A nano-lens array and a method for manufacturing the same

Abstract

The application discloses a nano-lens array and a preparation method thereof. The preparation method of the nano-lens array comprises the following steps: coating photoresist on one surface of a substrate, shielding the photoresist by using a mask plate with a circular hole array, and then performing exposure treatment and development treatment on the photoresist, so as to obtain a photoresist film with a circular hole array on the substrate; plating a metal layer on the substrate with the photoresist film with the circular hole array; stripping the photoresist film from the substrate to obtain a metal disc array; performing annealing treatment on the substrate with the metal disc array, so that the metal disc array is melted and condensed into a metal sphere array, and the metal sphere array is used as an etching mask of the substrate; and performing dry etching on the substrate with the metal sphere array to obtain a nano-lens array. The nano-lens array prepared by the preparation method has low cost and simple operation.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a nanolens array and its fabrication method. Background Technology

[0002] Currently, the fabrication and application of photonic devices at the micrometer and even nanometer scale has become an important development direction. Nanostructures and their arrays have the function of separating individual color centers and enhancing the light extraction efficiency of color centers in the field of photonics, and have broad application prospects in quantum communication, quantum physics, electromagnetic measurement and other fields.

[0003] In applications of solid-state color center single-photon sources, the photon signal intensity is relatively low. This is mainly because most photons emitted by the single-photon source structure cannot escape from the dielectric material. The materials used for the solid color centers, such as diamond and silicon carbide, have high refractive indices, leading to a stronger total internal reflection effect. Therefore, it is essential to design single-photon source structures and fabrication methods suitable for avoiding photon emission due to total internal reflection. A single-photon source structure consists of a color center and a nanolens array; photons emitted by the color center are refracted through the nanolens array. Currently, the fabrication of nanolens-based single-photon sources mainly utilizes a combination of electron beam lithography and dry etching. However, the electron beam lithography equipment used in this method is expensive, resulting in high fabrication costs and limiting its widespread use. This method also presents certain complexities and limitations for large-scale fabrication of nanolens arrays. Summary of the Invention

[0004] Therefore, it is necessary to provide a nanolens array and its preparation method to solve the technical problem that the preparation of nanolens arrays requires an electron beam exposure machine, which leads to high costs in the preparation of nanolens arrays.

[0005] The present invention provides a method for fabricating a nanolens array, comprising the following steps:

[0006] Photoresist is coated on one surface of a substrate, the photoresist is masked with a mask having an array of circular holes, and then the photoresist is exposed and developed to obtain a photoresist film with an array of circular holes on the substrate.

[0007] A metal layer is deposited on the substrate of the photoresist film having an array of circular holes;

[0008] The photoresist film is peeled off from the substrate to obtain a metal disk array;

[0009] The substrate having the metal disk array is annealed to melt and condense the metal disk array into a metal sphere array, which serves as an etching mask for the substrate.

[0010] The substrate having the array of metal spheres is subjected to dry etching to obtain a nanolens array.

[0011] Furthermore, prior to the step of coating a photoresist on one surface of the substrate, the method further includes: acid washing the surface of the substrate to remove impurities from the substrate surface.

[0012] Furthermore, during the annealing process of the substrate having the metal disk array, the substrate is tilted.

[0013] Furthermore, the tilt angle of the substrate is less than 30°.

[0014] Furthermore, the annealing process on the substrate having the metal disk array is performed in a vacuum environment or an inert gas atmosphere.

[0015] Furthermore, after the step of dry etching the substrate having the array of metal spheres, the method further includes:

[0016] The substrate after dry etching is acid-washed to remove residual metals and other impurities.

[0017] Furthermore, the diameter of a single metal disk in the metal disk array is 0.5µm to 5µm.

[0018] Furthermore, the thickness of the metal layer is 5 nm to 500 nm.

[0019] Furthermore, the substrate is made of diamond, gallium nitride, and silicon carbide.

[0020] The present invention also provides a nanolens array, which is prepared by the above-described preparation method. The nanolens array has the same spacing between each nanolens, and the spacing is 0.5 to 50 μm.

[0021] This invention provides a method for fabricating a nanolens array. An annealing process is performed on a substrate containing a metal disk array. The metal disk array melts, and due to the surface tension of the molten metal, the metal disk array condenses into a metal sphere array. During this condensation process, the volume of a single metal disk remains essentially constant, while the diameter of a single metal sphere is much smaller than the diameter of a single metal disk. The diameter of a single metal disk decreases from the micrometer scale to the nanometer scale of the metal sphere diameter, thus serving as an etching mask. Dry etching is then performed on the substrate containing the metal sphere array to obtain the nanolens array. This fabrication method only requires a conventional exposure machine combined with conventional photolithography technology to obtain the nanolens array. Furthermore, the size of the fabricated nanolens array is much smaller than the minimum resolution of conventional photolithography machines. It eliminates the need for expensive electron beam lithography machines and avoids the complex processes of direct writing on photoresist in electron beam lithography. This method results in low-cost, simple-to-operate nanolens arrays suitable for large-scale fabrication. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram showing the top and side views of the nanolens array in an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of etching and acid washing in the nanolens array fabrication method of this invention.

[0025] 1. Substrate; 2. Metal disk array; 3. Metal sphere array; 4. Nanolens array.

[0026] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0029] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the term "and / or" throughout the text includes three solutions; taking A and / or B as an example, it includes technical solution A, technical solution B, and a technical solution that simultaneously satisfies A and B. Furthermore, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0030] In some embodiments, such as Figure 1 and Figure 2 As shown, A represents annealing, B represents etching, and C represents acid pickling. A method for fabricating a nanolens array includes the following steps:

[0031] S100. Photoresist is coated on one surface of substrate 1. The photoresist is then masked using a mask with an array of circular holes. The photoresist is then exposed and developed to obtain a photoresist film with an array of circular holes on substrate 1. Specifically, substrate 1 is selected from a smooth-surfaced color center carrier material. The material of substrate 1 is diamond, gallium nitride, silicon carbide, or other color center carrier materials.

[0032] S200. A metal layer is deposited on the substrate 1, which has a photoresist film with an array of circular holes. Specifically, the diameter of a single metal disk in the metal disk array 2 is 0.5 μm to 5 μm. More specifically, the thickness of the metal layer is 5 nm to 500 nm. The material of the metal layer is a metal with good ductility and high surface tension when molten, such as gold or silver.

[0033] S300, The photoresist film is peeled off from the substrate 1 to obtain the metal disk array 2.

[0034] S400, Annealing is performed on a substrate 1 having a metal disk array 2 to melt and condense the metal disk array 2 into a metal sphere array 3, which serves as an etching mask.

[0035] S500, dry etching is performed on substrate 1 with metal sphere array 3 to obtain nanolens array 4.

[0036] This invention provides a method for fabricating a nanolens array 4. A photoresist is coated onto a substrate 1. The photoresist is exposed through a mask with a circular aperture array. During exposure, the photoresist under the circular aperture array is not blocked by the mask and is in an exposed state, allowing it to dissolve. The other parts of the photoresist are blocked by the mask and remain unexposed. This unexposed photoresist is retained. After development, a photoresist film with a circular aperture array is obtained. A metal layer is deposited on the substrate 1 with the photoresist film containing the circular aperture array, such that the metal layer of the circular aperture array portion is directly deposited on the substrate 1, while the other portions are deposited on the photoresist film. When the photoresist film is peeled off from the substrate 1, the metal layer deposited on the photoresist film is peeled off, leaving the metal layer of the circular aperture array portion, which is the metal disk array 2. Annealing is performed on a substrate 1 containing a metal disk array 2, causing the metal disk array 2 to melt. Due to the surface tension of the molten metal, the metal disk array 2 condenses into a metal sphere array 3. During the condensation process, the volume of a single metal disk remains essentially constant, while the diameter of a single metal sphere is much smaller than the diameter of a single metal disk. The diameter of a single metal disk decreases from the micrometer scale to the nanometer scale of the metal sphere diameter, thus serving as an etching mask. Dry etching is then performed on the substrate 1 containing the metal sphere array 3 to obtain a nanolens array 4. This fabrication method only requires a conventional exposure machine combined with conventional photolithography to obtain the nanolens array 4. Furthermore, the size of the fabricated nanolens array 4 is much smaller than the minimum resolution size of conventional photolithography machines. It eliminates the need for expensive electron beam lithography machines and avoids complex processes such as direct writing on photoresist in electron beam lithography. This method results in a low-cost and simple fabrication method for nanolens array 4, suitable for large-scale fabrication.

[0037] S100, Before the step of coating photoresist on substrate 1 and exposing the photoresist through a mask with a circular aperture array to obtain a photoresist film with a circular aperture array on substrate 1, the following steps are also included:

[0038] S110. The surface of substrate 1 is acid-washed to remove impurities from the surface of substrate 1.

[0039] S400. During the annealing process of the substrate 1 with the metal disk array 2, the substrate 1 is tilted. Specifically, the tilt angle of the substrate 1 is less than 30°. After the metal disks condense into metal spheres, micro-protrusions that conform to the outer periphery of the metal disks are generated. With the substrate 1 tilted, all the metal spheres roll in the tilt direction. When all the metal spheres roll to their respective micro-protrusions, all the metal spheres abut against their respective micro-protrusions, so that the metal sphere array 3 is more orderly and the performance of the nanolens array 4 is improved.

[0040] S400. Annealing of the substrate 1 with the metal disk array 2 is performed in a vacuum environment or an inert gas atmosphere, where the inert gas does not react with the metal layer at high temperatures. During annealing, the annealing temperature is close to or higher than the melting point of the metal layer.

[0041] S500, after the step of dry etching the substrate 1 having the metal sphere array 3, the following is also included:

[0042] S510. The substrate 1 after dry etching is acid-washed to remove residual metal and other impurities.

[0043] In another embodiment, a nanolens array 4 is prepared by the above-described preparation method. The spacing between each nanolens in the nanolens array 4 is the same or specified. The arrangement of the nanolenses in the array can be a tetrahedral arrangement, a hexagonal close-packed arrangement, or a specified position arrangement, and the spacing is 0.5 to 50 μm.

[0044] To better explain the technical solution of the present invention, the following specific embodiments are listed.

[0045] Example 1

[0046] Step 1: First clean a 3×3mm area with aqua regia. 2 The diamond substrate was then ultrasonically cleaned for 10 minutes each with acetone, isopropanol, and deionized water, and then dried with nitrogen gas.

[0047] A 3μm thick layer of SPR220 photoresist was spin-coated at 90℃. After pre-baking for 90 seconds, the photoresist was shielded using a mask with a circular aperture array, and exposed to UV light for 8 seconds. After exposure, the mask was removed, resulting in multiple 3μm diameter circular apertures, forming a circular aperture array photoresist film. Gold plating with a thickness of 300nm was applied to both the diamond substrate and the photoresist film. The photoresist film was then peeled off from the diamond substrate to obtain multiple gold disks with a diameter of 3μm and a thickness of 300nm. These gold disks formed a gold disk array.

[0048] Step 2: Perform rapid annealing on the gold disk array on the diamond substrate. The temperature is rapidly increased at a rate of 10℃ to 100℃ per second, and the annealing temperature is 1200℃. The temperature is held for 30 seconds, which causes the gold disks to melt and condense into gold microspheres. Multiple gold microspheres form a gold microsphere array. The gold microsphere array is then cooled to room temperature by natural cooling or rapid cooling.

[0049] Step 3: The diamond substrate with the gold microsphere array obtained in Step 2 is subjected to inductively coupled plasma etching. The etching gases are argon and oxygen, and the gas flow rates are argon 5 sccm and oxygen 15 sccm. After etching for 5 minutes, it is subjected to aqua regia washing treatment to finally obtain an ordered diamond nanolens array.

[0050] Example 2

[0051] Step 1: First clean a 3×3mm area with aqua regia. 2 The diamond substrate was then ultrasonically cleaned for 10 minutes each with acetone, isopropanol, and deionized water, and then dried with nitrogen gas.

[0052] A 1μm thick layer of AZ5214 photoresist was spin-coated at 100℃. After pre-baking for 90 seconds, the photoresist was covered with a mask containing a circular aperture array. Exposure was performed using a UV lithography machine for 5 seconds. After exposure, the mask was removed, resulting in multiple 1μm diameter circular apertures, forming a circular aperture array photoresist film. A 100nm thick gold plating was then applied to the diamond substrate and the photoresist film. The photoresist film was then peeled off from the diamond substrate to obtain multiple gold disks with a diameter of 1μm and a thickness of 100nm. These gold disks formed a gold disk array.

[0053] Step 2: Perform rapid annealing on the gold disk array on the diamond. The temperature is rapidly increased at a rate of 10℃ to 100℃ per second, reaching an annealing temperature of 1100℃ and held for 30 seconds. This causes the gold disks to melt and condense into gold microspheres. Multiple gold microspheres form a gold microsphere array, which is then cooled to room temperature through natural cooling or rapid cooling.

[0054] Step 3: The substrate with the gold microsphere array obtained in Step 2 is subjected to inductively coupled plasma etching. The etching gas is oxygen, the gas flow rate is 15 sccm, and the etching time is 3 minutes. After etching, it is subjected to aqua regia washing treatment to finally obtain an ordered diamond nanolens array.

[0055] Example 3

[0056] Step 1: Clean the gallium nitride substrate with hydrochloric acid, then ultrasonically clean it with acetone, isopropanol and deionized water for 10 minutes each, and dry it with nitrogen gas after cleaning.

[0057] A 1μm thick layer of AZ5200 photoresist was spin-coated at 100℃. After pre-baking for 60 seconds, the photoresist was covered with a mask containing a circular aperture array. Exposure was performed using a UV lithography machine for 5 seconds. After exposure, the mask was removed, resulting in multiple circular apertures with a diameter of 2μm, forming a circular aperture array photoresist film. The gallium nitride substrate and the photoresist film were then silver-plated to a thickness of 300nm. The photoresist film was then peeled off from the gallium nitride substrate to obtain multiple silver disks with a diameter of 2μm and a thickness of 300nm. These silver disks formed a silver disk array.

[0058] Step 2: Perform rapid annealing on substrate 1, rapidly heating it at a rate of 10℃~100℃ per second, annealing it at 1000℃ for 30 seconds, so that the silver disk melts and condenses into silver microspheres, and multiple silver microspheres form a silver microsphere array. The silver microsphere array is then cooled to room temperature by natural cooling or rapid cooling.

[0059] Step 3: The substrate with the silver microsphere array obtained in Step 2 is subjected to inductively coupled plasma etching. The etching gas is chlorine gas with a flow rate of 15 sccm. After etching for 15 min, hydrochloric acid is used for acid washing to finally obtain an ordered gallium nitride nanolens array.

[0060] Example 4

[0061] Step 1: Clean the diamond substrate with hydrochloric acid, then ultrasonically clean it with acetone, isopropanol and deionized water for 10 minutes each, and dry it with nitrogen gas after cleaning.

[0062] A 1μm thick layer of AZ5200 photoresist was spin-coated at 100℃. After pre-baking for 60 seconds, the photoresist was covered with a mask containing a circular aperture array. Exposure was performed using a UV lithography machine for 5 seconds. After exposure, the mask was removed, resulting in multiple circular apertures with a diameter of 2μm, forming a circular aperture array photoresist film. Silver plating with a thickness of 100nm was then applied to the diamond substrate and the photoresist film. The photoresist film was then peeled off from the diamond substrate to obtain a silver disk array with a diameter of 2μm and a thickness of 300nm.

[0063] Step 2: Perform rapid annealing on the silver disk array on the diamond substrate. The temperature is rapidly increased at a rate of 10℃ to 100℃ per second, and the annealing temperature is 1000℃. The temperature is held for 30 seconds, which causes the silver disks to melt and condense into silver spheres. Multiple silver spheres form a silver sphere array. The silver sphere array is then cooled to room temperature by natural cooling or rapid cooling.

[0064] Step 3: The diamond substrate with the silver microsphere array obtained in Step 2 is subjected to inductively coupled plasma etching. The etching gases are chlorine, oxygen and argon, and the gas flow rate is 15 sccm. After etching for 15 min, hydrochloric acid is used for acid washing to finally obtain an ordered diamond nanolens array.

[0065] Example 5

[0066] Step 1: First clean a 3×3mm area with aqua regia. 2 The diamond substrate was then ultrasonically cleaned for 10 minutes each with acetone, isopropanol, and deionized water, and then dried with nitrogen gas.

[0067] A 3μm thick layer of SPR220 photoresist was spin-coated at 90℃. After pre-baking for 90 seconds, the photoresist was covered with a mask containing a circular aperture array. Exposure was performed using a UV lithography machine for 8 seconds. After exposure, the mask was removed, resulting in multiple 3μm diameter circular apertures, forming a circular aperture array photoresist film. Gold plating with a thickness of 300nm was then applied to the diamond substrate and the photoresist film. The photoresist film was then peeled off from the diamond substrate to obtain gold disks with a diameter of 3μm and a thickness of 300nm. Multiple gold disks formed a gold disk array.

[0068] Step 2: Perform rapid annealing on the gold disk array on the diamond substrate. The temperature is rapidly increased at a rate of 10℃ to 100℃ per second, and the annealing temperature is 1200℃. The temperature is held for 30 seconds, which causes the gold disks to melt and condense into gold microspheres. Multiple gold microspheres form a gold microsphere array. The gold microsphere array is then cooled to room temperature by natural cooling or rapid cooling.

[0069] Step 3: The diamond substrate with the gold microsphere array obtained in Step 2 is subjected to inductively coupled plasma etching. The etching gases are argon and oxygen, and the gas flow rates are argon 5 sccm and oxygen 15 sccm. After etching for 5 minutes, it is subjected to aqua regia washing treatment. Finally, an ordered diamond nanolens array is obtained.

[0070] Example 6

[0071] Step 1: Clean the 10×10mm area with aqua regia. 2 The diamond substrate was then ultrasonically cleaned for 10 minutes each with acetone, isopropanol, and deionized water, and then dried with nitrogen gas.

[0072] A 5μm thick layer of AZ5214 photoresist was spin-coated at 100℃. After pre-baking for 90 seconds, the photoresist was covered with a mask containing a circular aperture array. Exposure was performed using a UV lithography machine for 5 seconds. After exposure, the mask was removed, resulting in multiple 1μm diameter circular apertures, forming a circular aperture array photoresist film. Gold plating with a thickness of 200nm was applied to both the diamond substrate and the photoresist film. The photoresist film was then peeled off from the diamond substrate to obtain gold disks with a diameter of 1μm and a thickness of 200nm. Multiple gold disks formed a gold disk array, arranged in a close-packed configuration.

[0073] Step 2: Perform rapid annealing on the gold disk array on the diamond substrate. The temperature is rapidly increased at a rate of 10℃ to 100℃ per second, and the annealing temperature is 1100℃. The temperature is held for 30 seconds, which causes the gold disks to melt and condense into gold microspheres. Multiple gold microspheres form a gold microsphere array. The gold microsphere array is then cooled to room temperature by natural cooling or rapid cooling.

[0074] Step 3: The substrate with the gold microsphere array obtained in Step 2 is subjected to inductively coupled plasma etching. The etching gas is oxygen, the gas flow rate is 15 sccm, and the etching time is 3 minutes. After etching, it is subjected to aqua regia washing treatment to finally obtain an ordered diamond nanolens array.

[0075] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for fabricating a nano-lens array, characterized by, The method comprises the following steps: coating photoresist on one surface of a substrate, shielding the photoresist with a mask plate having a circular hole array, and then exposing and developing the photoresist to obtain a photoresist film having a circular hole array on the substrate; the substrate is made of diamond, gallium nitride or silicon carbide; plating a metal layer on the substrate having the photoresist film with a circular hole array; stripping the photoresist film from the substrate to obtain a metal disc array; annealing the substrate having the metal disc array to melt and condense the metal disc array into a metal sphere array, which serves as an etching mask of the substrate; the diameter of each metal disc in the metal disc array is 0.5-5 μm; dry etching the substrate having the metal sphere array to obtain a nano-lens array; in the annealing process of the substrate having the metal disc array, the substrate is arranged in an inclined manner.

2. The production method according to claim 1, characterized by, The method further comprises, before the step of coating photoresist on one surface of a substrate: acid pickling the surface of the substrate to remove impurities on the surface of the substrate.

3. The production method according to claim 2, characterized by, The inclination angle of the substrate is less than 30°.

4. The method of claim 1, wherein, The annealing process of the substrate having the metal disc array is performed in a vacuum environment or in an inert gas or atmospheric atmosphere.

5. The preparation method according to claim 1, characterized in that, The method further comprises, after the step of dry etching the substrate having the metal sphere array: acid pickling the substrate after dry etching to remove residual metal and other impurities.

6. The method of claim 1, wherein, The thickness of the metal layer is 5-500 nm.

7. A nano-lens array, characterized by, The nano-lens array is prepared by the method according to any one of claims 1-6, and the spacing of each nano-lens in the nano-lens array is the same and is 0.5-50 μm.

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