Superlens and preparation method thereof, camera module and electric equipment

Abstract

The embodiment of the invention provides a super lens and a preparation method thereof, a camera module and electric equipment. The intervals between the micro-nano structures on the surface of the super lens are narrow, the smoothness of the surfaces of the micro-nano structures is high, and the super lens has a certain depth-to-width ratio. Based on the special surface design of the super lens, the super lens has high numerical aperture and focusing efficiency on the basis of excellent elimination of the chromatic aberration of visible light, so that it is possible that the super lens replaces a traditional lens composition used for eliminating the chromatic aberration in an optical device.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of lenses, and in particular, to a metasurface lens and a preparation method thereof, a camera module, and an electrical device. Background Art

[0002] With the development of terminal devices, consumers have higher and higher requirements for terminal devices (such as mobile phones). Among them, a powerful camera function is also an important factor attracting consumers. In related technologies, multiple groups of lenses are often built into the camera module of a terminal device to eliminate chromatic aberration generated when white light is focused, which results in an excessive thickness of the camera module and has a certain impact on the thinness and aesthetics of the terminal device. A metasurface lens is an optical device that uses artificial sub-wavelength unit structures to perform wavefront modulation on a traditional medium. It can precisely control the phase by using the nanostructures on the surface, enabling light of different working wavelengths to be focused at the same point, achieving lens focusing and eliminating chromatic aberration caused by light of different working wavelengths. It is expected to replace the traditional lens group in optical devices, and the thickness of the metasurface lens is only one ten-thousandth of the thickness of a traditional lens, making the miniaturization and integration of optical devices gradually possible.

[0003] Although the current metasurface lenses can better eliminate the imaging chromatic aberration of white light, their numerical aperture is not high and the focusing efficiency is low, so their applications are still limited. Summary of the Invention

[0004] The embodiments of the present application provide a metasurface lens and a preparation method thereof, a camera module, and an electrical device. In each nanocolumn array of the metasurface lens, a plurality of nanocolumns with a relatively high aspect ratio are arranged in an array, and the spacing between adjacent nanocolumns is narrow, and the surface smoothness of each nanocolumn is high, which can simultaneously improve the focusing efficiency and numerical aperture of the metasurface lens.

[0005] In a first aspect of the embodiments of the present application, a metasurface lens is provided, including a substrate and a plurality of nanocolumn arrays disposed on one side surface of the substrate. Each nanocolumn array includes a plurality of nanocolumns arranged in an array; the spacing between two adjacent nanocolumns is 20 nm - 240 nm; the aspect ratio of the nanocolumn is ≥ 3.57; the roughness of the planar edge of the nanocolumn is ≤ 2 nm.

[0006] In the above-mentioned metalens, each nanorod in the nanorod array has a slender and tall structure, and the spacing between two adjacent nanorods is relatively narrow, which can make the arrangement density of the slender and tall microstructures with sub-wavelength size for phase adjustment on the surface of the metalens relatively large and the duty cycle high. As a result, the phase compensation of the metalens can be significantly improved and finely regulated, so that chromatic aberration generated by light in a continuous broadband can be preferably eliminated while the focusing efficiency and numerical aperture of the metalens are improved. Further, by controlling the roughness of the planar edge of the nanorod within the range of ≤2 nm, the light loss can be further reduced, and the focusing efficiency of the metalens can be further improved.

[0007] In some embodiments of the present application, the spacing between two adjacent nanorods is 20 nm - 39 nm. In this way, the arrangement density of the nanorods on the surface of the metalens can be ensured to be relatively large, so that the focusing efficiency and numerical aperture of the metalens can be further improved.

[0008] In some embodiments of the present application, the aspect ratio of the nanorod is 3.57 - 16.7. By controlling the aspect ratio of the nanorod within the above range, while ensuring a wide phase regulation range, high focusing efficiency and large numerical aperture of the metalens, the metalens can be more easily fabricated.

[0009] In some embodiments of the present application, the height of the nanorod is 600 nm - 1000 nm. By controlling the height of the nanorod within the above range, a relatively wide phase adjustment range and stronger phase adjustment ability of the metalens can be ensured, and it has good visible light achromatic aberration performance, and is beneficial to further improving its focusing efficiency and numerical aperture.

[0010] In some embodiments of the present application, the width of the nanorod is 60 nm - 280 nm. By controlling the width of the nanorod within the above range, the cross-sectional area of the nanorod can be controlled within a suitable range, and the density of the nanorods per unit area of the metalens can be ensured to be relatively large, thereby ensuring strong phase regulation performance of the metalens.

[0011] In some embodiments of the present application, the roughness of the planar edge of the nanorod is 1 nm - 2 nm. In this way, while fully reducing the visible light loss, the fabrication difficulty of the metalens can be reduced, and the cost performance of the metalens can be improved.

[0012] In some embodiments of the present application, the included angle between the side wall of the nanorod and the substrate is 85° - 90°. In this way, the phase adjustment effect of the nanorod can be fully exerted, and the formation of trapezoidal nanorods can be avoided, thereby avoiding the phenomenon that the spacing between the bottoms of adjacent nanorods is too small, and reducing the risk that the poor separation at the bottom of the nanorod affects the phase adjustment ability.

[0013] In some embodiments of the present application, any 10 μm of the metalens 2In terms of area, there are at least 70 of the nanocolumns. In this way, the arrangement density of the nanocolumns in the nanocolumn array is relatively large, which can further broaden the phase modulation of the metalens and optimize the achromatic effect.

[0014] In some embodiments of the present application, the material of the nanocolumns is selected from silicon nitride or gallium nitride. The refractive index and light transmittance of the above materials are relatively high, which is beneficial to the performance of the metalens.

[0015] In some embodiments of the present application, the heights of the nanocolumns in a single nanocolumn array are equal.

[0016] In some embodiments of the present application, the heights of the nanocolumns in multiple nanocolumn arrays are equal. In some other specific embodiments, the heights of the nanocolumns in a single nanocolumn array are equal, while the heights of the nanocolumns in multiple nanocolumn arrays are not equal.

[0017] In some embodiments of the present application, the aperture of the metalens ≥ 1 mm. In this way, the light-receiving area of the metalens is large. When it is applied to a camera, the thickness of the camera lens module can be significantly reduced while the wide-angle angle of the camera is increased.

[0018] In some embodiments of the present application, the average light transmittance of the metalens in the visible light band ≥ 60%. In this way, a relatively high focusing efficiency of the metalens can be ensured.

[0019] In some embodiments of the present application, the numerical aperture of the metalens ≥ 0.5.

[0020] In some embodiments of the present application, the focusing efficiency of the metalens ≥ 60%.

[0021] In a second aspect of the embodiments of the present application, a method for manufacturing a metalens is provided, including:

[0022] Providing a substrate and a material layer disposed on one surface of the substrate, and forming a first hard mask on the surface of the material layer facing away from the substrate; the etching selectivity between the material layer and the first hard mask ≥ 30:1;

[0023] Disposing a photoresist layer on the surface of the first hard mask facing away from the material layer, the photoresist layer including a plurality of photoresist columns disposed at intervals, the first hard mask between adjacent two of the photoresist columns being exposed, and the width of the photoresist columns being 20 nm - 240 nm, to obtain a first preform;

[0024] Forming a second hard mask on the surface of the first preform having the photoresist layer to obtain a second preform; the etching selectivity between the second hard mask and the first hard mask < 1;

[0025] Remove the photoresist layer, and etch the area of the first hard mask that is not covered by the second hard mask to obtain a third preform;

[0026] Etch the third preform so that the material layer is transformed into a plurality of nano-column arrays, each nano-column array including a plurality of nano-columns arranged in an array, to obtain a superlens; wherein, the aspect ratio of the nano-columns ≥ 3.57, and the planar edge roughness of the nano-columns ≤ 2 nm.

[0027] The above preparation method has strong operability and strong process reliability. Those skilled in the art can quickly master its preparation process, with high production efficiency and is suitable for large-scale industrial production.

[0028] In some embodiments of the present application, the material of the first hard mask includes metal chromium, metal silver or metal aluminum. The above materials have strong etching resistance.

[0029] In some embodiments of the present application, the material of the second hard mask is silicon dioxide. In the etching system provided by the embodiments of the present application, silicon dioxide is a mask suitable for materials such as chromium, silver or aluminum, and its use as the material of the second hard mask can improve the accuracy of pattern transfer.

[0030] In some embodiments of the present application, the thickness of the first hard mask is 20 nm - 50 nm; the thickness of the second hard mask is 10 nm - 40 nm. In this way, when etching the material layer, the safety and uniformity of the material layer etching can be improved.

[0031] In some embodiments of the present application, etching the area of the first hard mask that is not covered by the second hard mask includes: placing the second preform after removing the photoresist layer in a plasma etching device, introducing chlorine gas, and the flow rate of the chlorine gas is 20 sccm - 40 sccm; adjusting the plasma power to 1000 W - 1400 W, the bias power to 0 - 50 W, and the gas pressure to 0 - 20 mTorr. Controlling the etching conditions within the above range can achieve chemical etching and physical bombardment of the first hard mask, and smoothly and cleanly remove the first hard mask on the area not covered by the second hard mask.

[0032] In some embodiments of the present application, it further includes introducing oxygen gas into the plasma etching device, and the oxygen gas flow rate ≤ 10 sccm. In this way, the chemical etching environment in the system can be optimized.

[0033] In some embodiments of the present application, the etching of the third preform includes: placing the third preform in a plasma etching device, introducing trifluoromethane, and the flow rate of the trifluoromethane is 30 sccm - 50 sccm; adjusting the plasma power to 200 W - 400 W, the bias power to 10 W - 50 W, and the gas pressure to 0 - 20 mTorr. The above etching recipe can enable the material layer to be precisely etched to form a nano-column array, and nano-columns with high height and good perpendicularity can be obtained.

[0034] In some embodiments of the present application, it further includes introducing oxygen into the plasma etching device, and the flow rate of the oxygen ≤ 20 sccm. In this way, more suitable etching conditions can be obtained for the material layer.

[0035] In the third aspect of the embodiments of the present application, a camera module is provided, including a lens assembly; the lens assembly includes the metalens provided in the first aspect of the embodiments of the present application, or includes a metalens prepared according to the preparation method provided in the second aspect of the embodiments of the present application. Due to the adoption of the above metalens, the thickness of the lens assembly is much smaller than that of the lens assembly in the related art, and the imaging quality of the final camera module can even reach or exceed that of the existing camera modules using traditional lens groups, thus having strong market competitiveness.

[0036] In the fourth aspect of the embodiments of the present application, an electronic device is provided, and the electronic device includes the camera module provided in the third aspect of the embodiments of the present application. Due to the adoption of the camera module provided in the embodiments of the present application, the electronic device can have good market prospects.

[0037] In some embodiments of the present application, the above electronic device includes, but is not limited to, terminal devices such as mobile phones, laptop computers, tablet computers, and wearable electronic devices. Description of the Drawings

[0038] Figure 1 is a schematic cross-sectional structure diagram of a metalens provided in an embodiment of the present application;

[0039] Figure 2 is an optical photograph of a metalens provided in an embodiment of the present application;

[0040] Figure 3 is Figure 2 an optical microscope photograph of a local area of the metalens in

[0041] Figure 4A is Figure 3 a scanning electron microscope (SEM) photograph of the surface of a local area in

[0042] Figure 4B isFigure 3 SEM photograph of the surface of another partial area in

[0043] Figure 5 Schematic process flow diagram of the preparation method of the metalens provided by an embodiment of the present application. Detailed implementation manners

[0044] Different from the traditional lens that realizes the focusing of light by changing the optical path difference, the metalens realizes the regulation of light by introducing abrupt changes in optical yield at the junction of two media with sub-wavelength-sized microstructures. It has a very low dependence on the propagation path and propagation distance of light, which is conducive to the miniaturization and integration of optical devices.

[0045] For optical devices, chromatic aberration (also known as "color difference") is a common problem that plagues manufacturers and consumers. Taking a camera device as an example, its lens assembly needs to focus and image visible light. As is well known, visible light is continuous broadband light. When light of multiple wavelengths passes through a lens, multiple different propagation optical paths will be generated, resulting in dispersion and causing chromatic aberration, which seriously affects the imaging quality. Although current metalenses can already better eliminate the chromatic aberration of visible light, their focusing efficiency is quite different from that of traditional lens groups and the numerical aperture is small, which severely restricts the application of metalenses in eliminating chromatic aberration of continuous broadband light.

[0046] To solve the above technical problems, an embodiment of the present application provides a metalens. Please refer to Figure 1 , the metalens 1 provided by the embodiment of the present application includes a substrate 10 and a plurality of nanocolumn arrays disposed on one side surface of the substrate 10. Each nanocolumn array includes a plurality of nanocolumns 20 arranged in an array; the spacing (d) between two adjacent nanocolumns 20 is 20 nm - 240 nm; the aspect ratio of the nanocolumn 20 ≥ 3.57; the planar edge roughness of the nanocolumn 20 ≤ 2 nm. For the convenience of description, nanocolumn A and nanocolumn B are defined as two adjacent nanocolumns. In the embodiment of the present application, the "spacing between two adjacent nanocolumns" can be expressed as the distance between the top of nanocolumn A and the top of nanocolumn B. The top of the nanocolumn 20 refers to the end of the nanocolumn 20 away from the substrate 10. In the embodiment of the present application, a scanning electron microscope (SEM) can be used to measure the aspect ratio, planar edge roughness of the nanocolumn 20, and the spacing between two adjacent nanocolumns.

[0047] In the above-mentioned metalens 1, any nanorod 20 in any nanorod array is a slender and tall structure, and the spacing between two adjacent nanorods 20 is narrow, which can make the arrangement density of the slender and tall microstructures with sub-wavelength size for phase adjustment on the surface of the metalens 1 large and the duty cycle high, so as to significantly improve and finely control the phase compensation of the metalens 1, and thus can preferably eliminate the chromatic aberration generated by continuous broadband light while improving the focusing efficiency and numerical aperture of the metalens 1. Further, controlling the planar edge roughness of the nanorod 20 within the range of ≤2 nm can further reduce the loss of light (especially visible light), and can further improve the focusing efficiency of the metalens 1.

[0048] In the embodiments of the present application, the cross-sectional shape of the nanorod 20 is not specifically limited and can be any symmetric figure that meets the use requirements of the metalens 1. The cross-sectional shape of the nanorod 20 can be simple geometric shapes such as circles, ellipses, squares, rectangles, etc., or complex geometric shapes such as rings, rectangular rings, crosses, and tic-tac-toe shapes. Among them, the cross-section of the nanorod 20 is the section obtained by truncating the nanorod 20 with any plane perpendicular to the height direction of the nanorod 20.

[0049] In some embodiments of the present application, the cross-section of the nanorod 20 is an isotropic complex geometric shape such as a ring, a rectangular ring, a cross, or a tic-tac-toe shape. In this way, the duty cycle of the metalens 1 can be further improved, and then its phase adjustment range can be improved. Of course, in the face of other optical phase control requirements, the cross-sectional shape of the nanorod 20 can also be an anisotropic geometric shape. In this way, a polarization-sensitive nanorod array can be obtained, so that the metalens 1 can have different responses to light with different polarization states.

[0050] In the embodiments of the present application, the aspect ratio of the nanorod 20 refers to "the height (H) of the nanorod 20 / the width (L) of the nanorod 20". Among them, for a cylindrical nanorod 20, the width (L) of the nanorod 20 refers to its diameter; for a cuboid nanorod 20, the width of the nanorod 20 refers to the length of the rectangular cross-section of the nanorod 20; for a nanorod 20 with a complex geometric shape, the width refers to the maximum dimension of its cross-section: for example, the maximum cross-section size of a ring refers to its outer diameter. Specifically, the aspect ratio of the nanorod 20 can be but is not limited to 3.57, 4, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 48, 50, 52, 55, 58, 60, etc. If the aspect ratio of the nanorod 20 is too low (less than 3.57), the phase adjustment range of the metalens 1 will be too small, the ability to eliminate visible light chromatic aberration will become weak, and the application value will be low.

[0051] In some embodiments of the present application, the aspect ratio of the nanorods 20 is 3.57 - 16.7. Considering that in the embodiments of the present application, the planar edge roughness of the nanorods 20 is small and the arrangement density is large, controlling the aspect ratio of the nanorods 20 within the above range can ensure a wide phase modulation range, high focusing efficiency, and large numerical aperture of the metalens 1, while making the metalens 1 easier to fabricate.

[0052] In the embodiments of the present application, the spacing (d) between two adjacent nanorods 20 refers to "the minimum distance between two adjacent nanorods 20". Specifically, the spacing between two adjacent nanorods 20 can be, but is not limited to, 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 32 nm, 35 nm, 38 nm, 40 nm, 45 nm, 50 nm, 60 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 240 nm, etc. If the spacing between two adjacent nanorods 20 is too large (>240 nm), it will lead to too low an arrangement density of the nanorods 20 on the surface of the metalens 1 and a decrease in the duty cycle, resulting in a small focusing efficiency and numerical aperture of the metalens 1, which is not conducive to the application of the metalens 1; specifically, when a metalens 1 with a small focusing efficiency and / or numerical aperture is applied in a camera module, it will lead to poor imaging quality. If the spacing between two adjacent nanorods 20 is too small, it will not only increase the fabrication difficulty of the metalens 1, but also the limited increase in benefits, and even lead to a decrease in the focusing efficiency. In some embodiments of the present application, the spacing between two adjacent nanorods 20 is 20 nm - 39 nm. In this way, a large arrangement density of the nanorods 20 on the surface of the metalens 1 can be ensured, thereby further improving the focusing efficiency and numerical aperture of the metalens 1.

[0053] In the embodiments of the present application, the arrangement periods of the nanorods 20 in a single nanorod array are the same. Among them, the arrangement period of the nanorods 20 refers to the center distance between two adjacent nanorods 20 in a single nanorod array. That is, in a single nanorod array, the center distances between any two adjacent nanorods 20 are equal; the widths of multiple nanorods 20 can be the same or different.

[0054] In the embodiments of the present application, the arrangement periods of the nanorods 20 in multiple nanorod arrays can be the same or different.

[0055] In some embodiments of the present application, any 10 μm of the metalens 1 2 area has at least 70 nanorods 20. For example, 70 - 80 nanorods 20. In this way, the arrangement density of the nanorods 20 in the nanorod array is large, which can further broaden the phase modulation of the metalens 1 and optimize the achromatic aberration effect. Specifically, any 10 μm of the metalens 1 2The number of nanocolumns on the area can be, but is not limited to, 70, 72, 75, 78, 80.

[0056] Specifically, the planar edge roughness of the nanocolumn 20 can be, but is not limited to, 0, 0.2 nm, 0.5 nm, 0.8 nm, 1 nm, 1.2 nm, 1.5 nm, 1.8 nm, 2 nm, etc. In the embodiments of the present application, the planar edge roughness of the nanocolumn 20 includes: the surface roughness of the nanocolumn 20 and the roughness of the edges of the nanocolumn 20, and the chamfer at the end points of the nanocolumn 20. If the planar edge roughness of the nanocolumn 20 > 2 nm, it will especially increase the loss of visible light and reduce the focusing efficiency of the superlens 1.

[0057] In some embodiments of the present application, the planar edge roughness of the nanocolumn 20 is 1 nm - 2 nm. In this way, while sufficiently reducing the loss of visible light, the manufacturing difficulty of the superlens 1 can be reduced, and the cost performance of the superlens 1 can be improved.

[0058] In the embodiments of the present application, when the aspect ratio of the nanocolumn 20 ≥ 3.57 is satisfied, the height of the nanocolumn 20 is not specifically limited, and those skilled in the art can select according to the actual production situation. However, in order to further improve and ensure the phase modulation ability of the superlens 1, in some embodiments of the present application, the height (H) of the nanocolumn 20 ≤ 1000 nm. Specifically, the height of the nanocolumn 20 can be, but is not limited to, 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 620 nm, 650 nm, 680 nm, 700 nm, 720 nm, 750 nm, 780 nm, 800 nm, 820 nm,

[0059] 850 nm, 880 nm, 900 nm, 920 nm, 950 nm, 980 nm, 1000 nm. In some specific embodiments, the height (H) of the nanocolumn 20 is 600 nm - 1000 nm. Controlling the height of the nanocolumn 20 within the above range can ensure that the superlens 1 has a wider phase adjustment range, stronger phase adjustment ability, better visible light achromatic aberration performance, and is beneficial to further improving its focusing efficiency and numerical aperture. In the embodiments of the present application, the height of the nanocolumn can be measured by SEM.

[0060] In some embodiments of the present application, the heights of the nanocolumns 20 within a single nanocolumn array are all equal. Further, all dimensions of the nanocolumns 20 within a single nanocolumn array are equal.

[0061] To achieve different regulation requirements, the arrangement of multiple nano-pillar arrays on the surface of the metalens 1 and / or the sizes of the nano-pillars 20 of the multiple nano-pillar arrays may vary. In some embodiments of the present application, the heights of the multiple nano-pillars 20 in a single nano-pillar array are the same, and the heights of the nano-pillars 20 of the multiple nano-pillar arrays are different: for example, the multiple nano-arrays include a third nano-array and a fourth nano-array, and the heights of all the nano-pillars 20 in the third nano-array are 1000 nm, and the heights of all the nano-pillars 20 in the fourth nano-array are 950 nm. In some other embodiments, the heights of the multiple nano-pillars 20 in a single nano-pillar array are the same, and the heights of the nano-pillars 20 of the multiple nano-pillar arrays are also the same: for example, the heights of the nano-pillars 20 in the third nano-array and the fourth nano-array are both 1000 nm. In still some other embodiments, the heights of the multiple nano-pillars 20 in a single nano-pillar array are different, and the heights of the nano-pillars 20 of the multiple nano-pillar arrays are also different: for example, the heights of some of the nano-pillars 20 in the third nano-array are 1000 nm, and the heights of some other nano-pillars 20 are 950 nm, the heights of some of the nano-pillars 20 in the fourth nano-array are 900 nm, and the heights of some other nano-pillars 20 in the fourth nano-array are 850 nm. Those skilled in the art can make selections according to actual needs.

[0062] In some embodiments of the present application, the width of the nano-pillar 20 is 60 nm - 280 nm. Specifically, the width of the nano-pillar 20 can be but is not limited to 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 110 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, etc. By controlling the width of the nano-pillar 20 within the above range, the cross-sectional area of the nano-pillar 20 can be controlled within a suitable range, and the density of the nano-pillars 20 per unit area of the metalens 1 can be ensured to be large, thereby ensuring strong phase regulation performance of the metalens 1. In the embodiments of the present application, the width of the nano-pillar can be measured by SEM.

[0063] Based on different phase regulation requirements, in some embodiments, the widths of the multiple nano-pillars 20 in a single nano-pillar array are the same. In some other embodiments, the widths of the multiple nano-pillars 20 in a single nano-pillar array are differently distributed, but the width of any nano-pillar 20 is within the range of 30 nm - 280 nm, and the arrangement period of a single nano-pillar array is equal.

[0064] In some embodiments of the present application, the average light transmittance of the metalens 1 in the visible light band is ≥ 60%. Specifically, the visible light includes light with a wavelength of 400 nm - 700 nm. In the embodiments of the present application, an electron microscope or X-ray diffraction is used to characterize the average light transmittance of the metalens 1 in the visible light band. Specifically, the average light transmittance of the metalens 1 in the visible light band can be, but is not limited to, 60%, 65%, 70%, 75%, 80%, 85%, 86%.

[0065] When the height and arrangement density of the nanocolumns 20 are fixed, and their material is a high refractive index and high light transmittance material, the phase modulation function of the metalens 1 can be further optimized. Therefore, in some embodiments of the present application, the material of the nanocolumns 20 is selected from silicon nitride or gallium nitride. In particular, for silicon nitride, its refractive index is not as good as that of gallium nitride, which may result in a relatively small adjustment range when its phase modulation range covers 0 - 2π, resulting in a numerical aperture smaller than that of the gallium nitride metalens 1. However, based on the metalens 1 provided in the embodiments of the present application, when the nanocolumns 20 are silicon nitride nanocolumns 20, the focusing efficiency of the metalens 1 is ≥ 60%; the numerical aperture of the metalens 1 is ≥ 0.5. Specifically, the focusing efficiency of the metalens 1 can be, but is not limited to, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, etc. Specifically, the numerical aperture of the metalens 1 can be, but is not limited to, 0.5, 0.52, 0.55, 0.58, 0.6, 0.62, 0.65. In the embodiments of the present application, an optical transfer function measuring instrument is used to test the focusing efficiency of the metalens. The numerical aperture of the numerical metalens can be calculated based on the focal length of the metalens 1 and the Lens target surface.

[0066] In some embodiments of the present application, please continue to refer to Figure 1 , the included angle (α) between the side wall of the nanocolumn 20 and the substrate 10 is 85° - 90°. In this way, the side wall of the nanocolumn 20 is perpendicular or approximately perpendicular to the substrate 10, which can give full play to the phase adjustment effect of the nanocolumn 20 and ensure a good achromatic aberration effect; it can also avoid the formation of trapezoidal nanocolumns 20, thereby avoiding the phenomenon that the distance between the bottoms of adjacent nanocolumns 20 (the end of the nanocolumn 20 close to the substrate 10) is too small, and reducing the risk that the poor separation at the bottom of the nanocolumn 20 affects the phase adjustment ability. Specifically, the included angle between the side wall of the nanocolumn 20 and the substrate 10 can be, but is not limited to, 85°, 85.5°, 86°, 86.5°, 87°, 87.5°, 88°, 88.5°, 89°, 89.5°, 90°, etc. In some specific embodiments, the side walls of the nanocolumns 20 are all perpendicular to the substrate 10. In the embodiments of the present application, an SEM can be used to test the included angle between the side wall of the nanocolumn 20 and the substrate.

[0067] At present, there is still a problem in the field of metalenses on how to further increase the aperture of the metalens. Theoretically, when the aperture size of the metalens is increased, its ability to eliminate chromatic aberration will be lost. Therefore, the aperture of the metalens currently used to eliminate chromatic aberration is generally in the micron range, and the light collection range is very small; or, there are metalenses that can reach the millimeter level, but their chromatic aberration elimination performance cannot meet the usage requirements, which results in the difficulty of commercial application of the metalenses that can be used to eliminate chromatic aberration in the current related technologies. However, in view of the structural parameters of the nanocolumns 20 and the arrangement parameters of the nanocolumn array of the metalens 1 provided in the embodiments of the present application, even if the aperture of the metalens 1 is made to the millimeter level, an excellent chromatic aberration elimination effect can still be achieved, and a high focusing efficiency and numerical aperture can be realized. In some embodiments of the present application, the aperture of the metalens 1 ≥ 1 mm; for example, 1 mm - 2 mm, and the focusing efficiency ≥ 60%, and the numerical aperture ≥ 0.5. In this way, the metalens 1 has a large light collection area. When it is applied to a camera, it can reduce the thickness of the camera lens assembly while increasing the wide-angle angle of the camera. Specifically, the aperture of the metalens 1 can be, but is not limited to, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.2 mm, etc.

[0068] Please refer to Figures 2 - 4B , Figure 2 The transparent sheet-like object within the circular frame in Figure 3 is Figure 2 the optical photograph of the metalens provided in an embodiment of the present application, Figure 4A and Figure 4B is Figure 3 the optical microscope photograph of a certain area in Figure 4A and Figure 4B are the SEM photographs of the nanocolumn arrays at two different positions in

[0069] In the embodiments of the present application, the material of the above-mentioned substrate 10 can be selected from any material well-known in the art, specifically, it can be selected from materials that can transmit light of various wavelengths. In some embodiments, the substrate 10 is selected from any transparent material that can transmit visible light. Specifically, the material of the above-mentioned substrate 10 is selected from glasses of various components.

[0070] At present, it is difficult to fabricate nanocolumns with a high aspect ratio and low planar edge roughness. It is even more of a challenge in the industry to obtain a micro-nano structured surface with a high density of nanocolumns. Especially for high-hardness materials such as silicon nitride and gallium nitride, the etching of these materials is difficult in itself, and it is even more difficult to fabricate a superlens using silicon nitride or potassium nitride as the medium. To solve the above technical problems, an embodiment of the present application also provides a method for fabricating a superlens. Please refer to Figure 5 , the fabrication method includes:

[0071] S01. Provide a substrate 10 and a material layer 21 disposed on one surface of the substrate 10, and form a first hard mask 30 on the surface of the material layer 21 facing away from the substrate 10; the etching selectivity between the material layer 21 and the first hard mask 30 ≥ 30:1; wherein, the material layer 21 is used to fabricate the aforementioned nanocolumns 20; the etching selectivity refers to the ratio of the etching rate of the first material to the second material under the same etching conditions. In an embodiment of the present application, the first hard mask 30 covers the surface of the material layer 21 facing away from the substrate 10.

[0072] S02. Dispose a photoresist layer 40 on the surface of the first hard mask 30 facing away from the material layer 21. The photoresist layer 40 includes a plurality of photoresist columns 41 disposed at intervals, and the first hard mask 30 between two adjacent photoresist columns 41 is exposed, and the width of the photoresist column 41 is 20 nm - 240 nm, to obtain a first preform;

[0073] S03. Form a second hard mask 50 on the surface of the first preform having the photoresist layer 40 to obtain a second preform; the etching selectivity between the second hard mask 50 and the first hard mask 30 < 1;

[0074] S04. Remove the photoresist layer 40;

[0075] S05. Etch the area of the first hard mask 30 not covered by the second hard mask 50 to obtain a third preform;

[0076] S06. Etch the third preform so that the material layer 21 is transformed into a plurality of nanocolumn arrays, each nanocolumn array includes a plurality of nanocolumns 20 arranged in an array, to obtain a superlens 1; wherein, the aspect ratio of the nanocolumns 20 ≥ 3.57, and the planar edge roughness of the nanocolumns 20 ≤ 2 nm. It can be understood that to transform the material layer 21 into one or more nanocolumn arrays by etching, it is necessary to first transfer the planar pattern of the nanocolumn array (i.e., the orthographic projection of the nanocolumn array on the substrate) or its complementary pattern to the surface of the object to be etched. In an embodiment of the present application, two hard mask conversions (steps S02 - S04) are used to transfer the planar pattern of the nanocolumn array to the surface of the object to be etched, which can significantly improve the planar edge roughness of the finally etched nanocolumns. Specifically:

[0077] It is not difficult to deduce from the above process that the orthographic projection of the photoresist layer 40 on the substrate 10 and the planar pattern of the nanocolumn array to be prepared are complementary patterns. In step S03, a second hard mask 50 is formed on the surface of the first preform on the side with the photoresist layer 40. At this time, the second hard mask 50 is present on the exposed surface of the first hard mask 30 and the surface of the photoresist column 41 facing away from the substrate 10, obtaining a second preform. In step S04, when the photoresist layer 40 is removed, the second hard mask 50 carried on its surface is also removed together. The projection of the remaining second hard mask 50 on the substrate 10 is the planar pattern of the nanocolumn array. At this time, under the protection of the remaining second hard mask 50 layer, the first hard mask 30 is etched, and the planar pattern of the nanocolumn array can be transferred to the surface of the material layer 21; thus far, the transfer of the planar pattern of the nanocolumn array is completed. Compared with the conventional one-time transfer of photoresist in the related art, the special transfer step design provided by the embodiments of the present application overcomes the technical problems that when preparing nanocolumns 20 with a high aspect ratio, it is necessary to increase the height of the photoresist column 41, resulting in a large stripping difficulty, it is very difficult to obtain nanocolumns 20 with a relatively high aspect ratio, and the planar edge roughness of the obtained nanocolumns 20 is high; and the above preparation method can transfer the planar pattern of the dense nanocolumn array to the surface of the third preform completely, smoothly and precisely, providing the possibility for obtaining a densely distributed nanocolumn array. In step S06, the material layer 21 with an etching selectivity ratio of ≥30:1 with respect to the patterned first hard mask 30 layer is etched under the protection of the patterned first hard mask 30 layer, and nanocolumns 20 with a relatively large aspect ratio can be obtained, thereby successfully fabricating the superlens provided by the embodiments of the present application.

[0078] The above preparation method can be used to prepare the aforementioned superlens provided by the embodiments of the present application, and the process reliability of the above preparation method is strong. Those skilled in the art can quickly master its preparation process, with high production efficiency and being suitable for large-scale industrial production. Moreover, the above preparation method can realize the preparation of nanocolumns 20 with different cross-sectional shapes.

[0079] In the embodiments of the present application, the etching selectivity between the material layer 21 and the first hard mask 30 can be, but is not limited to, 30:1, 32:1, 35:1, 38:1, 40:1, 42:1, 45:1, 48:1, 50:1, 52:1, etc. If the above etching selectivity is too low, when preparing the nanocolumns 20 with a specific height, it is necessary to further increase the thickness of the first hard mask 30, which will significantly increase the difficulty of etching and the nanocolumns 20 with a predetermined aspect ratio cannot be obtained; in addition, it may also cause the phenomenon that the planar edge roughness of the nanocolumns 20 becomes larger, and the superlens provided by the embodiments of the present application cannot be obtained. In some specific embodiments, the etching selectivity between the material layer 21 and the first hard mask 30 is (30-50):1. In this way, the production cost can be controlled at a relatively low level while ensuring the etching effect; at the same time, it is also beneficial to control the better perpendicularity of the nanocolumns 20.

[0080] In some embodiments of the present application, in step S01, the material layer 21 can be formed on the surface of the substrate 10 by, but is not limited to, a deposition method. The process parameters of the deposition can be selected according to the material of the material layer 21, and the present application does not limit this.

[0081] In some embodiments of the present application, in step S01, the first hard mask 30 is formed on the surface of the material layer 21 facing away from the substrate 10 by a deposition process. In some specific embodiments, a metal chromium layer is deposited on the surface of the material layer 21 facing away from the substrate 10. In this way, the obtained first hard mask 30 layer is uniform and dense, and the interface with the material layer 21 is tightly bonded.

[0082] In some embodiments of the present application, the material of the material layer 21 is selected from gallium nitride or silicon nitride. The refractive index and light transmittance of the above materials are relatively high, which is beneficial to ensuring better achromatic aberration effect of the prepared superlens.

[0083] In some embodiments of the present application, the material of the material layer 21 is selected from gallium nitride or silicon nitride, and the material of the first hard mask 30 is selected from any one of metal chromium, metal aluminum, and metal silver. In some specific embodiments, the material of the first hard mask is metal chromium. Metal chromium has strong anti-etching ability and high hardness. During the preparation process of the superlens, especially in step S06, it can firmly adhere to the surface of the material layer 21, reducing the risk of structural deformation of the nanocolumns 20 or the increase of planar edge roughness caused by mask curling.

[0084] Although the etching selectivity of the first hard mask 30 to the material layer 21 is relatively large, during the etching process of the material layer 21, the first hard mask 30 will also be etched away by a certain thickness. Therefore, in order to ensure that the height of the nanocolumns 20 is not lost during the etching process of the material layer 21 and to ensure the uniformity of the etching of the material layer 21, in some embodiments of the present application, the thickness of the first hard mask 30 ≥ 20 nm. Further, in order to control production costs, in some specific embodiments, the thickness of the first hard mask 30 is 20 nm - 50 nm. Specifically, the thickness of the first hard mask 30 can be, but is not limited to, 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 32 nm, 35 nm, 38 nm, 40 nm, 42 nm, 45 nm, 48 nm, 50 nm, etc.

[0085] It can be understood that the thickness of the material layer 21 is generally equal to the height of the nanocolumns 20 of the superlens to be prepared. Therefore, in some embodiments of the present application, the thickness of the material layer 21 is 600 nm - 1000 nm.

[0086] In some embodiments of the present application, the formation of the photoresist layer 40 in step S02 includes: coating a photoresist composition on the surface of the first hard mask 30 layer facing away from the substrate 10, determining the exposure area according to a preset pattern, and sequentially performing exposure treatment and development treatment on the photoresist layer 40 to obtain spaced-apart photoresist columns 41. Among them, the above photoresist composition can be a negative material, and the exposure treatment causes the photoresist in the exposure area to undergo a polymerization reaction and / or a crosslinking reaction, and the development treatment removes the photoresist composition in the unexposed area. At this time, the preset pattern is a complementary pattern of the planar pattern of the nanocolumn array; or, the photoresist composition can be a positive material, and the exposure treatment causes the photoresist in the exposure area to undergo solubilization, and the development treatment removes the photoresist composition in the exposure area. At this time, the preset pattern is the planar pattern of the nanocolumn array. Specifically, the photoresist (photosensitive material) in the photoresist combination can be selected from materials well-known to those skilled in the art. In some specific embodiments, the photosensitive material includes, but is not limited to, polymethyl methacrylate (PMMA), metal-organic cluster-based photosensitive materials. The above photosensitive materials have high pattern resolution and low edge roughness, which is beneficial to reducing the planar edge roughness of the finally prepared nanocolumns 20.

[0087] In the embodiments of the present application, the exposure treatment can adopt any exposure process well-known to those skilled in the art. In some specific embodiments, an electron beam is used to perform exposure treatment on the photoresist layer 40.

[0088] In the embodiments of the present application, the spacing between two adjacent nano-columns 20 substantially depends on the width of the photoresist column 41; thus, the width of the photoresist column 41 refers to the width of the bottom surface of the photoresist column 41 (i.e., the end face close to the first hard mask 30). In step S02, the width of the photoresist column 41 can be, but is not limited to, 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 32 nm, 35 nm, 38 nm, 40 nm, 45 nm, 50 nm, 60 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 240 nm, etc. If the width of the photoresist column 41 is too large, the spacing between two adjacent nano-columns 20 in the fabricated superlens will be too large.

[0089] In some specific embodiments of the present application, the width of the photoresist column 41 is 20 nm - 39 nm. At this time, the phase adjustment ability of the fabricated superlens is better.

[0090] In some embodiments of the present application, in step S03, the second hard mask 50 is formed by a deposition process. Specifically, the material of the second hard mask 50 is deposited on the surface of the first preform having the photoresist layer 40. In this way, the material of the second hard mask 50 can be smoothly covered on the surface of the photoresist column 41 facing away from the substrate 10 and on the surface of the first hard mask 30 exposed between the photoresist columns 41, and the thickness of the fabricated second hard mask 50 is uniform and the density is high.

[0091] In some embodiments of the present application, the material of the second hard mask 50 is selected from silicon dioxide. In the etching system provided by the embodiments of the present application, silicon dioxide is a mask suitable for materials such as chromium, silver, or aluminum, and using it as the material of the second hard mask 50 can improve the accuracy of pattern transfer.

[0092] In some embodiments of the present application, the first hard mask 30 is a metal chromium layer, and the second hard mask 50 is a silicon dioxide layer. At this time, in some specific embodiments, the thickness of the second hard mask 50 is 10 nm - 40 nm. In this way, when etching the first hard mask 30 in step S05, the safety and uniformity of the etching can be ensured, which is beneficial to obtaining a superlens with a target structure. Specifically, the thickness of the second hard mask 50 can be, but is not limited to, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 32 nm, 35 nm, 38 nm, 40 nm, etc. In some specific embodiments, the thickness ratio of the first hard mask 30 to the second hard mask 50 is (2.3 - 4):1. In this way, the risk that the second hard mask 50 is completely etched away and the thickness of the first hard mask 30 is lost during the etching process of step S05 can be reduced, thereby ensuring the safety of the etching of the material layer 21 in step S06, and further not losing the preset height of the final nanocolumns 20. Specifically, the thickness ratio of the first hard mask 30 to the second hard mask 50 can be, but is not limited to, 2.3:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, etc.

[0093] In some specific embodiments, the thickness of the photoresist layer 40 is greater than or equal to the thickness of the second hard mask 50. In this way, it is beneficial to smoothly strip the photoresist layer 40 in step S04, and the material residue of the photoresist layer 40 can be avoided.

[0094] In some embodiments of the present application, removing the photoresist layer 40 in step S04 may include: contacting the second preform with a stripping solution to make the material of the photoresist layer 40 react with the stripping solution, and then removing the reacted material of the photoresist layer 40 by means such as gas purging. Specifically, the above contacting the second preform with the stripping solution includes, but is not limited to: placing the second preform in the stripping solution and reacting for a period of time, or rinsing the second preform with the stripping solution. Those of ordinary skill in the art can determine the contact method and contact duration between the stripping solution and the second preform according to the actual production situation, as long as the photoresist layer 40 can be smoothly removed.

[0095] In some embodiments of the present application, the etching process in step S05 can adopt gas dry etching (i.e., plasma etching).

[0096] In some embodiments of the present application, in step S05, etching the area of the first hard mask 30 not covered by the second hard mask 50 includes: placing the second preform after removing the photoresist layer 40 in a plasma etching equipment and introducing chlorine gas for etching.

[0097] In some specific embodiments, the material of the first hard mask 30 is metallic chromium. At this time, chlorine molecules are bombarded by high-voltage accelerated ions to eject a plasma containing Cl - (chloride ion oxidation trap), which can take away the electrons in the Cr atoms, turning the Cr atoms into positively charged chromium ions. The adhesion force of the chromium ions to other unreacted Cr atoms is relatively weak and they will be blown away by the gas in the equipment, thus realizing the chemical etching of the metallic chromium (the first hard mask 30). At the same time, chlorine also has a physical bombardment effect on the first hard mask 30. Therefore, under the dual action of chemical etching and physical bombardment, the first hard mask 30 not covered by the second hard mask 50 can be successfully removed.

[0098] In some embodiments of the present application, in step S05, the flow rate of the above-mentioned chlorine gas is 20 sccm - 40 sccm. A suitable chlorine gas flow rate can ensure that there is sufficient Cl - for chemical etching of the first hard mask 30 without corroding other structures. Specifically, the flow rate of the above-mentioned chlorine gas can be, but is not limited to, 20 sccm, 22 sccm, 25 sccm, 28 sccm, 30 sccm, 32 sccm, 35 sccm, 38 sccm, 40 sccm, etc.

[0099] In some embodiments of the present application, in step S05, the plasma power of the plasma equipment is adjusted to 1000 W - 1400 W. In this way, the Cl - ion concentration in the equipment can be controlled within a suitable range to ensure the etching effect and etching rate. Specifically, in step S05, the plasma power can be, but is not limited to, 1000 W, 1050 W, 1100 W, 1150 W, 1200 W, 1250 W, 1300 W, 1350 W, 1400 W, etc.

[0100] In order to maintain the dynamic balance of the air pressure in the plasma equipment and improve the etching effect of the plasma, in step S05, the air pressure in the plasma etching equipment (specifically its reaction chamber) is maintained at 0 - 20 mTorr. Specifically, the air pressure in the plasma etching equipment can be, but is not limited to, 1 mTorr, 3 mTorr, 5 mTorr, 8 mTorr, 10 mTorr, 12 mTorr, 15 mTorr, 18 mTorr, 20 mTorr, etc.

[0101] To ensure the etching effect, generally, the physical bombardment intensity on the material to be etched is controlled by the bias power of the plasma etching equipment. In some embodiments of the present application, in step S05, the bias power of the plasma etching equipment is ≤ 50 W. Of course, in some cases, it is not necessary to adjust the physical bombardment effect. At this time, the bias power of the plasma etching equipment can be adjusted to 0. Specifically, in step S05, the bias power of the plasma etching equipment can be, but is not limited to, 0, 2 W, 5 W, 8 W, 10 W, 12 W, 15 W, 18 W, 20 W, 22 W, 25 W, 30 W, 35 W, 40 W, 45 W, 50 W.

[0102] To avoid the re - combination of the bombarded Cl - again, in step S05, oxygen is introduced into the plasma etching equipment to adjust the proportion of chlorine gas in the equipment. In some specific embodiments, in step S05, the flow rate of oxygen is ≤ 10 sccm. Specifically, the flow rate of oxygen can be, but is not limited to, 1 sccm, 2 sccm, 5 sccm, 8 sccm, 10 sccm, etc.

[0103] In some embodiments of the present application, in step S05, after etching the first hard mask 30, a second hard mask 50 may remain on the surface of the first hard mask 30 facing away from the substrate 10, or the second hard mask 50 may not exist.

[0104] In some specific embodiments of the present application, step S05 includes: placing the second pre - form after removing the photoresist layer 40 in the plasma etching equipment, and the etching conditions are: the flow rate of chlorine gas is 20 sccm - 40 sccm, the flow rate of oxygen is 0 - 10 sccm, the plasma power is 1000 W - 1400 W, and the bias power is 0 - 50 w.

[0105] In some embodiments of the present application, the gas dry etching of the material layer 21 is also used to prepare the nanowires 20.

[0106] In view of the high hardness of silicon nitride and gallium nitride, it is very difficult to obtain nanowires 20 with a high aspect ratio by gas etching method. To etch a nanowire array with a large depth on the basis of the close arrangement of the nanowires 20 (for example, the height of the nanowires 20 is 600 nm - 1000 nm), it is even more difficult. Therefore, in some embodiments of the present application, in step S06, the third pre - form is placed in the plasma etching equipment, and trifluoromethane is introduced. The F generated by the impact of trifluoromethane -Etch the silicon nitride layer or the gallium nitride layer. Understandably, the etching process in step S06 is a process in which the height of the nanocolumns 20 continuously increases. However, due to the lateral etching in the gas dry etching, as the etching process progresses, the side walls of the nanocolumn 20 structures formed first may also be etched, resulting in deformation of the finally obtained nanocolumn 20 structures, low perpendicularity, and even structural collapse. F - It has strong corrosiveness to the material of the material layer 21. As the etching progresses, the lateral etching may become more obvious. At this time, a single F - etching will cause deformation of the nanocolumn 20 structure, but after the trifluoromethane molecules are bombarded by high-speed electrons, positively charged carbon-containing groups will also be generated. This part of the carbon-containing groups will adhere to the side walls of the already formed nanocolumn 20 structures, protecting them from lateral etching, thereby ensuring the integrity and perpendicularity of the finally fabricated nanocolumns 20. In some specific embodiments, the flow rate of trifluoromethane is 30 sccm - 50 sccm. A suitable flow rate can make trifluoromethane easily ionized and ensure that there is a sufficient amount of F - and carbon-containing groups in the reaction chamber to ensure a relatively high etching rate. Specifically, in step S06, the flow rate of trifluoromethane can be but is not limited to 30 sccm, 32 sccm, 35 sccm, 38 sccm, 40 sccm, 42 sccm, 45 sccm, 48 sccm, 50 sccm, etc.

[0107] Furthermore, in order to control the concentration of F - and carbon-containing groups in the plasma etching equipment to be relatively appropriate and ensure the etching effect, in step S06, the plasma power is controlled to be 200 W - 400 W. Specifically, in step S06, the plasma can be but is not limited to 200 W, 220 W, 250 W, 280 W, 300 W, 320 W, 350 W, 380 W, 400 W, etc.

[0108] In addition to adhering to the side walls of the already formed nanocolumn 20 structures, the above-mentioned carbon-containing groups may also adhere to the surface of the material layer 21 to be etched. At this time, in order to remove the carbon-containing groups on the surface to be etched and obtain nanocolumns 20 with a relatively large height, a bias voltage needs to be applied to bombard away the carbon-containing groups adhering to the surface to be etched. In some embodiments of the present application, the bias power of the plasma etching equipment is 10 W - 50 W. Specifically, in step S06, the bias power of the plasma equipment can be but is not limited to 10 W, 12 W, 15 W, 18 W, 20 W, 22 W, 25 W, 28 W, 30 W, 32 W, 35 W, 38 W, 40 W, 42 W, 45 W, 48 W, 50 W, etc.

[0109] Considering some cases, when the F -When the content is sufficient, there may be an excessive amount of carbon-containing groups in the reaction chamber that may interfere with the etching reaction. At this time, oxygen can be introduced into the plasma etching equipment, and oxygen anions can react with the excessive positively charged carbon-containing groups to generate CO 2 and be discharged from the reaction chamber, thereby eliminating the interference of excessive carbon-containing groups. In some specific embodiments, in step S06, the flow rate of oxygen ≤ 20 sccm. Specifically, in step S06, the flow rate of oxygen can be but is not limited to 1 sccm, 2 sccm, 5 sccm, 8 sccm, 10 sccm, 12 sccm, 15 sccm, 18 sccm, 20 sccm, etc.

[0110] Similarly, in order to ensure the etching effect and maintain the dynamic pressure balance in the plasma etching equipment (specifically its reaction chamber), in some embodiments of the present application, in step S06, the pressure in the plasma etching equipment is controlled to be 0 - 20 mTorr.

[0111] In some embodiments of the present application, step S06 includes: placing the third preform in the plasma etching equipment, and the etching conditions are: the flow rate of trifluoromethane is 30 sccm - 50 sccm, the flow rate of oxygen is 0 - 20 sccm, the plasma power is 200 W - 400 W, and the bias power is 10 W - 50 W. In this way, not only can a nanocolumn array with a high aspect ratio and dense arrangement be obtained, but also the verticality of the obtained nanocolumns 20 is good. For example, the angle between the side wall of the nanocolumn 20 and the substrate 10 is 85° - 90°.

[0112] The embodiment of the present application also provides a camera module, including a lens assembly; wherein, the lens assembly includes the superlens provided by the embodiment of the present application, or includes a superlens prepared according to the preparation method provided by the embodiment of the present application. Due to the adoption of the above superlens, the thickness of the lens assembly is much smaller than that of the lens assembly in the related art, and the imaging quality of the final camera module can even reach or exceed that of the existing camera modules using traditional lens groups, thus having strong market competitiveness.

[0113] In the embodiment of the present application, the above camera module is included in but not limited to terminal devices such as mobile phones, laptop computers, tablet computers, and wearable electronic devices.

[0114] The embodiment of the present application also provides an electrical device, including the camera module provided by the embodiment of the present application. Due to the adoption of the camera module provided by the embodiment of the present application, the electrical device can have good market prospects.

[0115] In the embodiments of the present application, the above-mentioned electrical equipment includes, but is not limited to, terminal devices such as mobile phones, laptop computers, tablet computers, wearable electronic devices, etc. Of course, the above-mentioned camera module can also be applied to other electrical equipment, such as monitoring equipment, dash cams, etc.

[0116] In the embodiments of the present application, the range value represented by "a-b" includes the endpoint values a and b. For example, the range represented by "10-300" includes the endpoint value 10 and the endpoint value 300.

[0117] The above is the exemplary embodiment of the present application. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and refinements can be made to it, and these improvements and refinements are also regarded as the protection scope of the present application.

Claims

1. A metalens, characterized in that, it includes a substrate and a plurality of nano - pillar arrays disposed on one surface of the substrate, and each of the nano - pillar arrays includes a plurality of nano - pillars arranged in an array; the spacing between two adjacent nano - pillars is 20nm - 240nm; the aspect ratio of the nano - pillar is ≥3.57; the roughness of the planar edge of the nano - pillar is ≤2nm.

2. The metalens according to claim 1, characterized in that, the spacing between two adjacent nano - pillars is 20nm - 39nm.

3. The metalens according to claim 1 or 2, characterized in that, the aspect ratio of the nano - pillar is 3.57 - 16.

7.

4. The metalens according to any one of claims 1 - 3, characterized in that, the height of the nano - pillar is 600nm - 1000nm; the width of the nano - pillar is 60nm - 280nm.

5. The metalens according to any one of claims 1 - 4, characterized in that, the roughness of the planar edge of the nano - pillar is 1nm - 2nm.

6. The metalens according to any one of claims 1 - 5, characterized in that, the included angle between the side wall of the nano - pillar and the substrate is 85° - 90°.

7. The metalens according to any one of claims 1 - 6, characterized in that, Any 10 μm of the metalens 2 has at least 70 of the nanocolumns on the area thereof.

8. The metalens according to any one of claims 1 - 7, characterized in that, the material of the nano - pillar is selected from silicon nitride or gallium nitride.

9. The metalens according to any one of claims 1 - 8, characterized in that, the heights of the nano - pillars in a single nano - pillar array are equal.

10. The metalens according to claim 9, characterized in that, the heights of the nano - pillars in multiple nano - pillar arrays are equal.

11. The metalens according to any one of claims 1 - 10, characterized in that, the aperture of the metalens is ≥1mm.

12. The metalens according to any one of claims 1 - 11, characterized in that, the average transmittance of the metalens in the visible light band is ≥60%.

13. The metalens according to any one of claims 1 - 12, characterized in that, the numerical aperture of the metalens is ≥0.

5.

14. The metalens according to any one of claims 1 - 13, characterized in that, the focusing efficiency of the metalens is ≥60%.

15. A method for manufacturing a metalens, characterized in that, it includes: providing a substrate and a material layer disposed on one surface of the substrate, and forming a first hard mask on the surface of the material layer facing away from the substrate; the etching selectivity ratio of the material layer to the first hard mask is ≥30:1; disposing a photoresist layer on the surface of the first hard mask facing away from the material layer, the photoresist layer includes a plurality of photoresist columns arranged at intervals, the first hard mask between two adjacent photoresist columns is exposed, and the width of the photoresist column is 20nm - 240nm, to obtain a first preform; forming a second hard mask on the surface of the first preform having the photoresist layer to obtain a second preform; the etching selectivity ratio of the second hard mask to the first hard mask is <1; Remove the photoresist layer, and etch the area of the first hard mask that is not covered by the second hard mask to obtain a third preform; Etch the third preform so that the material layer is transformed into a plurality of nanocolumn arrays, and each of the nanocolumn arrays includes a plurality of nanocolumns arranged in an array to obtain a superlens; wherein, the aspect ratio of the nanocolumns ≥ 3.57, and the planar edge roughness of the nanocolumns ≤ 2 nm.

16. The preparation method according to claim 15, wherein, the material of the first hard mask includes chromium metal, silver metal or aluminum metal; the material of the second hard mask is silicon dioxide.

17. The preparation method according to claim 15 or 16, wherein, the thickness of the first hard mask is 20 nm - 50 nm; the thickness of the second hard mask is 10 nm - 40 nm.

18. The preparation method according to any one of claims 15 - 17, wherein, etching the area of the first hard mask that is not covered by the second hard mask includes: Placing the second preform after removing the photoresist layer in a plasma etching device, introducing chlorine gas, and the flow rate of the chlorine gas is 20 sccm - 40 sccm; adjusting the plasma power to 1000 W - 1400 W, the bias power to 0 - 50 W, and the gas pressure to 0 - 20 mTorr.

19. The preparation method according to claim 18, wherein, it further includes introducing oxygen gas into the plasma etching device, and the flow rate of the oxygen gas ≤ 10 sccm.

20. The preparation method according to any one of claims 15 - 19, wherein, etching the third preform includes: Placing the third preform in a plasma etching device, introducing trifluoromethane, and the flow rate of the trifluoromethane is 30 sccm - 50 sccm; adjusting the plasma power to 200 W - 400 W, the bias power to 10 W - 50 W, and the gas pressure to 0 - 20 mTorr.

21. The preparation method according to claim 20, wherein, it further includes introducing oxygen gas into the plasma etching device, and the flow rate of the oxygen gas ≤ 20 sccm.

22. A camera module, wherein, it includes a lens assembly; the lens assembly includes the superlens according to any one of claims 1 - 14, or includes the superlens prepared by the preparation method according to any one of claims 15 - 21.

23. An electronic device, wherein, the electronic device includes the camera module according to claim 22.

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