Detection device
By combining a linear light source with a deflecting prism, dark field illumination is formed, which solves the problem that the background brightness is higher than the defect brightness due to the pattern arrangement in dark field detection, and realizes high signal-to-noise ratio detection of small-sized defects.
Patent Information
- Application Number
- CN202323039819.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-10
- Publication Date
- 2026-02-27
- Estimated Expiration
- 2033-11-10
AI Technical Summary
In dark field inspection, the background brightness of objects with patterns is higher than that of small-sized defects due to the arrangement of the patterns, causing the defect scattering signal to be submerged in the background brightness and unable to be identified.
By setting the incident angle between the linear light source and the object to be inspected, the image cannot be formed. A deflecting prism is used to change the direction of the light to form dark field illumination, which increases the relative brightness of small-sized defects. A coupling lens group is used to limit the light convergence angle, and a polarizer is used to adjust the azimuth angle of the light to reduce interference from diffracted light.
Under dark illumination conditions, periodic patterns do not form images, which significantly improves the signal-to-noise ratio for detecting small-sized defects and increases the relative brightness and detection sensitivity of small-sized defects.
Smart Images
Figure CN223955454U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of optical detection, in particular to a detection device. BACKGROUND
[0002] Optical detection is generally divided into bright field detection and dark field detection, wherein the bright field detection is limited by the diffraction limit, and the minimum detection defect is the Airy spot radius, and the dark field detection is based on Rayleigh scattering or Mie scattering of small size particles, and as long as the scattering signal of the small size defect can be detected, the goal of improving the detection sensitivity can be achieved, and the minimum size of the dark field detection can be easily less than the Airy spot radius under the bright field.
[0003] However, for the patterned object to be detected, due to the arrangement of the pattern on the object to be detected, the light in the dark field illumination can be diffracted, so that part of the diffraction light directly enters the imaging system, thereby forming the effect of bright field illumination.
[0004] And the effect of bright field illumination in such patterned object to be detected makes the brightness of the dark field background higher than that of the small size defect, so that the signal value of the defect scattering is submerged in the background brightness and cannot be recognized. CONTENT OF THE INVENTION
[0005] The embodiment of the present application provides a detection device, which is used for setting the incidence angle between the linear light source and the object to be detected, so that the pattern in the object to be detected cannot be imaged, thereby improving the relative brightness of the small size defect, and improving the detection signal-to-noise ratio of the small size defect.
[0006] The embodiment of the present application provides a detection device, which comprises:
[0007] At least one detection module, the detection module comprises a linear light source, the emergent light of the linear light source and the normal line of the object to be detected form a first angle, and the first angle comprises 60° to 90°;
[0008] A turning prism is arranged along the direction of the emergent light of the linear light source, and the turning prism is used for changing the direction of the emergent light of the linear light source, so that the emergent chief ray of the deflected linear light source is perpendicular to the light emitting surface of the linear light source;
[0009] When the emergent light of the turning prism irradiates to the object to be detected, the dark field illumination is formed on the surface of the object to be detected, so that the imaging device in the detection device detects the defect in the object to be detected according to the scattering information of the object to be detected in the dark field illumination, and the object to be detected is provided with a periodic pattern.
[0010] Preferably, if the to-be-detected object is provided with a plurality of parallel transverse cutting lines and a plurality of parallel longitudinal cutting lines, the projection of the chief ray of the linear light source on the plane of the to-be-detected object forms a second angle with a target cutting line, the second angle is 30° to 60°, and the target cutting line is any one of the transverse cutting lines or the longitudinal cutting lines.
[0011] Preferably, the linear light source irradiates the to-be-detected object in a critical illumination manner.
[0012] Preferably, the angle between the light-emitting surface of the linear light source and the chief ray of the linear light source is a third angle, wherein the third angle and the second angle satisfy a first formula:
[0013] The first formula includes: .
[0014] wherein, the third angle is the second angle is and the ratio of the spot size of the linear light source on the to-be-detected object to the size of the light-emitting surface of the linear light source is
[0015] Preferably, the turning prism includes a first surface and a second surface along the direction of the outgoing light rays of the linear light source, wherein the angle between the first surface and the second surface is , and the refractive index of the turning prism is n.
[0016] After the outgoing light rays of the linear light source pass through the turning prism, the deflection angle of the outgoing light rays of the linear light source relative to the light-emitting surface of the linear light source is , the angle , the angle and the refractive index n satisfy a second formula:
[0017] The second formula includes: .
[0018] Preferably, the detection module further includes:
[0019] A coupling mirror group, configured to receive the outgoing light rays of the turning prism and limit the convergence angle of the outgoing light rays of the turning prism to 0° to 15°.
[0020] Preferably, the convergence angle is 0° to 5°.
[0021] Preferably, the coupling mirror group comprises a first lens group, an aperture stop and a second lens group, the first lens group is used for converting the outgoing light rays of the turning prism into parallel light beams, the aperture stop is used for limiting the spot diameter of the parallel light beams, and the second lens group is used for converging the outgoing light rays passing through the aperture stop to the object to be detected.
[0022] Preferably, the detection module further comprises:
[0023] a polarizer arranged in coincidence with the aperture stop, the polarizer being used for adjusting the polarization azimuth angle of the outgoing light rays of the linear light source.
[0024] Preferably, the linear light source comprises a bar-shaped LED light source, or the linear light source comprises a linearly arranged optical fiber and a light source connected to the optical fiber.
[0025] From the above technical solutions, it can be seen that the embodiments of the present application have the following advantages:
[0026] Because the linear light source in the embodiments of the present application is incident on the object to be detected at a first angle, wherein the first angle comprises 60° to 90°, the outgoing light rays of the linear light source form a dark field illumination on the surface to be detected when irradiating the object to be detected, and the detection module in the embodiments of the present application is provided with a turning prism along the direction of the outgoing light rays of the linear light source, which is used for improving the brightness of the dark field illumination, so that under the condition of the dark field illumination, the periodic pattern in the object to be detected cannot be imaged, thereby further improving the relative brightness of small-size defects, i.e. improving the detection signal-to-noise ratio of small-size defects. BRIEF DESCRIPTION OF DRAWINGS
[0027] Figure 1 FIG. 1 is a schematic diagram of an embodiment of the detection device in the embodiments of the present application;
[0028] Figure 2 FIG. 2 is a schematic diagram of the first angle and the second angle in the embodiments of the present application;
[0029] Figure 3 FIG. 3 is a schematic diagram of another embodiment of the detection device in the embodiments of the present application;
[0030] Figure 4 FIG. 4 is a schematic diagram of an embodiment of the detection device comprising a plurality of detection modules in the embodiments of the present application;
[0031] Figure 5 FIG. 5 is a schematic diagram of the comparison of the signal-to-noise ratio of small-size defects between the prior art and the present application. DETAILED DESCRIPTION
[0032] The embodiment of the present application provides a detection device, which is used for setting the incidence angle between a linear light source and a to-be-detected object, so that a pattern in the to-be-detected object cannot be imaged, thereby improving the relative brightness of small-size defects, and improving the detection signal-to-noise ratio of the small-size defects.
[0033] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.
[0034] The terms "first", "second", "third", "fourth" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.
[0035] For the convenience of understanding, the detection device in the present application is described below, please refer to Figure 1 One embodiment of the detection device in the present application comprises:
[0036] At least one detection module 10, a to-be-detected object 20, an imaging device 30 and a turning prism 40, wherein the detection module 10 comprises a linear light source 101, the linear light source 101 comprises an LED light source or a linearly arranged optical fiber and a light source connected with the optical fiber.
[0037] Specifically, the to-be-detected object 20 in the present application comprises a wafer, a chip, a mask or a glass screen, and the to-be-detected object is provided with a periodic pattern, such as a periodically arranged dot or a periodically arranged line.
[0038] The imaging device 30 comprises a microscope group or an assembled magnifying imaging device.
[0039] Furthermore, in order to prevent periodic patterns in the object to be inspected from being imaged and to improve the relative brightness of small-sized defects, the linear light source 101 in this embodiment of the application forms a first angle with the normal of the object to be inspected when illuminating the object 20. The first angle includes 60° to 90°, preferably 75°.
[0040] In addition, since the light intensity of the light source decreases as the light emission angle increases, that is, the light intensity of the light source is strongest in the direction perpendicular to the surface of the light source. In order to ensure high brightness of dark field illumination, this application embodiment also provides a deflection prism 40 along the direction of the emitted light of the linear light source to change the direction of the emitted main light of the linear light source, so that the emitted main light of the deflected linear light source is perpendicular to the light emission surface of the linear light source.
[0041] It should be noted that when the linear light source 101 illuminates the object to be tested 20 at a first angle, a dark field illumination is formed on the surface of the object to be tested 20, so that the imaging device 30 can detect defects in the object to be tested based on the scattering information of the object to be tested in the dark field illumination.
[0042] Because the linear light source in this embodiment is incident on the object to be inspected at a first angle, wherein the first angle includes 60° to 90°, the emitted light from the linear light source forms a dark field illumination on the surface to be inspected when illuminating the object to be inspected. In addition, the detection module in this embodiment is provided with a deflecting prism along the direction of the emitted light from the linear light source to enhance the brightness of the dark field illumination. Under the dark field illumination conditions, the periodic patterns in the object to be inspected cannot be imaged, thereby further improving the relative brightness of small-sized defects, that is, improving the detection signal-to-noise ratio of small-sized defects.
[0043] Furthermore, based on Figure 1 In the described embodiment, when the periodic pattern in the object to be detected consists of multiple parallel horizontal cutting lines and multiple parallel vertical cutting lines, this application further provides that the projection of the emitted light from the linear light source onto the plane of the object to be detected forms a second angle with the target cutting line in the object to be detected. This second angle includes 30° to 60°, and the target cutting line is any one of the horizontal or vertical cutting lines. For ease of understanding... Figure 2 A schematic diagram of the second angle is provided.
[0044] Preferably, the second angle in this application is 45°, which minimizes the interference of the cutting line in the object to be inspected on the main light emitted by the linear light source. Furthermore, by setting the first and second angles, the diffraction image of the periodic pattern in the object to be inspected can be further reduced, thereby improving the relative brightness of small-sized defects.
[0045] As an optional embodiment, in order to form a high-brightness narrow and strong illumination on the surface of the object to be detected, the linear light source 101 in the embodiment adopts a critical illumination mode to irradiate the object to be detected. The critical illumination refers to the illumination of the linear light source after the imaging system on the surface of the object to be detected. The illumination mode can form a narrow and strong illumination on the surface of the object to be detected.
[0046] Further, in order to ensure the uniformity of the critical illumination, as an optional mode, the light path can be set according to the Scheimpflug principle. Specifically, in the embodiment, the following is set:
[0047] The angle between the light emitting surface of the linear light source and the chief ray of the linear light source is a third angle The emergent ray of the linear light source forms a second angle with the target cutting line in the object to be detected And the third angle and the second angle satisfy the first formula:
[0048] The first formula includes: Wherein, The ratio of the spot size of the linear light source on the object to be detected to the size of the light emitting surface of the linear light source.
[0049] Because the light path in the embodiment follows the Scheimpflug principle, the uniformity of the illumination of the linear light source on the surface of the object to be detected is improved.
[0050] As another optional embodiment, the third angle In the embodiment can be directly set to be equal to the second angle That is, M = 1, so as to further improve the uniformity of the illumination.
[0051] Further, in order to make the chief ray of the exit of the turning prism perpendicular to the light emitting surface of the linear light source, as an optional embodiment, the turning prism in the embodiment includes a first surface and a second surface along the direction of the emergent ray of the linear light source, wherein the angle between the first surface and the second surface is The refractive index of the turning prism 40 is n;
[0052] The deflection angle of the chief ray of the exit of the linear light source after the turning prism relative to the light emitting surface of the linear light source is Then the deflection angle The angle And the refractive index n satisfy the second formula:
[0053] The second formula includes: .
[0054] For the convenience of understanding, the following examples are given: assuming that the angle between the outgoing chief ray of the linear light source and the light emitting surface of the linear light source before passing through the turning prism is , and the angle between the outgoing chief ray of the linear light source and the light emitting surface of the linear light source after passing through the turning prism is , then the deflection angle = - .
[0055] That is, the outgoing chief ray of the linear light source changes from not perpendicular to the light emitting surface of the linear light source to perpendicular to the light emitting surface of the linear light source after passing through the turning prism.
[0056] Therefore, the turning prism 40 in the present application can improve the light brightness and light uniformity of critical illumination.
[0057] Further, in order to avoid the diffraction light of the cutting line entering the imaging device 30, the coupling mirror group 50 can be further provided in the embodiment of the present application, wherein the coupling mirror group 50 is used to receive the outgoing light of the turning prism 40 and limit the convergence angle of the outgoing light of the turning prism 40 to between 0° and 15°, and preferably the range of the size of the convergence angle is between 0° and 5°.
[0058] As an optional embodiment, the coupling mirror group 50 in the embodiment of the present application includes a first lens group 501, an aperture stop 502 and a second lens group 503, the first lens group 501 is used to convert the outgoing light of the turning prism 40 into a parallel light beam, the aperture stop 502 is used to limit the spot diameter of the parallel light beam, and the second lens group 503 is used to converge the outgoing light passing through the aperture stop to the object to be detected, thereby avoiding the diffraction light of the cutting line entering the imaging device 30 under the premise of saving cost.
[0059] Further, in order to reduce the energy of the diffraction light in the dark field illumination, a polarizer 60 can also be provided at the position of the aperture stop 502, the polarizer 60 is used to adjust the orientation angle of the outgoing light of the first lens group 501 to reduce the energy of the diffraction light in the dark field illumination, for the convenience of understanding, Figure 3 a schematic diagram of a detection device including a linear light source 101, a polarizer 60, a turning prism 40 and a coupling mirror group 50 (including a first lens group 501, an aperture stop 502 and a second lens group 503) is given.
[0060] In order to ensure the uniformity of the illumination, as an optional embodiment, the embodiment of the present application preferably comprises m detection modules, the m is a positive integer, and the light spots of the linear light sources in the m detection modules at least partially overlap in the object to be detected, Figure 4 A schematic diagram of the detection device comprising multiple detection modules is given.
[0061] As an optional embodiment, in order to ensure the overlapping degree of the light spots of the linear light sources in the m detection modules in the object to be detected, the m detection modules can be arranged to be symmetrically distributed in space.
[0062] For the purpose of comparison, Figure 5 The annular dark field illumination effect in the prior art (left) and the illumination effect of the present application (right) are given. For the same area, the periodic structure of the wafer is imaged under the prior art dark field illumination, resulting in a low relative brightness of small size defects, that is, a low signal-to-noise ratio. The right figure obviously has no periodic pattern, the background is almost 0, and the relative brightness of small size defects is obviously improved, that is, the signal-to-noise ratio is obviously improved. The signal-to-noise ratio of small size defects is increased from 12 in the prior art to 61.5 in the present application, and the signal-to-noise ratio is increased by 5 times.
[0063] The above-described embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A detection device, characterized in that, The application relates to a detection device for detecting defects in a target object, comprising: at least one detection module, wherein the detection module comprises a linear light source, and an angle between an outgoing light ray of the linear light source and a normal line of the target object is a first angle, and the first angle is 60-90 degrees; a turning prism arranged along a direction of the outgoing light ray of the linear light source, and the turning prism is used for changing a direction of an outgoing chief ray of the linear light source, so that the outgoing chief ray of the deflected linear light source is perpendicular to a light-emitting surface of the linear light source; when the outgoing light ray of the turning prism irradiates the target object, dark field illumination is formed on a surface of the target object, and an imaging device in the detection device detects defects in the target object according to scattering information of the target object in the dark field illumination, wherein the target object is provided with a periodic pattern.
2. The detection device of claim 1, wherein, If a plurality of parallel transverse cutting lines and a plurality of parallel longitudinal cutting lines are arranged in the target object, a projection of the outgoing chief ray of the linear light source on a plane of the target object forms a second angle with a target cutting line, the second angle is 30-60 degrees, and the target cutting line is any one of the plurality of parallel transverse cutting lines or the plurality of parallel longitudinal cutting lines.
3. The detection device of claim 2, wherein, The linear light source irradiates the target object in a critical illumination mode.
4. The detection device of claim 3, wherein, An included angle between the light-emitting surface of the linear light source and the outgoing chief ray of the linear light source is a third angle, wherein the third angle and the second angle satisfy a first formula: The first formula includes: ; wherein, is the third angle, is the second angle, is the ratio of the spot size of the linear light source on the object to be detected to the size of the light emitting surface of the linear light source.
5. The detection device of claim 1, wherein, The turning prism comprises a first surface and a second surface along the direction of the outgoing light rays of the linear light source, wherein the included angle between the first surface and the second surface is , and the refractive index of the turning prism is n. The deflection angle of the light rays of the linear light source after passing through the turning prism relative to the light emitting surface of the linear light source is , the included angle , the included angle and the refractive index n satisfy a second formula: The second formula includes: .
6. The detection device of claim 5, wherein, The detection module further comprises: a coupling mirror group, which is used for receiving the outgoing light ray of the turning prism and limiting a convergence angle of the outgoing light ray of the turning prism to 0-15 degrees.
7. The detection device of claim 6, wherein, The convergence angle ranges from 0 to 5 degrees.
8. The detection device of claim 6, wherein, The coupling mirror group comprises a first lens group, an aperture stop and a second lens group, the first lens group is used for converting the outgoing light ray of the turning prism into a parallel light beam, the aperture stop is used for limiting a spot diameter of the parallel light beam, and the second lens group is used for converging the outgoing light ray passing through the aperture stop to the target object.
9. The detection device of claim 8, wherein, The detection module further comprises: a polarizer arranged in coincidence with the aperture stop, and the polarizer is used for adjusting a polarizing azimuth angle of the outgoing light ray of the linear light source.
10. The detection device according to any one of claims 1 to 9, characterized in that The linear light source comprises a bar-shaped LED light source, or the linear light source comprises linearly arranged optical fibers and a light source connected with the optical fibers.