High-aspect-ratio micro-nano needle tip array based on self-assembled mask and preparation method of high-aspect-ratio micro-nano needle tip array

Abstract

The invention discloses a high-aspect-ratio micro-nano needle tip array based on a self-assembled mask and a preparation method of the high-aspect-ratio micro-nano needle tip array. The preparation method comprises the following steps: forming tightly arranged self-assembled microspheres on the surface of a silicon wafer to obtain a self-assembled mask; etching the self-assembled mask by adopting an ICP (Inductively Coupled Plasma) etching mode to obtain a patterned mask; etching the patterned mask by adopting an ICP (Inductively Coupled Plasma) etching mode to obtain a micro-nano needle tip array containing the mask; and removing the mask to obtain the micro-nano needle tip array. According to the method, the large-area, flexible and adjustable micro-nano needle tip array with the high aspect ratio can be prepared under the conditions of high efficiency and low cost.

Description

Technical Field

[0001] The invention relates to a high aspect ratio micro-nano needle tip array based on a self-assembly mask and a preparation method thereof, belonging to the technical field of micro-nano processing. Background Art

[0002] Micro-nano processing in the prior art mainly uses techniques such as photolithography, wet etching, dry etching, and electrolytic deposition to process and manufacture micron-scale and nanometer-scale materials. The preparation of micro-nano needle tip arrays in the prior art often has problems such as complicated process flow and high cost.

[0003] CN115793414B discloses a method for preparing a high aspect ratio microstructure with adjustable height ratio. The method comprises the following steps: first, a layer of photoresist is spin-coated on the substrate at a low speed, and a non-uniform dose of grayscale exposure and development is performed by a laser direct writing device; then, the multi-level height photoresist column is first etched, and the etching time and etching depth are selected according to the ratio of the multi-level structure; then, oxygen plasma is used to remove the residual photoresist after etching the first-level structure; then, the second-level structure is etched; then, the residual glue on the upper layer of the second-level structure is removed; and so on, the etching and degumming process is cyclically performed until the top layer of the last-level structure is removed. The method adopts a photolithography process, which has high requirements on the preparation environment, and adopts a two-step Bosch-tapering process, which has the disadvantages of complicated technology and unstable processing effect.

[0004] CN116119604A discloses a method and device for preparing a high-density silicon microneedle array. The method comprises the following steps: providing a silicon substrate, and preparing a negative photoresist layer on the silicon substrate; patterning the negative photoresist layer; preparing a positive photoresist layer corresponding to the patterned negative photoresist layer; heating and reflowing the prepared positive photoresist layer to obtain a positive reflow photoresist layer; dry etching the silicon substrate using the positive reflow photoresist layer and the patterned negative photoresist layer to form a desired silicon microneedle array after etching, wherein the silicon microneedle array comprises a microneedle body distributed on the silicon substrate, and the microneedle body comprises a needle body portion distributed on the silicon substrate and a needle head portion located on the needle body portion; removing the positive reflow photoresist layer and the patterned negative photoresist layer. This method requires first using a patterned negative photoresist as a preliminary mask, and then using a reflow process positive photoresist to generate an arc mask. After the etching is completed, the photoresist still needs to be subsequently removed. The process flow is cumbersome and the process stability is difficult to control.

[0005] CN109173039B discloses a method for preparing an inverted funnel-shaped silicon-based solid microneedle array. The method comprises the following steps: 1) depositing a front silicon nitride protective film and a back silicon nitride protective film on a single crystal silicon wafer; 2) spin-coating a photoresist on the front silicon nitride protective film for photolithography, and the photoresist after photolithography forms an array-shaped circular shielding film; 3) dry-etching the front silicon nitride protective film exposed outside the shielding film to expose the single crystal silicon wafer; 4) using an inductively coupled plasma etching system and a deep silicon etching Bosch process to anisotropically etch the single crystal silicon wafer to etch an array-shaped cylinder on the single crystal silicon wafer; 5) removing the shielding film on the single crystal silicon wafer; 6) using an acidic etching solution to isotropically wet-etch the single crystal silicon wafer to obtain a microneedle array. This method requires first using a patterned photoresist as a mask, generating a microcolumn array through a Bosch process, and finally forming a needle tip array by wet etching. The process flow is cumbersome and the process stability is difficult to control.

[0006] CN115285931A discloses a method for preparing a conical silicon-based solid microneedle array. The method comprises: (1) selecting a single-polished single-crystal silicon wafer, the single-polished single-crystal silicon wafer comprising a polished surface and a second surface opposite to each other, depositing a silicon nitride protective film on the polished surface and the second surface respectively, and plating an aluminum protective film on the silicon nitride protective film on the polished surface by magnetron sputtering; (2) transferring a mask pattern to the aluminum protective film on the polished surface by photolithography; (3) etching the aluminum protective film and etching the silicon nitride protective film on the polished surface; (4) anisotropically etching the polished surface of the silicon wafer after step (3) to obtain a cylindrical array structure; (5) isotropically wet etching the silicon wafer after step (4) to etch a radially controllable conical array structure, and the etching liquid is placed in an ice-water mixture tank; (6) cleaning the silicon wafer after step (5) to remove residual acidic etching liquid on the silicon wafer. This method uses a two-step process of masking and bosch-tapering, and has problems such as complicated process flow and difficult to control process stability.

[0007] It can be seen that the existing technology for preparing micro-nano needle tip arrays often first uses positive photoresist or negative photoresist to generate a patterned mask through photolithography development; then uses etching technology to generate micrometer-level or nanometer-level cylindrical arrays; and then uses anisotropic wet etching methods to form needle tip arrays. The existing technology has at least the following problems: the process steps are cumbersome, the cost is high, the parameter control is difficult, the use of wet etching is subject to large fluctuations in interface components and etching liquid parameters, and the environmental conditions are high, and the safety risks are high; it is difficult to control the shape of the needle tip array, which is more suitable for processing needle tip arrays of hundreds of micrometers, but it is difficult to process micro needle tip arrays in the size range of nanometers to several micrometers; it is difficult to adjust parameters, and the preparation of needle tip arrays of different structures and sizes requires a lot of parameter optimization to achieve; it is difficult to achieve efficient and rapid preparation of large-scale structures, which limits the industrial application of micro-nano needle tip arrays in actual devices. Summary of the invention

[0008] In order to solve at least one of the above technical problems, the purpose of the present invention is to provide a high aspect ratio micro-nano needle tip array based on a self-assembled mask and a preparation method thereof. The present invention can prepare a large-area, flexible and controllable high aspect ratio micro-nano needle tip array under high efficiency and low cost.

[0009] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a high aspect ratio micro-nano needle tip array based on a self-assembled mask, which comprises the following steps:

[0010] S1: forming tightly packed self-assembled microspheres on the surface of silicon wafer to obtain a self-assembled mask;

[0011] S2: etching the self-assembled mask by ICP etching to obtain a patterned mask;

[0012] S3: etching the patterned mask by ICP etching to obtain a micro-nano needle tip array containing the mask;

[0013] S4: removing the mask from the micro-nano needle tip array containing the mask to obtain the high aspect ratio micro-nano needle tip array based on the self-assembled mask.

[0014] According to a specific embodiment of the present invention, preferably, step S1 includes: extracting a dispersion of microspheres using a needle; placing ultrapure water in a container; connecting one end of the needle to a syringe pump and the other end to a hose, overlapping the hose to the liquid surface of the ultrapure water in the container, and injecting the dispersion of microspheres into the liquid surface of the ultrapure water in the container using the syringe pump, needle and hose; immersing a gel containing sodium dodecyl sulfate from one side of the liquid surface edge into ultrapure water for 1-60 seconds to form a tightly arranged structure of the microspheres on the liquid surface; placing a silicon wafer below the liquid surface, and then taking it out tilted upward at an angle greater than 0° and less than 60° to the liquid surface, and transferring the tightly arranged self-assembled microspheres to the surface of the silicon wafer, and after drying, obtaining the self-assembled mask.

[0015] According to a specific embodiment of the present invention, preferably, in step S1, the microspheres include one or a combination of polystyrene microspheres, silica microspheres, polymethyl methacrylate microspheres, polyvinyl alcohol microspheres, and the like.

[0016] According to a specific embodiment of the present invention, preferably, in step S1, the diameter of the microspheres is 50 nm-10 μm.

[0017] According to a specific embodiment of the present invention, preferably, in step S1, the microsphere dispersion is injected into the liquid surface of ultrapure water in the container at an injection speed of 10-500 μl / min.

[0018] According to a specific embodiment of the present invention, preferably, in step S1, the closely arranged self-assembled microspheres formed on the surface of the silicon wafer are a single layer of microspheres.

[0019] According to a specific embodiment of the present invention, preferably, in step S2, the conditions for etching the self-assembled mask by ICP etching include: the upper electrode power is 30-500W, the lower electrode power is 5-100W, the pressure is 1-50Pa, the etching gas is Ar and / or O2, the etching gas flow rate is 10-150sccm, and the etching time is 30-300s.

[0020] According to a specific embodiment of the present invention, preferably, in step S3, the conditions for etching the patterned mask by ICP etching include: the upper electrode power is 100-1500W, the lower electrode power is 5-50W, the pressure is 1-50Pa, C4F8 gas is used as the passivation gas, and SF6 gas is used as the etching gas, and the two are alternately cycled for several times. More preferably, in a single cycle, the C4F8 gas flow rate is 10-200sccm, the passivation time is 5-50s, the SF6 gas flow rate is 10-200sccm, and the etching time is 5-50s. More preferably, the number of said several cycles is 10-300 times.

[0021] According to a specific embodiment of the present invention, preferably, step S4 comprises: immersing the micro-nano needle tip array containing the mask in ultrapure water for ultrasonic cleaning to remove the mask and obtain the high aspect ratio micro-nano needle tip array based on the self-assembled mask.

[0022] The second aspect of the present invention provides a high aspect ratio micro-nano needle tip array based on a self-assembled mask, which is prepared by the above-mentioned preparation method.

[0023] According to a specific embodiment of the present invention, preferably, the aspect ratio of the high aspect ratio micro-nano needle tip array based on the self-assembled mask is 1:5 to 10:1.

[0024] According to a specific embodiment of the present invention, preferably, the diameter of the top end of the needle tip in the high aspect ratio micro-nano needle tip array based on the self-assembled mask is 10-30 nm, and the diameter of the bottom end of the needle tip is 50 nm-5 μm.

[0025] According to a specific embodiment of the present invention, preferably, the spacing between the bottom ends of two adjacent needle tips in the high aspect ratio micro-nano needle tip array based on the self-assembled mask is 100 nm-10 μm.

[0026] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0027] The present invention studies the self-assembly technology of microspheres, which can realize the rapid preparation of large-area silicon wafer surface masks, and can flexibly adjust the mask size according to processing requirements, without the need to use photolithography, with low environmental requirements and low cost. On this basis, the present invention only adopts the Bosch process, and by adjusting the ICP process parameters, it can realize the formation of an inclination angle while etching downward, and realizes the rapid preparation of a high aspect ratio micro-nano needle tip array in a one-step method, and can flexibly adjust the microneedle height according to requirements, and the processing technology is stable. The present invention overcomes the problems of cumbersome process flow, more process steps, and higher preparation cost in the prior art, avoids the Bosch-tapering two-step process in the prior art, avoids the technical path of preparing patterned photoresist masks, dry etching, and wet etching, and has many advantages such as low process cost, easy adjustment of parameters, high flexibility, high processing efficiency, and stable processing effect. Therefore, the present invention can prepare a large-area, flexible and controllable high aspect ratio micro-nano needle tip array under the conditions of high efficiency, rapidity, and low cost. The high aspect ratio micro-nano needle tip array prepared by the present invention can be widely used in optical devices, energy absorption and storage devices, hydrophilic and hydrophobic surface regulation, droplet transport, biosensors, bioengineering and biomanufacturing, etc., and has key technology transformation value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the structure of the microsphere self-assembly system in Example 1.

[0029] Figure 2 This is an electron microscope image of the arrangement of the self-assembled mask in Example 1.

[0030] Figure 3 Schematic diagram of the process of steps S2 and S3 in Examples 1-3.

[0031] Figure 4 This is a morphology diagram of the micro-nano needle tip array in Example 1.

[0032] Figure 5 This is a morphology diagram of the micro-nano needle tip array in Example 2.

[0033] Figure 6 This is a morphology diagram of the micro-nano tip array in Example 3.

[0034] Description of Figure Numbers:

[0035] 1-needle; 2-syringe pump; 3-hose; 4-container. DETAILED DESCRIPTION

[0036] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the present invention is now described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0037] It should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0038] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0039] According to a specific embodiment of the first aspect of the present invention, the present invention provides a method for preparing a high aspect ratio micro-nano needle tip array based on a self-assembled mask, which comprises the following steps:

[0040] S1: forming tightly packed self-assembled microspheres on the surface of silicon wafer to obtain a self-assembled mask;

[0041] S2: etching the self-assembled mask by ICP etching to obtain a patterned mask;

[0042] S3: etching the patterned mask by ICP etching to obtain a micro-nano needle tip array containing the mask;

[0043] S4: removing the mask from the micro-nano needle tip array containing the mask to obtain the high aspect ratio micro-nano needle tip array based on the self-assembled mask.

[0044] In some embodiments, the silicon wafer may be a silicon wafer with a (100) crystal plane or a silicon wafer with a (111) crystal plane.

[0045] In some embodiments, the preparation method further includes step S0 before step S1: pre-treating the silicon wafer, the pre-treatment including cleaning and heat treatment. The cleaning may be ultrasonic cleaning in an organic solvent, such as but not limited to acetone, and the time, power and frequency of the ultrasonic cleaning may be conventionally adjusted by a person skilled in the art. After ultrasonic cleaning, contamination on the surface of the silicon wafer may be removed. The temperature of the heat treatment may be 200°C and the time may be 1-10 minutes. The heat treatment may be performed using a hot plate. After heat treatment, organic impurities on the surface of the silicon wafer may be removed.

[0046] In some embodiments, step S1 includes: using a syringe to extract a dispersion of microspheres; placing ultrapure water in a container; connecting one end of the syringe to a syringe pump and the other end to a hose, overlapping the hose to the liquid surface of the ultrapure water in the container, and using the syringe pump, syringe and hose to inject the dispersion of microspheres into the liquid surface of the ultrapure water in the container; immersing a gel containing sodium dodecyl sulfate from one side of the liquid surface edge into ultrapure water for 1-60 seconds to form a tightly arranged structure of the microspheres on the liquid surface; placing a silicon wafer below the liquid surface, and then taking it out tilted upward at an angle greater than 0° and less than 60° to the liquid surface, and transferring the tightly arranged self-assembled microspheres to the surface of the silicon wafer. After drying, the self-assembled mask is obtained.

[0047] In some embodiments, in step S1, the microspheres include one or a combination of polystyrene microspheres, silica microspheres, polymethyl methacrylate microspheres, polyvinyl alcohol microspheres, etc. More preferably, the diameter of the microspheres is 50 nm-10 μm.

[0048] In some embodiments, in step S1, the solvent in the microsphere dispersion is, for example, but not limited to, one or a combination of dimethyl sulfoxide (DMSO), alcohol, anhydrous ethanol, and isopropanol. The concentration of the microspheres in the microsphere dispersion may be 1×10 6 / ml to 1×10 10 Pieces / ml.

[0049] In some embodiments, in step S1, the dispersion of microspheres is obtained by dispersing the microspheres in a solvent by ultrasound, wherein the time, power and frequency of the ultrasound can be conventionally adjusted by those skilled in the art.

[0050] In some embodiments, in step S1, the microsphere dispersion is injected into the liquid surface of ultrapure water in the container at an injection speed of 10-500 μl / min.

[0051] In some embodiments, in step S1 , the closely arranged self-assembled microspheres formed on the surface of the silicon wafer are a single layer of microspheres.

[0052] In some embodiments, in step S1, the amount of the gel containing sodium dodecyl sulfate is not particularly limited as long as it can be completely immersed in ultrapure water.

[0053] In some embodiments, in step S1, the gel containing sodium dodecyl sulfate may include sodium dodecyl sulfate polyacrylamide gel. The sodium dodecyl sulfate polyacrylamide gel can be prepared by conventional methods in the art, and the present invention does not specifically limit it. Specifically, the preparation method of the sodium dodecyl sulfate polyacrylamide gel may include the following steps: reacting a mixed system of acrylamide, a crosslinking agent, a promoter, an initiator, sodium dodecyl sulfate and water to obtain sodium dodecyl sulfate polyacrylamide gel. Among them, the crosslinking agent includes N, N'-methylenebisacrylamide, etc., the promoter includes N, N, N', N'-tetramethylethylenediamine, etc., and the initiator includes ammonium persulfate or a redox initiator system containing ammonium persulfate, etc. The amount of acrylamide, crosslinking agent, promoter, initiator, sodium dodecyl sulfate and water can be conventionally adjusted in the art. The reaction can be carried out in a mold, the reaction temperature can be 20-30°C, and the time can be 1-20 hours. After the reaction is completed, conventional drying can be carried out. The present invention uses gel containing sodium dodecyl sulfate to be immersed in ultrapure water, which generates a surface tension gradient to drive the microspheres on the liquid surface to move, so that the microspheres on the liquid surface form a tightly arranged, single-layer structure.

[0054] In some embodiments, in step S1, the volume of the microsphere dispersion, the cross-sectional area of ​​the container, and the volume of ultrapure water therein can be flexibly adjusted according to actual conditions (such as the area of ​​the silicon wafer, etc.).

[0055] In some embodiments, in step S2, the conditions for etching the self-assembled mask by ICP etching include: the upper electrode power is 30-500W, the lower electrode power is 5-100W, the pressure is 1-50Pa, the etching gas is Ar and / or O2, the etching gas flow rate is 10-150sccm, and the etching time is 30-300s.

[0056] In some embodiments, in step S3, the conditions for etching the patterned mask by ICP etching include: the upper electrode power is 100-1500W, the lower electrode power is 5-50W, the pressure is 1-50Pa, C4F8 gas is used as the passivation gas, and SF6 gas is used as the etching gas, and the two are alternately cycled for several times. Preferably, in a single cycle, the C4F8 gas flow rate is 10-200sccm, the passivation time is 5-50s, the SF6 gas flow rate is 10-200sccm, and the etching time is 5-50s. Preferably, the number of said several cycles is 10-300 times.

[0057] In some embodiments, step S4 includes: immersing the masked micro-nano needle tip array in ultrapure water for ultrasonic cleaning to remove the mask, thereby obtaining the high aspect ratio micro-nano needle tip array based on the self-assembled mask. The time, power and frequency of the ultrasonic cleaning can be conventionally adjusted by those skilled in the art.

[0058] In some embodiments, the preparation method can prepare a high aspect ratio micro-nano needle tip array based on a self-assembled mask on a large area, and the range of the large area is 1 cm 2 -1000cm 2 .

[0059] According to a specific embodiment of the second aspect of the present invention, the present invention provides a high aspect ratio micro-nano needle tip array based on a self-assembled mask, which is prepared by the above-mentioned preparation method.

[0060] In some embodiments, the high aspect ratio micro-nano tip array based on the self-assembled mask has an aspect ratio of 1:5 to 10:1.

[0061] In some embodiments, the diameter of the top end of the needle tip in the high aspect ratio micro-nano needle tip array based on the self-assembled mask is 10-30 nm, and the diameter of the bottom end of the needle tip is 50 nm-5 μm.

[0062] In some embodiments, the spacing between the bottom ends of two adjacent tips in the high aspect ratio micro-nano tip array based on the self-assembled mask is 100 nm-10 μm.

[0063] The technical solutions of the present invention are specifically described below by way of examples, but the present invention is not limited to these examples and can of course be implemented in various modifications within the scope of the gist of the present invention.

[0064] Example 1

[0065] S0: Pre-processing of silicon wafers

[0066] Take a thickness of 500 μm and an area of ​​6.25 cm2 A square cut piece of silicon wafer with a (100) crystal plane is placed in acetone and ultrasonically cleaned for 3 minutes; then placed on a hot plate and baked at 200° C. for 5 minutes to obtain a pretreated silicon wafer;

[0067] S1: Preparation of large-area self-assembled masks

[0068] The microsphere self-assembly system was used, such as Figure 1 As shown, the system includes: a needle tube 1, an injection pump 2 connected to one end of the needle tube 1, a hose 3 connected to the other end of the needle tube 1, and a container 4; the container 4 is an open cylindrical container, which can be made of plastic and has a cross-sectional diameter of 15 cm; it should be noted that Figure 1 Other conventional components are also shown, such as a bracket, a display, etc., and the present invention does not impose any special restrictions on these components;

[0069] Polystyrene (PS) microspheres with a diameter of 900 nm were added to an ethanol / water mixture and ultrasonically dispersed for 10 min to obtain 200 μl of polystyrene microsphere dispersion, in which the concentration of polystyrene microspheres was 1×10 9 Pieces / ml;

[0070] The dispersion of polystyrene microspheres is extracted by a needle tube 1; 200 ml of ultrapure water is placed in a container; one end of the needle tube 1 is connected to an injection pump 2 and the other end is connected to a hose 3; after the liquid surface of the ultrapure water is stable, the hose 3 is overlapped to the liquid surface of the ultrapure water in the container 4; the dispersion of polystyrene microspheres is injected into the liquid surface of the ultrapure water in the container 4 at a speed of 200 μl / min by using the injection pump 2, the needle tube 1 and the hose 3, so that the dispersion of polystyrene microspheres is evenly dispersed to the liquid surface of the ultrapure water; on one side of the ultrapure water, a gel containing sodium dodecyl sulfate is immersed in the liquid surface for 10 seconds; the volume of the gel containing sodium dodecyl sulfate is about 5 cm 3 The preparation method is as described above, wherein the polystyrene microspheres on the surface of the ultrapure water are formed into a tightly arranged, single-layer structure; the pretreated silicon wafer (with the (100) crystal surface facing upward) is tiltedly immersed in the liquid and placed below the liquid surface, and then taken out tiltedly upward at an angle of 30° to the liquid surface, and the tightly arranged, single-layer self-assembled polystyrene microspheres are transferred to the surface of the silicon wafer, and after standing and drying, the self-assembled mask is obtained; the arrangement of the self-assembled mask is as shown in Figure 2 As shown, it can be seen that the polystyrene microspheres are closely arranged and a single layer structure is formed on the surface of the pre-treated silicon wafer;

[0071] S2: Preparation of patterned mask

[0072] like Figure 3As shown, the self-assembled mask is etched using an ICP device (SINTECH_SI500), and the etching conditions include: the upper electrode power is 200W, the lower electrode power is 50W, the pressure is 3Pa, the etching gas is O2, the etching gas flow rate is 40sccm, and the etching time is 40s to obtain a patterned mask;

[0073] S3: Preparation of micro-nano tip arrays

[0074] like Figure 3 As shown, the patterned mask is etched by an ICP device (SINTECH_SI500), and the etching conditions include: the upper electrode power is 500W, the lower electrode power is 15W, the pressure is 7Pa, C4F8 gas is used as the passivation gas, and SF6 gas is used as the etching gas, and the two are cycled alternately; in a single cycle, the C4F8 gas flow rate is 100sccm, the passivation time is 12s, the SF6 gas flow rate is 15sccm, and the etching time is 9s. After 100 cycles, a micro-nano needle tip array containing a mask is obtained;

[0075] S4: Mask removal

[0076] The masked micro-nano needle tip array is immersed in ultrapure water and ultrasonically cleaned for 3 minutes to remove the mask, thereby obtaining a high aspect ratio micro-nano needle tip array based on a self-assembled mask.

[0077] Electron microscopy examination revealed Figure 4 As shown, the aspect ratio of the micro-nano needle tip array is 6:1, the diameter of the top end of the needle tip is 10 nm, the diameter of the bottom end of the needle tip is 500 nm, and the distance between the bottom ends of two adjacent needle tips is 900 nm.

[0078] Example 2

[0079] Using the pretreated silicon wafer in Example 1;

[0080] S1: Preparation of large-area self-assembled masks

[0081] Polystyrene (PS) microspheres with a diameter of 1200 nm were added to an ethanol / water mixture and ultrasonically dispersed for 10 min to obtain 200 μl of polystyrene microsphere dispersion, in which the concentration of polystyrene microspheres was 1×10 9 The remaining steps of preparing the self-assembly mask are the same as those in Example 1;

[0082] S2: Preparation of patterned mask

[0083] like Figure 3As shown, the self-assembled mask is etched using an ICP device (SINTECH_SI500), and the etching conditions include: the upper electrode power is 200W, the lower electrode power is 50W, the pressure is 3Pa, the etching gas is O2, the etching gas flow rate is 40sccm, and the etching time is 40s to obtain a patterned mask;

[0084] S3: Preparation of micro-nano tip arrays

[0085] like Figure 3 As shown, the patterned mask is etched by an ICP device (SINTECH_SI500), and the etching conditions include: the upper electrode power is 500W, the lower electrode power is 15W, the pressure is 7Pa, C4F8 gas is used as the passivation gas, and SF6 gas is used as the etching gas, and the two are cycled alternately; in a single cycle, the C4F8 gas flow rate is 100sccm, the passivation time is 11s, the SF6 gas flow rate is 15sccm, and the etching time is 10s. After 80 cycles, a micro-nano needle tip array containing a mask is obtained;

[0086] S4: Mask removal

[0087] The masked micro-nano needle tip array is immersed in ultrapure water and ultrasonically cleaned for 3 minutes to remove the mask, thereby obtaining a high aspect ratio micro-nano needle tip array based on a self-assembled mask.

[0088] Electron microscopy examination revealed Figure 5 As shown, the aspect ratio of the micro-nano needle tip array is 4:1, the diameter of the top end of the needle tip is 10 nm, the diameter of the bottom end of the needle tip is 500 nm, and the distance between the bottom ends of two adjacent needle tips is 900 nm.

[0089] Example 3

[0090] Using the pretreated silicon wafer in Example 1;

[0091] S1: Preparation of large-area self-assembled masks

[0092] Polystyrene (PS) microspheres with a diameter of 1500 nm were added to an ethanol / water mixture and ultrasonically dispersed for 10 min to obtain 200 μl of polystyrene microsphere dispersion, in which the concentration of polystyrene microspheres was 1×10 9 The remaining steps of preparing the self-assembly mask are the same as those in Example 1;

[0093] S2: Preparation of patterned mask

[0094] like Figure 3As shown, the self-assembled mask is etched using an ICP device (SINTECH_SI500), and the etching conditions include: the upper electrode power is 200W, the lower electrode power is 50W, the pressure is 3Pa, the etching gas is O2, the etching gas flow rate is 40sccm, and the etching time is 40s to obtain a patterned mask;

[0095] S3: Preparation of micro-nano tip arrays

[0096] like Figure 3 As shown, the patterned mask is etched by an ICP device (SINTECH_SI500), and the etching conditions include: the upper electrode power is 500W, the lower electrode power is 15W, the pressure is 7Pa, C4F8 gas is used as the passivation gas, and SF6 gas is used as the etching gas, and the two are cycled alternately; in a single cycle, the C4F8 gas flow rate is 100sccm, the passivation time is 10s, the SF6 gas flow rate is 15sccm, and the etching time is 10s. After 60 cycles, a micro-nano needle tip array containing a mask is obtained;

[0097] S4: Mask removal

[0098] The masked micro-nano needle tip array is immersed in ultrapure water and ultrasonically cleaned for 3 minutes to remove the mask, thereby obtaining a high aspect ratio micro-nano needle tip array based on a self-assembled mask.

[0099] Electron microscopy examination revealed Figure 6 As shown, the aspect ratio of the micro-nano needle tip array is 3:1, the diameter of the top end of the needle tip is 10 nm, the diameter of the bottom end of the needle tip is 500 nm, and the distance between the bottom ends of two adjacent needle tips is 900 nm.

Claims

1. A method for preparing a high aspect ratio micro-nano needle tip array based on a self-assembled mask, comprising the following steps: S1: forming tightly packed self-assembled microspheres on the surface of silicon wafer to obtain a self-assembled mask; S2: etching the self-assembled mask by ICP etching to obtain a patterned mask; S3: etching the patterned mask by ICP etching to obtain a micro-nano needle tip array containing the mask; S4: removing the mask from the micro-nano needle tip array containing the mask to obtain the high aspect ratio micro-nano needle tip array based on the self-assembled mask.

2. The preparation method according to claim 1, wherein Step S1 includes: extracting a dispersion of microspheres using a needle; placing ultrapure water in a container; connecting one end of the needle to a syringe pump and the other end to a hose, overlapping the hose to the liquid surface of the ultrapure water in the container, and injecting the dispersion of microspheres into the liquid surface of the ultrapure water in the container using the syringe pump, the needle and the hose; immersing a gel containing sodium dodecyl sulfate into ultrapure water from one side of the liquid surface edge for 1-60 seconds to form a tightly arranged structure of microspheres on the liquid surface; placing a silicon wafer below the liquid surface, and then taking it out by tilting it upward at an angle greater than 0° and less than 60° to the liquid surface, transferring the tightly arranged self-assembled microspheres to the surface of the silicon wafer, and obtaining the self-assembled mask after drying.

3. The preparation method according to claim 1 or 2, wherein In step S1, the microspheres include one or a combination of polystyrene microspheres, silica microspheres, polymethyl methacrylate microspheres and polyvinyl alcohol microspheres.

4. The preparation method according to claim 1 or 2, wherein: In step S1, the diameter of the microspheres is 50 nm-10 μm.

5. The preparation method according to claim 2, wherein: In step S1, the dispersion of microspheres is injected into the liquid surface of ultrapure water in the container at an injection speed of 10-500 μl / min.

6. The preparation method according to claim 1 or 2, wherein: In step S1, closely arranged self-assembled microspheres are formed on the surface of the silicon wafer as a single layer of microspheres.

7. The preparation method according to claim 1, wherein In step S2, the conditions for etching the self-assembled mask by ICP etching include: upper electrode power is 30-500W, lower electrode power is 5-100W, pressure is 1-50Pa, etching gas is Ar and / or O2, etching gas flow rate is 10-150sccm, and etching time is 30-300s.

8. The preparation method according to claim 1, wherein In step S3, the conditions for etching the patterned mask by ICP etching include: upper electrode power is 100-1500W, lower electrode power is 5-50W, pressure is 1-50Pa, C4F8 gas is used as passivation gas, SF6 gas is used as etching gas, and the two are alternately cycled for several times.

9. The preparation method according to claim 8, wherein: In step S3, in a single cycle, the C4F8 gas flow rate is 10-200 sccm, the passivation time is 5-50 s, the SF6 gas flow rate is 10-200 sccm, and the etching time is 5-50 s.

10. The preparation method according to claim 8, wherein: In step S3, the number of the several cycles is 10-300 times.

11. The preparation method according to claim 1, wherein: Step S4 includes: immersing the micro-nano needle tip array containing the mask in ultrapure water for ultrasonic cleaning to remove the mask and obtain the micro-nano needle tip array with high aspect ratio based on the self-assembled mask.

12. A high aspect ratio micro-nano needle tip array based on a self-assembled mask, which is prepared by the preparation method according to any one of claims 1 to 11.

13. The high aspect ratio micro-nano needle tip array based on self-assembled mask according to claim 12, wherein: The aspect ratio of the high aspect ratio micro-nano needle tip array based on the self-assembled mask is 1:5 to 10:

1.

14. The high aspect ratio micro-nano needle tip array based on self-assembled mask according to claim 12, wherein: The diameter of the top end of the needle tip in the high aspect ratio micro-nano needle tip array based on the self-assembled mask is 10-30 nm, and the diameter of the bottom end of the needle tip is 50 nm-5 μm.

15. The high aspect ratio micro-nano needle tip array based on self-assembled mask according to claim 12, wherein: The spacing between the bottom ends of two adjacent needle tips in the high aspect ratio micro-nano needle tip array based on the self-assembled mask is 100nm-10μm.

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