations to expand the detection range of the W and N channels and improve the detection rate of asymmetric defects. Specifically:

[0116] The first detection channel is equipped with a first polarization device and / or a first attenuation device.

[0117] The second detection channel is equipped with a second polarization device and / or a second attenuation device.

[0118] The third detection channel is equipped with a third polarization device and / or a third attenuation device.

[0119] The fourth detection channel is equipped with a fourth polarization device and / or a fourth attenuation device.

[0120] Among them, the first polarizing device and the second polarizing device have different polarization parameters, and the first attenuator and the second attenuator have different attenuation parameters. The third polarizing device and the fourth polarizing device have different polarization parameters, and the third attenuator and the fourth attenuator have different attenuation parameters.

[0121] For example, a polarization rotation device can be added to the first and second detection channels to allow only specific polarization states to pass through. By fusing information from multiple channels, richer defect feature information can be obtained, improving detection accuracy and classification accuracy.

[0122] Therefore, by configuring polarization devices with different polarization parameters or attenuation devices with different attenuation parameters, the four detection channels can be reasonably allocated between high sensitivity (low signal light intensity) and low sensitivity (high signal light intensity). This is especially suitable for asymmetric defects, as it is better suited to their asymmetric signal light intensity distribution, thus improving the detection rate.

[0123] The embodiments of this application do not specifically limit the form of the light source of the illumination component. For example, the illumination component can be used to emit a detection beam towards the object under test to form a point light spot, or the illumination component can be used to emit a detection beam towards the object under test to form a line light spot. As one possible implementation, the shape of the illumination spot is not limited to a line, but can also be an ellipse, a square, or other shapes.

[0124] As one possible implementation, the line spot can be modulated by a shaping module. This shaping module can be a collimated flat-top shaping element, or a freeform surface shaping element. The freeform surface shaping element can provide single-degree-of-freedom linewidth compression along the narrow side direction. The shaping module can be implemented using diffractive optical elements (DOEs), microlens arrays, prisms, etc. It can also include one-dimensional beam expanders, collimated flat-top shaping elements, freeform surface shapers, or any other suitable shaping module known in the art. As an example, the shaping module can shape a circular detection spot into a linear detection spot.

[0125] Because of their small and circular shape (spot diameter on the order of tens to hundreds of micrometers), point light sources have smaller differences in optical path length between different positions of the spot and the detector's conjugate point, making them less prone to defocusing and resulting in better focusing performance. Using a line light source offers at least three advantages:

[0126] One advantage is that, due to the larger area of ​​the linear laser spot, the laser energy density can be significantly reduced, thus reducing damage to the test object.

[0127] The second advantage is that using a line light source can significantly improve detection efficiency.

[0128] Thirdly, under the same yield model, the longer the line spot length, the lower the wafer scanning speed, which can significantly reduce the scanning speed of the high-precision motion platform and reduce the development difficulty of the high-precision motion platform (a type of carrier platform).

[0129] As mentioned above, the perpendicularity of the incident surface to the detection surface is a prerequisite for the distribution of uneven defects according to the aforementioned pattern. The shape of the light spot incident on the wafer can be a point spot (with a diameter on the order of tens to hundreds of micrometers) or a line spot (the width of the long side can range from 0.5 to 20 mm, and the width of the short side can range from 1 to 100 μm). Point spots are circular, so there is no defocusing problem, while line spots need to be perpendicular to the detection surface to solve the defocusing problem, which will be explained in detail below.

[0130] When an illumination assembly is used to emit a detection beam to form a line spot on the object under test, defocusing may occur, resulting in low spot utilization. See also Figure 9 The figure is a top view of an illumination detection provided in an embodiment of this application. The left side shows the case where the incident surface and the detection surface are not perpendicular. When the incident surface and the detection surface are not perpendicular, the light spot 2 (line light spot) will eventually converge on the object to be measured. At this time, the left and right endpoints A and B of the line light spot are at different distances from the lens. Point A is closer to the lens and point B is farther away. Therefore, the images of the left and right ends of the line light spot on the detector will be out of focus (defocused). Only the center point is in focus, and the light spot utilization rate is extremely low.

[0131] Based on this, this application proposes a method for setting up detection channels. As mentioned above, the four detection channels are located on the same detection surface, which can be set to be perpendicular to the long side of the line spot. This ensures that the optical axis of each detection channel is perpendicular to the long side of the line spot. Figure 9 As shown on the right, if the detection surface is ensured to be perpendicular to the long side of the light spot 1 (line light spot), the distance between each position of the long side of the line light spot and the lens is almost the same, making it less prone to defocusing. The line light spot has a high utilization rate, which can improve the stability and yield of the detection system.

[0132] See Figure 10 The figure is a schematic diagram of a structure in which the incident surface and the detection surface are perpendicular, provided by an embodiment of this application. Taking detection channel 1 and detection channel 2 as examples, the two light source components emit detection beam 101 and detection beam 102 respectively. Detection beam 101 and detection beam 102 form plane A (incident surface). The optical axis of detection channel 1 and the optical axis of detection channel 2 form plane B (detection surface). Plane A is perpendicular to plane B, so that the line spot formed by the incident laser is also perpendicular to plane B. This layout can not only solve the defocusing problem in the case of line scanning multi-channel collection, but also collect light rays with different scattering angles, and realize the distinction between pit and protrusion defects.

[0133] Therefore, by setting the detection surface to be perpendicular to the long side of the line spot, that is, setting the optical axis of each detection channel to be perpendicular to the long side of the line spot, the distance from the two endpoints of the long side of the detection spot to the objective lens is the same, which effectively ensures the consistency of the imaging depth of the entire line spot on the detector. This method can minimize the imaging shift caused by spatial angle differences, so that each position of the line spot can be accurately focused and imaged, further improving the utilization rate of the line spot.

[0134] The photosensitive surface of the detector is used to collect the scattered light from the detection spot. When the length and width of the photosensitive surface are different, in order to achieve clear imaging, the long side of the photosensitive surface can be made perpendicular to the plane of the detection surface, so that the long side of the photosensitive surface is parallel to the detection surface. This allows the scattered light from the detection spot to be fully collected by the photosensitive surface, increasing the amount of scattered light entering the detector and achieving a complete and clear image of the detection spot, thereby improving detection efficiency.

[0135] By setting the short side width of the detection spot to be smaller, even if the objective lens or detector in the detection channel deflects at a small angle along the narrow side, the distance between the endpoint of the narrow side of the detection spot and the object-side focal plane of the objective lens will be smaller due to the smaller short side width. Therefore, even if there is a small angle shift along the narrow side, the resulting distance L deviation will not be too large. In other words, after the shift, the distance between the endpoint of the narrow side of the detection spot and the object-side focal plane of the objective lens will still be small, preventing defocusing. In short, a wider linewidth leads to greater defocusing, while a shorter linewidth reduces the likelihood of defocusing, thus improving focusing accuracy, image quality, and stability.

[0136] As one possible implementation, the illumination component may include a polarization adjustment module for enhancing particle signals and suppressing background noise, specifically:

[0137] (1) Enhance particle signal: Some particles are more sensitive to light with a specific polarization direction. Rotating the polarization direction can enhance the particle's scattering signal and improve detection sensitivity. (That is, increase signal strength and improve SNR).

[0138] (2) Suppressing background noise: Wafer surface roughness and thin film interference will generate background noise. Rotating the polarization direction can suppress background noise in a specific direction and improve the signal-to-noise ratio (i.e., reduce haze intensity and improve SNR).

[0139] by Figure 3 For example, the polarization state of the laser light source is adjusted by the polarization adjustment module 104, and then the circular light spot is shaped and focused into a line light spot 114 by the beam shaping module 105. When the line light spot illuminates the defect on the surface of the object under test 115, it will generate scattered signal light in the surrounding space, which will be collected by each detection channel.

[0140] The following uses the structure of an illumination component as an example to explain the polarization light path and its principle. (See also...) Figure 11 The light source 211 emits signal light to the wafer under test. The beam is first split by the beam splitter 212, and then part of the light enters the first incident component. The polarization controller 215 converts the laser light into different polarization forms, such as linearly polarized light and circularly polarized light. Linearly polarized light can be divided into p-polarized light, s-polarized light, and linearly polarized light at a specific angle. Circularly polarized light can be divided into left-handed and right-handed circularly polarized light. The polarization controller 215 can be an optical system consisting of waveplates or combinations of waveplates, or it can be an optical element formed from a metasurface. After the polarization-modulated beam passes through the beam expander 213 and the reflector 216 changes the beam propagation path, a perpendicularly incident beam L1 (corresponding to...) is formed. Figure 3 Illumination 101). The second incident component includes a reflector 214, a polarization controller 215, a beam expander and shaper 213, and a reflector 217, forming an obliquely incident beam L2 (corresponding to...). Figure 3 Lighting component 102).

[0141] Based on the detection system provided in the above-described embodiments, this application also provides a detection method applied to the above-described detection system. (See attached image.) Figure 12 , Figure 12 This is a flowchart illustrating a detection method provided in an embodiment of this application. The method includes S1201-S1203:

[0142] S1201: Sends a detection beam to the object under test.

[0143] S1202: Acquire the first signal light collected by the first detection channel, the second signal light collected by the second detection channel, the third signal light collected by the third detection channel, and the fourth signal light collected by the fourth detection channel.

[0144] As one possible implementation, the signal light collected by each detection channel can be the signal light intensity, which can be the sum of the signal light intensities collected by one of the detection channels. This signal light intensity can be determined by the following formula:

[0145] ;

[0146] in, The signal light intensity of one of the detection channels The entire pixel area occupied by the defect signal. This represents the signal strength obtained by the detector in this pixel area. This represents the noise intensity generated by the object under test in this pixel area. (The remaining text appears to be incomplete and possibly contains errors. A more accurate translation would require the full context.) It is roughly similar; the signal intensity obtained by the detector at the defect-free location of the object under test can be taken as... Alternatively, the average of multiple signal intensities acquired by detectors at multiple defect-free locations on the object under test can be used to obtain the result. .

[0147] S1203: Generate defect detection information of the object under test based on the first signal light, the second signal light, the third signal light and the fourth signal light.

[0148] Among them, defect detection information is characterization information used to reflect defects in the object under test. For example, defect detection information can be used to indicate whether there are defects on the surface of the object under test, the type of defects, the location of defects, the size of defects, etc.

[0149] This application does not specifically limit how to generate defect detection information of the test object based on the first signal light, the second signal light, the third signal light, and the fourth signal light. The following describes four generation methods as examples.

[0150] Method 1: Determine the symmetry of the test object. See A1-A3 for details.

[0151] A1: Determine the wide channel signal intensity ratio based on the first signal light and the second signal light.

[0152] A wide channel refers to a detection channel in the broad direction, such as the first detection channel and the second detection channel. The wide channel signal strength ratio is the ratio of the signal strength of each detection channel within the wide channel. For example, the wide channel signal strength ratio can be expressed by the formula... It is confirmed that, among which For wide channel signal strength ratio, The signal intensity of the first signal light. The intensity of the second signal light.

[0153] A2: Determine the narrow channel signal intensity ratio based on the third and fourth signal lights.

[0154] Narrow channels are detection channels in a narrow direction, such as the third and fourth detection channels. The narrow channel signal strength ratio (SSTR) is the ratio of the signal strength of each detection channel within the narrow channel. For example, the narrow channel SSTR can be expressed by the formula... It is confirmed that, among which Narrow channel signal strength ratio, The signal intensity of the third signal light. The intensity of the fourth signal light.

[0155] A3: Based on the wide channel signal strength ratio and the narrow channel signal strength ratio, generate defect detection information to indicate whether the target defect is a symmetrical defect.

[0156] The target defect is defined as a defect in the object under test. If the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is less than a first difference threshold, the target defect is a symmetrical defect. If the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect. The first difference threshold is a preset threshold used to determine whether the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is small, and the second difference threshold is a preset threshold used to determine whether the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is large.

[0157] Specifically, let's take two judgment methods as examples.

[0158] Method 1: Calculate the mean.

[0159] Determine the mean values ​​of the wide channel signal strength ratio and the narrow channel signal strength ratio.

[0160] For example, the formula K4=(K2+K3) / 2 can be used, where K4 is the mean, K2 is the narrow channel signal strength ratio, and K3 is the wide channel signal strength ratio.

[0161] Based on the difference between the mean and 1, defect detection information is generated to indicate whether the target defect is a symmetrical defect. If the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is less than a first difference threshold, the target defect is a symmetrical defect. If the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect. That is, the larger |K4-1| is, the stronger the asymmetry of the defect.

[0162] For example, when K4 > 1.05, it is determined to be an asymmetric defect with stronger scattering on the left; when K4 < 0.95, it is determined to be an asymmetric defect with stronger scattering on the right.

[0163] Method 2: Find the maximum value.

[0164] Determine the maximum values ​​for the wide channel signal strength ratio and the narrow channel signal strength ratio.

[0165] For example, the formula K5=max(K2,K3) is used, where K5 is the maximum value, K2 is the narrow channel signal strength ratio, and K3 is the wide channel signal strength ratio.

[0166] Based on the difference between the maximum value and 1, defect detection information is generated to indicate whether the target defect is a symmetrical defect. If the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is less than the first difference threshold, the target defect is a symmetrical defect. If the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is greater than the second difference threshold, the target defect is an asymmetrical defect. That is, the larger |K4-1| is, the stronger the asymmetry of the defect.

[0167] For example, when K4 > 1.05, it is determined to be an asymmetric defect with stronger scattering on the left; when K4 < 0.95, it is determined to be an asymmetric defect with stronger scattering on the right.

[0168] Generation Method Two: Determine the concavity / convexity of the defect.

[0169] See Figure 13 This figure is one of the schematic diagrams illustrating the signal light intensity distribution of a concave-convex defect in a vertical collection channel according to an embodiment of this application. Here, theta represents the angle between the optical axis of the detection channel and the target normal. The blue curve represents the signal light intensity distribution of the convex defect, and the red curve represents the signal light intensity distribution of the concave defect. The dashed line corresponds to a defect size of 41 nm, and the solid line corresponds to a defect size of 31 nm. It can be seen that the signal light from the convex defect is mainly distributed in the detection channel at a large angle, while the signal light from the concave defect is mainly distributed in the detection channel at a small angle. See also... Figure 14 This figure is a schematic diagram of the signal light intensity distribution of a symmetrical concave-convex defect provided in an embodiment of this application. It is based on the setting of a first detection channel (W1), a second detection channel (W2), a third detection channel (N1), and a fourth detection channel (N2), wherein... The signal light intensity corresponding to the central corner of the N1 channel for the protrusion-type defect is... The signal light intensity corresponding to the central corner of the N2 channel for the protrusion-type defect is... The signal light intensity corresponding to the central corner of the W1 channel for the protrusion-type defect is... The signal light intensity corresponding to the central corner of the W2 channel for protrusion-type defects is... The signal light intensity corresponding to the central corner of the N1 channel for pit-like defects. The signal light intensity corresponding to the central corner of the N2 channel for pit-like defects. The signal light intensity corresponding to the central corner of the W1 channel for pit-like defects. This represents the signal light intensity corresponding to the central corner of the W2 channel for pit-like defects. See also... Figure 15 This figure is a schematic diagram of the signal light intensity distribution of an asymmetric concave-convex defect provided in an embodiment of this application, and... Figure 14Similarly, the red curve indicates the signal intensity distribution of pit-type defects, and the blue curve indicates the signal intensity distribution of convex defects. By comparing the signal intensity at the center corner of different detection channels, it can be seen that the signal intensity ratio IN / IW of the N channel and the W channel (not shown in the figure, used to indicate the signal intensity ratio of the N channel and the W channel, where the N channel includes N1 and N2 channels, and the W channel includes W1 and W2 channels) shows different patterns for different defect types (the red curve indicates the signal intensity distribution of pit-type defects, and the blue curve indicates the signal intensity distribution of convex defects): the IN / IW ratio is smaller for convex defects, while it is larger for pit-type defects.

[0170] Based on this, the embodiments of this application propose a specific implementation method for determining the concavity and convexity of defects, as detailed in B1-B3:

[0171] B1: Determine the signal strength ratio between the narrow channel and the wide channel based on the first signal light, the second signal light, the third signal light, and the fourth signal light.

[0172] The narrow channel includes the third and fourth detection channels, while the wide channel includes the first and second detection channels.

[0173] B2: If the signal strength ratio is greater than the signal strength ratio threshold, defect detection information is generated to indicate that the target defect is a pit-type defect.

[0174] The signal strength ratio threshold is a preset threshold used to determine the type of defect.

[0175] For example, when K1 > A, the target defect is determined to be a pit-type defect, where K1 is the signal strength ratio threshold and A is the signal strength ratio threshold.

[0176] B3: If the signal strength ratio is less than the signal strength ratio threshold, defect detection information is generated to indicate that the target defect is a protrusion-type defect.

[0177] For example, when K1 < A, the target defect is determined to be a protrusion-type defect, where K1 is the signal strength ratio threshold and A is the signal strength ratio threshold.

[0178] In addition to theoretical analysis, this application also uses experimental testing to demonstrate the feasibility of using four detection channels to detect defect types. Figure 16A scatter plot depicting the experimental measurement results of a wafer surface defect under four probe channel settings is presented. Each point represents a defect, with the x and y axes representing the intensity values ​​of the corresponding N-channel and W-channel, respectively. It can be observed that the scatter plot is densely distributed in two central regions, the upper left and lower right. The entire coordinate region can be divided into two areas by a straight line where the ratio of the N-channel to W-channel intensity is equal to k, where k is a fixed constant. Protrusion and pit defects are distributed in these two regions, respectively. The accuracy of these defect type classifications was verified during testing using methods such as electron microscopy re-examination. Here, B is a system reference signal offset, a compensation parameter used for linear mapping and classification of signal intensity between probe channels.

[0179] Based on this, this application proposes a specific implementation of the second generation method, as detailed in C1, where C1 is a specific implementation of B1:

[0180] C1: Determine the signal strength ratio between the narrow channel and the wide channel based on the ratio of the narrow channel signal strength to the wide channel signal strength and the compensation parameters.

[0181] In this system, the narrow channel signal intensity is the sum of the signal intensities of the third and fourth signal lights, and the wide channel signal intensity is the sum of the signal intensities of the first and second signal lights. The compensation parameter is used to compensate for the signal intensity ratio. As one possible implementation, the compensation parameter is a constant, representing the energy difference between the wide and narrow channels in the detection system, and can be determined based on the optical settings of the detection system.

[0182] In one possible implementation, C1 can be determined by the following formula:

[0183] ;

[0184] in, The ratio of the narrow channel signal strength to the wide channel signal strength is given. The signal intensity of the third signal light. The signal intensity of the fourth signal light. The signal intensity of the first signal light. The signal intensity of the second signal light. The compensation parameter is...

[0185] Therefore, a compensation parameter is introduced into the signal strength ratio calculation process, serving as a reference offset or energy normalization constant between detection channels. This compensation parameter can be obtained through system calibration or modeling analysis, and is used to linearly map or correct the signal strength, thereby eliminating systematic biases and improving the accuracy of the calculation when calculating the signal strength ratio. Figure 16Taking the scatter plot as an example, after adjusting the compensation parameters, different defect types (such as pits and protrusions) exhibit clearer and more separable cluster distributions in the intensity ratio coordinate system, which is beneficial for setting a unified classification threshold (such as the signal intensity ratio threshold) for identification.

[0186] In one possible implementation, the compensation parameters and the signal strength ratio threshold can be determined as follows, see D1-D5:

[0187] D1: Get the first set and the second set.

[0188] The first set includes multiple initial compensation parameters, and the second set includes multiple initial signal strength ratio thresholds. The initial compensation parameters are compensation parameters to be determined, and the initial signal strength ratio thresholds are signal strength ratio thresholds to be determined.

[0189] D2: Determine the predicted defect values ​​for multiple test samples based on the target combination.

[0190] Selecting an initial signal strength ratio threshold from the second set yields a combination; the first and second sets can determine multiple combinations. The target combination is one of these combinations, and it includes an initial compensation parameter and an initial signal strength ratio threshold. The initial compensation parameter is selected from the first set.

[0191] Taking a target combination as an example, by applying the target combination, at least one test sample with pit-type defects of different sizes and at least one test sample with protrusion-type defects of different sizes are measured in the detection system to obtain defect prediction values ​​for multiple test samples. The defect prediction value is the defect type of the test sample predicted based on the target combination.

[0192] D3: Determine the defect prediction accuracy of the target combination based on the predicted defect values ​​of multiple test samples and the actual defect values ​​of multiple test samples.

[0193] The correct value can be the one that matches the actual defect value, and the defect prediction accuracy of the target combination can be statistically analyzed.

[0194] D4: Take each combination determined by the first set and the second set as the target combination and determine the defect prediction accuracy of each combination.

[0195] The defect prediction accuracy of each combination determined by the first and second sets is determined by executing D2-D4 respectively.

[0196] D5: Determine the initial compensation parameter and the initial signal strength ratio threshold in the optimal combination as the compensation parameter and the signal strength ratio threshold, respectively.

[0197] The optimal combination is the one with the highest defect prediction accuracy.

[0198] Therefore, by calibrating and testing each combination consisting of the first set and the second set, the optimal combination is sought from multiple initial compensation parameters and multiple initial signal strength ratio thresholds, thereby obtaining more accurate compensation parameters and signal strength ratio thresholds, and improving the accuracy of concavity and convexity judgment.

[0199] Generation method three: Determine the size of the defect.

[0200] See Figure 13 As shown, the larger the defect size, the greater the signal light intensity. Based on this, this application provides a method for determining the defect size, specifically referring to E1-E2, where E2 is a specific implementation of S1203:

[0201] E1: Obtain the first calibration curve of the first detection channel, the second calibration curve of the second detection channel, the third calibration curve of the third detection channel, and the fourth calibration curve of the fourth detection channel. As one possible implementation, the calibration curves will be different for different types of test objects, different detection channels, and different optical configurations, and need to be calibrated separately.

[0202] See Figure 17 Taking a protruding defect in one N-channel as an example, this is a schematic diagram of the calibration curve provided in the embodiment of this application. It can be seen that the signal light intensity is different for different defect sizes.

[0203] E2: Based on the defect size indicated by the first calibration curve for the first signal light, the defect size indicated by the second calibration curve for the second signal light, the defect size indicated by the third calibration curve for the third signal light, and the defect size indicated by the fourth calibration curve for the fourth signal light, generate defect detection information to indicate the size of the target defect.

[0204] For example, the size of the target defect can be determined by weighted fusion of the defect sizes indicated by four calibration curves to generate defect detection information.

[0205] Therefore, by configuring different calibration curves for different detection channels, it is possible to adapt to actual scenarios with different directions and different response capabilities of detection channels, thereby enhancing the adaptability of the detection system to complex defect types and complex optical configurations.

[0206] Generation Method Four: Determine the location of the defect.

[0207] The test object can rotate at a constant speed on the platform. When a defect (such as a particle) at a certain position of the test object moves to the detection area (such as the line spot 109), the particle is illuminated and emits signal light in all directions, which is captured by each detection channel and finally imaged on the detector. The position of the defect on the test object can be calculated based on the original image stored by the detector and the speed of the moving platform.

[0208] The term "comprising" and its variations as used herein are open-ended inclusions, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the description below.

[0209] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0210] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0211] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0212] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A detection system, characterized in that, The detection system includes a platform, an illumination assembly, and multiple detection channels located on the same detection surface. Each detection channel is equipped with at least one detector. The multiple detection channels include a first detection channel, a second detection channel, a third detection channel, and a fourth detection channel. The platform is used to carry the object to be tested, and the target normal of the object to be tested passes perpendicularly through the platform. The illumination component is configured to emit a detection beam toward the object under test, the detection beam being scattered by the object under test to form at least one signal beam; The multiple detection channels are respectively configured to collect the signal light emitted from the corresponding detection area in an imaging manner, and generate defect detection information of the object under test based on the signal light; Wherein, the first detection channel and the second detection channel have an obtuse angle, the third detection channel and the fourth detection channel have an acute angle, the first detection channel and the second detection channel are symmetrically distributed about the target normal, the third detection channel and the fourth detection channel are symmetrically distributed about the target normal, the incident surface is perpendicular to the detection surface, and the incident surface is the plane formed by the optical axis of the detection beam and the target normal; The detection system is used to acquire the first signal light collected by the first detection channel, the second signal light collected by the second detection channel, the third signal light collected by the third detection channel, and the fourth signal light collected by the fourth detection channel; The detection system is used to determine the signal intensity ratio of the narrow channel to the wide channel based on the ratio of the narrow channel signal intensity to the wide channel signal intensity and a compensation parameter. The sum of the signal intensities of the third signal light and the fourth signal light forms the narrow channel signal intensity, and the sum of the signal intensities of the first signal light and the second signal light forms the wide channel signal intensity. The compensation parameter is used to compensate for the signal intensity ratio. The detection system generates defect detection information based on the signal strength ratio: If the signal strength ratio is greater than the signal strength ratio threshold, defect detection information is generated to indicate that the target defect is a pit-type defect; If the signal strength ratio is less than the signal strength ratio threshold, defect detection information is generated to indicate that the target defect is a protrusion-type defect.

2. The detection system according to claim 1, characterized in that, The detection range is the range of signal light intensity that the detection channel can recognize. The first detection range of the first detection channel is different from the second detection range of the second detection channel, and the third detection range of the third detection channel is different from the fourth detection range of the fourth detection channel.

3. The detection system according to claim 2, characterized in that, The first detection channel is equipped with a first polarization device and / or a first attenuation device; The second detection channel is equipped with a second polarization device and / or a second attenuation device; The third detection channel is equipped with a third polarization device and / or a third attenuation device; The fourth detection channel is equipped with a fourth polarization device and / or a fourth attenuation device; The polarization parameters of the first polarization device and the second polarization device are different, and the attenuation parameters of the first attenuation device and the second attenuation device are different. The third polarization device has different polarization parameters than the fourth polarization device, and the third attenuation device has different attenuation parameters than the fourth attenuation device.

4. The detection system according to claim 1, characterized in that, The illumination component is used to emit a detection beam towards the object under test to form a spot of light; or... The illumination component is used to emit a detection beam to the object under test to form a line spot.

5. The detection system according to claim 4, characterized in that, If the illumination component is used to emit a detection beam to the object under test to form a line spot, then the detection surface is perpendicular to the long side of the line spot.

6. The detection system according to claim 1, characterized in that, The illumination assembly includes a first illumination assembly and a second illumination assembly. The first illumination assembly is configured to emit a first detection beam toward the object under test along the target normal, and the second illumination assembly is configured to emit a second detection beam toward the object under test at an oblique angle to the platform.

7. A detection method, characterized in that, The method, using the detection system as described in claims 1-6, comprises: Send a detection beam to the object under test; Acquire the first signal light collected by the first detection channel, the second signal light collected by the second detection channel, the third signal light collected by the third detection channel, and the fourth signal light collected by the fourth detection channel; Based on the first signal light, the second signal light, the third signal light, and the fourth signal light, defect detection information of the object under test is generated; The step of generating defect detection information for the object under test based on the first signal light, the second signal light, the third signal light, and the fourth signal light includes: Based on the first signal light, the second signal light, the third signal light, and the fourth signal light, the signal strength ratio of the narrow channel to the wide channel is determined. The narrow channel includes the third detection channel and the fourth detection channel, and the wide channel includes the first detection channel and the second detection channel. If the signal strength ratio is greater than the signal strength ratio threshold, defect detection information is generated to indicate that the target defect is a pit-type defect; If the signal strength ratio is less than the signal strength ratio threshold, defect detection information is generated to indicate that the target defect is a protrusion-type defect; Determining the signal strength ratio of the narrow channel to the wide channel based on the first signal light, the second signal light, the third signal light, and the fourth signal light includes: The signal strength ratio of the narrow channel to the wide channel is determined based on the ratio of the narrow channel signal strength to the wide channel signal strength and the compensation parameter. The narrow channel signal strength is the sum of the signal strengths of the third signal light and the fourth signal light, and the wide channel signal strength is the sum of the signal strengths of the first signal light and the second signal light. The compensation parameter is used to compensate for the signal strength ratio.

8. The method according to claim 7, characterized in that, The ratio of the narrow channel signal strength to the wide channel signal strength, determined based on the ratio of the narrow channel signal strength to the wide channel signal strength and compensation parameters, is expressed by the following formula: ； in, The ratio of the narrow channel signal strength to the wide channel signal strength is given. The signal intensity of the third signal light. The signal intensity of the fourth signal light. The signal intensity of the first signal light. The signal intensity of the second signal light. The compensation parameter is...

9. The method according to claim 7, characterized in that, The compensation parameter and the signal strength ratio threshold are determined in the following manner: Obtain a first set and a second set, wherein the first set includes multiple initial compensation parameters and the second set includes multiple initial signal strength ratio thresholds; Based on the target combination, the defect prediction values ​​of multiple test samples are determined, wherein the target combination includes an initial compensation parameter and an initial signal intensity ratio threshold. Based on the predicted defect values ​​of the multiple test samples and the actual defect values ​​of the multiple test samples, the defect prediction accuracy of the target combination is determined. Each combination determined by the first set and the second set is taken as the target combination, and the defect prediction accuracy of each combination is determined. The initial compensation parameter and the initial signal strength ratio threshold in the optimal combination are respectively determined as the compensation parameter and the signal strength ratio threshold, and the optimal combination is the combination with the highest defect prediction accuracy.

10. The method according to claim 7, characterized in that, The method further includes: Obtain the first calibration curve of the first detection channel, the second calibration curve of the second detection channel, the third calibration curve of the third detection channel, and the fourth calibration curve of the fourth detection channel; The step of generating defect detection information for the object under test based on the first signal light, the second signal light, the third signal light, and the fourth signal light includes: Based on the defect size indicated by the first calibration curve for the first signal light, the defect size indicated by the second calibration curve for the second signal light, the defect size indicated by the third calibration curve for the third signal light, and the defect size indicated by the fourth calibration curve for the fourth signal light, defect detection information for indicating the size of the target defect is generated.

11. The method according to claim 7, characterized in that, The step of generating defect detection information for the object under test based on the first signal light, the second signal light, the third signal light, and the fourth signal light includes: Determine the wide-channel signal intensity ratio based on the first signal light and the second signal light; The narrow channel signal intensity ratio is determined based on the third signal light and the fourth signal light; Based on the wide-channel signal strength ratio and the narrow-channel signal strength ratio, defect detection information is generated to indicate whether the target defect is a symmetrical defect. If the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is less than a first difference threshold, the target defect is a symmetrical defect. If the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect.

12. The method according to claim 11, characterized in that, The step of generating defect detection information to indicate whether a target defect is a symmetrical defect based on the wide-channel signal strength ratio and the narrow-channel signal strength ratio includes: Determine the average of the wide channel signal strength ratio and the narrow channel signal strength ratio; Based on the difference between the mean and 1, defect detection information is generated to indicate whether the target defect is a symmetrical defect. Specifically, if the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is less than a first difference threshold, the target defect is a symmetrical defect; if the difference between the wide-channel signal strength ratio and the narrow-channel signal strength ratio and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect. Alternatively, the maximum value of the wide-channel signal strength ratio and the narrow-channel signal strength ratio is determined. Based on the difference between the maximum value and 1, defect detection information is generated to indicate whether the target defect is a symmetrical defect. If the difference between the wide channel signal strength ratio and the narrow channel signal strength ratio and 1 is less than a first difference threshold, the target defect is a symmetrical defect. If the difference between the wide channel signal strength ratio and the narrow channel signal strength ratio and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect.

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