CN111208144B - Defect detection system and defect detection method - Google Patents

Abstract

The invention discloses a defect detection system and a defect detection method. The defect detection system includes a light source module for emitting a first detection beam; a beam splitting module for splitting the first detection beam to obtain multiple second detection beams; The second detection beam is incident on multiple positions on the surface of the sample to be detected, and multiple reflected beams are obtained after being reflected by the sample to be detected, and the multiple reflected beams carry surface information of multiple positions on the surface of the sample to be detected; the detection module is used to receive and Detect multiple reflected light beams to obtain the surface information of the sample to be tested; the surface information includes surface flatness information and surface inclination information; the imaging module is connected to the detection module to receive surface information, and according to the surface information, the surface of the sample to be tested is processed. imaging. By obtaining the surface information of the sample to be tested, one or more imaging is performed on the surface of the sample to be tested according to the surface information, so as to ensure that the entire surface of the sample to be tested can be clearly imaged.

Description

A defect detection system and defect detection method

technical field

Embodiments of the present invention relate to the technical field of defect detection, and in particular, to a defect detection system and a defect detection method.

Background technique

When performing defect detection on the surface to be measured, it is often limited by the limited focal depth of the lens. In order to achieve high-resolution sub-micron defect imaging, real-time automatic focusing is required. The autofocus technology used for lens focusing can be divided into coaxial epi-light scheme and off-axis oblique light scheme according to the direction of the focused beam. The coaxial epi-light solution requires a prism to reflect the focusing beam into the defect detection lens. In high-precision applications, the introduction of a prism outside the lens will cause serious astigmatism, which is not worth the candle. The off-axis tilted light solution does not need to multiplex the defect detection lens for its focusing beam, so it is suitable for high-precision defect detection scenarios.

Focusing and leveling sensors can be used in the existing technology. The principle is to adjust the focus based on moiré fringes formed by oblique light passing through two groups of gratings. However, the broadband light source used in this method will interfere with defect detection and cannot be applied to defect detection technology. Or a triangulation-based laser displacement sensor can be used for real-time autofocus of the lens and provide a reference beam. But these two methods can only measure single-point focal plane.

In practical applications, due to the large target surface size of the large target surface camera, the measurement field of view is also relatively large, generally tens of millimeters. In the entire measurement field of view, the surface topography of the measured sample may fluctuate far beyond the focal depth of the lens. Therefore, single-point focal plane measurement cannot accurately characterize the best focal plane of the lens, and cannot clearly image the entire measurement surface.

Contents of the invention

In view of this, an embodiment of the present invention provides a defect detection system and a defect detection method to solve the problem that the single-point focal plane measurement in the prior art cannot accurately characterize the best focal plane of the lens and cannot clearly image the entire measurement surface question.

In a first aspect, an embodiment of the present invention provides a defect detection system, including:

a light source module, configured to emit the first detection light beam;

A beam splitting module, located on the propagation path of the first detection beam, for splitting the first detection beam to obtain multiple second detection beams; multiple second detection beams are incident on the sample to be detected Multiple positions on the surface are reflected by the sample to be detected to obtain multiple reflected beams, and the multiple reflected beams carry surface information of multiple positions on the surface of the sample to be detected;

The detection module is located on the propagation path of the multiple reflected light beams, and is used to receive and detect the multiple reflected light beams, and obtain the position of the sample to be detected by analyzing the spot position changes of the multiple reflected light beams on the detection surface. Surface information; the surface information includes surface flatness information and surface inclination information;

An imaging module, connected to the detection module, is used to receive the surface information, and perform at least one focused imaging on the surface of the sample to be detected according to the surface information.

Optionally, the defect detection system also includes a Fourier lens;

The Fourier lens is located on the propagation path of the multiple reflected beams, and is used to converge the multiple reflected beams to obtain multiple converged beams;

The detection module is located on the propagation path of the multiple converged light beams, and is used to receive and detect the multiple converged light beams, and obtain the to-be-detected surface information of the sample.

Optionally, the imaging module includes an imaging lens, an imaging camera and a processing unit;

The imaging lens is connected to the imaging camera;

The processing unit is respectively connected with the detection module and the imaging camera, and is used to receive the surface information, and control the imaging camera and the imaging lens to perform detection on the surface of the sample to be detected according to the surface information. Focus imaging at least once.

Optionally, the beam splitting module includes a diffraction grating, and the diffraction grating is used to split the first detection beam to obtain multiple second detection beams with the same energy.

In the second aspect, the embodiment of the present invention also provides a defect detection method, using the above-mentioned defect detection system, including:

Acquiring surface information of the sample to be tested; the surface information includes surface flatness information and surface inclination information;

performing at least one focused imaging on the surface of the sample to be detected according to the surface information.

Optionally, multiple second detection light beams are incident on multiple positions on the surface of the sample to be detected, corresponding to multiple sub-surfaces on the surface of the sample to be detected;

Carrying out at least one focus imaging on the surface of the sample to be detected according to the surface information, including:

determining sub-highest value information and sub-lowest value information in each of said sub-surfaces;

The maximum value information among the plurality of sub-maximum value information is the surface maximum value information, and the minimum value information of the plurality of sub-minimum value information is the surface minimum value information;

When the difference between the surface highest value information and the surface minimum value information and the focal depth of the imaging module satisfy a first preset relationship, calculate the optimal focal plane information of the surface of the sample to be detected, according to the The optimal focal plane information is used to perform optimal focal plane focusing imaging on the surface of the sample to be detected;

When the difference between the surface highest value information and the surface minimum value information and the focal depth of the imaging module satisfy a second preset relationship, the imaging module is controlled to focus on the surface of the sample to be detected multiple times imaging.

Optionally, calculating the optimal focal plane information of the surface of the sample to be detected includes:

calculating surface average height information according to the surface maximum value information and the surface minimum value information;

The focal plane corresponding to the surface average height information is used as the optimal focal plane.

Optionally, calculating the optimal focal plane information of the surface of the sample to be detected includes:

Respectively acquiring the first focal plane information corresponding to the center area of the surface of the sample to be detected and the second focal plane information corresponding to the edge area of the surface of the sample to be detected;

According to the first focal plane information and the second focal plane information, different weighting coefficients are used to calculate the optimal focal plane information of the surface of the sample to be detected, wherein the weighting coefficient of the first focal plane information is greater than the specified The weighting coefficient of the second focal plane information.

Optionally, controlling the imaging module to perform multiple focus imaging on the surface of the sample to be detected, including:

Determine the number of in-focus imaging according to the difference between the surface highest value information and the surface minimum value information and the focal depth of the imaging module;

According to the number of times of focus imaging, the imaging module is moved, and the imaging module is controlled to perform multiple focus imaging on the surface of the sample to be detected; wherein, during each focus imaging, the highest value in the field of view of the imaging module is the same as The difference information between the lowest values is less than or equal to the focal depth of the imaging module.

Optionally, when the difference H between the surface maximum value information and the surface minimum value information and the focal depth DOF of the imaging module satisfy H<2*DOF, the surface maximum value information and the surface minimum value information The difference between and the focal depth of the imaging module satisfy a first preset relationship;

When the difference H between the surface highest value information and the surface minimum value information and the depth of focus DOF of the imaging module satisfy H≥2*DOF, the difference between the surface highest value information and the surface minimum value information The value and the focal depth of the imaging module satisfy a second preset relationship.

The defect detection system provided by the embodiment of the present invention splits the first detection beam emitted by the light source module by setting a beam splitting module to obtain multiple second detection beams, and the multiple second detection beams are incident on the surface of the sample to be detected. Multiple reflected beams are obtained after being reflected by the sample to be detected, and the multiple reflected beams carry surface information of multiple positions on the surface of the sample to be detected; the detection module is used to obtain the surface information of the sample to be detected according to the multiple reflected beams, and the imaging module It is used for performing at least one focus imaging on the surface of the sample to be detected according to the surface information. In this way, when the surface flatness of the sample to be tested meets the set flatness requirements or the surface inclination of the sample to be tested is small, only one focus imaging of the surface of the sample to be tested can ensure a clear image of the entire surface to be imaged. When the surface flatness of the sample to be tested does not meet the set flatness requirements or the surface of the sample to be tested has a large inclination, multiple focus imaging can be performed on the surface of the sample to be tested according to the surface information of the sample to be tested to ensure that the entire sample to be tested is obtained. Sharp images of imaging surfaces. Based on the clear image of the surface to be imaged, the defect degree of the surface to be imaged is detected to ensure high detection accuracy; moreover, the defect detection system provided by the embodiment of the present invention detects the surface to be imaged by multiple second detection beams, and at least based on the surface information One-time focus imaging can solve the problems of low focus detection efficiency caused by single-beam detection and single-focus plane focus imaging in the prior art, and the problem of inability to distinguish defocus or sample tilt.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is a structural schematic diagram of a defect detection system in the prior art

2 is a schematic structural diagram of a defect detection system provided by an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of another defect detection system provided by an embodiment of the present invention;

FIG. 4 is a schematic flowchart of a defect detection method provided by an embodiment of the present invention;

Fig. 5 is a schematic diagram of a plurality of second detection beams provided by an embodiment of the present invention for detecting multiple positions on the surface of a sample to be detected;

FIG. 6 is a schematic flowchart of another defect detection method provided by an embodiment of the present invention;

FIG. 7 is a schematic diagram of a multi-focus imaging provided by an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be fully described below through specific implementation in combination with the drawings in the embodiments of the present invention. Apparently, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts, All fall within the protection scope of the present invention.

Fig. 1 is a schematic structural diagram of a defect detection system in the prior art. As shown in Fig. 1, in the existing defect detection system, the light beam emitted by the light source 11 is incident on the central area of the sample 12 to be detected, and passes through the sample 12 to be detected. After being reflected, it enters the imaging unit 13, and the imaging unit 13 can only perform single-focus plane imaging on the central area of the sample 12 to be inspected to obtain a clear image of the central area of the sample 12 to be inspected. When the surface of the sample 12 to be tested is relatively large, and the surface flatness of the sample 12 to be tested is relatively poor, or the surface of the sample 12 to be tested is inclined to a large degree, single focal plane imaging cannot obtain a clear image of the entire surface of the sample to be tested, and cannot be treated. Imaging surfaces for precise defect detection.

Based on the above technical problems, an embodiment of the present invention provides a defect detection system, including: a light source module, used to emit the first detection beam; a beam splitting module, located on the propagation path of the first detection beam, for detecting The beam is split to obtain multiple second detection beams; the multiple second detection beams are incident on multiple positions on the surface of the sample to be detected, and after being reflected by the sample to be detected, multiple reflected beams are obtained, and the multiple reflected beams carry the sample to be detected The surface information of multiple positions on the surface; the detection module is located on the propagation path of the multiple reflected beams, and is used to receive and detect the multiple reflected beams, and by analyzing the position changes of the multiple reflected beams on the detection surface, the detected The surface information of the sample; the surface information includes surface flatness information and surface inclination information; the imaging module is connected with the detection module to receive the surface information, and perform at least one focus imaging on the surface of the sample to be detected according to the surface information. By adopting the above-mentioned technical solution, by setting the beam splitting module to split the first detection beam emitted by the light source module, multiple second detection beams are obtained, and the multiple second detection beams are incident on multiple positions on the surface of the sample to be tested. After detecting the reflection of the sample, multiple reflected beams are obtained, and the multiple reflected beams carry the surface information of multiple positions on the surface of the sample to be tested; the detection module is used to obtain the surface information of the sample to be tested according to the spot position changes of the multiple reflected beams on the detection surface , the imaging module is used to perform at least one focused imaging on the surface of the sample to be detected according to the surface information. In this way, when the surface flatness of the sample to be tested meets the set flatness requirements or the surface inclination of the sample to be tested is small, only one focus imaging of the surface of the sample to be tested can ensure a clear image of the entire surface to be imaged. When the surface flatness of the sample to be tested does not meet the set flatness requirements or the surface of the sample to be tested has a large inclination, multiple focus imaging can be performed on the surface of the sample to be tested according to the surface information of the sample to be tested to ensure that the entire sample to be tested is obtained. Sharp images of imaging surfaces. Based on the clear image of the surface to be imaged, the defect degree of the surface to be imaged is detected to ensure high detection accuracy; moreover, the defect detection system provided by the embodiment of the present invention detects the surface to be imaged by multiple second detection beams, and at least based on the surface information One-time focus imaging can solve the problems of low focus detection efficiency caused by single-beam detection and single-focus plane focus imaging in the prior art, and the problem of inability to distinguish defocus or sample tilt.

The above is the core idea of the present invention, and the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Fig. 2 is a schematic structural diagram of a defect detection system provided by an embodiment of the present invention. As shown in Fig. 2 , the defect detection system provided by an embodiment of the present invention includes a light source module 21, a beam splitting module 22, a detection module 23 and an imaging module 24 The light source module 21 is used to emit the first detection beam 211; the beam splitting module 22 is located on the propagation path of the first detection beam 211, and is used to split the first detection beam 211 to obtain multiple second detection beams 221; A second detection beam is incident on multiple positions on the surface of the sample 25 to be detected, and multiple reflected beams 222 are obtained after being reflected by the sample 25 to be detected, and the multiple reflected beams 222 carry surface information of multiple positions on the surface of the sample 25 to be detected; The module 23 is located on the propagation path of the multiple reflected beams 222, and is used to receive and detect the multiple reflected beams 222, and obtain the surface information of the sample to be detected by analyzing the position changes of the multiple reflected beams 222 on the detection surface; The information includes surface flatness information and surface inclination information; the imaging module 24 is connected to the detection module 23 (not shown in the figure) for receiving surface information and performing at least one focus imaging on the surface of the sample to be inspected according to the surface information.

Exemplarily, as shown in FIG. 2, the beam splitting module 22 is located on the propagation path of the first detection beam 211, and is used to split the first detection beam 211 to obtain a plurality of second detection beams 221, such that the plurality of first detection beams The second detection beam can be incident on multiple positions on the surface of the sample 25 to be detected, and after being reflected by the sample 25 to be detected, multiple reflected beams 222 are obtained, and the multiple reflected beams 222 carry surface information of multiple positions on the surface of the sample 25 to be detected. The surface information described above may include surface flatness information and surface inclination information, and the surface flatness information can be understood as the height difference between each point on the surface of the sample 25 to be detected and the set surface; the surface inclination information can be understood as The inclination angle information of the surface of the sample 25, the inclination angle here can be understood as the angle between the surface of the sample 25 to be detected and the set surface, and the set surface can be a horizontal plane or a vertical plane, which is not limited in the embodiment of the present invention.

Further, the detection module 23 receives and detects the multiple reflected beams 222, and obtains the surface information of the sample to be detected according to the spot position changes of the multiple reflected beams 222 on the detection surface. The detection module 23 can be a CCD or a CMOS detector. The embodiment of the invention does not limit this.

Further, the imaging module 24 is connected with the detection module 23 (not shown in the figure), receives the surface information of the sample 25 to be inspected, and performs at least one focus imaging on the surface of the sample 25 to be inspected according to the surface information. Specifically, when the surface flatness of the sample to be tested 25 satisfies the set flatness requirements well, or the surface inclination of the sample to be tested is small, it is only necessary to perform a focus imaging on the surface of the sample to be tested 25 to ensure that the entire sample to be tested is obtained. Clear image of the surface; when the surface flatness of the sample to be tested is poor and does not meet the set flatness requirements, or the surface of the sample to be tested has a large inclination, the surface information of the sample to be tested can be used according to the surface information of the sample to be tested. Multiple focus imaging at different positions ensures a clear image of the entire surface to be imaged. In this way, by performing flatness detection on the imaging surface of the sample to be detected 25, different focus imaging strategies are adopted based on the flatness information to ensure that a clear imaging image of the surface of the sample to be detected 25 is obtained. High degree of detection to ensure high detection accuracy.

To sum up, the defect detection system provided by the embodiment of the present invention splits the first detection beam emitted by the light source module by setting a beam splitting module to obtain multiple second detection beams, and the multiple second detection beams are incident on the sample to be tested Multiple positions on the surface are reflected by the sample to be detected to obtain multiple reflected beams, and the multiple reflected beams carry surface information of multiple positions on the surface of the sample to be detected; The surface information of the sample to be detected is obtained by changing, and the imaging module is used to perform at least one focus imaging on the surface of the sample to be detected according to the surface information. In this way, when the surface flatness of the sample to be tested meets the set flatness requirements or the surface inclination of the sample to be tested is small, only one focus imaging of the surface of the sample to be tested can ensure a clear image of the entire surface to be imaged. When the surface flatness of the sample to be tested does not meet the set flatness requirements or the surface of the sample to be tested has a large inclination, multiple focus imaging can be performed on the surface of the sample to be tested according to the surface information of the sample to be tested to ensure that the entire sample to be tested is obtained. Sharp images of imaging surfaces. Based on the clear image of the surface to be imaged, the defect degree of the surface to be imaged is detected to ensure high detection accuracy; moreover, the defect detection system provided by the embodiment of the present invention detects the surface to be imaged by multiple second detection beams, and at least based on the surface information One-time focus imaging can solve the problems of low focus detection efficiency caused by single-beam detection and single-focus plane focus imaging in the prior art, and the problem of inability to distinguish defocus or sample tilt.

Optionally, FIG. 3 is a schematic structural diagram of another defect detection system provided by an embodiment of the present invention. As shown in FIG. The lens 26 is located on the propagation path of the multiple reflected beams 222, and is used to converge the multiple reflected beams 222 to obtain multiple converged beams 261; the detection module 23 is located on the propagation path of the multiple converged beams 261, and is used to receive and detect Multiple beams of converging light beams 261, and the surface information of the sample 25 to be detected is obtained according to the position changes of the spots of the multiple beams of converging reflected beams 261 on the detection surface.

Exemplarily, by comparing Fig. 2 and Fig. 3, it can be known that by adding a Fourier lens 26, the multi-beam reflected beam 222 is converged by the Fourier lens 26 to obtain a multi-beam converged beam 261, and at this time, the multi-beam converged beam 261 The area covered by the light spot is smaller than the area covered by the light spot of the multiple reflected light beams 222. At this time, the detection module 23 with a smaller area can be used to receive the multiple converged light beams 261. On the one hand, it is beneficial to save the cost of the detection module 23, thereby reducing the overall defect detection. The cost of the system; on the other hand, it can reduce the volume of the entire defect detection system, which is conducive to the realization of a miniaturized and highly integrated defect detection system, which is in line with the development trend of miniaturization and high integration of the defect detection system.

Further, since the reflected light beam 222 carries the inclination information of the surface of the sample 25 to be detected, the reflected light beam 222 undergoes Fourier transform after passing through the Fourier lens 26, and no additional displacement error will be generated at this time, ensuring that the detection module 23 can accurately detect The surface information of the sample 25 to be detected will not generate additional displacement errors due to the addition of lenses, ensuring high detection accuracy.

Optionally, continue to refer to Fig. 2 and Fig. 3, in the defect detection system provided by the embodiment of the present invention, the imaging module 24 may include an imaging lens 241, an imaging camera 242 and a processing unit 243; wherein, the imaging lens 241 and the imaging camera 242 is connected; the processing unit 243 is respectively connected with the detection module 23 and the imaging camera 242, and is used to receive the surface information, and control the imaging camera 242 and the imaging lens 241 to perform at least one focused imaging on the surface of the sample 25 to be inspected according to the surface information.

Specifically, the imaging module 24 can include an imaging lens 241, an imaging camera 242, and a processing unit 243; the imaging lens 241 can be an imaging lens with high magnification and high numerical aperture, so as to ensure that the surface of the sample 25 to be tested can be clearly imaged; the imaging camera 242 can It is a large target surface imaging camera, which ensures that the surface of the sample 25 to be detected with a relatively large area can be imaged; the processing unit 243 is respectively connected with the detection module 23 and the imaging camera 242, and is used to adjust the imaging camera 242 and the imaging lens according to the surface information The imaging angle or imaging position of 241 is used to perform at least one focused imaging on the surface of the sample 25 to be detected, so as to realize clear imaging of the surface of the sample 25 with detection.

Further, multiple second detection light beams 221 may be located on the same plane; the imaging camera 242 may be a line array imaging camera; and the detection module 23 may be a line array detector.

Exemplarily, the multiple second detection beams 221 split by the beam splitting module 22 may be located on the same plane, and correspondingly, the imaging camera 242 may be a line array imaging camera; the detection module 23 may be a line array detector, On the one hand, it can reduce the large divergence angle of the beam caused by the non-coplanar beam, and the larger divergence angle will further cause a large displacement error, which affects the accuracy of flatness detection; on the other hand, the imaging of the line array imaging camera is clear The accuracy is higher, and the detection sensitivity of the linear array detector is higher, which further improves the detection accuracy of the surface flatness of the sample to be detected.

Further, the imaging lens 241 can be an imaging lens with high magnification and high numerical aperture, its imaging magnification is a, and the numerical aperture is NA, wherein, a≥3, NA≥0.18; the line array imaging camera can be a large target surface line array imaging The size of the target surface of the camera is L, where L≥60mm. Reasonably set the imaging magnification and numerical aperture of the imaging lens 241 to ensure that the surface of the sample 25 to be tested can be clearly imaged; reasonably set the size of the target surface of the line array imaging machine to ensure that a larger area of the surface of the sample 25 to be tested can be realized for imaging.

Optionally, the beam splitting module 22 provided in the embodiment of the present invention includes a diffraction grating for splitting the first detection beam 211 to obtain multiple second detection beams 221 . A diffraction grating is used as the beam splitting module 22 to ensure a simple structure of the beam splitting module. Further, through the optimization of the surface microstructure of the diffraction grating, the phase adjustment of the first detection beam 211 can be realized to ensure that multiple second detection beams 221 with the same energy can be obtained, and the multiple second detection beams 221 with the same energy to be detected Sample 25 is tested for flatness to ensure high detection accuracy; and, the defect detection system provided by the embodiment of the present invention detects the surface to be imaged through multiple second detection beams, and performs at least one focus imaging based on surface information, which can solve the problem of existing problems. In the technology, single-beam detection and single-focus plane focus imaging bring about low focus detection efficiency, and problems such as defocus or sample tilt cannot be distinguished.

Based on the same inventive concept, an embodiment of the present invention also provides a defect detection method. As shown in FIG. 4, FIG. 4 is a schematic flowchart of a defect detection method provided by an embodiment of the present invention. As shown in FIG. 4, the defect detection method provided by an embodiment of the present invention includes:

S110. Acquire surface information of the sample to be detected; the surface information includes surface flatness information and surface inclination information.

Exemplarily, the surface information can include surface flatness information and surface inclination information, and the surface flatness information can be understood as the height difference between each point on the surface of the sample to be detected and the set surface; the surface inclination information can be understood as Detect the inclination angle information of the sample surface. The inclination angle here can be understood as the angle between the surface of the sample to be detected and the set surface. The set surface can be a horizontal plane or a vertical plane, which is not limited in the embodiment of the present invention.

S120. Perform at least one focus imaging on the surface of the sample to be detected according to the surface information.

Exemplarily, by first acquiring the surface information of the sample to be tested, the surface information may include surface flatness information or surface inclination information, when the surface flatness of the sample to be tested meets the set flatness requirements or the surface inclination of the sample to be tested When <100urad, only one focus imaging on the surface of the sample to be tested can ensure a clear image of the entire surface to be imaged; when the surface flatness of the sample to be tested does not meet the set flatness requirements or the surface inclination of the sample to be tested When >100urad, multiple focus imaging can be performed on the surface of the sample to be tested according to the surface information of the sample to be tested to ensure a clear image of the entire surface to be imaged. Based on the clear image of the surface to be imaged, the defect degree of the surface to be imaged is detected to ensure high detection accuracy; and, the defect detection method provided in the embodiment of the present invention uses multiple second detection beams to detect the surface to be imaged, and based on the surface information, at least One-time focus imaging can solve the problems of low focus detection efficiency caused by single-beam detection and single-focus plane focus imaging in the prior art, and the problem of inability to distinguish defocus or sample tilt.

Exemplarily, FIG. 5 is a schematic diagram of a plurality of second detection beams provided by an embodiment of the present invention for detecting multiple positions on the surface of the sample to be detected. As shown in FIG. 5 , multiple second detection beams 221 are incident on the Multiple positions on the surface of the sample 25 , position A, position B and position C are exemplarily shown in the figure, respectively corresponding to multiple sub-surfaces aa', bb' and cc' on the surface of the sample to be tested. Wherein each sub-surface can be understood as a position where a second detection light beam 221 is incident on the surface of the sample 25 to be detected, position A can be the focus point of sub-surface aa', position B can be the focus point of sub-surface bb', and position C It can be the focusing point of the sub-surface cc', where position B is the focusing point of the central field of view of the imaging lens, DOF is the focal depth range of the central field of view of the imaging lens, and 244 is the optical axis of the imaging lens. On the basis of the above embodiments, FIG. 6 is a schematic flowchart of another defect detection method provided by the embodiment of the present invention. As shown in FIG. 6, the defect detection method provided by the embodiment of the present invention includes:

S210. Obtain surface information of the sample to be detected; the surface information includes surface flatness information and surface inclination information.

S220. Determine sub-highest value information and sub-lowest value information in each of the sub-surfaces.

S230. The maximum value information among the plurality of sub-maximum value information is the surface maximum value information, and the minimum value information of the plurality of sub-minimum value information is the surface minimum value information.

Exemplarily, as shown in FIG. 5 , when the surface of the sample to be tested is a curved surface with large surface undulations, multiple second detection beams 221 hit three positions on the surface of the sample to be tested, respectively position A, At position B and position C, the sub-surfaces aa', bb' and cc' are measured by multiple second detection beams 221, the surface information of each sub-surface can be obtained, and the sub-highest value information and sub-lowest value information of each sub-surface can be determined. value information. Taking Figure 5 as an example, the camera target surface of the imaging lens is set as the reference surface (not shown in the figure), and the height value of the point closest to the reference surface in each subsurface is the sub-highest value information of the subsurface, and each subsurface The height value of the point farthest from the reference surface in the surface is the sub-minimum information of the sub-surface. According to the sub-maximum value information and sub-minimum value information of each sub-surface, the surface maximum value information and surface minimum value information of the entire object to be imaged can be determined, wherein the surface maximum value information can be understood as the maximum value information among multiple sub-maximum value information , the surface minimum value information can be understood as the minimum value information of multiple sub-minimum value information.

S240. When the difference between the surface highest value information and the surface minimum value information and the focal depth of the imaging module satisfy a first preset relationship, calculate the optimal focal plane information of the surface of the sample to be detected, according to The optimal focal plane information performs optimal focal plane focused imaging on the surface of the sample to be detected.

Exemplarily, when the difference H between the surface highest value information and the surface minimum value information and the depth of focus DOF of the imaging module satisfy H<2*DOF, the difference between the surface highest value information and the surface minimum value information and The depth of focus of the imaging module satisfies the first preset relationship; at this time, a clear image of the entire surface of the sample to be tested can be achieved by focusing once.

Furthermore, due to the different topological structures of the surface of the sample to be detected, the focal plane position of the central field of view is not necessarily the optimal focal plane position of the entire surface of the sample to be detected. Compared with the traditional single-point focusing scheme, the embodiment of the present invention adopts Multiple second detection beams measure the height information of multiple positions. Based on multiple height information, the global optimal focal plane of the entire surface of the sample to be detected can be effectively evaluated, and the optimal focal plane of the surface of the sample to be detected can be further optimized through the optimal focal plane. Focus imaging can further improve the imaging clarity, facilitate defect detection on the surface of the sample to be tested, and improve detection accuracy.

Optionally, determining the optimal focal plane information on the surface of the sample to be detected may include multiple feasible implementations, and two feasible implementations are described below:

Optionally, calculating the optimal focal plane information of the surface of the sample to be detected may include:

Calculate surface average height information according to surface maximum value information and surface minimum value information;

The focal plane corresponding to the surface average height information is taken as the optimal focal plane.

Exemplarily, the surface maximum value information and the surface minimum value information of the sample to be detected can be determined according to the above-mentioned embodiment, the surface average height information is calculated according to the surface maximum value information and the surface minimum value information, and the plane where the surface average height is located is used as the plane to be detected Focus on the focal plane of the sample, and the obtained focal plane is the optimal focal plane of the sample to be tested.

Optionally, calculating the optimal focal plane information of the surface of the sample to be detected may include:

Respectively acquiring the first focal plane information corresponding to the center area of the surface of the sample to be detected and the second focal plane information corresponding to the edge area of the surface of the sample to be detected;

According to the first focal plane information and the second focal plane information, different weighting coefficients are used to calculate the optimal focal plane information of the surface of the sample to be detected, wherein the weighting coefficient of the first focal plane information is greater than the weighting coefficient of the second focal plane information.

Exemplarily, the first focal plane information corresponding to the central area of the surface of the sample to be tested and the second focal plane information corresponding to the edge area of the surface of the sample to be tested are obtained respectively, wherein the first focal plane information can be the information corresponding to the central area of the sample surface to be tested The height information of the first focal plane, wherein the second focal plane information may be the height information of the second focal plane corresponding to the edge region of the surface of the sample to be detected. Further, using different weighting coefficients for the first focal plane information and the second focal plane information to calculate the optimal focal plane information on the surface of the sample to be detected, wherein the weighting coefficient of the first focal plane information is greater than the weighting coefficient of the second focal plane information, For example, the weighting coefficient of the first focal plane information can be 70%, and the weighting coefficient of the second focal plane information can be 30%. The height information corresponding to the first focal plane is multiplied by 70%, and the weighting coefficient corresponding to the second focal plane The height information is multiplied by 30% to calculate the height information corresponding to the optimal focal plane, and then the plane where the height information corresponding to the optimal focal plane is located is used as the focal plane of the sample to be tested for focusing, and the obtained focal plane is the Optimal focal plane for the sample.

S250. When the difference between the highest value information on the surface and the lowest value information on the surface and the focal depth of the imaging module meet a second preset relationship, control the imaging module to perform multiple measurements on the surface of the sample to be detected. secondary focus imaging.

Exemplarily, when the difference H between the surface highest value information and the surface minimum value information and the depth of focus DOF of the imaging module satisfy H≥2*DOF, the difference between the surface maximum value information and the surface minimum value information is equal to The depth of focus of the imaging module satisfies the second preset relationship. At this time, it is necessary to realize clear imaging of the entire surface of the sample to be tested through multiple focusing imaging.

Further, controlling the imaging module to perform multiple focus imaging on the surface of the sample to be detected may include:

Determine the number of in-focus imaging according to the difference between the surface maximum value information and the surface minimum value information and the focal depth of the imaging module;

According to the number of focus imaging, the imaging module is moved, and the imaging module is controlled to perform multiple focus imaging on the surface of the sample to be detected; wherein, during each focus imaging, the difference information between the highest value and the lowest value in the field of view of the imaging module is less than or equal to Depth of focus of the imaging module.

Exemplarily, FIG. 7 is a schematic diagram of a multiple focusing imaging provided by an embodiment of the present invention. As shown in FIG. The focal depth range of the imaging lens corresponding to the partial surface of the sample corresponding to the second detection beam; 244 is the optical axis of the imaging lens 241, and 245 is the measurement field of view range FOV of the imaging lens 241.

Before focusing and imaging multiple times, according to the difference (H1-H2) between the surface maximum value information H1 and the surface minimum value information H2 in the lens FOV and the focal depth DOF of the imaging module, determine the number of focus imaging times n, where n =ceil((H1-H2)/DOF), wherein, ceil() means rounding up, for example, when (H1-H2)/DOF=4.1, n=5. After determining the number of times of focusing and imaging, move the imaging module 24, and then guide the imaging module 24 to perform multiple focusing. The area of each focusing measurement is different. Through multiple focusing traversal detection, and each time focusing and imaging, the imaging module has a clear field of view The difference information between the highest value and the lowest value within is less than or equal to the focal depth of the imaging module, which can realize full-field clear imaging of samples with large surface inclination or curvature changes, and facilitate subsequent defect detection on the surface of the sample to be inspected.

To sum up, the defect detection method provided by the embodiment of the present invention determines the surface maximum value information and the surface minimum value information of the surface of the sample to be detected through the surface information, and according to the difference between the surface maximum value information and the surface minimum value information and When the focal depth of the image module satisfies different preset relationships, different focus imaging strategies can be adopted. Single focus imaging can be based on the optimal focal plane, or multiple focus imaging can be performed on the surface of the sample to be tested, which can achieve steepness and large depth For real-time focus imaging of defective samples, two different focus imaging strategies can ensure clear imaging of the sample to be tested, high focus imaging efficiency, and high defect detection efficiency in subsequent surface defect detection.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here, and that the features of the various embodiments of the present invention may be partially or fully coupled or combined with each other, and may cooperate with each other in various ways and technically driven. Various obvious changes, readjustments, mutual combinations and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention, and the present invention The scope is determined by the scope of the appended claims.

Claims (10)

1. A defect detection system, characterized in that, comprising: a light source module, configured to emit the first detection light beam; A beam splitting module, located on the propagation path of the first detection beam, for splitting the first detection beam to obtain multiple second detection beams; multiple second detection beams are incident on the sample to be detected Multiple positions on the surface are reflected by the sample to be detected to obtain multiple reflected beams, and the multiple reflected beams carry surface information of multiple positions on the surface of the sample to be detected; The detection module is located on the propagation path of the multiple reflected light beams, and is used to receive and detect the multiple reflected light beams, and obtain the position of the sample to be detected by analyzing the spot position changes of the multiple reflected light beams on the detection surface. Surface information; the surface information includes surface flatness information and surface inclination information; an imaging module, connected to the detection module, for receiving the surface information, and performing at least one focus imaging on the surface of the sample to be detected according to the surface information; Multiple beams of the second detection beams in the beam splitting module are incident on multiple positions on the surface of the sample to be detected, corresponding to multiple sub-surfaces on the surface of the sample to be detected; Carrying out at least one focus imaging on the surface of the sample to be detected according to the surface information, including: determining sub-highest value information and sub-lowest value information in each of said sub-surfaces; The maximum value information among the plurality of sub-maximum value information is the surface maximum value information, and the minimum value information of the plurality of sub-minimum value information is the surface minimum value information; When the difference between the surface highest value information and the surface minimum value information and the focal depth of the imaging module satisfy a first preset relationship, calculate the optimal focal plane information of the surface of the sample to be detected, according to the The optimal focal plane information is used to perform optimal focal plane focusing imaging on the surface of the sample to be detected; When the difference between the surface highest value information and the surface minimum value information and the focal depth of the imaging module satisfy a second preset relationship, the imaging module is controlled to focus on the surface of the sample to be detected multiple times imaging. 2. The defect detection system according to claim 1, wherein the defect detection system further comprises a Fourier lens; The Fourier lens is located on the propagation path of the multiple reflected beams, and is used to converge the multiple reflected beams to obtain multiple converged beams; The detection module is located on the propagation path of the multiple converged light beams, and is used to receive and detect the multiple converged light beams, and obtain the to-be-detected surface information of the sample. 3. The defect detection system according to claim 1, wherein the imaging module comprises an imaging lens, an imaging camera and a processing unit; The imaging lens is connected to the imaging camera; The processing unit is respectively connected with the detection module and the imaging camera, and is used to receive the surface information, and control the imaging camera and the imaging lens to perform detection on the surface of the sample to be detected according to the surface information. Focus imaging at least once. 4. The defect detection system according to claim 1, wherein the beam splitting module includes a diffraction grating, and the diffraction grating is used to split the first detection beam to obtain multiple beams with the same energy. Two detection beams. 5. A defect detection method, characterized in that the defect detection system according to any one of claims 1-4 is adopted, comprising: Acquiring surface information of the sample to be tested; the surface information includes surface flatness information and surface inclination information; performing at least one focused imaging on the surface of the sample to be detected according to the surface information. 6. The defect detection method according to claim 5, wherein multiple second detection light beams are incident on multiple positions on the surface of the sample to be detected, corresponding to multiple sub-surfaces on the surface of the sample to be detected; Carrying out at least one focus imaging on the surface of the sample to be detected according to the surface information, including: determining sub-highest value information and sub-lowest value information in each of said sub-surfaces; The maximum value information among the plurality of sub-maximum value information is the surface maximum value information, and the minimum value information of the plurality of sub-minimum value information is the surface minimum value information; When the difference between the surface highest value information and the surface minimum value information and the focal depth of the imaging module satisfy a first preset relationship, calculate the optimal focal plane information of the surface of the sample to be detected, according to the The optimal focal plane information is used to perform optimal focal plane focusing imaging on the surface of the sample to be detected; When the difference between the surface highest value information and the surface minimum value information and the focal depth of the imaging module satisfy a second preset relationship, the imaging module is controlled to focus on the surface of the sample to be detected multiple times imaging. 7. The defect detection method according to claim 6, wherein calculating the optimal focal plane information of the surface of the sample to be detected comprises: calculating surface average height information according to the surface maximum value information and the surface minimum value information; The focal plane corresponding to the surface average height information is used as the optimal focal plane. 8. The defect detection method according to claim 6, wherein calculating the optimal focal plane information of the surface of the sample to be detected comprises: Respectively acquiring the first focal plane information corresponding to the center area of the surface of the sample to be detected and the second focal plane information corresponding to the edge area of the surface of the sample to be detected; According to the first focal plane information and the second focal plane information, different weighting coefficients are used to calculate the optimal focal plane information of the surface of the sample to be detected, wherein the weighting coefficient of the first focal plane information is greater than the specified The weighting coefficient of the second focal plane information. 9. The defect detection method according to claim 6, wherein controlling the imaging module to perform multiple focus imaging on the surface of the sample to be detected comprises: Determine the number of in-focus imaging according to the difference between the surface highest value information and the surface minimum value information and the focal depth of the imaging module; According to the number of times of focus imaging, the imaging module is moved, and the imaging module is controlled to perform multiple focus imaging on the surface of the sample to be detected; wherein, during each focus imaging, the highest value in the field of view of the imaging module is the same as The difference information between the lowest values is less than or equal to the focal depth of the imaging module. 10. The defect detection method according to claim 6, wherein when the difference H between the surface highest value information and the surface minimum value information and the focal depth DOF of the imaging module satisfy H<2*DOF , the difference between the surface highest value information and the surface minimum value information and the focal depth of the imaging module satisfy a first preset relationship; When the difference H between the surface highest value information and the surface minimum value information and the depth of focus DOF of the imaging module satisfy H≥2*DOF, the difference between the surface highest value information and the surface minimum value information The value and the focal depth of the imaging module satisfy a second preset relationship.

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