Multilevel micro-nano structure, preparation method and application thereof

Abstract

The application provides a multistage micro-nano structure and a preparation method and application thereof, and comprises the following steps: (1) preparing a sacrificial layer on the surface of an initial substrate; (2) preparing a multilayer electron beam resist on the surface of the sacrificial layer, wherein the sensitivities of adjacent two layers of the electron beam resist are different; (3) performing electron beam exposure, development and fixation on the multilayer electron beam resist to obtain a multistage micro-nano resist structure, wherein the exposure patterns and exposure doses of adjacent two layers of the electron beam resist are different; (4) filling the multistage micro-nano resist structure and forming a thin film on the top layer of the multistage micro-nano resist structure; (5) removing the sacrificial layer, turning over and transferring the part above the sacrificial layer upside down to a target substrate, removing the residual electron beam resist, and optionally removing the thin film to obtain the multistage micro-nano structure. The method of the application only needs one-time exposure and thin film deposition, and the prepared multistage micro-nano structure has wide application prospects in the fields of microfluidic devices, optoelectronic devices and the like.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano fabrication technology. Specifically, this invention relates to a multi-level micro-nano structure, its fabrication method, and its applications. Background Technology

[0002] Micro- and nanostructures, due to their unique optical and electrical properties, have been widely applied in fields such as surface plasmon resonance (SPR), biomedical detection, microfluidic devices, mechanical devices, and optoelectronic devices. The fabrication of conventional micro- and nanostructures typically requires equipment such as electron beam lithography (EBL), laser direct writing, two-photon lithography, focused ion beam (FIB), or plasma etching; however, this usually only produces conventional structures with uniform height.

[0003] Multilevel micro- and nanostructures, with each level's shape and size individually controllable, offer additional degrees of freedom due to the increased controllable level. This allows for more convenient and multi-dimensional adjustment of the structure's morphology and performance parameters, thus enhancing their application prospects in various fields. However, multilevel micro- and nanostructures remain difficult to fabricate, typically requiring multiple overlay processes. This not only presents challenges such as long processing cycles, poor alignment accuracy, and difficulties in fabrication due to multiple complex processes, but also prevents arbitrary control of the multilevel structure and materials. Summary of the Invention

[0004] To overcome the problems of long process cycles, poor alignment accuracy, complex processes, and the inability to arbitrarily control the multi-level structure and materials in existing multi-level micro / nanostructure technologies, this invention provides a method for fabricating multi-level micro / nanostructures. This method features a simple fabrication process requiring only one exposure and thin film deposition, and the shape, material, and number of each level are controllable. Furthermore, this invention also provides the multi-level micro / nanostructures fabricated by the above method and their application areas.

[0005] The above-mentioned objective of the present invention is achieved by providing the following technical solution.

[0006] In a first aspect, the present invention provides a method for preparing hierarchical micro / nano structures, comprising the following steps:

[0007] (1) Prepare a sacrificial layer on the surface of the initial substrate;

[0008] (2) A multilayer electron beam resist is prepared on the surface of the sacrificial layer, wherein the sensitivity of two adjacent electron beam resist layers is different;

[0009] (3) Electron beam exposure, development and fixing are performed on the multilayer electron beam resist to obtain a multi-level micro-nano resist structure, wherein the exposure pattern and exposure dose of two adjacent electron beam resist layers are different.

[0010] (4) Deposit one or more thin films by atomic layer deposition (ALD) to fill the multi-level micro-nano resist structure, and form a thin film on the top layer of the multi-level micro-nano resist structure to obtain an intermediate product;

[0011] (5) Remove the sacrificial layer of the intermediate product, flip the portion of the intermediate product above the sacrificial layer and transfer it to the target substrate, remove the residual electron beam resist, and optionally remove part or all of the film that has been flipped to the bottom layer to obtain the multi-level micro-nano structure.

[0012] In this invention, the term "multilayer" refers to at least two layers, preferably two to five layers.

[0013] In this invention, the term "multi-level" refers to at least 2 levels, preferably 2-5 levels.

[0014] In this invention, the number of levels of the multi-level micro / nano structure corresponds to the number of layers of the multilayer electron beam resist, and the first level of the micro / nano structure corresponds to one layer of the electron beam resist.

[0015] In this invention, the term "first level" refers to the multi-level micro / nano resist structure or the level in the multi-level micro / nano structure that is furthest from the initial substrate (or target substrate). In the multi-level micro / nano structure and multi-level micro / nano resist structure of this invention, starting from the first level, along the direction from the first level to the level closest to the initial substrate (or target substrate), each level of the micro / nano resist structure or each level of the micro / nano structure is sequentially referred to as the first level, the second level, ..., the nth level, where n is an integer greater than or equal to 2.

[0016] In this invention, the term "sensitivity of electron beam photoresist" refers to the energy of the electron beam required for the electron beam photoresist to undergo cross-linking or degradation reactions. The term "different sensitivities" refers to the different degrees of exposure of different electron beam photoresists under the same exposure dose. For example, under the same exposure dose, a photoresist with high sensitivity is completely exposed and undergoes sufficient cross-linking or degradation reactions, thus being dissolved by the developer, while a photoresist with low sensitivity undergoes almost no cross-linking or degradation reactions and is therefore unaffected by the developer.

[0017] The inventors of this invention unexpectedly discovered that by preparing multiple layers of electron beam resists with different sensitivities on the surface of the sacrificial layer, and prioritizing the exposure of the highly sensitive resist at the same location during exposure, while exposing the less sensitive resist later, a multi-level structure can be prepared at the same location. Thus, a multi-level micro / nano resist structure can be obtained with only one exposure. Using the multi-level micro / nano resist structure as a template, a controllable multi-level micro / nano structure can be obtained through a single thin film deposition. Moreover, the shape, material, and number of levels of the multi-level micro / nano structure are controllable, overcoming the problems of long process cycles, poor alignment accuracy, complex processes, and the inability to arbitrarily control the multi-level structure and materials in existing multi-level micro / nano structures.

[0018] Preferably, in the method described in this invention, in step (1), the initial substrate is a rigid substrate.

[0019] Preferably, in the method described in this invention, in step (1), the rigid substrate is at least one of silicon wafer, quartz and sapphire.

[0020] Preferably, in the method described in this invention, in step (1), the thickness of the sacrificial layer is 20-200 nm.

[0021] Preferably, in the method described in this invention, in step (1), the sacrificial layer is at least one of a water-soluble conductive adhesive layer, a SiO2 layer, and a metal layer.

[0022] Preferably, in the method described in this invention, in step (1), the metal layer is an aluminum layer and / or a chromium layer.

[0023] Preferably, in the method of the present invention, in step (2), the electron beam resist is selected from at least one of methacrylic acid (MAA), polymethyl methacrylate (PMMA), a copolymer of α-chloromethacrylate and α-methylstyrene (ZEP520).

[0024] Preferably, in the method described in this invention, in step (2), the thickness of any layer of electron beam resist is 100-1500 nm, preferably 100-500 nm.

[0025] Preferably, in the method described in this invention, in step (3), the electron beam exposure is performed under the following conditions: the exposure voltage is 10-100 keV, the aperture is 5-50 μm, and the exposure dose of any layer of electron beam resist is 50-1500 μC / cm. 2 Unrestricted by any theory, the exposure dose is affected by the required structural height; the higher the required structural height, the greater the exposure dose.

[0026] Preferably, in the method described in this invention, in step (3), the size of the exposed pattern is 50-5000 nm.

[0027] In this invention, the term "size" refers to the fixed dimensions of an exposed pattern other than its height, such as length, width, or diameter.

[0028] Preferably, in the method of the present invention, in step (3), the developing solution used in the developing process is compatible with the type of electron beam resist. For example, PMMA and MMA electron beam resists both use methyl isobutyl ketone (MIBK):isopropanol (IPA) in a volume ratio of 1:3 as the developing solution, while ZEP520 electron beam resist uses butyl acetate as the developing solution.

[0029] Preferably, in the method described in this invention, in step (3), the fixing solution used during the fixing process is compatible with the type of electron beam resist. For example, PMMA electron beam resist and ZEP520 electron beam resist use IPA as the fixing solution.

[0030] Preferably, in the method of the present invention, in step (4), the deposition of one or more thin films is carried out at a temperature less than or equal to the glass transition temperature of any of the electron beam resists; preferably, the deposition of one or more thin films is carried out at a temperature of 80-120°C.

[0031] Preferably, in the method described in this invention, in step (4), the thickness of each of the deposited one or more thin films is 10-500 nm.

[0032] Preferably, in the method described in this invention, in step (4), the thin film is formed of an oxide.

[0033] Preferably, in the method described in this invention, in step (4), the oxide is at least one of titanium oxide, aluminum oxide, and hafnium oxide.

[0034] Preferably, in the method of the present invention, in step (5), the removal of the sacrificial layer of the intermediate product is carried out by a method including the following steps: placing the intermediate product in a sacrificial layer dissolving solution to separate the initial substrate and the portion above the sacrificial layer in the intermediate product.

[0035] Preferably, in the method described in this invention, in step (5), the sacrificial layer dissolving solution is at least one of water, buffer oxide etching solution (BOE solution), and metal etching solution.

[0036] Preferably, in the method described in this invention, in step (5), the target substrate is a rigid substrate or a flexible substrate.

[0037] Preferably, in the method described in this invention, in step (5), the rigid substrate is one of silicon wafer, quartz and sapphire.

[0038] Preferably, in the method described in this invention, in step (5), the flexible substrate is one of polyimide film, polydimethylsiloxane (PDMS) film, and fiber cloth.

[0039] Preferably, in the method of the present invention, in step (5), the removal of residual electron beam resist is carried out by oxygen plasma method and / or ozone oxidation method.

[0040] Preferably, in the method described in this invention, in step (5), the removal of part or all of the thin film flipped to the bottom layer is performed by inductively coupled plasma etching.

[0041] Preferably, in the method described in this invention, in step (5), the etching is performed under the following conditions:

[0042] The flow rate of CHF3 is 10-50 sccm or the flow rate of Cl2 is 2-20 sccm;

[0043] Ar gas flow rate is 2-20 sccm;

[0044] RF power is 10-200W;

[0045] ICP power is 400-1500W;

[0046] Etching pressure is 5-100 mTorr;

[0047] The etching temperature is 20-60℃;

[0048] The etching time is 10-200 seconds.

[0049] Preferably, in the method described in this invention, the method further includes the following step: before step (1), the initial substrate is subjected to surface cleaning treatment.

[0050] Preferably, in the method described in this invention, the cleaning process is performed by a method comprising the following steps: ultrasonically cleaning the initial substrate sequentially with acetone, isopropanol and deionized water, and then drying it.

[0051] Secondly, the present invention provides a multi-level micro / nano structure prepared by the method described in the first aspect.

[0052] Preferably, in the multi-level micro / nano structure described in this invention, the height of any level of micro / nano structure is 50-1000 nm.

[0053] Thirdly, the present invention provides an application of the multi-level micro / nano structure described in the second aspect in surface plasmon resonance, biomedical detection, microfluidic devices, mechanical devices, and optoelectronic devices.

[0054] The present invention has the following beneficial effects:

[0055] This invention prepares multiple electron beam resists with different sensitivities on the surface of the sacrificial layer. During exposure, the highly sensitive resist at the same location is exposed first, and the less sensitive resist is exposed later, thus achieving the preparation of a multi-level structure at the same location. Therefore, a multi-level micro / nano resist structure can be obtained with only one exposure. Using the multi-level micro / nano resist structure as a template, a controllable multi-level micro / nano structure can be obtained through a single thin film deposition. Moreover, the shape, material, and number of levels of the multi-level micro / nano structure are controllable, overcoming the problems of long process cycles, poor alignment accuracy, complex processes, and the inability to arbitrarily control the multi-level structure and materials in existing multi-level micro / nano structures.

[0056] This invention deposits one or more thin films on a fixed product using atomic layer deposition. This method has better filling effect, can adapt to various shapes of different levels, and allows the grown film to extend to any position of each level, thereby realizing the preparation of various levels with different shapes and sizes.

[0057] The multi-level micro / nano structures prepared by this invention have broad application prospects in the fields of surface plasmon resonance, biomedical detection, microfluidic devices, mechanical devices, and optoelectronic devices. Attached Figure Description

[0058] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein:

[0059] Figure 1 This is a scanning electron microscope image of the two-stage "stool"-shaped TiO2 micro / nano structure prepared in Example 1 of this invention;

[0060] Figure 2 This is a scanning electron microscope image of the three-level "cage"-shaped Al2O3 micro / nano structure obtained in Example 2 of this invention;

[0061] Figure 3 This is a scanning electron microscope image of the three-level "basket"-shaped HfO2 micro / nano structure prepared in Example 3 of this invention;

[0062] Figure 4 These are scanning electron microscope images of the three-level and five-level composite TiO2 micro / nano structures prepared in Example 4 of this invention;

[0063] Figure 5 This is a scanning electron microscope image of the three-level "dumbbell" shaped Al2O3 micro / nano structure obtained in Example 5 of this invention. Detailed Implementation

[0064] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0065] Example 1

[0066] This embodiment illustrates the method for preparing a two-stage "stool"-shaped TiO2 micro / nano structure according to the present invention.

[0067] Step 1: Clean the silicon wafer sequentially with acetone, isopropanol and deionized water using ultrasonic cleaning for 5 minutes each time. After cleaning, dry it with a nitrogen gun.

[0068] Step 2: Coat the silicon wafer surface with a 100nm thick layer of water-soluble conductive adhesive as a sacrificial layer;

[0069] Step 3: Spin-coat MAA / PMMA electron beam resists with different sensitivities sequentially onto the surface of the sacrificial layer, with thicknesses of 100nm and 400nm respectively, and bake after spin-coating; wherein, the glass transition temperature of both MAA and PMMA is above 120℃;

[0070] Step 4: Electron beam exposure of the MAA / PMMA electron beam resist, wherein the exposure voltage is 100 keV, the aperture is 25 μm, the first stage (the top of the "stool") is circular with a diameter of 2000 nm, and the exposure dose is 250 μC / cm. 2 The second stage (the "stool" legs) is a square with a side length of 100nm, and the exposure dose is 700μC / cm. 2 After exposure, it is placed in a developer solution with a volume ratio of MIBK:IPA of 1:3 for development, and then fixed with IPA to obtain a two-stage cavity resist structure.

[0071] Step 5: A multilayer TiO2 film is deposited by ALD to fill the two-stage cavity resist structure, and a TiO2 film is formed on the top layer of the two-stage cavity resist structure to obtain the intermediate product; wherein, the deposition temperature is 90℃ and the thickness of each TiO2 film is 50nm;

[0072] Step 6: Place the intermediate product in water to dissolve the sacrificial layer, separate the portion above the sacrificial layer from the silicon wafer and the intermediate product, flip the portion above the sacrificial layer over and transfer it to the target silicon wafer, and then dry it at 40°C. After drying, use an oxygen plasma stripper to remove the residual electron beam resist, and then use inductively coupled plasma etching to remove the TiO2 film that has been flipped to the bottom layer, obtaining the TiO2 micro / nano structure. The etching is performed under the following conditions: CHF3 flow rate of 30 sccm, Ar gas flow rate of 5 sccm, RF power of 100W, ICP power of 1000W, etching pressure of 20 mTorr, etching temperature of 20°C, and etching time of 35 s.

[0073] The TiO2 micro / nano structure prepared in this embodiment is as follows: Figure 1 As shown, it is a two-stage "stool" shape, with the first stage being larger than the second stage. The height of the first stage is 150 nm, and the height of the second stage is 400 nm. This embodiment achieves independent control of the structure and size of the two-stage structure.

[0074] Example 2

[0075] This embodiment illustrates the method for preparing a three-level "cage"-shaped Al2O3 micro / nano structure according to the present invention.

[0076] Step 1: Clean the quartz substrate sequentially with acetone, isopropanol and deionized water using ultrasonic cleaning for 5 minutes each time, and then dry it with a nitrogen gun.

[0077] Step 2: Grow a 100nm thick SiO2 layer on the surface of the quartz substrate as a sacrificial layer;

[0078] Step 3: Spin-coat the surface of the sacrificial layer with different sensitivities of MAA / PMMA / MAA electron beam resist, with thicknesses of 100nm, 400nm and 100nm respectively, and bake after spin-coating;

[0079] Step 4: Electron beam exposure of the MAA / PMMA / MAA electron beam resist, wherein the exposure voltage is 100 keV, the aperture is 25 μm, the first stage (the top of the "cage") is a 100×600 nm rectangle, and the exposure dose is 200 μC / cm. 2 The second stage (the middle part of the "cage") is a 100×100nm square with an exposure dose of 600μC / cm. 2 The third stage (the bottom of the "cage") is a rectangle of 100×600nm, with an exposure dose of 200μC / cm. 2 After exposure, it is placed in a developer solution with a volume ratio of MIBK:IPA of 1:3 for development, and then fixed with IPA to obtain a three-level cavity resist structure.

[0080] Step 5: A multilayer Al2O3 film is deposited by ALD to fill the tertiary cavity resist structure, and an Al2O3 film is formed on the top layer of the tertiary cavity resist structure to obtain the intermediate product; wherein, the deposition temperature is 80℃ and the thickness of each Al2O3 film is 100nm;

[0081] Step 6: Place the intermediate product in BOE solution to dissolve the sacrificial layer, separate the quartz substrate and the portion above the sacrificial layer in the intermediate product, flip the portion above the sacrificial layer over and transfer it to the sapphire substrate (target substrate), and then dry it at 40°C. After drying, use ozone to remove the residual electron beam resist, and then use inductively coupled plasma etching to remove the Al2O3 film that has been flipped to the bottom layer to obtain the Al2O3 micro / nano structure. The etching is performed under the following conditions: Cl2 flow rate of 10 sccm, Ar gas flow rate of 5 sccm, RF power of 100W, ICP power of 800W, etching pressure of 10 mTorr, etching temperature of 20°C, and etching time of 60s.

[0082] The Al2O3 micro / nano structure prepared in this embodiment is as follows: Figure 2 As shown, it is a three-tiered "cage" structure, symmetrical in the height direction. The height of the first tier is 100 nm, the height of the second tier (column height) is 250 nm, and the height of the third tier is 100 nm. This embodiment achieves joint control of the three-tiered structure in terms of both structure and size.

[0083] Example 3

[0084] This embodiment illustrates the method for preparing a three-level "basket"-shaped HfO2 micro / nano structure according to the present invention.

[0085] Step 1: Clean the quartz substrate sequentially with acetone, isopropanol and deionized water using ultrasonic cleaning for 5 minutes each time, and then dry it with a nitrogen gun.

[0086] Step 2: Grow a 100nm thick aluminum film on the surface of a quartz substrate as a sacrificial layer;

[0087] Step 3: Spin-coat the surface of the sacrificial layer with different sensitivities of MAA / PMMA / MAA electron beam resist, with thicknesses of 100nm, 400nm and 100nm respectively;

[0088] Step 4: Electron beam exposure of the MAA / PMMA / MAA electron beam resist. The exposure voltage is 50 keV, the aperture is 25 μm, and the first stage (the top of the "basket") is a cross pattern composed of rectangles of varying lengths with a width of 100 nm. There is no pattern at the center of the first stage. The exposure dose is 200 μC / cm². 2The second stage (the middle part of the "basket") is a 100×100nm square with an exposure dose of 600μC / cm. 2 The third level (the bottom of the "basket") consists of rectangles of varying lengths with a width of 100 nm, and the exposure dose is 200 μC / cm². 2 After exposure, it is placed in a developer solution with a volume ratio of MIBK:IPA of 1:3 for development, and then fixed with IPA to obtain a three-level cavity resist structure.

[0089] Step 5: A multilayer HfO2 film is deposited by ALD to fill the tertiary cavity resist structure, and an HfO2 film is formed on the top layer of the tertiary cavity resist structure to obtain the intermediate product; wherein, the deposition temperature is 120℃ and the thickness of each HfO2 film is 100nm;

[0090] Step 6: Place the intermediate product in tetramethylammonium hydroxide (TMAH) to dissolve the aluminum film used as a sacrificial layer, separate the quartz substrate and the part above the sacrificial layer in the intermediate product, flip the part above the sacrificial layer upside down and transfer it to the target quartz substrate, and then dry it at 40°C. After drying, use an oxygen plasma desizing machine to remove the residual electron beam resist to obtain the HfO2 micro / nano structure.

[0091] The HfO2 micro / nano structure prepared in this embodiment is as follows: Figure 3 As shown, it is a three-tiered "basket" shape, and asymmetrical in the height direction. The height of the first tier is 70 nm, the height of the second tier (pillar height) is 250 nm, and the height of the third tier is 100 nm. Through this embodiment, independent control of the structure and size of the three-tiered structure is achieved.

[0092] Example 4

[0093] This embodiment illustrates the method for preparing tertiary and quinary composite TiO2 micro / nano structures according to the present invention.

[0094] Step 1: Clean the quartz substrate sequentially with acetone, isopropanol and deionized water using ultrasonic cleaning for 5 minutes each time, and then dry it with a nitrogen gun.

[0095] Step 2: Coat the surface of the first quartz substrate with a 100nm thick layer of water-soluble conductive adhesive as a sacrificial layer;

[0096] Step 3: Spin-coat the surface of the sacrificial layer with different sensitivities of MAA / PMMA / MAA / PMMA / MAA electron beam resist, with thicknesses of 100nm, 300nm, 100nm, 300nm and 100nm respectively;

[0097] Step 4: Electron beam exposure is performed on the MAA / PMMA / MAA / PMMA / MAA electron beam resist. The exposure voltage is 50 keV and the aperture is 25 μm. For the three-level structure, exposure is performed as in Example 3. For the five-level structure, the exposure dose for the first, third, and fifth levels is 150 μC / cm. 2 The exposure dose for levels two and four is 500 μC / cm. 2 Each layer uses rectangles of different sizes. After exposure, they are placed in a developer solution with a volume ratio of MIBK:IPA of 1:3 for development. Then, IPA is used for fixing to obtain three-level and five-level cavity resist structures.

[0098] Step 5: A multilayer TiO2 film is deposited by ALD to fill the tertiary and quinary cavity resist structures, and a TiO2 film is formed on the top layer of the tertiary and quinary cavity resist structures to obtain the intermediate product; wherein, the deposition temperature is 105℃ and the thickness of each TiO2 film is 100nm;

[0099] Step 6: The intermediate product is placed in water to dissolve the sacrificial layer, separating the quartz substrate and the portion above the sacrificial layer in the intermediate product. The portion above the sacrificial layer is flipped over and transferred to the target quartz substrate, then dried at 40°C. After drying, oxygen plasma is used to remove the residual electron beam resist, and then inductively coupled plasma etching is used to remove the TiO2 film that has been flipped to the bottom layer, obtaining the TiO2 micro / nano structure. The etching is performed under the following conditions: CHF3 flow rate of 30 sccm, Ar gas flow rate of 5 sccm, etching power of 100 W, ICP power of 1000 W, etching pressure of 20 mTorr, etching temperature of 20°C, and etching time of 35 s.

[0100] The TiO2 micro / nano structure prepared in this embodiment is as follows: Figure 4 As shown, it is a three-level and five-level composite TiO2 micro / nano structure array, wherein the height of the first, third, and fifth levels is 80 nm, and the height of the second and fourth levels is 150 nm. Through this embodiment, not only were structures with different levels fabricated simultaneously, but also independent control over the number of levels, structure, and size was achieved.

[0101] Example 5

[0102] This embodiment illustrates the method for preparing a three-level "dumbbell" shaped Al2O3 micro / nano structure according to the present invention.

[0103] Step 1: Clean the quartz substrate sequentially with acetone, isopropanol and deionized water using ultrasonic cleaning for 5 minutes each time, and then dry it with a nitrogen gun.

[0104] Step 2: Grow a 100nm thick SiO2 layer on the surface of the quartz substrate as a sacrificial layer;

[0105] Step 3: Spin-coat the surface of the sacrificial layer with ZEP520A / PMMA / ZEP520A electron beam resists of different sensitivities in sequence, with thicknesses of 100nm, 400nm and 100nm respectively, and bake after spin-coating; among them, the glass transition temperature of ZEP520A, MAA and PMMA are all above 120℃.

[0106] Step 4: Electron beam exposure is performed on ZEP520A / PMMA / ZEP520A electron beam resist. The exposure voltage is 100 keV, the aperture is 25 μm, the first stage (the top of the "dumbbell") is a 400×400 nm rectangle, and the exposure dose is 200 μC / cm. 2 The second stage (the middle part of the "dumbbell") is a 100×100nm square with an exposure dose of 600μC / cm. 2 The third stage (the bottom of the "dumbbell") is a 400×400nm rectangle with an exposure dose of 200μC / cm. 2 After exposure, the first stage ZEP520 resist is developed in butyl acetate, then the second stage PMMA resist is developed in a developer solution with a volume ratio of MIBK:IPA of 1:3, then the third stage ZEP520 resist is developed in butyl acetate, and finally fixed with IPA to obtain a three-stage cavity resist structure.

[0107] Step 5: A multilayer Al2O3 film is deposited by ALD to fill the tertiary cavity resist structure, and an Al2O3 film is formed on the top layer of the tertiary cavity resist structure to obtain the intermediate product; wherein, the deposition temperature is 80℃ and the thickness of each Al2O3 film is 100nm;

[0108] Step 6: Place the intermediate product in BOE solution to dissolve the sacrificial layer, separate the quartz substrate and the portion above the sacrificial layer in the intermediate product, flip the portion above the sacrificial layer over and transfer it to the sapphire substrate (target substrate), and then dry it at 40°C. After drying, use ozone to remove the residual electron beam resist, and then use inductively coupled plasma etching to remove the Al2O3 film that has been flipped to the bottom layer to obtain the Al2O3 micro / nano structure. The etching is performed under the following conditions: Cl2 flow rate of 10 sccm, Ar gas flow rate of 5 sccm, RF power of 100W, ICP power of 800W, etching pressure of 10 mTorr, etching temperature of 20°C, and etching time of 60s.

[0109] The Al2O3 micro / nano structure prepared in this embodiment is as follows: Figure 5As shown, it is a three-stage "dumbbell" shape, with the first stage having a height of 80 nm, the second stage (column height) having a height of 250 nm, and the third stage having a height of 150 nm. This embodiment achieves joint control over the structure and dimensions of the three-stage structure.

[0110] The embodiments described above are merely examples illustrating several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing hierarchical micro / nano structures, comprising the following steps: (1) Prepare a sacrificial layer on the substrate surface; (2) A multilayer electron beam resist is prepared on the surface of the sacrificial layer, wherein the sensitivity of two adjacent electron beam resist layers is different; (3) Electron beam exposure, development and fixing are performed on the multilayer electron beam resist to obtain a multi-level micro-nano resist structure, wherein the exposure pattern and exposure dose of two adjacent electron beam resist layers are different; (4) The multi-level micro-nano resist structure obtained in step (3) is filled by depositing a thin film by atomic layer deposition and forming a thin film on the surface of its multi-layer electron beam resist; (5) Remove the sacrificial layer of the multi-level micro-nano resist structure obtained in step (4), then flip the part above the sacrificial layer up and down and transfer it to the target substrate, remove the remaining electron beam resist, and do not remove or remove part or all of the film that has been flipped to the bottom to obtain the multi-level micro-nano structure. In step (3), the electron beam exposure is performed under the following conditions: exposure voltage of 10-100 KeV, aperture of 5-50 μm, and exposure dose of any layer of electron beam resist of 50-1500 μC / cm. 2 .

2. The method according to claim 1, wherein, In step (1), the substrate is a rigid substrate.

3. The method according to claim 2, wherein, The rigid substrate is at least one of silicon wafer, quartz, and sapphire.

4. The method according to claim 1, wherein, In step (1), the thickness of the sacrificial layer is 20-200 nm; and / or The sacrificial layer is at least one of a water-soluble conductive adhesive layer, a SiO2 layer, and a metal layer.

5. The method according to claim 4, wherein, The metal layer is an aluminum layer and / or a chromium layer.

6. The method according to claim 1, wherein, In step (2), the electron beam resist is at least one of MAA, PMMA, and ZEP520; and / or The thickness of any single electron beam resist layer is 100-1500 nm.

7. The method according to claim 6, wherein, The thickness of any one layer of electron beam resist is 100-500 nm.

8. The method according to claim 1, wherein, The size of the exposed pattern is 50-5000 nm.

9. The method according to claim 1, wherein, In step (4), the deposition of the thin film is carried out at a temperature less than or equal to the glass transition temperature of any of the electron beam resists; and / or The thin film is formed of oxide.

10. The method according to claim 9, wherein, The deposition of the thin film is carried out at a temperature of 80-120°C.

11. The method according to claim 9, wherein, The oxide is at least one of titanium oxide, aluminum oxide, and hafnium oxide.

12. The method according to claim 1, wherein, In step (5), the removal of the sacrificial layer of the multi-level micro / nano resist structure obtained in step (4) is performed by a method comprising the following steps: placing the multi-level micro / nano resist structure obtained in step (4) in a sacrificial layer dissolving solution to separate the substrate and the portion of the multi-level micro / nano resist structure above the sacrificial layer; and / or The target substrate can be a rigid substrate or a flexible substrate.

13. The method according to claim 12, wherein, The sacrificial layer dissolving solution is at least one of water, BOE solution, and metal corrosion solution.

14. The method according to claim 12, wherein, The rigid substrate is one of silicon wafer, quartz, and sapphire; and / or The flexible substrate is one of polyimide film, PDMS film, and fiber cloth.

15. The method according to claim 1, wherein, In step (5), the removal of the remaining electron beam resist is carried out by oxygen plasma method and / or ozone oxidation method; and / or The removal of the film, which is partially or completely flipped to the bottom, is performed by inductively coupled plasma etching.

16. The method according to claim 15, wherein, The etching is performed under the following conditions: The flow rate of CHF3 is 10-50 sccm or the flow rate of Cl2 is 2-20 sccm; Ar gas flow rate is 2-20 sccm; RF power is 10-200 W; ICP power is 400-1500 W; Etching pressure is 5-100 mTorr; The etching temperature is 20-60℃; The etching time is 10-200 s.

17. The method according to any one of claims 1 to 16, wherein, The method further includes the following steps: before step (1), the substrate is subjected to surface cleaning treatment.

18. The method according to claim 17, wherein, The cleaning process is carried out by a method including the following steps: the substrate is ultrasonically cleaned sequentially with acetone, isopropanol and deionized water for 5-10 minutes, and then dried.

19. A multi-level micro / nano structure prepared by the method described in any one of claims 1-18.

20. The application of the multi-level micro / nano structure of claim 19 in surface plasmon resonance, biomedical detection, microfluidic devices, mechanical devices, and optoelectronic devices.

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