A method for compact nanoscale displacement measurement based on super-oscillating light fields

Abstract

The present invention discloses a method for realizing compact nanoscale displacement measurement based on super-oscillating light field, including: irradiating incident radially polarized light to a super-oscillating lens to generate a super-oscillating nanoscale light field; the super-oscillating nanoscale light field interacts with a silicon scatterer to generate scattered light; the scatterer is displaced in different directions along the nanoscale, and each time it moves, a CCD camera collects a forward scattered light field; and the displacement of the nanoscale scatterer is detected using the scattering signal of the super-oscillating nanoscale light field. The device of the present invention does not rely on a large-sized objective lens, and the super-oscillating lens has a micron-level thin thickness, and can generate a light spot that exceeds the diffraction limit, and has better integration capability and detection accuracy; the directional index parameter is introduced I DX and I DY The actual nanoscale displacement of the scatterer is parametrically modeled, so that the displacement of the scatterer can be reconstructed, which has important application value in industrial production to test whether nano-micro devices deviate from the predetermined installation position.

Description

Technical Field

[0001] The present invention relates to the field of light beam transformation for precision metrology detection and optical scattering metrology technology, and in particular to a method for realizing compact nanometer-level displacement metrology based on a super-oscillating light field. Background Art

[0002] In recent years, the understanding of superoscillating light has led to the development of superoscillating lenses, imaging, and metrology techniques. Dielectric, metallic, and metamaterial nanostructured superoscillating lenses have been introduced that are able to produce smaller hot spots than conventional lenses allow. Far-field, contactless, non-invasive deep subwavelength super-resolution imaging and measurement techniques have also been developed that exploit the high light localization and fast phase changes in superoscillating fields.

[0003] Super-oscillating lenses can easily generate nano-sized light fields, and super-oscillating lenses can be made very thin and have strong integration capabilities, so super-oscillating lenses can be used for precision metrology. Ultra-precision measurement is the cornerstone of the development of high-end equipment technology such as lithography. In the mass production process of semiconductor lithography, precision metrology is used for the rapid and accurate measurement of components and light source related characteristics, and the assessment of nanoparticle contamination in the production environment. It is the most important link in semiconductor lithography technology. Precision metrology determines the success or failure of semiconductor processes and nano-feature characterization. The light field can be divided into near-field and far-field. In the near-field of nanophotonic structures, the complex relationship between electric and magnetic fields is most obvious. Information will change and be lost during transmission. Through the change in the properties of the light field, many precise changes can be understood. Information. Complex electric and magnetic fields usually change on a sub-wavelength scale and lead to many novel photon phenomena, such as enhanced light field scattering, abnormal light momentum, and complex spatial evolution of optical singularities.

[0004] The existing optical detection system currently used to detect nano-scale precision information of nano-objects is based on polarization-controlled directional scattering of nano-position sensing. Nano-objects (such as nanoparticles, nanodisks, nanopillars, nanospheres, etc.) have different responses to light fields of different polarization states (such as linear polarization, circular polarization, radial polarization, etc.) of incident light, so as to characterize the precise information when nano-objects interact with light fields of different polarization states, thereby realizing nano-level position detection and sensing. However, due to the large spot size of the incident light used, the existing optical detection system will use a high numerical aperture lens as the objective lens to focus the incident light to reduce the spot size of the incident light, thereby generating a nanoscale light field that interacts with the commonly used nano-objects, namely nanospheres, to generate scattered light. Due to the weak intensity of the scattered light field, it is usually necessary to place another high numerical aperture lens behind the nanosphere to amplify the forward scattered light field for imaging, and use a CCD camera to collect the forward scattered light field. By analyzing and calculating the light field collected from the CCD camera, the relevant information of the nanospheres as scatterers, including displacement, size, etc., is obtained.

[0005] In the process of implementing the technical method of the embodiment of the present invention, the inventor of this patent found at least the following technical problems in the prior art:

[0006] The existing optical detection system for obtaining displacement information of nano-objects at the nanoscale mainly uses a detection light field that is generated by focusing through a high numerical aperture lens and is higher than the diffraction limit, so the spot size of the detection light field is relatively large. At present, many existing optical detection systems use multiple high numerical aperture lenses to process the light field, which will cause the entire optical detection system to occupy a large space volume. The detection size of the high numerical aperture lens is significantly different from that of the sample to be detected. Therefore, the method of constructing a light field using a high numerical aperture lens is not conducive to integrating the existing optical detection system into a micro-system for operation.

[0007] In summary, the existing nanoscale optical detection methods cannot meet the practical requirements of miniaturization and compactness of nano-precision displacement detection. Summary of the invention

[0008] The embodiment of the present invention provides a method for realizing compact nanoscale displacement measurement based on super-oscillating light field, and provides a detection method based on optical forward scattering which is compact, high-precision, and has practical application value in sample processing positioning such as lithography, and meets the practical use requirements of miniaturization and compactness of nano-precision displacement detection of silicon cubes as nano-samples.

[0009] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is to provide a method for realizing compact nanoscale displacement measurement based on super-oscillating light field, which includes the following steps.

[0010] The incident radially polarized light is irradiated onto the aluminum film surface of the super-oscillating lens to generate a super-oscillating nanoscale light field; the silicon cube is used as a scatterer, and the super-oscillating nanoscale light field interacts with the scatterer to generate scattered light; the scatterer is subjected to nanoscale displacement in different directions, and each time it is moved, the forward scattered light field is collected by a CCD camera; a directional index parameter is introduced I DX and I DY The actual nanoscale displacement of the scatterer is parameterized and modeled so as to detect the displacement of the nanoscale scatterer using a super-oscillating nanoscale light field.

[0011] Optionally, the super-oscillation lens specifically includes: a silicon dioxide substrate; and an aluminum film, which is coated on the silicon dioxide substrate in a concentric ring shape.

[0012] Optionally, the thickness of the aluminum film is 100 nm.

[0013] Optionally, the silicon cube specifically includes: a silicon dioxide substrate; and a silicon regular hexahedron fixed on the silicon dioxide substrate.

[0014] Optionally, the size of the silicon regular hexahedron is 200nm×200nm×200nm.

[0015] Optionally, the scatterer is subjected to nanoscale displacement in different directions, and each time it is moved, the forward scattering light field is collected once by the CCD camera, specifically including: placing the scatterer at the center of the light spot of the super-oscillation lens, so that the forward scattering light field collected by the CCD camera is symmetrically distributed; the scatterer is subjected to nanoscale displacement along the X direction and the Y direction with a step size of 5nm, and each time it is moved, the CCD camera collects the forward scattering light field once; the scatterer is subjected to nanoscale displacement along the -X direction and the -Y direction with a step size of 5nm, and each time it is moved, the CCD camera collects the forward scattering light field once.

[0016] Optionally, the directional index parameter I DX and I DY The mathematical expression for the actual nanoscale displacement with the scatterer is:

[0017] ;

[0018] ;

[0019] The position of the scatterer at the center of the light spot is taken as the origin of the coordinates, and a plane rectangular coordinate system is constructed. The forward scattering light field collected by the CCD camera is transformed to the far field through Fourier transformation. The light field is located in each quadrant of the coordinate system. I 1. I 2. I 3. I 4 are the average values ​​of the light field intensity in the white dotted boxes located in the first quadrant, the second quadrant, the third quadrant and the fourth quadrant of the coordinate system, respectively.

[0020] On the other hand, an embodiment of the present invention also provides a system for realizing compact nanoscale displacement measurement based on super-oscillating light field, comprising: a super-oscillating lens for generating a super-oscillating nanoscale light field based on incident radially polarized light; a silicon cube for generating scattered light after interacting with the super-oscillating nanoscale light field; and a CCD camera for collecting a forward scattered light field each time the scatterer is moved at nanoscale in different directions.

[0021] Optionally, the system further comprises: a radial polarizer for converting incident linearly polarized laser light into incident radially polarized light.

[0022] Optionally, the system further comprises: a three-axis nano-displacement platform for automatically performing nano-scale displacement of the scatterer in different directions.

[0023] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0024] The light field spot size commonly used in existing optical detection systems is relatively large, which is not conducive to detecting information of objects smaller than the spot size, so it is necessary to obtain a smaller light field. The present invention uses the aluminum film surface of the super-oscillating lens as a super-surface structure, and uses the nanometer-sized super-oscillating nanoscale light field generated by the interaction between the incident radially polarized light and the super-surface structure to perform precise displacement positioning. Compared with the traditional use of high numerical aperture lenses to construct light fields, the device of the present invention does not rely on large-sized objective lenses, has a micron-level thickness, and produces a spot size that exceeds the diffraction limit. The super-oscillating nanoscale light field has a smaller spot size and light field characteristics. In addition, because the super-surface structure can be made smaller in size, it can be made to be a few hundred nanometers to tens of microns thick, which is about 10 times smaller than the existing optical detection system with a traditional high numerical aperture lens. 6 times, so it has strong integration capabilities, which provides convenience for the subsequent reduction of the space occupied by the optical path. In addition, the size of the super-oscillation nanoscale light field is small, and the detection accuracy performance will be improved accordingly, and a resolution exceeding the super-oscillation spot size will be obtained.

[0025] Compared with the traditional method of focusing the light field above the diffraction limit by a high numerical aperture lens as a detection method of the light field, the present invention uses the super-oscillating nanoscale light field generated by the super-oscillating lens to interact with the scatterer, uses a CCD camera to collect and process the forward scattered light field, and introduces a directional index parameter I DX and I DY ,Will I DX and I DY By linking it with the nanoscale displacement, the displacement of the scatterer can be reconstructed, which has great application value for industrial production inspection. Because it is difficult to intuitively detect the deviation between the actual installation position and the theoretical position for the installation of nano-sized devices, the directional performance index parameter is introduced. I DX and I DY , and is linked to the nanoscale displacement to measure the deviation from the initial position. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the composition of a system for realizing compact nano-scale displacement measurement based on super-oscillating light field in one embodiment of the present invention;

[0027] Figure 2 It is a schematic diagram of the structure of a super-oscillating lens in one embodiment of the present invention;

[0028] Figure 3A A diagram showing the field distribution of a super-oscillating nanoscale light field in an XY plane in an embodiment of the present invention;

[0029] Figure 3B is an intensity distribution diagram of a super-oscillating nanoscale light field in one embodiment of the present invention;

[0030] Figure 3C A diagram showing the field distribution of a super-oscillating nanoscale light field in an XZ plane in an embodiment of the present invention;

[0031] Figure 3D A diagram showing the field distribution of a super-oscillating nanoscale light field in the YZ plane in one embodiment of the present invention;

[0032] Figure 4A This is a light field distribution diagram collected by a CCD camera in a symmetrical excitation mode in one embodiment of the present invention;

[0033] Figure 4B A light field distribution diagram of a light field collected by a CCD camera in a symmetrical excitation mode in an embodiment of the present invention, which is transformed to a far field through Fourier transformation;

[0034] Figure 4C A light field distribution diagram collected by a CCD camera in an asymmetric excitation mode in one embodiment of the present invention;

[0035] Figure 4D A light field distribution diagram of a light field collected by a CCD camera in an asymmetric excitation mode in one embodiment of the present invention, which is transformed to a far field through Fourier transformation;

[0036] Figure 5 A local light field distribution diagram of a light field collected by a CCD camera at a displacement starting point of a scatterer in one embodiment of the present invention, which is transformed to a far field through Fourier transformation;

[0037] Fig. 6A is the directional index parameter I DX Schematic diagram of the relationship with the actual nanoscale displacement of the scatterer on the X-axis;

[0038] Figure 6B is the directional index parameter I DY Schematic diagram of the relationship with the actual nanoscale displacement of the scatterer on the Y axis. DETAILED DESCRIPTION

[0039] The embodiment of the present invention provides a method for realizing compact nanoscale displacement measurement based on super-oscillating light field, which solves the problem that the existing nanoscale optical detection method cannot meet the actual use requirements of miniaturization and compactness of nano-precision displacement detection.

[0040] In order to better understand the method of realizing compact nanoscale displacement measurement based on super-oscillating light field in an embodiment of the present invention, a detailed description will be given below in conjunction with the drawings and specific implementation methods of the specification. Obviously, the embodiments described in the present invention are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] Please refer to the following Figure 1 , a method for realizing compact nanoscale displacement measurement based on super-oscillating light field, comprising the following steps.

[0042] Step 10: Irradiate the incident radially polarized light onto the aluminum film surface of the super-oscillating lens to generate a super-oscillating nanoscale light field.

[0043] In the specific implementation process of step 10, for example, the aluminum film surface of the super-oscillating lens is used as the super-surface structure, and the incident radially polarized light can be directly used as the light source, so that the incident radially polarized light interacts with the super-surface structure to generate a super-oscillating nanoscale light field. When the incident linearly polarized laser is used as the light source, a radial polarizer is required to first convert the incident linearly polarized laser into incident radially polarized light.

[0044] Next, FDTD simulation software was used to perform simulation operations, setting the radial polarized light with a wavelength of 633nm as the light source to illuminate the super-oscillating lens, and generating a super-oscillating light field with a focal depth of about 2um at a distance of about 3.2um from the super-oscillating lens. FIG. 3A to FIG. 3D As shown, similar to the Rayleigh criterion Rr=0.61×λ / NA, using the super-oscillation criterion formula r s =0.38×λ / NA is used to verify the generated super-oscillation nanoscale light field. By comparing the super-oscillation criterion with the Rayleigh criterion, it is found that the super-oscillation light field has the characteristic of smaller spot size, which also shows that the super-oscillation light field has stronger resolution. The super-oscillation nanoscale light field is verified by using the super-oscillation criterion formula, where the incident light wavelength λ is 633nm, the super-oscillation lens numerical aperture NA=n×sinα, where n is the refractive index of air, α is half of the aperture angle, and the super-oscillation lens numerical aperture NA is calculated to be 0.975, and Rr=400nm is calculated. r s =249.4nm. When FWHM< r s When , the light field can be considered as a super-oscillating nanoscale light field. Figure 3B As shown, FWHM = 221nm, which is less than 249.4nm. Based on this, it can be determined that the nanostructure light field generated by radially polarized light irradiating the super-oscillating lens is a super-oscillating nanoscale light field.

[0045] like Figure 2 As shown, the super-oscillation lens specifically includes: a silicon dioxide substrate; an aluminum film, which is coated on the silicon dioxide substrate in a concentric ring shape.

[0046] The thickness of the aluminum film is from several hundred nanometers to several tens of micrometers. Preferably, the thickness d of the aluminum film is set to 100 nm.

[0047] A method for manufacturing a super-oscillating lens comprises the following sub-steps:

[0048] Step 101: uniformly coating a layer of aluminum film on a silicon dioxide substrate;

[0049] Step 102: A thin aluminum film supported on a silicon dioxide substrate is milled by focused ion beam milling to obtain 25 opaque concentric ring structures.

[0050] Step 20: The silicon cube is used as a scatterer, and the super-oscillating nanoscale light field interacts with the scatterer to produce scattered light.

[0051] In the specific implementation process of step 20, for example, when the center position of the ultra-oscillating nanoscale light field spot and the center of the scatterer are located in a straight line, this scenario is called a symmetric excitation mode, such as Figure 4A and Figure 4B As shown; when the center position of the super-oscillating nanoscale light field spot is offset from the center of the scatterer, this scenario is called an asymmetric excitation mode, as shown in Figure 4C and Figure 4D Both scattering modes can be characterized using the transmission matrix.

[0052] Under symmetrical excitation conditions, the scattering vector is mainly composed of the first two components s1 and s2, as shown in the following equation:

[0053] .

[0054] Under asymmetric excitation conditions, in addition to the two components g1 and g2, the additional phase term in the scattering vector causes non-zero components g3, g4, ... g n , as shown below:

[0055] .

[0056] In the case of displacements of different magnitudes, the interaction effects of the various components are different, so the scattering field patterns excited are also different.

[0057] The silicon cube specifically includes: a silicon dioxide substrate; a silicon regular hexahedron fixed on the silicon dioxide substrate. The size of the silicon regular hexahedron is 200nm×200nm×200nm, which is a preferred size and can be set according to actual use requirements, and the present invention does not limit it.

[0058] A method for making a silicon cube comprises the following sub-steps;

[0059] Step 201: The material of the silicon cube is silicon.

[0060] Step 202: On the silicon dioxide substrate, first cover it with a mask plate, the height of which is 200nm, leaving a rectangular hole with a size of 200nm×200nm in the center of the mask plate, grow silicon in the rectangular hole, and finally obtain a silicon regular hexahedron with a size of 200nm×200nm×200nm.

[0061] Step 30: The scatterer is displaced in nanometer scale in different directions. Each time it is moved, the forward scattering light field is collected by a CCD camera.

[0062] Step 30 specifically includes:

[0063] Step 301: Place the scatterer at the center of the light spot of the super-oscillation lens, so that the forward scattering light field collected by the CCD camera is symmetrically distributed. The position of the scatterer at the center of the light spot of the super-oscillation lens is used as the coordinate origin O and a plane rectangular coordinate system is constructed. The light field collected by the CCD camera is transformed to the far field through Fourier transformation. The light field is located in each quadrant of the coordinate system. In order to reduce the impact of the projected light field on the analysis results, four symmetrically located and equal-sized areas are selected in the outermost light lobes for analysis, such as Figure 5 shown.

[0064] Step 302: Move the scatterer in nanometer scale along the X direction and the Y direction with a step length of 5 nm. Each time the scatterer moves, the CCD camera collects the forward scattered light field.

[0065] Step 303: The scatterer is moved in nanometer scale along the -X direction and the -Y direction with a step length of 5 nm. Each time it moves, the CCD camera collects the forward scattering light field.

[0066] Step 40: Introducing the Directional Index Parameter I DX and I DY It is linked to the actual nanoscale displacement of the scatterer so as to use the super-oscillating nanoscale light field to detect the displacement of the nanoscale scatterer.

[0067] Directivity Index Parameters I DX and I DY The mathematical expression for the actual nanoscale displacement with the scatterer is:

[0068] ;

[0069] ;

[0070] The position of the scatterer at the center of the light spot is taken as the origin of the coordinates, and a plane rectangular coordinate system is constructed. The forward scattering light field collected by the CCD camera is transformed to the far field through Fourier transformation. The light field is located in each quadrant of the coordinate system. I 1. I 2. I 3. I4 are the average values ​​of the light field intensity in the white dotted boxes located in the first quadrant, the second quadrant, the third quadrant and the fourth quadrant of the coordinate system, respectively.

[0071] Fig. 6A and Figure 6B It shows the actual nanoscale displacement and directional index parameters of the scatterer on the X and Y axes. I DX and I DY From the figure, we can see that the directional index parameter I DX and I DY It has good linear representation for nanoscale displacements in both the X-axis and Y-axis directions.

[0072] like Figure 1 As shown, another embodiment of the present invention provides a system for realizing compact nano-scale displacement measurement based on super-oscillating light field, comprising:

[0073] A super-oscillating lens for generating a super-oscillating nanoscale light field based on incident radially polarized light;

[0074] Silicon cubes for generating scattered light after interaction with ultraoscillating nanoscale light fields;

[0075] The CCD camera is used to collect the forward scattered light field each time the scatterer is displaced in nanometer scale in different directions.

[0076] Preferably, the system further comprises: a radial polarizer for converting incident linearly polarized laser light into incident radially polarized light.

[0077] Preferably, the system further comprises: a three-axis nano-displacement platform for automatically performing nano-scale displacement of the scatterer in different directions.

[0078] Preferably, along the transmission direction of light, the system also includes a light source, a plane mirror 1, a plane mirror 2, an X-linear polarizer, a beam scaling device, a plane mirror 3, an aperture stop, and a lens.

[0079] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for realizing compact nanoscale displacement measurement based on super-oscillating light field, characterized in that: include: The incident radially polarized light is irradiated onto the aluminum film surface of the super-oscillating lens to generate a super-oscillating nanoscale light field; A silicon cube is used as a scatterer, and the super-oscillating nanoscale light field interacts with the scatterer to generate scattered light; The scatterer is displaced in nanometer scale in different directions, and each time it is moved, a forward scattering light field is collected by a CCD camera; Introducing the Directivity Index Parameter I DX and I DY The nanometer-scale displacement actually performed by the scatterer is linked to the super-oscillating nanometer-scale light field so as to detect the displacement of the nanometer-scale scatterer.

2. The method according to claim 1, characterized in that The super-oscillating lens specifically comprises: Silicon dioxide substrate; The aluminum film is plated on the silicon dioxide substrate in a concentric ring shape.

3. The method according to claim 2, characterized in that The thickness of the aluminum film is 100 nm.

4. The method according to claim 1, characterized in that The silicon cube specifically comprises: Silica substrate; The silicon regular hexahedron is fixed on the silicon dioxide substrate.

5. The method according to claim 4, characterized in that The size of the silicon regular hexahedron is 200nm×200nm×200nm.

6. The method according to claim 1, characterized in that The scatterer is subjected to nanometer-scale displacement in different directions, and each time the scatterer is moved, a forward scattering light field is collected by a CCD camera, specifically comprising: Placing the scatterer at the center of the light spot of the super-oscillating lens so that the forward scattering light field collected by the CCD camera is symmetrically distributed; The scatterer is moved in nanometer scale along the X direction and the Y direction with a step length of 5 nm, and each time it moves, the CCD camera collects a forward scattering light field; The scatterer is moved in nanometer scale along the -X direction and the -Y direction with a step length of 5 nm. Each time it moves, the CCD camera collects a forward scattering light field.

7. The method according to claim 1, characterized in that The directional index parameter I DX and I DY The mathematical expression for the actual nanoscale displacement with the scatterer is: ； ； The position of the scatterer at the center of the light spot is taken as the origin of the coordinates, and a plane rectangular coordinate system is constructed. The forward scattering light field collected by the CCD camera is transformed to the far field through Fourier transformation. The light field is located in each quadrant of the coordinate system. I 1. I 2. I 3. I 4 are the average values ​​of the light field intensity in the white dotted boxes located in the first quadrant, the second quadrant, the third quadrant and the fourth quadrant of the coordinate system, respectively.

8. A system for compact nanoscale displacement measurement based on super-oscillating light fields, characterized in that: include: A super-oscillating lens for generating a super-oscillating nanoscale light field based on incident radially polarized light; a silicon cube for generating scattered light after interacting with the super-oscillating nanoscale light field; The CCD camera is used to collect the forward scattered light field every time the scatterer is displaced in different directions at the nanoscale; the directional index parameter is introduced I DX and I DY The nanometer-scale displacement actually performed by the scatterer is linked to the super-oscillating nanometer-scale light field so as to detect the displacement of the nanometer-scale scatterer.

9. The system according to claim 8, characterized in that The system further comprises: Radial polarizers are used to convert incident linearly polarized laser light into incident radially polarized light.

10. The system according to claim 8, characterized in that The system further comprises: The three-axis nano-displacement platform is used to automatically displace the scatterer in different directions at the nanoscale.

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