A defect detection system, objective aberration compensation method, and defect detection method

Abstract

The application discloses a defect detection system, an objective lens aberration compensation method and a defect detection method. If an aberration compensation mode is started, an interferometer is connected to an optical path of the system, an optical reference member is arranged on a roof of the system, light emitted by the interferometer successively passes through an optical modulation device and an objective lens to reach the optical reference member, and then returns to the interferometer along the original path until being reflected to the interferometer, and the reflected light collected by the interferometer can be used to determine an adjustment strategy for the optical modulation device in the system, so that the objective lens aberration compensation is achieved. After the aberration compensation is completed, the system can return to a defect detection mode, at this time, the interferometer is cut out of the optical path of the system, the optical reference member is removed from the optical path, and a sample to be measured is arranged on the objective lens. The defect detection module can detect defects of the sample to be measured based on the collected reflected light. The free switching between the modes supports real-time compensation of the objective lens aberration during use of the system, and continuous deterioration of the objective lens aberration during use of the system is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of defect detection, in particular to a defect detection system, an objective lens aberration compensation method and a defect detection method. BACKGROUND

[0002] In the semiconductor manufacturing process, defect detection is one of the key processes. Bright field defect detection can detect a wider range of defect types, and is a guarantee for improving product yield, reducing production cost and promoting process iteration. At present, in order to pursue higher resolution, larger field of view and higher throughput, the light power used by the bright field defect detection equipment is also greatly improved. The wave aberration caused by lens heat makes the image quality of the objective lens deteriorate, which has become one of the prominent problems.

[0003] At present, there are some schemes for compensating the aberration of the objective lens, which are generally realized by adjusting the position of the lens and modifying the shape of the lens during the equipment adjustment. Once the equipment is adjusted, it is very difficult to compensate the aberration of the objective lens. If the wave aberration of the objective lens can be compensated in real time and dynamically during the use of the equipment, the image quality of the objective lens in the defect detection equipment can be effectively prevented from deteriorating during use, and even the accuracy of the defect detection result can be improved. Unfortunately, there is currently a lack of defect detection equipment that can compensate the aberration of the objective lens in real time. SUMMARY

[0004] Based on the above problems, the present application provides a defect detection system, an objective lens aberration compensation method and a defect detection method, which aims to realize real-time compensation of the aberration of the objective lens during the use of the defect detection system, and to avoid continuous deterioration of the image quality of the objective lens during use, thereby affecting the accuracy of the defect detection result.

[0005] The embodiments of the present application disclose the following technical solutions:

[0006] The first aspect of the present application provides a defect detection system, which has two functional modes of aberration compensation mode and defect detection mode; the system comprises:

[0007] an interferometer, a light source module, a light modulation device, an objective lens, an optical reference piece and a defect detection module; when the system starts the aberration compensation mode, the interferometer is connected to the optical path of the system, the optical reference piece is located on the object plane of the objective lens, the light emitted by the interferometer passes through the light modulation device and the objective lens in turn to reach the optical reference piece, and is reflected on the optical reference piece, the reflected light passes through the objective lens and the light modulation device in turn to reach the interferometer and is collected by the interferometer; the reflected light collected by the interferometer is used to determine the adjustment strategy of the light modulation device, so as to compensate the wave aberration of the objective lens by adjusting the light modulation device;

[0008] After the light modulation device is adjusted according to the adjustment strategy, the system switches to the defect detection mode, the interferometer is cut out of the optical path of the system, the optical reference element is moved out of the object plane, and the sample to be tested is moved into the object plane; the light emitted by the light source module passes through the adjusted light modulation device and the objective lens in sequence to reach the sample to be tested, and is reflected on the sample to be tested, and the reflected light passes through the objective lens and the adjusted light modulation device in sequence and is collected by the defect detection module; the defect detection module is configured to generate a defect detection result of the sample to be tested according to the collected light.

[0009] In an optional implementation, the light modulation device is located between the light source module and the objective lens in the optical path, and the light modulation device is located between the defect detection module and the objective lens in the optical path; the defect detection system further comprises a light splitting device; the light splitting device is arranged between the light source module and the light modulation device in the optical path, and the light splitting device is located between the defect detection module and the light modulation device in the optical path; the light source module and the defect detection module are located on the first side and the second side of a light splitting surface of the light splitting device, respectively.

[0010] In an optional implementation, the defect detection system further comprises a first reflective element with variable position; the interferometer is located on the second side of the light splitting surface; the optical reference element is a second reflective element with variable position.

[0011] When the system starts the aberration compensation mode, the first reflective element is configured to move from a first position to a second position, and the second reflective element is configured to move from a third position to a fourth position; the light emitted by the interferometer passes through the light splitting device, is reflected by the light modulation device, and is transmitted by the objective lens in sequence to reach the second reflective element, is reflected on the second reflective element, and passes through the objective lens, is reflected by the light modulation device, and is transmitted by the light splitting device in sequence to reach the interferometer, and is collected by the interferometer; wherein the first position is located between the interferometer and the light splitting device in the optical path, when the first reflective element is located at the first position, the defect detection module and the light splitting device are located on one side of a reflective surface of the first reflective element; the second position and the third position are located outside the optical path of the system; and the fourth position is the position of the object plane.

[0012] In an optional implementation, when the system switches to the defect detection mode, the first reflecting element is configured to move from the second position to the first position, the second reflecting element is configured to move from the fourth position to the third position, and the sample to be detected is configured to move into the fourth position; the light emitted by the light source module is reflected by the light splitting device, reflected by the adjusted light modulation device, and transmitted by the objective lens in sequence to reach the sample to be detected, and is reflected on the sample to be detected, and the reflected light is transmitted by the objective lens, reflected by the adjusted light modulation device, transmitted by the light splitting device, and reflected by the first reflecting element in sequence to reach the defect detection module and is collected by the defect detection module.

[0013] In an optional implementation, the defect detection system further comprises an operation control module, which is electrically connected with the interferometer and is also electrically connected with the light modulation device.

[0014] The operation control module is configured to calculate wave aberration information of the objective lens according to the information of the light emitted by the interferometer and the information of the reflected light collected by the interferometer, generate an adjustment strategy for the light modulation device according to the wave aberration information, and send an electrical control instruction to the light modulation device based on an adjustment parameter in the adjustment strategy to adjust the light modulation device through the electrical control instruction.

[0015] In an optional implementation, the light modulation device is a deformable mirror.

[0016] The operation control module is specifically configured to calculate aberration to be compensated for by the deformable mirror according to the wave aberration information, determine a target adjustment surface profile of the deformable mirror according to the aberration to be compensated for by the deformable mirror, and generate an adjustment strategy containing adjustment parameters of adjustment elements on a back surface of the deformable mirror according to the target adjustment surface profile.

[0017] In an optional implementation, the adjustment elements are piezoelectric ceramics, and the adjustment parameters include displacement amounts to be moved by the piezoelectric ceramics.

[0018] The operation control module is specifically configured to send an electrical control instruction to the deformable mirror to drive each piezoelectric ceramic on the back surface of the deformable mirror to move according to a respective displacement amount to be moved, so that a surface profile of the deformable mirror reaches the target adjustment surface profile.

[0019] In an optional implementation, the adjustment elements are thermal resistors, and the adjustment parameters include current or voltage to be supplied.

[0020] The operation control module is specifically configured to send an electrical control instruction to the deformable mirror, control the electrical connection of a thermal resistance on the back surface of the deformable mirror based on the electrical connection current or the electrical connection voltage, and change the surface type of the deformable mirror until the target adjustment surface type is reached.

[0021] In an optional implementation, the light modulation device is a digital micromirror device (DMD) or a spatial light modulator (SLM).

[0022] The operation control module is specifically configured to determine a target phase distribution of the light modulation device according to the aberration that needs to be compensated by the deformable mirror, generate a grayscale image according to the target phase distribution, use the grayscale image as an adjustment parameter in the adjustment strategy, send an electrical control instruction to the light modulation device to load the grayscale image onto the screen of the light modulation device, and make the light modulation device reach the target phase distribution by loading the grayscale image.

[0023] The second aspect of the present application provides an objective lens aberration compensation method, applied to the defect detection system in any implementation of the first aspect; the objective lens aberration compensation method comprises:

[0024] Starting the aberration compensation mode of the system, controlling the interferometer to be connected into the optical path of the system, and controlling the optical reference member to be moved to the object plane of the objective lens.

[0025] Turning on the interferometer, and the light emitted by the interferometer sequentially passes through the light modulation device and the objective lens to reach the optical reference member and is reflected on the optical reference member.

[0026] Collecting, by the interferometer, the reflected light returned from the optical reference member and sequentially passing through the objective lens and the light modulation device to reach the interferometer;

[0027] Determining an adjustment strategy for the light modulation device according to the reflected light collected by the interferometer.

[0028] Adjusting the light modulation device by using the adjustment strategy to compensate for the wave aberration of the objective lens.

[0029] The third aspect of the present application provides a defect detection method, applied to the defect detection system in any implementation of the first aspect; the defect detection method comprises:

[0030] Starting the defect detection mode of the system.

[0031] When it is determined that the objective lens of the system needs to be compensated for aberration during the operation of the defect detection mode of the system, switching the system to the aberration compensation mode.

[0032] controlling the interferometer to be in the optical path of the system and controlling the optical reference to move to the object plane of the objective lens;

[0033] turning on the interferometer, light emitted by the interferometer passing through the light modulation device and the objective lens in sequence to the optical reference, and being reflected on the optical reference;

[0034] collecting, by the interferometer, reflected light returned from the optical reference and passing through the objective lens and the light modulation device in sequence to the interferometer;

[0035] determining, according to the reflected light collected by the interferometer, an adjustment strategy for the light modulation device;

[0036] adjusting the light modulation device by using the adjustment strategy to compensate for wave aberration of the objective lens;

[0037] switching the system to the defect detection mode;

[0038] controlling the interferometer to be cut out of the optical path of the system and controlling the optical reference to move out of the object plane, and moving a sample to be tested into the object plane;

[0039] turning on the light source module, light emitted by the light source module passing through the adjusted light modulation device and the objective lens in sequence to the sample to be tested, and being reflected on the sample to be tested;

[0040] collecting, by the defect detection module, reflected light returned from the sample to be tested and passing through the objective lens and the adjusted light modulation device in sequence to the defect detection module;

[0041] generating, by the defect detection module, a defect detection result of the sample to be tested according to the collected light.

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] The technical scheme of the present application provides a defect detection system, an objective lens aberration compensation method and a defect detection method. The objective lens aberration compensation method and the defect detection method are both applied in the above-mentioned defect detection system. The defect detection system has two functional modes, i.e., an aberration compensation mode and a defect detection mode, and can be freely switched between the two modes. For example, during operation in the defect detection mode, if a user finds that the objective lens image quality is deteriorated, the system can be switched to the aberration compensation mode. After the objective lens aberration compensation of the system is completed, the user switches the system to the defect detection mode, and completes the regular defect detection work.

[0044] The defect detection system realizes mode switching in a simple and convenient manner: if it is required to start the aberration compensation mode, only the interferometer needs to be connected into the optical path of the system, and the optical reference piece needs to be placed on the roof of the system, so that the light emitted by the interferometer successively passes through the optical modulation device and the objective lens to reach the optical reference piece, and returns from the optical reference piece in the original path until it is reflected back to the interferometer and is collected by the interferometer. The reflected light collected by the interferometer can be used to determine the adjustment strategy for the optical modulation device in the system, so as to achieve the purpose of compensating for the aberration of the objective lens. After the aberration compensation is completed, the system can return to the defect detection mode, at this time, only the interferometer needs to be cut out of the optical path of the system, and the optical reference piece needs to be removed from the optical path of the object surface, and the sample to be tested needs to be moved into the object surface of the system. At this time, the light is emitted by the light source module, and successively passes through the adjusted optical modulation device and the objective lens to reach the surface of the sample to be tested; the light reflected by the surface of the sample to be tested successively passes through the objective lens and the adjusted optical modulation device, and finally enters the defect detection module; the defect detection module can realize the detection of the defects of the sample to be tested based on the collected reflected light. The free switching between the modes supports the real-time compensation for the aberration of the objective lens in the use process of the defect detection system, so as to effectively avoid the continuous deterioration of the aberration of the objective lens in the use process and affect the accuracy of the defect detection result. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0046] Figure 1A A structural schematic diagram of a defect detection system provided by an embodiment of the present application;

[0047] Figure 1B A schematic diagram of a defect detection system provided by an embodiment of the present application working in a defect detection mode;

[0048] Figure 2 A schematic diagram of another defect detection system provided by an embodiment of the present application working in an aberration compensation mode;

[0049] Figure 3 A schematic diagram of another defect detection system provided by an embodiment of the present application working in a defect detection mode;

[0050] Figure 4A A structural schematic diagram of a deformable mirror provided by an embodiment of the present application, which is provided with a piezoelectric ceramic on the back surface;

[0051] Figure 4B A structural schematic diagram of another defect detection system provided by an embodiment of the present application;

[0052] Figure 5 A flow chart of an objective aberration compensation method provided for an embodiment of the present application;

[0053] Figure 6 A flow chart of a defect detection method provided for an embodiment of the present application. DETAILED DESCRIPTION

[0054] As described above, the current defect detection equipment generally compensates the objective aberration by adjusting the position of the lens or modifying the shape of the lens during the equipment installation process. However, it is very difficult to compensate the objective aberration after the equipment is installed. This is because the equipment cannot be repeatedly interrupted for use and re-installed for the compensation of the objective aberration in actual application, which will greatly affect the defect detection efficiency of the equipment and the normal operation of the work flow. At present, how to realize the real-time compensation of the objective aberration during the use of the equipment is a difficulty in the field.

[0055] For the above problems, the inventors propose a defect detection system, an objective aberration compensation method and a defect detection method. In the present application, an interferometer, a light source module, a light modulation device, an objective lens, an optical reference and a defect detection module are configured in the defect detection system. The interferometer and the optical reference can be transformed in position according to the current function mode of the system, so as to flexibly realize the switching of the system mode. When the aberration compensation mode of the system is started, the interferometer is mainly responsible for the light emission and light collection, and the reflected light collected by the interferometer can be used to determine the adjustment strategy of the light modulation device, so as to realize the compensation of the objective aberration by adjusting the light modulation device. When the defect detection mode of the system is started, the interferometer is removed from the light path, the object plane of the system is placed in the sample to be tested, and the light reflected by the sample to be tested passes through the objective lens and the adjusted light modulation device in turn and is finally collected by the defect detection module. Based on the collected light, the defect detection module can generate the defect detection result of the sample to be tested. It can be seen that in the present application, since the interferometer and the optical reference can be flexibly transformed in position according to the function mode of the system, the defect detection system can support the temporary execution of the compensation of the objective aberration during the use of the system. In this way, the continuous deterioration of the objective aberration during the use of the system is effectively avoided, and the accuracy of the defect detection result can be effectively improved.

[0056] In order to make the person skilled in the art better understand the scheme of the present application, the technical scheme 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, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor are within the scope of protection of the present application.

[0057] Referring to Figure 1A , the figure is a structural schematic diagram of a defect detection system provided by an embodiment of the present application. As Figure 1A indicated, the defect detection system provided by the embodiment of the present application comprises an interferometer 01, a light source module 02, a light modulation device 03, an objective lens 04, an optical reference element 05 and a defect detection module 06. In an alternative implementation, the light modulation device 03 in the defect detection system is located between the light path of the light source module 02 and the objective lens 04, and the light modulation device 03 is located between the light path of the defect detection module 06 and the objective lens 04.

[0058] The defect detection system provided by the embodiment of the present application has two functional modes, i.e. an aberration compensation mode and a defect detection mode. The switching between the two modes is realized by adjusting the position of the interferometer 01, changing the light source and adjusting the elements of the system object plane.

[0059] In the present application, as Figure 1A indicated, the red line represents the light path when the system works in the aberration compensation mode. When the system starts the aberration compensation mode, the interferometer 01 is connected into the light path of the system, and the optical reference element 05 is located on the object plane of the objective lens 04. In this mode, the interferometer 01 acts as the light source of the system. The light emitted by the interferometer 01 passes through the light modulation device 03 and the objective lens 04 in turn to reach the optical reference element 05, and is reflected on the optical reference element 05. The reflected light passes through the objective lens 04 and the light modulation device 03 in turn to reach the interferometer 01 and is collected by the interferometer 01.

[0060] In the embodiment of the present application, the optical reference element 05 can be an element with the function of reflecting light, for example, a mirror in various forms. As an example, the optical reference element 05 can be a plane mirror. The objective lens 04 can be a single lens, or can be an objective lens 04 lens group composed of multiple lenses. In the working process of the defect detection system, if the light source power is large, it is easy to cause the objective lens 04 lens to accumulate heat, and then cause wave aberration, promote the degradation of the image quality of the objective lens 04, and even affect the accuracy of the defect detection of the measured object. Therefore, the embodiment of the present application proposes to compensate the aberration of the objective lens 04 in real time during the working process of the objective lens 04 through the aberration compensation function of the defect detection system.

[0061] In aberration compensation mode, the reflected light collected by interferometer 01 is used to determine the adjustment strategy for optical modulator 03, thereby compensating for the wavefront aberration of objective lens 04. In this scheme, optical modulator 03 can be implemented in various ways, such as a deformable mirror, a digital micromirror device (DMD), or a spatial light modulator (SLM). Since the adjustment strategy for optical modulator 03 is determined based on the reflected light collected by interferometer 01, and the reflected light collected by interferometer 01 reflects the wavefront aberration of objective lens 04, adjusting optical modulator 03 according to the adjustment strategy achieves compensation for the wavefront aberration of objective lens 04 in the system. Afterward, the system can switch to defect detection mode.

[0062] Figure 1B This is a schematic diagram illustrating a defect detection system operating in defect detection mode, as provided in an embodiment of this application. Figure 1B In the diagram, the green line represents the optical path of the system operating in defect detection mode. From... Figure 1B It is easy to see that when the system is operating in defect detection mode, the interferometer 01 is required to be cut out of the system's optical path, and the optical reference 05 is required to be moved out of the object surface. At this time, the sample to be tested 09 needs to be moved into the object surface, i.e., occupy... Figure 1A The position of the optical reference component 05. In defect detection mode, the light source module 02 replaces the interferometer 01 as the system light source. The light emitted by the light source module 02 passes sequentially through the adjusted light modulator 03 and the objective lens 04 to reach the sample 09 under test, and is reflected on the sample 09. The reflected light passes sequentially through the objective lens 04 and the adjusted light modulator 03 and is collected by the defect detection module 06; the defect detection module 06 is used to generate the defect detection result of the sample 09 under test based on the collected light.

[0063] Since the defect detection results are generated based on the reflected light of the collected sample 09, this is a relatively mature technology for defect detection in the semiconductor manufacturing field, so it will not be elaborated here.

[0064] From the above introduction, it is not difficult to find that the defect detection system provided in the embodiments of the present application has a simple and convenient mode switching method: if it is necessary to start the aberration compensation mode, only need to connect the interferometer 01 to the optical path of the system, and place the optical reference piece 05 on the roof of the system, so that the light emitted by the interferometer 01 successively passes through the light modulation device 03 and the objective lens 04 to reach the optical reference piece 05, and returns from the optical reference piece 05 to the interferometer 01 by the original route and is reflected back to the interferometer 01. The reflected light collected by the interferometer 01 can be used to determine the adjustment strategy for the light modulation device 03 in the system, so as to achieve the purpose of aberration compensation for the objective lens 04. After the aberration compensation is completed, the system can return to the defect detection mode, at this time, only need to cut out the interferometer 01 from the optical path of the system, and move the optical reference piece 05 from the object surface out of the optical path, and then move the sample 09 to be tested into the object surface of the system. At this time, the light source module 02 emits light, which successively passes through the adjusted light modulation device 03 and the objective lens 04 to reach the surface of the sample 09 to be tested; the light reflected by the surface of the sample 09 to be tested successively passes through the objective lens 04 and the adjusted light modulation device 03, and finally enters the defect detection module 06; the defect detection module 06 can realize the detection of the defects of the sample 09 to be tested based on the collected reflected light. The free switching between the modes supports the real-time compensation for the aberration of the objective lens 04 in the use process of the defect detection system, so as to effectively avoid the continuous deterioration of the image quality of the objective lens 04 in the use process and affect the accuracy of the defect detection result.

[0065] The basic structure of the defect detection system introduced above should have the interferometer 01, the light source module 02, the light modulation device 03, the objective lens 04, the optical reference piece 05 and the defect detection module 06. In other possible implementation manners, more elements can be arranged in the defect detection system to realize the functions such as light path folding. That is, the system light path is not limited to the structure shown in Figure 1A 、 Figure 1B . The other possible structures of the defect detection system will be introduced below in combination with Figure 2 and Figure 3 .

[0066] Figure 2 The schematic diagram of another defect detection system provided in the embodiments of the present application working in the aberration compensation mode is shown in Figure 2 . As shown in the system, it further comprises a light splitting device 07 and a first reflecting element 08. The position of the first reflecting element 08 is adjustable. By comparing Figure 2 and Figure 3 , it can be seen that the relative positions of the first reflecting element 08 and other elements are different in Figure 2 and Figure 3 . In Figure 2 , the first reflecting element 08 is at the second position P2, that is, outside the system light path. While in Figure 3The system is shown to work in the case of defect detection mode, the first reflecting element 08 is moved to the first position P1, that is, in the system light path. Due to the change of the position of the first reflecting element 08, and the change of the light source in the two different modes of the system, the light path shown in the figure also changes obviously. Figure 2 and Figure 3 The light path shown in the figure also changes obviously.

[0067] As shown in Figure 2 and Figure 3 The light splitting device 07 is arranged between the light source module 02 and the light modulation device 03, and the light splitting device 07 is located between the defect detection module 06 and the light modulation device 03. The light source module 02 and the defect detection module 06 are respectively located on the two sides of the light splitting surface of the light splitting device 07, which can be called the first side and the second side. The light splitting device 07 has the functions of transmitting light and reflecting light. The light source module 02 and the defect detection module 06 located on the first side and the second side of the light splitting device 07 respectively use the reflection function of the first side and the light transmission function of the second side of the light splitting device 07 in the light path.

[0068] As shown in Figure 3 The interferometer 01 is also located on the second side of the light splitting surface, and the cutting in and cutting out of the interferometer 01 in the system light path can be realized by the first reflecting element 08. As shown in Figure 2 and Figure 3 When the first reflecting element 08 is in the second position P2, the interferometer 01 is included in the system light path and can be used as a light source and can collect reflected light. When the first reflecting element 08 is in the first position P1, the interferometer 01 is cut out of the system light path even if the position does not change. The first reflecting element 08 can be various forms of optical elements with reflecting function, as an example, the first reflecting element 08 can be a plane mirror, and its position can be flexibly changed between the first position P1 and the second position P2. The optical reference element 05 introduced in the foregoing can be a second reflecting element with variable position, as an example, the second reflecting element is also a plane mirror.

[0069] In combination with Figure 2 and Figure 3 When the system starts the aberration compensation mode, the first reflecting element 08 is configured to move from the first position P1 to the second position P2, and the second reflecting element is configured to move from the third position P3 to the fourth position P4; the light emitted by the interferometer 01 passes through the light splitting device 07, the light modulation device 03 and the objective lens 04 in turn, is reflected on the second reflecting element, and then passes through the objective lens 04, the light modulation device 03 and the light splitting device 07 in turn to reach the interferometer 01, and is collected by the interferometer 01.

[0070] AsFigure 3 As shown, the first position P1 is located between the optical paths of the interferometer 01 and the beam splitter 07. When the first reflecting element 08 is located at the first position P1, both the defect detection module 06 and the beam splitter 07 are located on one side of the reflecting surface of the first reflecting element 08. The second position P2 and the third position P3 are located outside the optical path of the system. The fourth position P4 is the position of the object surface.

[0071] like Figure 3 As shown, when the system switches to defect detection mode, the first reflective element 08 is configured to move from the second position P2 to the first position P1, the second reflective element is configured to move from the fourth position P4 to the third position P3, and the sample to be tested 09 is configured to move into the fourth position. The light emitted by the light source module 02 is reflected by the beam splitter 07, reflected by the adjusted light modulator 03, and transmitted by the objective lens 04 before reaching the sample to be tested 09. The reflected light is then reflected by the objective lens 04, reflected by the adjusted light modulator 03, transmitted by the beam splitter 07, and reflected by the first reflective element 08 before reaching the defect detection module 06 and being collected by the defect detection module 06.

[0072] As mentioned earlier, the optical modulation device 03 can be a deformable mirror. The surface shape of the deformable mirror can be adjusted; therefore, it has the ability to compensate for the aberrations of the objective lens 04 in the system. In practical applications, an adjustment element is provided on the back of the deformable mirror. This adjustment element can drive the surface shape of the deformable mirror to change. In practical applications, the adjustment element can be implemented in various ways. For example, the adjustment element can be a piezoelectric ceramic, such as... Figure 4A As shown. In other possible implementations, the adjustment element can also be a thermistor. The adjustment method of the optical modulation device 03 will then be described in more detail with reference to the embodiments.

[0073] Figure 4B This is a schematic diagram of another defect detection system provided in an embodiment of this application. (Combined with...) Figure 4B As shown, the system may further include a computational control module 10. The computational control module 10 is electrically connected to the interferometer 01 and also electrically connected to the optical modulator 03. The computational control module 10 is used to calculate the wavefront aberration information of the objective lens 04 based on the information of the light emitted by the interferometer 01 and the information of the reflected light collected by the interferometer 01; generate an adjustment strategy for the optical modulator 03 based on the wavefront aberration information; and send electrical control commands to the optical modulator 03 based on the adjustment parameters in the adjustment strategy, so as to adjust the optical modulator 03 through the electrical control commands.

[0074] In an optional implementation, the light modulation device 03 is a deformable mirror; the operation control module 10 is specifically configured to calculate wavefront aberration information required to be compensated by the deformable mirror; determine a target adjustment surface shape of the deformable mirror according to the wavefront aberration information required to be compensated by the deformable mirror; and generate an adjustment strategy containing adjustment parameters of adjustment elements on the back surface of the deformable mirror according to the target adjustment surface shape.

[0075] In an example introduced above, the adjustment elements on the back surface of the deformable mirror are piezoelectric ceramics, and the adjustment parameters include displacement amounts required to be moved by the piezoelectric ceramics.

[0076] The operation control module 10 is specifically configured to send an electrical control instruction to the deformable mirror to drive each piezoelectric ceramic on the back surface of the deformable mirror to move according to a respective displacement amount required to be moved, so that the surface shape of the deformable mirror reaches the target adjustment surface shape.

[0077] With reference to Figure 4A The back surface of the deformable mirror is provided with a plurality of piezoelectric ceramics. In order to facilitate adjustment of the surface shape of the deformable mirror, the piezoelectric ceramics can be uniformly spaced, or can be arranged in combination with the specific shape of the deformable mirror. Since the displacement amount of each piezoelectric ceramic can be independently controlled electrically, it can be known that the adjustment of the surface shape of the deformable mirror is very flexible, and can greatly meet the adjustment requirements of the surface shape of the deformable mirror, thereby effectively compensating for the wavefront aberration of the objective lens 04.

[0078] In actual application, a corresponding relationship between the surface shape of the deformable mirror and a plurality of wavefront aberration information can be constructed in advance. The surface shape refers to a surface shape capable of compensating for the corresponding wavefront aberration. Based on the corresponding relationship, when the operation control module 10 calculates the wavefront aberration of the objective lens 04, the target adjustment surface shape of the deformable mirror can be correspondingly determined. The operation control module 10 can also master the positions of the piezoelectric ceramics, and based on the current positions and the target adjustment surface shape, calculate the displacement amount of each piezoelectric ceramic from the corresponding target position under the target adjustment surface shape. Then, the adjustment strategy is generated to cause the piezoelectric ceramics to move the corresponding displacement amount for adjustment.

[0079] In another example introduced above, the adjustment elements on the back surface of the deformable mirror are thermal resistors, and the adjustment parameters include current or voltage.

[0080] The operation control module 10 is specifically configured to send an electrical control instruction to the deformable mirror to control the thermal resistors on the back surface of the deformable mirror to be powered based on the current or voltage, so that the surface shape of the deformable mirror changes due to the heat generated after the thermal resistors are powered until the target adjustment surface shape is reached.

[0081] The thermal resistance of the deformable mirror can be, for example, a material with a high temperature coefficient of resistance, such as nickel, platinum, etc., which can effectively convert electrical energy into heat energy. When an electric current passes through the thermal resistance, the electrical energy is converted into heat energy due to the resistance of the resistance, causing the thermal resistance to increase in temperature. This temperature change will cause the thermal expansion and contraction of the thermal resistance material, thereby changing the local surface shape of the deformable mirror.

[0082] In practical applications, a corresponding relationship between heat and surface shape adjustment amount can be constructed in advance. The operation control module 10 can determine the surface shape adjustment amount according to the difference between the target adjustment surface shape and the current surface shape; determine the heat that should be generated by the thermal resistance based on the above-mentioned corresponding relationship, and then determine the current or voltage to be applied to the thermal resistance of the deformable mirror in a powered manner to generate heat and change the surface shape of the deformable mirror.

[0083] In optional implementations, the light modulation device 03 can be a digital micromirror device (DMD) or a spatial light modulator (SLM) in addition to the deformable mirror mentioned above.

[0084] DMD is a new type of optical element based on micro-optics and micro-electromechanical system technology, which realizes fine control of light field by dynamically controlling the geometric parameters (such as focal length, position or refractive index) of micro-lenses. Each micro-lens unit can work independently, thus showing strong application potential in beam shaping, dynamic focusing, 3D imaging, etc. These micro-lens units are usually arranged in a two-dimensional array. The geometric parameters (such as curvature, thickness) of each lens can be dynamically adjusted by electrical signals, thermal effects or mechanical forces. By changing the focal length of individual lenses (for example, using liquid crystal refractive index change or MEMS deformation), the digital micromirror array can adjust the light path in real time. The cooperative work of multiple lenses can realize the phase modulation of complex wavefront, such as correcting optical aberration or generating specific light field distribution.

[0085] SLM is an optical device that can modulate the spatial distribution (such as amplitude, phase, polarization, etc.) of light waves. SLM realizes the control of light field by changing some characteristics (such as amplitude, phase, polarization) of light waves. This modulation can be real-time and dynamic, and can be controlled by electrical signals, optical signals or other external control signals.

[0086] For the implementation mode in which the light modulation device 03 is a digital micromirror array DMD or a spatial light modulator SLM, in the defect detection system proposed by the present application, the operation control module 10 is specifically configured to determine a target phase distribution of the light modulation device 03 according to the aberration that needs to be compensated by the deformable mirror; generate a grayscale image according to the target phase distribution, and use the grayscale image as an adjustment parameter in the adjustment strategy; and send an electrical control instruction to the light modulation device 03 to load the grayscale image onto the screen of the light modulation device 03, so that the light modulation device 03 reaches the target phase distribution by loading the grayscale image.

[0087] Taking phase-modulated SLM as an example, the core of SLM's phase adjustment through superimposed grayscale images lies in establishing a precise grayscale-phase mapping relationship. SLM can be understood as a liquid crystal screen. The grayscale image is loaded onto the SLM screen, and each grayscale corresponds to the orientation of a liquid crystal particle, further changing the optical path difference to achieve the purpose of phase modulation. Therefore, what is actually loaded onto the SLM is a phase matrix, which is used to compensate for the wavefront aberration of the system.

[0088] Based on the defect detection system described above, this application also provides a method for compensating for object image aberration. This method is applied to the defect detection system described above. The method is described below with reference to the accompanying drawings. The method mainly describes the process of compensating for object image aberration using this defect detection system.

[0089] Figure 5 This is a flowchart illustrating an object image aberration compensation method provided in an embodiment of this application. Figure 5 As shown, the object image aberration compensation methods include:

[0090] S501. Activate the aberration compensation mode of the system, control the interferometer to enter the optical path of the system, and control the optical reference to move to the object plane of the objective lens.

[0091] S502. Turn on the interferometer. The light emitted by the interferometer passes through the optical modulation device and the objective lens in sequence to reach the optical reference and is reflected on the optical reference.

[0092] S503, The reflected light collected by the interferometer from the optical reference and passing through the objective lens and optical modulation device in sequence before reaching the interferometer;

[0093] S504. Based on the reflected light collected by the interferometer, determine the adjustment strategy for the optical modulation device;

[0094] S505. Adjust the optical modulation device using an adjustment strategy to compensate for the wavefront aberration of the objective lens.

[0095] exist Figure 5 The illustrated process mainly describes the adjustment method for the positions of some components after the system activates the aberration compensation mode, as well as the optical paths of the light emitted by the interferometer and the light reflected back from the optical reference. Steps S504 and S505 can be implemented by modules, components, or devices with computational and control functions. For example, S504 and S505 can be implemented by the computational control module described above.

[0096] Based on the defect detection system and object aberration compensation method described above, this application also provides a defect detection method. This method is also applied to the defect detection system described above. Figure 6A flowchart of a defect detection method. As shown in Figure 6 the defect detection method comprises:

[0097] S601, starting a defect detection mode of the system;

[0098] S602, when it is determined that the objective lens of the system needs to be compensated for aberration during the system running the defect detection mode, switching the system to an aberration compensation mode;

[0099] S603, controlling the interferometer to be connected into the optical path of the system, and controlling the optical reference member to be moved to the object plane of the objective lens;

[0100] S604, starting the interferometer, and the light emitted by the interferometer passes through the light modulation device and the objective lens in sequence to reach the optical reference member, and is reflected on the optical reference member;

[0101] S605, collecting, by the interferometer, the reflected light returned from the optical reference member and passing through the objective lens and the light modulation device in sequence to reach the interferometer;

[0102] S606, determining an adjustment strategy for the light modulation device according to the reflected light collected by the interferometer;

[0103] S607, adjusting the light modulation device by using the adjustment strategy to compensate for the wave aberration of the objective lens;

[0104] S608, switching the system to the defect detection mode;

[0105] S609, controlling the interferometer to be cut out of the optical path of the system, and controlling the optical reference member to be moved out of the object plane, and moving the sample to be tested into the object plane;

[0106] S610, starting the light source module, and the light emitted by the light source module passes through the adjusted light modulation device and the objective lens in sequence to reach the sample to be tested, and is reflected on the sample to be tested;

[0107] S611, collecting, by the defect detection module, the reflected light returned from the sample to be tested and passing through the objective lens and the adjusted light modulation device in sequence to reach the defect detection module;

[0108] S612, generating, by the defect detection module, a defect detection result of the sample to be tested according to the collected light.

[0109] In combination with S601-S612, the flow as a whole reflects a process in which the system performs defect detection, then performs intermediate objective lens aberration compensation, and then continues to perform defect detection after the compensation is completed. During this period, the system light source needs to be changed, and the elements on the object plane also need to be adjusted. As can be seen from the above flow, the present application can compensate for the objective lens aberration in real time during the detection of the defect detection system. It does not need to interrupt the detection and re-adjust, which improves the real-time performance of the aberration compensation, and is conducive to more efficient and more accurate defect detection.

[0110] It should be noted that each of the embodiments in the present specification is described in a progressive manner, and the same and similar parts between the embodiments can be referred to each other. Each embodiment focuses on the difference from other embodiments. In particular, for the method embodiment, since it is basically similar to the system embodiment, the description is relatively simple, and the relevant parts can be referred to the part of the system embodiment. The system embodiment described above is only schematic, and the units described as separate components can or can not be physically separate, and the components prompted as units can or can not be physical units, that is, they can be located in one place, or distributed on multiple network units. According to the actual needs, some or all of the modules can be selected to achieve the purpose of the present embodiment. Those skilled in the art can understand and implement it without creative labor.

[0111] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any skilled person in the art can easily think of changes or replacements within the technical range disclosed in 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 defect detection system, characterized by, The system has two functional modes of aberration compensation mode and defect detection mode; the system comprises: an interferometer, a light source module, a light modulation device, an objective lens, an optical reference element and a defect detection module; when the system starts the aberration compensation mode, the interferometer is connected into the light path of the system, the optical reference element is located on the object plane of the objective lens, the light emitted by the interferometer passes through the light modulation device and the objective lens in sequence to reach the optical reference element, and is reflected on the optical reference element, the reflected light passes through the objective lens and the light modulation device in sequence to reach the interferometer and is collected by the interferometer; the reflected light collected by the interferometer is used to determine the adjustment strategy of the light modulation device to compensate the wave aberration of the objective lens by adjusting the light modulation device; after the light modulation device is adjusted according to the adjustment strategy, the system switches to the defect detection mode, the interferometer is cut out of the light path of the system, the optical reference element is removed from the object plane, and a sample to be tested is moved into the object plane; the light emitted by the light source module passes through the adjusted light modulation device and the objective lens in sequence to reach the sample to be tested, and is reflected on the sample to be tested, the reflected light passes through the objective lens and the adjusted light modulation device in sequence and is collected by the defect detection module; the defect detection module is used to generate the defect detection result of the sample to be tested according to the collected light; the light modulation device is located between the light source module and the objective lens, and the light modulation device is located between the defect detection module and the objective lens; the system further comprises a light splitting device; the light splitting device is arranged between the light source module and the light modulation device, and the light splitting device is located between the defect detection module and the light modulation device; the light source module and the defect detection module are respectively located on the first side and the second side of the light splitting surface of the light splitting device; the system further comprises a first reflective element with variable position; the interferometer is located on the second side of the light splitting surface; the optical reference element is a second reflective element with variable position; when the system starts the aberration compensation mode, the first reflective element is configured to move from a first position to a second position, and the second reflective element is configured to move from a third position to a fourth position; the light emitted by the interferometer passes through the light splitting device, is reflected by the light modulation device and is transmitted by the objective lens in sequence to reach the second reflective element, is reflected on the second reflective element, passes through the objective lens, is reflected by the light modulation device and is transmitted by the light splitting device in sequence to reach the interferometer and is collected by the interferometer; wherein the first position is located between the interferometer and the light splitting device, when the first reflective element is located at the first position, the defect detection module and the light splitting device are located on one side of the reflection surface of the first reflective element; the second position and the third position are located outside the light path of the system; the fourth position is the position of the object plane.

2. The system of claim 1, wherein, when the system switches to the defect detection mode, the first reflecting element is configured to move from the second position to the first position, the second reflecting element is configured to move from the fourth position to the third position, and the sample under test is configured to move into the fourth position; light emitted by the light source module is transmitted through the light splitting device, the adjusted light modulation device, and the objective lens in sequence, reaches the sample under test, and is reflected on the sample under test, and the reflected light is transmitted through the objective lens, the adjusted light modulation device, the light splitting device, and the first reflecting element in sequence, reaches the defect detection module, and is collected by the defect detection module.

3. The system of claim 1, wherein, The system further comprises an operation control module, which is electrically connected to the interferometer and further electrically connected to the light modulation device. The operation control module is configured to calculate wave aberration information of the objective lens based on information of light emitted by the interferometer and information of reflected light collected by the interferometer, generate an adjustment strategy for the light modulation device based on the wave aberration information, and send an electrical control instruction to the light modulation device based on an adjustment parameter in the adjustment strategy to adjust the light modulation device through the electrical control instruction.

4. The system of claim 3, wherein, The light modulation device is a deformable mirror. The operation control module is specifically configured to calculate aberration to be compensated for by the deformable mirror based on the wave aberration information, determine a target adjustment surface profile of the deformable mirror based on the aberration to be compensated for by the deformable mirror, and generate an adjustment strategy including adjustment parameters of adjustment elements on a back surface of the deformable mirror based on the target adjustment surface profile.

5. The system of claim 4, wherein, The adjustment elements are piezoelectric ceramics, and the adjustment parameters include displacement amounts that the piezoelectric ceramics need to move. The operation control module is specifically configured to send an electrical control instruction to the deformable mirror to drive each piezoelectric ceramic on the back surface of the deformable mirror to move according to a respective displacement amount that the piezoelectric ceramic needs to move, so that a surface profile of the deformable mirror reaches the target adjustment surface profile.

6. The system of claim 4, wherein, The adjustment elements are heating resistors, and the adjustment parameters include current or voltage. The operation control module is specifically configured to send an electrical control instruction to the deformable mirror to control the heating resistors on the back surface of the deformable mirror to be powered based on the current or the voltage, so that a surface profile of the deformable mirror changes due to heat generated after the heating resistors are powered until the target adjustment surface profile is reached.

7. The system of claim 4, wherein, The light modulation device is a digital micromirror device (DMD) or a spatial light modulator (SLM). The operation control module is specifically configured to determine a target phase distribution of the light modulation device based on the aberration to be compensated for by the deformable mirror, generate a grayscale image based on the target phase distribution, use the grayscale image as an adjustment parameter in the adjustment strategy, send an electrical control instruction to the light modulation device to load the grayscale image onto a screen of the light modulation device, and make the light modulation device reach the target phase distribution by loading the grayscale image.

8. An objective aberration compensation method, characterized by, The method is applied to the defect detection system of any one of claims 1-7; the method comprises: starting an aberration compensation mode of the system, controlling the interferometer to access the optical path of the system, and controlling the optical reference member to move to the object plane of the objective lens; starting the interferometer, and the light emitted by the interferometer sequentially passes through the light modulation device and the objective lens to reach the optical reference member and is reflected on the optical reference member; collecting, by the interferometer, the reflected light returned from the optical reference member and sequentially passing through the objective lens and the light modulation device to reach the interferometer; determining an adjustment strategy for the light modulation device according to the reflected light collected by the interferometer; adjusting the light modulation device by using the adjustment strategy to compensate for the wave aberration of the objective lens.

9. A defect detection method characterized by, The method is applied to the defect detection system of any one of claims 1-7; the method comprises: starting a defect detection mode of the system; when it is determined that the objective lens of the system needs to be compensated for aberration during the system running the defect detection mode, switching the system to an aberration compensation mode; controlling the interferometer to access the optical path of the system, and controlling the optical reference member to move to the object plane of the objective lens; starting the interferometer, and the light emitted by the interferometer sequentially passes through the light modulation device and the objective lens to reach the optical reference member and is reflected on the optical reference member; collecting, by the interferometer, the reflected light returned from the optical reference member and sequentially passing through the objective lens and the light modulation device to reach the interferometer; determining an adjustment strategy for the light modulation device according to the reflected light collected by the interferometer; adjusting the light modulation device by using the adjustment strategy to compensate for the wave aberration of the objective lens; switching the system to the defect detection mode; controlling the interferometer to be cut out of the optical path of the system, and controlling the optical reference member to be moved out of the object plane, and moving a to-be-tested sample into the object plane; starting the light source module, and the light emitted by the light source module sequentially passes through the adjusted light modulation device and the objective lens to reach the to-be-tested sample and is reflected on the to-be-tested sample; collecting, by the defect detection module, the reflected light returned from the to-be-tested sample and sequentially passing through the objective lens and the adjusted light modulation device to reach the defect detection module; generating, by the defect detection module, a defect detection result of the to-be-tested sample according to the collected light.

Images