Optical detection device and method

Abstract

The application discloses an optical detection device and method. The optical detection device comprises a carrier for carrying a to-be-detected object, an illumination module for emitting a detection light beam to the to-be-detected object, a focusing module for respectively emitting the detection light beam to the to-be-detected object and a reference focal plane through an optical assembly and converging to a spectrum recorder through the optical assembly, a data processing module for acquiring phase information and a spectrum wavelength of the interference light beam and calculating an optimal relative distance between the carrier and an imaging objective lens when a to-be-detected surface of the to-be-detected object is placed on an optimal focal plane according to the phase information and the spectrum wavelength of the interference light beam, and a control module for controlling a driving part to drive the carrier to move in a direction perpendicular to a plane where the carrier is located, so that the relative distance between the carrier and the imaging objective lens reaches the optimal relative distance. The device is used to improve detection efficiency on the basis of ensuring optical detection accuracy.

Description

Technical Field

[0001] This invention relates to the field of optical inspection technology, and in particular to an optical inspection device and method. Background Technology

[0002] In recent years, with the deepening and popularization of industrial automation and intelligence, the use of automated optical inspection (AOI) equipment to replace traditional manual visual inspection has become a technological development trend. AOI equipment is widely used in the automotive, pharmaceutical, transportation, and semiconductor industries due to its fast and accurate defect identification and location capabilities.

[0003] Currently, existing AOI equipment typically includes an optical imaging module, a stage, and a material transfer system. The optical imaging module includes an illumination unit, an imaging lens, and a detector. During AOI inspection, the surface to be inspected needs to be adjusted to the optimal focal plane to obtain a clear image for easy identification of defects. Generally, existing technologies use an optical system to scan and image the object in a direction perpendicular to the stage; however, this scanning process takes time, impacting the inspection efficiency on the production line.

[0004] Given the above background, how to improve and optimize detection efficiency while ensuring the accuracy of optical detection has become a current technical challenge. Summary of the Invention

[0005] This invention provides an optical detection device and method to improve detection efficiency while ensuring the accuracy of optical detection.

[0006] In a first aspect, the present invention provides an optical detection device, comprising a stage for carrying an object under test, an illumination module for emitting a detection beam toward the object under test, and a focusing module for using optical components to split the detection beam and direct it onto the object under test and a reference focal plane respectively, and to converge it to a spectral recorder; the spectral recorder is used to record the phase information and spectral wavelength of the interference beam after the detection beam is reflected by the object under test and the reference focal plane respectively. The optical detection device further includes a data processing module for acquiring the phase information and spectral wavelength of the interference beam, and calculating, based on the phase information and spectral wavelength of the interference beam, the optimal relative distance between the stage and the imaging objective when the surface under test of the object under test is placed at the optimal focal plane. A control module is used to control a drive unit to drive the stage to move in a direction perpendicular to the plane of the stage, so that the relative distance between the stage and the imaging objective reaches the optimal relative distance.

[0007] The beneficial effects of the optical detection device provided by the present invention are as follows: In this embodiment, the data processing module utilizes the principle of white light interferometry to calculate the optimal relative distance between the stage and the imaging objective when the test surface of the object to be tested is placed at the optimal focal plane using the phase information and spectral wavelength of the interference beam. Based on this optimal relative distance, the stage can be adjusted once to complete the focusing process. This avoids multiple scanning and image taking of the object to be tested, saves focusing time, and improves detection efficiency while ensuring the accuracy of optical detection.

[0008] Optionally, the optical inspection device further includes an imaging module, used to acquire the imaging beam reflected by the object under test when the surface to be tested is placed at the optimal focal plane, and to image the object under test to form image information. The data processing module is further used to acquire the image information from the imaging module and perform optical inspection on the image information.

[0009] Optionally, the data processing module is further configured to acquire the light intensity of the interference beam and determine the light intensity adjustment amount of the detection optical path module based on the light intensity of the interference beam; the detection optical path module is connected to the data processing module, and the detection optical path module is further configured to adjust the light intensity of the detection beam based on the light intensity adjustment amount.

[0010] Optionally, the illumination module includes a focusing light source, a first mechanical switch, a first beam splitter, and an imaging light source; the focusing light source is used to emit a first detection beam, the imaging light source is used to emit a second detection beam, and the first mechanical switch is used to control the opening or closing of the focusing optical path corresponding to the first detection beam.

[0011] The focusing module includes a test surface optical path, a reference surface optical path, and a focal plane measurement optical path; the test surface optical path includes a first imaging objective lens and a second beam splitter adjacent to the test object; the reference surface optical path includes a second mechanical switch, a second imaging objective lens, and a reference focal plane; the focal plane measurement optical path includes a third beam splitter, a lens, and a spectrometer.

[0012] When the first mechanical switch is opened, both the first detection beam and the second detection beam pass through the first beam splitter, the second beam splitter, and the first imaging objective lens and are incident on the object under test, forming a first reflected beam after reflection from the surface of the object under test; and when the second mechanical switch is opened, both the first detection beam and the second detection beam pass through the first beam splitter, the second beam splitter, and the second imaging objective lens and are incident on the reference focal plane, forming a second reflected beam after reflection from the surface of the reference focal plane, the first reflected beam and the second reflected beam forming the interference beam, and the interference beam enters the spectral recorder through the lens.

[0013] Optionally, the illumination module includes a focusing light source, a first polarizer, a first beam splitter, an imaging light source, and a second polarizer. The focusing module includes a test surface optical path, a reference surface optical path, and a focal plane measurement optical path; the test surface optical path includes a first imaging objective lens adjacent to the test object and a second beam splitter; the reference surface optical path includes a second mechanical switch, a second imaging objective lens, and a reference focal plane; the focal plane measurement optical path includes a third beam splitter, an analyzer, a lens, and a spectral recorder; the polarization direction of the analyzer is the same as the polarization direction of the first polarizer, but orthogonal to the polarization direction of the second polarizer.

[0014] Both the first detection beam and the second detection beam are incident on the object under test through the first beam splitter, the second beam splitter, and the first imaging objective, and are reflected by the surface of the object under test to form a first reflected beam; and the first detection beam is incident on the reference focal plane through the first beam splitter, the second beam splitter, the analyzer, and the second imaging objective, and is reflected by the surface of the reference focal plane to form a second reflected beam. The first reflected beam and the second reflected beam form the interference beam, and the interference beam is incident on the spectral recording module through a lens.

[0015] Optionally, the focusing light source is a broadband light source.

[0016] Optionally, the broadband light source is a white light source.

[0017] In a second aspect, the present invention also provides an optical detection method, which can be applied to the optical detection device as described in any embodiment of the first aspect, the method comprising:

[0018] The control illumination module emits a detection beam toward the object under test, which is placed on a stage.

[0019] The focusing control module uses optical components to split the detection beam and direct it into the object under test and the reference focal plane respectively, and then focuses it to the spectral recorder through optical components; the spectral recorder is used to record the phase information and spectral wavelength of the interference beam formed by the detection beam after being reflected by the object under test and the reference focal plane respectively;

[0020] The phase information and spectral wavelength of the interference beam are acquired, and the optimal relative distance between the stage and the imaging objective is calculated based on the phase information and spectral wavelength of the interference beam when the test surface of the object under test is placed on the optimal focal plane. The control module is used to control the drive unit to drive the stage to move in a direction perpendicular to the plane where the stage is located, so that the relative distance between the stage and the imaging objective reaches the optimal relative distance.

[0021] Optionally, the method further includes: controlling the imaging module to acquire the imaging beam reflected by the detection beam after passing through the object under test when the test surface of the object under test is placed at the optimal focal plane, and to image the object under test to form image information; controlling the data processing module to obtain the image information from the imaging module, and to perform overlay measurement on the image information.

[0022] Compared with the prior art, the optical detection device and method proposed in this invention, on the one hand, calculates the optimal relative distance between the stage and the imaging objective when the object under test is at the optimal focal plane using the principle of white light interferometry with a spectrometer recorder, avoiding multiple image scans, saving scanning time, and improving productivity; on the other hand, it separates the light source of the focusing system and the light source of the imaging system, and uses a special optical path design to provide the two light sources to the focusing system and the imaging system respectively without interfering with each other. In this way, while ensuring productivity, the spectrometer ranging technology can be better utilized. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of an optical detection device provided in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of another optical detection device structure provided in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of an optical detection method provided in an embodiment of the present invention.

[0027] Figure Labels

[0028] The system includes an illumination module 101, a focusing module 102, an imaging module 103, a data processing module 104, a control module 105, and a stage 106.

[0029] Focusing light source 1-1, imaging light source 1-2;

[0030] First beam-splitting plate 2-1, second beam-splitting plate 2-2, third beam-splitting plate 8;

[0031] First mechanical switch 14, second mechanical switch 5;

[0032] 4. Object under test; 3. First imaging objective; 6. Second imaging objective; 7. Reference focal plane;

[0033] 9. Lens; 10. Spectrum recorder;

[0034] Imaging objective lens 11 and camera 12;

[0035] The first polarizer 3-1, the second polarizer 3-2, and the analyzer 3-3. Detailed Implementation

[0036] To make the content of this invention clearer and easier to understand, the following description, in conjunction with the accompanying drawings, further illustrates the invention. Of course, this invention is not limited to this specific embodiment, and common substitutions well-known to those skilled in the art are also covered within the scope of protection of this invention.

[0037] It should be noted that in the following specific embodiments, in order to clearly illustrate the structure of the present invention and facilitate explanation, the structure in the accompanying drawings is not drawn to scale and has been partially enlarged, deformed and simplified. Therefore, it should be avoided to interpret this as a limitation of the present invention.

[0038] Figure 1 This is a schematic diagram of the optical detection device proposed in an embodiment of the present invention. Figure 1 As shown, the optical detection device includes: an illumination module 101, a focusing module 102, an imaging module 103, a data processing module 104, a control module 105, and a stage 106. Wherein:

[0039] The stage 106 is used to hold the object under test 4. The object under test 4 can be a wafer or other semiconductor device.

[0040] An illumination system 101 is used to emit a detection beam towards the object under test 4. For example... Figure 1 As shown, the illumination system 01 includes a focusing light source 1-1, a first mechanical switch 14, an imaging light source 1-2, and a first beam splitter 2-1. The focusing light source 1-1 emits a first detection beam, and the imaging light source 1-2 emits a second detection beam. The focusing light source can be a broadband light source. In one possible embodiment, the focusing light source is a white light source to facilitate distance measurement using a spectrometer. A dual-light source design is employed, utilizing a special optical path design to ensure that the two light sources provide separate light to the focusing system and the imaging system without interference. When the first mechanical switch 14 is open, the first detection beam emitted from the focusing light source 1-1 passes through the first mechanical switch 14, the first beam splitter 2-1, and the second beam splitter 2-2, and enters the object under test 4 and the reference focal plane 7. When the first mechanical switch 14 is closed, the first detection beam emitted from the focusing light source 1-1 does not enter the object under test 4 and the reference focal plane 7.

[0041] The focusing module 102 includes a test surface optical path, a reference surface optical path, and a focal plane measurement optical path. The test surface optical path includes a first imaging objective lens 3 adjacent to the test object 4 and a second beam splitter 2-2; the reference surface optical path includes a second mechanical switch 5, a second imaging objective lens 6, and a reference focal plane 7, where the reference focal plane 7 is the optimal focal plane of a known objective lens. The focal plane measurement optical path includes a third beam splitter 8, a lens 9, and a spectrometer 10. When the second mechanical switch 5 is open, both the first detection beam and the second detection beam pass through the first beam splitter 2-1, the second beam splitter 2-2, and the second imaging objective lens 6 and are incident on the reference focal plane 7. The second reflected beam is formed by reflection from the surface of the reference focal plane 7, and the first reflected beam and the second reflected beam form the interference beam. The interference beam passes through the lens 9 and enters the spectrometer 10.

[0042] During the focal plane measurement stage, the data processing module 104 is used to acquire the phase information and spectral wavelength of the interference beam, and calculate the optimal relative distance between the stage 106 and the imaging objective lens 12 when the test surface of the object under test 4 is placed at the optimal focal plane based on the phase information and spectral wavelength of the interference beam; the control module 104 is used to control the drive unit to drive the stage 7 to move in a direction perpendicular to the plane where the stage is located, so that the relative distance between the stage and the imaging objective lens reaches the optimal relative distance.

[0043] It is worth noting that the optimal focal plane refers to the focal plane with the best imaging effect, and the optimal relative distance refers to the distance between the stage 106 and the imaging objective lens 12 when the object under test is placed at the optimal focal plane. Thus, this device calculates the optimal relative distance between the stage and the imaging objective lens when the object under test is at the optimal focal plane using the principle of white light interferometry with a spectral recorder, avoiding multiple image scans, saving scanning time, and improving productivity.

[0044] The device further includes an imaging module 103, used to acquire the imaging beam formed by the reflection of the detection beam from the object under test 7 when the test surface of the object under test 7 is placed at the optimal focal plane, and to image the object under test 7 to form image information. The data processing module 104 is also used to acquire the image information from the imaging module 12 and perform overlay measurement on the image information.

[0045] See Figure 1During the overlay measurement stage, the imaging module 103 includes a third beam splitter 8, an imaging objective lens 11, and a camera 12. When the surface to be measured of the object under test 4 is positioned at the optimal focal plane, the second detection beam passes through the first beam splitter 2-1, the second beam splitter 2-2, and the first imaging objective lens 3 and is incident on the object under test 4. A third reflected beam is formed by reflection from the surface of the object under test 4. This third reflected beam then passes sequentially through the third beam splitter 8, the imaging objective lens 11, and the camera 12 to form an imaging beam. The camera 12 is used to acquire the imaging beam and image the object under test 4. The data processing module 104 obtains the image information from the imaging module 12 and performs overlay measurement or optical inspection on the image information.

[0046] In another embodiment of the present invention, considering the switching time problem of mechanical switches in optical detection, this embodiment also provides another optical detection device, such as... Figure 2 As shown, the illumination module of this optical testing device includes a focusing light source 1-1, a first polarizer 3-1, a first beam splitter 2-1, an imaging light source 1-2, and a second polarizer 3-2. The focusing module includes a test surface optical path, a reference surface optical path, and a focal plane measurement optical path. The test surface optical path includes a first imaging objective lens 3 and a second beam splitter 2-2 adjacent to the test object 4. The reference surface optical path includes an analyzer 3-3, a second imaging objective lens 6, and a reference focal plane 7. The focal plane measurement optical path includes a third beam splitter 8, a lens 9, and a spectral recorder 10. The polarization direction of the analyzer 3-3 is the same as that of the first polarizer 3-1, but orthogonal to the polarization direction of the second polarizer 3-2.

[0047] During the focal plane measurement process, the first detection beam emitted by the focusing light source 1-1 passes through beam splitters 2-1 and 2-2. One beam enters the imaging optical path to acquire the focal plane information of the object under test 4, and the other beam enters the reference plane optical path to acquire the information of the reference focal plane 7. The reflected beams from the object under test 4 and the reference focal plane 7 are both converged into one beam by beam splitters 2-2 and undergo white light interference. The beam then passes through beam splitter 8 and enters the spectrum recorder 10. The spectrum recorder 10 records the interference pattern and transmits the data signal to the data processing module 13. The data processing module 13 analyzes the phase information of the two arms in the spectral interference fringes. Through phase extraction and unfolding, the absolute distance is detected, and the relative distance between the object plane of the object under test 4 and the reference focal plane can be obtained, thereby achieving focusing. In this embodiment, the accuracy can be achieved within 10 nm, and the entire focal plane measurement process does not require multiple scans.

[0048] During the imaging process, the second detection beam emitted by the imaging light source 1-2 passes through beam splitters 2-1 and 2-2. One beam enters the imaging optical path to acquire the object surface information of the object under test 4, while the other beam enters the reference optical path and is intercepted by the analyzer 5. The reflected light from the object under test 4 passes through the beam splitter 8 and is finally imaged on the camera 12. Due to the special polarization settings, the reflected light from the reference focal plane 7 and the broadband white light emitted by the focusing light source 1-1 do not enter the camera 12, thus having no impact on the imaging.

[0049] Based on the above-described optical detection device, in one possible embodiment, the data processing module 104 is further configured to acquire the light intensity of the interference beam and determine the light intensity adjustment amount of the detection optical path module according to the light intensity of the interference beam; the illumination module 101 is connected to the data processing module 104, and the illumination module 101 is further configured to adjust the light intensity of the detection beam according to the light intensity adjustment amount.

[0050] Figure 3 This is a flowchart of the optical detection method according to an embodiment of the present invention. Figure 3 As shown, this optical detection method can be executed by a controller, and the method includes the following steps:

[0051] S301, control the lighting module to emit a detection beam towards the object under test, the object under test being placed on the stage.

[0052] S302, the focusing module controls the optical components to split the detection beam and direct it into the object under test and the reference focal plane respectively, and then converges it to the spectral recorder through the optical components.

[0053] The spectral recorder is used to record the phase information and spectral wavelength of the interference beam formed by the detection beam after being reflected by the object under test and the reference focal plane, respectively.

[0054] S303, the control data processing module acquires the phase information and spectral wavelength of the interference beam, and calculates the optimal relative distance between the stage and the imaging objective when the test surface of the object under test is placed at the optimal focal plane based on the phase information and spectral wavelength of the interference beam.

[0055] S304, the control drive unit drives the stage to move in a direction perpendicular to the plane where the stage is located, so that the relative distance between the stage and the imaging objective lens reaches the optimal relative distance.

[0056] The method further includes: controlling the imaging module to acquire the imaging beam formed by the reflection of the detection beam from the object under test when the test surface of the object under test is placed at the optimal focal plane, and imaging the object under test to form image information; controlling the data processing module to acquire the image information from the imaging module, and performing overlay measurement on the image information. Additionally, when the optical inspection device does not include a mechanical switch, the controller does not need to control the mechanical switch.

[0057] In summary, compared with the prior art, the optical detection device and method proposed in this invention, on the one hand, calculate the optimal relative distance between the stage and the imaging objective when the object under test is at the optimal focal plane using the principle of white light interferometry with a spectrometer recorder, thereby avoiding multiple image scans, saving scanning time, and improving productivity; on the other hand, by separating the light source of the focusing system and the light source of the imaging system, and using a special optical path design, the two light sources are provided to the focusing system and the imaging system respectively without interfering with each other. In this way, while ensuring productivity, the spectrometer ranging technology can be better utilized.

[0058] The above description is merely a preferred embodiment of the present invention, and the embodiments are not intended to limit the scope of patent protection of the present invention. Therefore, any equivalent structural changes made based on the description and drawings of the present invention should also be included within the scope of protection of the present invention. The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention.

[0059] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An optical detection device, characterized in that, include: The stage is used to hold the object to be measured. An illumination module is used to emit a detection beam toward the object under test; The focusing module includes a test surface optical path, a reference surface optical path, and a focal plane measurement optical path, for use to split the detection beam into the test object and the reference focal plane respectively through optical components, and to converge it to the spectral recorder through optical components; The spectral recorder is used to record the phase information and spectral wavelength of the interference beam formed after the detection beam is reflected by the object under test and the reference focal plane, respectively. The data processing module is used to acquire the phase information and spectral wavelength of the interference beam, and calculate the optimal relative distance between the stage and the imaging objective when the test surface of the object under test is placed at the optimal focal plane based on the phase information and spectral wavelength of the interference beam; wherein, the data processing module obtains the optimal relative distance by analyzing the phase information of the two arms in the spectral interference fringes, and by phase extraction and unfolding to detect the absolute distance. The control module is used to control the drive unit to drive the stage to move in a direction perpendicular to the plane where the stage is located, so that the relative distance between the stage and the imaging objective lens reaches the optimal relative distance.

2. The optical detection device according to claim 1, characterized in that, The device further includes: The imaging module is used to acquire the imaging beam after the detection beam is reflected by the test object when the test surface of the test object is placed at the optimal focal plane, and to image the test object to form image information. The data processing module is also used to acquire the image information from the imaging module and perform overlay measurement on the image information.

3. The optical detection device according to claim 1, characterized in that, The data processing module is also used to acquire the light intensity of the interference beam and determine the light intensity adjustment amount of the detection beam based on the light intensity of the interference beam. The lighting module is connected to the data processing module, and the lighting module is also used to adjust the light intensity of the detection beam according to the light intensity adjustment amount.

4. The optical detection device according to claim 1, characterized in that, The illumination module includes a focusing light source, a first mechanical switch, a first beam splitter, and an imaging light source; the focusing light source is used to emit a first detection beam, the imaging light source is used to emit a second detection beam, and the first mechanical switch is used to control the opening or closing of the focusing optical path corresponding to the first detection beam. The optical path of the surface under test includes a first imaging objective lens and a second beam splitter adjacent to the object under test; the optical path of the reference surface includes a second mechanical switch, a second imaging objective lens and a reference focal plane; the optical path of the focal plane measurement includes a third beam splitter, a lens and a spectrometer. When the first mechanical switch is opened, both the first detection beam and the second detection beam pass through the first beam splitter, the second beam splitter, and the first imaging objective lens and are incident on the object under test, forming a first reflected beam after reflection from the surface of the object under test; and when the second mechanical switch is opened, both the first detection beam and the second detection beam pass through the first beam splitter, the second beam splitter, and the second imaging objective lens and are incident on the reference focal plane, forming a second reflected beam after reflection from the surface of the reference focal plane, the first reflected beam and the second reflected beam forming the interference beam, and the interference beam enters the spectral recorder through the lens.

5. The optical detection device according to claim 4, characterized in that, The imaging module includes a third beam splitter, an imaging objective lens, and a camera. When the test surface of the object under test is placed at the optimal focal plane, the second detection beam passes through the first beam splitter, the second beam splitter, and the first imaging objective lens and is incident on the object under test. The beam is reflected by the surface of the object under test to form a third reflected beam. The third reflected beam passes through the third beam splitter, the imaging objective lens, and the camera in sequence to form an imaging beam. The camera is used to acquire the imaging beam to image the object under test.

6. The optical detection device according to claim 4, characterized in that, The control module is electrically connected to the first mechanical switch and the second mechanical switch respectively. The control module is also used to control the first mechanical switch and the second mechanical switch to open or close simultaneously.

7. The optical detection device according to claim 1, characterized in that, The illumination module includes a focusing light source, a first polarizer, a first beam splitter, an imaging light source, and a second polarizer. The optical path of the surface under test includes a first imaging objective lens and a second beam splitter adjacent to the object under test; the optical path of the reference surface includes an analyzer, a second imaging objective lens, and a reference focal plane; the optical path of the focal plane measurement includes a third beam splitter, a lens, and a spectral recorder; the polarization direction of the analyzer is the same as the polarization direction of the first polarizer, but orthogonal to the polarization direction of the second polarizer.

8. The optical detection device according to claim 4, characterized in that, The focusing light source is a broadband light source.

9. An optical detection method, using the optical detection apparatus as described in any one of claims 1 to 8, characterized in that, include: The control illumination module emits a detection beam toward the object under test, which is placed on a stage. The focusing control module uses optical components to split the detection beam and direct it into the object under test and the reference focal plane respectively, and then focuses it to the spectral recorder through optical components; the spectral recorder is used to record the phase information and spectral wavelength of the interference beam formed by the detection beam after being reflected by the object under test and the reference focal plane respectively; The control data processing module acquires the phase information and spectral wavelength of the interference beam, and calculates the optimal relative distance between the stage and the imaging objective when the test surface of the object under test is placed on the optimal focal plane based on the phase information and spectral wavelength of the interference beam. The control drive unit drives the stage to move in a direction perpendicular to the plane where the stage is located, so that the relative distance between the stage and the imaging objective lens reaches the optimal relative distance.

10. The optical detection method according to claim 9, characterized in that, The method further includes: When the test surface of the object under test is placed at the optimal focal plane, the control imaging module acquires the imaging beam after the detection beam is reflected by the object under test, and forms an image information of the object under test; The data processing module is controlled to acquire the image information from the imaging module and to perform overlay measurement on the image information.

Images