Detection system and detection method

Abstract

The invention discloses a detection system and a detection method, the detection system comprises a carrying platform, a lighting assembly and a plurality of detection channels, each detection channel is provided with at least one detector, and the plurality of detection channels comprise a first detection channel, a second detection channel, a third detection channel and a fourth detection channel. The object carrying platform is used for carrying an object to be measured. The illumination assembly is configured to emit a detection light beam to a to-be-detected object, and the detection light beam is scattered by the to-be-detected object to form at least one beam of signal light. The plurality of detection channels are respectively configured to collect the signal light emitted by the corresponding detection areas in an imaging manner, and generate defect detection information of the object to be detected according to the signal light. The four coplanar detection channels are located on the two sides of the target normal respectively to form symmetrical distribution, and the incident plane is perpendicular to the detection plane, so that the distribution rule of scattered light intensity of different types of defects is better met, the detection system has a better signal light collection effect aiming at the different types of defects, and the detection precision and sensitivity are improved.

Description

Technical Field

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

[0002] Currently, scattered light imaging-based inspection systems are commonly used to identify surface defects in objects under test. For example, if a wafer has defects such as grooves, particles, and scratches, it can cause the chips made from it to fail. Therefore, wafer surface defect detection is necessary before use.

[0003] In the related art, multiple detection channels are usually used to detect the same object to be tested, so as to obtain defect information of the object to be tested at different angles.

[0004] Taking semiconductor chips as an example, any contaminants (such as foreign matter or particles generated during the production process) or defects (such as scratches and dents) on a semiconductor chip whose physical dimensions are close to or larger than the feature size of the final product are harmful and must be strictly monitored throughout the entire manufacturing process. Therefore, surface defect detection for unpatterned wafers has important applications in many areas of the semiconductor industry, including: product quality inspection by wafer manufacturers; incoming goods inspection by chip manufacturers, contamination monitoring of process equipment and process steps; and equipment contamination status inspection by semiconductor equipment manufacturers. Different types of contamination have different sources. Generally speaking, particle-type protrusion defects mainly originate from the environment within the semiconductor equipment chamber, pit-type defects mainly originate from the epitaxial growth and crystal pulling processes, and scratch-type defects originate from errors in the polishing process. In defect detection, obtaining information on defect type can help users in different fields effectively identify the source of defects and effectively reduce the number of repeated inspections required.

[0005] However, for the detection system in the related art, since defects such as convexity and concaveness are unknown before detection, it is impossible to accurately detect convex defects and concave defects. There is a possibility that certain defects will be missed, resulting in low accuracy in defect identification. Summary of the Invention

[0006] In response to the above problems, the present application provides a detection system and a detection method for improving the recognition range of the detection channel and improving the accuracy of defect recognition.

[0007] Based on this, this application discloses the following technical solutions: In a first aspect, the present application provides a detection system, comprising a loading platform, an illumination assembly, and a plurality of detection channels, wherein the plurality of detection channels are located on the same detection surface, each of the detection channels is configured with at least one detector, and the plurality of detection channels include a first detection channel, a second detection channel, a third detection channel, and a fourth detection channel; The loading platform is used to carry the object to be tested, and the target normal line of the object to be tested vertically passes through the loading platform; The lighting assembly is configured to emit a detection light beam toward the object to be measured, wherein the detection light beam is scattered by the object to be measured to form at least one beam of signal light; The plurality of 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 to be detected based on the signal light; Among them, the first detection channel and the second detection channel respectively have obtuse angles with the target normal, the third detection channel and the fourth detection channel respectively have acute angles with the target normal, 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 a plane formed by the optical axis of the detection light beam and the target normal.

[0008] Optionally, the detection range is the signal light intensity range that the detection channel can identify, 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.

[0009] Optionally, the first detection channel is configured with a first polarization device and / or a first attenuation device; The second detection channel is configured with a second polarization device and / or a second attenuation device; The third detection channel is configured with a third polarization device and / or a third attenuation device; The fourth detection channel is configured with a fourth polarization device and / or a fourth attenuation device; Wherein, 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 and the fourth polarization device have different polarization parameters, and the third attenuation device and the fourth attenuation device have different attenuation parameters.

[0010] Optionally, the lighting assembly is used to emit a detection light beam to the object to be tested to form a point light spot; or, The lighting assembly is used to emit a detection light beam to the object to be tested to form a line light spot.

[0011] Optionally, if the lighting assembly is used to emit a detection beam toward the object to be tested to form a linear light spot, the detection surface is perpendicular to the long side of the linear light spot. Optionally, the lighting assembly includes a first lighting assembly and a second lighting assembly, the first lighting assembly being configured to emit a first detection beam toward the object to be tested along the target normal, and the second lighting assembly being configured to emit a second detection beam toward the object to be tested at an oblique angle relative to the loading platform.

[0012] In a second aspect, the present application proposes a detection method, which is applied to the detection system as described in the first aspect above, and the method comprises: sending a detection light beam to the object to be detected; Acquire a first signal light collected by the first detection channel, a second signal light collected by the second detection channel, a third signal light collected by the third detection channel, and a fourth signal light collected by the fourth detection channel; Defect detection information of the object to be tested is generated according to the first signal light, the second signal light, the third signal light, and the fourth signal light.

[0013] Optionally, generating defect detection information of the object to be tested according to the first signal light, the second signal light, the third signal light, and the fourth signal light includes: determining a signal intensity ratio of a narrow channel to a wide channel based on the first signal light, the second signal light, the third signal light, and the fourth signal light, wherein 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 a signal strength ratio threshold, generating defect detection information indicating that the target defect is a pit-type defect; If the signal intensity ratio is less than the signal intensity ratio threshold, defect detection information indicating that the target defect is a protrusion defect is generated. 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: The signal intensity ratio of the narrow channel to the wide channel is determined based on a ratio of the narrow channel signal intensity to the wide channel signal intensity and a compensation parameter, where the narrow channel signal intensity is the sum of the signal intensities of the third signal light and the fourth signal light, and the wide channel signal intensity is the sum of the signal intensities of the first signal light and the second signal light. The compensation parameter is used to compensate for the signal intensity ratio.

[0014] Optionally, 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 a compensation parameter, which is expressed by the following formula: ; in, is the ratio of the narrow channel signal strength to the wide channel signal strength, is the signal light intensity of the third signal light, is the signal light intensity of the fourth signal light, is the signal light intensity of the first signal light, is the signal light intensity of the second signal light, is the compensation parameter.

[0015] Optionally, the compensation parameter and the signal strength ratio threshold are determined in the following manner: Acquire a first set and a second set, wherein the first set includes a plurality of initial compensation parameters, and the second set includes a plurality of initial signal strength ratio thresholds; Determining defect prediction values ​​of a plurality of DUT samples according to a target combination, wherein the target combination includes an initial compensation parameter and an initial signal intensity ratio threshold; Determining a defect prediction accuracy rate of the target combination according to the defect prediction values ​​of the plurality of test object samples and the actual defect values ​​of the plurality of test object samples; Taking each combination determined by the first set and the second set as the target combination, and determining the defect prediction accuracy of each combination; 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.

[0016] Optionally, the method further includes: Obtaining a first calibration curve for the first detection channel, a second calibration curve for the second detection channel, a third calibration curve for the third detection channel, and a fourth calibration curve for the fourth detection channel; Generating defect detection information of the object to be tested according to the first signal light, the second signal light, the third signal light, and the fourth signal light includes: Defect detection information indicating the size of a target defect is generated 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.

[0017] Optionally, generating defect detection information of the object to be tested according to the first signal light, the second signal light, the third signal light, and the fourth signal light includes: determining a wide channel signal intensity ratio according to the first signal light and the second signal light; determining a narrow channel signal intensity ratio according to the third signal light and the fourth signal light; Defect detection information is generated based on the wide-channel signal intensity ratio and the narrow-channel signal intensity ratio to indicate whether the target defect is a symmetrical defect. If the difference between the wide-channel signal intensity ratio and the narrow-channel signal intensity 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 intensity ratio and the narrow-channel signal intensity and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect.

[0018] Optionally, generating defect detection information indicating whether a target defect is a symmetric defect according to the wide channel signal intensity ratio and the narrow channel signal intensity ratio includes: Determining a mean of the wide channel signal strength ratio and the narrow channel signal strength ratio; Generating defect detection information indicating whether the target defect is a symmetrical defect based on the difference between the mean and 1, wherein if the difference between the wide channel signal intensity ratio and the narrow channel signal intensity ratio and 1 is less than a first difference threshold, the target defect is a symmetrical defect; and if the difference between the wide channel signal intensity ratio and the narrow channel signal intensity and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect; or determining a maximum value of the wide channel signal intensity ratio and the narrow channel signal intensity ratio; 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, wherein if the difference between the wide channel signal intensity ratio and the narrow channel signal intensity 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 intensity ratio and the narrow channel signal intensity and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect.

[0019] It can be seen from the above technical solutions that this application has at least the following beneficial effects: The detection system includes a loading platform, an illumination component, and multiple detection channels. The multiple detection channels are 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 loading platform is used to carry the object to be tested, and the target normal of the object to be tested passes perpendicularly through the loading platform. The illumination component is configured to emit a detection beam to the object to be tested, and the detection beam is scattered by the object to be tested to form at least one signal light. 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 to be tested based on the signal light. Among them, the first detection channel and the second detection channel respectively have an obtuse angle with the target normal, the third detection channel and the fourth detection channel respectively have an acute angle with the target normal, 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.

[0020] Therefore, by setting up four coplanar detection channels in the acute and obtuse angle ranges, arranged symmetrically about the target normal, and with the incident surface of the illumination assembly perpendicular to the detection surface, the signal light scattered by the defect is highly comparable and directionally consistent 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 either side of the target normal, respectively, to sense the signal light intensity at high and low angles. The ratio of signal light intensities at different angles can be used to accurately determine whether the defect type is a pit or a bump. Furthermore, based on the signal strength relationship between similar channels (such as two wide channels or two narrow channels), it is possible to identify whether the spatial scattering of the defect is asymmetric and, therefore, determine whether the defect is symmetrical. Furthermore, by setting up separate detection channels in the wide and narrow channels, that is, collecting signal light at different angles, it is possible to further identify asymmetric defects. Through the structural collaborative association of the above-mentioned detection channels, the detection system not only has the ability to distinguish the types of defects, but can also finely distinguish the structural characteristics and spatial distribution patterns of defects, thereby significantly improving the accuracy of defect identification and classification accuracy, avoiding missed detection and false detection of some types of defects, and enhancing the accuracy of the detection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A schematic diagram of an existing detection system provided in an embodiment of the present application; Figure 2 A schematic diagram of a multi-channel detection system provided in an embodiment of the present application; Figure 3 A schematic diagram of the structure of a detection system provided in an embodiment of the present application; Figure 4 A schematic diagram of detecting an asymmetric defect proposed in an embodiment of the present application; Figure 5 A schematic diagram of defect scattering field distribution provided in an embodiment of the present application; Figure 6 A schematic diagram of the signal light angle of a symmetrical type defect provided in an embodiment of the present application; Figure 7 A schematic diagram of the signal light angle of an asymmetric defect provided in an embodiment of the present application; Figure 8 A schematic diagram of a signal light intensity curve for different defect sizes provided in an embodiment of the present application; Figure 9 A schematic top view of an illumination detection system provided in an embodiment of the present application; Figure 10 A schematic diagram of a structure in which the incident surface and the detection surface are perpendicular to each other provided in an embodiment of the present application; Figure 11 A schematic diagram of the structure of the lighting assembly provided in an embodiment of the present application; Figure 12 A schematic diagram of a detection method provided in an embodiment of the present application; Figure 13 A schematic diagram of the signal light intensity distribution of a concave-convex defect in a vertical collection channel provided in an embodiment of the present application; Figure 14 A schematic diagram of the signal light intensity distribution of a symmetrical concave-convex defect provided in an embodiment of the present application; Figure 15 A schematic diagram of the signal light intensity distribution of an asymmetric concave-convex defect provided in an embodiment of the present application; Figure 16 A scatter plot of experimental measurement results of wafer surface defects provided in an embodiment of the present application; Figure 17 A schematic diagram of a calibration curve provided in an embodiment of the present application. DETAILED DESCRIPTION

[0023] The following describes embodiments of the present application in more detail with reference to the accompanying drawings. Although certain embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be construed as limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present application. It should be understood that the drawings and embodiments of the present application are for illustrative purposes only and are not intended to limit the scope of protection of the present application.

[0024] The following is a detailed introduction to the detection system in the related art.

[0025] See also Figure 1 , this figure is a schematic diagram of an existing detection system provided in an embodiment of the present application. Taking wafer detection as an example, a single-channel method or a multi-channel method is usually adopted in related technologies.

[0026] The single-channel method mainly uses a large NA microscope imaging lens and sets the lens optical axis perpendicular to the wafer surface. This method can collect defect scattered light within a larger output angle range, but the design, processing, and assembly of the objective lens are extremely difficult, and the noise light generated by the roughness of the wafer substrate is also increased accordingly. At the same time, scattered light at different angles is collected by the detector during imaging collection, and it is difficult to obtain the scattered light angle distribution information, resulting in the inability to accurately detect protrusion defects and depression defects.

[0027] Based on this, a multi-channel approach deploys multiple small-NA lenses at different spatial angles. These lenses collectively collect signal light to obtain defect information. This approach is less challenging to develop than larger-NA lenses. Because multiple channels detect the same target, the optical axis of at least one lens is not perpendicular to the wafer surface. Figure 1 A non-vertical channel among multiple detection channels is shown in FIG.

[0028] In a multi-channel detection system, two detection channels are usually set up (for example Figure 2 The wide channel W shown is equipped with a detection channel 2, and the narrow channel N is equipped with a detection channel 1) to respectively collect the signal light scattered by the defect to improve defect recognition capabilities. To improve detection sensitivity, these detection channels often use detectors with small pixel sizes to reduce the system noise level and enhance the response to weak scattered signals. However, the defects on the surface of the object to be tested may not be perfectly spherical or pit-shaped, resulting in their scattered light not being completely symmetrical relative to the incident surface. In practice, some types of defects may be difficult to identify, with a high missed detection rate, and low recognition accuracy and sensitivity for some defect types. For example, some raised defects have different scattering intensities on the left and right sides, resulting in the scattered light collected on the side with weaker scattering intensity being weaker and undetectable.

[0029] Based on this, the present application provides a detection system and method. By setting up four coplanar detection channels in the acute and obtuse angle ranges, arranged symmetrically about the target normal, and with the incident surface and detection surface of the illumination assembly perpendicular to each other, the system ensures that the signal light scattered by the defect is highly comparable and directionally consistent across 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 either side of the target normal, respectively, to sense the signal light intensity at high and low angles. The ratio of signal light intensities at different angles can be used to accurately determine whether the defect type is a pit or a bump. Furthermore, based on the signal strength relationship between similar channels (such as two wide channels or two narrow channels), it is possible to identify whether the spatial scattering of the defect is asymmetric and, therefore, determine whether the defect is symmetrical. Furthermore, by setting up separate detection channels in the wide and narrow channels, i.e., collecting signal light at different angles, it is possible to further identify asymmetric defects. Through the structural collaborative association of the above-mentioned detection channels, the detection system not only has the ability to distinguish the types of defects, but can also finely distinguish the structural characteristics and spatial distribution patterns of defects, thereby significantly improving the accuracy of defect identification and classification accuracy, avoiding missed detection and false detection of some types of defects, and enhancing the accuracy of the detection system.

[0030] See also Figure 3 , which is a structural diagram of a detection system provided in an embodiment of the present application.

[0031] The detection system includes a loading platform (not shown), an illumination assembly, and multiple detection channels. The multiple detection channels are located on the same detection surface and 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 the embodiments of the present application is described below using the example of a detection system including the first detection channel, the second detection channel, the third detection channel, and the fourth detection channel.

[0032] The loading platform is used to carry the object to be measured, and the target normal line of the object to be measured vertically passes through the loading platform.

[0033] The lighting assembly is configured to emit a detection beam toward the object to be tested, and the detection beam is scattered by the object to be tested to form at least one signal light. For example, the lighting assembly can be Figure 3 The lighting A or lighting B in the embodiment, lighting A emits a detection light beam 101 and lighting B emits a detection light beam 102.

[0034] The lighting assembly includes a light source, a polarization adjustment module, and a beam shaping module.

[0035] The light source mentioned herein 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 generate light of any suitable wavelength (e.g., approximately 355 nm, approximately 266 nm, or approximately 193 nm).

[0036] 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 the polarization state. For example, the polarization state can be adjusted to linear polarization, circular polarization, elliptically polarized light, left-handed polarization, right-handed polarization, etc., and can be set based on actual needs. As an example, the polarization conversion module can be an optical element such as a polarizer or half-wave plate.

[0037] The beam shaping module can be a collimated flat-top shaping element or a free-form surface shaping element. The free-form surface shaping element can provide single-degree-of-freedom linewidth compression along the narrow edge direction. The shaping module can be implemented using diffractive optical elements (DOEs), microlens arrays, prisms, etc. The shaping module can also include a one-dimensional beam expander, a collimated flat-top shaping element, a free-form surface shaper, 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.

[0038] Multiple detection channels are respectively configured to collect signal light emitted from the corresponding detection area in an imaging manner and generate defect detection information of the object to be tested based on the signal light. Each detection channel is configured 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.

[0039] As a 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. Examples of the detector include a discrete photomultiplier tube (PMT), a charge-coupled device (CCD), a time delay integrator (TDI), a complementary metal oxide semiconductor (CMOS) sensor, a PMT array, an electron bombardment CCD (EB-CCD), an electron-multiplying CCD (EM-CCD), an enhanced photodiode, or an avalanche photodiode (APD) array. The objective lens is used to collect scattered light generated by the detection light spot in the detection area, and the detector is used to determine the signal intensity of the scattered light so as to determine defect information in the detection area based on the signal intensity. Each detection channel can 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, the detector can be a line detector.

[0040] This application will be followed by Figure 3 Taking the detection system as an example, specifically, the detection light beam 101 emitted by lighting A coincides with the target normal, that is, the detection light beam 101 emitted by lighting A also passes vertically through the object loading platform, and 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.

[0041] Among them, the first detection channel and the second detection channel have obtuse angles with the target normal respectively, the third detection channel and the fourth detection channel have acute angles with the target normal respectively, the first detection channel and the second detection channel are located on both sides of the target normal, and the third detection channel and the fourth detection channel are located on both sides of the target normal.

[0042] In one possible implementation, the lighting assembly includes a first lighting assembly and a second lighting assembly, wherein the first lighting assembly is configured to emit a first detection beam toward the object to be tested along a target normal line, and the second lighting assembly is configured to emit a second detection beam toward the object to be tested along an oblique angle relative to the object loading platform. Figure 3 As shown, the first lighting assembly can be lighting A and the second lighting assembly can be lighting B.

[0043] Therefore, through the above-mentioned settings, the detection system can achieve the coordinated use of vertical and oblique incidence illumination modes, thereby enriching the scattering excitation conditions of the object under test and improving the full coverage capability of defect detection. Specifically, the first lighting component emits the detection beam along the target normal direction, which can form a symmetrical vertical illumination field on the surface of the object under test. This is suitable for exciting targets with significant forward scattering, such as small surface particles and shallow concave defects. This incidence direction has high incidence uniformity and can form a regular and strong scattering signal, which is beneficial for signal extraction and imaging stability in subsequent detection channels.

[0044] The second lighting component emits a second detection beam at an oblique angle, so that the detection beam is incident on the surface of the object to be tested at a certain inclination angle, forming oblique scattering at the structural edges or concave-convex interfaces of the object to be tested, which helps to stimulate asymmetric signals of defects with large surface contour changes or more significant side scattering (such as pit edges, raised particle sidewalls, etc.). This incident direction significantly expands the distribution range of the signal light scattering direction, thereby improving the detection system's response capability to different types of defects.

[0045] See also Figure 4 , which is a schematic diagram of detecting an asymmetric defect proposed in an embodiment of the present application, such as Figure 4 (a) shows the results of the Scanning Electron Microscope Review (SEMReview) of some real defects. It can be seen that most defects are not perfect spherical protrusions or pits, resulting in asymmetrical distribution of scattered light after deep ultraviolet laser irradiation on these imperfect defects. Figure 4 Taking the simplified modeling method shown in (b) as an example, the detection beam 102 is incident obliquely on the surface of a rectangular defect. The length, width and height of the defect are 200nm, 50nm and 50nm respectively. The angle between the long side of the defect and the illumination plane is 45 degrees, which introduces asymmetry. The far-field scattering intensity distribution of the defect is calculated by time-domain finite difference, and the result is as follows: Figure 4 (c) The asymmetric scattered field distribution results show that the scattered field has obvious asymmetry relative to the illumination plane. For example, the signal light intensity at 90 degrees is significantly stronger than that at 270 degrees. In actual situations, the signal light intensity at 270 degrees is also stronger than that at 90 degrees.

[0046] Further, taking four defect types as an example, see Figure 5 , which is a schematic diagram of defect scattering field distribution provided by an embodiment of the present application, Figure 5 (a) Schematic diagram of the scattered field distribution of the convex symmetrical defect. Figure 5 (b) shows the scattered field distribution of the convex asymmetric defect. Figure 5 (c) shows the scattered field distribution of pit-like symmetrical defects. Figure 5(d) Schematic diagram of the scattering field distribution of a pit-type asymmetric defect, where the color represents the signal light intensity, and the redder the better. The color distribution is used to indicate the directionality of the signal light scattering. Figure 6 A schematic diagram of the signal light angle of a symmetrical type defect is shown, corresponding to Figure 5 (a) and Figure 5 (c) the type of defect, Figure 7 A schematic diagram of the signal light angle of an asymmetric defect is shown, corresponding to Figure 5 (b) and Figure 5 (d) Defect type. The red lines indicate the signal intensity of pit defects at different angles, and the blue lines indicate the signal intensity of bump defects at different angles.

[0047] Depend on Figure 5 、 Figure 6 and Figure 7 It can be seen that for symmetrical defects such as protrusions and symmetrical defects such as pits, the signal light intensity is approximately symmetrical about the target normal (such as 0 degrees), and the signal light intensity of symmetrical defects such as protrusions is distributed at a larger angle. However, for asymmetric defects such as protrusions and symmetrical defects such as pits, the signal light intensity tends to one side of the target normal, resulting in a distribution that is strong on one side and weak on the other.

[0048] Therefore, detection channels can be arranged in different directions (such as acute angle directions and obtuse angle directions) respectively, so that the first detection channel, the second detection channel, the third detection channel and the fourth detection channel can collect scattered signal light of different intensities in different directions. For example, for the direction range in which the target normal has an acute angle, two detection channels are set on both sides of the target normal respectively. For example, for the direction range in which the target normal has an obtuse angle, two detection channels are set on both sides of the target normal to adapt to the signal light intensity distribution of symmetrical defects and asymmetric defects, ensuring that no matter whether the scattering direction of the defect is to the left or to the right, there is a detection channel in the main scattering direction, avoiding the situation where, for example, only the detection channel on the left is arranged and the signal light intensity is biased to the right, thereby improving the defect detection rate.

[0049] In this way, the four detection channels can respectively cover the signal light distribution areas of the object to be tested in different scattering directions. For example, the detection channel with an obtuse angle is conducive to collecting signal light scattered at a large angle, and is suitable for capturing the reflection information of the defect edge, while the detection channel with an acute angle is more suitable for capturing weaker signal light in a small angle direction, thereby improving the response capability to tiny defects.

[0050] In addition, if the first angle is the angle between the first detection channel and the target normal, the second angle is the angle between the second detection channel and the target normal, the third angle is the angle between the third detection channel and the target normal, and the fourth angle is the angle between the fourth detection channel and the target normal, then the difference between the first angle and the second angle is less than the first difference threshold, and the difference between the third angle and the fourth 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, etc., so as to judge the symmetry and concave-convexity of the defect. This will be explained in detail in the method embodiments later and will not be repeated here.

[0051] 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 detection channel and the second detection channel, and the approximate symmetry between the third detection channel and the fourth detection channel.

[0052] For example, when 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, the difference between the third angle and the fourth angle is 3 degrees. If the difference is lower than the preset first difference threshold (for example, 5°), it is considered that the "approximately symmetrical" structural requirement is met.

[0053] In one possible implementation, the first and second detection channels are symmetrically arranged about the target normal, and the third and fourth detection channels are symmetrically arranged about the target normal. This strictly symmetrical arrangement of the detection channels ensures that each detection channel has completely equivalent reception conditions for the same type of defect scattering direction. This allows for more precise construction of parameters used to indicate defect detection information, such as signal light intensity ratios and differences, thereby improving the accuracy of defect symmetry and concavity detection.

[0054] The detection surface is the plane formed by the optical axes of the detection channels, and the incident surface is the 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 to each other. Specifically, taking the fifth angle as the angle between the detection surface and the incident surface, and the sixth angle as the angle between the optical axes of the detection channels and the long side of the linear light spot as an example, the difference between the fifth angle and the vertical angle (90 degrees) is less than the second difference threshold, and the difference between the sixth angle and the vertical angle is less than the second difference threshold.

[0055] The second difference threshold is a preset tolerance parameter used to limit the maximum allowable range of the difference between the fifth angle and the sixth angle 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, so that the geometric path of the signal light scattered by the defect is consistent between each detection channel, reducing the situation where the signal light intensity collected by the detection channels on both sides of the target is greatly deviated due to inconsistent geometric paths due to the oblique intersection of the incident surface and the detection surface, thereby improving detection accuracy.

[0056] In a possible implementation, the incident surface and the detection surface are perpendicular to each other. By strictly limiting the perpendicularity, the geometric path consistency of the signal light collected by the detection channel is further improved, thereby improving the detection accuracy.

[0057] The above technical solution demonstrates that by providing four coplanar detection channels in both the acute and obtuse angle ranges, arranged symmetrically about the target normal, and with the illumination assembly's incident surface and detection surface positioned perpendicularly, the signal light scattered by the defect is highly comparable and directionally consistent across 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 either side of the target normal, sensing signal light intensity at high and low angles. The ratio of signal light intensities at different angles allows accurate determination of defect type as either a pit or a bump. Furthermore, based on the signal strength relationship between similar channels (such as two wide channels or two narrow channels), it is possible to identify whether the defect's spatial scattering is asymmetric and, therefore, determine whether the defect is symmetrical. Furthermore, by providing separate detection channels in the wide and narrow channels, i.e., collecting signal light at different angles, it is possible to further identify asymmetric defects. Through the structural collaborative association of the above-mentioned detection channels, the detection system not only has the ability to distinguish the types of defects, but can also finely distinguish the structural characteristics and spatial distribution patterns of defects, thereby significantly improving the accuracy of defect identification and classification accuracy, avoiding missed detection and false detection of some types of defects, and enhancing the accuracy of the detection system.

[0058] In related technologies, the full-well electron capacity of small-pixel detectors is relatively low, making them prone to saturation when receiving strong signal light, which in turn limits the detection channel's recognition range. For example, the defect size distribution on a wafer may span a wide range, 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, significantly reducing the accuracy of wafer defect size recognition. The detection range is the range of signal light intensities that the detection channel can recognize. The detection range is determined by the minimum light intensity that the detection channel can detect and the number of full-well electrons in the detector. The minimum light intensity that the detection channel can detect can be determined by multiple parameters such as the detector shot noise, dark noise, haze noise (background noise), and the signal-to-noise ratio threshold for defect detection.

[0059] Based on this, an embodiment of the present application proposes a specific implementation method for expanding the detection range of the detection system. Specifically, 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.

[0060] The following example illustrates one method for expanding the detection range. By constructing a near-field physical scattering model based on the finite-difference time-domain method, the three-dimensional Maxwell equations are solved to obtain the near-field distribution of defect scattering. Ray tracing based on the Debye integral is then used to implement a joint simulation of near-field optics and imaging optics. This results in scattered light intensity curves for different defect sizes in the W channel (a wide channel used to indicate the general direction of detection, such as the first and second detection channels).

[0061] See also Figure 8 , this figure is a schematic diagram of the signal light intensity curve under different defect sizes proposed in an embodiment of the present application. Among them, if the first detection channel (detection channel A) and the second detection channel (detection channel B) use the same lens and detector, and the polarization configuration and attenuation configuration are exactly the same, the detection ranges of the two detection channels are exactly the same. If the first detection channel can detect defects within the size of A1~A2, and the defect scattering intensity ratio of A2 / A1 is M1 times, then the defect size that can be detected by the second detection channel can be adjusted to B1~B2 by setting the attenuation multiple of the second detection channel to M2 times. In the above manner, the detection range of the W channel or N channel (narrow channel, used to indicate a small direction detection channel, such as the third detection channel and the fourth detection channel) can be expanded from A1~A2 to A1~B2, and the detection range is significantly improved.

[0062] As a possible implementation, the first detection range, the second detection range, the third detection range, and the fourth detection range are set based on the signal light intensity range corresponding to the defect size of the object to be detected. For example, the first detection range and the second detection range may have overlapping parts or no overlapping parts, and the third detection range and the fourth detection range may have overlapping parts or no overlapping parts. For example, Figure 8 As shown, if the object to be tested 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 part within the size range of A2-B1.

[0063] As a 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 lower detection threshold, the first upper limit can be greater than the upper detection threshold, the second lower limit can be less than the lower detection threshold, and the second upper limit can be greater than the upper detection threshold. This allows the detection system to cover a wider detection range and identify defects of more types and sizes.

[0064] In one possible implementation, the four detection channels can each adopt an independent detection configuration or an attenuation configuration to expand the detection range of the W channel and the N channel and improve the detection rate of asymmetric defects. Specifically: The first detection channel is configured with a first polarization device and / or a first attenuation device.

[0065] The second detection channel is configured with a second polarization device and / or a second attenuation device.

[0066] The third detection channel is configured with a third polarization device and / or a third attenuation device.

[0067] The fourth detection channel is configured with a fourth polarization device and / or a fourth attenuation device.

[0068] The first polarizer and the second polarizer have different polarization parameters, the first attenuator and the second attenuator have different attenuation parameters, the third polarizer and the fourth polarizer have different polarization parameters, and the third attenuator and the fourth attenuator have different attenuation parameters.

[0069] For example, polarization rotation devices can be added to the first detection channel and the second detection channel to allow only specific polarization states to pass through, and more abundant defect feature information can be obtained through multi-channel information fusion to improve detection accuracy and classification accuracy.

[0070] Therefore, by configuring polarization devices with different polarization parameters or attenuation devices with different attenuation parameters, the four detection channels can be reasonably allocated at high sensitivity (low signal light intensity) and low sensitivity (high signal light intensity). This is especially true for asymmetric defects, as it is more adapted to the asymmetric distribution of signal light intensity and improves the detection rate.

[0071] The embodiments of the present application do not specifically limit the light source form of the illumination assembly. For example, the illumination assembly may be configured to emit a detection beam toward the object to be tested to form a point light spot, or the illumination assembly may be configured to emit a detection beam toward the object to be tested to form a line light spot. As a possible implementation, the shape of the illumination light spot is not limited to a line and may also be other shapes such as an ellipse or a square.

[0072] As a possible implementation, the line spot can be modulated by a shaping module. The shaping module can be a collimated flat-top shaping element, or a free-form surface shaping element. The free-form 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. The shaping module can also include a one-dimensional beam expander, a collimated flat-top shaping element, a free-form surface shaper, 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.

[0073] Because the spot shape of the point light is small and circular (the spot diameter is on the order of tens to hundreds of microns), the optical path difference between the different positions of the spot and the conjugate point of the detector is small, which makes defocus less likely and improves the focusing effect. Using a line light source has at least the following three advantages: Advantage 1: Due to the larger linear spot area, the laser energy density can be significantly reduced, thus reducing damage to the object to be measured.

[0074] The second advantage is that the use of linear light source can significantly improve detection efficiency.

[0075] Advantage three: Under the same productivity mode, 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 difficulty of developing the high-precision motion platform (a type of loading platform).

[0076] As can be seen from the foregoing, the perpendicularity between the incident surface and the detection surface is a prerequisite for the regular distribution of concave and convex defects described above. The incident light spot on the wafer can be a point spot (with a diameter ranging from tens to hundreds of microns) or a line spot (with a long side width ranging from 0.5 to 20 mm and a short side width ranging from 1 to 100 μm). A point spot is circular, so there is no defocus issue. However, a line spot must be perpendicular to the detection surface to solve this problem. This is explained in detail below.

[0077] When the lighting assembly is used to emit a detection beam to the object to be tested to form a line spot, defocusing may occur, resulting in low spot utilization. Figure 9 This figure is a top-down schematic diagram of an illumination detection provided by an embodiment of the present 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, they will eventually converge into a light spot 2 (line light spot) 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 lengths from the lens. Point A is close to the lens, and point B is far away. Therefore, the images of the left and right ends of the line light spot on the detection detector will be out of focus (defocused), and only the center point is in focus, and the light spot utilization rate is extremely low.

[0078] Based on this, the embodiment of the present application proposes a setting method for detection channels. As mentioned above, the four detection channels are located on the same detection surface, and the detection surface can be set to be perpendicular to the long side of the line spot. In this way, 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 spot 1 (line spot), the distance between each position of the long side of the line spot and the lens is almost consistent, it is not easy to defocus, the line spot utilization rate is high, and the stability and productivity of the detection system can be improved.

[0079] See also Figure 10 , this figure is a schematic diagram of a structure in which the incident surface and the detection surface are perpendicular to each other provided by an embodiment of the present application. Taking detection channel 1 and detection channel 2 as examples, the two light source components emit detection beams 101 and detection beams 102 respectively. The detection beams 101 and 102 constitute plane A (incident surface), and the optical axes of detection channel 1 and detection channel 2 constitute plane B (detection surface). Plane A is perpendicular to plane B, so that the linear spot formed by the incident laser is also perpendicular to plane B. This layout method can not only solve the defocus problem in the case of line scanning multi-channel collection, but also collect light with different scattering angles to achieve the distinction between pits and protrusions.

[0080] Therefore, by setting the detection surface perpendicular to the long side of the line spot, that is, setting the optical axis of each detection channel perpendicular to the long side of the line spot, the distances from the two end points of the long side of the detection spot to the objective lens are the same, effectively ensuring the consistency of the imaging depth of the entire line spot on the detector. This method can minimize the imaging offset 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.

[0081] The photosensitive surface of the detector is used to collect the scattered light of the detection spot. When the length and width of the photosensitive surface are different, in order to achieve clear imaging, the long side direction of the photosensitive surface can be made perpendicular to the plane of the detection surface, so that the long side direction of the photosensitive surface is parallel to the detection surface. In this way, the scattered light of the detection spot can be fully collected by the photosensitive surface, thereby increasing the amount of scattered light entering the detector, achieving complete and clear imaging of the detection spot, and thus improving detection efficiency.

[0082] By setting the short side width of the detection spot to be smaller, even if the objective lens or detector of the detection channel deflects slightly in the narrow side direction, the smaller short side width will keep the endpoint of the narrow side of the detection spot closer to the object-side focal plane of the objective lens. Consequently, even if a small angle shift occurs in the narrow side direction, the resulting deviation in distance L will not be too large. That is, 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 is also smaller, preventing defocus. In short, the wider the line width, the more defocused it is, and conversely, the shorter the line width, the less likely it is to be defocused, thereby improving focusing accuracy, imaging quality, and stability.

[0083] As a possible implementation, the lighting assembly may include a polarization adjustment module, which is used to enhance the particle signal and suppress background noise. Specifically: (1) Enhanced particle signal: Some particles are more sensitive to light with a specific polarization direction. Rotating the polarization direction can enhance the particle scattering signal and improve detection sensitivity (i.e., increase signal intensity and improve SNR).

[0084] (2) Suppressing background noise: Wafer surface roughness and thin film interference can generate background noise. Rotating the polarization direction can suppress background noise in a specific direction and improve the signal-to-noise ratio (i.e., reducing haze intensity and improving SNR).

[0085] by Figure 3 For example, the laser light source is polarized by the polarization adjustment module 104, and then the circular spot is shaped and converged into a line spot 114 by the beam shaping module 105. When the line spot irradiates the defect on the surface of the object to be measured 115, it generates scattered signal light in the surrounding space and is collected by each detection channel.

[0086] The following uses the structure of a lighting component as an example to explain the polarization light path and its principle. Figure 11 , the light source 211 sends a signal light to the wafer to be tested. The light 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 into different polarization forms such as linear polarization and circular polarization. Among them, linear polarization can be divided into p-polarized light, s-polarized light and specific angle linear polarization. Circular polarization can be divided into left-handed circularly polarized light and right-handed circularly polarized light. The polarization controller 215 can be an optical system composed of a wave plate or a combination of wave plates, or an optical element formed by a metasurface. After the polarization-modulated light beam passes through the beam expander 213 for shaping and the reflector 216 for changing the beam propagation path, a vertical incident light beam L1 (corresponding to Figure 3 The second incident component includes a reflector 214, a polarization controller 215, a beam expander 213 and a reflector 217 to form an oblique incident light beam L2 (corresponding to Figure 3 lighting assembly 102).

[0087] Based on the detection system provided in the above application embodiment, the present application embodiment also provides a detection method, which is applied to the above detection system, see Figure 12 , Figure 12 This is a flow chart of a detection method provided in an embodiment of the present application, the method comprising S1201-S1203: S1201: Sending a detection beam to the object to be tested.

[0088] S1202: Acquire a first signal light collected by the first detection channel, a second signal light collected by the second detection channel, a third signal light collected by the third detection channel, and a fourth signal light collected by the fourth detection channel.

[0089] As a possible implementation, the signal light collected by each detection channel may be a signal light intensity. The signal light intensity may be the sum of the signal light intensities collected by one of the detection channels. The signal light intensity may be determined by the following formula: ; in, is the signal light intensity of one of the detection channels, is the total pixel area occupied by the defect signal, is the signal intensity obtained by the detector in the pixel area, is the noise intensity generated by the object under test in the pixel area. It is roughly similar. The signal strength obtained by the detector at the defect-free position of the object to be tested can be taken as , or the average value of multiple signal intensities obtained by detectors at multiple defect-free locations of the object to be tested can be obtained .

[0090] S1203: Generate defect detection information of the object to be tested according to the first signal light, the second signal light, the third signal light, and the fourth signal light.

[0091] The defect detection information is characterization information used to reflect defects of the object to be tested. For example, the defect detection information can be used to indicate whether there are defects on the surface of the object to be tested, the type of defects, the location of the defects, the size of the defects, etc.

[0092] The embodiment of the present application does not specifically limit how to generate defect detection information of the object to be tested 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.

[0093] Generation method 1: Determine the symmetry of the object under test. See A1-A3 for details.

[0094] A1: Determine a wide channel signal intensity ratio based on the first signal light and the second signal light.

[0095] The wide channel is a detection channel in a large direction, such as the first detection channel and the second detection channel. The wide channel signal intensity ratio is the signal intensity ratio of each detection channel in the wide channel. For example, the wide channel signal intensity ratio can be calculated by the formula Determine that is the wide channel signal intensity ratio, is the signal light intensity of the first signal light, is the signal light intensity of the second signal light.

[0096] A2: Determine a narrow channel signal intensity ratio based on the third signal light and the fourth signal light.

[0097] Narrow channels are detection channels with small directions, such as the third detection channel and the fourth detection channel. The narrow channel signal intensity ratio is the signal intensity ratio of each detection channel in the narrow channel. For example, the narrow channel signal intensity ratio can be obtained by the formula Determine that is the narrow channel signal strength ratio, is the signal light intensity of the third signal light, is the signal light intensity of the fourth signal light.

[0098] A3: Generate defect detection information indicating whether the target defect is a symmetrical defect based on the wide channel signal intensity ratio and the narrow channel signal intensity ratio.

[0099] The target defect is a defect in the object under test. If the difference between the wide channel signal intensity ratio and the narrow channel signal intensity 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 intensity ratio and the narrow channel signal intensity 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 intensity ratio and the narrow channel signal intensity 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 intensity ratio and the narrow channel signal intensity ratio and 1 is large.

[0100] Specifically, take two judgment methods as examples. Judgment method 1: find the mean.

[0101] Determine the mean of the wide channel signal intensity ratio and the narrow channel signal intensity ratio.

[0102] For example, through the formula K4=(K2+K3) / 2, K4 is the mean, K2 is the narrow channel signal strength ratio, and K3 is the wide channel signal strength ratio.

[0103] Based on the difference between the mean and 1, defect detection information is generated to indicate whether the target defect is symmetrical. If the difference between the wide channel signal intensity ratio and the narrow channel signal intensity ratio and 1 is less than a first difference threshold, the target defect is symmetrical. If the difference between the wide channel signal intensity ratio and the narrow channel signal intensity and 1 is greater than a second difference threshold, the target defect is asymmetrical. In other words, the larger the |K4-1|, the more asymmetric the defect.

[0104] For example, when K4>1.05, it is determined to be an asymmetric defect with stronger scattering on the left side; when K4<0.95, it is determined to be an asymmetric defect with stronger scattering on the right side. Judgment method two: find the maximum value.

[0105] The maximum value of the wide channel signal intensity ratio and the narrow channel signal intensity ratio is determined.

[0106] For example, through the formula K5=max(K2, K3), K5 is the maximum value, K2 is the narrow channel signal strength ratio, and K3 is the wide channel signal strength ratio.

[0107] 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 intensity ratio and the narrow channel signal intensity 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 intensity ratio and the narrow channel signal intensity and 1 is greater than the second difference threshold, the target defect is an asymmetrical defect. In other words, the larger the |K4-1|, the more asymmetric the defect.

[0108] For example, when K4>1.05, it is determined to be an asymmetric defect with stronger scattering on the left side; when K4<0.95, it is determined to be an asymmetric defect with stronger scattering on the right side. Generation method 2: determine the concave-convexity of the defect.

[0109] See also Figure 13 This figure is one of the schematic diagrams of the signal light intensity distribution of a concave-convex defect in a vertical collection channel provided by an embodiment of the present application, where theta represents the angle between the optical axis of the detection channel and the target normal. The blue curve is the signal light intensity distribution of a convex defect, and the red curve is the signal light intensity distribution of a pit defect. The dotted line corresponds to a defect size of 41nm, and the solid line corresponds to a defect size of 31nm. It can be seen that the signal light of a convex defect is mainly distributed in the detection channel at a large angle, while the signal light of a pit defect is mainly distributed in the detection channel at a small angle. Figure 14 , This figure is a schematic diagram of the signal light intensity distribution of a symmetrical concave-convex defect provided by an embodiment of the present application, based on setting a first detection channel (W1), a second detection channel (W2), a third detection channel (N1) and a fourth detection channel (N2), wherein, is the signal light intensity corresponding to the central angle of the convex defect in the N1 channel, is the signal light intensity corresponding to the central angle of the convex defect in the N2 channel, is the signal light intensity corresponding to the central angle of the convex defect in the W1 channel, is the signal light intensity corresponding to the central angle of the W2 channel for the convex defect, is the signal light intensity corresponding to the center angle of the pit defect in the N1 channel, is the signal light intensity corresponding to the center angle of the pit defect in the N2 channel, is the signal light intensity corresponding to the center angle of the pit defect in the W1 channel, is the signal light intensity corresponding to the center angle of the pit defect in the W2 channel. Figure 15 , which is a schematic diagram of the signal light intensity distribution of an asymmetric concave-convex defect provided by an embodiment of the present application, and Figure 14 Similarly, the red curve is used to indicate the signal light intensity distribution of the pit type, and the blue curve is used to indicate the signal light intensity distribution of the protrusion type. By comparing the signal light intensities of the central angles 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 to the W channel, the N channel includes the N1 channel and the N2 channel, and the W channel includes the W1 channel and the W2 channel) shows different rules for different defect types (the red curve is used to indicate the signal light intensity distribution of the pit type, and the blue curve is used to indicate the signal light intensity distribution of the protrusion type): the IN / IW of the protrusion type defect is smaller, while the IN / IW of the pit type defect is larger.

[0110] Based on this, the embodiment of the present application proposes a specific implementation method for determining the concave-convex nature of a defect, see B1-B3 for details: B1: Determine a signal intensity ratio between a narrow channel and a wide channel based on the first signal light, the second signal light, the third signal light, and the fourth signal light.

[0111] 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.

[0112] B2: If the signal strength ratio is greater than the signal strength ratio threshold, defect detection information indicating that the target defect is a pit-type defect is generated.

[0113] The signal strength ratio threshold is a preset threshold used to determine the defect type.

[0114] For example, when K1>A, the target defect is determined to be a pit defect, K1 is the signal intensity ratio threshold, and A is the signal intensity ratio threshold.

[0115] B3: If the signal intensity ratio is less than the signal intensity ratio threshold, defect detection information indicating that the target defect is a convex defect is generated.

[0116] For example, when K1<A, the target defect is determined to be a convex defect, K1 is the signal intensity ratio threshold, and A is the signal intensity ratio threshold.

[0117] In addition to theoretical analysis, this application also uses experimental tests to prove the feasibility of using four detection channels to detect defect types. Figure 16 The scatter plot depicts the experimental measurement results of a wafer surface defect under four detection channel settings, where each point represents a defect, and its horizontal and vertical coordinates represent the intensity values ​​of the defect corresponding to the N channel and the W channel, respectively. It can be found that the scatter plot is more densely distributed in the two central areas in the upper left and lower right. The entire coordinate area can be divided into two areas using a straight line with the intensity ratio of the N channel to the W channel equal to k, where k is a fixed constant. The protrusion and pit defects are respectively scattered in these two areas. The correctness of these defect type classifications was also verified by methods such as electron microscopy re-inspection during the test. Among them, B is a system reference signal offset, which is a compensation parameter for linear mapping of signal intensities between detection channels and classification judgment.

[0118] Based on this, the embodiment of the present application proposes a specific implementation of the second generation method, see C1 for details, where C1 is a specific implementation of B1: C1: 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 the compensation parameter.

[0119] The narrow channel signal intensity is the sum of the signal intensities of the third and fourth signal lights, while 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 a possible implementation, the compensation parameter is a constant representing the energy difference between the wide and narrow channels of the detection system. This parameter can be determined based on the optical setup of the detection system.

[0120] In one possible implementation, C1 can be determined by the following formula: ; in, is the ratio of the narrow channel signal strength to the wide channel signal strength, is the signal light intensity of the third signal light, is the signal light intensity of the fourth signal light, is the signal light intensity of the first signal light, is the signal light intensity of the second signal light, is the compensation parameter.

[0121] Therefore, a compensation parameter is introduced into the calculation process of the signal intensity ratio 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 perform linear mapping or correction on the signal intensity, thereby eliminating systematic deviations when calculating the signal intensity ratio and improving the accuracy of the calculation. Figure 16 Taking the scatter plot in as an example, after the compensation parameters are adjusted, different defect types (such as pits and protrusions) show clearer and separable cluster distributions in the intensity ratio coordinate system, which is conducive to setting a unified classification threshold (such as signal intensity ratio threshold) for identification.

[0122] In a possible implementation, the compensation parameter and the signal strength ratio threshold may be determined as follows, see D1-D5: D1: Get the first set and the second set.

[0123] The first set includes multiple initial compensation parameters, 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.

[0124] D2: Determine the defect prediction values ​​of multiple DUT samples based on the target combination.

[0125] An initial signal strength ratio threshold is selected from the second set to obtain a combination. The first set and the second set can determine multiple combinations. The target combination is one of the multiple combinations, and the target combination includes an initial compensation parameter and an initial signal strength ratio threshold. The initial compensation parameter is selected from the first set.

[0126] Taking the target combination as an example, by applying the target combination, at least one DUT sample with pit-type defects of varying sizes and at least one DUT sample with protrusion-type defects of varying sizes are measured in the inspection system to obtain defect prediction values ​​for the multiple DUT samples. The defect prediction value is the defect type of the DUT sample predicted based on the target combination.

[0127] D3: Determine the defect prediction accuracy of the target combination based on the defect prediction values ​​of the multiple test object samples and the actual defect values ​​of the multiple test object samples.

[0128] The defect prediction value that is consistent with the actual defect value can be taken as the correct value to calculate the defect prediction accuracy of the target combination.

[0129] 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.

[0130] That is, D2-D4 are executed on each combination determined by the first set and the second set respectively to determine the defect prediction accuracy of each combination.

[0131] 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.

[0132] Among them, the optimal combination is the combination with the highest defect prediction accuracy.

[0133] Therefore, by calibrating and testing each combination 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, thereby improving the accuracy of concavity and convexity judgment. Generation method three, determine the size of the defect.

[0134] See also Figure 13 As shown, the larger the size of the defect, the greater the signal light intensity. Based on this, the embodiment of the present application provides a method for determining the defect size, see E1-E2 for details, where E2 is a specific implementation of S1203: E1: Obtain a first calibration curve for the first detection channel, a second calibration curve for the second detection channel, a third calibration curve for the third detection channel, and a fourth calibration curve for the fourth detection channel. As a possible implementation, different calibration curves may be required for different types of DUTs, different detection channels, and different optical configurations, and therefore require separate calibration.

[0135] See also Figure 17 Taking the raised defect of the N channel on one side as an example, this is a schematic diagram of the calibration curve provided in the embodiment of the present application. It can be seen that the signal light intensity corresponding to different defect sizes is different.

[0136] E2: Generate defect detection information indicating the size of the target defect 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.

[0137] For example, the defect sizes indicated by the four calibration curves can be used to determine the size of the target defect through weighted fusion to generate defect detection information.

[0138] Therefore, by configuring different calibration curves for different detection channels, it is possible to adapt to actual scenarios with different directions and detection channel response capabilities, thereby enhancing the detection system's adaptability to complex defect types and complex optical configurations.

[0139] Generation method four: determine the location of the defect.

[0140] The object to be tested can rotate at a constant speed on the loading platform. When a defect (such as a particle) at a certain position of the object to be tested moves to the detection area (such as the line spot 109), the particle is illuminated and emits signal light to the surrounding area, which is captured by each detection channel and finally imaged by the detector. The position of the defect on the object to be tested can be calculated based on the original image stored in the detector and the movement speed of the motion platform.

[0141] As used herein, the term "including" and its variations are open-ended, i.e., "including but not limited to." The term "based on" means "based, at least in part, on." The term "one embodiment" means "at least one embodiment," the term "another embodiment" means "at least one additional embodiment," and the term "some embodiments" means "at least some embodiments." Other terms are defined in the following description.

[0142] It should be understood that in this application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or plural.

[0143] It should also be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0144] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0145] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to 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 loading platform, an illumination assembly, and a plurality of detection channels, wherein the plurality of detection channels are located on the same detection surface, each of the detection channels is configured with at least one detector, and the plurality of detection channels include a first detection channel, a second detection channel, a third detection channel, and a fourth detection channel; The loading platform is used to carry the object to be tested, and the target normal line of the object to be tested vertically passes through the loading platform; The lighting assembly is configured to emit a detection light beam toward the object to be measured, wherein the detection light beam is scattered by the object to be measured to form at least one beam of signal light; The plurality of 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 to be detected based on the signal light; Among them, the first detection channel and the second detection channel respectively have obtuse angles with the target normal, the third detection channel and the fourth detection channel respectively have acute angles with the target normal, 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 a plane formed by the optical axis of the detection light beam and the target normal.

2. The detection system according to claim 1, characterized in that The detection range is the signal light intensity range that the detection channel can identify. The first detection range of the first detection channel is different from the second detection range of the second detection channel. 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 configured with a first polarization device and / or a first attenuation device; The second detection channel is configured with a second polarization device and / or a second attenuation device; The third detection channel is configured with a third polarization device and / or a third attenuation device; The fourth detection channel is configured with a fourth polarization device and / or a fourth attenuation device; Wherein, 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 and the fourth polarization device have different polarization parameters, and the third attenuation device and the fourth attenuation device have different attenuation parameters.

4. The detection system according to claim 1, characterized in that The lighting assembly is used to emit a detection light beam to the object to be tested to form a point light spot; or, The lighting assembly is used to emit a detection light beam to the object to be tested to form a line light spot.

5. The detection system according to claim 4, characterized in that: If the lighting assembly is used to emit a detection light beam to the object to be detected to form a linear light spot, the detection surface is perpendicular to the long side of the linear light spot.

6. The detection system according to claim 1, characterized in that The lighting assembly includes a first lighting assembly and a second lighting assembly. The first lighting assembly is configured to emit a first detection beam toward the object to be tested along the target normal, and the second lighting assembly is configured to emit a second detection beam toward the object to be tested along an oblique angle with respect to the loading platform.

7. A detection method, characterized in that: Applied to the detection system according to claims 1-6, the method comprises: sending a detection light beam to the object to be detected; Acquire a first signal light collected by the first detection channel, a second signal light collected by the second detection channel, a third signal light collected by the third detection channel, and a fourth signal light collected by the fourth detection channel; Defect detection information of the object to be tested is generated according to the first signal light, the second signal light, the third signal light, and the fourth signal light.

8. The method according to claim 7, characterized in that Generating defect detection information of the object to be tested according to the first signal light, the second signal light, the third signal light, and the fourth signal light includes: determining a signal intensity ratio of a narrow channel to a wide channel based on the first signal light, the second signal light, the third signal light, and the fourth signal light, wherein 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 a signal strength ratio threshold, generating defect detection information indicating that the target defect is a pit-type defect; If the signal intensity ratio is less than the signal intensity ratio threshold, defect detection information indicating that the target defect is a protrusion defect is generated.

9. The method according to claim 8, characterized in that The determining, based on the first signal light, the second signal light, the third signal light, and the fourth signal light, a signal intensity ratio of a narrow channel to a wide channel includes: The signal intensity ratio of the narrow channel to the wide channel is determined based on a ratio of the narrow channel signal intensity to the wide channel signal intensity and a compensation parameter, where the narrow channel signal intensity is the sum of the signal intensities of the third signal light and the fourth signal light, and the wide channel signal intensity is the sum of the signal intensities of the first signal light and the second signal light. The compensation parameter is used to compensate for the signal intensity ratio.

10. The method according to claim 9, characterized in that 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, which is expressed by the following formula: ； in, is the ratio of the narrow channel signal strength to the wide channel signal strength, is the signal light intensity of the third signal light, is the signal light intensity of the fourth signal light, is the signal light intensity of the first signal light, is the signal light intensity of the second signal light, is the compensation parameter.

11. The method according to claim 9, characterized in that The compensation parameter and the signal strength ratio threshold are determined in the following manner: Acquire a first set and a second set, wherein the first set includes a plurality of initial compensation parameters, and the second set includes a plurality of initial signal strength ratio thresholds; Determining defect prediction values ​​of a plurality of DUT samples according to a target combination, wherein the target combination includes an initial compensation parameter and an initial signal intensity ratio threshold; Determining a defect prediction accuracy rate of the target combination according to the defect prediction values ​​of the plurality of test object samples and the actual defect values ​​of the plurality of test object samples; Taking each combination determined by the first set and the second set as the target combination, and determining the defect prediction accuracy of each combination; 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.

12. The method according to claim 7, characterized in that The method further comprises: Obtaining a first calibration curve for the first detection channel, a second calibration curve for the second detection channel, a third calibration curve for the third detection channel, and a fourth calibration curve for the fourth detection channel; Generating defect detection information of the object to be tested according to the first signal light, the second signal light, the third signal light, and the fourth signal light includes: Defect detection information indicating the size of a target defect is generated 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.

13. The method according to claim 7, characterized in that Generating defect detection information of the object to be tested according to the first signal light, the second signal light, the third signal light, and the fourth signal light includes: determining a wide channel signal intensity ratio according to the first signal light and the second signal light; determining a narrow channel signal intensity ratio according to the third signal light and the fourth signal light; Defect detection information is generated based on the wide-channel signal intensity ratio and the narrow-channel signal intensity ratio to indicate whether the target defect is a symmetrical defect. If the difference between the wide-channel signal intensity ratio and the narrow-channel signal intensity 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 intensity ratio and the narrow-channel signal intensity and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect.

14. The method according to claim 13, characterized in that The generating, according to the wide channel signal intensity ratio and the narrow channel signal intensity ratio, defect detection information indicating whether the target defect is a symmetric defect comprises: Determining a mean of the wide channel signal strength ratio and the narrow channel signal strength ratio; Generating defect detection information indicating whether the target defect is a symmetrical defect based on the difference between the mean and 1, wherein if the difference between the wide channel signal intensity ratio and the narrow channel signal intensity ratio and 1 is less than a first difference threshold, the target defect is a symmetrical defect; and if the difference between the wide channel signal intensity ratio and the narrow channel signal intensity and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect; or determining a maximum value of the wide channel signal intensity ratio and the narrow channel signal intensity ratio; 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, wherein if the difference between the wide channel signal intensity ratio and the narrow channel signal intensity 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 intensity ratio and the narrow channel signal intensity and 1 is greater than a second difference threshold, the target defect is an asymmetrical defect.

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