A method for preparing a nano forest structure

Abstract

The present invention relates to a method for preparing a nano forest structure, comprising: providing a substrate; coating a polymer layer on the surface of the substrate; and subjecting the polymer layer to at least one S1 and S2 treatment: S1, etching by a first plasma, S2, regrouping by a second plasma to form a nano forest structure. The present invention adopts a special dry etching process to make the nano forest structure. By changing the process parameters of etching and regrouping, or by changing the number of etching and regrouping cycles, the size and density of the nano forest structure can be effectively controlled, thereby obtaining a precisely controllable nano forest structure. The preparation method has the advantages of low processing cost, high processing accuracy, and simple preparation process, and has broad application prospects.

Description

Technical Field

[0001] The invention relates to the field of nanotechnology, and in particular to a method for preparing a nano forest structure. Background Art

[0002] Nanoforests refer to large-area nanoscale columnar structures with high density on the surface of materials. Due to their special surface effects such as large specific surface area and high porosity, they have broad and important application prospects in new energy devices, biomedical detection devices, microfluidic devices, electronic devices and nanoimprinting. Therefore, how to process and manufacture low-cost nanoforest structures with controllable morphology and size has become one of the research hotspots in nanotechnology.

[0003] At present, the preparation of nanostructures generally adopts methods such as electron beam lithography (Electron-Beam Lithography), focused ion beam (FIB) etching and chemical synthesis growth technology (Vapor Liquid Solid, VLS).

[0004] Electron beam lithography and focused ion beam etching are both “top-down” methods for processing nanostructures. They rely on corresponding cutting-edge equipment, which is expensive and mostly uses serial processing mode. This restricts the processing of nanopillar forest structures, greatly affecting their promotion and application in research, development, and productization. Although VLS chemical synthesis technology is a parallel preparation process with simple process steps and can prepare nanoforest structures on a large area, the direction and size parameters of the nanoforest structures prepared by this technology are difficult to control well, which in turn affects the characteristics of the nanoforest structures. In addition, this technology is difficult to be compatible with conventional MEMS processes, which further limits the application of this technology in devices.

[0005] Therefore, those skilled in the art hope to develop a simple and easy non-photolithography method to prepare a nanoforest structure, and through this method effectively control the size and density of the nanoforest, so as to obtain a precisely controllable nanoforest structure. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a nanoforest structure. The method prepares the nanoforest structure through a simple and easy non-photolithography method without relying on cutting-edge equipment. It has the advantages of low processing cost, simple preparation process, and can effectively control the size and density of the nanoforest structure, and has broad application prospects.

[0007] To this end, the present invention provides a method for preparing a nano forest structure, comprising:

[0008] providing a substrate;

[0009] Coating a polymer layer on the surface of the substrate;

[0010] The polymer layer is subjected to at least one S1 and S2 treatment: S1, etching by a first plasma, and S2, re-polymerization by a second plasma to form a nano-forest structure.

[0011] Further, the material of the substrate can be selected from silicon-based materials, glass, quartz or sapphire. For example, in some embodiments, the material of the substrate is silicon-based material, and the substrate can be a Si wafer, a SiGe wafer or a SOI wafer.

[0012] Furthermore, the polymer is selected from one or a combination of two or more of polyimide, polydimethylsiloxane, polyethylene, polymethyl methacrylate and other polymer materials that can be etched by plasma and whose main elements are C, H and O. In a preferred embodiment, the polymer is polyimide.

[0013] Furthermore, the coating may be spin coating or spray coating; in a preferred embodiment, it is spin coating. When spin coating is adopted, the thickness of the polymer layer can be controlled by the spin coating rotation speed.

[0014] Furthermore, after the coating, the method further comprises the following step: heating.

[0015] Furthermore, the heating method is oven heating or hot plate baking. In a preferred embodiment, the heating temperature is 100-180° C. and the heating time is 10-60 min.

[0016] Furthermore, the thickness of the polymer layer can be set according to requirements, for example, it can be 2-10 μm.

[0017] Furthermore, the first plasma is selected from one or both of oxygen plasma (O2) or carbon tetrafluoride plasma (CF4); preferably oxygen plasma.

[0018] Furthermore, the etching in step S1 is anisotropic etching. In a preferred embodiment, the direction of the anisotropic etching is perpendicular to the substrate surface.

[0019] Furthermore, the etching conditions include: chamber pressure of 1-100 mT, preferably 5-20 mT; upper electrode power range of 100-1000 W, preferably 100-500 W; lower electrode power range of 0-1000 W, preferably 50-200 W.

[0020] Furthermore, the second plasma is selected from an inert gas such as argon plasma (Ar), helium plasma (He), nitrogen plasma (N2) or methane plasma (CH4) or a combination of two or more thereof.

[0021] Furthermore, the conditions for the recombination include: the chamber pressure is 1-100mT, preferably 5-20mT; the upper electrode power range is 100-1000W, preferably 100-500W; the lower electrode power range is 0-1000W, preferably 50-500W.

[0022] Further, the number of times the polymer layer is subjected to S1 and S2 treatment is n times, wherein n is an integer selected from 1 to 50. Since the more cycles are performed, the larger the size of the nanostructure is, the cycle can be performed according to the required size structure, for example, the number of times the S1 and S2 treatments are performed can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45 or 50 times.

[0023] Compared with the prior art, the technical solution of the present invention has at least the following advantages:

[0024] (1) The present invention provides a simple and easy non-photolithography method to prepare nanoforest structures. It does not rely on cutting-edge equipment and its processing cost is significantly lower than that of electron beam lithography or focused ion beam etching. In addition, the preparation method provided by the present invention is compatible with conventional MEMS processes and has broad application prospects.

[0025] (2) The present invention adopts a special dry etching process to produce the nanoforest structure. The preparation process is simple. By changing the process parameters of etching and polymer deposition, or by changing the number of cycles of etching and polymer deposition, the size and density of the nanoforest structure can be effectively controlled, thereby obtaining a precisely controllable nanoforest structure. The preparation process can realize parallel processing and large-area preparation of nanoforest structures, and is suitable for large-scale commercial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0027] Figure 1 The process flow chart of the preparation method of the nano forest provided by the present invention is shown;

[0028] Figure 2 A schematic diagram of the structure after a polymer layer is provided on the surface of a substrate provided by an embodiment of the present invention is shown;

[0029] Figure 3 The first plasma Figure 2 A schematic diagram of the structure of the polymer layer after the first etching is shown;

[0030] Figure 4 The second plasma Figure 3 Schematic diagram of the structure after the first reunion of the structure shown;

[0031] Figure 5 Shows the Figure 4 The schematic diagram of the structure after the structure shown is cyclically etched and reassembled to obtain a nanoforest structure that meets the target size and / or density requirements;

[0032] Figure 6 The SEM image of the nanofiber structure formed after the polyimide layer on the surface of the substrate is etched for the first time according to the method provided by the present invention is shown;

[0033] Figure 7 The SEM image of the nano-forest structure formed after the polyimide layer on the surface of the substrate is first etched and first reassembled according to the method provided by the present invention is shown;

[0034] Figure 8 The SEM image of the nano-forest structure formed after the polyimide layer on the surface of the substrate is etched and reassembled three times in a cycle according to the method provided by the present invention is shown;

[0035] The above drawings include the following reference numerals:

[0036] 1. Substrate; 2. Polymer layer; 3. Nanofiber structure; 4. Nanoforest structure after the first cycle; 5. Target nanoforest structure. DETAILED DESCRIPTION

[0037] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0038] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0039] It should be noted that the terms "first", "second" and the like in the claims, specification and drawings of the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0040] As introduced in the background technology, the current processing methods of nano forest structures have the problems of high cost, expensive equipment, low processing efficiency, difficulty in effectively controlling the direction and size parameters of the nano forest structure, and poor compatibility with subsequent processes. Therefore, it is urgent to develop a simple and easy non-photolithography method that can accurately control the nano forest structure to prepare the nano forest structure. In order to solve the above technical problems, the present invention provides a method for preparing a nano forest structure, comprising the following steps:

[0041] providing a substrate;

[0042] coating a polymer layer on a surface of a substrate;

[0043] The polymer layer is subjected to at least one S1 and S2 treatment: S1, etching by a first plasma, and S2, re-polymerization by a second plasma to form a nano-forest structure.

[0044] The above preparation method accurately and effectively controls the size and density of the nanoforest by cyclically performing a special dry etching process (i.e., steps S1 and S2).

[0045] The following will describe in more detail an exemplary method of preparing a nano forest structure according to the present invention. Of course, these exemplary embodiments can be implemented in a variety of different forms and should not be construed as being limited to the embodiments described herein.

[0046] First, a substrate is provided. The material of the substrate of the present invention is not particularly limited, and other base materials commonly used in micro-machining processes can be used, for example, silicon-based materials, glass, quartz or sapphire. For example, in some embodiments, the material of the substrate is a silicon-based material, and the substrate can be a Si wafer, a SiGe wafer or an SOI wafer. The choice of substrate material has no significant effect on the subsequent processing process.

[0047] Then, a polymer layer is coated on the substrate.

[0048] In the step of coating the polymer layer, the polymer may be directly coated on the substrate, or a mixture comprising an adhesive and the polymer may be coated on the substrate. When a mixture comprising an adhesive and the polymer is used for coating, the proportion and type of the adhesive in the mixture may be determined according to conventional experimental conditions in the art.

[0049] The coating can be performed by spin coating or spray coating; preferably spin coating because the uniformity of spin coating is better than that of spray coating. Preferably, a heating step is also included, and the heating can be performed by oven heating or hot plate baking. The heating can be performed under the following conditions: the heating temperature is 100-180°C and the heating time is 10-60 minutes. The heating step can remove organic matter.

[0050] The polymer is selected from one or a combination of two or more of polyimide, polydimethylsiloxane, polyethylene, polymethyl methacrylate and other polymer materials that can be bombarded by plasma and whose main elements are C, H and O. In a preferred embodiment, the polymer is polyimide.

[0051] After coating the polymer layer on the substrate, the polymer layer is processed in steps S1 and S2: S1, etching by the first plasma to form a nanofiber structure, S2, polymerizing and depositing the nanofiber structure by the second plasma to form a nanoforest structure. If the fiber size and structure of the nanoforest meet the target requirements, the process can be stopped after the polymer layer is processed in steps S1 and S2 once; if the fiber size and structure of the nanoforest do not meet the target requirements, steps S1 and S2 are repeated until the nanoforest structure has the target size and / or density.

[0052] When the polymer is selected from polyimide, polydimethylsiloxane, polyethylene, polymethyl methacrylate or other polymer materials that can be bombarded by plasma and whose main elements are C, H, and O, the following first plasma and second plasma can be used for treatment:

[0053] The first plasma is selected from one or both of oxygen plasma (O2) and carbon tetrafluoride plasma (CF4); preferably oxygen plasma;

[0054] The second plasma is selected from an inert gas such as argon plasma (Ar), helium plasma (He), nitrogen plasma (N2) or methane plasma (CH4) or a combination of two or more thereof.

[0055] When the polymer is polyimide, the specific parameters of the above steps S1 and S2 include:

[0056] S1, anisotropically etching the polyimide layer using O2 or CF4 gas;

[0057] The chamber pressure is 1-100 mT; preferably 5-20 mT;

[0058] The upper electrode power is 100-1000W, preferably 100-500W; too low upper electrode power is not conducive to plasma ionization, while too high power cannot increase the concentration of plasma and will cause energy waste;

[0059] The power of the lower electrode is 0-1000W, preferably 50-200W; too high a power of the lower electrode will make the energy of the reaction particles too high, causing damage to the substrate;

[0060] S2, using Ar, He, N2 or CH4 gas to recombine the nanostructure of polyimide, through which the nanostructure can be recombinated to form thicker nanofibers, that is, to form a nanoforest structure;

[0061] The chamber pressure is 1-100 mT, preferably 5-20 mT;

[0062] The upper electrode power is 100-1000W, preferably 100-500W; too low upper electrode power is not conducive to the ionization of the reaction, while too high power cannot increase the concentration of plasma and will cause energy waste;

[0063] The power of the lower electrode is 0-1000W, preferably 50-500W; too low a power of the lower electrode is not conducive to the recombination reaction, and too high a power of the lower electrode will make the energy of the reaction particles too high, causing damage to the substrate.

[0064] When the polymer is polydimethylsiloxane, polyethylene, or polymethyl methacrylate, the same parameters as those when the polymer is polyimide can still be used.

[0065] According to the preparation method provided by the present invention, the size of a single nanofiber structure of the prepared nanoforest structure can reach 50-500nm, the height can reach 1-10μm, and the distance between single nanofiber structures can reach 20-200nm. It should be pointed out that by adjusting the process parameters of etching and reassembly, or by changing the number of cycles of etching and reassembly, the size and density of the nanoforest structure can be effectively controlled, thereby achieving a nanoforest structure that meets the target requirements and is precisely controllable.

[0066] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for preparing a nano forest structure, characterized in that The following steps are involved: providing a substrate; Coating a polymer layer on the surface of the substrate; The polymer layer is subjected to at least one of S1 and S2 treatments: S1, etching by a first plasma to form a nanofiber structure, and S2, reuniting the nanofiber structure by a second plasma to form a nanoforest structure; The first plasma is selected from one or a combination of oxygen plasma or carbon tetrafluoride plasma; the second plasma is selected from one or a combination of two or more of argon plasma, helium plasma and methane plasma; The etching conditions include: chamber pressure of 1-100mT, upper electrode power range of 100-1000W, lower electrode power range of 0-1000W; the regrouping conditions include: chamber pressure of 1-100mT, upper electrode power range of 100-1000W, lower electrode power range of 0-1000W.

2. The preparation method according to claim 1, characterized in that The material of the substrate is selected from silicon-based materials, glass, quartz or sapphire.

3. The preparation method according to claim 1, characterized in that: The polymer is selected from one or a combination of two or more of polyimide, polydimethylsiloxane, polyethylene and polymethyl methacrylate.

4. The preparation method according to claim 1, characterized in that: The step of applying the polymer layer further comprises heating.

5. The preparation method according to claim 4, characterized in that: The heating temperature is 100-180° C., and the heating time is 10-60 min.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The etching is anisotropic etching.

7. The preparation method according to claim 6, characterized in that: The direction of the anisotropic etching is perpendicular to the substrate surface.

8. The preparation method according to any one of claims 1 to 5, characterized in that: The etching conditions include: chamber pressure of 5-20 mT; upper electrode power range of 100-500 W; lower electrode power range of 50-200 W.

9. The preparation method according to any one of claims 1 to 5, characterized in that: The number of times the polymer layer is subjected to the S1 and S2 treatments is n times, wherein n is an integer selected from 1-50.

10. The preparation method according to any one of claims 1 to 5, characterized in that: The conditions for the reunification include: chamber pressure of 5-20 mT; upper electrode power range of 100-500 W; lower electrode power range of 50-500 W.

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