Dark-field confocal microscopic measurement device and method based on vortex light aperture scanning

Abstract

The present application discloses a dark-field confocal microscopic measurement device and method based on vortex light aperture scanning, which relates to the technical field of optical precision measurement. The device includes: a vortex light generation module, a vortex light aperture scanning module, a sample scanning module, and a dark-field lock-in detection module. On the one hand, the vortex light aperture scanning module is used to realize the scanning of the focused spot focused on the sample within a small range on the sample, generating an oscillation signal to highlight the scattering signal of the nano-scale defects of the sample. On the other hand, the dark-field lock-in detection module is used to realize the detection of high-sensitivity oscillation signals. In the present invention, the combination of the small-range scanning of the vortex light aperture and the dark-field lock-in detection function realizes the high-sensitivity detection of defects smaller than 50 nanometers.

Description

Technical Field

[0001] The present application relates to the field of optical precision measurement technology, and particularly to a dark-field confocal microscopic measurement device and method based on vortex light aperture scanning. Background Art

[0002] High-energy optical components and semiconductor wafers have extensive applications in precision instrument manufacturing and major optoelectronic engineering research. Defect detection of optical components and semiconductor devices effectively guarantees the product yield and improves production efficiency. At present, the detection requirements for optical components and semiconductor components are transitioning from surface defect detection to subsurface and interlayer defect detection.

[0003] Confocal microscopic measurement technology has become an important means for non-destructive detection of optical components and semiconductor wafers due to its advantages of good optical tomography ability and high-resolution imaging. Traditional confocal microscopy technology cannot effectively separate surface reflection information and subsurface scattering information, and is limited in the detection of subsurface of optical components and interlayer defects of semiconductor integrated circuits. As an important branch of confocal microscopic measurement technology, dark-field confocal measurement technology collects the scattering signals of light sources in samples under dark-field background conditions to achieve non-fluorescent labeling, high-contrast, and high-resolution microscopic imaging. Since dark-field confocal microscopy technology can effectively suppress surface reflected light, it provides a new way for surface and subsurface detection of components.

[0004] However, due to factors such as beam diffraction and sample multiple scattering effects, the measurement of ordinary optical dark-field confocal microscopic measurement technology has insufficient signal-to-noise ratio for detecting nano-scale micro-defects. Generally, the detection scale is limited to more than 50 nm, the overall defect detection rate is insufficient, and it is easy to miss the detection of micro-defects smaller than 50 nm. Therefore, developing high-sensitivity defect detection technology is an urgent problem to be solved in the industrial detection field. Summary of the Invention

[0005] The purpose of the present application is to provide a dark-field confocal microscopic measurement device and method based on vortex light aperture scanning, which can achieve high-sensitivity detection of micro-defects smaller than 50 nm through the combination of a vortex aperture scanning module and a dark-field lock-in detection module.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] In a first aspect, the present application provides a dark-field confocal microscopic measurement device based on vortex light aperture scanning, including: a vortex light generation module, a vortex light aperture scanning module, a sample scanning module, and a dark-field lock-in detection module;

[0008] The vortex light generation module is used to generate vortex light;

[0009] The vortex light aperture scanning module sequentially includes, along the light propagation direction of the vortex light generated by the vortex light generation module: a reflecting mirror, a single-axis scanning galvanometer, a beam expander, a non-polarizing beam splitter, and an objective lens;

[0010] The non-polarizing beam splitter is used to split the beam output by the beam expander and the signal return light reflected by the sample;

[0011] The objective lens is used to focus the beam output by the beam expander after beam splitting onto the sample and collect the signal return light and incident it on the non-polarizing beam splitter;

[0012] The single-axis scanning galvanometer is used to control the beam transmission direction of the vortex light reflected by the reflecting mirror so that the dark spot at the center of the vortex light incident on the objective lens deviates from the center of the entrance pupil and moves back and forth within the entrance pupil range of the objective lens during the scanning process, and the focused spot focused on the sample oscillates back and forth within a small range of the sample; the size of the scanning range is determined by the aperture and wavelength of the objective lens;

[0013] The sample scanning module is used to control the movement of the sample during the scanning process so that the focused spot on the sample performs two-dimensional scanning or three-dimensional scanning within the sample;

[0014] The dark field lock-in detection module sequentially includes, along the light propagation direction of the signal return light split by the non-polarizing beam splitter: a diaphragm, a focusing lens, a pinhole, a photomultiplier tube, and a lock-in amplifier;

[0015] The diaphragm is used to filter out the reflected light in the signal return light and retain the scattered light at the center of the beam;

[0016] The focusing lens is used to focus the scattered light output by the diaphragm and incident it on the photomultiplier tube through the pinhole; the photomultiplier tube is used to convert the optical signal of the received scattered light into an electrical signal; the lock-in amplifier is used to perform lock-in amplification processing on the electrical signal output by the photomultiplier tube.

[0017] In a second aspect, the present application provides a dark field confocal microscopic measurement method based on vortex light aperture scanning, which is implemented based on the dark field confocal microscopic measurement device based on vortex light aperture scanning, and includes:

[0018] The vortex light generated by the vortex light generation module is incident on the reflecting mirror;

[0019] The vortex light reflected by the reflecting mirror is incident on the single-axis scanning galvanometer, and the single-axis scanning galvanometer is used to control the beam transmission direction of the vortex light reflected by the reflecting mirror;

[0020] The beam output by the single-axis scanning galvanometer is incident on the non-polarizing beam splitter through the beam expander;

[0021] The non-deflecting beam splitter splits the beam output by the beam expander and is incident on the objective lens; during the scanning process, the dark spot at the center of the vortex light incident on the objective lens moves back and forth within the objective pupil range, deviating from the pupil center.

[0022] The beam output by the objective lens is focused on the sample; the focused spot focused on the sample scans within a small range of the sample; the size of the small range is determined according to the aperture and wavelength of the objective lens.

[0023] The signal return light reflected by the sample is incident on the non-polarizing beam splitter through the objective lens.

[0024] The non-polarizing beam splitter splits the signal return light reflected by the sample and is incident on the aperture stop to filter out the reflected light in the signal return light and retain the scattered light at the center of the beam.

[0025] The beam output by the aperture stop is incident on the photomultiplier tube after passing through the focusing lens and the pinhole in sequence.

[0026] The photomultiplier tube converts the optical signal of the received scattered light into an electrical signal and outputs the electrical signal to the lock-in amplifier.

[0027] The lock-in amplifier performs lock-in amplification processing on the electrical signal output by the photomultiplier tube.

[0028] According to the specific embodiments provided in this application, the following technical effects are disclosed in this application:

[0029] This application provides a dark-field confocal microscopic measurement device and method based on vortex light aperture scanning. On the one hand, the vortex light aperture scanning technology is introduced. The beam propagation direction of the vortex light can be controlled by a single-axis scanning galvanometer, so that during the scanning process, the vortex light incident on the objective lens moves back and forth within the objective pupil range, deviating from the pupil center. By this movement, the equivalent orbital angular momentum order of the vortex light is changed, and the focused spot focused on the sample scans within a small range of the sample, generating an oscillation signal to highlight the scattering signal of the nano-scale defects of the sample. On the other hand, during the scanning process, the generated oscillation signal is detected with high sensitivity using the lock-in amplification detection technology. In the present invention, the combination of the small-range scanning of the vortex light aperture and the dark-field lock-in detection function realizes the high-sensitivity detection of defects smaller than 50 nanometers. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1Schematic structural diagram of a dark-field confocal microscopic measurement device based on vortex light aperture scanning in an embodiment of the present application;

[0032] Figure 2 Flow schematic diagram of a dark-field confocal microscopic measurement method based on vortex light aperture scanning provided in an embodiment of the present application.

[0033] Reference numerals:

[0034] 1 - Laser; 2 - Spiral phase plate; 3 - Reflecting mirror; 4 - Uniaxial scanning galvanometer; 5 - Beam expander; 6 - Non-polarizing beam splitter; 7 - Objective lens; 8 - Sample; 9 - Three-dimensional displacement stage; 10 - Diaphragm; 11 - Focusing lens; 12 - Pinhole; 13 - Photomultiplier tube; 14 - Lock-in amplifier; 15 - Signal generator. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0036] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0037] As Figure 1 shown, this embodiment provides a dark-field confocal microscopic measurement device based on vortex light aperture scanning, which is used to realize the small-range scanning of the vortex light aperture of the sample and the dark-field lock-in detection function. The device specifically includes: a vortex light generation module, a vortex light aperture scanning module, a sample scanning module, and a dark-field lock-in detection module.

[0038] The vortex light generation module is used to generate vortex light. As Figure 1 shown, the vortex light generation module sequentially includes, in the light propagation direction: a laser 1 and a spiral phase plate 2; the spiral phase plate 2 is used to convert the laser output by the laser 1 into vortex light. Among them, the laser 1 outputs laser light in the visible light band, which is incident on the spiral phase plate 2. The center of the spiral phase plate 2 coincides with the center of the laser optical axis, generating first-order vortex light.

[0039] The vortex light aperture scanning module sequentially includes, in the light propagation direction of the vortex light generated by the vortex light generation module: a reflecting mirror 3, a uniaxial scanning galvanometer 4, a beam expander 5, a non-polarizing beam splitter 6, and an objective lens 7.

[0040] The non-polarizing beam splitter 6 is used to split the light beam output by the beam expander 5 and the signal return light reflected by the sample 8.

[0041] The objective lens 7 is used to focus the light beam output by the beam expander 5 after beam splitting onto the sample 8, collect the signal return light, and incident it on the non-polarizing beam splitter 6.

[0042] The single-axis scanning galvanometer 4 is used to control the beam transmission direction of the vortex light reflected by the mirror 3, so that the dark spot at the center of the vortex light incident on the objective lens 7 deviates from the pupil center and moves back and forth within the pupil range of the objective lens 7 during the scanning process. By this movement, the equivalent orbital angular momentum order of the vortex light is changed, and the focused spot focused on the sample 8 scans within a small range of the sample 8; the size of the small range is determined according to the aperture and wavelength of the objective lens 7, specifically 5 to 10 times of Na / 2λ. Na represents the aperture of the objective lens 7, and λ represents the wavelength. Taking the first-order vortex light generated above as an example, the order of the vortex light deviating from the pupil center is near the first order above, so it is described as the equivalent orbital angular momentum order.

[0043] The optical path propagation process of each structure in the vortex light aperture scanning module is as follows: The generated vortex light is incident on the single-axis scanning galvanometer 4 by the mirror 3. The single-axis scanning galvanometer 4 controls the change of the beam propagation direction. The reflected light of the single-axis scanning lens is expanded by the beam expander 5 and split by the non-polarizing beam splitter 6 and then incident on the objective lens 7, and is focused on the sample 8. The focused spot scans within a small range of the sample 8. At the same time, the dark spot at the center of the vortex light deviates from the pupil center and moves within the pupil range of the objective lens 7 during the scanning process, and finally an oscillation signal is generated during the vortex light scanning process. The signal return light reflected by the sample 8 is collected by the objective lens 7 and then split by the non-polarizing beam splitter 6 and reflected to the optical path of the subsequent dark-field lock-in detection module.

[0044] The sample scanning module is used to control the movement of the sample 8 during the scanning process so that the focused spot on the sample 8 performs two-dimensional scanning or three-dimensional scanning within the sample 8.

[0045] As Figure 1 shown, the sample scanning module includes a three-dimensional displacement stage 9; the sample 8 is located on the three-dimensional displacement stage 9. Among them, by moving the three-dimensional displacement stage 9 to drive the movement of the sample 8, it is possible to control the residence time of the focused spot focused on the sample 8 at the scanning point to be greater than 2 to 3 times of the scanning period.

[0046] The dark-field lock-in detection module successively includes: a diaphragm 10, a focusing lens 11, a pinhole 12, a photomultiplier tube 13, and a lock-in amplifier 14 according to the light propagation direction of the signal return light split by the non-polarizing beam splitter 6.

[0047] The diaphragm 10 is used to filter out the reflected light in the signal return light and retain the scattered light at the center of the light beam.

[0048] The focusing lens 11 is used to focus the scattered light output by the diaphragm 10 and make it incident on the photomultiplier tube 13 through the pinhole 12.

[0049] The photomultiplier tube 13 is used to convert the optical signal of the received scattered light into an electrical signal.

[0050] The lock-in amplifier 14 is used to perform lock-in amplification processing on the electrical signal output by the photomultiplier tube 13.

[0051] The optical path propagation process of each structure in the dark-field lock-in detection module is as follows: The aperture of the diaphragm 10 is adjusted to the size of the central dark spot of the vortex light. The diaphragm 10 filters out the approximately annular reflected light in the signal return light, retains the central solid scattered light, and performs dark-field detection through the focusing lens 11, the pinhole 12, and the photomultiplier tube 13. The output signal of the photomultiplier tube is connected to the lock-in amplifier 14. After being amplified by the lock-in amplifier 14, a weak oscillation signal scattered with high sensitivity during the scanning process is output. The high-sensitivity detection of defects smaller than 50 nanometers is achieved through the amplification effect of the oscillation signal on the defect scattering.

[0052] As an alternative embodiment, the dark-field lock-in detection module further includes a signal generator 15; the signal generator 15 is used to control the scanning frequencies of the single-axis scanning galvanometer 4 and the lock-in amplifier 14. Among them, the reference signal of the lock-in amplifier 14 is provided by the signal generator 15. The scanning frequency of the lock-in amplifier 14 is the same as that of the single-axis scanning galvanometer 4, and the phase difference between the control signal of the lock-in amplifier 14 and the control signal of the single-axis scanning galvanometer 4 is a fixed value. As an example, the scanning frequencies of the single-axis scanning galvanometer 4 and the lock-in amplifier 14 are greater than 1 kHz. In the present invention, the signal output by the signal generator 15 to the single-axis scanning galvanometer 4 is used to control the propagation direction of the light beam by the single-axis scanning galvanometer 4.

[0053] In this embodiment, in the vortex light aperture scanning technology, the setting of the single-axis scanning galvanometer 4 enables the light beam to scan a small range of the sample 8, generating an oscillation signal. The scattering signal of defects smaller than nanometers is highlighted through the oscillation signal, which is beneficial to the detection of defects smaller than 50 nm. In the dark-field lock-in amplification detection technology, the oscillation signal is collected with high sensitivity through the dark-field lock-in amplification technology, which is beneficial to the detection of defects smaller than 50 nm.

[0054] The present application also provides an application scenario, which applies the above dark-field confocal microscopic measurement device based on vortex light aperture scanning. Specifically: The dark-field confocal microscopic measurement device based on vortex light aperture scanning provided in this embodiment can be applied to the defect detection scenarios of optical elements and semiconductor devices. The defect detection link in the defect detection scenarios of optical elements and semiconductor devices where the dark-field confocal microscopic measurement device based on vortex light aperture scanning provided in this embodiment is applied.

[0055] Based on the same inventive concept, an embodiment of the present application also provides a dark-field confocal microscopic measurement method based on vortex light aperture scanning. The solution provided by this method to solve the problem is similar to the solution recorded in the above device. Therefore, the specific limitations in the embodiment of the dark-field confocal microscopic measurement method based on vortex light aperture scanning provided below can refer to the limitations on the dark-field confocal microscopic measurement device based on vortex light aperture scanning in the above text, and will not be repeated here.

[0056] In an exemplary embodiment, as Figure 2 shown, a dark-field confocal microscopic measurement method based on vortex light aperture scanning is provided, including:

[0057] Step 201, the vortex light generated by the vortex light generation module is incident on the mirror 3.

[0058] Step 202, the vortex light reflected by the mirror 3 is incident on the single-axis scanning galvanometer 4, and the single-axis scanning galvanometer 4 is used to control the beam transmission direction of the vortex light reflected by the mirror 3.

[0059] Step 203, the beam output by the single-axis scanning galvanometer 4 is incident on the non-polarizing beam splitter 6 through the beam expander 5.

[0060] Step 204, the non-deflecting beam splitter splits the beam output by the beam expander 5 and is incident on the objective lens 7. During the scanning process, the dark spot at the center of the vortex light incident on the objective lens 7 moves back and forth within the entrance pupil of the objective lens 7 and deviates from the center of the entrance pupil.

[0061] Step 205, the beam output by the objective lens 7 is focused on the sample 8; the focused spot focused on the sample 8 scans within a small range of the sample 8; the size of the small range is determined according to the aperture and wavelength of the objective lens 7.

[0062] Step 206, the signal return light reflected by the sample 8 is incident on the non-polarizing beam splitter 6 through the objective lens 7.

[0063] Step 207, the non-polarizing beam splitter 6 splits the signal return light reflected by the sample 8 and is incident on the aperture stop 10 to filter out the reflected light in the signal return light and retain the scattered light at the center of the beam.

[0064] Step 208: The light beam output by the diaphragm 10 is incident on the photomultiplier tube 13 after passing through the focusing lens 11 and the pinhole 12 in sequence.

[0065] Step 209: The photomultiplier tube 13 converts the optical signal of the scattered light received into an electrical signal and outputs the electrical signal to the lock-in amplifier 14.

[0066] Step 210: The lock-in amplifier 14 performs lock-in amplification processing on the electrical signal output by the photomultiplier tube 13.

[0067] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0068] Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A dark-field confocal microscopic measurement device based on vortex light aperture scanning, characterized in that, Including: a vortex light generation module, a vortex light aperture scanning module, a sample scanning module, and a dark field lock-in detection module; the vortex light generation module is used to generate vortex light; the vortex light aperture scanning module sequentially includes, along the light propagation direction of the vortex light generated by the vortex light generation module: a reflecting mirror, a uniaxial scanning galvanometer, a beam expander, a non-polarizing beam splitter, and an objective lens; the non-polarizing beam splitter is used to split the beam output by the beam expander and the signal return light reflected by the sample; the objective lens is used to focus the beam output by the beam expander after splitting on the sample and collect the signal return light and incident it on the non-polarizing beam splitter; the uniaxial scanning galvanometer is used to control the beam transmission direction of the vortex light reflected by the reflecting mirror so that the dark spot at the center of the vortex light incident on the objective lens deviates from the center of the entrance pupil and moves back and forth within the entrance pupil range of the objective lens during the scanning process, and the focused spot focused on the sample oscillates back and forth within a small range of the sample; the size of the range is determined according to the aperture and wavelength of the objective lens, specifically 5 to 10 times of Na / 2λ; Na represents the aperture of the objective lens, and λ represents the wavelength; the sample scanning module is used to control the movement of the sample during the scanning process so that the focused spot on the sample performs two-dimensional scanning or three-dimensional scanning within the sample; the dark field lock-in detection module sequentially includes, along the light propagation direction of the signal return light split by the non-polarizing beam splitter: a diaphragm, a focusing lens, a pinhole, a photomultiplier tube, and a lock-in amplifier; the diaphragm is used to filter out the reflected light in the signal return light and retain the scattered light at the center of the beam; the focusing lens is used to focus the scattered light output by the diaphragm and incident it on the photomultiplier tube through the pinhole; the photomultiplier tube is used to convert the optical signal of the received scattered light into an electrical signal; the lock-in amplifier is used to perform lock-in amplification processing on the electrical signal output by the photomultiplier tube.

2. The dark-field confocal microscopic measurement device based on vortex light aperture scanning according to claim 1, wherein the vortex light generation module sequentially includes, along the light propagation direction: a laser and a spiral phase plate; the spiral phase plate is used to convert the laser output by the laser into vortex light.

3. The dark-field confocal microscopic measurement device based on vortex light aperture scanning according to claim 2, wherein the center of the spiral phase plate coincides with the center of the laser optical axis; the vortex light is first-order vortex light.

4. The dark-field confocal microscopic measurement device based on vortex light aperture scanning according to claim 1, characterized in that, the sample scanning module includes a three-dimensional displacement stage; the sample is located on the three-dimensional displacement stage.

5. The dark-field confocal microscopic measurement device based on vortex light aperture scanning according to claim 4, wherein the residence time of the focused spot focused on the sample at the scanning point is greater than a preset residence time; the preset residence time is 2 to 3 times of the scanning period.

6. The dark-field confocal microscopic measurement device based on vortex light aperture scanning according to claim 1, characterized in that the dark field lock-in detection module further includes a signal generator; the signal generator is used to control the scanning frequencies of the uniaxial scanning galvanometer and the lock-in amplifier.

7. The dark-field confocal microscopic measurement device based on vortex light aperture scanning according to claim 6, characterized in that the scanning frequencies of the uniaxial scanning galvanometer and the lock-in amplifier are the same, and the phase difference of the control signals of the uniaxial scanning galvanometer and the lock-in amplifier is a fixed value.

8. The dark-field confocal microscopic measurement device based on vortex light aperture scanning according to claim 7, wherein, the scanning frequencies of the uniaxial scanning galvanometer and the lock-in amplifier are greater than 1 kHz.

9. A dark-field confocal microscopic measurement method based on vortex light aperture scanning, characterized in that, the method of the dark field confocal microscopy measurement device based on vortex light aperture scanning is implemented based on the dark field confocal microscopy measurement device based on vortex light aperture scanning according to any one of claims 1 to 8, including: the vortex light generated by the vortex light generation module is incident on the reflecting mirror; The vortex light reflected by the mirror is incident on the single-axis scanning galvanometer, and the single-axis scanning galvanometer is used to control the beam transmission direction of the vortex light reflected by the mirror; The beam output by the single-axis scanning galvanometer is incident on the beam expander and then on the non-polarizing beam splitter; The non-deflecting beam splitter splits the beam output by the beam expander and is incident on the objective lens; during the scanning process, the dark spot at the center of the vortex light incident on the objective lens moves back and forth within the objective pupil range and deviates from the pupil center; The beam output by the objective lens is focused on the sample; the focused spot focused on the sample scans within a small range of the sample; the size of the small range is determined according to the aperture and wavelength of the objective lens, specifically 5 to 10 times of Na / 2λ; Na represents the aperture of the objective lens, and λ represents the wavelength; The signal return light reflected by the sample is incident on the non-polarizing beam splitter through the objective lens; The non-polarizing beam splitter splits the signal return light reflected by the sample and is incident on the aperture to filter out the reflected light in the signal return light and retain the scattered light at the beam center; The beam output by the aperture is incident on the photomultiplier tube after passing through the focusing lens and the pinhole in sequence; The photomultiplier tube converts the optical signal of the received scattered light into an electrical signal and outputs the electrical signal to the lock-in amplifier; The lock-in amplifier performs lock-in amplification processing on the electrical signal output by the photomultiplier tube.

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