Method for manufacturing metaoptics devices, detection method, and measuring device

Abstract

This disclosure aims to provide a method for manufacturing a meta-optics device that can easily form meta-atoms, a detection method for detecting how a structure is formed without damaging the structure, and a measuring device that can be used in the detection method. [Solution] The method comprises forming a plurality of first structures using nanoimprint lithography, and then using nanoimprint lithography to form a plurality of second structures smaller than the plurality of first structures from the plurality of first structures.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a meta-optics device, a detection method, and a measuring apparatus.

Background Art

[0002] A metamaterial is an artificial material that exhibits behaviors not found in natural substances. The artificial components in a metamaterial are called meta-atoms. Among these artificial materials, optical elements are referred to as optical metamaterials or meta-optics devices. The size of these meta-atoms is shorter than the wavelength of light. An example of a meta-optics device is a metalens. A metalens forms a subwavelength meta-atom pattern to manipulate incident light. Non-Patent Document 1 discloses a planar metalens in the visible light region. This metalens is a planar lens composed of a plurality of rectangular parallelepiped meta-atoms made of TiO2, which is manufactured by forming a pattern of an electron beam resist in the shape of meta-atoms on a synthetic quartz glass substrate by electron beam lithography, depositing amorphous TiO2 by atomic layer deposition (ALD), and lift-off.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Manufacturing meta-optics devices requires tiny metaatoms shorter than the wavelength of light, fabricated with dimensional tolerances of around one order of nanometers. Attempting to form such metaatoms using electron beam lithography results in low throughput; using DUV lithography is costly; and attempting to form them in a single nanoimprint lithography cycle is expensive due to the need to create molds of the desired shape. In particular, forming multiple metaatoms of different sizes with high throughput and low cost has been challenging. Therefore, there has been a need for a technology that can easily form metaatoms. Conventionally, the shape of fine semiconductor structures formed on a substrate was measured using critical dimension-scanning electron microscopy (CD-SEM). However, this method had problems such as performance damage to the semiconductor due to electron beam irradiation and the long time required for full-surface measurement. Therefore, there was a need for a non-destructive detection method to determine how these fine structures were formed.

[0005] This disclosure was made to solve the problems described above, and aims to provide a method for manufacturing a meta-optics device that can easily form meta-atoms, a method for detecting how the structure is formed, and a measuring device used in the detection method. [Means for solving the problem]

[0006] The method for manufacturing a meta-optics device according to this disclosure comprises forming a plurality of first structures by nanoimprint lithography and dividing the plurality of first structures into a plurality of second structures smaller than the plurality of first structures by nanoimprint lithography. Since the fine structures are formed by two nanoimprint lithography processes, there are two opportunities to process the material, allowing for a high degree of freedom in shaping the structures. For example, multiple structures of different sizes can be manufactured. Furthermore, since nanoimprint lithography is used, the throughput reduction that occurs when using electron beam lithography can be avoided.

[0007] The detection method according to this disclosure comprises: acquiring a first spectrum, which is a reflection, transmission, or scattering spectrum obtained by irradiating a dielectric nanostructure on a substrate with first linearly polarized visible light; and acquiring a second spectrum, which is a reflection, transmission, or scattering spectrum obtained by irradiating the dielectric nanostructure with second linearly polarized visible light having a different electric field polarization direction from the first linearly polarized visible light. Furthermore, the method comprises determining the distance between the centroids of the first resist pattern on which the dielectric nanostructure is formed and the centroid of the second resist pattern from the wavelength difference between the peak positions of the first spectrum and the peak positions of the second spectrum. According to this method, the distance between the centroids, i.e., the superposition distance, can be detected from the spectral shape that reflects the anisotropy of the dielectric nanostructure by utilizing the Mie resonance phenomenon exhibited by the dielectric nanostructure. This method enables instantaneous measurement in the field of view of an optical microscope in a non-destructive manner.

[0008] The measuring device according to this disclosure comprises a sample support unit, a light source, a linear polarizer which is a wire grid polarizer or a Gran-Taylor polarizer provided between the sample support unit and the light source, a changing device which can change the linear polarization direction in the range of 0° to 90°, and a camera. By using a wire grid polarizer or a Gran-Taylor polarizer, the extinction ratio of linearly polarized light can be increased, thereby improving the measurement accuracy of the detection method described above to, for example, 1 nm.

[0009] Other features of this disclosure are outlined below. [Effects of the Invention]

[0010] Metaatoms can be easily formed. The dimensions of the formed metaatoms and other semiconductor structures can be detected nondestructively. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an example of a method for manufacturing meta-optics devices. [Figure 2] This figure shows examples of second structures with different densities and examples of forming multiple second structures of different sizes. [Figure 3] This figure shows an example of the configuration of a measuring device for obtaining a transmission spectrum. [Figure 4] This figure shows some example configurations of the sample. [Figure 5] This figure shows examples of the first and second spectra. [Figure 6] This figure shows the correlation between the wavelength difference Δλ and the distance between centers lc. [Figure 7] This figure shows the effect of differences in overlap on the spectrum. [Figure 8] This figure shows the first and second spectra obtained for the sample in Figure 7. [Figure 9] This figure shows the effect of the diameter of dielectric nanostructures on the resonance wavelength. [Figure 10] This figure shows the effect of the formation period of dielectric nanostructures on the resonance wavelength. [Figure 11] This figure shows the effect of the height of dielectric nanostructures on the relationship between wavelength difference and center-to-center distance. [Figure 12] This figure shows the effect of the angle of incidence on the first and second spectra. [Figure 13] This is the spectrum when the dielectric nanostructure is GaAs. [Figure 14] This diagram compares the reflectance spectrum and the transmission spectrum. [Figure 15] It is a diagram showing a configuration example of a measuring device for obtaining a reflection spectrum. [Figure 16] It is a diagram showing a configuration example of a measuring device for obtaining a scattering spectrum. [Figure 17] It is a diagram showing another configuration example of a measuring device for obtaining a scattering spectrum.

Embodiments for Carrying Out the Invention

[0012] Embodiment 1. Method for Manufacturing a Meta-Optical Device This method for manufacturing a meta-optical device includes two times of nanoimprint lithography (NIL). FIG. 1 is a diagram showing an example of the method for manufacturing a meta-optical device. First, as shown in FIG. 1A, a resist 14 is applied to a dielectric layer 12 formed on a substrate 10.

[0013] A mold 16 with a concave structure pattern engraved is aligned with a predetermined position on the substrate 10. According to an example, the mold 16 and the substrate 10 can be aligned with an accuracy of atomic scale error by using the alignment method described in International Publication No. 202,214,9341. That is, a first array body and a second array body are provided on the mold 16, and a first array body with the same periodic structure as the aforementioned first array body and a second array body with the same periodic structure as the aforementioned second array body are provided on the substrate 10. The amount of misalignment is detected by fitting an optical signal by light from the array bodies, and the mold 16 and the substrate 10 are aligned based on the detected amount of misalignment. According to another example, alignment can be performed by another well-known method.

[0014] Next, the mold 16 is pressed against the resist 14 and UV light is irradiated to photo-cure the resist 14. Then, the mold 16 is peeled off from the resist 14, i.e., demolded, to obtain the resist pattern 14a shown in Figure 1B. The residual film corresponding to the recesses of the resist pattern 14a is removed, for example, by oxygen-reactive ion etching, and the dielectric layer 12 exposed from the resist pattern is etched, for example, by reactive ion etching, and the resist pattern is removed to obtain the structure shown in Figure 1C. Figure 1C shows multiple first structures 12a formed by etching the dielectric layer 12 in the first nanoimprint lithography method. The left side of Figure 1C is a cross-sectional view, and the right side is a plan view. In this example, the multiple first structures 12a are circular in plan view.

[0015] Next, the process proceeds to the second nanoimprint lithography. First, as shown in Figure 1D, a resist 20 is applied to cover multiple first structures 12a. A mold 16, which is the same as or different from the mold used in the first nanoimprint lithography, is positioned on the substrate 10 in a predetermined location using any method. The positioning is done so that a concave structure pattern, which is the same as or different from the concave structure pattern of the resist pattern 14a described above, is formed on the resist 20. In the example in Figure 1D, the same mold 16 used in the first nanoimprint lithography and the substrate 10 are positioned in a different location than the positioning in the first nanoimprint lithography. Figure 1D shows that the mold 16 is positioned slightly to the left of the mold positioned in Figure 1A.

[0016] Next, the mold 16 is pressed against the resist 20 and UV light is irradiated to photo-cure the resist 20. After that, the mold 16 is peeled off from the resist 20, and the remaining film corresponding to the recesses of the resist pattern 20a is removed, for example, by oxygen-reactive ion etching to obtain the resist pattern 20a shown in Figure 1E. The left side of Figure 1E is a cross-sectional view, and in this example, the resist pattern 20a comprises a portion that covers the substrate 10 and a portion that covers parts of the multiple first structures 12a. As shown in the left side of Figure 1E, each of the multiple first structures 12a has a portion where the dielectric is exposed and a portion that is covered by the resist pattern 20a. The right side of Figure 1E is a plan view. This plan view shows the pattern portions of the resist pattern 20a that are not recesses, and the multiple first structures 12a. In this example, the portion of the resist pattern 20a that overlaps with the multiple first structures 12a is approximately elliptical.

[0017] Next, multiple first structures 12a exposed from the resist pattern 20a are etched, for example, by reactive ion etching. Then, by removing the resist pattern 20a, a structure like that shown in Figure 1F is obtained. Figure 1F shows multiple second structures 12b formed by etching the dielectric layer 12 by two nanoimprint lithography methods. The left side of Figure 1F is a cross-sectional view, and the right side is a plan view. In this example, the multiple second structures 12b are approximately elliptical in plan view. The size of one of the multiple second structures 12b is, for example, several hundred nanometers. The approximately elliptical second structure 12b can be defined by the length in the major axis direction ly and the length in the minor axis direction lx, as shown on the right side of Figure 1F. According to one example, an approximately elliptical second structure with a difference of 5 nm or more between the lengths of the major axis and the minor axis can be formed in this way. According to another example, an anisotropic second structure 12b with a difference of 5 nm or more between the lengths of the major axis and the minor axis can be formed in this way. Anisotropic second structures are, for example, rectangles, rounded rectangles, and superellipses.

[0018] Thus, the second nanoimprint lithography method transforms the multiple first structures 12a into multiple second structures 12b that are smaller than the multiple first structures 12a. The multiple first structures are then processed using the second nanoimprint lithography method to obtain multiple second structures of the desired shape. The shapes of the multiple first structures and the multiple second structures are not particularly limited.

[0019] For example, such a plurality of second structures 12b can be provided as a meta-optics device such as a planar lens or a meta-lens. The plurality of second structures can be formed such that their densities are the same or different depending on the region of the substrate. By varying the density of the plurality of second structures depending on the region of the substrate, the refractive index changes according to the density, so they can function as a planar lens that refracts light by giving a steep phase change. Figure 2A shows an example in which the density of the second structures differs depending on the region on the substrate.

[0020] In one example, multiple second structures are the same size. In another example, the sizes of multiple second structures do not need to be uniform, and their size can be optimized depending on the type of metaoptics device. That is, multiple second structures can include multiple structures of different sizes. Figure 2B shows an example in which multiple second structures of different sizes have been formed. In general, it is practically difficult to manufacture multiple structures of different sizes using a single nanoimprint lithography method because the creation of the mold becomes costly. In contrast, when forming fine structures using two nanoimprint lithography methods, there are two opportunities to process the material, so the shape can be formed with greater freedom. Furthermore, since nanoimprint lithography is used, it is possible to avoid the reduction in throughput during production that occurs with electron beam lithography. Although two NILs have been described here, in another example, the desired shape of the structure can be obtained by three or more NILs.

[0021] 2. Measuring device Figure 3 shows an example of the configuration of a measuring device for obtaining a transmission spectrum. In one example, the light source 30 is a halogen lamp. In another example, the light source 30 can be an incoherent light source such as a mercury lamp, xenon lamp, or LED, or a coherent light source such as a CW (continuous wave) laser light source or a pulsed laser light source.

[0022] The linear polarizer 32 is provided to extract linearly polarized light from the light emitted from the light source 30. Any type of linear polarizer capable of extracting linearly polarized light can be used as the linear polarizer 32. Such linear polarizers include, for example, crystalline types using crystalline materials such as mica or quartz, and those that use polarization by elongated elliptical nanoparticles embedded in glass. In another example, the linear polarizer 32 is a wire grid polarizer or a Gran-Taylor polarizer. While a normal linear polarizer has an extinction ratio of 1000:1, a wire grid polarizer has an extinction ratio of 100,000:1 or higher, and a Gran-Taylor polarizer has an extinction ratio of 100,000:1. By using a wire grid polarizer or a Gran-Taylor polarizer, the extinction ratio of the linearly polarized light used for measurement can be increased, making it possible to measure the superposition distance in units of 1 nm from the difference in peak wavelengths, as described later.

[0023] The measuring device for obtaining the transmission spectrum in Figure 3 is equipped with a changing device 33 that can change the linear polarization direction within a range of 0° to 90°. For example, if the x-positive direction in Figure 3 is set to a linear polarization direction of 0°, then the y-positive or y-negative direction will be a linear polarization direction of 90°. The changing device 33 can be any device that can change the linear polarization within a range of 0° to 90°. In one example, the changing device 33 has a mechanism that mechanically rotates the linear polarizer 32, thereby changing the linear polarization direction within a range of 0° to 90°. In another example, a linear polarizer that obtains linear polarization by combining two circularly polarized signals in opposite directions can be used, in which case the changing device controls the polarization direction of the linearly polarized signal by controlling the phase difference between the two circularly polarized signals. In yet another example, the changing device 33 is an element that rotates the polarization direction of the linearly polarized signal by 90°. The polarization direction is controlled by switching the installation or non-installation of this element in the optical path. In yet another example, a different changing device can be used. Furthermore, the figures in this disclosure, including Figure 3, are for technical explanation purposes and may be simplified or abstracted, and may not necessarily correspond to the actual appearance and dimensions. Accordingly, the modification device 33 in Figure 3 is shown only descriptively and conceptually, and does not necessarily represent its actual appearance.

[0024] The aforementioned linear polarizer 32 is provided between the light source 30 and the sample support section 34. This measuring device has an objective lens 36 and a spectroscopic detector 38. Light transmitted through the sample in the sample support section 34 passes through the objective lens 36 and reaches the spectroscopic detector 38. The spectroscopic detector 38 includes, for example, a spectroscopic element that separates incident light into wavelengths, and a camera that detects the light dispersed by the spectroscopic element. The spectroscopic element is, for example, a prism, a diffraction grating, or an optical filter. The camera is, for example, a CCD camera or a CMOS camera. In another example, the camera is a hyperspectral camera. A hyperspectral camera is, for example, a camera that can measure the spatial distribution of a spectrum by performing spectroscopy while retaining spatial information and acquiring spectral information for each pixel of an image. A hyperspectral camera typically includes a diffraction grating and a two-dimensional detector that detects wavelength information and spatial information. In one example, a hyperspectral camera may have a display section, either in part or externally, that displays the distribution of colors corresponding to the position of the sample.

[0025] 3. Detection Method This detection method, for example, uses the aforementioned measuring device to utilize the behavior of dielectric nanostructures as Mie resonators, measuring their optical anisotropy using a linearly polarized visible light spectrum, and detecting the distance between centroids, or superposition distance, from the spectral shape that reflects the anisotropy of the dielectric nanostructures. Figure 4 shows an example of a partial configuration of the sample. Figure 4A is a plan view of the dielectric nanostructure 40. In this example, the dielectric nanostructure 40 is approximately elliptical in plan view, with a minor axis length of lx and a major axis length of ly. Figure 4B is a partial front view of the sample. The sample comprises a substrate 42 and dielectric nanostructures 40 formed on the substrate 42. Multiple such dielectric nanostructures 40 are periodically formed on the substrate 42. Figure 4C shows that the electric field polarization direction at 0° is parallel to the x-axis, and the electric field polarization direction at 90° is parallel to the y-axis.

[0026] In this detection method, a dielectric nanostructure 40 on a substrate is irradiated with first linearly polarized visible light. The electric field polarization direction of the first linearly polarized visible light is, for example, 0° or 90°. The transmission spectrum obtained by irradiating the sample with the first linearly polarized visible light is called the first spectrum. For example, the first spectrum is acquired by a spectroscopic detector 38. The second spectrum is acquired before or after the acquisition of the first spectrum. The second spectrum is a transmission spectrum obtained by irradiating a dielectric nanostructure with second linearly polarized visible light having a different electric field polarization direction from the first linearly polarized visible light. For example, the electric field polarization direction of the second linearly polarized visible light is 90° when the electric field polarization direction of the first linearly polarized visible light is 0°, and 0° when the electric field polarization direction of the first linearly polarized visible light is 90°. The electric field polarization direction can be adjusted by the adjustment device 33. The transmission spectrum obtained by irradiating the sample with second linearly polarized visible light is called the second spectrum. For example, the second spectrum is acquired by the spectroscopic detector 38. Note that the first and second spectra are not limited to transmission spectra transmitted through the sample, but may also be reflection spectra or scattering spectra.

[0027] Figure 5 shows an example of the simulation results for the first and second spectra. The simulation was performed under the following conditions: Electromagnetic field calculations were performed using the finite-difference time-domain method (FDTD) with Ansys Lumerical FDTD software. In this embodiment, the mesh size representing the minimum Yee lattice unit in the simulation was a cube with x=5nm, y=5nm, and z=5nm, and a plane wave was incident. For each unit structure, the boundary conditions in the x and y directions were periodic repeating conditions, and the boundary condition in the z direction was a perfectly matched layer condition. The refractive indices of Si, Ge, and GaAs at a wavelength of 633nm were 3.9, 5.5, and 3.8, respectively. In this example, for a silicon dielectric nanostructure exhibiting anisotropy with a minor axis lx in the 0° direction and a major axis ly in the 90° direction, the first spectrum was obtained using first linearly polarized visible light with an electric field polarization direction of 0°, and the second spectrum was obtained using second linearly polarized visible light with an electric field polarization direction of 90°. The first and second spectra reflect the Mie resonance phenomenon caused by the dielectric nanostructure. Mie resonance is a resonance phenomenon of light caused by particles of wavelength size, and is particularly observed in high refractive index dielectrics. The resonance wavelength changes depending on the size and shape of the particles, i.e., the dielectric nanostructure. There are electrical resonances that respond to the incident electric field and magnetic resonances that respond to the incident magnetic field. The second spectrum in Figure 5 has two peaks; the long-wavelength peak is attributed to magnetic dipole resonance, and the short-wavelength peak is attributed to electric dipole resonance. The peak originating from magnetic dipole resonance was obtained with sufficient intensity in both the first and second spectra. In other words, a peak of sufficient intensity can be obtained with both the first linearly polarized visible light having an electric field polarization direction parallel to the short axis of the dielectric nanostructure and the second linearly polarized visible light having an electric field polarization direction parallel to the long axis of the dielectric nanostructure. On the other hand, the short-wavelength peak originating from the resonance of the electric dipole was of sufficient intensity in the second spectrum, but weak in the first spectrum. It was found that the peak intensity of the electric dipole significantly decreases and the signal-to-noise ratio decreases as the disk diameter in the electric field polarization direction (i.e., the length of the dielectric nanostructure) decreases. Therefore, for example, by focusing on the long-wavelength peak originating from the magnetic dipole rather than the short-wavelength peak originating from the resonance of the electric dipole, it is possible to detect the peak difference between the first and second spectra. In the example in Figure 5, the peak position of the first spectrum is λ1, the peak position of the second spectrum is λ2, and the wavelength difference between them is Δλ. For example, the peak at the peak position of the first spectrum is reflection, transmission, or scattering based on magnetic dipole resonance. The inventors found a correlation between this wavelength difference Δλ and the dimensions of the dielectric nanostructure. A circular resist mask, which is easy to explain, is illustrated in Figure 7 as an example. More directly, they found a correlation between the wavelength difference Δλ and the center-to-center distance (this is an example of the centroid-to-centroid distance) lc. The center-to-center distance lc is the distance between the center position of the first circular resist mask and the center position of the second circular resist mask. A large center-to-center distance lc means that there is little overlap between the two etching patterns, resulting in the formation of a dielectric nanostructure (e.g., second structure 12b) with a short axis length. Conversely, a small center-to-center distance lc means that there is a large overlap between the two etching patterns, resulting in the formation of a dielectric nanostructure (e.g., second structure 12b) with a long axis length. If the distance between centers lc is 0, the two etching patterns will overlap without any misalignment. Therefore, the distance between centers lc can be said to be the overlapping distance of the two etching patterns. Figure 6 shows the correlation between the wavelength difference Δλ and the center-to-center distance lc. In Figure 6, multiple points represent data obtained from simulations, and the line segments are obtained by fitting them together. The linear region is the region where Δλ and lc have a roughly positive linear relationship, and in the example of Figure 6, this corresponds to the range of Δλ from 0 nm to 55 nm. In this region where the fitting line is linear, lc can be estimated with high accuracy from Δλ. If the estimated center-to-center distance lc is the same as the design value, it can be seen that the two etching patterns were formed accurately. On the other hand, if the estimated center-to-center distance lc differs from the design value, it can be seen that the two etching patterns deviated from the design value by that difference. Furthermore, the length of the dielectric nanostructure can be determined from the estimated center-to-center distance lc. Thus, using this detection method, the center-to-center distance lc of the dielectric nanostructure can be determined from the wavelength difference Δλ between the peak positions of the first spectrum and the peak positions of the second spectrum.

[0028] Incidentally, in the semiconductor microfabrication process using nanoimprint lithography (NIL), a mold is aligned to a predetermined position on the substrate to form a resist mask, and semiconductor microfabrication is achieved through an etching process. In this process, the substrate and the mold need to be aligned with, for example, an accuracy of one order of nanometers. The substrate and the mold must be aligned, imprinted, a resist pattern formed, and then etched to form a dielectric nanostructure of the desired shape. When two NIL processes are performed, the above detection method can be used to determine the centroidal distance (center distance) lc from the wavelength difference Δλ between the centroidal position (center position) of the mold pattern from the first NIL and the centroidal position (center position) of the mold pattern from the second NIL. This centroidal distance (center distance) lc reflects the overlapping distance of the two mold patterns.

[0029] For example, consider the case where a dielectric nanostructure with a roughly elliptical shape, as shown in Figure 1F, is manufactured using the manufacturing method for metaoptics devices described with reference to Figure 1. The upper part of Figure 7 shows the mold pattern positions of two nanoimprint lithography processes. Figure 7A shows the mold pattern 50 and its center position for the first NIL (NIL1), and the mold pattern 52 and its center position for the second NIL (NIL2). NIL1 forms a planar dielectric nanostructure as shown by mold pattern 50. Then, NIL2 leaves the portion of this dielectric nanostructure that overlaps with mold pattern 52. As a result, a dielectric nanostructure with a roughly elliptical shape, as shown in Figure 7D, is formed. In Figure 7A, the circumference of mold pattern 50 and the center of mold pattern 52 overlap, and the circumference of mold pattern 52 and the center of mold pattern 50 overlap. This state is said to have an overlap degree of 0.5. Since each mold pattern overlaps by half in the x direction, the overlap degree is 0.5. The degree of overlap is calculated using the following formula, where lc is the distance between centers and R is the diameter of the circle. Overlap degree = (R - lc) / R Therefore, the larger the distance between centers lc, the smaller the degree of overlap. Figure 7B shows the mold patterns 50 of NIL1 and 52 of NIL2 when the overlap degree is 0.75. When the overlap degree is 0.75, the overlap area of ​​the two mold patterns is larger than when the overlap degree is 0.5 as described above. Figure 7E shows the planar shape of the dielectric nanostructure manufactured by the mold patterns 50 and 52 in Figure 7B. Figure 7C shows the mold pattern 50 of NIL1 and the mold pattern 52 of NIL2 when the overlap degree is 1. In this case, the two mold patterns 50 and 52 completely overlap. When the overlap degree is 1, the shape of the dielectric nanostructure obtained from NIL1 is maintained after NIL2. Figure 7F shows that the planar shape of the dielectric nanostructure produced by the mold patterns 50 and 52 in Figure 7C is circular.

[0030] Figure 8 shows the first and second spectra obtained for the three samples in Figure 7. Three simulations were performed with varying periods and diameters for overlap degrees of 0.5, 0.75, and 1. The first simulation was performed with a period of 450 nm by forming multiple dielectric nanostructures at 450 nm intervals, a mold pattern diameter of 210 nm, and a dielectric nanostructure height of 180 nm. The second simulation was performed by forming multiple dielectric nanostructures at 500 nm intervals, resulting in a period of 500 nm, with a mold pattern diameter of 250 nm and a dielectric nanostructure height of 180 nm. The third simulation was performed by forming multiple dielectric nanostructures at 600 nm intervals, resulting in a period of 600 nm, with a mold pattern diameter of 300 nm and a dielectric nanostructure height of 180 nm. In all simulations unless otherwise specified, dielectric nanostructures were assumed to be silicon nanodisks (Si-NDs).

[0031] When the overlap degree was 0.5, the peaks of the first and second spectra were detected with sufficient intensity in the two samples on the left and in the center, but the peak in the sample on the right was somewhat weaker. When the electric field polarization direction was 0°, in which the peak originating from the short axis direction was detected, a decrease in peak intensity was observed compared to when it was 90°.

[0032] At an overlap of 0.75, spectral peaks were detected with sufficient intensity in all samples on the left, center, and right. The wavelength difference Δλ of the peak positions obtained at an overlap of 0.75 was smaller than the wavelength difference Δλ obtained at an overlap of 0.5. Also, in both cases of overlap 0.5 and 0.75, the peak position shifts to shorter wavelengths in the short-axis polarization direction (0°) compared to the long-axis polarization direction (90°). Figure 8 also shows the spectrum when the electric field polarization direction is 45°. The peak position at 45° is between the peak position at 0° and the peak position at 90°. In this example, to increase Δλ, the wavelength difference Δλ between the peak position at 0° and the peak position at 90° is used. That is, the electric field polarization direction of the first linearly polarized visible light and the electric field polarization direction of the second linearly polarized visible light differ by 90°. In another example, the first and second spectra may be obtained from linearly polarized visible light having any two electric field polarization directions between 0° and 90°.

[0033] When the overlap degree is 1, the dielectric nanostructure has an isotropic shape rather than an anisotropic shape, so the same spectrum can be obtained even if the direction of electric field polarization of linearly polarized visible light is changed. It was found that the smaller the overlap degree, the larger the wavelength difference Δλ, and the larger the overlap degree, the smaller Δλ becomes. From the Δλ value obtained in this way, the inter-center distance lc can be determined based on the relationship between Δλ and the inter-center distance lc as shown in Figure 6. The greater the degree of overlap, the smaller Δλ and the smaller the inter-center distance lc. In the linear region of Figure 6, for every 1 nm variation in the wavelength difference Δλ, the inter-center distance lc changes by approximately 1.5 nm. Therefore, the inter-center distance lc, which is the shift in the processing position, can be determined with approximately 1.5 times the sensitivity of the difference in spectral peaks.

[0034] Here, (alignment setting value) - (overlap distance) is the error (amount of deviation), and this error is called "overlap accuracy." For example, if we hypothetically consider an overlap of 0.75 as the setting value (design value), and the center-to-center distance lc corresponding to an overlap of 0.5 is calculated, or the center-to-center distance lc corresponding to an overlap of 1 is calculated, then the alignment setting value - overlap distance (center-to-center distance), i.e., the error, is large, so it can be determined that the overlap accuracy of the two mold patterns is low. On the other hand, if the center-to-center distance lc corresponding to an overlap of 0.75 or a center-to-center distance close to it is calculated, it can be determined that the overlap accuracy of the two mold patterns is high. By determining the center-to-center distance lc in this way, it is possible to ensure that the superposition accuracy is within a certain range. Furthermore, the superposition distance of the semiconductor pattern fabricated as a result of the alignment of the substrate and mold can be estimated with an accuracy of one order of magnitude nanometers. Moreover, this method does not cause damage to the sample. In addition, the first and second spectra within the desired range can be acquired with high throughput using an optical microscope. On the other hand, when electron beam irradiation is performed with a CD-SEM, damage to the sample is unavoidable, and in that sense, this method is superior. Furthermore, if the same mold is used for both the first and second NIL (Natural Integrity Line) runs, a wavelength difference Δλ can be obtained that reflects only the overlap distance. On the other hand, if different molds are used for the first and second NIL runs, a wavelength difference Δλ will be obtained that reflects both the dimensional difference between the molds and the overlap distance, which may reduce the accuracy of the center-to-center distance lc compared to using the same mold. However, if the dimensional difference between the molds is small, this does not pose a practical problem.

[0035] In this example, dielectric nanostructures were formed using two NIL (Natural Integration Linear) processes with the same mold. In another example, dielectric nanostructures can be formed by an exposure process using a photomask or reticle. In this case, the distance between the centers of two mask patterns, not the distance between the centers of two mold patterns, can be estimated from the wavelength difference Δλ. This detection method is broadly applicable when forming dielectric nanostructures by repeating a series of processes, including any patterning and etching method, twice. Forming dielectric nanostructures that function as process monitors at regular intervals across the entire wafer surface enables observation of the in-plane distribution of superposition distances. Using a high-magnification optical microscope, the distribution of linearly polarized visible light spectra in a narrow region can be observed, while using a low-magnification optical microscope allows observation of linearly polarized visible light spectra in a wide region. The distribution of colors within the field of view can be investigated using a hyperspectral camera. If the first and second spectra are transmission spectra, the substrate 10 material should be transparent, such as synthetic quartz. However, if a reflectance spectrum or scattering spectrum is to be obtained, any substrate can be used.

[0036] 4. Investigation of the shape and period of dielectric nanostructures We will examine the diameter of the dielectric nanostructure. Figure 9A is a partial plan view of the sample. Figure 9A illustrates a structure in which a substrate 42 and a circular dielectric nanostructure 60 are formed on it. For a sample in which this structure is repeated with period p, the diameter of the dielectric nanostructure is p / 2, and the height of the dielectric nanostructure is 180 nm, we investigated by simulation how changes in the value of p affect the Mie resonance wavelength. Figure 9B shows the results of such investigation, and is a simulation result showing the relationship between the diameter of the dielectric nanostructure Si-ND and the resonance wavelength. From Figure 9B, it can be seen that as the diameter of the dielectric nanostructure increases, the resonance wavelength shifts to the longer wavelength side, and the resonance wavelength is in the visible to infrared region. According to this simulation, in order to position the spectral peak in the wavelength range of visible light, which is from 360 nm to 830 nm, the value of p should be set to 300 nm to 600 nm or from 400 nm to 500 nm. In other words, the diameter of the dielectric nanostructure can be set to 150 nm to 300 nm, or to 200 nm to 250 nm.

[0037] This study examines the installation period of dielectric nanostructures. Figure 10A is a partial plan view of a sample. Figure 10A illustrates a structure in which a substrate 42 and a circular dielectric nanostructure 60 are formed on it. For a sample in which this structure is repeated with period p, the diameter of the dielectric nanostructure is R, and the height of the dielectric nanostructure is 180 nm, simulations were used to investigate how changes in the values ​​of period p and diameter R affect the Mie resonance wavelength. Figure 10B shows the results of such investigations, illustrating the simulation results showing the relationship between the diameter of the Si-ND dielectric nanostructure and the resonance wavelength. From this simulation, it was found that the resonance wavelength strongly depends on the diameter R of the Si-ND. Furthermore, it was found that the resonance band shape and resonance intensity strongly depend on the period p. According to the inventors' simulations, by forming multiple dielectric nanostructures with periods between 300 nm and 500 nm, it was possible to position the spectral peak in the visible light wavelength range of 360 nm to 830 nm.

[0038] This section examines the height of dielectric nanostructures. Figure 11A shows the sample shape. The upper part of Figure 11A is a front view, and the lower part is a top view. The height of the dielectric nanostructure 60 formed on the substrate 42 is h, and its diameter is R. Multiple such structures are formed with a period p. For this sample, the effect of the height h on the relationship between the wavelength difference Δλ and the intercenter distance lc was investigated by simulation. Figure 11B shows the results of such investigation, where the relationship between Δλ and lc was calculated for the cases p=450nm and R=210nm, and p=600nm and R=300nm. First, in the case of the relatively small structure size on the left side of Figure 11B, it was found that changing the height h of the dielectric nanostructure changes the ratio of the change in Δλ to the change in lc, i.e., the sensitivity. More specifically, increasing the height h of the Si-ND reduces the change in intercenter distance relative to the change in peak difference compared to the case where the height h is small. Therefore, increasing the height h makes it possible to observe minute changes in the intercenter distance. Furthermore, when the height h was small, the linear region in which the peak difference and the intercenter distance had a linear relationship tended to narrow. The right side of Figure 11B shows the simulation results when the Si-ND was relatively large. From these results, it was found that for large Si-NDs, the height h does not contribute much to the sensitivity. According to the inventors' research, for relatively small Si-NDs, it was found that setting the height h of the dielectric nanostructure to between 120 nm and 240 nm made it easier to adjust the ratio of the change in Δλ to the change in lc, i.e., the sensitivity, to the desired value. For example, in a sample in which multiple dielectric nanostructures with a diameter of 210 nm and a height of 180 nm were formed with a period of 450 nm, the spectral peak falls in the visible light region in the detection method described above, making it easy to measure Δλ.

[0039] 5. Examination of the incident angle of linearly polarized visible light The effect of the incident angle when linearly polarized visible light is incident on a sample on the first and second spectra was investigated. Figure 12A shows the sample and the linearly polarized visible light incident on the sample. The direction of propagation of the linearly polarized visible light is represented by k, and its electric field polarization direction is represented by E. The angle between the direction of propagation of the linearly polarized visible light and the dashed line, which is a virtual line perpendicular to the substrate 42, is θ. This angle θ is called the incident angle. A sample was investigated in which multiple Si-ND dielectric nanostructures were formed with a period of 450 nm, with a diameter of 210 nm and a height of 180 nm. Figure 12B shows the simulation results of spectra obtained when the incident angle θ was 0°, 15°, 30°, and 45°. In the range of incident angle θ from 0° to 45°, the peak intensity changed according to the incident angle θ, but the peak position did not change even when the incident angle θ changed. Therefore, the above detection method can be implemented using a well-known focusing lens optical system that does not precisely control the incident angle θ. Furthermore, in order to detect a peak position with sufficient intensity within the wavelength range of visible light, which is between 360 nm and 830 nm, the incident angle can be in the range of 0° to 30°. For example, the angle between the direction of propagation of the first linearly polarized visible light and a virtual line perpendicular to the substrate can be set to between 0° and 30°, and the angle between the direction of propagation of the second linearly polarized visible light and a virtual line perpendicular to the substrate can be set to between 0° and 30°.

[0040] 6. Examination of materials for dielectric nanostructures GaAs was investigated as a material for dielectric nanostructures. Simulations were performed to obtain the first and second spectra of a sample consisting of multiple dielectric nanostructures made of GaAs, with a diameter of 210 nm and a height of 180 nm, arranged at a period of 450 nm. Figure 13 shows the simulation results. The transmission spectrum is shown on the right side of Figure 13. From this figure, it can be seen that the wavelength difference Δλ between the peak positions of the first and second spectra can be detected when GaAs is used as a dielectric nanostructure. The reflection spectrum is shown on the left side of Figure 13. Although the intensity of the peak positions in the reflection spectrum is smaller than that of the transmission spectrum, it was found that Δλ can be detected. Figure 14 shows the relationship between the wavelength difference Δλ of the peaks of this GaAs sample and the intercenter distance lc. Data obtained from the transmission spectrum are connected by dashed lines. Data obtained from the reflection spectrum are not connected by dashed lines. From these results, it can be seen that the intercenter distance lc can be calculated using a Δλ of approximately 0 nm to 50 nm with the transmission spectrum, and the intercenter distance lc can be calculated using a Δλ of approximately 0 nm to 20 nm with the reflection spectrum. Furthermore, simulations were also performed when the dielectric nanostructure material was Ge. Similar to the case of GaAs mentioned above, it was found that although the intensity of the peak position in the reflection spectrum was smaller than that of the transmission spectrum, Δλ could be detected in both cases. Incidentally, the higher the refractive index of a dielectric nanostructure, the higher its optical confinement ability. For example, if the refractive index at a wavelength of 633 nm is lower than 2, sufficient optical confinement cannot be obtained, and dielectrics with a refractive index higher than 6 are rare and difficult to process. For example, materials with a refractive index in the range of 2.0 to 6.0 at a wavelength of 633 nm can be used as dielectric nanostructures. The refractive index at 633 nm of the dielectric nanostructures exemplified so far is around 4 to 5.5. In addition, TiO2 can be used as a Mie resonator, and the refractive index of TiO2 at a wavelength of 633 nm is around 2.5.

[0041] 7. Example of a measuring instrument configuration As mentioned above, the first and second spectra can be reflection, transmission, or scattering spectra. An example of a measuring device for obtaining a transmission spectrum is shown in Figure 3. Figure 15 shows an example of the configuration of a measuring device for obtaining a reflection spectrum. Light emitted from the light source 30 is converted into linearly polarized light by the linear polarizer 32, reflected by the half mirror 70, passes through the objective lens 36, and irradiates the sample supported by the sample support section 34. The reflected light reflected from the sample is detected by the spectroscopic detector 38.

[0042] Figure 16 shows an example configuration of a measuring device for obtaining a scattering spectrum. Linearly polarized visible light incident on the sample is scattered by the sample, and the scattered light is detected by the spectroscopic detector 38. Figure 17 shows another example configuration of a measuring device for obtaining a scattering spectrum. Linearly polarized visible light is split into multiple optical paths by the ring aperture 72 and then irradiated onto the sample to obtain scattered light. The scattered light is detected by the spectroscopic detector 38. In the configuration example of Figure 17, a dark-field objective lens can be used as the objective lens 36. In the measuring device shown in Figure 15-17, the linear polarizer 32 and the polarizer changer 33 can be placed at any position between the light source and the sample. The computer 39 shown in Figure 3 is also implemented in the measuring device shown in Figure 15-17.

[0043] 8. Application of detection methods to the manufacturing method of meta-optics devices The method for determining the intercenter distance using the detection method described above can be incorporated into the manufacturing process of metaoptics devices. That is, when manufacturing nanostructures that reflect the desired degree of overlap using multiple NIL (Natural Integrity Line) processes, estimating the intercenter distance using the detection method described above can ensure that dielectric nanostructures with the intended shape have been formed.

[0044] 9. Mold patterns, etching patterns, semiconductor patterns, mask patterns These names share the common meaning of being patterns for etching the dielectric layer. The first etching is performed using the first mold pattern, first etching pattern, first semiconductor pattern, or first mask pattern (collectively referred to as the first pattern), and the second etching is performed using the second mold pattern, second etching pattern, second semiconductor pattern, or second mask pattern (collectively referred to as the second pattern). In the example above, the first and second patterns were circular, but other shapes can be used. For example, the first and second patterns can be elliptical, polygonal, or rounded polygonal. If the first and second patterns are any shape, including circles, then "center" may be replaced with "centroid," and in that case, the distance between centers lc may be replaced with the distance between centroids lc. In one example, the centroid refers to the geometric centroid. The distance between centroids lc corresponding to the wavelength difference Δλ can be determined based on the relationship between the wavelength difference Δλ and the distance between centroids lc, just as in the case of determining the distance between centers. [Explanation of Symbols]

[0045] 10 Substrate, 12 Dielectric layer, 12a Multiple first structures, 12b Multiple second structures, 14,20 Resist, 14a,20a Resist pattern, 16 Mold, 30 Light source, 32 Linear polarizer, 33 Modification device, 34 Sample support, 36 Objective lens, 38 Spectroscopy detector

Claims

1. Forming multiple first structures using nanoimprint lithography, A method for manufacturing a metaoptics device, comprising: using nanoimprint lithography to form a plurality of second structures smaller than the plurality of first structures from the plurality of first structures.

2. The plurality of second structures are formed on a substrate, A method for manufacturing a metaoptics device according to claim 1, wherein the densities of the plurality of second structures are the same or different depending on the region of the substrate.

3. The method for manufacturing a metaoptics device according to claim 1, wherein the plurality of second structures include a plurality of structures of the same or different sizes.

4. A method for manufacturing a metaoptics device according to any one of claims 1 to 3, wherein the plurality of second structures include structures having an anisotropic shape in which the difference between the length of the major axis and the length of the minor axis in a plan view is 5 nm or more.

5. The method for manufacturing a metaoptics device according to any one of claims 1 to 3, wherein the metaoptics device is a planar lens or a metalens.

6. Obtaining a first spectrum, which is the reflection, transmission, or scattering spectrum obtained by irradiating a dielectric nanostructure on a substrate with first linearly polarized visible light, To obtain a second spectrum, which is a reflection, transmission, or scattering spectrum, obtained by irradiating the dielectric nanostructure with a second linearly polarized visible light having a different electric field polarization direction from the first linearly polarized visible light, A detection method comprising determining the distance between the centroids of the centroid of the first resist pattern on which the dielectric nanostructure is formed and the centroid of the second resist pattern from the wavelength difference between the peak position of the first spectrum and the peak position of the second spectrum.

7. The detection method according to claim 6, characterized in that the peak at the peak position of the first spectrum is reflection, transmission, or scattering based on magnetic dipole resonance.

8. The detection method according to claim 6 or 7, further comprising forming the dielectric nanostructure by two nanoimprint lithography procedures using the same mold.

9. The detection method according to claim 6 or 7, wherein the electric field polarization direction of the first linearly polarized visible light and the electric field polarization direction of the second linearly polarized visible light are 90° different.

10. The dielectric nanostructure has a diameter of 150 nm or more and 300 nm or less. Multiple dielectric nanostructures are formed with a period of 300 nm to 500 nm. The detection method according to claim 6 or 7, wherein the dielectric nanostructure is circular or elliptical in plan view.

11. The detection method according to claim 6 or 7, wherein the height of the dielectric nanostructure is 120 nm or more and 240 nm or less.

12. The angle between the direction of propagation of the first linearly polarized visible light and the imaginary line perpendicular to the substrate is 0° or more and 30° or less. The detection method according to claim 6 or 7, wherein the angle between the direction of propagation of the second linearly polarized visible light and a virtual line perpendicular to the substrate is 0° or more and 30° or less.

13. The detection method according to claim 6 or 7, wherein the dielectric nanostructure has a refractive index in the range of 2.0 to 6.0 at a wavelength of 633 nm.

14. Sample support section, Light source and A linear polarizer, which is a wire grid polarizer or a Grand-Taylor polarizer, is provided between the sample support and the light source. A device that can change the linear polarization direction within a range of 0° to 90°, A measuring device equipped with a camera.

15. The aforementioned camera is a hyperspectral camera, The measuring device according to claim 14, further comprising a display unit that displays a color distribution corresponding to the position of a sample supported by the sample support unit.

Images