Wafer inspection method and apparatus

Abstract

A wafer inspection method and apparatus. The method comprises: generating first illumination light; irradiating the first illumination light onto the surface of a wafer, so as to form a first light spot; detecting scattered light from the surface of the wafer on one or more detection channels (21, 22, 23, 24), wherein there is a first angle between a first projection, on the surface of the wafer, of the optical axis of a first detection channel (21) among the one or more detection channels and a first illumination light path projection of the first illumination light on the surface of the wafer, the first angle ranges from 35 degrees to 55 degrees, and at least one detection channel (21, 22, 23, 24) among the one or more detection channels (21, 22, 23, 24) uses a polarizing assembly (212, 222, 232, 242) to filter out background light from the scattered light, so as to obtain signal light of defects on the wafer; and using a detection module (4) to receive the signal light, so as to detect the defects on the wafer.

Description

Wafer inspection methods and apparatus

[0001] Technical Field

[0002] This disclosure relates to the technical field of laser inspection, and more specifically, to a wafer inspection method and a wafer inspection device.

[0003] Background Technology

[0004] Wafer defect detection technology locates and detects defects such as particles and scratches on wafers, effectively improving the yield rate of chip manufacturing and is an important technology in the semiconductor manufacturing process. Unlike bright-field illumination, which directly collects reflected light, dark-field defect detection technology collects scattered light from specific areas to determine defects. A high-precision, high-speed displacement stage is used to move the wafer and complete the overall wafer inspection. Its high precision and high-speed detection characteristics and advantages are widely used in wafer defect detection.

[0005] Current research suggests using line scanning technology to improve the illumination range and simultaneously perform scattered light imaging detection on the line-scanned area, which can effectively reduce the risk of wafer damage. However, the minimum size of defects that wafer inspection technology can detect depends on the signal strength and noise level. Effectively increasing the signal strength of specific defects and reducing background noise are key to improving detection accuracy. Furthermore, wafers contain defects of various shapes, and different defects respond differently to signal light. Therefore, it is necessary to effectively identify multiple different types of defects to improve detection capabilities.

[0006] Summary of the Invention

[0007] To address the shortcomings of existing wafer inspection technologies, embodiments of this disclosure provide a wafer inspection method and a wafer inspection apparatus.

[0008] In a first aspect, this disclosure provides a wafer inspection method. The method includes: generating a first illumination light; illuminating the first illumination light onto the surface of a wafer to form a first light spot; detecting scattered light from the surface of the wafer on one or more detection channels, wherein the optical axis of the first detection channel in the one or more detection channels has a first angle between a first projection on the surface of the wafer and a first illumination light path projection on the surface of the wafer, the first angle being in the range of 35 degrees to 55 degrees; wherein at least one detection channel in the one or more detection channels uses a polarization component to filter out background light from the scattered light to obtain signal light indicating defects in the wafer; and receiving the signal light using a detection module to detect defects in the wafer.

[0009] Optionally, the first detection channel is located on the first side of the first light spot, and the incident direction of the first illumination light is located on the second side of the first light spot, with the first side and the second side being opposite to each other.

[0010] Optionally, the first light spot is a rectangular light spot, and the projection of the first illumination light path on the surface of the wafer forms a second angle between the first illumination light path projection and the first axis of the first light spot, the second angle ranging from 30 degrees to 60 degrees; the optical axis of the first detection channel forms a third angle between the first projection on the surface of the wafer and the first axis of the first light spot, the third angle ranging from 85 degrees to 95 degrees.

[0011] Optionally, the first axis is the major axis of the first light spot, the first angle and the second angle are 45 degrees, and the third angle is 90 degrees.

[0012] Optionally, the first illumination light includes a component with a first polarization direction, the first polarization direction being perpendicular to the first illumination light path projection on the surface of the wafer and the first illumination light path forming a first plane.

[0013] Optionally, each of at least one of the one or more detection channels includes a half-wave plate and a polarizing beam splitter (PBS). Detecting the scattered light from the surface of the wafer on the one or more detection channels includes: rotating the optical axis of the half-wave plate in each of the at least one detection channel to change the background light into linearly polarized light with a second polarization direction, wherein the second polarization direction is perpendicular to the first polarization direction; and filtering the linearly polarized light with the second polarization direction using the polarizing beam splitter (PBS).

[0014] Optionally, the one or more detection channels further include one or more of a second detection channel, a third detection channel, and a fourth detection channel; the angle between the first projection of the optical axis of the first detection channel on the surface of the wafer and the fourth projection of the optical axis of the fourth detection channel on the surface of the wafer is between -5 degrees and +5 degrees; the angle between the second projection of the optical axis of the second detection channel on the surface of the wafer and the first axis of the first light spot is between -5 degrees and +5 degrees; the angle between the third projection of the optical axis of the third detection channel on the surface of the wafer and the projection of the path of the first illumination light on the surface of the wafer illumination light path is between -5 degrees and +5 degrees.

[0015] Optionally, each of the first, second, third, and fourth detection channels includes a detection lens and a detection camera. The method further includes one or more of the following steps: setting the optical axis of the detection lens of the first detection channel, the second axis of the first light spot, and the optical axis of the detection camera of the first detection channel in a second plane; setting the optical axis of the detection lens of the second detection channel, the first axis of the first light spot, and the optical axis of the detection camera of the second detection channel in a third plane; setting the optical axis of the detection lens of the third detection channel, the path of the first illumination light, and the optical axis of the detection camera of the third detection channel in a first plane; setting the optical axis of the detection lens of the fourth detection channel, the second axis of the first light spot, and the optical axis of the detection camera of the fourth detection channel in the second plane, wherein the first axis is perpendicular to the second axis.

[0016] Optionally, the wafer inspection method further includes: generating a second illumination light; irradiating the surface of the wafer with the second illumination light to form a second light spot, wherein one or more of the size, position, and intensity distribution of the second light spot are the same as one or more of the size, position, and intensity distribution of the first light spot, and the projection of the second illumination light path on the surface of the wafer is the same as the first axis of the first light spot; and detecting the scattered light of the second light spot on one or more of the first detection channel, the second detection channel, and the fourth detection channel.

[0017] Optionally, the method further includes: adjusting one or more detection channels from the first detection channel to the fourth detection channel to achieve clear imaging; acquiring the signal intensity Is of one or more detection channels from the first detection channel to the fourth detection channel, wherein the signal intensity Is is the sum of the scattered light intensity collected by each detection channel; and determining the defect type by comparing the signal intensity Is of one or more detection channels from the first detection channel to the fourth detection channel.

[0018] In a second aspect, this disclosure also provides a wafer inspection apparatus, comprising: a first illumination component configured to generate a first illumination light and irradiate the first illumination light onto the surface of the wafer to form a first light spot; one or more detection channels configured to detect scattered light from the surface of the wafer on the one or more detection channels, wherein the optical axis of the first detection channel of the one or more detection channels has a first angle between a first projection on the surface of the wafer and a first illumination light path projection on the surface of the wafer, the first angle being in the range of 35 degrees to 55 degrees, wherein at least one of the one or more detection channels uses a polarization component to filter out background light in the scattered light to obtain signal light for defects in the wafer; and a detection module configured to receive the signal light to detect defects in the wafer.

[0019] Optionally, the first detection channel is located on the first side of the first light spot, and the incident direction of the first illumination light is located on the second side of the first light spot, with the first side and the second side being opposite to each other.

[0020] Optionally, the first light spot is a rectangular light spot, and the projection of the first illumination light path on the surface of the wafer forms a second angle between the first illumination light path projection and the first axis of the first light spot, the second angle ranging from 30 degrees to 60 degrees; the optical axis of the first detection channel forms a third angle between the first projection on the surface of the wafer and the first axis of the first light spot, the third angle ranging from 85 degrees to 95 degrees.

[0021] Optionally, the first axis is the major axis of the first light spot, the first angle and the second angle are 45 degrees, and the third angle is 90 degrees.

[0022] Optionally, the first illumination light includes a component with a first polarization direction, the first polarization direction being perpendicular to the first illumination light path projection on the surface of the wafer and the first illumination light path forming a first plane.

[0023] Optionally, each of at least one of the one or more detection channels includes a half-wave plate and a polarizing beam splitter (PBS), and the detection device is further configured to: rotate the optical axis of the half-wave plate in each of the at least one detection channel to change the background light into linearly polarized light with a polarization direction perpendicular to the first polarization direction; and filter out the linearly polarized light using the polarizing beam splitter (PBS).

[0024] Optionally, the one or more detection channels further include one or more of a second detection channel, a third detection channel, and a fourth detection channel; the angle between the first projection of the optical axis of the first detection channel on the surface of the wafer and the fourth projection of the optical axis of the fourth detection channel on the surface of the wafer is between -5 degrees and +5 degrees; the angle between the second projection of the optical axis of the second detection channel on the surface of the wafer and the first axis of the first light spot is between -5 degrees and +5 degrees; the angle between the third projection of the optical axis of the third detection channel on the surface of the wafer and the projection of the path of the first illumination light on the surface of the wafer illumination light path is between -5 degrees and +5 degrees.

[0025] Optionally, each of the first, second, third, and fourth detection channels includes a detection lens and a detection camera. The optical axis of the detection lens, the second axis of the first light spot, and the optical axis of the detection camera of the first detection channel are arranged in a second plane; the optical axis of the detection lens, the first axis of the first light spot, and the optical axis of the detection camera of the second detection channel are arranged in a third plane; the optical axis of the detection lens, the path of the first illumination light, and the optical axis of the detection camera of the third detection channel are arranged in a first plane; and the optical axis of the detection lens, the second axis of the first light spot, and the optical axis of the detection camera of the fourth detection channel are arranged in the second plane, wherein the first axis is perpendicular to the second axis.

[0026] Optionally, the wafer inspection device further includes: a second illumination component configured to generate a second illumination light, which illuminates the surface of the wafer to form a second light spot, wherein one or more of the size, position, and intensity distribution of the second light spot are the same as one or more of the size, position, and intensity distribution of the first light spot, and the projection of the path of the second illumination light on the surface of the wafer is the same as the first axis of the first light spot; the detection module is further configured to detect the scattered light of the second light spot on one or more of the first detection channel, the second detection channel, and the fourth detection channel.

[0027] Optionally, the detection module is further configured to: adjust one or more detection channels from the first detection channel to the fourth detection channel to achieve clear imaging; acquire the signal intensity Is of one or more detection channels from the first detection channel to the fourth detection channel, wherein the signal intensity Is is the sum of the scattered light intensity collected by each detection channel; and determine the defect type by comparing the signal intensity Is of one or more detection channels from the first detection channel to the fourth detection channel.

[0028] Attached image description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0030] Figure 1 is a flowchart of the wafer defect detection method disclosed herein;

[0031] Figure 2A is a first schematic diagram of the structure of the first lighting component of this disclosure and its arrangement relative to the wafer;

[0032] Figure 2B is a second schematic diagram showing the structure of the first lighting component of this disclosure and its arrangement relative to the wafer;

[0033] Figure 3A is a schematic diagram showing the relationship between the polarization direction of the scattered light from the particle defects and the polarization direction of the background scattered light from the wafer surface at a 90-degree lateral position in the direction of illumination.

[0034] Figure 3B is a schematic diagram showing the relationship between the polarization direction of the scattered light from the particle defects and the polarization direction of the background scattered light from the wafer surface at a 45-degree angle to the side of the direction of illumination.

[0035] Figure 4A is a top view showing the positional relationship between the first detection channel and the wafer disclosed herein;

[0036] Figure 4B is a side view of the positional relationship between the first probe channel and the wafer disclosed herein;

[0037] Figure 4C is a schematic diagram of the optical path of the first detection channel of this disclosure;

[0038] Figure 4D is a schematic diagram showing the defocusing situation caused by different placement methods of the detection channel and the light spot;

[0039] Figure 5A is a top view showing the positional relationship between the first to fourth detection channels and the wafer in this disclosure;

[0040] Figure 5B is a side view of the positional relationship between the first to fourth probe channels and the wafer of this disclosure;

[0041] Figure 5C is a schematic diagram of the scattering characteristics of different types of defects in this disclosure;

[0042] Figure 5D is a schematic diagram of the optical path of the second detection channel of this disclosure;

[0043] Figure 5E is a schematic diagram of the optical path of the third detection channel of this disclosure;

[0044] Figure 5F is a schematic diagram of the optical path of the fourth detection channel of this disclosure;

[0045] Figure 6 is a schematic diagram of how the second detection channel of this disclosure improves the dynamic range of defect detection;

[0046] Figure 7 is a flowchart of the steps for defect detection using the first to fourth detection channels of this disclosure;

[0047] Figure 8A is another side view showing the positional relationship between the first, third, and fourth detection channels of this disclosure and the wafer;

[0048] Figure 8B is another top view showing the positional relationship between the first, third, and fourth detection channels of this disclosure and the wafer;

[0049] Figure 8C is another structural schematic diagram of the first detection channel of this disclosure;

[0050] Figure 9 is a schematic diagram of the method for setting up the second detection channel in this disclosure;

[0051] Figure 10A is a side view of the positional relationship of the second illumination component of this disclosure relative to the wafer;

[0052] Figure 10B is a top view of the positional relationship of the second illumination component of this disclosure relative to the wafer;

[0053] Figure 10C is a top view of the positional relationship of the probe channel relative to the wafer when the present disclosure is illuminated using the first illumination component;

[0054] Figure 10D is a side view of the positional relationship of the probe channel relative to the wafer when the present disclosure is illuminated using the first illumination component;

[0055] Figure 10E is a top view of the positional relationship of the probe channel relative to the wafer when the present disclosure is illuminated using a second illumination component;

[0056] Figure 10F is a side view of the positional relationship of the probe channel relative to the wafer when the present disclosure is illuminated using the second illumination assembly.

[0057] Detailed Implementation Methods

[0058] The term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0059] It should be understood that although the terms first, second, third, etc., may be used to describe different objects in the embodiments of this disclosure, these objects should not be limited to these terms. These terms are only used to distinguish these objects. For example, first may also be referred to as second without departing from the scope of the embodiments of this disclosure, and similarly, second may also be referred to as first.

[0060] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the article or device that includes said element.

[0061] Line scan illumination in related wafer inspection technologies requires imaging the line area. In this technology, to collect scattered light at a wider angle, a single large numerical aperture (NA) lens is often used. The design, fabrication, and assembly of such lenses are complex, and their large size limits the angle of the illumination path. The minimum defect size that wafer inspection technology can detect depends on the signal and noise levels. A single large NA lens cannot be configured to address the intensity variations of wafer defects in different scattering directions, and cannot effectively remove background scattered light, resulting in a low signal-to-noise ratio (SNR). Furthermore, wafers contain defects of various shapes, each responding differently to signal light. A single large NA lens cannot determine the defect type based on the directional characteristics of the intensity variations of scattered light from different defects in different directions.

[0062] Furthermore, in methods employing non-point scanning and multiple detection channels to detect wafer defects, the signal light used for defect detection originates from a linear region on the wafer plane. In this case, the plane of the photodetector is not naturally parallel to the detection area on the wafer surface. The optical path length from the corresponding conjugate point of the photodetector may differ at different locations within the detection area, and defocusing can easily occur at some points within the detection area, affecting detection accuracy. The challenge of this method lies in the placement of the detection device and detection channels. Related technologies require effective separation of background scattered light and defect signal light to achieve specific detection of the defect signal.

[0063] The disclosed solution employs one or more small NA lenses, with multiple channels of small NA lenses placed in different orientations and positions, replacing a single normal large NA lens. A detection channel is set up in a direction ranging from 35 to 55 degrees laterally to the direction of illumination light propagation for detection. This ensures that the polarization direction of the signal scattered light from the wafer defect is substantially perpendicular to the polarization direction of the background scattered light from the wafer. The background scattered light from the wafer can be filtered out using a polarization device, improving the signal-to-noise ratio (SNR) and enhancing detection accuracy. Furthermore, the disclosed solution can utilize multiple small NA lenses working together to obtain defect information. Since the development difficulty of small NA lenses is relatively lower than that of large NA lenses, the solution of this application can reduce costs. In addition, the use of one or more detection channels in the disclosed solution can avoid the problem of defocusing caused by the tilting of the focused spot of the signal light. The disclosed solution can also achieve simultaneous identification and detection of multiple defect types. The technical solution of this application is described in detail below.

[0064] Figure 1 is a flowchart of the wafer defect detection method of this disclosure. Referring to Figure 1, the wafer defect detection method of this disclosure includes the following steps S101-S105.

[0065] Step S101: Generate the first illumination light.

[0066] Specifically, referring to Figures 2A and 2B, which are schematic diagrams of the structure of the first illumination component 1 used in this disclosure, Figure 2A shows a view parallel to the surface of the wafer (i.e., a side view of the wafer plane), and Figure 2B shows a view perpendicular to the surface of the wafer (i.e., a top view of the wafer plane). The first illumination component 1 can be used to generate first illumination light.

[0067] The first illumination component 1 may include a first laser 11. The first laser 11 can generate laser light. In some embodiments, the laser light is unpolarized light. The wavelength of the laser light may be a deep ultraviolet (DUV) laser in the range of 100nm-300nm, such as 266nm or 193nm; or an ultraviolet (UV) laser in the range of 300-400nm.

[0068] Related wafer defect detection techniques involve perpendicularly positioning the incident plane of the illumination light (i.e., the plane formed by the projection of the illumination light path onto the wafer surface and the illumination light path itself) and the detection plane (i.e., the plane formed by one or more optical axes from one or more detection channels). The direction of illumination light propagation maintains a specific angle with the wafer normal, while the optical axes of one or more detection channels maintain other specific and asymmetrical angles with the wafer normal. The optical axes of one or more detection channels are perpendicular to the line spot. This detection technique collects the signal scattered light from defects and the background scattered light from the wafer surface from the incident plane at a 90-degree angle to the detection plane. The drawback of this technique is that the polarization direction of the collected defect scattered light signal is not completely orthogonal to the polarization direction of the background scattered light signal from the wafer, resulting in an inability to completely separate the background scattered light signal from the defect light signal, leading to a low signal-to-noise ratio. In the field of wafer probing, the signal-to-noise ratio (SNR) refers to the proportion of effective defect-scattered light signal in the background scattered signal of the wafer. SNR can be expressed as (defect signal intensity - average background scattered signal intensity) ÷ (maximum background signal intensity - minimum background signal intensity). Generally, (maximum background signal intensity - minimum background signal intensity) represents the fluctuation of the wafer's background scattered signal. According to this formula, an effective way to improve SNR is to increase the intensity of the obtained defect signal while simultaneously reducing the average intensity of the background scattered signal. Referring to Figure 3A, Figure 3A is a schematic diagram showing the relationship between the polarization direction of the scattered light from the particle defects and the polarization direction of the background scattered light from the wafer surface at 80 to 100 degrees (90 ± 10 degrees) lateral to the incident plane of the illumination light. In Figure 3A, the polarization direction of the illumination light is perpendicular to the incident plane of the illumination light at 90 degrees (e.g., the illumination light is P-polarized or S-polarized). As can be seen from Figure 3A, at a position between 80 and 100 degrees laterally in the direction of illumination, the perpendicularity between the polarization direction of the background scattered light from the wafer and the polarization direction of the scattered light from the wafer's defects (i.e., the signal light) is large and between 90 degrees. Therefore, the background noise cannot be effectively separated, and the signal-to-noise ratio cannot be maximized.

[0069] Figure 3B is a schematic diagram showing the relationship between the polarization direction of the scattered light generated by the particle defect and the polarization direction of the background scattered light from the wafer surface within a lateral range of 35 to 55 degrees in the direction of illumination. Referring to Figure 3B, when the polarization direction of the illumination light is 90 degrees lateral to the direction of illumination (e.g., the illumination light is P-polarized), the polarization direction of the scattered light generated by the particle defect is radially distributed, and the polarization direction of the background scattered light is shown in the middle of Figure 3B. This disclosure uses a detection channel to perform detection in a direction within a lateral range of 35 to 55 degrees in the direction of illumination. At this location, the polarization direction of the defect signal light is perpendicular or approximately perpendicular to the polarization direction of the background scattered light signal from the wafer. Detection in this region, combined with a polarization separation element, can separate the background light signal from the defect light signal, essentially filtering out the background light and minimizing the loss of the particle defect signal light, thereby improving the signal-to-noise ratio (SNR) of the defect signal. In this way, the scheme of this disclosure can effectively improve the SNR of the defect signal.

[0070] In the embodiments of this disclosure, the illumination light can be light of other polarization states containing P-polarized light. The illumination light can be equivalently composed of P-polarized light with intensity I1 and S-polarized light with intensity I2, with a total illumination light intensity of I. Since the vibration directions of P-polarized light and S-polarized light are perpendicular, they will not interfere with each other. The collected light signal is approximately equal to the sum of the signal light intensity obtained by P-polarized light of intensity I1 alone and the signal light intensity obtained by S-polarized light of intensity I2 alone. Therefore, when illumination is provided by other polarization states of non-pure P-polarized light and non-pure S-polarized light, the scheme of this disclosure can also improve the SNR of the scattered light signal from defects. The greater the intensity of P-polarized light contained in the illumination light, i.e., the greater the intensity ratio I1 / (I1+I2), the higher the proportion of the scattered light signal from defects in the background scattering signal of the wafer, and the better the SNR improvement effect (when I2=0, the illumination light contains only P light, and the intensity ratio of P-polarized light to illumination light is 1, at which point the SNR can reach its maximum value).

[0071] In some embodiments, to obtain P-polarized or S-polarized light, a first polarization structure 12 can be provided in the first illumination component 1 to control the polarization of the laser emitted from the first laser 11, thereby obtaining P-polarized or S-polarized light. The laser emitted by the first laser 11 may include a first component in the P-polarization direction and a second component in the S-polarization direction. In embodiments of this disclosure, to improve the SNR of the signal light, it is necessary to include a component perpendicular to the incident plane in the polarization direction of the illumination light. In embodiments of this disclosure, P-polarized light is used as an example. P-polarized light is transmitted through the first polarization structure 12, and S-polarized light is reflected from the first polarization structure 12. The first polarization structure 12 may include a half-wave plate, a polarizing beam splitter (PBS), and a polarizer. In some embodiments, the polarizer may be a Brewster polarizer. The half-wave plate rotates the laser polarization state, and the half-wave plate, in conjunction with the polarizing beam splitter, can achieve variable-ratio beam splitting. Polarizers can efficiently separate polarized light in the P-polarization direction (P-polarized light) or polarized light in the S-polarization direction (S-polarized light).

[0072] In some other embodiments, the first illumination component 1 may not include the first polarization structure 12. In this case, the illumination light may be light of other polarization states, including P-polarized light.

[0073] In embodiments of this disclosure, the first illumination component 1 further includes a first shaper 13. The first shaper 13 is configured to obtain an optical signal from the first laser 11 or the first polarization structure 12 and to shape the optical signal. The first shaper 13 may include a freeform refractive lens, which precisely controls the light refraction path through local curvature changes. Based on Snell's law and the law of conservation of energy, the freeform refractive lens redistributes the optical signal obtained from the first polarization structure 12 to form a circular spot or a linear spot (the ratio of the major axis length to the minor axis length is greater than 2 (major axis:minor axis > 2), such as a rectangle or an ellipse) or a target spot with a uniformity > 90%.

[0074] Step S102: Illuminate the first illumination light at a first incident angle onto the surface of the wafer to form a first light spot.

[0075] In some embodiments of this disclosure, the first light spot can be of any shape. Embodiments of this disclosure collect signal light at a position between 35 and 55 degrees (e.g., 45 degrees) laterally to the projection of the first illumination path onto the surface of the wafer. This effectively filters out background scattered light and improves the SNR by utilizing the essentially perpendicular polarization directions between the signal light and the background scattered light. In other embodiments of this disclosure, the first light spot is a rectangular spot having a major axis and a minor axis. The first axis can be the major axis. The rectangular spot can have a long side and a short side, and the ratio of the length of the long side to the short side can be greater than 2:1. A second angle is formed between the major axis of the first light spot and the projection of the first illumination path onto the surface of the wafer. In some embodiments, the range of the second angle can be 30 to 60 degrees, for example, 35 to 55 degrees, such as 45 degrees. In this embodiment, due to the arrangement of the first illumination component 11 and the first light spot, the angle between the long axis of the first light spot and the projection of the first illumination light path onto the wafer surface is not 90 degrees. Therefore, the optical path lengths at both ends of the long axis direction of the first illumination light reaching the first light spot are different. To compensate for this optical path difference, a first shaper 13 (freeform refractive lens) can be used to achieve focusing, so as to obtain the same optical path length at both ends of the long axis direction of the first illumination light reaching the first light spot. The first shaper includes two freeform surface lenses: a first freeform surface lens (Lens1) and a second freeform surface lens (Lens2). These lenses are arranged sequentially along the light propagation direction. Lens1 has a planar incident surface and a freeform exit surface; Lens2 has a freeform incident surface and a planar exit surface. The first freeform surface lens controls the length of the rectangular light spot and the uniformity of energy distribution at the working surface. The second freeform surface lens controls the linewidth of the rectangular light spot at the working surface and is used for defocus compensation, thereby ensuring the linelight spot is in focus. The surface shape of the aforementioned freeform surface can be expressed by the following expression:

[0076] Among them,  represents a quantity related to the curvature of the parent surface at off-axis points;

[0077]  , representing a quantity related to the normal direction or focal length of the off-axis quadratic surface;

[0078] Among them,

[0079]  This represents a constant term, indicating the overall translation in the Z direction, which adjusts the axial position of the surface in the optical path. Represents the tilt term, which represents the linear tilt around the X-axis and is used to tilt the surface relative to the optical axis. Represents the off-axis quadratic surface reference term, used to control the focusing function of the optical system; This represents the freeform surface correction term, used for precise aberration correction;

[0080] R is the radius of curvature of the parent quadratic surface at its vertex; R > 0 indicates a convex surface, and R < 0 indicates a concave surface.

[0081] φk is the conic constant, which determines the type of the reference quadratic surface;

[0082]  It is the off-axis distance along the y-axis, which is the offset of the center of the freeform surface relative to the vertex of the parent surface in the Y direction;

[0083]  It is the normalized radius of the polynomial coefficients of the freeform surface;

[0084] ∅z(x,y) is the surface profile elevation of the freeform surface, and (x,y) is the coordinate of the freeform surface diameter position.

[0085]  It is the freeform surface coefficient, representing the additional surface shape deviation coefficient of the freeform surface relative to the reference surface.

[0086] Polynomial Represented as:

[0087] 

[0088] The range of j is 0 to 19, and the range of k is 0 to 20, and j + k ≤ 20;

[0089] For len1, the maximum order of j / k is 76, and for len2, the maximum order of j / k is 10.

[0090] In some embodiments, the first illumination component 1 further includes a first reflector 14, configured to reflect the light signal emitted by the first shaper 13 to generate first illumination light. The first illumination light is incident on the surface of the wafer at a first incident angle, forming a first light spot. The first incident angle can be the angle between the path of the first illumination light and the projection of the first illumination light path onto the surface of the wafer. The range of the first incident angle can be 60 degrees to 80 degrees, for example, 70 degrees. When the first polarization structure 12 is used, the polarization direction of the first illumination light is perpendicular to the incident surface of the first illumination light, which is the plane formed by the path of the first illumination light and the projection of the first illumination light path onto the wafer.

[0091] Step S103: Detect the scattered light on the surface of the wafer on one or more detection channels, wherein the optical axis of the first detection channel in the one or more detection channels has a first angle between the first projection of the first detection channel on the surface of the wafer and the first illumination path projection of the first illumination light on the surface of the wafer, wherein at least one detection channel in the one or more detection channels uses a polarization component to filter out the background light and obtain the signal light of the defect of the wafer.

[0092] Specifically, referring to Figures 4-7, which are schematic diagrams of the arrangement of the detection channel according to this disclosure. In these embodiments, a detection channel is placed 35-55 degrees laterally in front of the path of the first illumination light. That is, there is a first angle of 35-55 degrees (e.g., 45 degrees) between the first projection of the optical axis of this detection channel on the surface of the wafer and the projection of the first illumination light path on the surface of the wafer. The incident positions of the detection channel and the first illumination light are located on both sides of the long axis of the first light spot. Based on the arrangement described in Figure 3B, setting the detection channel at this position can utilize the spatial distribution characteristics of the polarization direction of the defect scattered light signal and the background light signal (the polarization direction of the defect signal light is perpendicular or approximately perpendicular to the polarization direction of the background scattered light signal of the wafer) and the intensity distribution characteristics, in conjunction with the polarization separation element, to basically completely separate the background light signal and the defect light signal, thereby effectively filtering out the background scattered light and maximizing the signal-to-noise ratio (SNR) of the obtained signal light. The angle between the optical axis of the probe channel and its projection onto the surface of the wafer (i.e., the tilt angle β of the probe channel) can range from 30 degrees to 90 degrees, for example, from 30 degrees to 60 degrees or from 40 degrees to 70 degrees. This tilt angle can be adjusted according to the application of different systems.

[0093] In some embodiments of this disclosure, when the first light spot is a rectangular light spot, the projection of the optical axis of the detection channel onto the surface of the wafer forms a third angle between the projection and the long axis of the first light spot. This third angle ranges from 85 degrees to 95 degrees, for example, 90 degrees. The optical axis of the detection channel is inclined relative to the short side of the rectangular linear light spot.

[0094] In the embodiments disclosed herein, the optical axis refers to the axis of symmetry of the optical system, around which the light beam rotates without any change in optical properties.

[0095] Optionally, the detection channel configuration of this disclosure utilizes the focusing characteristics of the illumination light, making the optical axis of the detection channel inclined relative to the short side of the rectangular linear light spot and perpendicular to the long side of the rectangular linear light spot. This effectively prevents defocusing at the long edge of the first light spot. Furthermore, based on the principle described in Figure 3B, setting the detection channel at this location utilizes the spatial distribution characteristics (the polarization direction of the defect's scattered light signal is perpendicular or approximately perpendicular to the polarization direction of the wafer's background scattered light signal) and intensity distribution characteristics. Combined with a polarization separation element, this allows for near-complete separation of the background light signal and the defect light signal, effectively filtering out background scattered light and maximizing the signal-to-noise ratio (SNR) of the obtained signal light.

[0096] Step S104: Receive the signal light using the detection module to detect defects in the wafer.

[0097] In some embodiments of this disclosure, at least one of the one or more detection channels has a detection module, which may include a detection camera and a signal processing device. The detection camera may include, but is not limited to, a CCD detector, a TDI detector, a photomultiplier tube (PMT), an avalanche photodiode (APD), etc., and may be a wide-field camera, such as an area array camera. It is configured to receive the signal light, convert the signal light into an electrical signal, and forward the electrical signal to the signal processing device. The signal processing device may be a common electrical signal processing device, such as a central processing unit, which will not be described in detail here. The signal processing device may also include a control unit, which may be configured to control the detection cameras of one or more detection channels to focus. Control units are known to those skilled in the art and will not be described in detail here.

[0098] One or more detection channels in the embodiments of this disclosure can detect different types of defects individually or together, and these schemes are described in detail below.

[0099] The detection modules of each detection channel include detection lenses and detection cameras.

[0100] A detection lens is used to collect the scattered light beam from the object to be detected and image the object onto the detection camera. The detection camera may include, but is not limited to, a CCD detector, a TDI detector, a photomultiplier tube (PMT), an avalanche photodiode (APD), etc. Defects generated during wafer manufacturing can include bumps and depressions. Bump defects include particle defects, disk-shaped bumps, and elongated bumps, while depressions include pits and scratches. Furthermore, the shape of the defect also affects the illumination light differently; elongated defects and disk-shaped defects will scatter the illumination light at different angles.

[0101] For particulate defects, referring to Figures 4A and 4B, Figure 4A is a top view showing the positional relationship between the first detection channel 21 and the wafer, and Figure 4B is a side view showing the positional relationship between the first detection channel 21 and the wafer. This disclosure uses a first detection channel 21 to detect signal light for particulate defects. The first detection channel 21 includes a detection lens, and a first angle is formed between the projection of the optical axis of the detection channel onto the surface of the wafer and the projection of the path of the first illumination light onto the surface of the wafer. This angle can range from 35 degrees to 55 degrees, for example, 45 degrees. The detection channel and the incident position of the first illumination light are located on opposite sides of the long axis of the first light spot.

[0102] In some embodiments, considering the characteristics of particulate defects, the angle between the optical axis of the first detection channel 21 and its first projection onto the surface of the wafer (i.e., the tilt angle of the optical axis of the detection channel relative to the surface of the wafer) is set to β. The value of β can be adjusted according to different application systems, different detection environments, and different detection purposes. The value of β can range from 30 degrees to 90 degrees, for example, from 30 degrees to 60 degrees or from 40 degrees to 70 degrees.

[0103] Referring to Figure 4C, which is a schematic diagram of the optical path of the first detection channel of this disclosure, the first detection channel 21 includes a first detection lens 211, a first polarizer 212, and a first detection camera 213. The first polarizer 212 is located between the first detection lens 211 and the first detection camera 213 along the optical path. The optical axes of the first detection lens 211, the first polarizer 212, and the first detection camera 213 are located in the same plane. The first detection lens 211 is configured to image a first light spot onto the field of view of the first detection camera 213. The first polarizer 212 is configured to allow signal light from particle defects to pass through and block background light (i.e., background noise) from the wafer surface.

[0104] In some embodiments, the first polarizer 212 includes a first half-wave plate and a first polarizing beam splitter (PBS). By rotating the optical axis of the half-wave plate, the polarization direction of linearly polarized light can be changed. When the polarization direction of the signal light is P-polarized or the signal light includes a component in the P-polarized direction, the half-wave plate deflects the polarization component of the background light, converting it into S-polarized light, which is then reflected (filtered out) by the first PBS. The signal light in the P-polarized direction or the signal light component in the P-polarized direction passes through the first PBS, thereby filtering out the background signal.

[0105] The following steps can be used during detection:

[0106] 1. Adjust the first illumination component 1 to emit laser light from the first laser 11, and the emitted laser light irradiates the first shaper 13. Optionally, if the first illumination component 1 includes a first polarization structure 12, then the first polarization structure 12 polarizes the laser light from the laser 11 to obtain linearly polarized light, such as light polarized in the P-polarization direction.

[0107] 2. Adjust the first shaper 13 (freeform surface focusing module) of the first illumination component 1 so that the focused light spot (i.e. the first light spot) falls on the surface of the wafer, and the long axis direction of the focused light spot and the projection of the illumination light path on the wafer surface form a 45-degree angle, and the light spot is uniform.

[0108] 3. Adjust the first detection channel 21 so that the optical axis of the first detection channel is perpendicular to the long axis of the first light spot.

[0109] 4. Conduct imaging tests to ensure that the imaging surface of the detection camera is not out of focus from the illuminated area.

[0110] 5. Observe the imaging image. By rotating the half-wave plate, adjust the optical axis direction of the half-wave plate in the detection channel to minimize the background light signal. At this time, the signal of the particle defect will reach its strongest.

[0111] 6. Use the detection module to calibrate the size of particle defects.

[0112] In related wafer probing technologies, to detect scattered signal light at different angles, the probe channel is tilted at a certain angle relative to the wafer surface. The illumination spot is focused on the wafer surface, resulting in the tilted probe channel being tilted relative to the focused spot. When the angle between the optical axis of the probe channel lens and one side of the illumination spot is not 90°, the distances from the endpoints of the line spot to the lens are different. When the imaging surface is in the center, the images of both endpoints on the probe camera will be out of focus, and only the center position can effectively collect signal light, resulting in low spot utilization. Referring to Figure 4D, Figure 4D is a defocusing diagram under different placement methods of the probe channel and the spot. As shown in Figure 4D, when the optical axis of the probe channel is perpendicular to the long axis of the line spot, the defocus is small; when the optical axis of the probe channel is perpendicular to the short axis of the line spot, the defocus is large. Large defocus will cause the images of the two endpoints of the long axis to be out of focus. To address the issue of long-axis defocusing in line scanning, the optical axis of the probe lens in the probe channel is set perpendicular to the long axis of the illumination spot on the wafer, and the imaging plane of the probe camera is parallel to the long axis of the illumination spot. This effectively avoids defocusing and improves system stability and yield. Furthermore, to achieve a wider range of collection of particle defect signal light, a larger collection angle is needed in the illumination area. The numerical aperture of the lens, NA = n*sin(γ), where γ is the imaging collection angle. In an imaging lens using air as the medium, n is taken as 1. It is evident that a larger collection angle requires a larger NA. The depth of field D of the imaging system... ,in Here, NA represents the wavelength of the collected light, and NA is the numerical aperture of the lens. It is evident that the larger the numerical aperture, the smaller the depth of field of the imaging system becomes on a quadratic scale. Furthermore, a long-side-tilted collection scheme significantly limits the system's depth of field and numerical aperture, thereby restricting its signal light collection capability. The scheme disclosed herein allows the imaging lens to possess a larger NA and signal light collection capability, thus improving the system's defect detection capability.

[0113] Furthermore, to address the issue of low signal-to-noise ratio in particle defect detection in related technologies, the present invention incorporates a polarizer in the detection channel, employing a combination of a half-wave plate and a PBS. Utilizing the characteristic that the polarization directions of the background scattered light from the wafer and the particle defect light are perpendicular at approximately 45 degrees to the side of the illumination light's direction of travel, the background scattered light is filtered out, resulting in pure particle defect signal light detected and thus improving the signal-to-noise ratio of the defect signal.

[0114] In other embodiments, to detect the different characteristics of disk-shaped defects, pit defects, elongated protrusion defects, and granular defects, based on the embodiments shown in Figures 4A and 4B, and referring to Figures 5A and 5B, the embodiments of this disclosure add a second detection channel 22, a third detection channel 23, and a fourth detection channel 24. Figure 5A is a top view showing the positional relationship between the first to fourth detection channels and the wafer in an embodiment of this disclosure, and Figure 5B is a side view showing the positional relationship between the first to fourth detection channels and the wafer in an embodiment of this disclosure. The first detection channel 21 is the same as the first detection channel 21 in the embodiment of Figure 4.

[0115] In some embodiments, the angle between the first projection of the optical axis of the first detection channel 21 onto the surface of the wafer and the fourth projection of the optical axis of the fourth detection channel 24 onto the surface of the wafer is between -5 degrees and +5 degrees; the angle between the second projection of the optical axis of the second detection channel 22 onto the surface of the wafer and the first axis of the first light spot is between -5 degrees and +5 degrees; and the angle between the third projection of the optical axis of the third detection channel 23 onto the surface of the wafer and the projection of the path of the first illumination light onto the surface of the wafer is between -5 degrees and +5 degrees.

[0116] Optionally, the angle between the first projection of the optical axis of the first detection channel 21 and the fourth projection of the optical axis of the fourth detection channel 24 is 0 degrees, and the optical axis of the fourth detection channel 24 and the optical axis of the first detection channel 21 are located in the same second plane; the angle between the second projection of the optical axis of the second detection channel 22 and the major axis of the first light spot is 0 degrees, and the optical axis of the second detection channel 22 and the major axis of the first illumination spot are located in the same third plane, or the major axis of the first illumination spot is parallel to the second projection of the optical axis of the second detection channel 22. The angle between the third projection of the optical axis of the third detection channel 23 and the first illumination path projection of the first illumination light is 0 degrees, and the optical axis of the third detection channel 23 and the path of the first illumination light are located in the same first plane, or the third projection of the optical axis of the third detection channel 23 is parallel to the first fluorescence path projection of the first illumination light. When the first illumination light is P-polarized light, the polarization direction of the first illumination light is perpendicular to the first plane.

[0117] Referring to Figure 5C, which is a schematic diagram of the scattering characteristics of different types of defects, the scattering characteristics of pit-type defects, granular defects, elongated protrusions, and disc-shaped protrusions differ. Granular defects scatter stronger light intensity at low detection angles, while pit-type defects scatter stronger light intensity at high detection angles, and disc-shaped protrusions scatter stronger light intensity at low detection angles in front of the illumination direction. In this scheme, multiple detection channels are set up to address the different scattering characteristics of these defect types. When a channel is detected to be more sensitive to a certain defect, while other channels cannot detect it, the corresponding defect can be identified.

[0118] Specifically, in some embodiments, the second detection channel 22 can be configured to detect protrusion-type defects and elongated protrusion defects. The angle (i.e., tilt angle) between the optical axis of the second detection channel 22 and its second projection on the wafer surface can range from 45 degrees to 65 degrees. The numerical aperture can range from 0.1 to 0.3. The specific value of the numerical aperture depends on the optical system and the specific application. The addition of the second detection channel 22 enables the system to detect defects with other polarization directions of scattered light. Since the first detection channel 21 is positioned 45° to the side in front of the incident direction of the first illumination light, the polarization direction of the particle defect scattered signal light is exactly perpendicular to the polarization direction of the wafer surface scattered signal light, which can filter out the scattered light from the wafer surface while minimizing the loss of the particle defect scattered signal light. However, in the field of defect detection, not all defects have this polarization characteristic of particle defects. In the direction 45° in front of the incident direction of the illumination light, the polarization direction of the elongated protrusion defect is the same as the polarization direction of the scattered light from the wafer surface. If only the first detection channel 21 is used for detection, the scattered signal light from the elongated protrusion defect will be blocked by the first polarized PBS 213, which will filter it out as background scattered light from the wafer, resulting in the omission of the defect signal. Therefore, a second detection channel 22 is set in the direction of illumination light. The position of the second detection channel 22 and the position of the first detection channel 21 can be axially symmetrical with respect to the projection of the first illumination light path on the wafer surface. The joint detection of the first detection channel 21 and the second detection channel 22 can avoid the omission of elongated protrusions.

[0119] In some embodiments, the third detection channel 23 can be configured to detect disk-shaped defects. The angle (i.e., tilt angle) between the optical axis of the third detection channel 23 and its third projection on the wafer surface can range from 45 degrees to 65 degrees. The numerical aperture can range from 0.1 to 0.3. The specific value of the numerical aperture depends on the optical system and the specific application.

[0120] In some embodiments, the fourth detection channel 24 can be configured to detect pit-like defects. The angle (i.e., tilt angle) between the optical axis of the fourth detection channel 24 and its fourth projection on the wafer surface can range from 65 degrees to 90 degrees. The numerical aperture can range from 0.1 to 0.5, and the specific value of the numerical aperture depends on the optical system and the specific application. Since the optical axis of the fourth detection channel 24 is perpendicular to the major axis of the illumination spot, the fourth detection channel 24 can be adapted to imaging lenses with higher numerical apertures, which can further improve the detection capability of pit-like defects.

[0121] In some embodiments, referring to FIG5D, FIG5D is a schematic optical path diagram of the second detection channel of the present disclosure. The second detection channel 22 includes a second detection lens 221, a second polarizer 222, and a second detection camera 223. The second polarizer 222 is located between the second detection lens 221 and the second detection camera 223 along the direction of light propagation. The optical axes of the second detection lens 221, the second polarizer 222, and the second detection camera 223 are located in the same plane. The second detection lens 222 is configured to image a first light spot onto the field of view of the second detection camera 223. The second polarizer 222 is configured to filter out background light (i.e., background noise). In some embodiments, the second polarizer 222 includes a second half-wave plate and a second polarizing beam splitter (PBS). According to the principle of the half-wave plate, the fast axis of the half-wave plate produces an optical path difference of 1 / 2 wavelength compared to the slow axis. By rotating the optical axis of the half-wave plate, the polarization direction of linearly polarized light can be changed. The polarization direction of the signal light from the elongated protrusion is the same as that of the background light. The second polarization beam splitter (PBS) can filter out other scattered light with polarization directions different from both the background signal light and the signal light from the elongated protrusion. By adjusting the half-wave plate, the background signal from the wafer obtained by the second detection channel 22 is made the strongest. At this point, scanning detection can be performed to detect the signal light from the elongated protrusion, whose polarization direction is the same as that of the background scattered light from the wafer.

[0122] In some embodiments, referring to FIG5E, FIG5E is a schematic optical path diagram of the third detection channel of the present disclosure. The third detection channel 23 includes a third detection lens 231, a third polarizer 232, and a third detection camera 233. The third polarizer 232 is located between the third detection lens 231 and the third detection camera 233. The optical axes of the third detection lens 231, the third polarizer 232, and the third detection camera 233 are located in the same plane. The third detection lens 231 is configured to image a first light spot onto the field of view of the third detection camera 233. The third polarizer 232 is configured to filter out background light (i.e., background noise). In some embodiments, the third polarizer includes a third half-wave plate and a third polarizing beam splitter PBS. By rotating the optical axis of the half-wave plate, the polarization direction of the linearly polarized light can be changed. The third polarizing beam splitter PBS can filter out other scattered light with a polarization direction different from that of the signal light from the disk defect. The optical axis of the third detection channel 233 is in the same plane as the incident direction of the first illumination light and is located in front of the incident direction of the first illumination light. The third detection channel 233 is more sensitive to the detection of disk-type defects. At a low angle position in front of the illumination direction, the scattered energy of disk-type defects is more concentrated. Placing the detection channel at this position can obtain the maximum scattered energy of disk-type defects and achieve the maximum signal-to-noise ratio.

[0123] In some embodiments, referring to FIG5F, FIG5F is a schematic diagram of the optical path of the fourth detection channel of the present disclosure. The fourth detection channel 24 includes a fourth detection lens 241, a fourth polarizer 242, and a fourth detection camera 243. The fourth polarizer 243 is located between the fourth detection lens 241 and the fourth detection camera 243 along the optical path. The optical axes of the fourth detection lens 241, the fourth polarizer 242, and the fourth detection camera 243 are located in the same plane. The fourth detection lens 241 is configured to image a first light spot onto the field of view of the fourth detection camera 241. The fourth polarizer 242 is configured to filter out background light (i.e., background noise). In some embodiments, the fourth polarizer 242 includes a fourth half-wave plate and a fourth polarizing beam splitter PBS. By rotating the optical axis of the half-wave plate, the polarization direction of the linearly polarized light can be changed. By adjusting the half-wave plate, the background signal of the wafer obtained by the fourth detection channel 24 is maximized. When a scanning inspection is performed at this time, if a certain defect is detected to be more sensitive to the fourth detection channel 24, but cannot be detected by other channels, it can be identified as a pit-type defect.

[0124] In the embodiments disclosed herein, the first to fourth detection channels can be set individually or jointly to detect different types of defects. Therefore, in actual settings, the first detection channel 21 can be set alone without other detection channels; or the second detection channel 22 can be set alone without other detection channels; or the third detection channel 23 can be set alone without other detection channels; or the fourth detection channel 24 can be set alone without other detection channels; or the first detection channel 21 and the second detection channel 22 can be set without other detection channels; or the first detection channel 21 and the third detection channel 23 can be set without other detection channels; or the first detection channel 21 and the fourth detection channel can be set. 24. No other detection channels are set; or a second detection channel 22 and a third detection channel 23 are set, and no other detection channels are set; or a second detection channel 22 and a fourth detection channel 24 are set, and no other detection channels are set; or a third detection channel 22 and a fourth detection channel 23 are set, and no other detection channels are set; or a first detection channel 21, a second detection channel 22, and a third detection channel 23 are set, and a fourth detection channel 24 is not set; or a first detection channel 21, a second detection channel 22, and a fourth detection channel 24 are set, and a third detection channel 23 is not set; or a second detection channel 22, a third detection channel 23, and a fourth detection channel 24 are set, and a first detection channel 21 is not set. These combinations can be set according to the needs of actual applications. The setting method of each detection channel in each combination is similar to the setting method in Figure 5 and the related description, and will not be described in detail here. The detection module 4 can perform corresponding detection according to different setting methods. In some embodiments, the detection module 4 may include a controller and a signal processing unit. The controller can adjust one or more of the first to fourth detection channels. The controller can adjust the following aspects of one or more detection channels: 1. Adjusting the polarization state of the collected signal light by adjusting the half-wave plate and polarizer; 2. Switching the detection lenses of one or more detection channels to adjust the magnification and NA parameters of the detection lenses. The optical axis angle of the detection channel can be set in a fixed manner or in an adjustable manner. The controller can also adjust the tilt angle of the optical axis of the detection channel. The detection cameras in one or more of the first to fourth detection channels can convert the collected optical signals into electrical signals. The signal processing unit can be configured to obtain electrical signals from the detection cameras in one or more of the first to fourth detection channels and analyze the electrical signals. The signal processing unit can also be configured to control the controller.

[0125] In other embodiments, one or more detection channels each include a corresponding detection module, and each detection module includes a detection lens and a detection camera. The detection lens is used to collect the scattered light beam from the object to be detected and to image the object to be detected onto the detection camera.

[0126] In the embodiments disclosed herein, the detection camera may include, but is not limited to, a CCD detector, a TDI detector, a photomultiplier tube (PMT), an avalanche photodiode (APD), etc.

[0127] Referring to Figure 6, which is a schematic diagram illustrating how the second detection channel of this disclosure enhances the dynamic range of defect detection, the dynamic range of particle defects detected by the detection system can be expanded. In optical detection, the detectable dynamic range is determined by the lowest light intensity detectable by the detection channel and the number of electrons in the detector's full well. The lowest light intensity detectable by the detection channel is determined by multiple parameters, including shot noise, dark noise, background noise of the detection camera, and the signal-to-noise ratio threshold for defect detection. Since the first detection channel 21 detects linearly polarized light (P-light), the half-wave plate of the second detection channel 22 can be adjusted for linearly polarized light, thus adjusting the particle defect noise entering the detection channel within a certain range. In this case, the second PBS can act as an attenuator. Assuming the attenuation ratio is M1, the upper and lower limits of the defect signal range detectable by the second detection channel will be increased by M1 times compared to the first detection channel. As shown in the figure, combined with the defect size and particle defect scattering intensity curve, it can be observed that the detection dynamic range of the system can be expanded from A1-B1 to A1-B2. It is worth noting that A1~A2 and B1~B2 may or may not overlap, and the attenuation ratio needs to be selected according to the size distribution of defects on the wafer surface.

[0128] In some embodiments, when using one or more of the first to fourth detection channels for defect detection, since different detection channels can detect different types of defects, it is necessary to define the detection steps for different detection channels. Referring to Figure 7, the detection steps specifically include the following steps.

[0129] Step 1: Adjust one or more of the four imaging channels to achieve clear imaging, and remove the polarization separation module in the first detection channel 21. Obtain the signal intensity, where signal intensity Is refers to the sum of scattered light intensity from the defect in a defined collection channel. Subtract the corresponding noise intensity I from the signal intensity of all pixels occupied by the defect signal. haze The signal strength Is is calculated using the following formula.

[0130] 

[0131] The superimposed area is the entire pixel area occupied by the defect signal, I grayScaleis the signal intensity obtained by the detection module in this pixel region, I haze is the noise intensity generated by the substrate roughness of the wafer in this pixel region. The haze noise at different positions on the same wafer is mostly similar, I haze It can be the intensity of the detector at the defect-free position of the wafer, or it can be obtained by averaging the intensities of multiple defect-free position detectors.

[0132]  Step 2: Calculate the correlation coefficient. By comparing the detection conditions of each channel and identifying the detection conditions of different channels, the defect types can be identified. The defect types are judged by comparing the signal ratios of one or more channels from the first detection channel to the fourth detection channel. And calculate the channel intensity ratio K1, which satisfies K1 = (2*ISN) / (IS1+IS2-B), where ISN1 / IS1 / IS2 are the defect signal intensities detected by the fourth detection channel, the first detection channel, and the second detection channel respectively. B is a constant representing the energy difference of the dual-channel detection system, which is determined by the optical settings of the collection system.

[0133]  Step 3: Judge the defect type. Set a threshold A for defect type determination.. When K1>A, it is judged as a pit; when K1<A, it is judged as a protrusion; the range of the threshold A varies according to the system layout, for example, it varies between 1 and 5. For any dark-field detection system, the values of A and B can be determined by experimental calibration. The specific method is as follows: Prepare some samples with pit defects of different sizes and some samples with protrusion defects of different sizes, measure them respectively in this dark-field detection system, and then select the optimal values of A and B according to the measurement data. In addition, when it is judged as a protrusion, it can be judged whether it is a granular protrusion, a disc-shaped protrusion or a strip-shaped protrusion. Assume that the intensities of the first detection channel, the second detection channel, and the third detection channel are IS1 / IS2 / IS3 respectively, and let IS1 / (IS2 + IS3)=K2, IS2 / IS3=K3. When K2>C, it is judged as a granular protrusion, and at this time, a polarization separation module is added and adjusted to further reduce the background scattering noise. When K2<C, it is necessary to further judge K3. When K3>D, it is judged as a strip-shaped protrusion defect, otherwise it is judged as a disc defect. The thresholds A-D can all be further calibrated according to experiments. The detection flow chart is as shown in the figure.

[0134]  In this embodiment, by setting different first detection channels to fourth detection channels, various types of defects such as pits, strip-shaped and disc-shaped can be identified, which can improve the detection accuracy. The following specifically describes different usage combination examples.

[0135] In some embodiments of this disclosure, the first detection channel 21, the third detection channel 23, and the fourth detection channel 24 can be used, omitting the second detection channel 22 for detection. Referring to Figures 8A and 8B, Figure 8A is a side view showing the positional relationship between the first, third, and fourth detection channels and the wafer, and Figure 8B is a top view showing the positional relationship between the first, third, and fourth detection channels and the wafer in some embodiments of this disclosure. In these embodiments, the placement and tilt angle of the first detection channel 21, the third detection channel 23, and the fourth detection channel 24 are the same as in the previous embodiments. Specific details can be found in the above embodiments, but in these embodiments, the detector of the first detection channel 21 is extended by adding a fifth detection camera 214 after the first PBS 212 of the first detection channel 21. Referring to Figure 8C, Figure 8C is another schematic diagram of the structure of the first detection channel. In this way, the defect detection capabilities of the first detection channel 21 and the second detection channel 22 are integrated into the first detection channel 21. The first detection camera 213 is configured to detect particulate defects, and the fifth detection camera 214 is configured to detect elongated protruding defect signals.

[0136] When the illumination light is P-polarized, the fifth detection camera 214 can receive S-polarized light reflected by the first PBS 212. This S-polarized light includes scattered light from the elongated protruding defect and background scattered light. The polarization direction of the scattered light from the elongated protruding defect is the same as that of the background light, and it can be synchronously received by the fifth detection camera 214. The first detection camera 213 can receive P-polarized light transmitted by the first PBS 212, and can receive the scattered signal light from particle defects with a polarization direction perpendicular to the background light, achieving maximum background light separation and maximizing the signal-to-noise ratio for small-sized defects. Compared with Scheme 2, this scheme reduces one detection channel, effectively saving space. At this point, the detection effect of S-polarized light in the first detection channel 21 can replace the second detection channel 22, achieving the same detection of multiple defects. Compared to the previous embodiment that used a second detection channel located on the same plane as the direction of the first illumination light to detect elongated protruding defects, this scheme also uses the placement of the first detection channel for detecting elongated protruding defects. This allows for short-side tilting, making smaller depth of field and larger numerical aperture possible in optical design, effectively improving the collection angle of elongated protruding defects.

[0137] In the embodiments of this disclosure, the angle between the third projection of the optical axis of the third detection channel 23 onto the wafer surface and the major axis of the light spot ranges from 30 degrees to 60 degrees, and the angle with the minor axis of the light spot also ranges from 30 degrees to 60 degrees. The angle between the third projection of the optical axis of the third detection channel 23 onto the wafer surface and the projection of the path of the first illumination light onto the wafer surface ranges from -5 degrees to 5 degrees. In this case, the distances between the two endpoints of the major axis of the light spot and the optical axis of the third detection channel 23 are different, and the distances between the two endpoints of the minor axis of the light spot and the optical axis of the third detection channel 23 are also different. As described above, this arrangement will cause the image on the third detection camera 233 of the third detection channel 23 to be out of focus.

[0138] As shown in Figure 9, when the lens of the third detection channel 23 is tilted simultaneously in both the XZ and YZ planes, the imaging of the major and minor axes by the third detection channel 23 in both the XZ and YZ planes must satisfy the requirements of Scharm's Law. According to Scharm's Law, the angle between the optical axis of the detection channel lens and the axis of the illumination spot is θ, and the angle with the imaging plane of the camera is γ. The lens magnification is δ. The length of the illumination spot is on the order of mm. To ensure that the long side of the spot does not defocus, the optics must satisfy Scharm's Law: tanθ / tanγ = δ. When the optical axis of the third detection channel 23 is tilted, θ is not equal to γ. However, when the optical axis of the third detection channel 23 is tilted relative to the major axis of the spot and also tilted relative to the minor axis of the spot, Scharm's Law must be satisfied in both the XZ and YZ planes. That is, in the XZ plane, tanθ1 = δtanγ1 must be satisfied, and in the YZ plane, tanθ2 = δtanγ2 must be satisfied. θ1 is the angle between the projection of the optical axis of the third detection channel 23 in the XZ plane and the projection of the light spot in the XZ plane; γ1 is the angle between the projection of the optical axis of the third detection channel 23 in the XZ plane and the projection of the camera's image plane in the XZ plane; θ2 is the angle between the projection of the optical axis of the third detection channel 23 in the YZ plane and the projection of the light spot in the YZ plane; and γ2 is the angle between the projection of the optical axis of the third detection channel 23 in the YZ plane and the projection of the camera's image plane in the YZ plane. θ1 is not equal to γ1, and θ2 is not equal to γ2. With this setting, the tilt angles θ1 and θ2 of the detection camera can compensate to some extent for changes in the working distance (defocus) of the field of view outside the optical axis. Simultaneous tilting of the object and image achieves aberration compensation, eliminating defocus caused by different object distances in different fields of view. In practical use, it is necessary to adjust the astigmatism, coma, field curvature, and focal position of the third detection channel 23 according to the Schahm's Law, starting with a small tilt angle and gradually increasing it to the target angle. To eliminate defocus in both the major and minor axes caused by the tilt of the XZ plane and the simultaneous tilt of the XY plane of the optical axis, it is necessary to use aspherical and freeform lenses to ensure that the defocus in both directions can be corrected well.

[0139] In some embodiments of this disclosure, a first detection channel, a second detection channel, and a fourth detection channel may be used, while the third detection channel is omitted. In these embodiments, a second illumination component 3 is added. Referring to Figures 10A to 10F, Figure 10A is a side view showing the positional relationship of the second illumination component relative to the wafer in some embodiments of this disclosure, and Figure 10B is a top view showing the positional relationship of the second illumination component relative to the wafer in some embodiments of this disclosure. The tilt angle of the illumination light generated by the second illumination component 3 is the same as the tilt angle of the illumination light generated by the first illumination component 1. The incident surface of the illumination light from the second illumination component 3 is perpendicular to the surface of the wafer, and the line of intersection between the incident surface and the surface of the wafer is the same as the long axis of the focused light spot. The second illumination component 3 also includes a laser and a polarization structure. The laser and polarization structure of the second illumination component 3 may be the same as those of the first illumination component 1, i.e., the first laser 11 and the first polarization structure 12 of the first illumination component 1 may be reused. In other embodiments, the second illumination component 3 may include a separate laser and polarization structure. To save space, the second illumination component 3 can reuse the first laser and the first polarization structure of the first illumination component 1. In some embodiments, a beam splitting structure 35 can be used to obtain polarized light or unpolarized light with a P-polarization direction emitted from the first laser or the first polarization structure. The beam splitting structure 35 can be located on the light-emitting side of the first laser 11. When the first illumination component 1 is provided with a first polarization structure, the beam splitting device can be located on the light-emitting side of the first polarization structure.

[0140] The second illumination component 3 requires an independent design of a freeform surface focusing lens. Specifically, the second illumination component 3 includes a second shaper 33 and a second reflector 34. The second shaper 33 may include a freeform surface refractive lens, which precisely controls the light refraction path through local curvature changes. Based on Snell's law and the law of conservation of energy, it redistributes the P-polarized light obtained from the first polarization structure 12 to form a target light spot with a specific shape (major axis length: minor axis length > 2, such as a rectangle or ellipse) or uniformity > 90%. The polarization direction of the second illumination light is the same as that of the first illumination light, and its polarization direction is perpendicular to the plane formed by the path of the second illumination light and the projection of the second illumination light path onto the wafer.

[0141] The second reflector 34 is configured to direct the light emitted from the second shaper 33 onto the surface of the wafer at a second incident angle, forming a second light spot, which is a rectangular line spot. The second incident angle is the angle between the path of the second illumination light and the surface of the wafer, and the second incident angle may be the same as or different from the first incident angle. The range of the second incident angle can be 60 degrees to 80 degrees, for example, 70 degrees. The size, position, and intensity distribution of the second light spot are exactly the same as those of the first light spot.

[0142] In these embodiments, the arrangement of the first, second, and fourth detection channels is the same as that in the embodiments described above. Referring to Figures 10C-10D, Figure 10C is a top view showing the positional relationship of the detection channels relative to the wafer when illuminated using the first illumination component 1, and Figure 10D is a side view showing the positional relationship of the detection channels relative to the wafer when illuminated using the first illumination component. Similar to the previous embodiments, the first detection channel 21 can detect particle defects. The fourth detection channel 24 can detect pit defects. The second detection channel can detect elongated protrusion defects. The detection method is the same as in the embodiments described above; for details, please refer to the embodiments described above, which will not be described in detail here.

[0143] Referring to Figures 10E-10F, Figure 10E is a top view showing the positional relationship of the detection channel relative to the wafer when the second illumination component is used for illumination, and Figure 10F is a side view showing the positional relationship of the detection channel relative to the wafer when the second illumination component is used for illumination. When the second illumination component 2 is used for illumination, the position of the second detection channel 22 is exactly in front of the illumination light from the second illumination component 3, making it more sensitive to disk-type defects and enabling the detection of disk-type defects. In this case, the second illumination component 22 can be used in conjunction with the fourth detection channel 24, replacing the use of the third detection channel 23.

[0144] This scheme increases the number of optical paths in the illumination assembly and reduces the number of detection channels, achieving the detection of four defect types using three detection channels. Because the polarization elements, high-quality imaging lenses, and high-speed wide-field cameras in the detection channels are expensive, it can reduce the manufacturing cost of the optical system to some extent, and also save space by increasing the lens aperture.

[0145] The embodiments of this disclosure also provide a wafer inspection apparatus. The wafer inspection apparatus includes a first illumination component 1 configured to generate a first illumination light and irradiate the first illumination light onto the surface of a wafer at a first incident angle to form a first light spot; one or more detection channels configured to detect scattered light from the surface of the wafer on the one or more detection channels, wherein the optical axis of the first detection channel in the one or more detection channels has a first angle between a first projection on the surface of the wafer and a first illumination light path projection on the surface of the wafer, the first angle being in the range of 35 degrees to 55 degrees, for example 45 degrees, wherein at least one of the one or more detection channels uses a polarization component to filter out background light to obtain signal light indicating defects in the wafer; and a detection module 4 configured to receive the signal light to detect defects in the wafer.

[0146] Optionally, the first detection channel is located on the first side of the first light spot, and the incident direction of the first illumination light is located on the second side of the first light spot, with the first side and the second side opposite to each other.

[0147] In some embodiments, the first light spot is a rectangular light spot. A second angle is formed between the projection of the first illumination light path onto the surface of the wafer and the first axis of the first light spot, the second angle ranging from 30 degrees to 60 degrees. The optical axis of the first detection channel forms a third angle between the first projection onto the surface of the wafer and the first axis of the first light spot, the third angle ranging from 85 degrees to 95 degrees. The first axis is the long axis of symmetry of the first light spot. The first polarization direction is perpendicular to the first plane formed by the path of the first illumination light and the projection of the first illumination light path.

[0148] In some embodiments, the first illumination light includes a component with a first polarization direction, the first polarization direction being perpendicular to the path of the first illumination light on the surface of the wafer, and the first plane formed by the projection of the first illumination light path onto the surface of the wafer and the path of the first illumination light.

[0149] In some embodiments, each of at least one of the detection channels includes a half-wave plate and a polarizing beam splitter (PBS), and the detection device 4 is further configured to: rotate the optical axis of the half-wave plate in each of the at least one detection channel to change the background light into linearly polarized light with a second polarization direction, wherein the second polarization direction is perpendicular to the first polarization direction; and filter out the linearly polarized light using the polarizing beam splitter (PBS).

[0150] In some embodiments, one or more detection channels further include one or more of a second detection channel 22, a third detection channel 23, and a fourth detection channel 24; the angle between the first projection of the optical axis of the first detection channel 21 onto the surface of the wafer and the fourth projection of the optical axis of the fourth detection channel 24 onto the surface of the wafer is between -5 degrees and +5 degrees; the angle between the second projection of the optical axis of the second detection channel 22 onto the surface of the wafer and the first axis of the first light spot is between -5 degrees and +5 degrees; the angle between the third projection of the optical axis of the third detection channel 23 onto the surface of the wafer and the projection of the path of the first illumination light onto the surface of the wafer is between -5 degrees and +5 degrees.

[0151] Optionally, the optical axis of the first detection channel 21 and the optical axis of the fourth detection channel 24 are located in the same second plane; the optical axis of the second detection channel 22 is located in a third plane perpendicular to the second plane; and the optical axis of the third detection channel 23 is located in the same first plane as the path of the first illumination light.

[0152] In some embodiments, each of the first detection channel 21, the second detection channel 22, the third detection channel 23, and the fourth detection channel 24 includes a detection lens and a detection camera. The optical axis of the detection lens 211 of the first detection channel 21, the second axis of the first light spot, and the optical axis of the detection camera 213 of the first detection channel 21 are arranged in the same plane; the optical axis of the detection lens 221 of the second detection channel 22, the first axis of the first light spot, and the optical axis of the detection camera 213 of the second detection channel 22 are arranged in the same plane; the optical axis of the detection lens 231 of the third detection channel 23, the path of the first illumination light, and the optical axis of the detection camera 233 of the third detection channel 23 are arranged in the same plane; the optical axis of the detection lens 241 of the fourth detection channel 24, the second axis of the first light spot, and the optical axis of the detection camera 243 of the fourth detection channel 24 are arranged in the same plane, wherein the first axis is perpendicular to the second axis. In some embodiments, when the first light spot is a linear rectangular light spot, the first axis may be the major axis of the rectangular light spot, and the second light spot may be the minor axis of the rectangular light spot.

[0153] In some embodiments, the wafer inspection apparatus of this disclosure further includes a second illumination component 3, configured to: generate a second illumination light; and irradiate the wafer with the second illumination light at a second incident angle to form a second light spot, wherein one or more of the size, position, and intensity distribution of the second light spot are the same as the size, position, and intensity distribution of the first light spot, and the projection of the second illumination light path on the surface of the wafer is the same as the first axis of the first light spot. The detection module 4 is further configured to detect the scattered light of the second light spot on one or more of the first detection channel 21, the second detection channel 22, and the fourth detection channel 24.

[0154] In some embodiments, the detection module 4 is further configured to: adjust one or more detection channels from the first detection channel to the fourth detection channel to achieve clear imaging; acquire the signal intensity Is of one or more detection channels from the first detection channel to the fourth detection channel, wherein the signal intensity Is is the sum of the scattered light intensity collected by each detection channel; and determine the defect type by comparing the signal intensity Is of one or more detection channels from the first detection channel to the fourth detection channel.

[0155] Some embodiments of this disclosure also provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, can implement the steps of the method for detecting wafer defects provided in some embodiments of this disclosure.

[0156] In the embodiments provided in this application, it should be understood that the disclosed methods and apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0157] Furthermore, the detection module 4 in the various embodiments of this disclosure can be integrated into one processing unit, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0158] The integrated units implemented as software functional units described above can be stored in a computer-readable storage medium. These software functional units, stored in a storage medium, include several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute some steps of the transmission and reception methods described in the various embodiments of this disclosure. The aforementioned storage medium can be a volatile or non-volatile computer-readable storage medium, including: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.

[0159] It is understood that the detection module 4 in the embodiments described in this disclosure can be implemented using hardware, software, firmware, middleware, microcode, or a combination thereof. For hardware implementation, modules, units, submodules, subunits, etc., can be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), general-purpose processors, controllers, microcontrollers, microprocessors, other electronic units for performing the functions described in this disclosure, or combinations thereof.

[0160] The above descriptions are some embodiments of this disclosure. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles described in this disclosure, and these improvements and modifications should also be considered within the scope of protection of this disclosure.

Claims

1. A wafer inspection method, comprising: Generate the first illumination light; The first illumination light is shone onto the surface of the wafer to form a first light spot; Scattered light from the surface of the wafer is detected on one or more detection channels, wherein the optical axis of the first detection channel of the one or more detection channels has a first angle between a first projection of the first illumination light onto the surface of the wafer and a first illumination light path projection of the first illumination light onto the surface of the wafer, the first angle being in the range of 35 degrees to 55 degrees, wherein at least one of the one or more detection channels uses a polarization component to filter out background light from the scattered light to obtain signal light of defects in the wafer. The detection module receives the signal light to detect defects in the wafer.

2. The wafer inspection method of claim 1, wherein The first detection channel is located on the first side of the first light spot, and the incident direction of the first illumination light is located on the second side of the first light spot, with the first side and the second side being opposite to each other.

3. The wafer inspection method of claim 2, wherein The first light spot is a rectangular light spot, and the projection of the first illumination light onto the surface of the wafer via the first illumination light path forms a second angle between the first illumination light and the first axis of the first light spot, the second angle being in the range of 30 degrees to 60 degrees. The optical axis of the first detection channel forms a third angle between the first projection on the surface of the wafer and the first axis of the first light spot, the third angle being in the range of 85 degrees to 95 degrees.

4. The wafer inspection method according to claim 3, wherein, The first axis is the major axis of the first light spot, the first angle and the second angle are 45 degrees, and the third angle is 90 degrees.

5. The wafer inspection method according to any one of claims 1 to 4, wherein, The first illumination light includes a component with a first polarization direction, the first polarization direction being perpendicular to the path of the first illumination light on the surface of the wafer, the projection of the first illumination light path onto the surface of the wafer, and the first illumination light path forming a first plane.

6. The wafer inspection method according to claim 5, wherein each of at least one of the one or more detection channels comprises a half-wave plate and a polarizing beam splitter (PBS). The process of probing the scattered light from the surface of the wafer on one or more probe channels includes: Rotate the optical axis of the half-wave plate in each of the at least one detection channel to change the background light into linearly polarized light with a second polarization direction, wherein the second polarization direction is perpendicular to the first polarization direction; The polarizing beam splitter PBS is used to filter linearly polarized light in the second polarization direction.

7. The wafer inspection method according to any one of claims 1 to 4, wherein, The one or more detection channels further include one or more of a second detection channel, a third detection channel, and a fourth detection channel; The angle between the first projection of the optical axis of the first detection channel onto the surface of the wafer and the fourth projection of the optical axis of the fourth detection channel onto the surface of the wafer is between -5 degrees and +5 degrees. The second projection of the optical axis of the second detection channel onto the surface of the wafer lies at an angle between -5 degrees and +5 degrees with the first axis of the first light spot. The angle between the third projection of the optical axis of the third detection channel onto the surface of the wafer and the projection of the path of the first illumination light onto the surface of the wafer is between -5 degrees and +5 degrees.

8. The wafer inspection method according to claim 7, wherein, Each of the first detection channel, the second detection channel, the third detection channel, and the fourth detection channel includes a detection lens and a detection camera. The method further includes one or more of the following steps: The optical axis of the detection lens of the first detection channel, the second axis of the first light spot, and the optical axis of the detection camera of the first detection channel are set in the second plane; The optical axis of the detection lens of the second detection channel, the first axis of the first light spot, and the optical axis of the detection camera of the second detection channel are set in the third plane; The optical axis of the detection lens of the third detection channel, the path of the first illumination light, and the optical axis of the detection camera of the third detection channel are set in the first plane; The optical axis of the detection lens of the fourth detection channel, the second axis of the first light spot, and the optical axis of the detection camera of the fourth detection channel are arranged in the second plane. The first axis is perpendicular to the second axis.

9. The wafer inspection method according to claim 7 further includes: Generate a second illumination light; The second illumination light is irradiated onto the surface of the wafer to form a second light spot. One or more of the size, position, and intensity distribution of the second light spot are the same as one or more of the size, position, and intensity distribution of the first light spot. The projection of the second illumination light path on the surface of the wafer is the same as the first axis of the first light spot. The scattered light of the second spot is detected on one or more of the first detection channel, the second detection channel, and the fourth detection channel.

10. The wafer inspection method according to claim 7, wherein, The method further includes: Adjust one or more of the first detection channel to the fourth detection channel until a clear image is formed; The signal intensity Is of one or more detection channels from the first detection channel to the fourth detection channel is obtained, wherein the signal intensity Is is the sum of the scattered light intensity collected by each detection channel; The defect type is determined by comparing the signal strength Is of one or more of the first to fourth detection channels.

11. A wafer inspection device, comprising: A first illumination component is configured to generate a first illumination light and to illuminate the surface of the wafer to form a first light spot. One or more detection channels are configured to detect scattered light from the surface of the wafer on one or more detection channels, wherein the optical axis of a first detection channel in the one or more detection channels has a first angle between a first projection of the optical axis onto the surface of the wafer and a first illumination path projection of the first illumination light onto the surface of the wafer, the first angle being in the range of 35 degrees to 55 degrees, wherein at least one of the one or more detection channels uses a polarization component to filter out background light from the scattered light to obtain signal light of defects in the wafer; The detection module is configured to receive the signal light to detect defects in the wafer.

12. The wafer inspection apparatus according to claim 11, wherein, The first detection channel is located on the first side of the first light spot, and the incident direction of the first illumination light is located on the second side of the first light spot, with the first side and the second side being opposite to each other.

13. The wafer inspection apparatus according to claim 12, wherein, The first light spot is a rectangular light spot, and the projection of the first illumination light onto the surface of the wafer via the first illumination light path forms a second angle between the first illumination light and the first axis of the first light spot, the second angle being in the range of 30 degrees to 60 degrees. The optical axis of the first detection channel forms a third angle between the first projection on the surface of the wafer and the first axis of the first light spot, the third angle being in the range of 85 degrees to 95 degrees.

14. The wafer inspection apparatus according to claim 13, wherein, The first axis is the major axis of the first light spot, the first angle and the second angle are 45 degrees, and the third angle is 90 degrees.

15. The wafer inspection apparatus according to any one of claims 11 to 14, wherein, The first illumination light includes a component with a first polarization direction, the first polarization direction being perpendicular to the path of the first illumination light on the surface of the wafer, the projection of the first illumination light path onto the surface of the wafer, and the first illumination light path forming a first plane.

16. The wafer inspection apparatus of claim 15, wherein each of at least one of the one or more detection channels comprises a half-wave plate and a polarizing beam splitter (PBS). The detection device is further configured to: rotate the optical axis of the half-wave plate in each of the at least one detection channel to change the background light into linearly polarized light with the polarization direction of the second polarization direction, wherein the second polarization direction is perpendicular to the first polarization direction; and filter out the linearly polarized light using the polarizing beam splitter PBS.

17. The wafer inspection apparatus according to any one of claims 11 to 14, wherein, The one or more detection channels further include one or more of a second detection channel, a third detection channel, and a fourth detection channel; The angle between the first projection of the optical axis of the first detection channel onto the surface of the wafer and the fourth projection of the optical axis of the fourth detection channel onto the surface of the wafer is between -5 degrees and +5 degrees. The second projection of the optical axis of the second detection channel onto the surface of the wafer lies at an angle between -5 degrees and +5 degrees with the first axis of the first light spot. The angle between the third projection of the optical axis of the third detection channel onto the surface of the wafer and the projection of the path of the first illumination light onto the surface of the wafer is between -5 degrees and +5 degrees.

18. The wafer inspection apparatus according to claim 17, wherein, Each of the first, second, third, and fourth detection channels includes a detection lens and a detection camera. The optical axis of the detection lens of the first detection channel, the second axis of the first light spot, and the optical axis of the detection camera of the first detection channel are arranged in the second plane; The optical axis of the detection lens of the second detection channel, the first axis of the first light spot, and the optical axis of the detection camera of the second detection channel are arranged in the third plane; The optical axis of the detection lens of the third detection channel, the path of the first illumination light, and the optical axis of the detection camera of the third detection channel are arranged in the first plane. The optical axis of the detection lens of the fourth detection channel, the second axis of the first light spot, and the optical axis of the detection camera of the fourth detection channel are arranged in the second plane. The first axis is perpendicular to the second axis.

19. The wafer inspection apparatus according to claim 17, further comprising: A second illumination component is configured to generate a second illumination light, which illuminates the surface of the wafer to form a second light spot. One or more of the size, position, and intensity distribution of the second light spot are the same as one or more of the size, position, and intensity distribution of the first light spot. The path of the second illumination light on the surface of the wafer is projected onto the same first axis as the first light spot. The detection module is further configured to detect the scattered light of the second spot on one or more of the first detection channel, the second detection channel, and the fourth detection channel.

20. The wafer inspection apparatus according to claim 17, wherein, The detection module is further configured as follows: Adjust one or more of the first detection channel to the fourth detection channel until a clear image is formed; The signal intensity Is of one or more detection channels from the first detection channel to the fourth detection channel is obtained, wherein the signal intensity Is is the sum of the scattered light intensity collected by each detection channel; The defect type is determined by comparing the signal strength Is of one or more of the first to fourth detection channels.

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