A detection apparatus and method

Abstract

The application provides a detection device and method. The detection device obtains first light intensity distribution information of signal light corresponding to a sampling position on a to-be-detected element by interference of first echo light and second echo light reflected by the surface of the to-be-detected element through a first detection device, and further obtains phase distribution of the signal light according to the intensity distribution, so as to obtain defect distribution data of the to-be-detected element. The first detection device comprises two or more polarization detectors or no polarization detector and at least one polarization detector. The application can effectively realize polarization state analysis of the signal light, realize high-precision detection of the to-be-detected element in the longitudinal direction, and has good reliability, high stability and fast detection speed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical detection, in particular to a detection device and method. BACKGROUND

[0002] Wafer defect detection refers to detecting whether there are defects such as grooves, particles, scratches and defect positions on the wafer. Wafer defect detection is widely used. As a chip substrate, defects on the wafer may cause the failure of the expensive process made thereon, so the wafer manufacturer often detects defects to ensure product yield, and the wafer user also needs to determine the defect level of the wafer before use to ensure product yield; wafer defect detection is also often used to test whether the semiconductor instrument has additional contamination.

[0003] Optical detection method has the characteristics of fast detection speed and no additional contamination, and is widely used in component defect detection. However, the existing optical detection method for detecting wafer defects, such as light scattering method, has low detection accuracy in the wafer axial direction (perpendicular to the wafer surface direction). SUMMARY

[0004] In view of this, the purpose of the present application is to provide a detection device and method which can effectively improve the technical problem of low detection accuracy in the wafer axial direction of the prior art.

[0005] In a first aspect, an embodiment of the present application provides a detection device, comprising: a light generation modulation device and a first detection device. The light generation modulation device is used to generate first polarized light and second polarized light, make the first polarized light reflect on the surface of the measured component to form first echo light, make the second polarized light reflect on the surface of the measured component to form second echo light, and make the first echo light and the second echo light interfere to form signal light, wherein the first polarized light and the second polarized light have a preset shear between the centers. The first detection device is used to obtain the first light intensity distribution information of the signal light, the first detection device comprises two or more detectors, the two or more detectors are all polarized detectors, and the polarization detection directions of different polarized detectors are different, or the two or more detectors comprise a non-polarized detector and at least one polarized detector.

[0006] Further, the first detection device comprises a first detection area, the first detection area is used to scan the surface of the measured component; the first detection area comprises a plurality of first detection unit areas, the arrangement direction of the plurality of first detection unit areas is not perpendicular to the scanning direction of the first detection area on the surface of the measured component, and each detector is used to detect the signal light reflected by the measured surface corresponding to different first detection unit areas respectively.

[0007] Further, the arrangement direction of the plurality of first probe unit regions is parallel to the scanning direction of the first probe region on the surface of the element to be measured.

[0008] Further, the first probe region is strip-shaped, and the extension direction of the first probe region is perpendicular to the scanning direction of the first probe region on the surface of the element to be measured.

[0009] Further, when the surface to be measured of the element to be measured is circular, the first probe region extends along the radial direction of the surface of the element to be measured; and the scanning direction of the first probe region on the surface to be measured of the element to be measured is perpendicular to the diameter direction of the surface to be measured.

[0010] Further, the first polarized light and the second polarized light are used to form a probe light spot on the surface of the element to be measured; and in the scanning direction of the first probe region on the surface of the element to be measured, the size of the probe light spot is greater than or equal to the size of the first probe region.

[0011] Further, each of the polarization detectors is a polarization line detector, and the non-polarization detector is a line detector. Using the polarization line detector is beneficial to increase the detection area of a single sampling and further improve the detection efficiency.

[0012] Further, when the number of the polarization detectors is two, the polarization detection directions of the two polarization detectors are perpendicular to each other.

[0013] Further, when the first probe device includes three or more polarization detectors, the three or more polarization detectors include a first polarization detector, a second polarization detector, and a third polarization detector, wherein the included angle between the polarization detection directions of the third polarization detector and the first polarization detector is equal to 360° / n, n is an integer greater than or equal to 3, and n is the number of the polarization detectors. Using three or more polarization detectors can more accurately obtain the phase information of the signal light, so as to obtain a more accurate height measurement result.

[0014] Further, the polarization detection directions of the first polarization detector and the third polarization detector are perpendicular, and the included angle between the polarization detection directions of the third polarization detector and the second polarization detector is 45°.

[0015] Further, when the first probe device includes a non-polarization detector and at least one polarization detector, the number of the polarization detectors is two or more, wherein the included angle between the polarization detection directions of the two polarization detectors is an acute angle or an obtuse angle.

[0016] Further, the light generation modulation device includes:

[0017] a first light generating device for generating a first polarized light and a second polarized light, the first polarized light and the second polarized light having a preset shearing amount between the centers of the first polarized light and the second polarized light, the first polarized light being reflected by a surface of a to-be-detected element to form a first echo light, the second polarized light being reflected by the surface of the to-be-detected element to form a second echo light, and the first echo light beam and the second echo light beam being combined;

[0018] a polarization controller for modulating a polarization direction of the first echo light beam and the second echo light beam, so that the first echo light beam and the second echo light beam interfere to form a signal light.

[0019] Further, the first light generating device comprises a probe light generating module and a light beam adjusting module, and the probe light generating module and the light beam adjusting module are coupled.

[0020] The probe light generating module is configured to generate a first probe light.

[0021] The light beam adjusting module is configured to divide the first probe light into the first polarized light and the second polarized light, and combine the first echo light beam and the second echo light beam.

[0022] Further, the probe light generating module comprises a first light source and a beam expanding and shaping device, the first light source is configured to generate a first probe light, and the beam expanding and shaping device is configured to control a spot shape and size of the surface of the to-be-detected element.

[0023] Further, the light beam adjusting module comprises a birefringent crystal.

[0024] Further, the first probe light is linearly polarized light, circularly polarized light or elliptically polarized light. When the probe light is linearly polarized light, it is beneficial to simplify the subsequent demodulation process.

[0025] Further, the detection device further comprises a first processing device, and the first probe device is electrically connected to the first processing device. The first processing device is configured to acquire defect information of the to-be-detected element according to first light intensity distribution information of the signal light.

[0026] Further, the first processing device comprises:

[0027] a signal demodulation module configured to acquire initial information of the signal light according to the first light intensity distribution information of the signal light;

[0028] a noise acquisition module configured to perform low-pass filtering processing on the first light intensity distribution information of the signal light to acquire noise information;

[0029] a target information acquisition module configured to acquire the defect information of the to-be-detected element according to the initial information and the noise information.

[0030] Further, the initial information includes initial phase information of the signal light, and the noise information includes noise phase information. The target information acquisition module includes: a target phase acquisition submodule, configured to perform difference processing on the initial phase information and the noise phase information to acquire target phase information; and a defect information acquisition submodule, configured to acquire defect information of the to-be-tested element according to the target phase information. In this way, phase noise contained in the signal light can be filtered out, and the accuracy of the detection result can be improved.

[0031] Further, the target information acquisition module further includes: a defect standard library, which includes preset phase information and preset defect information, and is configured to determine a corresponding relationship between the preset phase information and the preset defect information; and the defect information acquisition submodule is specifically configured to search the defect standard library according to the target phase information to acquire corresponding preset defect information, and obtain the defect information of the to-be-tested element.

[0032] Further, the detection device further includes: a second detection device, configured to collect scattered light on the surface of the to-be-tested element and acquire second light intensity distribution information of the scattered light; and a second processing device, configured to acquire first defect information of the to-be-tested element according to the first light intensity distribution information, acquire second defect information of the to-be-tested element according to the second light intensity distribution information, and obtain target defect information of the to-be-tested element based on the first defect information and the second defect information. In this way, double-channel detection can be implemented, and the horizontal resolution can be improved on the basis of improving the vertical precision of defect detection.

[0033] Further, the detection device further includes: a second light generation device, configured to generate second detection light, and make the second detection light scattered on the surface of the to-be-tested element to form the scattered light.

[0034] In a second aspect, an embodiment of the present application further provides a defect detection method, applied to the detection device provided in the first aspect, and the method includes: generating first polarized light and second polarized light through a light generation modulation device, and making the first polarized light reflected on a to-be-tested surface of a to-be-tested element to form first echo light, and making the second polarized light reflected on the to-be-tested surface to form second echo light, wherein the first polarized light and the second polarized light have a preset shear amount between centers; making the first echo light and the second echo light interfere through the light generation modulation device to form signal light; and acquiring light intensity information of the signal light along multiple different polarization directions through a first detection device, or acquiring total light intensity information of the signal light and light intensity information along at least one polarization direction.

[0035] Further, when the first detection device comprises a first detection area, the first detection area comprises a plurality of first detection unit areas; the method further comprises: controlling the first polarized light and the second polarized light to scan on the surface to be measured, and repeating the steps of forming the signal light and acquiring the light intensity information.

[0036] Further, the scanning direction of the first polarized light and the second polarized light on the surface to be measured is the same as the arrangement direction of the plurality of first detection unit areas.

[0037] Further, the step of acquiring the light intensity information of the signal light along a plurality of different polarization directions by the first detection device, or acquiring the total light intensity information of the signal light and the light intensity information along at least one polarization direction comprises: sampling the light intensity of the signal light by the first detection device, the distance scanned by the first detection area in the time interval between adjacent two samplings is a scanning step, and the distance between the centers of adjacent first detection unit areas is equal to an integer multiple of the scanning step.

[0038] Further, the distance between the centers of adjacent first detection unit areas is equal to the scanning step.

[0039] Further, the step of controlling the first polarized light and the second polarized light to scan on the surface to be measured comprises: controlling the surface to be measured of the measured element to move in the direction opposite to the scanning direction.

[0040] Further, the step of controlling the surface to be measured of the measured element to move in the direction opposite to the scanning direction comprises: controlling the measured element to rotate around a rotation shaft perpendicular to the surface to be measured. The step of controlling the first polarized light and the second polarized light to scan on the surface of the measured element further comprises: after the surface to be measured rotates one circle around the rotation shaft or in the process of the surface to be measured rotating around the rotation shaft, controlling the light spot formed by the first polarized light and the second polarized light on the surface to be measured to move along the diameter direction of the surface to be measured.

[0041] Further, when the light generating modulation device comprises a first light source and a beam expanding and shaping device, the step of generating the first polarized light and the second polarized light comprises: generating first detection light by the first light source to form the first polarized light and the second polarized light based on the first detection light; adjusting the light spot shape and size formed by the first polarized light and the second polarized light on the surface to be measured of the measured element by the beam expanding and shaping device, so that the size of the light spot is greater than or equal to the size of the first detection area in the scanning direction of the surface to be measured of the measured element.

[0042] Further, the first intensity distribution information of the signal light is obtained by using the light intensity information of the signal light along multiple different polarization directions or the total light intensity information and the light intensity information along at least one polarization direction.

[0043] Further, the obtaining of the defect information of the element to be tested according to the first intensity distribution information of the signal light comprises: obtaining initial information of the signal light according to the first intensity distribution information; performing low-pass filtering processing on the first intensity distribution information to obtain noise information; and obtaining the defect information of the element to be tested according to the initial information and the noise information.

[0044] Further, the initial information comprises initial phase information of the signal light, and the noise information comprises noise phase information. The obtaining of the defect information of the element to be tested according to the initial information and the noise information comprises: performing difference processing on the initial phase information and the noise phase information to obtain target phase information; and obtaining the defect information of the element to be tested according to the target phase information.

[0045] Further, the obtaining of the defect information of the element to be tested according to the target phase information comprises: searching for corresponding preset defect information in a preconfigured defect standard library according to the target phase information to obtain the first defect information of the surface of the element to be tested, wherein the defect standard library comprises a corresponding relationship between multiple preset phase information and corresponding preset defect information.

[0046] The detection device provided by the embodiment of the application obtains the intensity distribution of the signal light corresponding to each sampling position on the element to be tested in different polarization directions through the signal light formed by the interference of the first echo light and the second echo light reflected by the surface of the element to be tested, and further obtains the phase distribution of the signal light according to the intensity distribution, so as to obtain the defect distribution data of the element to be tested. The first detection device comprises two or more polarization detectors or no polarization detector and at least one polarization detector, the polarization state analysis of the signal light can be effectively realized through the first detection device, the high-precision detection of the element to be tested in the longitudinal direction (perpendicular to the direction of the surface to be tested) can be realized, and the detection device has good reliability, high stability and fast detection speed.

[0047] In order to make the above-mentioned objects, characteristics and advantages of the application more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are referred to. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation to the scope. Other related drawings can also be obtained by those skilled in the art without any creative effort.

[0049] Figure 1 A structural schematic diagram of a detection device provided for the first embodiment of the present application;

[0050] Figure 2 A first detection zone schematic diagram of a first detection device provided for the first embodiment of the present application;

[0051] Figure 3 A structural schematic diagram of a detection device provided for the first embodiment of the present application;

[0052] Figure 4 A phase distribution schematic diagram of a detection result (including phase noise) provided for the first embodiment of the present application;

[0053] Figure 5 A signal preprocessing process schematic diagram provided for the first embodiment of the present application;

[0054] Figure 6 A phase distribution schematic diagram of a detection result (filtering out phase noise) provided for the first embodiment of the present application;

[0055] Figure 7 Another structural schematic diagram of a detection device provided for the first embodiment of the present application;

[0056] Figure 8 A flowchart of a defect detection method provided for the second embodiment of the present application;

[0057] Figure 9 A scanning track schematic diagram of a wafer under an application scenario provided for the second embodiment of the present application.

[0058] In the drawings, the reference signs are respectively: detection device 1, 2; detection light generating module 10; first light source 101; beam expanding and shaping device 102, 74; polarizer 103; light beam adjusting module 20; first beam splitter 201; birefringent crystal 202; objective lens 203; polarization controller 30; first detection device 40; first detection zone 401; first detector 41; second detector 42; third detector 43; fourth detector 44; object table 50; element to be detected 60; surface to be detected 600; scanning track 601; target region 602; second light generating device 71; second detection device 72; second beam splitter 73; first filter 75; second filter 76; converging lens 77. DETAILED DESCRIPTION

[0059] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Generally, the components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0060] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0061] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0062] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present application is usually placed, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third", "fourth" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0063] In the description of the present application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "arrangement", "connection", "coupling" should be understood broadly. For example, the connection can be a fixed connection, or a detachable connection, or an integral connection; can be a mechanical connection, or an electrical connection; can be a direct connection, or an indirect connection through an intermediate medium, or a communication inside two elements. The coupling between two devices means that the light emitted by one device is incident on the other device. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0064] As Figure 1As shown, the first embodiment of the present application provides a detection device 1, comprising: a light generating and modulating device and a first detection device 40. It should be noted that the element 60 to be detected by the detection device 1 can be a wafer or other elements such as coated optical elements, etc.

[0065] The light generating and modulating device is configured to generate a first polarized light and a second polarized light, make the first polarized light reflect off the surface of the element 60 to be detected to form a first echo light, make the second polarized light reflect off the surface of the element 60 to be detected to form a second echo light, and make the first echo light and the second echo light interfere to form a signal light. The first polarized light and the second polarized light have a preset shear between their centers. In an embodiment of the present application, the first polarized light and the second polarized light have the same propagation direction.

[0066] Specifically, the light generating and modulating device can comprise: a first light generating device and a polarization controller 30, the first light generating device is coupled to the polarization controller 30, and the polarization controller 30 is coupled to the first detection device 40. The first light generating device is configured to generate the first polarized light and the second polarized light, make the first polarized light reflect off the surface of the element 60 to be detected to form the first echo light, make the second polarized light reflect off the surface of the element 60 to be detected to form the second echo light, and make the first echo light and the second echo light combine to form the signal light.

[0067] Specifically, as shown in the figure, Figure 1 The first light generating device comprises a detection light generating module 10 and a light beam adjusting module 20, and the detection light generating module 10 is coupled to the light beam adjusting module 20. The detection light generating module 10 is configured to generate a first detection light. The light beam adjusting module 20 is configured to divide the first detection light into the first polarized light and the second polarized light, make the first polarized light and the second polarized light perpendicularly incident on the surface of the element 60 to be detected, and combine the first echo light reflected by the element 60 to be detected and the second echo light reflected by the element 60 to be detected. Specifically, the first detection light generated by the detection light generating module 10 enters the light beam adjusting module 20, is processed by the light beam device module to form the first polarized light and the second polarized light, and is incident on the surface of the element 60 to be detected. The first echo light reflected by the element 60 to be detected and the second echo light reflected by the element 60 to be detected are combined by the light beam adjusting module 20 and then enter the polarization controller 30.

[0068] In this embodiment, the first probe light can be monochromatic light such as 532 nm wavelength, and the spot shape and size can be set according to specific needs, and adapt to the detection area of the detection device. For example, a circular spot or a rectangular spot can be used. As an optional implementation, the first probe light generated by the probe light generation module 10 is linearly polarized light. Of course, in other embodiments of the present application, the first probe light can also be circularly polarized light or elliptically polarized light, which can be set as needed.

[0069] As an optional implementation, the probe light generation module 10 can include a first light source 101, a beam expanding and shaping device 102, and a polarizer 103. The first light source 101 is used to generate an initial light beam. The beam expanding and shaping device 102 is used to expand and shape the initial light beam into a first light beam with a preset size and a preset shape, so as to adjust the spot size and shape of the first polarized light and the second polarized light formed on the surface of the element to be measured 60. The polarizer 103 is used to adjust the polarization state of the first light beam to form a second light beam with a preset polarization state, thereby controlling the polarization state of the first polarized light and the second polarized light formed. Specifically, the initial light beam emitted by the first light source 101 is incident on the beam expanding and shaping device 102, and the first light beam is formed after the beam expanding and shaping processing of the beam expanding and shaping device 102. The second light beam emitted by the polarizer 103 is the first probe light.

[0070] It should be noted that the detection device 1 provided in this embodiment has low requirements on the monochromaticity of the first light source 101. Therefore, in this embodiment, the first light source 101 can use a laser, or the first light source 101 can include an LED light source and a narrow-band filter, and the light beam emitted by the LED light source is filtered by the narrow-band filter to form the initial light beam.

[0071] The beam expanding and shaping device 102 can be composed of one or more lenses and diaphragms, and the specific structure can be set according to the actual first light source 101 used and the required spot shape and size. In this embodiment, the spot shape after the beam expanding and shaping device 102 can be a linear spot or a rectangular spot, so as to facilitate the detection of the linear area of the element to be measured 60. Of course, in other embodiments of the present application, the spot after the beam expanding and shaping device 102 can also be other shapes, such as a circular spot or a square spot.

[0072] The polarizer 103 can be set according to the polarization state requirements of the first polarized light and the second polarized light. In an embodiment of the present application, the polarizer 103 can adjust the light beam emitted by the beam expanding and shaping device 102 to linearly polarized light with an angle of 45 degrees between the polarization direction and the optical axis of the polarizer 103. Of course, in other embodiments of the present application, the polarizer 103 can adjust the light beam emitted by the beam expanding and shaping device 102 to linearly polarized light in other directions, such as linearly polarized light with an angle of 30 degrees between the polarization direction and the optical axis of the polarizer 103, linearly polarized light with an angle of 60 degrees between the polarization direction and the optical axis of the polarizer 103, etc., which can be set according to requirements.

[0073] In addition, in other embodiments of the present application, when the first polarized light and the second polarized light corresponding to the initial light beam generated by the first light source 101 can meet the requirements in terms of spot shape and size on the surface of the element to be measured 60, the initial light beam emitted by the first light source 101 does not need to be expanded and shaped. At this time, the probe light generating module 10 can not include the above-mentioned beam expanding and shaping device 102, but only include the first light source 101 and the polarizer 103. Alternatively, when the first polarized light and the second polarized light corresponding to the initial light beam generated by the first light source 101 have a relatively large spot area on the surface of the element to be measured 60 and can meet the requirements, such as when the first light source 101 includes an LED light source and a narrow-band filter, the initial light beam emitted by the first light source 101 does not need to be expanded, but only needs to be shaped into the required shape. At this time, the probe light generating module 10 can include a light source, a beam shaping component, and a polarizer 103, wherein the beam shaping component can adopt a diaphragm for shaping the spot shape of the initial light beam emitted by the first light source 101.

[0074] In an embodiment of the present application, the first polarized light and the second polarized light can both be linearly polarized light, and the polarization directions are perpendicular to each other. At this time, the beam adjusting module 20 can specifically include a birefringent crystal 202 and an objective lens 203, as shown in FIG. 2B. Figure 1

[0075] The birefringent crystal 202 is used to divide the first probe light into two linearly polarized lights with a small included angle and perpendicular to each other based on the birefringence effect. Due to the anisotropy of the crystal material, the size of the included angle of the two refracted light rays is related to the propagation direction of the light wave and the polarization state. In order to minimize the included angle of the two refracted light rays, the transverse shear of the first polarized light and the second polarized light is minimized, thereby improving the detection accuracy. As an embodiment, the birefringent crystal 202 can adopt a Nomarski prism. Of course, in other embodiments of the present application, other applicable birefringent crystals 202 can also be used. It should be noted that when the vibration direction of the probe light is at an angle of 45 degrees with the optical axis, the light intensity of the first polarized light and the second polarized light is equal, which is beneficial to simplify the subsequent signal processing. ​

[0076] The objective lens 203 can be composed of one or more lenses, and is used to convert the two beams of linearly polarized light with a small included angle and perpendicular polarization directions, which are emitted by the birefringent crystal 202, into two beams of parallel light with a preset shearing amount, i.e., the first polarized light and the second polarized light.

[0077] Of course, in order to reasonably arrange the optical path, the beam adjustment module 20 can further include the first beam splitter 201 in addition to the birefringent crystal 202 and the objective lens 203, as shown in the figure. Figure 1 In the embodiment, the first beam splitter 201 can be a half-transmission half-reflection mirror.

[0078] As an implementation manner, the first beam splitter 201, the birefringent crystal 202 and the objective lens 203 are sequentially arranged on the light propagation path between the probe light generation module 10 and the to-be-detected element 60. At this time, the first probe light generated by the probe light generation module 10 is incident on the birefringent crystal 202 through the first beam splitter 201, is divided into two beams of linearly polarized light with a small included angle and perpendicular polarization directions, and after the two beams of linearly polarized light continue to pass through the objective lens 203, the first polarized light and the second polarized light are formed, and are incident on the surface of the to-be-detected element 60. The first polarized light is reflected by the surface of the to-be-detected element 60 to form the first echo light, and the second polarized light is reflected by the surface of the to-be-detected element 60 to form the second echo light. The first echo light and the second echo light return along the original path, enter the birefringent crystal 202 through the objective lens 203, and after re-combining collinearly in the birefringent crystal 202, are incident on the polarization controller 30 through the first beam splitter 201. It can be understood that after the first echo light and the second echo light reflected by the to-be-detected element 60 re-combine collinearly, the polarization directions of the first echo light and the second echo light remain unchanged.

[0079] In the embodiment, the polarization controller 30 is used to adjust the polarization directions of the first echo light and the second echo light. The first echo light and the second echo light interfere with each other to form the signal light. Specifically, the polarization controller 30 adjusts the polarization direction of the incident combined light, which can simplify the calculation complexity of obtaining the first echo light and the second echo light through the first light intensity distribution information, and improve the detection efficiency and accuracy. In the embodiment, the polarization controller 30 can be a quarter-wave plate, a half-wave plate, or a combination of a quarter-wave plate and a half-wave plate.

[0080] For example, when the first echo light and the second echo light reflected by the to-be-detected element 60 are linearly polarized light with perpendicular polarization directions, and the polarization controller 30 is a quarter-wave plate, when the polarization direction of the combined light and the optical axis plane of the quarter-wave plate form an angle of 45 degrees, the first echo light and the second echo light contained in the combined light are respectively converted into circularly polarized light with different directions of rotation, i.e., left-handed light and right-handed light.

[0081] In this embodiment, the first detection device 40 is used to acquire first light intensity distribution information of the signal light formed by the light generation and modulation device. Specifically, the first detection device 40 includes two or more detectors.

[0082] like Figure 2 As shown, the first detection device 40 includes a first detection area 401. The first detection area 401 refers to the region where the working surface of the first detection device 40, i.e., the photosensitive surface, is projected onto the surface of the element under test 60; that is, the region where the image of the photosensitive surface is formed on the surface under test by the optical device between the first detection device 40 and the element under test 60. It should be noted that... Figure 2 The projection diagram shown is for illustrative purposes only. Other optical devices, such as an objective lens 203, a light-refractive crystal, and a polarization controller 30, are also disposed between the first detection device 40 and the element under test 60. The signal light formed by the first echo and the second echo reflected from the surface under test within the first detection area 401 can be received by the working surface of the first detection device 40. Specifically, since the first detection device 40 includes two or more detectors, the first detection area 401 also includes multiple first detection unit areas, with one detector corresponding to one first detection unit area. At the same time during the detection process, each detector detects the signal light formed by the first echo and the second echo reflected from the surface under test within different first detection unit areas.

[0083] For example, such as Figure 2 As shown, assuming the first detection device 40 includes a first detector 41, a second detector 42, a third detector 43, and a fourth detector 44, where the first detector 41 corresponds to the first detection unit region P1, the second detector 42 corresponds to the first detection unit region P2, the third detector 43 corresponds to the first detection unit region P3, and the fourth detector 44 corresponds to the first detection unit region P4, then at the same time, the first detector 41 is used to detect the signal light formed by the first echo and the second echo reflected back from the test surface 600 in the first detection unit region P1; the second detector 42 is used to detect the signal light formed by the first echo and the second echo reflected back from the test surface 600 in the second detection unit region P2; the third detector 43 is used to detect the signal light formed by the first echo and the second echo reflected back from the test surface 600 in the third detection unit region P3; and the fourth detector 44 is used to detect the signal light formed by the first echo and the second echo reflected back from the test surface 600 in the fourth detection unit region P4.

[0084] In the detection, the first detection area 401 needs to be controlled to scan the surface 600 of the element 60 to be detected, so that the signal light formed by the first echo light and the second echo light reflected by the same detection area of the surface 600 to be detected is received by each detector in turn with the scanning time, that is, the signal light corresponding to the same detection area of the surface 600 to be detected is scanned on the working surface of each detector. For example, when it is needed to detect the defect condition of a preset detection area of the surface 600 to be detected of the element 60 to be detected, the first detection area 401 needs to be controlled to scan the detection area along a preset track, so that each detector can obtain the signal light formed by the first echo light and the second echo light reflected by the detection area.

[0085] Specifically, the manner of controlling the first detection area 401 to scan the surface to be detected of the element 60 to be detected can be that, after the optical path is built, the incident positions of the first polarized light and the second polarized light and the position of the first detection device 40 are kept unchanged, the element 60 to be detected is controlled to move along a preset track, so that the detection spot formed by the first polarized light and the second polarized light on the surface to be detected of the element 60 to be detected scans the surface to be detected, that is, the first detection area 401 corresponding to the first detection device 40 scans the surface to be detected. Of course, in other embodiments of the present application, after the optical path is built and the element 60 to be detected is placed, the element 60 to be detected is kept unchanged, and the incident positions of the first polarized light and the second polarized light and the movement of the first detection area 401 relative to the surface to be detected of the element 60 to be detected are controlled synchronously, so that the first detection area 401 scans the surface to be detected.

[0086] It can be understood that, in the scanning process, in order to enable each detector to receive the signal light corresponding to a preset detection area of the surface of the element 60 to be detected, the arrangement direction of the plurality of first detection unit areas and the scanning direction of the first detection area 401 on the surface of the element 60 to be detected should not be perpendicular. As an optional embodiment, the arrangement direction of the plurality of first detection unit areas is parallel to the scanning direction of the first detection area 401 on the surface of the element 60 to be detected, so that each detector can better receive the signal light corresponding to the preset detection area in the scanning process, thereby improving the detection efficiency.

[0087] Specifically, in the embodiment, the arrangement direction of the first detector 41, the second detector 42, the third detector 43 and the fourth detector 44 is the same as the arrangement direction of the plurality of first detection unit areas, so that the arrangement direction of the first detector 41, the second detector 42, the third detector 43 and the fourth detector 44 is parallel to the scanning direction of the first detection area 401 on the surface of the element 60 to be detected.

[0088] In order to further improve the detection efficiency, as an optional embodiment, the first detection area corresponding to the first detection device 40 is in a strip shape, and the plurality of first detection unit areas included in the first detection area are also in a strip shape. The extension direction of the first detection area is perpendicular to the scanning direction of the first detection area on the surface of the element to be detected 60. In this way, the element area that can be detected by one scanning can be increased, thereby improving the detection efficiency.

[0089] When the surface to be detected of the element to be detected 60 is circular, the first detection area extends along the radial direction of the surface of the element to be detected 60. At this time, the scanning direction of the first detection area on the surface to be detected of the element to be detected 60 is perpendicular to the diameter direction of the surface to be detected.

[0090] During detection, the first polarized light and the second polarized light form a detection light spot on the surface to be detected of the element to be detected 60, and the detection light spot should cover or partially cover the first detection area corresponding to the first detection device 40. As an optional embodiment, in the scanning direction of the first detection area on the surface of the element to be detected 60, the size of the detection light spot is greater than or equal to the size of the first detection area. For example, when the first detection area is in a strip shape, the detection light spot is in a rectangular shape, and when the scanning direction of the first detection area on the surface of the element to be detected 60 is consistent with the width direction of the detection light spot, the width of the detection light spot is greater than or equal to the width of the first detection area.

[0091] The size of the detection light spot being greater than or equal to the size of the first detection area can enable the detectors included in the first detection device 40 to simultaneously obtain the light intensity of the signal light reflected by different first detection unit areas, thereby improving the detection efficiency.

[0092] As an optional way, the above two or more detectors are polarization detectors, each polarization detector is used to detect the intensity of signal light in a specific polarization direction, and the polarization detection directions of different polarization detectors are different. It should be noted that the polarization detection direction refers to the polarization direction of the light that can be detected by the polarization detector. Therefore, the two or more polarization detectors can be used to obtain the intensity of the signal light emitted by the polarization controller 30 in different polarization directions. By detecting the intensity distribution of the signal light in different polarization directions through the two or more polarization detectors, the phase value of the signal light can be further obtained according to the intensity distribution, and the height distribution of the surface of the element to be detected 60 can be obtained according to the phase value of the signal light. It can be understood that the height difference between the positions of the first polarized light and the second polarized light on the element to be detected 60 will change the phase value of the reflected light, and therefore, the height distribution of the surface of the element to be detected 60 will affect the phase distribution of the signal light.

[0093] In the embodiment, the polarization detector can be formed by adding a micro-etching array above the photodetector. The micro-etching array is used to allow the component of the signal light in a specific polarization direction to pass through, so that the signal light in the specific polarization direction is deflected by the micro-etching array and received by the photodetector. The micro-etching array in different polarization detectors has different polarization transmission directions, so that different polarization detectors can obtain the intensity of the signal light in different polarization directions.

[0094] The number of polarization detectors included in the first detection device 40 and the polarization detection direction of each polarization detector can be determined according to the element defect detection requirement. For example, the first detection device 40 can include two polarization detectors, three polarization detectors, or four polarization detectors, etc.

[0095] It should be noted that when the first detection device 40 includes two polarization detectors, the polarization detection directions of the two polarization detectors are perpendicular to each other. At this time, it is not possible to distinguish whether the defect type is a protrusion or a depression (i.e., it is not possible to distinguish the phase sign), and three or more polarization detectors can be used to distinguish the defect type. Therefore, in an embodiment of the present application, the first detection device 40 can include three or more polarization detectors. When the first detection device 40 includes three or more polarization detectors, the three or more polarization detectors include at least a first polarization detector, a second polarization detector, and a third polarization detector. The included angle between the polarization detection direction of the third polarization detector and the polarization detection direction of the first polarization detector is equal to 360° / n, where n represents the number of polarization detectors, and n is an integer greater than or equal to 3. As an optional implementation, the polarization detection direction of the first polarization detector is perpendicular to the polarization detection direction of the third polarization detector, and the included angle between the polarization detection direction of the third polarization detector and the polarization detection direction of the second polarization detector is 45°, which is beneficial to simplify the subsequent phase demodulation.

[0096] For example, in an application scenario of the present application, the first detection device 40 includes four polarization line detectors, and the polarization detection directions are 0°, 45°, 90°, and 135°, as shown in FIG. 2B. Figure 3

[0097] In order to further improve the detection efficiency, in an embodiment of the present application, each polarization detector is a polarization line detector, that is, a polarization line detector array is used to measure the intensity of the signal light in different polarization directions. This is beneficial to increase the detection area of a single sampling and further improve the detection efficiency. Correspondingly, in the embodiment, the size of the detection spot is greater than or equal to the size of the first detection area in the direction perpendicular to the arrangement direction of the first detection unit area, which can increase the detection efficiency.

[0098] ​It can be understood that each polarization line detector is composed of a plurality of polarization detection units. For example, when the working surface of one polarization detection unit is in the shape of a square, i.e., the shape of the corresponding first detection unit region is also in the shape of a square, the working surface of one polarization line detector is a region composed of a plurality of square regions arranged linearly. When the detection region of the to-be-detected element 60 is circular, such as when the to-be-detected element 60 is a wafer, the working surface of the polarization line detector extends along the radial direction of the wafer. Of course, in other embodiments of the present application, each polarization detector can also be composed of one polarization detection unit. Specifically, one polarization detection unit can be composed of one or more micro-etching units above a single photoelectric detection unit, which are also used to make the components of the signal light in a specific polarization direction pass through and be received by the corresponding photoelectric detection unit. It should be noted that the above-mentioned micro-etching array can be composed of a plurality of micro-etching units.

[0099] As another optional mode, the above-mentioned first detection device 40 includes a non-polarization detector and at least one polarization detector. It should be noted that the non-polarization detector refers to a detector capable of obtaining intensity information of a light beam in any polarization direction; the polarization detector refers to a detector capable of obtaining intensity information of a light beam in a specific polarization direction. The number of polarization detectors can be one, and it is assumed that the polarization detection direction of the polarization detector is α. The intensity information of the signal light in the detection region corresponding to the polarization detector and the intensity information of the signal light in the detection region corresponding to the non-polarization detector in the α polarization direction obtained by the non-polarization detector can obtain the intensity information of the signal light in the β polarization direction orthogonal to α in the detection region, so as to obtain the phase information of the signal light in the detection region corresponding to the signal light in the α polarization direction and in the β polarization direction, thereby obtaining the defect condition of the detection region. Of course, the number of polarization detectors can also be two or more. At this time, when the included angle between the polarization detection directions of the two polarization detectors is an acute angle or an obtuse angle, it can be distinguished whether the defect type is a protrusion or a depression.

[0100] In addition, when the first detection device 40 includes a non-polarization detector and at least one polarization detector, in order to improve the detection efficiency, each polarization detector is a polarization line detector, and the non-polarization detector is also a line detector.

[0101] In addition, it can be understood that when the to-be-detected element 60 is detected, the to-be-detected element 60 needs to be placed on the object table 50. As an optional embodiment, as shown in FIG. 6, the object table 50 is provided with a plurality of micro-etching units 51, and the to-be-detected element 60 is placed on the micro-etching units 51. The micro-etching units 51 are used to make the components of the signal light in a specific polarization direction pass through and be received by the corresponding photoelectric detection unit. Figure 1As shown, the detection device 1 provided by the embodiment of the present application further comprises a carrier table 50 for placing the element to be detected 60. Further, in order to realize line scanning of the element to be detected 60, as a scanning mode, the carrier table 50 can be used not only for placing the element to be detected 60 but also for driving the element to be detected 60 to move. Specifically, the carrier table 50 can be an electrically-driven translation table or a manually-driven translation table. Of course, in order to more accurately control the scanning process, an electrically-driven translation table is preferred. In an embodiment of the present application, if an arbitrary point on the placing plane of the carrier table 50 is taken as the origin, a three-dimensional rectangular coordinate system is established, wherein the Z-axis direction is perpendicular to the placing plane, and the carrier table 50 adopts an electrically-driven translation table which can drive the element to be detected 60 to move in the X-axis, Y-axis and Z-axis directions and can drive the element to be detected 60 to rotate in the XY plane. Of course, in other embodiments of the present application, the carrier table 50 can also adopt an electrically-driven translation table with six degrees of freedom.

[0102] It should be noted that in other embodiments of the present application, the carrier table 50 can also be another carrier table 50 configured to adapt to the detection device 1, i.e., not included in the detection device 1.

[0103] In order to facilitate understanding of the technical solution, the working process of the detection device 11 provided by the embodiment will be briefly described below.

[0104] The first polarized light and the second polarized light generated by the first light generating device and having the same propagation direction and the preset shear amount are incident on the detection surface of the element to be detected 60. After being reflected by the element to be detected 60, the first echo light and the second echo light return to the first light generating device, enter the polarization controller 30 after being combined by the light generating device, and are subjected to polarization state processing by the polarization controller 30, then interfere to generate signal light, which is received by the first detection device 40.

[0105] In the embodiment, in order to make the first detection area of the first detection device 40 scan the element to be detected 60, i.e., to make the signal light corresponding to the same preset detection area on the element to be detected 60 be received by each detector included in the first detection device 40, the element to be detected 60 can be moved. Of course, in other embodiments of the present application, other ways can also be adopted.

[0106] Specifically, when the element to be detected 60 moves along the preset track, the first polarized light and the second polarized light scan the element to be detected 60 along the preset track, and the signal light corresponding to the same preset detection area on the element to be detected 60 is sequentially received by each detector in the order of scanning time. In the embodiment, the preset track can be set according to the shape of the detection area of the element to be detected 60, for example, when the detection area is a circular ring, the preset track can be a circular track, and when the detection area is a square, the preset track can be a straight track.

[0107] At this time, in order to make the different detectors included in the first detection device 40 more effectively detect the intensity distribution of the signal light corresponding to the adjacent regions (different positions) of the surface to be detected in the corresponding polarization direction at the same time, the arrangement direction of the working surface of each detector included in the first detection device 40 can be parallel to the scanning direction of the first polarized light and the second polarized light on the element to be detected 60, that is, the arrangement direction of the first detection unit area corresponding to each detector is parallel to the scanning direction of the first polarized light and the second polarized light on the element to be detected 60.

[0108] Further, since the detection is scanning detection, in order to obtain better detection results, it is necessary to set the scanning speed and the sampling frequency of the first detection device 40. The distance scanned by the first detection area of the first detection device 40 within the time interval of the adjacent two samplings of the first detection device 40, that is, the movement distance of the detection light spot formed by the first polarized light and the second polarized light on the element to be detected 60 relative to the element to be detected 60 is the scanning step, and the distance between the centers of the adjacent first detection unit areas should be adapted to the scanning step. Specifically, the distance between the centers of the adjacent first detection unit areas is equal to an integer multiple of the scanning step.

[0109] In order to further improve the detection efficiency, as an embodiment, the distance between the centers of the adjacent first detection unit areas is equal to the scanning step. In this way, each detector included in the first detection device 40 can sequentially detect the intensity distribution of the signal light corresponding to the same detection area of the surface to be detected along with the scanning time, so as to obtain the intensity distribution of the signal light in different polarization directions corresponding to the detection area. After the scanning is completed, the intensity distribution results of the signal light in different polarization directions corresponding to each detection area on the element to be detected 60 can be obtained.

[0110] It can be understood that after the first light intensity distribution information of the signal light corresponding to the preset detection area of the element to be detected 60 is obtained by the first detection device 40, the detection results of the first detection device 40 need to be further processed to obtain the defect distribution data of the element to be detected 60. For the detection equipment 1 provided by the embodiment of the present application, a data processing device can be included for processing the data output by the first detection device 40 to obtain the defect distribution data of the element to be detected 60, or the data output by the first detection device 40 can be processed by another configured data processing device such as a computer.

[0111] Of course, in order to realize online detection, as an optional embodiment, the present detection equipment 1 can also include a first processing device. The first processing device is electrically connected with the first detection device 40 to receive the first light intensity distribution information output by the first detection device 40 online. The control device is used to obtain the defect information of the element to be detected 60 according to the first light intensity distribution information of the signal light.

[0112] Specifically, the first processing device can be a computer, or can also be a data processing circuit module including a chip with a data processing function such as DSP, ARM or FPGA. The scanning detection will obtain the detection data stream output by the first detection device 40, and the first processing device can process the detection data stream output by the first detection device 40 through a preset phase demodulation algorithm to obtain the phase value of the signal light corresponding to each sampling position of the element under test 60. It can be understood that the phase of the signal light received by the first detection device 40 will reflect the phase difference of the two coherent lights, and since the phase difference is proportional to the height difference between the sampling positions corresponding to the two coherent lights, the micro relief at the corresponding sampling position can be obtained according to the phase value of the signal light, that is, the defect information at the corresponding sampling position is obtained.

[0113] Since the transverse shear amount Δa of the first polarized light and the second polarized light incident on the element under test 60 can be less than the general optical system resolution limit, the corresponding two transverse measurement positions are very close, and therefore the detection device 1 can achieve high detection accuracy in the longitudinal direction (perpendicular to the surface of the measured element).

[0114] The following will also take a wafer as an example to illustrate how to process these data to obtain the defect distribution of the wafer surface. It can be understood that the detection data stream output by the first detection device 40 contains the intensity distribution of the signal light corresponding to each sampling position on the wafer in different polarization directions. According to the intensity distribution of the signal light corresponding to each sampling position in different polarization directions, the phase value of the signal light corresponding to each sampling position is calculated, so as to obtain the phase distribution of the signal light corresponding to all sampling positions on the wafer surface, and then the defect information at each sampling position is calculated according to the phase distribution, so as to obtain the defect distribution data of the wafer surface.

[0115] For example, when the first detection device 40 includes four polarization line detectors, the polarization detection directions are 0 degrees, 45 degrees, 90 degrees and 135 degrees, respectively, and the signal light intensity received by the polarization line detector is taken as I i (r,t), where i=1, 2, 3, 4, respectively corresponding to the light intensity in the polarization direction of 0 degrees, 45 degrees, 90 degrees and 135 degrees, r is the pixel point information corresponding to the line detector, and t is the sampling time. The (r, t) can be converted into the position distribution on the wafer in combination with the specific scanning trajectory. Assuming that the phase of the target signal is represented by , then the signal light phase theoretically satisfies the following formula (1):

[0116]

[0117] According to the above formula, the phase distribution of the signal light detected by the first detection device 40 can be obtained.

[0118] However, the inventors found that, in the actual detection of the wafer by the detection device, although the wafer surface is very smooth when there is no defect in theory, the phase of the signal light is equal to 0, but many factors will cause noise, such as phase error of the optical system, a certain depolarization ratio of the pre-detector, influence of the bandwidth of the light source, and change of the flatness of the wafer surface during the scanning process, etc., which will cause a position-dependent error of the obtained signal light, and the phase zero obtained by direct calculation is no longer located at the phase zero, and there is a slow envelope that does not reflect the change of the height of the wafer surface. For example, Figure 4 A schematic diagram of the phase change with time calculated according to the actual detection data is shown, because there is a convex defect in the detection area of the wafer, the phase presents upward convexity and downward concave, corresponding to the rising and falling edges of the defect respectively, however, the phase still fluctuates at the flat position. These fluctuations at the flat position are the phase noise.

[0119] Therefore, in the actual detection, the phase of the signal light should satisfy the following formula (2):

[0120]

[0121] wherein φ(r, t) represents the phase noise.

[0122] Based on the above analysis, in an embodiment of the present application, the first light intensity distribution information output by the first detection device 40 needs to be pre-processed to eliminate the noise. At this time, the first processing device includes a signal demodulation module, a noise acquisition module and a target information acquisition module. The signal demodulation module is used to acquire initial information of the signal light according to the first light intensity distribution information of the signal light; the noise acquisition module is used to acquire noise information by low-pass filtering the first light intensity distribution information of the signal light; and the target information acquisition module is used to acquire defect information of the to-be-detected element 60 according to the initial information and the noise information.

[0123] The initial information includes initial phase information of the signal light. Specifically, taking the case that the first detection device 40 includes four polarization linear detectors and the polarization detection directions are 0 degree, 45 degree, 90 degree and 135 degree as an example, the initial phase information of the signal light can be calculated according to the above formula (1).

[0124] The noise information includes noise phase information. The noise phase information can be obtained by demodulating the phase after low-pass filtering the first light intensity distribution information of the signal light.

[0125] Specifically, the target information obtaining module includes a target phase obtaining sub-module and a defect information obtaining sub-module. The target phase obtaining sub-module is configured to obtain target phase information by performing difference processing on the initial phase information and the noise phase information. That is, as shown in the following formula (3), the target phase information can be obtained by subtracting the noise phase information φ(r, t) in the formula (2) from the obtained initial phase information φ(r, t). Figure 5 Figure 4 Figure 6 It can be seen that, by the above pre-processing, the influence of noise on the obtained phase distribution result can be effectively removed, and the accuracy of the detection result can be improved. Further, the defect information at each sampling position can be calculated according to the phase distribution, and the defect distribution data of the wafer surface can be obtained.

[0126] The defect information obtaining sub-module is configured to obtain the defect information of the to-be-tested element 60 according to the target phase information. As an optional manner, the height difference at the corresponding position on the surface of the to-be-tested element 60 can be calculated according to the target phase information of the signal light, so as to obtain the defect information of the to-be-tested element 60. As another optional manner, the target information obtaining module can further include a defect standard library, which includes a plurality of preset phase information and corresponding preset defect information, and is configured to determine the corresponding relationship between the phase information and the defect information. At this time, the defect information obtaining sub-module is specifically configured to search in the defect standard library according to the target phase information, obtain the corresponding preset defect information, and thus obtain the defect information of the to-be-tested element 60. That is, the defect information found in the defect standard library based on the target phase information is taken as the defect information of the to-be-tested element 60.

[0127] For example, the corresponding relationship between the phase of the signal light and the surface height of the to-be-tested element 60 can be obtained by a calibration method in advance. The specific process can be as follows: a series of height standard pieces (such as 10 nanometers, 20 nanometers, 30 nanometers, etc.) are made, and the corresponding phase distribution is directly measured to obtain a phase-height corresponding relationship curve according to the measurement data. In actual measurement, the corresponding height information is found according to the obtained target phase value. In this way, the height distribution of the to-be-tested surface can be more accurately obtained, and the calculation process of the defect information can be simplified, and the detection efficiency can be improved.

[0128] The modules included in the first processing device can be implemented by software code, and at this time, the modules can be stored in the memory of the first processing device. Alternatively, the modules included in the first processing device can also be implemented by hardware circuit such as an integrated circuit chip.

[0129] As an optional embodiment, as shown in Figure 7 ​​​As shown, the detection device 2 provided by the embodiment comprises a second detection device 72 in addition to the light generation modulation device and the first detection device 40. The second detection device 72 is configured to collect scattered light on the surface of the element 60 to be detected and obtain second light intensity distribution information of the scattered light. Thus, the scattered light detection channel is added on the basis of the detection channel of the differential interference method, i.e., the detection channel of the first detection device 40, so that the bright field and dark field combined detection is realized.

[0130] The defect detection principle of the light scattering method is as follows: the laser obliquely enters the surface of the element 60 to be detected at a certain position. When there is no defect on the surface of the element 60 to be detected, the element 60 to be detected exhibits a mirror effect, and the incident light is reflected from the other side at the same angle. When there is a defect on the surface of the element 60 to be detected, the incident light is scattered by the defect, and the scattered light is transmitted in various directions above the surface of the element 60 to be detected. The scattered light intensity is proportional to the defect size. Therefore, the defect distribution and defect size information of the surface of the element 60 to be detected can be obtained by detecting the scattered light above the surface of the element 60 to be detected.

[0131] The detection device 2 provided by the embodiment further comprises a second light generation device 71. The second light generation device 71 is configured to generate second detection light and make the second detection light scattered on the surface of the element 60 to be detected to form the scattered light. Specifically, the second detection light generated by the second light generation device 71 obliquely enters a preset detection area on the surface of the element 60 to be detected at a preset angle. When there is a defect in the preset detection area, the incident second detection light is scattered at the defect to form the scattered light.

[0132] In the embodiment, the detection device 2 further comprises a reflecting cup (not shown in the figure) configured to collect the scattered light on the surface to be detected. The second detection light generated by the second light generation device 71 forms a point light spot on the element 60 to be detected. The second detection device 72 is a photodiode or a photomultiplier tube.

[0133] Since the emission direction of the scattered light is arbitrary, the position of the second detection device 72 can be set as needed. As an optional mode, the scattered light detection channel can be in the same optical path as the signal light detection channel. For example, as shown in FIG. 6, the second detection light emitted by the second light generation device 71 obliquely enters the surface of the element 60 to be detected from below the objective lens at a preset incident angle. The preset angle can be set as needed, for example, the preset incident angle can be 72°. Figure 7

[0134] ​It should be noted that the spot shape and size of the second probe light on the measured element 60 can be adjusted as needed, for example, by setting a beam expander and shaper 74 in the light transmission path of the second light generating device 71. In this embodiment, the spot of the second probe light on the measured element 60 can be adjusted to a point spot, so as to facilitate the collection of scattered light by the reflecting cup, and to reduce the interference of scattered light in adjacent areas. In order to distinguish from the signal light, the wavelength of the second probe light emitted by the second light generating device 71 can be different from the wavelength of the first probe light emitted by the first light generating device. It can be understood that the wavelengths of the first probe light, the first polarized light, the second polarized light, and the signal light are consistent. In addition, in order to reduce the interference of stray light on the first echo light and the second echo light, a second beam splitter 73 is also needed to be added in the light receiving channel to divide the light received by the objective lens 203 into two parts for two-channel signal receiving, as shown in Figure 7 Meanwhile, a first filter 75 is added in front of the first detection device 40 to filter out the scattered light in this receiving channel. A second filter 76 is added in front of the second detection device 72 to filter out the interference light, and the scattered light transmits through the second filter 76 and converges to the second detection device 72 through the converging lens 77.

[0135] It should be noted that the position of the second beam splitter 73 can be set as needed, for example, it can be set in the light transmission path between the first beam splitter 201 and the polarization controller 30, or it can also be set in the light transmission path between the objective lens 203 and the birefringent crystal 202.

[0136] In this embodiment, the first light generating device and the second light generating device 71 form probe light spots on the surface of the measured element 60, respectively. Correspondingly, the signal light reflected by the surface of the measured element 60 is detected by the first detection device 40, and the scattered light scattered by the surface of the measured element 60 is detected by the second detection device 72. That is, the differential interference method detection channel and the scattered light detection channel are controlled to detect the measured element 60, respectively.

[0137] Specifically, based on the definition of the first detection area, the second detection device 72 also includes a second detection area. The second detection device 72 is used to obtain the scattered light scattered by the surface of the measured element 60 in the second detection area.

[0138] The way of detecting the measured element 60 by the scattered light detection channel can be that the measured element 60 is divided into a plurality of detection areas, and the spot formed by the second probe light on the surface of the measured element 60 and the second detection area are sequentially made to cover each detection area, so as to sequentially obtain the scattered light formed by each detection area on the surface of the measured element 60.

[0139] It should be noted that when the shape of the surface to be measured is circular, the second detection area can also be controlled to move along the diameter direction of the surface to be measured while scanning the surface to be measured.

[0140] In addition, since the scattered light detection channel is added, the embodiment further includes a second processing device different from the first processing device. The first detection device 40 and the second detection device 72 are both electrically connected to the second processing device. The second processing device is configured to obtain first defect information of the element to be measured 60 according to the first light intensity distribution information of the signal light obtained by the first detection device 40, obtain second defect information of the element to be measured 60 according to the second light intensity distribution information of the scattered light obtained by the second detection device 72, and obtain target defect information of the element to be measured 60 based on the first defect information and the second defect information. Specifically, the second processing device can also be a computer, or can also be a data processing circuit module including a chip with a data processing function such as DSP, ARM or FPGA.

[0141] The process of obtaining the first defect information of the element to be measured 60 according to the first light intensity distribution information can refer to the processing process of the first processing device, which will not be described here.

[0142] The first defect information includes first defect position information and first defect size information, and the second defect information includes second defect position information and second defect size information. The specific process of obtaining the target defect information of the element to be measured 60 based on the first defect information and the second defect information can be: defect accumulation is performed on the first defect information and the second defect information, and common defect merging judgment is performed to obtain the defect information of the element to be measured 60. Since there can be position errors during defect detection, the positions obtained by different channels for the same defect can be slightly different, so defect judgment is needed when merging defects. The specific defect judgment method is as follows: first, traverse all the defects obtained by a single channel, and take any one of the defects obtained by a single channel (such as a light scattering method channel) as a current defect; the distance between the current defect and each defect obtained by another channel (such as a differential interference method channel) is calculated in turn; it is judged whether the distance is less than a preset threshold value, if the distance is less than the preset threshold value, it is considered that the two defects corresponding to the distance are the same defect, and merging processing is performed, that is, the two defects are merged into one. The next defect obtained by the single channel is taken as the current defect, and the distance calculation and distance judgment processes are repeated until the judgment of all defects obtained by the single channel is completed.

[0143] The selection of the preset threshold value can be measured through multiple experiments. For example, different threshold values can be selected for merging judgment, and the value closest to the actual merging result is taken as the preset threshold value.

[0144] In summary, the detection device provided by the embodiment of the present application realizes polarization state judgment of signal light based on the first detection device 40, and can realize element defect detection through line scanning, obtain phase distribution of the signal light, obtain optical path difference of the two coherent lights according to the phase distribution of the signal light, and thus obtain the tiny fluctuation of the surface of the element to be detected 60, so as to realize high-precision detection of defects of the element to be detected 60 in the longitudinal direction (perpendicular to the direction of the measured surface), such as high-precision detection of pit type defects, and the detection device has good reliability, high stability, and fast detection speed. In addition, the phase noise filtering method is proposed according to the noise rule in wafer detection, so as to improve the signal-to-noise ratio of the detection result, that is, to further improve the defect detection precision.

[0145] Further, by adding a scattered light detection channel on the basis of the differential interference method detection channel, bright field and dark field combined detection is realized, which not only can improve the defect detection precision in the longitudinal direction (perpendicular to the direction of the measured surface), but also can improve the lateral resolution.

[0146] In addition, the embodiment of the present application also provides a defect detection method, which can be applied to the detection device provided by the first embodiment. Of course, in addition to the above-mentioned detection device, it can also be applied to other applicable detection devices. For example, Figure 8 As shown in the figure, the method comprises:

[0147] Step S801, generating first polarized light and second polarized light through light generation modulation device, and making the first polarized light reflect on the measured surface of the element to be detected 60 to form first echo light, and making the second polarized light reflect on the measured surface to form second echo light, wherein the first polarized light and the second polarized light have a preset shear amount between the centers;

[0148] Step S802, making the first echo light and the second echo light interfere through the light generation modulation device to form signal light;

[0149] Step S803, acquiring light intensity information of the signal light along a plurality of different polarization directions through the first detection device 40, or acquiring total light intensity information of the signal light and light intensity information along at least one polarization direction.

[0150] It should be noted that when the first detection device 40 includes two or more polarization detectors, and the polarization detection directions of different polarization detectors are different, the light intensity information of the signal light along multiple different polarization directions can be obtained. When the first detection device 40 includes a non-polarization detector and at least one polarization detector, the total light intensity information of the signal light and the light intensity information along at least one polarization direction can be obtained. The total light intensity information refers to the light intensity information of the signal light obtained by the non-polarization detector. In this embodiment, the light intensity information of the signal light along multiple different polarization directions, or the total light intensity information of the signal light and the light intensity information along at least one polarization direction are taken as the first light intensity distribution information of the signal light.

[0151] Specifically, since the first detection device 40 includes the first detection area, and the first detection area includes multiple first detection unit areas, to obtain the first light intensity distribution information of the signal light corresponding to a detection region on the surface of the to-be-tested element 60, each detector included in the first detection device 40 needs to receive the signal light corresponding to the detection region, and the first detection area needs to scan on the to-be-tested element 60 so that each first detection unit area covers the detection region in turn with the scanning time.

[0152] As an optional mode, the method further includes: controlling the first polarized light and the second polarized light to scan on the to-be-tested surface, and repeating the above steps S802 and S803. That is, in the process that the light spots formed by the first polarized light and the second polarized light on the to-be-tested surface scan on the to-be-tested surface, each scanning region will reflect the first echo light and the second echo light to form the signal light in turn, and meanwhile, the signal light corresponding to each scanning region will be received by the first detection device 40 in turn with the scanning time, so as to obtain the first light intensity distribution information.

[0153] Specifically, the positions of the incident positions of the first polarized light and the second polarized light and the first detection device 40 can be kept unchanged, the to-be-tested element 60 is controlled to move along a preset track by the motorized stage 50 or other actuators, so that the detection light spots formed by the first polarized light and the second polarized light on the surface of the to-be-tested element 60 scan on the to-be-tested element 60, and meanwhile, the first detection area of the first detection device 40 scans on the to-be-tested element 60 with the detection light spots.

[0154] As an optional embodiment, the scanning direction of the first polarized light and the second polarized light on the to-be-tested surface is the same as the arrangement direction of the multiple first detection unit areas.

[0155] As an optional implementation, the step of acquiring the light intensity information of the signal light along multiple different polarization directions by the first detection device, or acquiring the total light intensity information of the signal light and the light intensity information along at least one polarization direction, comprises: sampling the light intensity of the signal light by the first detection device 40, and the scanning distance of the first detection area within the time interval between two adjacent samplings is a scanning step, and the distance between the centers of two adjacent first detection unit areas is equal to an integer multiple of the scanning step.

[0156] As an optional implementation, the distance between the centers of two adjacent first detection unit areas is equal to the scanning step.

[0157] As an optional implementation, the step of controlling the first polarized light and the second polarized light to scan the surface to be measured comprises: controlling the surface to be measured of the measured element 60 to move in a direction opposite to the preset scanning direction. That is, the above-mentioned preset trajectory is opposite to the scanning direction.

[0158] As an optional implementation, when the light generation modulation device comprises a first light source 101 and a beam expanding and shaping device 102, the step of generating the first polarized light and the second polarized light can comprise: generating first detection light by the first light source 101 to form the first polarized light and the second polarized light based on the first detection light; adjusting the spot shape and size of the first polarized light and the second polarized light formed on the surface to be measured of the measured element 60 by the beam expanding and shaping device 102, so that the size of the spot is greater than or equal to the size of the first detection area in the scanning direction of the surface to be measured of the measured element 60 along the first detection area.

[0159] As an optional implementation, the step of controlling the surface to be measured of the measured element 60 to move in a direction opposite to the scanning direction comprises:

[0160] controlling the measured element 60 to rotate around a rotation shaft perpendicular to the surface to be measured;

[0161] The step of controlling the first polarized light and the second polarized light to scan the surface of the measured element 60 further comprises: after the surface to be measured rotates one round around the rotation shaft, or in the process of the surface to be measured rotating around the rotation shaft, controlling the spot formed by the first polarized light and the second polarized light on the surface to be measured to move along the diameter direction of the surface to be measured.

[0162] In this embodiment, after the surface to be measured rotates one round around the rotation shaft, the spot formed by the first polarized light and the second polarized light on the surface to be measured is controlled to move along the diameter direction of the surface to be measured. In this way, the obtained signal light is more stable, thereby increasing the detection accuracy.

[0163] In other embodiments, during the rotation of the surface under test around the axis, controlling the light spots formed by the first polarized light and the second polarized light on the surface under test to move along the diameter direction of the surface under test can increase the detection efficiency.

[0164] In actual testing, to facilitate scanning control, the component under test 60 can be placed on the stage 50, and the stage 50 can be used to move the component under test 60 along a preset trajectory. For example, in a specific application scenario, taking a wafer as an example, the process of controlling the wafer to move along a preset trajectory will be explained.

[0165] Before testing, the wafer is placed on the stage 50, with the center O of the wafer coinciding with the rotation center of the stage 50. The relative position of the first detection device 40 and the wafer is adjusted so that the extension direction of the first detection area is parallel to the wafer radius direction. The Nomarski prism is adjusted so that the deviation direction of the two linearly polarized beams generated by its beam splitting is perpendicular to the extension direction of the first detection area. For example, with the wafer center O as the origin, a system is established as follows: Figure 9 The rectangular coordinate system shown has the extension direction of the first detection zone parallel to... Figure 9 In the y-axis direction, the deviation direction of the two linearly polarized beams with a small included angle emitted from the Nomarski prism is parallel to the x-axis. Figure 9 The x-axis direction in the image is such that the first and second polarized light emitted from the objective lens have polarization along the x-axis. Figure 9 If a preset shearing amount is given along the x-axis, the detection device can detect protrusions or depressions on the surface of the component under test 60 along the x-axis. In other embodiments, the first polarized light and the second polarized light may also have polarization along the x-axis. Figure 9 The preset shearing amount in the y-axis direction, or the preset shearing amount direction of the first polarized light and the second polarized light, has an acute angle with the x-axis.

[0166] During inspection, the wafer can be moved by controlling the stage 50, thereby performing inspections at different locations on the wafer surface and ultimately achieving defect detection across the entire wafer surface. Specifically, when the scanning control process is as follows: after controlling the surface under test to rotate around the axis once, and then controlling the light spots formed by the first and second polarized lights on the surface under test to move along the diameter direction of the surface under test, the wafer can be divided into multiple annular regions. Each annular region corresponds to a scanning trajectory 601, and the multiple scanning trajectories 601 are distributed in concentric circles, such as... Figure 9It should be noted that, in order to avoid missing detection, two adjacent annular regions should be connected or at least have an overlapping area of one to two pixels (relative to the detector). Each annular region includes a plurality of target regions 602, and the shape and size of the target regions 602 are determined by the shape and size of the corresponding first detection area of the first detection device 40. First, the moving stage 50 is controlled to make the light spot emitted by the objective lens cover any one of the target regions 602 in the outermost annular region of the wafer, and at this time, the signal light corresponding to the target region 602 is received by the first detection device 40. Then, the moving stage 50 is controlled to rotate the wafer by one revolution, so that the light spot passes through the other target regions 602 of the outermost annular region of the wafer in sequence according to the preset scanning track 601, that is, the outermost annular region of the wafer is scanned. After the scanning is completed, each detector included in the first detection device 40 can obtain the signal light detection data corresponding to the outermost annular region of the wafer.

[0167] For example, when the first detection device 40 includes four polarization line detectors, namely polarization line detector A, polarization line detector B, polarization line detector C and polarization line detector D, each target region 602 can be divided into four adjacent sub-regions, and each sub-region corresponds to the first detection unit area of one polarization line detector, that is, the signal light reflected by each sub-region is received by the corresponding polarization line detector. For example, it is assumed that the target region 602 includes a first sub-region, a second sub-region, a third sub-region and a fourth sub-region. During the process of controlling the surface to be detected to rotate around the rotation shaft by one revolution, if at the current time, the first sub-region in the current target region 602 corresponds to the first detection unit area of the polarization line detector A, the second sub-region corresponds to the first detection unit area of the polarization line detector B, the third sub-region corresponds to the first detection unit area of the polarization line detector C, and the fourth sub-region corresponds to the first detection unit area of the polarization line detector D. Then at the next scanning time, the second sub-region in the current target region 602 corresponds to the first detection unit area of the polarization line detector A, the third sub-region corresponds to the first detection unit area of the polarization line detector B, the fourth sub-region corresponds to the first detection unit area of the polarization line detector C, and the first sub-region in the next target region 602 corresponds to the first detection unit area of the polarization line detector D. In this way, the polarization line detector A, the polarization line detector B, the polarization line detector C and the polarization line detector D can sequentially obtain the signal light corresponding to the current annular region according to the scanning time.

[0168] The surface to be measured is controlled to rotate around the rotation shaft for one revolution, so that the light spots formed by the first polarized light and the second polarized light on the surface to be measured scan the outermost annular region of the wafer surface, then the wafer is moved along the diameter direction by the carrier table 50, that is, the light spots formed by the first polarized light and the second polarized light on the wafer surface are moved in the direction opposite to the moving direction of the wafer, so that the light spots cover the target region in the next annular region of the wafer surface. Then the wafer is controlled to rotate around the rotation shaft for one revolution by the carrier table 50, and the scanning of the annular region is completed. In this way, the detection of the entire wafer surface is completed.

[0169] In combination of the signal measurement speed and the measurement transverse resolution, the embodiment of the present application adopts line scanning measurement. Considering that the light emitted by a general light source is a circular light spot, additional beam shaping is required for shaping into a line beam. However, the detection equipment has a low requirement on the light source intensity, and can realize the detection of the line region on the surface of the component by using circular spot illumination and line detector. Of course, a line light source matched with the detection region of the line detector can also be used for detection.

[0170] As an optional implementation, after the step S803 is performed, the method further includes: acquiring defect information of the component to be measured 60 according to the first light intensity distribution information of the signal light by the first processing device.

[0171] As an optional implementation, the acquisition of the defect information of the component to be measured 60 according to the first light intensity distribution information of the signal light includes: acquiring initial information of the signal light according to the first light intensity distribution information; performing low-pass filtering processing on the first light intensity distribution information to acquire noise information; and acquiring the defect information of the component to be measured 60 according to the initial information and the noise information.

[0172] As an optional implementation, the initial information includes initial phase information of the signal light, and the noise information includes noise phase information. The acquisition of the defect information of the component to be measured 60 according to the initial information and the noise information includes: performing difference processing on the initial phase information and the noise phase information to acquire target phase information; and acquiring the defect information of the component to be measured 60 according to the target phase information.

[0173] As an optional implementation, the acquisition of the defect information of the component to be measured 60 according to the target phase information includes: searching for corresponding preset defect information in a preconfigured defect standard library according to the target phase information to obtain the first defect information of the surface of the component to be measured 60, wherein the defect standard library includes a corresponding relationship between a plurality of preset phase information and corresponding preset defect information.

[0174] In another embodiment of the present application, the detection device can also be a dual-channel detection device, i.e., as described in the first embodiment above, including a scattered light detection channel and a differential interference method detection channel. Specifically, as shown in Figure 7 the detection device includes a second light generating device 71, a second detection device 72, and a second processing device.

[0175] At this time, the above defect detection method includes: scanning the surface to be measured by the first light generating device to generate first polarized light and second polarized light, and obtaining the first light intensity distribution information of the surface to be measured by the first detection device 40; after or before scanning the surface to be measured by the first light generating device to generate first polarized light and second polarized light, scanning the surface to be measured by the second light generating device 71 to generate second detection light, and obtaining the second light intensity distribution information of the scattered light of the surface to be measured by the second detection device 72; obtaining the first defect information of the measured element 60 according to the first light intensity distribution information by the second processing device, obtaining the second defect information of the measured element 60 according to the second light intensity distribution information, and obtaining the target defect information of the measured element 60 based on the first defect information and the second defect information.

[0176] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific implementation process of the above-described method can refer to the corresponding process in the above-described device embodiment, which will not be described here.

[0177] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A detection device, characterized by The method comprises: a first detection device for obtaining first light intensity distribution information of signal light, the first detection device comprising two or more detectors, each of the two or more detectors being a polarization detector, and different polarization detection directions of the polarization detectors being different, or the two or more detectors comprising a non-polarization detector and at least one polarization detector; each of the detectors sequentially scans the surface of the to-be-detected element, so that signal light corresponding to a same detection area of the surface of the to-be-detected element is sequentially received by each of the detectors in a time sequence; the first detection device comprises a first detection area, the first detection area being used for scanning the surface of the to-be-detected element, the first detection area comprising a plurality of first detection unit areas, and an arrangement direction of the plurality of first detection unit areas being not perpendicular to a scanning direction of the first detection area on the surface of the to-be-detected element, and each of the detectors being used for detecting signal light reflected by the surface of the to-be-detected element corresponding to different first detection unit areas.

2. The detection device of claim 1, wherein, At the same time, signal light corresponding to a plurality of detection areas of the surface of the to-be-detected element is received by each of the detectors.

3. The detection device of claim 1, wherein, The arrangement direction of the plurality of first detection unit areas is parallel to the scanning direction of the first detection area on the surface of the to-be-detected element.

4. The detection device of claim 1, wherein, The first detection area is in a strip shape, and an extension direction of the first detection area is perpendicular to the scanning direction of the first detection area on the surface of the to-be-detected element.

5. The detection device of claim 4, wherein, When the surface of the to-be-detected element is circular, the first detection area extends along a radial direction of the surface of the to-be-detected element, and the scanning direction of the first detection area on the surface of the to-be-detected element is perpendicular to a diameter direction of the surface.

6. A method of detection, characterized in that The method is applied to the detection device according to any one of claims 1 to 5, and the method comprises: obtaining light intensity information of signal light along a plurality of different polarization directions by using a first detection device, or obtaining total light intensity information of the signal light and light intensity information along at least one polarization direction; controlling each of the detectors to sequentially scan the surface of the to-be-detected element, so that signal light corresponding to a same detection area of the surface of the to-be-detected element is sequentially received by each of the detectors in a time sequence.

7. The detection method according to claim 6, characterized in that, When the first detection device comprises a first detection area, and the first detection area comprises a plurality of first detection unit areas, the controlling each of the detectors to sequentially scan the surface of the to-be-detected element also causes the plurality of first detection unit areas to detect different detection areas at the same time.

8. The detection method according to claim 6 or 7, characterized in that, When the first detection device comprises a first detection area, the first detection area comprises a plurality of first detection unit areas, an arrangement direction of the plurality of first detection unit areas is not perpendicular to a scanning direction of the first detection area on the surface of the to-be-detected element, and each of the detectors is used for detecting signal light of the surface of the to-be-detected element corresponding to different first detection unit areas, the controlling each of the detectors to sequentially scan the surface of the to-be-detected element, so that signal light corresponding to a same detection area of the surface of the to-be-detected element is sequentially received by each of the detectors in a time sequence, comprises: The step of controlling each detector to scan the surface to be measured in a scanning direction and repeatedly acquiring, by each detector, the light intensity information of the signal light of the surface to be measured corresponding to each first detection unit area during the scanning.

9. The detection method according to claim 8, characterized in that, The step of controlling each detector to scan the surface to be measured in a scanning direction and repeatedly acquiring, by each detector, the light intensity information of the signal light of the surface to be measured corresponding to each first detection unit area during the scanning. The step of controlling each detector to scan the surface to be measured in a scanning direction and repeatedly acquiring, by each detector, the light intensity information of the signal light of the surface to be measured corresponding to each first detection unit area during the scanning.

10. The method of claim 7, wherein, The step of controlling each detector to scan the surface to be measured in a scanning direction and repeatedly acquiring, by each detector, the light intensity information of the signal light of the surface to be measured corresponding to each first detection unit area during the scanning.

11. The detection method according to claim 10, characterized in that, The step of controlling each detector to scan the surface to be measured in a scanning direction and repeatedly acquiring, by each detector, the light intensity information of the signal light of the surface to be measured corresponding to each first detection unit area during the scanning.

12. The detection method of claim 11, wherein, The step of controlling each detector to scan the surface to be measured in a scanning direction and repeatedly acquiring, by each detector, the light intensity information of the signal light of the surface to be measured corresponding to each first detection unit area during the scanning.

13. The method of claim 7, wherein, The step of controlling each detector to scan the surface to be measured in a scanning direction and repeatedly acquiring, by each detector, the light intensity information of the signal light of the surface to be measured corresponding to each first detection unit area during the scanning.

14. The detection method according to claim 13, characterized in that, The step of controlling each detector to scan the surface to be measured in a scanning direction and repeatedly acquiring, by each detector, the light intensity information of the signal light of the surface to be measured corresponding to each first detection unit area during the scanning. The step of controlling each detector to scan the surface to be measured in a scanning direction and repeatedly acquiring, by each detector, the light intensity information of the signal light of the surface to be measured corresponding to each first detection unit area during the scanning. The step of controlling each detector to scan the surface to be measured in a scanning direction and repeatedly acquiring, by each detector, the light intensity information of the signal light of the surface to be measured corresponding to each first detection unit area during the scanning.

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