A multi-layer composite nanostructure imprinting template and a preparation method thereof

Abstract

The application relates to a kind of multilayer composite nanostructure imprinting templates and preparation methods thereof, and belongs to the technical field of micro-nano processing.The nanostructure of the template is composed of two or more layers of materials with different mechanical properties, which are rigid layer and elastic layer, or rigid layer, buffer layer and elastic layer, or the alternating structure of rigid layer, buffer layer and elastic layer.The multilayer composite nanostructure imprinting template of the application can imprint high-aspect-ratio nanostructures and effectively avoid defects such as deformation and damage of high-aspect-ratio nanostructures during the nanoimprint demolding process.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano fabrication technology, specifically a multilayer composite nanostructure imprint template and its preparation method. Background Technology

[0002] Nanoimprint lithography, invented in 1995 by Professor S.C. Chou of Princeton University, addresses the bottleneck in photolithography at the time, which struggled to achieve patterns smaller than 100 nanometers. It is a method for fabricating micro- and nanostructures and has seen significant development in recent years, considered one of the most promising general-purpose micro- and nanostructure manufacturing technologies besides photolithography. Compared to other micro- and nanostructure fabrication methods such as far-infrared (extreme) ultraviolet lithography and electron / ion beam lithography, it offers advantages such as ultra-high resolution, high throughput, and low cost. Compared to photolithography, nanoimprint lithography can fabricate complex 3D nanostructures in a single step, which currently requires multiple steps in photolithography. Examples include oblique toothed gratings for augmented reality and 3D sensing grayscale binary optical devices for facial recognition.

[0003] Currently, micro / nano devices fabricated in a single step using nanoimprint lithography exhibit relatively large aspect ratios, often exceeding 1. Therefore, to obtain high-fidelity nanostructures, rigid imprinting templates are required. Flexible templates would cause deformation of the large aspect ratio nanostructures. The problem with rigid templates is that during demolding, the tightly interlocking structure on the template and the imprinted structure means that unless the separation direction of the template and substrate is perfectly parallel to the vertical direction of the micro / nano structure, the rigid contact between the rigid template nanostructure and the imprinted rigid nanostructure will cause deformation of both, leading to breakage and damage. Furthermore, atmospheric pressure makes complete parallel separation between the template and substrate extremely difficult. Demolding typically begins from the edge, creating an angle between the template and substrate, inevitably causing rigid contact between the nanostructures of the template and substrate.

[0004] On the other hand, US Patent 6180239 discloses a soft imprinting technology with flexible templates as a key technical feature, using polymethylsiloxane (PDMS) as the template material. Due to the excellent flexibility of PDMS, it does not damage itself or the imprinted structure during demolding. However, the low mechanical strength of the flexible template material used in soft imprinting technology results in low resolution and makes it difficult to obtain nanostructures with large aspect ratios. Chinese Patent 200810195525.X invented a nanoimprinting-soft imprinting composite nanoimprinting template with sub-15 nm resolution, capable of imprinting high-resolution nanostructures on curved and irregular non-planar surfaces. This template consists of an elastic support layer and a rigid structure imprinting layer, combining the high resolution of a rigid nanoimprinting template with the flexibility of a flexible soft imprinting template. The elastic support layer of this template uses polysiloxane material commonly used in soft imprinting templates, allowing the template and imprinting substrate to adhere tightly without external pressure. However, the imprinted layer structure of this template is still a rigid UV-curable material. Therefore, when imprinting structures with a large aspect ratio, the demolding process will inevitably damage the template and the imprinted nanostructure. Summary of the Invention

[0005] In view of the above, the purpose of this invention is to solve the problem of damage to the template and the imprinted nanostructure caused during the demolding process in contact patterning technologies such as nanoimprinting. This invention provides a multi-layered composite nanostructure imprinting template, wherein the template's nanostructure is composed of two or more layers of materials with different mechanical properties, namely a rigid layer and an elastic layer; or a rigid layer, a buffer layer, and an elastic layer; or an alternating structure of rigid, buffer, and elastic layers. The rigid layer ensures the high resolution and large aspect ratio of the imprinted structure; the elastic layer can undergo significant recoverable elastic deformation during demolding when the template and the imprinted nanostructure come into contact, preventing damage to the nanostructure; the modulus of the buffer layer is between that of the rigid layer and the elastic layer, and the buffer layer's function is to prevent nanostructure defects caused by stress mismatch that may occur between the elastic layer and the rigid layer materials during template preparation. Another objective of this invention is to provide a method for preparing this template.

[0006] The multilayer composite nanostructure imprint template is characterized by comprising a substrate and a nanostructure layer, wherein the nanostructure layer is composed of two or more layers of materials with different mechanical properties, including at least an elastic layer and a rigid layer. The substrate is a UV-transmitting material, made of glass, quartz, methyl methacrylate film, PET polyester film, polycarbonate film, polyimide film, polystyrene film, polysiloxane elastomer, styrene elastomer, olefin elastomer, polyurethane elastomer, diene elastomer, or vinyl chloride elastomer. The rigid layer is a UV-curable material resistant to oxygen reactive ion etching, with an elastic modulus of 100 N / mm². 2 The thickness ranges from 50 nanometers to 1 micrometer. The elastic layer is a polymeric elastomer material with an elastic modulus below 20 N / mm2, an elongation at break greater than 50%, and an adjustable thickness. The ratio of its thickness to that of the rigid layer is less than 1. The elastic layer is made of a copolymer elastomer composed of styrene, butadiene, and isoprene, a chloroprene rubber-styrene graft copolymer elastomer, an ethylene propylene rubber-styrene graft copolymer elastomer, a polyurethane elastomer, a polyester elastomer, or a polysiloxane elastomer.

[0007] The imprint template of the multilayer composite nanostructure is characterized in that the imprint template includes a substrate and at least one set of unit nanostructures composed of elastic layers and rigid layers stacked sequentially, the unit nanostructures being stacked to a set thickness.

[0008] The imprint template of the multilayer composite nanostructure is characterized in that a buffer layer is provided between the elastic layer and the rigid layer, and the imprint template includes a substrate and at least one set of unit nanostructures composed of elastic layer, buffer layer and rigid layer stacked in sequence, the unit nanostructures being stacked to a set thickness. The material of the buffer layer has a modulus of 20 N / mm². 2 ~100 N / mm 2 40 N / mm is preferred 2 ~70 N / mm 2 The elongation at break is greater than 50%, and the ratio of its thickness to the rigid layer is less than 1. The material can be a blend of rigid layer material and elastic layer material.

[0009] The imprint template of the multilayer composite nanostructure is characterized in that the imprint template includes a substrate and at least one set of unit nanostructures consisting of a rigid layer, an elastic layer and a rigid layer stacked sequentially, the unit nanostructures being stacked to a set thickness.

[0010] The imprint template of the multilayer composite nanostructure is characterized in that a buffer layer is provided between the elastic layer and the rigid layer, and the imprint template includes a substrate and at least one set of unit nanostructures composed of elastic layer, rigid layer, buffer layer and rigid layer stacked in sequence, the unit nanostructures being stacked to a set thickness. The material of the buffer layer has a modulus of 20 N / mm². 2 ~100 N / mm 2 40 N / mm is preferred 2 ~70 N / mm 2The elongation at break is greater than 50%, and the ratio of its thickness to the rigid layer is less than 1. The material can be a blend of rigid layer material and elastic layer material.

[0011] The multilayer composite nanostructure imprinting template is characterized in that the thickness of the rigid layer is between 200 nanometers and 800 nanometers, preferably between 400 nanometers and 600 nanometers.

[0012] The multilayer composite nanostructure imprint template is characterized in that the surface of the nanostructure layer is coated with a silicon dioxide coating layer with a thickness of 5-10 nanometers, and the silicon dioxide is coated by electron beam evaporation, magnetron sputtering or plasma-enhanced chemical vapor deposition.

[0013] The multilayer composite nanostructure imprint template is characterized in that a low surface energy fluorinated alkane organic small molecule layer is bonded to the surface of the silica coating layer.

[0014] The method for preparing a multilayer composite nanostructure imprint template is characterized by comprising the following steps: 1) First, an elastic layer is spin-coated onto the substrate using a spin coater, followed by a UV-curable rigid layer. The rigid layer is then imprinted and cured using a UV-curable nanoimprinting process. 2) Alternatively, first spin-coat a rigid layer onto the substrate using a spin coater, then imprint and cure the rigid layer using UV-cured nanoimprinting technology; then spin-coat an elastic layer using a spin coater. 3) The residual layer of the rigid layer is removed by fluorine-based reactive ion etching, and then the nanostructure is etched onto the substrate by oxygen reactive ion etching.

[0015] The method for preparing a multilayer composite nanostructure imprint template is characterized by comprising the following steps: 1) First, the elastic layer and the buffer layer are coated and cured on the substrate using a spin coater, and then an oxygen-resistant UV-curable rigid layer is spin-coated; then the rigid layer is imprinted and cured using a master template. 2) Fluorine-based reactive ion etching removes the residual layer of the rigid layer, and then oxygen reactive ion etching removes the buffer layer and elastic layer under the imprinted residual layer to obtain a multilayer composite nanostructure. 3) The surface of the multilayer composite nanostructure is coated with a silicon dioxide coating layer with a thickness of 5-10 nanometers by electron beam evaporation, magnetron sputtering or ion-enhanced chemical vapor deposition; 4) Finally, through a gas-phase reaction, the Si-OH groups on the silica react with perfluorotrichlorosilane to bond a layer of low surface energy fluoroalkane organic small molecules to the surface of the silica coating layer, thus obtaining the imprint template of the multilayer composite nanostructure.

[0016] This invention provides a multilayer composite nanoimprint template and its preparation method. Compared with existing technologies, it has the following advantages: The multilayer composite nanostructure imprint template of this invention uses a multilayer composite nanostructure composed of an elastic layer, a buffer layer, and a rigid layer as the imprint template. This overcomes the shortcomings of low resolution and poor fidelity in soft printing technology, and can obtain high-resolution, high-fidelity, and large aspect ratio nanostructures; its period is greater than 100 nm, linewidth is less than 50 nm, and aspect ratio is greater than 10:1. It also overcomes the problem of template and imprinted nanostructure damage that may occur when the rigid nanostructure template is demolded during the imprinting of large aspect ratio nanostructures. Attached Figure Description

[0017] Figure 1 This is a cross-sectional schematic diagram of the multilayer composite nanostructure imprint template composed of an elastic layer and a rigid layer according to the present invention. Figure 2 This is a cross-sectional schematic diagram of the multilayer composite nanostructure imprint template of the present invention, which consists of an elastic layer, a buffer layer and a rigid layer. Figure 3 This is a cross-sectional schematic diagram of the multilayer composite nanostructure imprint template of the present invention, which is composed of alternating rigid layers, elastic layers, and rigid layers. Figure 4 This is a cross-sectional schematic diagram of the multilayer composite nanostructure imprint template of the present invention, which is composed of an elastic layer, a rigid layer, a buffer layer, and a rigid layer in alternation. Figure 5 This is a reference diagram illustrating the principle of use of the present invention; Figure 6 This is a comparative example of the principle of this invention. In the figure: 1-substrate, 2-elastic layer, 3-rigid layer, 4-buffer layer. Detailed Implementation

[0018] The present invention will be clearly and completely described below with reference to specific embodiments, comparative examples, and the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The imprint template includes a substrate and at least one set of unit nanostructures composed of elastic and rigid layers stacked sequentially, the unit nanostructures being stacked to a predetermined thickness, such as... Figure 1 As shown. The imprint template includes a substrate and at least one set of unit nanostructures consisting of an elastic layer, a buffer layer, and a rigid layer stacked sequentially. The unit nanostructures are stacked to a predetermined thickness, such as... Figure 2As shown. The imprint template includes a substrate and at least one set of unit nanostructures consisting of a rigid layer, an elastic layer, and a rigid layer stacked sequentially. The unit nanostructures are stacked to a predetermined thickness, such as... Figure 3 As shown. The imprint template includes a substrate and at least one set of unit nanostructures consisting of an elastic layer, a rigid layer, a buffer layer, and a rigid layer stacked sequentially. The unit nanostructures are stacked to a predetermined thickness, such as... Figure 4 As shown.

[0020] The nanoimprint materials and imprinting equipment involved in the following embodiments are all products of Prin Technology (Hangzhou) Co., Ltd.

[0021] Example 1 A 150 nm copolymer elastomer composed of styrene, butadiene, and isoprene was spin-coated onto a quartz substrate, followed by a 200 nm UV-curable rigid material (model PL-R-PC1000). A cylindrical array template with a structure of 600 nm period, 300 nm column diameter and 250 nm height was attached to the sample surface after spin-coating two materials. A UV-cured nanoimprinting process was performed using a nanoimprinter (model PL-S-150), in which the pressure was maintained at 300 kPa and the UV exposure was 10 seconds to cure the UV-cured rigid layer. The residual layer of the rigid layer was removed using a reactive ion etching apparatus (Oxford-180). The selected gases were CF4 and O2, and the etching was performed in a certain ratio. After the residual layer was etched, the elastic layer material was exposed to the air. The nanostructure was then etched onto the surface of the quartz substrate using an oxygen reactive ion etching apparatus (Oxford-180). The selected gas was O2. The etched sample was then subjected to ion-enhanced chemical vapor deposition (Oxford-100) to deposit a 5-nanometer-thick silica coating layer. Finally, the sample was injected with an anti-sticking reagent (model PL-R-AT) in an anti-sticking device (model PL-AT-300) and reacted in the gas phase to bond a layer of low surface energy fluoroalkane organic small molecules to the surface of the silica coating layer, thus obtaining the imprint template of the multilayer composite nanostructure.

[0022] Example 2 A 200 nm polydimethylsiloxane (PDMS) biomolecular layer was spin-coated onto a quartz substrate, followed by a 250 nm UV-curable rigid material (model PL-R-PC1000). A cylindrical array template with a structure of 600 nm period, 300 nm column diameter and 250 nm height was attached to the sample surface after spin-coating two materials. A UV-cured nanoimprinting process was performed using a nanoimprinter (model PL-S-150), in which the pressure was maintained at 300 kPa and the UV exposure was 10 seconds to cure the UV-cured rigid layer. The residual layer of the rigid layer was removed using a reactive ion etching apparatus (Oxford-180). The selected gases were CF4 and O2, and the etching was performed in a certain ratio. After the residual layer was etched, the elastic layer material was exposed to the air. The nanostructure was then etched onto the surface of the quartz substrate using an oxygen reactive ion etching apparatus (Oxford-180). The selected gas was O2. The etched sample was subjected to electron beam evaporation equipment (model ULVC-Ei5z) to deposit a 10-nanometer thick silicon dioxide coating layer; Finally, the sample was injected with an anti-sticking reagent (model PL-R-AT) in an anti-sticking device (model PL-AT-300) and reacted in the gas phase to bond a layer of low surface energy fluoroalkane organic small molecules to the surface of the silica coating layer, thus obtaining the imprint template of the multilayer composite nanostructure.

[0023] Example 3 A 250 nm polydimethylsiloxane (PDMS) elastomer was spin-coated onto a PET polyester film substrate, followed by a 500 nm UV-curable rigid material (model PL-R-PC1000). A cylindrical array template with a structure of 600 nm period, 300 nm column diameter and 250 nm height was attached to the sample surface. A UV-cured nanoimprinting process was performed using a nanoimprinter (model PL-S-150), in which the pressure was maintained at 300 kPa and the UV exposure was 10 seconds to cure the UV-cured rigid layer. The residual layer of the rigid layer was removed using a reactive ion etching apparatus (Oxford-180). The selected gases were CF4 and O2, and the etching was performed in a certain ratio. After the residual layer was etched, the elastic layer material was exposed to the air. The nanostructure was then etched onto the surface of the PET polyester film substrate using an oxygen reactive ion etching apparatus (Oxford-180). The selected gas was O2. The etched sample was subjected to ion-enhanced chemical vapor deposition (Oxford-100) to deposit a 5-nanometer-thick silica coating layer. Finally, the sample was injected with an anti-sticking reagent (model PL-R-AT) in an anti-sticking device (model PL-AT-300) and reacted in the gas phase to bond a layer of low surface energy fluoroalkane organic small molecules to the surface of the silica coating layer, thus obtaining the imprint template of the multilayer composite nanostructure.

[0024] Example 4 A 200 nm polydimethylsiloxane (PDMS) elastomer was spin-coated onto a quartz substrate, followed by a 300 nm buffer layer (model PL-R-UL1000), and then a 400 nm UV-curable rigid material (model PL-R-PC1000) was spin-coated. A grating template with a structure of 150 nm period, 60 nm linewidth and 600 nm height was attached to the sample surface. A UV-cured nanoimprinting process was performed using a nanoimprinter (model PL-S-150), in which the pressure was maintained at 400 kPa and the UV exposure was 10 seconds to cure the UV-cured rigid layer. The residual layer of the rigid layer was removed using a reactive ion etching apparatus (Oxford-180) with CF4 and O2 as the selected gases in a specific ratio. After the residual layer was etched, the elastic layer material was exposed to air. The nanostructure was then etched onto the surface of the elastomer using the same reactive ion etching apparatus (Oxford-180) with CHF3 and O2 as the selected gases in a specific ratio. The nanostructure was then etched onto the surface of the quartz substrate using the same reactive ion etching apparatus (Oxford-180) with O2 as the selected gas. The etched sample was then subjected to ion-enhanced chemical vapor deposition (Oxford-100) to deposit a 10-nanometer-thick silica coating layer. Finally, the sample was injected with an anti-sticking reagent (model PL-R-AT) in an anti-sticking device (model PL-AT-300) and reacted in the gas phase to bond a layer of low surface energy fluoroalkane organic small molecules to the surface of the silica coating layer, thus obtaining the imprint template of the multilayer composite nanostructure.

[0025] Example 5 Spin-coat a 200 nm UV-curable rigid material (model PL-R-PC1000) onto a quartz substrate, then spin-coat a 400 nm polydimethylsiloxane (PDMS) elastomer, and then spin-coat a 600 nm UV-curable rigid material (model PL-R-PC1000). A lattice template with a structure of 100 nm period, 50 nm column diameter, and 600 nm height was attached to the sample surface. A UV-cured nanoimprinting process was performed using a nanoimprinter (model PL-S-150), where the pressure was maintained at 600 kPa and the UV exposure was 10 seconds to cure the UV-curable rigid layer (PL-R-PC1000). The residual layer of the rigid layer was removed using a reactive ion etching apparatus (Oxford-180) with CF4 and O2 as the selected gases, and the etching was performed in a certain ratio. After the residual layer was etched, the elastic layer material was exposed to the air. The nanostructure was then etched onto the surface of the elastomer using the same reactive ion etching apparatus (Oxford-180) with O2 as the selected gas, and the etching was performed in a certain ratio. The nanostructure was then etched onto the surface of the quartz substrate using the same reactive ion etching apparatus (Oxford-180) with CF4 and O2 as the selected gases. The etched sample was subjected to ion-enhanced chemical vapor deposition (Oxford-100) to deposit a 5-nanometer-thick silica coating layer. Finally, the sample was injected with an anti-sticking reagent (model PL-R-AT) in an anti-sticking device (model PL-AT-300) and reacted in the gas phase to bond a layer of low surface energy fluoroalkane organic small molecules to the surface of the silica coating layer, thus obtaining the imprint template of the multilayer composite nanostructure.

[0026] Comparative Example 1 This comparative example uses a single-layer rigid template as the imprinting template. The difference between this single-layer rigid template and the template obtained in Example 1 is that it does not have a more encapsulating property, which can better encapsulate the particles during the imprinting process, resulting in an excessively large area of ​​imprinting defects due to incomplete adhesion during the imprinting process.

[0027] Comparative Example 2 The multi-layer template used in this comparative example differs from the template in Example 4 in that, during the high aspect ratio nanostructure imprinting process, the demolding process of the multi-layer template can easily damage the UV-curable material after imprinting, resulting in imprinting failure. In Example 4, the elastic layer and buffer layer allow the template structure to remain bent throughout the demolding process, making demolding easier.

[0028] Comparative Example 3 The elastic template used in this comparative example is an imprinting template. The structural materials of this elastic template are all elastic materials. In high-resolution, high-intensity nanoimprinting processes, the applied pressure causes deformation of the nanostructures themselves, which are typically elastic materials. In Example 5, the multilayer composite imprinting template uses multiple layers of rigid, cured nanostructure materials. Under high pressure during the imprinting process, it can maintain the shape of the nanostructures while also providing better demolding and flexible replication results.

[0029] The embodiments described in this specification are merely examples of implementations of the inventive concept and are for illustrative purposes only. The scope of protection of this invention should not be considered limited to the specific forms described in these embodiments; rather, it extends to equivalent technical means conceived by those skilled in the art based on the inventive concept.

Claims

1. An imprint template with a multilayer composite nanostructure, characterized in that... It includes a substrate and a nanostructure layer, wherein the nanostructure layer is composed of two or more layers of materials with different mechanical properties, including at least an elastic layer and a rigid layer; The substrate is a UV-transmitting material, made of glass, quartz, methyl methacrylate film, PET polyester film, polycarbonate film, polyimide film, polystyrene film, polysiloxane elastomer, styrene elastomer, olefin elastomer, polyurethane elastomer, diene elastomer, or vinyl chloride elastomer. The rigid layer is a UV-curable material resistant to oxygen reactive ion etching, with an elastic modulus of 100 N / mm². 2 The thickness ranges from 50 nanometers to 1 micrometer. The elastic layer is a polymeric elastomer material with an elastic modulus of 20 N / mm². 2 The following properties are provided: elongation at break is greater than 50%, thickness is adjustable, and the ratio of its thickness to the rigid layer is less than 1. The elastic layer is made of a copolymer elastomer composed of styrene, butadiene, and isoprene, a chloroprene rubber-styrene graft copolymer elastomer, an ethylene propylene rubber-styrene graft copolymer elastomer, a polyurethane elastomer, a polyester elastomer, or a polysiloxane elastomer. A buffer layer is provided between the elastic layer and the rigid layer. The imprint template includes a substrate and at least one set of unit nanostructures composed of an elastic layer, a buffer layer and a rigid layer stacked sequentially. The unit nanostructures are stacked to a set thickness. The material of the buffer layer has a modulus of 20 N / mm². 2 ~100 N / mm 2 The elongation at break is greater than 50%, and the ratio of its thickness to that of the rigid layer is less than 1. The material of the buffer layer is a blend of the rigid layer material and the elastic layer material. The surface of the nanostructure layer is covered with a silicon dioxide coating layer with a thickness of 5-10 nanometers. The silicon dioxide is coated by electron beam evaporation, magnetron sputtering or plasma-enhanced chemical vapor deposition. A low surface energy fluorinated alkane organic small molecule layer is bonded to the surface of the silicon dioxide coating layer.

2. The imprint template with a multilayer composite nanostructure as described in claim 1, characterized in that... The thickness of the rigid layer is between 200 nanometers and 800 nanometers.

3. The imprint template with a multilayer composite nanostructure as described in claim 1, characterized in that... The thickness of the rigid layer is between 400 nanometers and 600 nanometers.

4. The imprint template with a multilayer composite nanostructure as described in claim 1, characterized in that... The material of the buffer layer has a modulus of 40 N / mm². 2 ~70 N / mm 2 .

5. The method for preparing a multilayer composite nanostructure imprint template as described in claim 1, characterized in that... Includes the following steps: 1) First, the elastic layer and the buffer layer are coated and cured on the substrate using a spin coater. Then, an oxygen-resistant reactive ion etching-resistant UV-curable rigid layer is spin-coated. Next, the rigid layer is imprinted and cured using a master template. 2) Fluorine-based reactive ion etching removes the residual layer of the rigid layer, and then oxygen reactive ion etching removes the buffer layer and elastic layer below the residual layer to obtain a multilayer composite nanostructure. 3) The surface of the multilayer composite nanostructure is coated with a silicon dioxide coating layer with a thickness of 5-10 nanometers by electron beam evaporation, magnetron sputtering or plasma-enhanced chemical vapor deposition; 4) Finally, through a gas-phase reaction, the Si-OH groups on the silica react with perfluorotrichlorosilane to bond a layer of low surface energy fluoroalkane organic small molecules to the surface of the silica coating layer, thus obtaining the imprint template of the multilayer composite nanostructure.

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