CN101475173A - Method for preparing super-hydrophobic antireflex micron and nano composite structure surface - Google Patents

Abstract

The invention belongs to the technical field of preparation of composite structure surfaces, and in particular relates to a method for preparing superhydrophobic anti-reflection silicon surfaces of micron and nanometer composite structures. Including cleaning of silicon wafers, making micron-scale silicon islands and grid structures on the surface of silicon wafers, catalytic etching with silver or gold nanoparticles as barriers, obtaining micro- and nano-composite structure surfaces, and chemically performing composite structure surfaces modification steps. The static contact angle between the surface of the superhydrophobic anti-reflection material prepared by the method of the invention and water is greater than 150°, and the static rolling angle of water is less than 3°. The surface has excellent anti-reflection performance, especially the light reflectance in the wavelength range of 800nm to 1100nm is less than 3%. By applying the method of the invention, the superhydrophobic anti-reflection silicon surface of the micro-nano composite structure can be produced on a large scale, and can be widely used in solar cells, microfluidic chips, photoelectric devices, etc., and has good industrial application prospects.

Description

A method for preparing superhydrophobic antireflective micron and nanocomposite structure surfaces

technical field

The invention belongs to the technical field of preparation of composite structure surfaces, and in particular relates to a method for preparing superhydrophobic anti-reflection silicon surfaces of micron and nanometer composite structures.

Background technique

In recent years, countries all over the world have given great enthusiasm and attention to MEMS. It is becoming a new large-scale industry, a new growth point of the national economy, and has a significant impact on the development of national defense technology. However, with the miniaturization of devices and systems, the characteristic scale decreases, the ratio of surface area (L ² ) to volume (L ³ ) increases relatively, and the surface effect increases. The leading role, resulting in a series of problems such as surface friction, wear, adhesion and pressure loss, which makes (MEMS) devices suffer greatly.

A superhydrophobic surface generally refers to a surface with a contact angle with water greater than 150°. It has special wetting properties, has important characteristics such as waterproof, anti-fog, anti-cleaning, and anti-oxidation. It has broad application prospects in many fields such as scientific research, production, and life, such as lenses, optical devices, textiles, and mechanical products. , pipeline transportation, microfluidic chips, etc. This type of special property can reduce the adhesion and friction of the device surface and improve the flow performance of liquid in the microfluidic device. Yasuhisa Ando of the Mechanical Engineering Laboratory of the University of Tsukuba in Japan published in Sensors and Actuators, Vol.57No.2 (1996), p, 83-89 and V.Studer of France published in AppI.Phys.Lett.80, 3614 (2002) The application of superhydrophobic surfaces was tentatively studied in the thesis. There are two main methods for superhydrophobic modification of the surface of solid materials: one is to construct rough micro-nano structures on the hydrophobic surface with a contact angle greater than 90°; the other is to modify the surface with low surface energy substances, such as Jiang Lei Published in Adv. Mater. 2002, 14: 1857-180 explained. There have also been some reports on the hydrophobic modification of solid surfaces combining the above two methods. For example (Chinese patents, publication numbers CN1378581A, CN1613565A, CN1624062A), Langmuir2008, 24, 10421-10426. However, some of the above-mentioned methods for constructing superhydrophobic surfaces generally have complicated processes and require special instruments and equipment, making it difficult to realize large-scale preparation. Therefore, it is more valuable to explore new and cheap superhydrophobic preparation technologies.

Due to the high reflectivity of ordinary planar substrates, the optical system is disturbed by stray light, which seriously affects the transmittance and image resolution capabilities of the optical components in the optical system, resulting in a decrease in the resolution and sensitivity of the optical system, which seriously affects the Performance of optical and optoelectronic devices, such as solar cells, displays, optical sensors, polarizers, optical lenses, etc. In order to improve the performance of these devices, it is necessary to reduce the reflectivity of the substrate surface to light. Traditional methods for constructing anti-reflective subwavelength surface structures mainly include: electron beam etching, dry etching based on nanoimprinting, laser interference etching, etc. In order to build anti-reflection surfaces, scientific and technological workers have carried out a lot of research work, the most influential of which is the method of electron beam etching (Opt.Lett.1999, 24, 1422; Microeletron.Eng.2005, 78～79,287) . Although the method of electron beam etching has the advantages of high precision and high resolution, its wide application is restricted due to the disadvantages of expensive equipment and low efficiency. Based on the structure prepared by the self-assembled nanoparticle method, laser interference etching and nanoimprinting mask, RIE can construct a sub-wavelength structure with anti-reflection properties on a large area (Nanotechnology 2000.11.161; Nanotechnology 1997.8.53 ; AppI.Phys.Lett.2002.80.2242; J.Vac.Sci.Tehchnol.2003.21.287 4Small 2008.4.1972 Chinese patent, publication number CN1378581A, CN1613565 A, CN1624062 A), but the instrument that these technologies need is still very expensive, Its application is severely limited.

Contents of the invention

The purpose of the present invention is to prepare a large-area super-hydrophobic anti-reflective silicon surface in a simple method, and proposes a method for preparing a super-hydrophobic anti-reflective silicon surface with a micron and nanocomposite structure. The present invention utilizes the anisotropic etching effect of single crystal silicon in alkaline solution and the silver-catalyzed silicon etching method to prepare a composite structure in which the surface microstructure is co-existed with micron and nanostructures, and then through the fluorine-containing silylating agent The surface is chemically modified, and the prepared silicon surface has good superhydrophobic and antireflection properties at the same time. The static contact angle between the surface of the superhydrophobic anti-reflective material prepared by this method and water is greater than 150°, as shown in Figure 7, the sliding angle of water droplets on this surface is less than 3° (both the static contact angle and the rolling angle are within contact angle OCA20.DATAPHYSICS on the test). The surface also has good anti-reflection performance, especially the light reflectance is less than 3% in the wavelength range of 800-1100nm.

The method of the present invention has the advantages of simple operation, good universality, low cost, large area, fast and high efficiency, etc., and provides a new preparation method for expanding the application of silicon materials in industrial production, and can produce micro The superhydrophobic anti-reflective silicon surface of the nanocomposite structure can be widely used in solar cells, microfluidic chips, optoelectronic devices, etc., and has good industrial application prospects.

In order to realize the preparation of superhydrophobic anti-reflection micro-nano composite structure silicon surface, the scheme adopted in the present invention is to build micron and nanostructures on the silicon surface successively, wherein the height of micron-scale silicon islands or grids (obtained as a grid structure by photolithography method) The diameter of the nanohole is about 80-140nm.

The method for preparing the superhydrophobic anti-reflection silicon surface of the micron and nanocomposite structure of the present invention, comprises the steps:

(1) Select silicon wafers of n-100, p-100, n-111, p-111 and other crystal forms, and clean the surface. Ultrasonic cleaning in water, the ultrasonic power is 50-150W, the time is 1-10min, and then the silicon wafer is put into the HF solution with a mass fraction of 1-10% for 5-10min to remove the silicon dioxide on the surface, and finally deionized Wash with water, then blow dry with high-purity nitrogen;

(2) Form micron-scale silicon islands or grids on the surface of the silicon wafer by alkaline solution etching, RIE etching, photolithography or nanoimprinting;

The method of alkali solution etching described in the above-mentioned method is to put the silicon chip after cleaning into pH 10～14 40 ℃～110 ℃ KOH, NaOH, EDP (ethylenediamine, pyrocatechol and water) mixed solution) and ammonia solution for 0.5-3 hours, due to the anisotropic etching effect of the alkaline solution on silicon, micron-sized silicon islands are prepared on the silicon surface, and the height of the silicon islands is 5-7 μm;

The RIE etching method described in the above method is to transfer the array of PS spheres with a single layer of close hexagonal packing on the water surface to the cleaned silicon surface, and then use the obtained sample to prepare the silicon island microstructure by RIE etching. , the etching gas is SF ₆ (20-45sccm) and CHF ₃ (3-12sccm), the etching power is 80-160W, the chamber pressure is 25-60mTorr, and the etching time is 300-1000s. The obtained micron-sized silicon islands , the scanning electron microscope photo is shown in Figure 4, the height of the silicon island is 1.0 ~ 3.0 μm.

The photolithography method described in the above method is to select the cleaned silicon wafer as the base material, and process it through an oxygen plasma system for 2 to 8 minutes before use to make the surface clean and hydrophilic, which is convenient for the spin coating of the photoresist. membrane. The conditions for spin-coating the photoresist are: 1000-2500 revolutions/S, spin for 15-60S, and quench the sample at 80-100° C. for 25-45 minutes after the spin-coating is completed. Then control the exposure current 3.5A under the mask exposure machine, expose for 40s, develop in the developer solution (BP~212 UV positive photoresist developer) for 1-3s after exposure, and wash the remaining developer solution in distilled water , blown dry with nitrogen to obtain a photoresist micro-grid structure with a microstructure period of 10 μm, a hole of 5 μm, and a strip width of 5 μm. Then the obtained sample is etched by RIE to prepare a micron-scale silicon grid structure, the etching gas is SF ₆ (20-45 sccm) and CHF ₃ (3-12 sccm), the etching power is 80-160W, and the chamber pressure 25-60 mTorr, the etching time is 600-1500 s, and the height of the prepared micron-scale silicon grid is 3-6 μm.

The method for nanoimprinting described in the above-mentioned method is to get a small amount of thermoplastic polymer MRI～7030 (Micro Resist company, Germany) or polymethyl methacrylate PMMA to spin-coat on the silicon chip surface after cleaning , the spin-coating thickness is about 200-500nm, using a 2.5-inch nano-imprinting machine produced by Sweden's OBDUCAT company, using a template of silicon nitride material (constructed by electron beam etching, a lattice structure, the size of the dots The range is 800nm×800nm～10μm×10μm, and the pitch size of the dots ranges from 800nm～10μm) to build an ordered structure complementary to the polymer and template structure, that is, to use the nanoimprint method to build a micron-scale structure on the surface of the substrate. Then use oxygen plasma to remove the polymer layer between the lattices to expose the surface of the silicon wafer, and then use the polymer of the lattice structure as a barrier layer to prepare micron-scale silicon islands by RIE etching with the obtained sample. The etching gas is For SF ₆ (20-45sccm) and CHF ₃ (3-12sccm), the etching power is 80-160W, the chamber pressure is 25-60mTorr, the etching time is 500-1500s, and the height of the obtained silicon island is 2-4.5μm.

(3) Deposit gold or silver nano ions on the surface of micron-scale silicon islands or grid structures by electroless deposition, electrodeposition or chemical vapor deposition, and the thickness of the deposited gold or silver nanoparticles is 5-15 nm; Then put the micron-scale silicon island or the silicon chip on the surface of the grid structure into the HF/H ₂ O ₂ /H ₂ O solution (the mass fraction is 40-60% HF, the mass fraction is 20-40% H ₂ The volume ratio of O ₂ and H ₂ O is 1-3:5-8:10-15, and the catalytic etching is carried out to prepare nano-scale holes. Or gold nanoparticles are washed away, and then the surface of complex rice and nanocomposite structure is obtained;

The electroless deposition method described in the above method is to put the silicon chip with micron-scale silicon islands or grids on the surface into the mixed solution of 4~5M HF and 0.01~ _0.02MAgNO3 , and electrolessly deposit silver For nanoparticles, the deposition time is 1 to 4 minutes;

The method of electrodeposition described in the above method is to put the silicon wafer with micron-scale silicon islands or grids on the surface into the electrolyte solution _AgNO3 of 0.01-0.05M, the deposition voltage is 400-800mv, and the deposition time is 10-20min; or put the silicon wafer with micron-scale silicon islands or grids on the surface into the 0.01-0.05M electrolyte chloroauric acid, the deposition voltage is 500-700mv, and the deposition time is 8-20min;

(4) Chemically modify the surface of the prepared micro- and nano-scale structures: put the obtained silicon wafers on the surface of the micro- and nano-composite structures into a clean glass petri dish, drop 0.5 to 1.0 ml of fluoride on the bottom of the petri dish Silylating agents, such as heptadecylfluorodecyltrimethoxysilane, perfluorooctanesulfonic acid (PFOS), perfluorodecyltriethoxysilane (PFDTES), dodecyltrichlorosilane (DTS), Octalkyltrichlorosilane (ODTS), perfluorooctylmethyldichlorosilane (TFPS), etc., heated to 100-350°C for 1-3.5h, and then cooled to room temperature, so that micro and nano composite structures can be obtained superhydrophobic antireflective silicon surface.

The super-hydrophobic anti-reflection silicon surface of the micro-nano composite structure prepared by the invention has many advantages and good applications.

(1) The process of the method is simple, cheap, highly universal and easy to produce;

(2) The present invention does not require any template, and can realize large-area preparation, see FIG. 9 .

(3) The surface of the micro-nano composite structure of the present invention has a very large contact angle (greater than 150°), and a very small contact angle hysteresis (less than 3°), and the dust on the surface can be taken away by water droplets to realize self-cleaning ;

(4) The super-hydrophobic surface has the function of non-stick water and self-cleaning, and can be used in some drag-reducing components in microelectronic and micro-mechanical systems to reduce noise, reduce friction and prevent corrosion;

(5) Low surface energy and super-hydrophobic properties can reduce the pressure loss along the microfluidic channel, increase the flow velocity of the fluid, and can be used for the lossless delivery of ultra-micro liquid in the microfluidic chip;

(6) The silicon surface of the micro-nano composite structure has anti-reflection properties, and can be widely used in solar cells, optoelectronic devices, and the like.

Description of drawings

Figure 1: Schematic diagram of the process for preparing superhydrophobic anti-reflective silicon surfaces with micro- and nano-composite structures;

Figure 2: SEM picture of the prepared silicon island structure;

Figure 3: SEM image of PS spheres with a diameter of 1.1 μm arranged in a single layer on the surface of a silicon wafer;

Figure 4: SEM images of silicon islands obtained by RIE etching silicon with PS balls with a diameter of 1.1 μm as the barrier layer;

Figure 5: SEM image after electroless deposition of silver nanoparticles on the surface of the silicon island;

Figure 6: SEM picture of the prepared micro-nano composite structure;

Figure 7: CCD photo for measuring contact angle;

Figure 8: Reflectance spectrum curve;

Figure 9: A digital camera photo (right) of the prepared superhydrophobic antireflective silicon surface of a large-area micro-nano composite structure and a comparative photo of the corresponding silicon wafer (left).

As shown in Figure 1, the n-100 type silicon wafer is first selected, and its surface is cleaned. Then put it into a KOH solution with a pH of 14 and 60° C. for 1 hour to obtain a micron silicon island structure on the silicon surface. Gold or silver nanoparticles are then deposited on the surface of the silicon island structures. Finally, micro- and nano-composite structures are prepared by catalytic etching of gold or silver.

As shown in FIG. 2 , the prepared silicon island structure has a bottom side length of 4-6 μm and a height of 5-7 μm. Concrete preparation process is referring to embodiment 1

As shown in Figure 3, the single layer of PS spheres on the water surface was transferred to the silicon surface, and the array of PS spheres was detected by a scanning electron microscope. It can be seen from the SEM image that we have prepared an array structure of closely packed hexagonal PS spheres . See embodiment 6 for the specific process.

As shown in Figure 4, the obtained sample with a diameter of 1.1 μm PS spheres arranged in a single layer on the surface of a silicon wafer was etched by RIE to prepare a silicon island microstructure, and the etching gas was SF ₆ (30 sccm) and CHF ₃ ( 6 sccm) (SF ₆ :CHF ₃ =5:1), the etching power is 100W, the cavity pressure is 30mTorr, and the etching time is 710s. See embodiment 6 for the specific process.

As shown in Figure 5, a layer of metal silver nanoparticles is evenly deposited on the surface of the silicon island, and the particle size of the nanoparticles is about 100nm. Therefore, the size of the nanopores obtained by the next step of catalytic etching is also 100nm. about. The picture shows two silicon islands. The lower right corner is the tip of one of the silicon islands, and the back is a side of the silicon island. It can be seen that a layer of nanoparticles is evenly deposited on it. See embodiment 1 for the specific process.

As shown in Figure 6, for the prepared micro-nano composite structure, we can see that the structure of the micro-island remains intact after etching, and a nano-hole structure of about 100nm is prepared on the surface of the island by etching, realizing the realization of micro-nano Composite structure. See embodiment 1 for the specific process.

As shown in Figure 7, in the CCD photo of the contact angle, the edge profile of the water droplet is not very clear, because the rolling angle of the prepared structure is very small, and the water droplet is rolling, which also shows that the structure we prepared has very good superhydrophobicity Effect. See embodiment 1 for the specific process.

As shown in FIG. 8 , it is a reflection spectrum curve, and curve a is the reflection spectrum curve of a nanoscale structure obtained by directly depositing silver nanoparticles on the surface of a silicon wafer without a silicon island structure, and then catalytically etching. Curve b is the reflection spectrum curve of the micro-nano composite structure prepared by us, which has good anti-reflection effect in the entire measured wavelength range, especially in the wavelength range of 800-1100nm, and its reflectance is lower than 3%. Curve c is the reflectance spectrum curve of a pure silicon wafer, and its reflectivity is 40%. Curve d is the reflection spectrum curve of the silicon island structure. See embodiment 1 for the specific process.

As shown in Figure 9, it is a digital camera photo of the micro-nano composite structure prepared on the entire silicon wafer. It can be seen from the photo that our structure has no major defects and is suitable for large-area processing.

Detailed ways

Example 1:

(1) Select n-100 type silicon wafer and clean its surface. The treatment process is as follows: ultrasonically clean the silicon wafer in acetone, chloroform, ethanol, and water respectively, with an ultrasonic power of 100W for 5 minutes. Then put the silicon chip into the HF solution with a mass fraction of 1% for 5 minutes to remove the silicon dioxide on the surface, and finally wash it with deionized water and dry it with high-purity nitrogen gas.

(2) Prepare micron-scale silicon island structures on the silicon surface. The process is as follows: put the cleaned silicon wafer into a KOH solution at 60°C with a pH of 14 for 1 hour, and silicon is etched anisotropically in the alkaline solution. , thereby preparing a silicon island structure on the silicon surface, the bottom side of the silicon island is 4-6 μm long, and the height is 5-7 μm. as shown in picture 2.

(3) To prepare nanoscale pores on the surface of micron-scale silicon islands, first place the silicon wafer with silicon islands on the surface into a mixed solution of 4.6M HF and 0.01M _AgNO3 , and electrolessly deposit silver nanoparticles 1 minutes, as shown in Figure 5. Then put the silicon island structure with silver nanoparticles on the surface into the mixed solution of HF/H ₂ O ₂ /H ₂ O (the mass fraction is 49% HF, the mass fraction is 30% H ₂ O ₂ , and The volume ratio of H ₂ O is 1:5:10), and the catalytic etching is performed for 30s to prepare nanoscale holes. Finally, the silver nanoparticles were washed away by soaking in nitric acid with a mass fraction of 30% for 5 minutes, as shown in FIG. 6 .

(4) Chemically modify the surface of the prepared structure, put the obtained micro-nano composite structure into a clean glass petri dish, drop 0.5ml of heptadecafluorodecyltrimethoxysilane at the bottom of the petri dish, heat to 250 ℃, keep 2.5h, then cool to room temperature. The measured surface contact angle is 156°, as shown in Figure 7. The reflectivity is lower than 5%, as shown in Figure 8.

Example 2:

According to the method and steps of Example 1, the electroless deposition of silver nanoparticles is changed to electrodeposition, the electrolyte is 0.01M _AgNO solution, the deposition voltage is 400mv, and the deposition time is 15min. Other steps are the same as in Example 1, and can be The super-hydrophobic anti-reflective silicon surface is obtained, the height of the silicon island of the prepared structure is 5-7 μm, the size of the nanoscale hole is about 130 nanometers, the contact angle is 153°, and the reflectivity is lower than 8%.

Example 3:

According to the method and steps of Example 1, the electroless deposition of silver nanoparticles is changed to electrodeposition of gold nanoparticles, the electrolyte is 0.01M chloroauric acid solution, the deposition voltage is 500mv, and the deposition time is 10min. Other steps are the same as in the embodiment. 1. The superhydrophobic anti-reflective silicon surface can also be obtained. The height of the silicon island of the prepared structure is 5-7 μm, the size of the nanoscale hole is about 120 nanometers, the contact angle is 150°, and the reflectivity is lower than 8%.

Example 4:

According to the method and steps of Example 1, the electroless deposition of silver nanoparticles is changed to chemical vapor deposition, and the thickness of the deposited silver nanoparticles is 5nm. Other steps are the same as in Example 1, and a superhydrophobic antireflective silicon surface can also be obtained. The height of the silicon island of the prepared structure is 5-7 μm, the size of the nanoscale holes is about 100 nanometers, the contact angle is 157°, and the reflectivity is lower than 6%.

Example 5:

According to the method and steps of Example 1, the electroless deposition of silver nanoparticles is changed to chemical vapor deposition of gold nanoparticles, and the thickness of the deposited gold nanoparticles is 5nm. The other steps are the same as in Example 1, and the superhydrophobic antireflection silicon surface can also be obtained. . The height of the silicon island of the prepared structure is 5-7 μm, the size of the nanoscale holes is about 100 nanometers, the contact angle is 158°, and the reflectivity is lower than 6%.

Embodiment 6:

(1) Select n-100 type silicon wafer and clean its surface. The treatment process is as follows: ultrasonically clean the silicon wafer in acetone, chloroform, ethanol, and water respectively, with an ultrasonic power of 100W for 5 minutes. Then put the silicon chip into 1% HF solution for 5 minutes to remove the silicon dioxide on the surface, and finally wash it with deionized water and dry it with high-purity nitrogen gas.

(2) Preparation of micron-scale silicon island structures on the silicon surface, the process is as follows: buy a PS solution with a mass fraction of 10% from Microparticles GmbH (Germany), mix it with ethanol in equal volume, and supercharge for 15 minutes before use. Add 150mL of high-purity water (treated by a French MILLI~Q ultrapure water instrument, with a resistivity of 18.2MΩcm) into a glass petri dish with a diameter of 15cm, and take 5μL of the prepared solution and drop it on the silicon wafer. At this time, the PS microspheres are on the water surface. Disperse to form a disordered structure, wait for 50min and add 5 μL of 2% sodium dodecyl sulfate solution, then the PS balls will form an ordered monolayer array on the water surface, transfer the monolayer PS balls on the water surface to silicon On the surface, a scanning electron microscope was used to examine the array of PS spheres, as shown in Figure 3. It can be seen from the electron microscope images that we have prepared an array structure of closely packed hexagonal PS spheres. Then the obtained sample was etched by RIE to prepare the silicon island microstructure, the etching gas was SF ₆ (30 sccm) and CHF ₃ (6 sccm) (SF ₆ :CHF ₃ =5:1), the etching power was 100W, The cavity pressure is 30mTorr, and the etching time is 380s. The scanning electron microscope picture of the obtained silicon island microstructure is shown in FIG. 4 . The silicon island height of the fabricated structure was 1 μm.

(3) To prepare nanoscale pores on the surface of micron-scale silicon islands, first put the silicon wafer with silicon islands on the surface into a mixed solution of 4.6M HF and 0.01M _AgNO3 , and electrolessly deposit silver nanoparticles for 1min , and then put the silicon island structure with silver nanoparticles on the surface into the HF/H ₂ O ₂ /H ₂ O solution (the mass fractions are respectively 49% HF, 30% H ₂ O ₂ and the volume of H ₂ O The ratio is 1:5:10), and the catalytic etching is carried out for 30s to prepare nanoscale holes, and finally the silver nanoparticles are washed away by soaking in nitric acid with a mass fraction of 30% for 5min.

(4) Carry out surface chemical modification to the prepared structure, put the obtained micro-nano composite structure into a clean glass petri dish, drop 0.5ml of heptadecafluorodecyltrimethoxysilane at the bottom of the petri dish, heat to 250 ℃, keep 2.5h, then cool to room temperature. The height of the silicon island of the prepared structure is 1 μm, the size of the nanoscale hole is about 100 nanometers, the size of the contact angle is 150°, and the reflectivity is lower than 10%.

Embodiment 7:

According to the method and steps of Example 6, the electroless deposition of silver nanoparticles is changed to electrodeposition, the electrolyte is 0.01M _AgNO solution, the deposition voltage is 400mv, and the deposition time is 15min. Other steps are the same as in Example 6, and can be A superhydrophobic antireflective silicon surface is obtained. The height of the silicon island of the prepared structure is 1 μm, the size of the nanoscale hole is about 130 nanometers, the size of the contact angle is 151°, and the reflectivity is lower than 10%.

Embodiment 8:

According to the method and steps of Example 6, the electroless deposition of silver nanoparticles is changed to electrodeposition of gold nanoparticles, the electrolyte is 0.01M chloroauric acid solution, the deposition voltage is 500mv, and the deposition time is 10min. Other steps are the same as in the embodiment. 6. It is also possible to obtain a super-hydrophobic anti-reflective silicon surface. The height of the silicon island of the prepared structure is 1 μm, the size of the nanoscale hole is about 120 nanometers, the size of the contact angle is 152°, and the reflectivity is lower than 10%.

Embodiment 9:

According to the method and steps of Example 6, the electroless deposition of silver nanoparticles is changed to chemical vapor deposition, and the thickness of the deposited silver nanoparticles is 5nm. Other steps are the same as in Example 6, and a superhydrophobic antireflective silicon surface can also be obtained. The silicon island height of the prepared structure is 1 μm, the size of the nanoscale hole is about 100 nanometers, the contact angle is 154°, and the reflectivity is lower than 8%.

Example 10:

According to the method and steps of Example 6, the electroless deposition of silver nanoparticles is changed to chemical vapor deposition of gold nanoparticles, and the thickness of the deposited gold nanoparticles is 5nm. The other steps are the same as in Example 6, and the superhydrophobic anti-reflective silicon surface can also be obtained. . The silicon island height of the prepared structure is 1 μm, the size of the nanoscale holes is about 100 nanometers, the contact angle is 153°, and the reflectivity is lower than 8%.

Example 11:

(1) Select n-100 type silicon wafers, and clean the surface. The treatment process is as follows: ultrasonically clean the silicon wafer in acetone, chloroform, ethanol, and water respectively, with an ultrasonic power of 100W for 5 minutes. Then put the silicon chip into 1% HF solution for 5 minutes to remove the silicon dioxide on the surface, and finally wash it with deionized water and dry it with high-purity nitrogen gas.

(2) Prepare a micron-scale silicon grid structure on the silicon surface. The process is as follows: select the silicon wafer cleaned above as the base material, and treat it with an oxygen plasma system for 5 minutes before use to make the surface clean and hydrophilic, which is convenient for the photoresist. Spin coating film. The conditions for spin-coating the photoresist are: 1500 rpm/S, spin for 15S, and quench the sample at 80° C. for 30 min after spin-coating. Then control the exposure current 3.5A under the mask exposure machine, expose for 40s, and develop for 3s in the developing solution (BP～212 ultraviolet positive photoresist developing solution) after exposure, put into distilled water to wash the remaining developing solution, and use Blow dry with nitrogen to obtain a photoresist microstructure with a microstructure period of 10 μm, a hole of 5 μm, and a strip of 5 μm. Then the obtained sample is etched by RIE to prepare a silicon grid microstructure, the etching gas is SF ₆ (30 sccm) and CHF ₃ (6 sccm) (SF ₆ :CHF ₃ =5:1), and the etching power is 100W , chamber pressure 30mTorr, etching time 900s,

(3) Prepare nanoscale pores on the surface of the micron-scale silicon grid structure. First, put the silicon wafer with the silicon grid on the surface into a mixed solution of 4.6M HF and 0.01M AgNO ₃ for electroless deposition. silver nanoparticles for 1 minute, then put the silicon grid structure with silver nanoparticles on the surface into HF/H ₂ O ₂ /H ₂ O solution (49% HF, 30% H ₂ O ₂ and H ₂ O The volume ratio is 1:5:10), and the catalytic etching is carried out for 30s to prepare nanoscale holes. Finally, the silver nanoparticles were washed away with nitric acid.

(4) Carry out surface chemical modification to the prepared structure, put the obtained micro-nano composite structure into a clean glass petri dish, drop 0.5ml of heptadecafluorodecyltrimethoxysilane at the bottom of the petri dish, heat to 250 ℃, keep 2.5h, then cool to room temperature. The silicon grid height of the prepared structure is 3 μm, the size of the nanoscale holes is about 100 nanometers, the contact angle is 155°, and the reflectivity is lower than 7%.

Example 12:

According to the method and steps of Example 11, the electroless deposition of silver nanoparticles is changed to electrodeposition, the electrolyte is 0.01M _AgNO solution, the deposition voltage is 400mv, and the deposition time is 15min. The other steps are the same as in Example 11. A superhydrophobic antireflective silicon surface is obtained. The height of the silicon grid structure of the prepared structure is 3 μm, the size of the nanoscale holes is about 130 nanometers, the size of the contact angle is 153°, and the reflectivity is lower than 8%.

Example 13:

According to the method and steps of Example 11, the electroless deposition of silver nanoparticles is changed to electrodeposition of gold nanoparticles, the electrolyte is 0.01M chloroauric acid solution, the deposition voltage is 500mv, and the deposition time is 10min. Other steps are the same as in the embodiment. 11. The superhydrophobic anti-reflection silicon surface can also be obtained. The height of the silicon grid structure of the prepared structure is 3 μm, the size of the nanoscale holes is about 120 nanometers, the size of the contact angle is 152°, and the reflectivity is lower than 8%.

Example 14:

According to the method and steps of Example 11, the electroless deposition of silver nanoparticles is changed to chemical vapor deposition, and the thickness of the deposited silver nanoparticles is 5nm. Other steps are the same as in Example 11, and a superhydrophobic anti-reflective silicon surface can also be obtained. The height of the silicon grid structure of the prepared structure is 3 μm, the size of the nanoscale hole is about 100 nanometers, the size of the contact angle is 156°, and the reflectivity is lower than 6%.

Example 15:

According to the method and steps of Example 11, the electroless deposition of silver nanoparticles is changed to chemical vapor deposition of gold nanoparticles, and the thickness of the deposited gold nanoparticles is 5nm. The other steps are the same as in Example 11, and the superhydrophobic antireflection silicon surface can also be obtained. . The height of the silicon grid structure of the prepared structure is 3 μm, the size of the nanoscale holes is about 100 nanometers, the size of the contact angle is 155°, and the reflectivity is lower than 7%.

Example 16:

(1) Select n-100 type silicon wafers, and clean the surface. The treatment process is as follows: ultrasonically clean the silicon wafer in acetone, chloroform, ethanol, and water respectively, with an ultrasonic power of 100W for 5 minutes. Then put the silicon chip into 1% HF solution for 5 minutes to remove the silicon dioxide on the surface, and finally wash it with deionized water and dry it with high-purity nitrogen gas.

(2) Spin-coat a small amount of thermoplastic polymer MRI-7030 (Micro Resist, Germany) or polymethyl methacrylate PMMA on the surface of the treated silicon wafer with a spin-coating thickness of about 200-500 nm. Using a 2.5-inch nano-imprinting machine produced by Sweden's OBDUCAT company, a template of silicon nitride material (constructed by electron beam etching, a lattice structure, the size of the dots ranges from 800nm×800nm to 10μm×10μm, The pitch of the dots ranges from 800nm to 10μm) to construct an ordered structure that complements the polymer and the template structure, that is, to construct a micron-scale structure on the surface of the substrate by using the nanoimprint method. Then use oxygen plasma to remove the inter-lattice polymer barrier layer to expose the surface of the silicon wafer, and then the obtained sample is etched by RIE to prepare the silicon island microstructure. The etching gas is SF ₆ (30 sccm) and CHF ₃ (6 sccm ) (SF ₆ :CHF ₃ =5:1), the etching power is 100W, the cavity pressure is 30mTorr, and the etching time is 1000s.

(3) Prepare nanoscale pores on the surface of micron-scale silicon islands. First, put the silicon wafers with silicon islands on the surface into HF/AgNO ₃ (4.6 and 0.01M) solution, and electrolessly deposit silver nanoparticles for 1 minute. Then, put the silicon island structure with silver nanoparticles on the surface into the HF/H ₂ O ₂ /H ₂ O solution (the volume ratio of 49% HF, 30% H ₂ O ₂ and H ₂ O is 1:5 : 10), performing catalytic etching for 30s to prepare nanoscale holes. Finally, the silver nanoparticles were washed away with nitric acid.

(4) Carry out surface chemical modification to the prepared structure, put the obtained micro-nano composite structure into a clean glass petri dish, drop 0.5ml of heptadecafluorodecyltrimethoxysilane at the bottom of the petri dish, heat to 250 ℃, keep 2.5h, then cool to room temperature. The height of the silicon island of the prepared structure is 2.3 μm, the size of the nanoscale hole is about 100 nanometers, the size of the contact angle is 155°, and the reflectivity is lower than 6%.

Example 17:

According to the method and steps of Example 16, the electroless deposition of silver nanoparticles is changed to electrodeposition, the electrolyte is 0.01M _AgNO solution, the deposition voltage is 400mv, and the deposition time is 15min. Other steps are the same as in Example 11, and can be A superhydrophobic antireflective silicon surface is obtained. The silicon island height of the prepared structure is 2.3 μm, the size of the nanoscale hole is about 130 nm, the contact angle is 152°, and the reflectivity is lower than 8%.

Example 18:

According to the method and steps of Example 16, the electroless deposition of silver nanoparticles is changed to electrodeposition of gold nanoparticles, the electrolyte is 0.01M chloroauric acid solution, the deposition voltage is 500mv, and the deposition time is 10min. Other steps are the same as in the embodiment. 11. The superhydrophobic anti-reflection silicon surface can also be obtained. The height of the silicon island of the prepared structure is 2.3 μm, the size of the nanoscale hole is about 120 nm, the size of the contact angle is 150°, and the reflectivity is lower than 7%.

Example 19:

According to the method and steps of Example 16, the electroless deposition of silver nanoparticles is changed to chemical vapor deposition, and the thickness of the deposited silver nanoparticles is 5nm. Other steps are the same as in Example 11, and a superhydrophobic antireflective silicon surface can also be obtained. The height of the silicon island of the prepared structure is 2.3 μm, the size of the nanoscale hole is about 100 nanometers, the size of the contact angle is 154°, and the reflectivity is lower than 6%.

Example 20:

According to the method and steps of Example 16, the electroless deposition of silver nanoparticles is changed to chemical vapor deposition of gold nanoparticles, and the thickness of the deposited gold nanoparticles is 5nm. The height of the silicon island of the prepared structure is 2.3 μm, the size of the nanoscale hole is about 100 nanometers, the size of the contact angle is 155°, and the reflectivity is lower than 7%.

Claims (10)

1. A method for preparing a superhydrophobic anti-reflection silicon surface of a micron and nanocomposite structure, comprising the steps of: (1) select a silicon wafer, and clean its surface; (2) Forming a micron-scale silicon island or grid structure on the surface of the silicon wafer by alkaline solution etching, RIE etching, photolithography or nanoimprinting; (3) Deposit gold or silver nano ions on the surface of micron-scale silicon islands or grid structures by electroless deposition, electrodeposition or chemical vapor deposition, and the thickness of the deposited gold or silver nanoparticles is 5-15 nm; Then put silicon islands or grid-structured silicon wafers into HF/H ₂ O ₂ /H ₂ O solution for catalytic etching to prepare nanoscale holes, and finally soak them in nitric acid with a mass fraction of 30-50% 5-10 minutes to wash away the silver or gold nanoparticles, and then obtain the surface of micron and nanocomposite structures; (4) Put the obtained silicon chip on the surface of the micro- and nano-composite structure into a clean glass petri dish, drop 0.5-1.0ml of fluorosilylating reagent on the bottom of the petri dish, and then heat to 100-350°C for 1-3.5 h, and then cooled to room temperature to obtain a superhydrophobic antireflective silicon surface with micro- and nanocomposite structures. 2. A method for preparing a superhydrophobic anti-reflective silicon surface of a micron and nanocomposite structure as claimed in claim 1, characterized in that: cleaning the surface of the silicon wafer is to wash the silicon wafer in acetone, chloroform, ethanol, Ultrasonic cleaning in water, the ultrasonic power is 50-150W, the time is 1-10min, and then the silicon wafer is put into the HF solution with a mass fraction of 1-10% for 5-10min to remove the silicon dioxide on the surface, and finally deionized Rinse with water, then blow dry with high-purity nitrogen. 3. A method for preparing a superhydrophobic anti-reflective silicon surface of a micron and nanocomposite structure as claimed in claim 1, characterized in that: the method for etching the alkali solution in step (2) is to clean the silicon Put the chip into 40℃～100℃ KOH, NaOH, EDP or ammonia solution with a pH of 10～14 for 0.5～3h. Due to the anisotropic etching effect of the alkaline solution on the silicon, micron-sized particles are prepared on the silicon surface. Silicon island structure, the height of the silicon island is 5-7 μm. 4, a kind of method for preparing the superhydrophobic anti-reflection silicon surface of micron and nanocomposite structure as claimed in claim 1, is characterized in that: the method for the described RIE etching of step (2) is to close monolayer on the water surface The array of hexagonally stacked PS spheres was transferred to the cleaned silicon surface, and then the obtained sample was etched by RIE to prepare the silicon island microstructure. The etching gas was SF ₆ and CHF ₃ , and the flow rate of SF ₆ was 20 ~45sccm, the flow rate of CHF ₃ is 3~12sccm, the etching power is 80~160W, the cavity pressure is 25~60mTorr, the etching time is 300~1000s, and the height of the obtained silicon island is 1.0~3.0μm. 5. A method for preparing a superhydrophobic anti-reflective silicon surface of a micron and nanocomposite structure as claimed in claim 1, characterized in that: the photolithography method described in step (2) is to use a cleaned silicon wafer as The substrate material is treated with an oxygen plasma system for 2-8 minutes, then quenched after spin-coating photoresist, then exposed under a mask exposure machine, and then developed in a developer, washed with distilled water and dried with nitrogen, that is, on silicon The microstructure of the photoresist is obtained on the chip; finally, the obtained silicon wafer is etched by RIE to prepare the silicon grid microstructure, and the height of the prepared silicon grid is 3-6 μm. 6. A method for preparing a superhydrophobic anti-reflective silicon surface of a micron and nanocomposite structure as claimed in claim 1, characterized in that: the nanoimprinting method described in step (2) is a polymer MRI ～7030 or polymethyl methacrylate PMMA is spin-coated on the surface of the cleaned silicon wafer, and the silicon nitride with micron-scale lattice structure is used as a template to construct a polymer on the surface of the silicon wafer by nanoimprinting. A micron-scale ordered lattice structure complementary to the template structure; and then using the polymer of the lattice structure as a barrier layer to prepare micron-scale silicon islands by RIE etching, and the obtained silicon islands have a height of 2-4.5 μm. 7. A method for preparing a superhydrophobic anti-reflective silicon surface of a micron and nanocomposite structure as claimed in claim 1, characterized in that: the electroless deposition method described in step (3) is to prepare the surface with a micron-scale Silicon islands or grid-structured silicon wafers are put into a mixed solution of 4-5M HF and 0.01-0.02M AgNO ₃ to electrolessly deposit silver nanoparticles, and the deposition time is 1-4min. 8. A method for preparing a superhydrophobic anti-reflective silicon surface of a micron and nanocomposite structure, characterized in that: the electrodeposition method described in step (3) is to prepare the surface with micron-scale silicon islands or silicon grid structures Put the chip into 0.01-0.05M electrolyte AgNO ₃ , the deposition voltage is 400-800mv, and the deposition time is 10-20min; In the chloroauric acid electrolyte of M, the deposition voltage is 500-700mv, and the deposition time is 8-20min. 9. A method for preparing a superhydrophobic anti-reflective silicon surface with micron and nanocomposite structures as claimed in claim 1, characterized in that: the fluorosilylating agent described in step (4) is heptadecafluorodecyltrimethyl oxysilane, perfluorooctanesulfonic acid, perfluorodecyltriethoxysilane, dodecyltrichlorosilane, octadecyltrichlorosilane or perfluorooctylmethyldichlorosilane. 10. A method for preparing a superhydrophobic anti-reflective silicon surface with a micron and nanocomposite structure as claimed in claim 1, characterized in that the silicon wafer is n-100, p-100, n-111 or p-111 crystal type silicon wafers.

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