A method for preparing an arc-shaped gold nanopillar array

Abstract

This invention provides a method for fabricating an array of arc-shaped gold nanopillars, belonging to the field of gold nanomaterial fabrication technology. The invention involves preparing a gold film on the surface of a substrate using physical vapor deposition (PVD), then coating the gold film with photoresist to form a photoresist mask layer. The photoresist mask layer is then exposed and developed to form an array of circular holes consisting of multiple non-contacting first circular holes. Excess gold film and photoresist are removed through vertical etching and photoresist stripping. Finally, the diameter of each first circular hole in the array is enlarged by tilted etching, forming a second array of circular holes on the substrate. Residual gold film is retained between three adjacent second circular holes, resulting in the arc-shaped gold nanopillar array formed by the remaining gold film on the substrate surface. The fabrication method provided by this invention is simple to operate, has low production costs, high fabrication efficiency, and is capable of large-scale mass production.

Description

Technical Field

[0001] This invention belongs to the field of gold nanomaterial preparation technology, specifically relating to a method for preparing an arc-shaped gold nanopillar array. Background Technology

[0002] The surface-enhanced Raman scattering (SERS) effect generated by periodically arranged noble metal (gold, silver, platinum, etc.) nanoarrays can be used to detect the content of low-abundance organic matter, thus having a wide range of applications in biosensors. Compared with traditional gold nanopillar arrays, curved gold nanopillar arrays have a larger surface area and higher sensitivity, thus having broader research and application value.

[0003] Currently, noble metal nanopillar arrays are mainly fabricated using electron beam lithography (EBL). However, EBL is a complex process with high production costs and very low fabrication efficiency, making large-scale mass production difficult. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing arc-shaped gold nanopillar arrays. The preparation method provided by this invention is simple to operate, has low production cost, high preparation efficiency, and can be mass-produced.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing an array of arc-shaped gold nanopillars, comprising the following steps:

[0007] A gold film was prepared on the upper surface of a substrate by physical vapor deposition to obtain a gold-plated substrate;

[0008] Photoresist is coated on the upper surface of the gold film on the gold-plated substrate to form a photoresist mask layer; the photoresist mask layer is exposed and developed in sequence to form a first circular hole array, resulting in a photoresist developed substrate; the first circular hole array is formed by multiple non-contacting first circular holes, the bottom surface of each first circular hole exposes the gold film, and the gold film and the photoresist mask layer on the surface of the gold film are retained outside the first circular hole.

[0009] The gold film in each first circular hole on the photoresist developing substrate is removed by vertical etching, so that the bottom surface inside each first circular hole is exposed to the substrate, while the gold film and the photoresist mask layer on the surface of the gold film are retained outside the first circular hole, thus obtaining a vertically etched substrate.

[0010] The vertically etched substrate is subjected to a photoresist removal process to remove the remaining photoresist mask layer on the vertically etched substrate, while a gold film is retained outside the first circular hole, resulting in a photoresist-removed substrate.

[0011] The diameter of each first circular hole in the first circular hole array on the resist-removed substrate is increased by tilting etching to form a second circular hole array on the substrate; the second circular hole array is formed by the second circular holes and three adjacent second circular holes are in contact with each other, and a residual gold film is retained between the three adjacent second circular holes, and the arc-shaped gold nanopillar array formed by the residual gold film is obtained on the upper surface of the substrate.

[0012] Preferably, the substrate includes at least one of a glass substrate, a silicon substrate, a silicon carbide substrate, a sapphire substrate, and a quartz substrate.

[0013] Preferably, the physical vapor deposition process includes sequentially subjecting the substrate to acid treatment and alkali treatment;

[0014] The reagents used for the acid treatment are concentrated sulfuric acid and hydrogen peroxide. The concentration of the concentrated sulfuric acid is 98 wt%, and the concentration of the hydrogen peroxide is 30 wt% to 35 wt%. The volume ratio of the concentrated sulfuric acid to the hydrogen peroxide is 1 to 3: 1 to 2. The acid treatment time is 15 to 30 minutes.

[0015] The reagents used for the alkali treatment are ammonia and hydrogen peroxide. The concentration of ammonia is 0.8-0.9 g / mL, the concentration of hydrogen peroxide is 30 wt%-35 wt%, and the volume ratio of ammonia to hydrogen peroxide is 1-3:1-2. The alkali treatment time is 20-30 min.

[0016] Preferably, the physical vapor deposition method is magnetron sputtering; the deposition rate of the gold film is... The thickness of the gold film is 180–220 nm.

[0017] Preferably, the thickness of the photoresist mask layer is 550–650 nm; the coating is spin coating, and the rotation speed of the stage used in the spin coating is 2000–2500 rpm.

[0018] Preferably, the intensity of the light used for the exposure is 1.8–2.6 mW / cm². 2 The exposure time is 10-15 seconds.

[0019] Preferably, the diameter of the first circular hole is 380–420 nm, and the period is 590–610 nm.

[0020] Preferably, the conditions for vertical etching include: stage angle of 0-5°; argon flow rate of 10-15 sccm; and etching time of 30-45 min.

[0021] Preferably, the adhesive removal process is microwave plasma adhesive removal; the microwave plasma adhesive removal is carried out in an oxygen atmosphere with a flow rate of 200 sccm.

[0022] Preferably, the conditions for the tilt etching include: a stage angle of 60–70°; a stage rotation speed of 5–15 rpm; an argon flow rate of 5–10 sccm; and an etching time of 10–20 min.

[0023] This invention provides a method for fabricating an array of arc-shaped gold nanopillars, comprising the following steps: preparing a gold film on the upper surface of a substrate by physical vapor deposition; coating the upper surface of the gold film with photoresist to form a photoresist mask layer; then forming a circular aperture array consisting of multiple non-contacting first circular apertures by exposure and development, wherein the bottom surface of each first circular aperture exposes the gold film, and the gold film and the photoresist mask layer on the surface of the gold film are retained outside the first circular aperture; then removing the gold film in each first circular aperture on the substrate by vertical etching, thereby exposing the bottom surface of each first circular aperture to the substrate, and the first circular aperture... A vertically etched substrate is obtained by retaining a gold film and a photoresist mask layer on the surface of the gold film. The vertically etched substrate is then subjected to a photoresist stripping process to remove the remaining photoresist mask layer, leaving a gold film outside the first circular holes, resulting in a stripped substrate. The diameter of each first circular hole in the first circular hole array on the stripped substrate is enlarged by tilting etching, forming a second circular hole array on the substrate. The second circular hole array is formed by the second circular holes, with three adjacent second circular holes in contact with each other, and a remaining gold film remaining between the three adjacent second circular holes, resulting in an arc-shaped gold nanopillar array formed by the remaining gold film on the upper surface of the substrate. This method replaces electron beam lithography with traditional photolithography, resulting in lower production costs compared to traditional electron beam lithography. Furthermore, the execution and operation of each step are very simple, enabling large-scale production. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 Cross-sectional views of the gold-plated glass substrate and the photoresist glass substrate;

[0026] Figure 2 A top view of the photoresist developing glass substrate;

[0027] Figure 3This is a cross-sectional view of the photoresist developing glass substrate;

[0028] Figure 4 Cross-sectional views of vertically etched glass substrate and resist-removed glass substrate;

[0029] Figure 5 A top view of an array of arc-shaped gold nanopillars;

[0030] Among them, 1-glass substrate; 2-gold film; 3-photoresist mask layer. Detailed Implementation

[0031] This invention provides a method for preparing an array of arc-shaped gold nanopillars, comprising the following steps:

[0032] A gold film was prepared on the upper surface of a substrate by physical vapor deposition to obtain a gold-plated substrate;

[0033] Photoresist is coated on the upper surface of the gold film on the gold-plated substrate to form a photoresist mask layer; the photoresist mask layer is exposed and developed in sequence to form a first circular hole array, resulting in a photoresist developed substrate; the first circular hole array is formed by multiple non-contacting first circular holes, the bottom surface of each first circular hole exposes the gold film, and the gold film and the photoresist mask layer on the surface of the gold film are retained outside the first circular hole.

[0034] The gold film in each first circular hole on the photoresist developing substrate is removed by vertical etching, the bottom surface of each first circular hole is exposed to expose the substrate, and the gold film and the photoresist mask layer on the surface of the gold film are retained outside the first circular hole, thus obtaining a vertically etched substrate.

[0035] The vertically etched substrate is subjected to a photoresist removal process to remove the remaining photoresist mask layer on the vertically etched substrate, while a gold film is retained outside the first circular hole, resulting in a photoresist-removed substrate.

[0036] The diameter of each first circular hole in the first circular hole array on the resist-removed substrate is increased by tilting etching to form a second circular hole array on the substrate; the second circular hole array is formed by the second circular holes and three adjacent second circular holes are in contact with each other, and a residual gold film is retained between the three adjacent second circular holes, and the arc-shaped gold nanopillar array formed by the residual gold film is obtained on the upper surface of the substrate.

[0037] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0038] This invention prepares a gold film on the surface of a substrate using physical vapor deposition (PVD) to obtain a gold-plated substrate. In this invention, the substrate preferably includes at least one of a glass substrate, a silicon substrate, a silicon carbide substrate, a sapphire substrate, and a quartz substrate, more preferably a glass substrate or a silicon carbide substrate. In an embodiment of this invention, a glass substrate is used, specifically a 4-inch glass wafer. In this invention, the substrate is preferably subjected to acid treatment and then alkali treatment sequentially before PVD.

[0039] The reagents used for acid treatment in this invention are preferably concentrated sulfuric acid and hydrogen peroxide; the concentration of the concentrated sulfuric acid is preferably 98 wt%; the concentration of the hydrogen peroxide is preferably 30 wt% to 35 wt%, specifically 30 wt%, 32 wt%, or 35 wt%; the volume ratio of the concentrated sulfuric acid to the hydrogen peroxide is preferably 1 to 3:1 to 2, more preferably 2:1. The acid treatment time in this invention is preferably 15 to 30 minutes, more preferably 15 to 20 minutes. This invention removes residual particulate impurities from the substrate surface through acid treatment. Preferably, the substrate is immersed in the reagent used for acid treatment, and during the immersion process, the substrate is lifted up and down 3 to 5 times (specifically 3, 4, or 5 times) to ensure a more complete reaction between the substrate and the reagent used for acid treatment.

[0040] The reagents used for the alkali treatment in this invention are preferably ammonia and hydrogen peroxide; the concentration of the ammonia is preferably 0.8-0.9 g / mL, specifically 0.8 g / mL, 0.85 g / mL, or 0.9 g / mL; the concentration of the hydrogen peroxide is preferably 30 wt%-35 wt%, specifically 30 wt%, 32 wt%, or 35 wt%; the volume ratio of the ammonia to the hydrogen peroxide is preferably 1-3:1-2, more preferably 2:1. The alkali treatment time in this invention is preferably 20-30 min, more preferably 20-25 min. This invention neutralizes the acid treatment reagents remaining on the substrate surface through alkali treatment. Preferably, the substrate after acid treatment is immersed in the alkali treatment reagent, and during the immersion process, the substrate is lifted up and down 3-5 times (specifically 3, 4, or 5 times) to ensure complete neutralization of the acid treatment reagents.

[0041] After the alkali treatment, the substrate is preferably washed with water to obtain a pretreated substrate. In this invention, the water is preferably deionized water.

[0042] After obtaining the pretreated substrate, the present invention prepares a gold film on the surface of the pretreated substrate by physical vapor deposition, thereby obtaining a gold-plated substrate. In the present invention, the physical vapor deposition method is preferably magnetron sputtering; the deposition rate of the gold film is preferably... More preferably The thickness of the gold film described in this invention is preferably 180-220 nm, and more preferably 200 nm.

[0043] After obtaining the gold-plated substrate, the present invention coats the upper surface of the gold film on the gold-plated substrate with photoresist to form a photoresist mask layer. Preferably, the gold-plated glass substrate is placed on a spin coater, and photoresist is coated on its upper surface. In this invention, the coating is preferably spin-coating; the rotation speed of the stage used during spin-coating is preferably 2000–2500 rpm, more preferably 2000–2200 rpm; the thickness of the photoresist mask layer is preferably 550–650 nm, more preferably 600 nm. After the photoresist coating is completed, the present invention preferably performs a hardening operation on the photoresist-coated substrate. In this invention, the hardening operation is performed in an oven; the temperature of the hardening operation is preferably 80–100°C, more preferably 80–90°C; the time of the hardening operation is preferably 8–10 min, more preferably 8 min.

[0044] After forming a photoresist mask layer on a gold film on a gold-plated substrate, the present invention sequentially exposes and develops the photoresist mask layer to form a first circular aperture array, thereby obtaining a photoresist developed substrate. In this invention, the exposure and development are preferably performed in a photolithography machine. The intensity of the light used for exposure in this invention is preferably 1.8–2.6 mW / cm². 2 More preferably, it is 1.8–2.2 mW / cm². 2 The exposure time is preferably 10-15 seconds, more preferably 10-12 seconds. This invention transfers pattern information from a photomask to a photoresist mask layer through exposure; development forms a first circular aperture array in the photoresist mask layer. In this invention, the first circular aperture array is formed by multiple non-contacting first circular apertures, with the bottom surface of each first circular aperture exposing a gold film, and the gold film and the photoresist mask layer on the surface of the gold film remaining outside the first circular aperture. The diameter of the first circular aperture in this invention is preferably 380-420 nm, more preferably 400 nm; the period is preferably 590-610 nm, more preferably 600 nm.

[0045] After obtaining the photoresist developing substrate, the present invention removes the gold film in each first circular hole on the photoresist developing substrate by vertical etching, exposing the bottom surface of each first circular hole to the substrate, while retaining the gold film and the photoresist mask layer on the surface of the gold film outside each first circular hole, thus obtaining a vertically etched substrate. In the present invention, the vertical etching is preferably performed in a reactive ion beam etching machine. The preferred conditions for the vertical etching of the present invention include: a stage angle of 0-5°, more preferably 0°; an argon flow rate of 10-15 sccm, more preferably 15 sccm; and an etching time of 30-45 min, more preferably 30 min.

[0046] After obtaining the vertically etched substrate, the present invention performs a photoresist stripping process on the vertically etched substrate to remove the remaining photoresist mask layer on the substrate, while retaining a gold film outside the first circular hole, resulting in a stripped substrate. The photoresist stripping process of the present invention is preferably microwave plasma stripping; the microwave plasma stripping is preferably performed in an oxygen atmosphere; the oxygen flow rate is preferably 200–300 sccm, more preferably 200 sccm. In the present invention, the photoresist stripping process is preferably performed in a microwave plasma stripping machine.

[0047] After obtaining the resist-removed substrate, the present invention expands the diameter of each first circular hole in the first circular hole array on the resist-removed substrate by tilting etching, forming a second circular hole array on the substrate. The second circular hole array is formed by the second circular holes, with three adjacent second circular holes in contact with each other, and a residual gold film is retained between the three adjacent second circular holes, resulting in the arc-shaped gold nanopillar array formed by the residual gold film on the upper surface of the substrate. In the present invention, the tilting etching is preferably performed in a reactive ion beam etching machine. In the present invention, the preferred conditions for the tilting etching include: a stage angle of 60-70°, more preferably 64°; a stage rotation speed of 5-15 rpm, more preferably 10 rpm; an argon flow rate of 5-10 sccm, more preferably 10 sccm; and an etching time of 10-15 min, more preferably 10 min. In the present invention, tilting etching is performed under an argon atmosphere, and argon plasma continuously etches away the gold on the sidewalls of the first circular holes on the resist-removed substrate. After the tilting etching is completed, a second circular hole array is formed on the substrate. In this invention, the diameter of the second circular aperture array is preferably 590-610 nm, more preferably 600 nm; the period is preferably 590-610 nm, more preferably 600 nm.

[0048] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0049] The glass substrate used in this embodiment is a glass wafer with a diameter of 4 inches.

[0050] Example 1

[0051] (1) The glass substrate was immersed in a mixed solution of concentrated sulfuric acid (98 wt%) and hydrogen peroxide (30 wt%) (volume ratio of concentrated sulfuric acid to hydrogen peroxide: 2:1) for 15 min to remove residual particulate impurities on the surface of the glass substrate. During the immersion process, the glass substrate was lifted up and down 3 times to ensure a more complete reaction between the glass substrate and the acid. Then, the glass substrate was immersed in a mixed solution of ammonia (0.8 g / mL) and hydrogen peroxide (30 wt%) (volume ratio of ammonia to hydrogen peroxide: 2:1) for 20 min to neutralize the residual acid on the surface of the glass substrate. During the immersion process, the glass substrate was lifted up and down 3 times to ensure complete neutralization of the acid. After the immersion was completed, the glass substrate was rinsed with deionized water to obtain a pretreated glass substrate for later use.

[0052] (2) A gold film with a thickness of 200 nm was deposited on the upper surface of the pretreated glass substrate by magnetron sputtering at a deposition rate of [missing information]. A gold-plated glass substrate is obtained, such as Figure 1 As shown in (a).

[0053] (3) Place the gold-plated glass substrate on a spin coater and coat the upper surface of the gold-plated glass substrate with a photoresist layer of 600 nm thickness. The stage rotation speed is 2000 rpm during coating. Next, place the photoresist-coated glass substrate in an oven and heat it at 80°C for 8 minutes to complete the hardening process, i.e., form a photoresist mask layer on the upper surface of the gold-plated glass substrate, resulting in a photoresist glass substrate, as shown below. Figure 1 (b) and Figure 2 As shown. The photoresist glass substrate is placed in the photolithography machine under a light intensity of 1.8 mW / cm². 2 Exposure for 10 seconds under certain conditions to transfer the pattern information on the photomask to the photoresist mask layer; then a development operation is performed to form a first circular aperture array in the photoresist mask layer, resulting in a photoresist developing glass substrate; the first circular aperture array is formed by multiple non-contact first circular apertures (the bottom surface of each first circular aperture exposes a gold film, while the outside of the first circular aperture still retains the gold film and the photoresist mask layer on the surface of the gold film), the diameter of the first circular aperture is 400 nm, and the period is 600 nm, such as Figure 3 As shown.

[0054] (3) The photoresist developing glass substrate is placed in a reactive ion beam etching (RIBE) machine for vertical etching. The specific operation is as follows: the stage angle is set to 0°, and etching is performed for 30 minutes under an argon flow rate of 15 sccm to remove the gold film in each first circular hole on the photoresist developing glass substrate (i.e., the bottom surface of each first circular hole is exposed to the glass substrate, while the gold film and the photoresist mask layer on the surface of the gold film are still retained outside the first circular hole), to obtain a vertically etched glass substrate, such as... Figure 4 As shown in (a).

[0055] (4) After vertical etching is completed, the vertically etched glass substrate is placed in a microwave plasma resist remover. The power of the microwave plasma resist remover is set to 500W, and the resist is removed for 15 minutes under an oxygen flow rate of 200 sccm to remove the remaining photoresist mask layer on the vertically etched glass substrate (i.e., the gold film is still retained outside the first circular hole), resulting in a resist-removed glass substrate, as shown below. Figure 4 As shown in (b).

[0056] (5) The adhesive-removed glass substrate is placed in a reactive ion etching machine for tilt etching to enlarge the diameter of each first circular hole in the first circular hole array. The specific operation is as follows: the stage angle is set to 64°, the rotation speed is 10 rpm, and etching is performed for 10 min under an argon flow rate of 10 sccm. As the tilt etching proceeds, argon plasma continuously etches away the gold on the sidewalls of the first circular holes on the adhesive-removed glass substrate. After the tilt etching is completed, a second circular hole array is formed on the glass substrate. The second circular hole array is formed by the second circular holes, and three adjacent second circular holes are in contact with each other. A residual gold film is still retained between the three adjacent second circular holes. The arc-shaped gold nanopillar array formed by the residual gold film is obtained on the upper surface of the glass substrate, such as... Figure 5 As shown.

[0057] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing an array of arc-shaped gold nanopillars, comprising the following steps: A gold film was prepared on the upper surface of a substrate by physical vapor deposition to obtain a gold-plated substrate; Photoresist is coated on the upper surface of the gold film on the gold-plated substrate to form a photoresist mask layer; The photoresist mask layer is sequentially exposed and developed to form a first circular aperture array, thereby obtaining a photoresist development substrate. The first circular hole array is formed by multiple non-contacting first circular holes. The bottom surface of each first circular hole exposes a gold film, and the gold film and a photoresist mask layer on the surface of the gold film are retained outside the first circular hole. The gold film in each first circular hole on the photoresist developing substrate is removed by vertical etching, so that the bottom surface inside each first circular hole is exposed to the substrate, while the gold film and the photoresist mask layer on the surface of the gold film are retained outside the first circular hole, thus obtaining a vertically etched substrate. The vertically etched substrate is subjected to a photoresist removal process to remove the remaining photoresist mask layer on the vertically etched substrate, while a gold film is retained outside the first circular hole, resulting in a photoresist-removed substrate. The diameter of each first circular hole in the first circular hole array on the resist-removed substrate is increased by tilting etching to form a second circular hole array on the substrate; the second circular hole array is formed by the second circular holes and three adjacent second circular holes are in contact with each other, and a residual gold film is retained between the three adjacent second circular holes, and the arc-shaped gold nanopillar array formed by the residual gold film is obtained on the upper surface of the substrate.

2. The preparation method according to claim 1, characterized in that, The substrate includes at least one of a glass substrate, a silicon substrate, a silicon carbide substrate, a sapphire substrate, and a quartz substrate.

3. The preparation method according to claim 1, characterized in that, The physical vapor deposition process includes sequentially acid-treating and alkali-treating the substrate. The reagents used for the acid treatment are concentrated sulfuric acid and hydrogen peroxide. The concentration of the concentrated sulfuric acid is 98 wt%, and the concentration of the hydrogen peroxide is 30 wt% to 35 wt%. The volume ratio of the concentrated sulfuric acid to the hydrogen peroxide is 1 to 3: 1 to 2. The acid treatment time is 15 to 30 minutes. The reagents used for the alkali treatment are ammonia and hydrogen peroxide. The concentration of ammonia is 0.8-0.9 g / mL, the concentration of hydrogen peroxide is 30 wt%-35 wt%, and the volume ratio of ammonia to hydrogen peroxide is 1-3:1-2. The alkali treatment time is 20-30 min.

4. The preparation method according to claim 1, characterized in that, The physical vapor deposition method is magnetron sputtering; the deposition rate of the gold film is... The thickness of the gold film is 180–220 nm.

5. The preparation method according to claim 1, characterized in that, The thickness of the photoresist mask layer is 550–650 nm; the coating is spin coating, and the rotation speed of the stage used in the spin coating is 2000–2500 rpm.

6. The preparation method according to claim 1, characterized in that, The intensity of the light used for the exposure is 1.8–2.6 mW / cm². 2 The exposure time is 10-15 seconds.

7. The preparation method according to claim 1 or 6, characterized in that, The diameter of the first circular hole is 380–420 nm, and the period is 590–610 nm.

8. The preparation method according to claim 1, characterized in that, The conditions for vertical etching include: stage angle of 0-5°; argon flow rate of 10-15 sccm; and etching time of 30-45 min.

9. The preparation method according to claim 1, characterized in that, The adhesive removal process is microwave plasma adhesive removal; the microwave plasma adhesive removal is carried out in an oxygen atmosphere with a flow rate of 200 sccm.

10. The preparation method according to claim 1, characterized in that, The conditions for the tilt etching include: stage angle of 60-70°; stage rotation speed of 5-15 rpm; argon flow rate of 5-10 sccm; and etching time of 10-20 min.

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