A defect detection apparatus and method

Abstract

The application discloses a kind of defect detection device and method.The defect detection device includes: object plane, off-axis illumination module, imaging module and analysis processing module.The object plane is used to carry the object to be measured.The off-axis illumination module is used to generate and emit off-axis illumination beam.The imaging module is used to form the imaging light beam according to the off-axis illumination beam after the surface to be detected of the object to be measured is reflected, and the surface to be detected is imaged to generate image signal, wherein the included angle between the chief ray of the off-axis illumination beam and the axis of the imaging module is not 0.The analysis processing module is connected with the imaging module, and is used to identify the defect area of the surface to be detected according to the image signal.The present application increases the imaging brightness difference between different inclinations on the surface to be detected, facilitates the identification of shallow defects, and improves the detection accuracy.

Description

Technical Field

[0001] The present invention relates to the field of optical inspection technology, and in particular to a defect detection device and method. Background Technology

[0002] As the substrate for integrated circuits, silicon wafers play a crucial role in semiconductor manufacturing. However, the production process of silicon wafers involves numerous steps such as etching, back sealing, polishing, and epitaxy, which can easily introduce defects onto the wafer surface. To strictly control wafer quality, manufacturers must perform defect detection on the surface of silicon wafers.

[0003] Automated Optical Inspection (AOI) equipment has become the most popular silicon wafer defect inspection device due to its fast and accurate defect identification and location capabilities. Existing AOIs include illumination elements, imaging elements, and analysis and processing elements. The illumination element provides radiant light, the imaging element converts the light signal reflected from the surface to be inspected into a digital electrical signal, and the analysis and processing element identifies defects on the surface to be inspected based on the digital electrical signal.

[0004] However, existing AOIs cannot identify shallower defects, resulting in poor detection accuracy. Summary of the Invention

[0005] This invention provides a defect detection device and method to identify defects with shallow depths, such as orange peel defects, thereby improving detection accuracy.

[0006] In a first aspect, embodiments of the present invention provide a defect detection device, which includes: a loading plane, an off-axis illumination module, an imaging module, and an analysis and processing module;

[0007] The loading plane is used to support the object to be measured;

[0008] The off-axis illumination module is used to generate and emit off-axis illumination beams;

[0009] The imaging module is used to image the surface to be tested based on the imaging beam formed by the reflection of the off-axis illumination beam by the surface to be tested of the object under test, so as to generate an image signal, wherein the angle between the principal ray of the off-axis illumination beam and the axis of the imaging module is not 0.

[0010] The analysis and processing module is connected to the imaging module and is used to identify the defect area of ​​the surface to be inspected based on the image signal.

[0011] Optionally, the imaging module includes: an objective lens and a camera;

[0012] The objective lens is disposed between the object-carrying plane and the camera, and is used to collect the imaging beam formed by the detection beam after being reflected or scattered by the surface to be detected;

[0013] The camera is used to image the surface to be detected based on the imaging beam, and generate the image signal.

[0014] Optionally, the off-axis illumination module includes: a light-emitting unit, an aperture stop, a first condenser lens, and a beam splitter;

[0015] The light-emitting unit is used to generate and emit a light source;

[0016] The aperture stop is off-axis and is used to generate the off-axis illumination beam according to the light source.

[0017] The first condenser lens is disposed in the optical path of the off-axis illumination beam, and the first condenser lens is used to focus the off-axis illumination beam.

[0018] The beam splitter is disposed between the objective lens and the camera. The off-axis illumination beam is reflected by the beam splitter, enters the objective lens, and illuminates the surface to be inspected. The angle between the principal ray of the off-axis illumination beam reflected by the beam splitter and the axis of the objective lens is not 0.

[0019] Optionally, the off-axis illumination module further includes: a second condenser lens;

[0020] The second condensing lens is disposed between the light-emitting unit and the aperture stop, and the second condensing lens is used to concentrate the light source.

[0021] Optionally, the off-axis illumination module further includes a reflector, which is disposed between the first condenser and the beam splitter, and is used to reflect the off-axis illumination beam onto the beam splitter.

[0022] Optionally, the light-transmitting hole of the aperture stop may be circular, elliptical, annular, rectangular, or irregular in shape.

[0023] Optionally, the ratio of the light-transmitting aperture area of ​​the aperture stop to the aperture area of ​​the objective lens is within a first range, wherein the first range is 0.1 to 0.3.

[0024] Secondly, embodiments of the present invention also provide a defect detection method, which is implemented using any of the defect detection devices described in the first aspect, the defect detection method comprising:

[0025] The off-axis illumination module generates and emits an off-axis illumination beam.

[0026] The imaging module images the surface to be detected based on the imaging beam formed by the reflection of the off-axis illumination beam after it is reflected by the surface to be detected, so as to generate an image signal. The angle between the principal ray of the off-axis illumination beam and the axis of the imaging module is not 0.

[0027] The analysis and processing module identifies the defect area of ​​the surface to be inspected based on the image signal.

[0028] Optionally, the imaging module images the surface to be detected based on the imaging beam formed by the reflection of the off-axis illumination beam after passing through the surface to be detected, in order to generate an image signal, including:

[0029] The objective lens collects the imaging beam formed by the reflection or scattering of the detection beam by the surface to be detected;

[0030] The camera images the surface to be detected based on the imaging beam, generating the image signal.

[0031] Optionally, the off-axis illumination module generates and emits an off-axis illumination beam, including:

[0032] The light-emitting unit generates and emits a light source;

[0033] The aperture stop generates the off-axis illumination beam according to the light source;

[0034] The first condenser lens focuses the off-axis illumination beam;

[0035] The beam splitter reflects the off-axis illumination beam after it has been focused, allowing the off-axis illumination beam to enter the objective lens and illuminate the surface to be inspected.

[0036] The defect detection device and method provided in this embodiment include a carrying plane, an off-axis illumination module, an imaging module, and an analysis and processing module. The off-axis illumination module generates and emits an off-axis illumination beam. The imaging module images the surface to be tested based on the imaging beam formed by the reflection of the off-axis illumination beam from the surface to be tested, generating an image signal. The angle between the principal ray of the off-axis illumination beam and the axis of the imaging module is not zero. The analysis and processing module is connected to the imaging module and identifies defect areas on the surface to be tested based on the image signal, thus achieving defect detection of the object under test. Because there is an angle between the principal ray of the off-axis illumination beam and the axis of the imaging module, the off-axis illumination ray reflected from the inclined area has a larger tilt angle with the axis, preventing more light from entering the imaging module to participate in imaging. This increases the brightness difference between different tilt angles, facilitating the identification of shallow defects and improving detection accuracy. Attached Figure Description

[0037] Figure 1This is a schematic diagram illustrating the defect detection principle of an automated optical inspection device in the prior art;

[0038] Figure 2 This is a schematic diagram of an orange peel defect in the prior art;

[0039] Figure 3 This is a schematic diagram illustrating the orange peel defect detection principle of an automated optical inspection device in the prior art;

[0040] Figure 4 This is a schematic diagram of the structure of a defect detection device provided in an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of another defect detection device provided in an embodiment of the present invention;

[0042] Figure 6 This is a schematic diagram of the structure of another defect detection device provided in an embodiment of the present invention;

[0043] Figure 7 A schematic diagram comparing the aperture range of an aperture stop and an objective lens, provided for an embodiment of the present invention;

[0044] Figure 8 A schematic diagram illustrating the aperture range, off-axis illumination beam distribution range, and reflected light angular distribution range of an objective lens provided for an embodiment of the present invention;

[0045] Figure 9 This is a schematic diagram of the structure of another defect detection device provided in an embodiment of the present invention;

[0046] Figure 10 An imaging effect diagram of a surface to be detected provided in an embodiment of the present invention;

[0047] Figure 11 This is a flowchart illustrating a defect detection method provided in an embodiment of the present invention;

[0048] Figure 12 This is a flowchart illustrating another defect detection method provided in an embodiment of the present invention. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0050] As described in the background art, refer to Figure 1Existing AOI (Automated Optical Inspection) systems include an illumination element (not shown in the figure), an imaging element 101, and an analysis and processing element 102. The illumination element provides radiant light, the imaging element 101 converts the light signal reflected from the surface 103 to be inspected into a digital electrical signal, and the analysis and processing element 102 identifies defects on the surface 103 based on the digital electrical signal. The inventors discovered that the detection principle of this AOI utilizes the light absorption or scattering at the defect location 104 to identify defects. The surface 103 of the smooth silicon wafer to be inspected can be considered a mirror. Illumination light incident on it undergoes specular reflection, and all reflected light enters the imaging element 101 and is ultimately imaged on the image sensor within the imaging element, forming a bright background. However, at the defect location 104, due to surface unevenness or contamination, light is scattered or absorbed at a large angle, and only a portion of the reflected light enters the imaging element 101 and participates in imaging, forming a dark image at the corresponding position on the image sensor. The analysis and processing element 102 can detect defects by observing the different electrical signals at different positions on the image sensor. AOI (Automated Optical Inspection) is a good detection method for defects with strong scattering effects, such as scratches, dust, and pitting, as well as defects with strong absorption effects, such as dirt.

[0051] Reference Figure 2 Orange peel defect 200 is an uneven defect formed on the surface 103 to be inspected after polishing. Its lateral scale L is generally on the micrometer level, and its depth H is on the nanometer level. The uneven surface is relatively smooth, and the scattering and absorption effects are very weak. Most of the light incident on the surface is reflected. The slope angle δ is different at different locations of the defect, and the angle of the reflected light is related to the slope angle δ of the defect. For example, point A is a reflection point on a flat position on the surface to be inspected. Light rays perpendicular to the plane of the object are incident on point A, and the reflected light rays can return along the same path after reflection at point A. Point B is a reflection point on the surface to be inspected where there is an orange peel defect. Light rays perpendicular to the plane of the object are incident on point B, and the reflected light rays cannot return along the same path after reflection at point B, and will be deflected at a certain angle. The slope angle δ at point A is the smallest, which is 0°, and the slope angle δ at point B is the largest, which is generally less than 0.1°. Figure 2 and Figure 3 When using existing AOI equipment to detect orange peel defects 200, the principal ray of the radiation light is incident perpendicularly to the surface to be inspected 103. The orange peel defects 200 are located at different positions ( Figure 3(Only the reflected light at point B is shown.) All reflected light is reflected from the incident radiation. At point A, the reflected light can return along the same path and enter the imaging element 101 to participate in imaging. At point B, the reflected light deviates from the incident light at the largest angle, causing some of the reflected light to fall outside the maximum aperture angle range 2α that the imaging element 101 can collect, and thus cannot participate in imaging. Since the light beam provided by the illumination element is uniform, the incident light energy provided by the illumination element to points A and B is equal, both being η1. The reflected light energy retained at point A within the maximum aperture angle range 2α of the imaging element 101 is the largest, equal to η1. The reflected light energy retained at point B within the maximum aperture angle range 2α of the imaging element 101 is the smallest, η2, where η1 > η2. The signal intensity generated by the photosensitive chip in the imaging element receiving the reflected light from point A is S1, and the signal intensity generated by receiving the reflected light from point B is S2. S is proportional to η, so S1 > S2. When the difference between S1 and S2 is too small, the imaging element 101 cannot distinguish the difference between S1 and S2 when converting the analog signal to a digital signal. This results in the entire defect area having the same gray value in the image. Consequently, the analysis and processing element 102 cannot distinguish the defect. Therefore, existing AOI equipment cannot detect shallow defect types like orange peel defects, resulting in poor detection accuracy.

[0052] To address the aforementioned problems, this invention provides a defect detection device. Figure 4 This is a schematic diagram of a defect detection device provided in an embodiment of the present invention, with reference to... Figure 4 The defect detection device 400 includes: a loading plane 401, an off-axis illumination module ( Figure 4 (Not shown in the diagram) An imaging module 402 and an analysis and processing module 403. A carrying plane 401 is used to support the object to be tested 404. An off-axis illumination module is used to generate and emit an off-axis illumination beam. The imaging module 402 is used to image the surface to be tested based on the imaging beam formed by the reflection of the off-axis illumination beam from the surface to be tested, thereby generating an image signal. The angle θ1 between the principal ray of the off-axis illumination beam and the axis O of the imaging module 402 is not 0. The analysis and processing module 403 is connected to the imaging module 402 and is used to identify defect areas on the surface to be tested based on the image signal.

[0053] The off-axis illumination module refers to an illumination component capable of generating an off-axis illumination beam, which can be an optical system component including a light source and an off-axis lens group. The off-axis illumination beam is an illumination beam whose principal ray is not parallel to the axis O of the imaging module 402. Since the axis O of the imaging module 402 is perpendicular to the object plane 401, the incident angle of the principal ray of the off-axis illumination beam onto the object plane 401 is not equal to 90°. The imaging module 402 refers to an imaging component capable of imaging the surface to be tested based on the imaging beam. Exemplarily, the imaging module 402 can include at least a high-magnification microscope objective and a camera. The high-magnification microscope objective is a lens group positioned between the camera and the object to be tested 404, capable of collecting and refracting light, and can form a real image of the object to be tested 404 on the camera's photosensitive element. The camera can image the object to be tested 404 on the photosensitive element and generate corresponding analog electrical signals based on the imaging results, which are then converted into image signals in the form of digital electrical signals. The analysis and processing module 403 refers to a data processing device that analyzes and processes graphic signals, and can identify defects on the surface to be inspected based on the image signals.

[0054] Specifically, the off-axis illumination module emits an off-axis illumination beam, and the angle θ1 between the off-axis illumination beam and the axis O of the imaging module 402 is not zero. When the off-axis illumination beam illuminates the surface to be inspected, reflection or scattering occurs. A portion of the off-axis illumination beam, after being reflected from a relatively flat position on the surface, can completely serve as the imaging beam, entering the imaging module 402 and participating in imaging, resulting in high brightness at that position. However, another portion of the off-axis illumination beam, after being reflected from a position with a steep slope, experiences a significant angular deflection relative to the original incident light. Some of this deflection exceeds the maximum aperture angle range collected by the imaging element, and the remaining light serves as the imaging beam entering the imaging module 402, resulting in lower brightness at that position. The angle θ1 between the principal ray of the off-axis illumination beam and the axis O of the imaging module 402 is not zero. Compared to the illumination beam in the prior art where the main ray is parallel to the axis O of the imaging module 402, the off-axis illumination beam can obtain more offset (relative to the axis O of the imaging module 402) reflected light in areas with large slopes. As a result, the light reflected in areas with large slopes can be offset more from the imaging module 402, reducing the participation of light reflected in areas with large slopes in imaging, thereby increasing the grayscale difference between flat areas and slopes during imaging.

[0055] Combination Figure 2 and Figure 4For example, the angle between the principal ray of the off-axis illumination beam and the axis O of the imaging module 402 is θ1, the illumination angle range of the off-axis illumination beam at point A is θ2, and the maximum aperture angle range that the imaging module 402 can collect is 2α. The off-axis illumination beam illuminates point A, and the incident light energy of the off-axis illumination beam at point A is equal to η1'. The reflected light generated by the off-axis illumination beam at point A is all within the maximum aperture angle range of 2α of the imaging module 402, that is, all the reflected light generated by the off-axis illumination beam at point A can be used as the imaging beam φ1( Figure 4 (Only three rays are shown for illustration) enter the imaging module 402 to participate in the imaging of point A. The energy of the imaging beam φ1 is equal to η1' (ignoring transmission losses). In the imaging module 402, the camera's image sensor can generate a corresponding analog electrical signal based on the energy value η1' of the imaging beam φ1 at point A. The signal strength of the analog electrical signal (e.g., the signal strength can be expressed as a voltage or current value) is S1', where the signal strength of the analog electrical signal is positively correlated with the energy of the imaging beam. The analog electrical signal corresponding to point A is then converted into a digital electrical signal form of the point A image signal.

[0056] Figure 5 This is a schematic diagram of another defect detection device provided in an embodiment of the present invention, combined with... Figure 2 and Figure 5 For example, the angle between the principal ray of the off-axis illumination beam and the axis O of the imaging module 402 is θ1, the illumination angle range of the off-axis illumination beam at point B is θ2, and the maximum aperture angle range that the imaging module 402 can collect is 2α. The off-axis illumination beam illuminates point B, and the incident light energy of the off-axis illumination beam at point B is equal to η2'. Of the reflected light generated by the off-axis illumination beam at point B, only a portion is within the maximum aperture angle range of 2α of the imaging module 402, that is, only a portion of the reflected light generated by the off-axis illumination beam at point B can be used as the imaging beam φ2( Figure 5(Only two rays are shown for illustration) enter the imaging module 402 to participate in the imaging of point B. The energy of the imaging beam φ2 is less than η2' (ignoring transmission losses). Another portion of the reflected rays from the off-axis illumination beam at point B is outside the maximum aperture angle range 2α of the imaging module 402 and cannot enter it. In the imaging module 402, the camera's image sensor generates a corresponding analog electrical signal based on the energy value η2' of the imaging beam φ2 at point B. The signal strength of the analog electrical signal (e.g., the signal strength can be expressed as a voltage or current value) is S2', where the signal strength of the analog electrical signal is positively correlated with the energy of the imaging beam. The analog electrical signal is then converted into a digital image signal. The angle between the principal ray of the off-axis illumination beam and the axis O of the imaging module 402 is θ1. Since the principal ray is not parallel to the axis O of the imaging module 402, the deflection angle between the reflected ray at point B and the axis O increases. This prevents more light from entering the imaging module 402 to participate in the imaging of point B, thus increasing the difference between the signal intensity S2' of the analog signal at point B and the signal intensity S1' of the analog signal at point A. During analog-to-digital conversion by the camera, this ensures that the grayscale values ​​of points A and B differ by at least one gray level, allowing the analysis and processing module 403 to distinguish them.

[0057] The defect detection device provided in this embodiment includes a carrying plane, an off-axis illumination module, an imaging module, and an analysis and processing module. The off-axis illumination module generates and emits an off-axis illumination beam. The imaging module images the surface to be tested based on the imaging beam formed by the reflection of the off-axis illumination beam from the surface to be tested, generating an image signal. The angle between the principal ray of the off-axis illumination beam and the axis of the imaging module is not zero. The analysis and processing module is connected to the imaging module and identifies defect areas on the surface to be tested based on the image signal, thus achieving defect detection of the object under test. Because there is an angle between the principal ray of the off-axis illumination beam and the axis of the imaging module, the off-axis illumination ray reflected from the inclined area has a larger tilt angle with the axis. More light cannot enter the imaging module to participate in imaging, increasing the brightness difference of the image between different tilt angles, facilitating the identification of shallow defects and improving detection accuracy.

[0058] Optionally, Figure 6 This is a schematic diagram of the structure of another defect detection device provided in an embodiment of the present invention, with reference to... Figure 6Based on the aforementioned embodiments, the imaging module 402 includes: an objective lens 601 and a camera 602 (excluding the beam splitter 606). The objective lens 601 is disposed between the object-carrying plane 401 and the camera 602, and is used to collect the imaging beam formed by the reflection or scattering of the detection beam by the surface to be detected. The camera 602 is used to image the surface to be detected based on the imaging beam and generate an image signal. The off-axis illumination module 600 includes: a light-emitting unit 603, an aperture stop 604, a first condenser lens 605, and a beam splitter 606. The light-emitting unit 603 is used to generate and emit a light source; the aperture stop 604 is disposed off-axis and is used to generate an off-axis illumination beam based on the light source. The first condenser lens 605 is disposed in the optical path of the off-axis illumination beam, and the first condenser lens is used to focus the off-axis illumination beam. Beam splitter 606 is disposed between objective lens 601 and camera 602. Off-axis illumination beam is reflected by beam splitter 606, enters objective lens 601 and illuminates the surface to be inspected. The angle between the principal ray of the off-axis illumination beam reflected by beam splitter 606 and the axis O of objective lens 601 is not 0.

[0059] The objective lens 601 is a microlens group with high magnification, which can converge the imaging beam reflected from the surface to be tested, forming a magnified real image on the image sensor of the camera 602. The camera 602 is an image sensing device that images the surface to be tested based on the imaging beam received and propagated by the objective lens 601, generates a corresponding analog signal based on the received light, and then performs digital-to-analog conversion. The light-emitting unit 603 is a light source component capable of generating a light source. The aperture stop 604 is an aperture stop with an off-axis transparent aperture 607. The non-transparent aperture 607 of the aperture stop blocks light, allowing light to pass through only the transparent aperture 607. The first condenser lens 605 is a convex lens that can converge the off-axis illumination beam. The beam splitter 606 is a dual-function mirror positioned between the objective lens 601 and the camera 602. It can both reflect the off-axis illumination beam into the objective lens 601, thus illuminating the object plane 401 off-axis, and allow the imaging beam reflected from the surface to be tested to pass through and be projected onto the camera 602.

[0060] Specifically, the light-transmitting hole 607 of the aperture stop 604 is disposed off-axis. The light-transmitting hole 607 of the aperture stop 604 can be circular, elliptical, annular, rectangular, or any irregular shape. Preferably, Figure 7 This is a schematic diagram comparing the aperture range of an aperture stop and the aperture range of an objective lens, provided as an embodiment of the present invention. Figure 6 and Figure 7 The light-transmitting hole 607 of the aperture stop 604 can be circular (the white circular part in the figure). Figure 7The dashed circle in the diagram is an indicator line, representing the aperture range of objective lens 601. It indicates the distribution range of illumination light that objective lens 601 can receive when the aperture 607 of aperture stop 604 is infinitely large. In other words, when the aperture 607 is the same size as the dashed circle, all the illumination light generated by the aperture 607 can enter objective lens 601. The circular aperture 607 of aperture stop 604 can be tangent to or close to the inner edge of the dashed circle representing the aperture range. Therefore, the off-axis illumination beam generated by aperture stop 604 can be tangent to or close to the inner edge of the aperture of objective lens 601 and enter objective lens 601. This ensures that more reflected light from the defect of the surface to be inspected deviates from the maximum aperture angle range of objective lens 601, thus making the proportion of imaging light retained within the aperture angle range of objective lens 601 smaller than the total reflected light from the defect. It should be noted that the area of ​​the dashed circle representing the aperture range, i.e. the aperture area of ​​the objective lens 601, refers to the area of ​​the pattern formed by the intersection of all the light rays generated by the light source that can enter the aperture of the objective lens 601 and illuminate the surface to be inspected, when the light-transmitting aperture is large enough, through the light path set in the off-axis illumination module 600.

[0061] In addition, combined Figure 2 , Figure 6 and Figure 7 The smaller the angular range of the off-axis illumination light, the smaller the proportion of the imaging light at the defect to all reflected light at the defect for the same orange peel defect, thus resulting in a smaller difference in imaging brightness between the smooth area and the defect. However, a smaller angular range of the off-axis illumination light also reduces the illumination intensity, which negatively impacts the imaging effect. Therefore, it is necessary to balance the relationship between brightness difference and illumination intensity and select an appropriate off-axis angular range. The ratio of the area of ​​the light-transmitting aperture 607 of the aperture stop 604 to the aperture area of ​​the objective lens 601 is within a first range, for example, the first range can be 0.1 to 0.3. Experimental verification shows that the first range of 0.1 to 0.3 can ensure that the ratio between the minimum and maximum energy of the imaging beam at each point on the surface to be inspected with an orange peel defect is within the range of 0.8 to 0.96, so as to capture the orange peel defect, while also ensuring sufficient illumination intensity to ensure sufficient total imaging brightness. Here, the maximum and minimum energy of the imaging beam are the cross-sections of the same orange peel defect (e.g., Figure 2The concept of relative energy between adjacent points A and B (as shown) does not involve comparisons between multiple orange peel defects. Specifically, the maximum energy of the imaging beam refers to the energy value of the reflected beam generated after the off-axis illumination ray is reflected from point A, which is the energy value of the imaging beam that can enter the objective lens and ultimately participate in imaging. The minimum energy of the imaging beam refers to the energy value of the reflected beam generated after the off-axis illumination ray is reflected from point B, which is the energy value of the imaging beam that can enter the objective lens and ultimately participate in imaging. The definitions of points A and B have been explained in detail above and will not be repeated here.

[0062] The light source is processed by the aperture stop 604 to generate an off-axis illumination beam. The off-axis illumination beam is focused by the first condenser lens 605 and then enters the beam splitter 606, and is reflected into the objective lens 601. The off-axis illumination beam in the objective lens 601 has an angle with the axis O of the objective lens 601, and the angle is not 0.

[0063] For example, Figure 8 This is a schematic diagram illustrating the aperture range of an objective lens, the distribution range of the off-axis illumination beam, and the angular distribution range of the reflected light, provided as an embodiment of the present invention. Figure 6 and Figure 8 The off-axis illumination beam can enter the objective lens 601 entirely along the edge of its aperture, thus illuminating the entire surface to be inspected. However, only a portion of the reflected light from the surface containing the orange peel defect returns to the objective lens 601 and participates in the imaging process. The portion of the reflected light that fails to return to the objective lens 601 originates from locations on the surface where the defect is located (e.g., [missing information]). Figure 2 Point B) reflects the light. The angle between the off-axis illumination beam and the axis O of the imaging module 402 can be set so that the ratio between the minimum and maximum energy of the imaging beam at a single point on the surface to be detected is in the range of 0.8 to 0.96, which can capture orange peel defects while ensuring a certain illumination intensity.

[0064] The defect detection device provided in this embodiment includes an imaging module comprising an objective lens and a camera, and an off-axis illumination module comprising a light-emitting unit, an aperture stop, a first condenser lens, and a beam splitter. The light source is processed by the aperture stop to generate an off-axis illumination beam, which is then focused by the first condenser lens and enters the beam splitter, and finally reflected into the objective lens. The off-axis illumination beam forms an angle with the objective lens axis. This angle is set such that the ratio between the minimum and maximum energy of the imaging beam at a single point on the surface to be inspected is within the range of 0.8 to 0.96. This allows for the detection of orange peel defects while ensuring a certain illumination intensity, thereby improving the detection rate of orange peel defects and ensuring sufficient illumination intensity, thus enhancing the accuracy of the defect detection device.

[0065] Optionally, Figure 9 This is a schematic diagram of the structure of another defect detection device provided in an embodiment of the present invention, with reference to... Figure 9 Based on the aforementioned embodiments, the off-axis illumination module 600 further includes a second condenser lens 901 and a reflector 902. The second condenser lens 901 is disposed between the light-emitting unit 603 and the aperture stop 604, and is used to focus the light source. The reflector 902 is disposed between the first condenser lens and the beam splitter 606, and is used to reflect the off-axis illumination beam onto the beam splitter 606.

[0066] Specifically, the second condenser lens is a convex lens, which can converge the light source before it passes through the aperture stop 604, allowing more light to pass through the light transmission hole 607 to become an off-axis illumination beam, further increasing the light intensity of the off-axis illumination beam, thereby improving the imaging brightness and increasing the reliability of defect detection. The reflector 902 is disposed in the optical path of the off-axis illumination beam, between the first condenser lens and the beam splitter 606, and can reflect the off-axis illumination beam onto the beam splitter 606.

[0067] For example, Figure 10 This is an imaging effect diagram of a surface to be detected provided in an embodiment of the present invention, combined with... Figure 9 and Figure 10 ,use Figure 9 The defect detection device shown performs defect detection on the wafer surface. In this device, the ratio of the area of ​​the aperture of the aperture stop to the area of ​​the objective lens falls within a first range. Under these conditions, such as... Figure 10 The image of the camera shown clearly shows orange peel defects, with different shades of color at different tilt angles. The imaging effect is far better than the defect monitoring device in the background technology.

[0068] In the defect detection device provided in this embodiment, the off-axis illumination module generates and emits an off-axis illumination beam, and the imaging module images the surface to be tested based on the imaging beam formed by the reflection of the off-axis illumination beam from the surface to be tested, thereby generating an image signal. The angle between the principal ray of the off-axis illumination beam and the axis of the imaging module is not zero. The analysis and processing module is connected to the imaging module and identifies the defect area of ​​the surface to be tested based on the image signal, thus realizing defect detection of the object under test. Because there is an angle between the principal ray of the off-axis illumination beam and the axis of the imaging module, the off-axis illumination ray reflected from the inclined area has a larger tilt angle with the axis, preventing more light from entering the imaging module to participate in imaging. This increases the brightness difference of the image between different tilt angles, facilitating the identification of shallow defects and improving detection accuracy.

[0069] This invention also provides a defect detection method, which can be implemented using any defect detection device described in this invention. Figure 11 This is a flowchart illustrating a defect detection method provided in an embodiment of the present invention, referring to... Figure 11 Defect detection methods include:

[0070] S1001, Off-axis illumination module generates and emits off-axis illumination beam.

[0071] S1002 The imaging module images the surface to be inspected based on the imaging beam formed by the reflection of the off-axis illumination beam by the surface to be inspected, so as to generate an image signal.

[0072] In this case, the angle between the principal ray of the off-axis illumination beam and the axis of the imaging module is not 0.

[0073] S1003, The analysis and processing module identifies the defect area of ​​the surface to be inspected based on the image signal.

[0074] The defect detection method provided in this embodiment generates and emits an off-axis illumination beam by an off-axis illumination module. The imaging module images the surface to be inspected based on the imaging beam formed by the reflection of the off-axis illumination beam from the surface to be inspected, thereby generating an image signal. Since the angle between the principal ray of the off-axis illumination beam and the axis of the imaging module is not 0, the angle between the incident light and the tilted position on the surface to be inspected can be larger relative to the axis of the imaging module. As a result, more reflected light from the tilted position is reflected out of the objective lens and does not participate in the imaging, thereby increasing the difference in imaging brightness at different tilted positions, increasing the distinguishability of differences during signal analog-to-digital conversion, and thus improving the detection rate of orange peel defects.

[0075] Figure 12 This is a flowchart illustrating another defect detection method provided in an embodiment of the present invention, referring to... Figure 12 Defect detection methods include:

[0076] S1101, the light-emitting unit generates and emits a light source.

[0077] S1102, the aperture stop generates an off-axis illumination beam based on the light source.

[0078] S1103, The first condenser lens focuses the off-axis illumination beam.

[0079] S1104. The beam splitter reflects the off-axis illumination beam after it has been focused, so that the off-axis illumination beam enters the objective lens and illuminates the surface to be inspected.

[0080] S1105. The objective lens collects the imaging beam formed by the reflection or scattering of the detection beam by the surface to be detected.

[0081] S1106. The camera images the surface to be detected based on the imaging beam, generating an image signal.

[0082] S1107 The analysis and processing module identifies the defect area of ​​the surface to be inspected based on the image signal.

[0083] The defect detection device and method provided in this embodiment include an off-axis illumination module for generating and emitting an off-axis illumination beam, and an imaging module for imaging the surface to be tested based on the imaging beam formed by the reflection of the off-axis illumination beam from the surface to be tested, thereby generating an image signal. The angle between the principal ray of the off-axis illumination beam and the axis of the imaging module is not zero. An analysis and processing module connected to the imaging module is used to identify defect areas on the surface to be tested based on the image signal, thus achieving defect detection of the object under test. Because there is an angle between the principal ray of the off-axis illumination beam and the axis of the imaging module, the off-axis illumination ray reflected from the inclined area can have a larger tilt angle with the axis, preventing more light from entering the imaging module to participate in imaging. This increases the brightness difference of the imaging between different tilt angles, facilitating the identification of shallow defects and improving detection accuracy.

[0084] The above-described products can perform the methods provided in any embodiment of the present invention, and have the corresponding functional modules and beneficial effects for performing the methods.

[0085] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A defect detection device, characterized in that, include: The system includes a loading plane, off-axis illumination module, imaging module, and analysis and processing module. The object-carrying plane is used to support the object to be measured; the imaging module includes an objective lens and a camera; The off-axis illumination module generates and emits an off-axis illumination beam. Specifically, the off-axis illumination module includes a light-emitting unit, an aperture stop, a first condenser lens, and a beam splitter. The light-emitting unit generates and emits a light source. The aperture stop is off-axis and generates the off-axis illumination beam based on the light source. The first condenser lens is positioned in the optical path of the off-axis illumination beam and focuses the beam. The beam splitter is positioned between the objective lens and the camera. Reflected by the beam splitter, the light enters the objective lens and illuminates the surface to be inspected. The off-axis illumination beam generated by the aperture stop enters the objective lens tangentially or close to the inner edge of the aperture. The ratio of the area of ​​the aperture stop to the area of ​​the objective lens aperture is between 0.1 and 0.3, so that the ratio between the minimum and maximum energy of the imaging beam at each point on the surface to be inspected with orange peel defects at the nanometer level is between 0.8 and 0.96, while also ensuring the overall brightness of the image. The imaging module is used to image the surface to be tested based on the imaging beam formed by the reflection of the off-axis illumination beam by the surface to be tested of the test object, so as to generate an image signal. The angle between the principal ray of the off-axis illumination beam and the axis of the imaging module is not 0. The light source emitted by the same light-emitting unit enters the objective lens at different angles through the beam splitter, forming multiple non-parallel light paths that illuminate the same point on the surface to be tested. This allows the light reflected from the off-axis illumination beam at the location with orange peel defects to deviate more from the imaging module, increasing the grayscale difference between the flat location and the location with orange peel defects on the surface to be tested during imaging. The analysis and processing module is connected to the imaging module and is used to identify the shallow defect area of ​​the surface to be detected based on the fact that there is at least one gray level difference between the gray values ​​of the flat position and the position with orange peel defects in the image signal.

2. The defect detection device according to claim 1, characterized in that, The objective lens is disposed between the object-carrying plane and the camera, and is used to collect the imaging beam formed by the detection beam after being reflected or scattered by the surface to be detected; The camera is used to image the surface to be detected based on the imaging beam, and generate the image signal.

3. The defect detection device according to claim 1, characterized in that, The off-axis illumination module further includes: a second focusing lens; The second condensing lens is disposed between the light-emitting unit and the aperture stop, and the second condensing lens is used to concentrate the light source.

4. The defect detection device according to claim 1, characterized in that, The off-axis illumination module further includes a reflector, which is disposed between the first condenser lens and the beam splitter, and is used to reflect the off-axis illumination beam onto the beam splitter.

5. The defect detection device according to any one of claims 1-4, characterized in that, The aperture of the aperture stop can be circular, elliptical, annular, rectangular, or irregular in shape.

6. A defect detection method, characterized in that, The defect detection method is implemented using the defect detection apparatus as described in any one of claims 1-5, and includes: The off-axis illumination module generates and emits an off-axis illumination beam, specifically including: a light-emitting unit generating and emitting a light source; an aperture stop generating the off-axis illumination beam according to the light source; a first condenser lens focusing the off-axis illumination beam; and a beam splitter reflecting the focused off-axis illumination beam, allowing the off-axis illumination beam to enter the objective lens and illuminate the surface to be inspected. The off-axis illumination beam generated by the aperture stop will enter the objective lens tangentially to or near the inner edge of the objective lens's aperture. The ratio of the aperture area of ​​the aperture stop to the aperture area of ​​the objective lens is between 0.1 and 0.3, ensuring that the ratio between the minimum and maximum energy of the imaging beam at each point on the surface to be inspected, which has an orange peel defect with a depth of nanometers, is between 0.8 and 0.96, while also guaranteeing the overall brightness of the image. The imaging module images the surface to be tested based on the imaging beam formed by the reflection of the off-axis illumination beam after it is reflected by the surface to be tested, thereby generating an image signal. The angle between the principal ray of the off-axis illumination beam and the axis of the imaging module is not 0. The light source emitted by the same light-emitting unit enters the objective lens at different angles through the beam splitter, forming multiple non-parallel light paths that illuminate the same point on the surface to be tested. This allows the light reflected from the off-axis illumination beam at the location with orange peel defects to deviate more from the imaging module, increasing the grayscale difference between the flat location and the location with orange peel defects on the surface to be tested during imaging. The analysis and processing module identifies shallow defect areas on the surface to be detected based on the fact that the gray values ​​of the flat areas and the areas with orange peel defects in the image signal differ by at least one gray level.

7. The defect detection method according to claim 6, characterized in that, The imaging module images the surface to be detected based on the imaging beam formed by the reflection of the off-axis illumination beam after it passes through the surface to be detected, in order to generate an image signal, including: The objective lens collects the imaging beam formed by the reflection or scattering of the detection beam by the surface to be detected; The camera images the surface to be detected based on the imaging beam, generating the image signal.

Images