Preparation method of micron-sized metal film array

Abstract

The invention discloses a preparation method of a micron-sized metal thin film array, and belongs to the technical field of thin film deposition processes. A micron-sized metal thin film array is prepared by adopting an unbalanced magnetic field cathode and using a vertical sputtering mode, the thickness of a metal thin film is 100-500nm, and a thin film grain growth mode is a nano columnar crystal. The preparation method comprises the following steps: (1) through combination of a magnetron sputtering method and a mask layer, a circular metal film array with the diameter consistent with that of holes in the surface of the mask layer can be precisely prepared on a large scale; (2) a non-equilibrium magnetic field cathode is used, plasma can be restrained on the surface of the target material, the utilization rate of the target material is improved, and meanwhile, sputtered target material atoms are restrained, so that the target material atoms can vertically pass through holes of the mask layer and are deposited on the surface of the substrate; and (3) the metal film array with uniform size and consistent thickness can be obtained by adjusting the technological parameters during magnetron sputtering, such as air pressure, power, target-substrate distance and rotating speed, so that the preparation difficulty of the film array is effectively reduced, and meanwhile, the film quality is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film deposition processes. Specifically, it relates to a method for preparing a micron-scale metal thin film array. Background Art

[0002] With the rapid development of micro-nano optical devices, nanostructures designed based on the principles of photon resonance or plasmon resonance exhibit brand-new optical properties. These novel features show great application potential in related research fields.

[0003] A micron-scale metal thin film array is a micron-sized metal thin film structure with a certain arrangement rule on a substrate, usually fabricated by techniques such as photolithography, sputtering, and electron beam evaporation. Due to its high surface area-to-volume ratio, high precision and sensitivity, excellent electrical and thermal conductivity, structural flexibility and customizability, and tunable optical properties, the micron-scale metal thin film array is widely used in high-tech fields such as sensors, optical devices, and electronic components, and has important application value in the manufacture of optical devices such as filters, mirrors, and plasmonic optical devices. With the in-depth exploration of researchers, it is found that the optical performance can be tuned by changing the geometric parameters of the array (such as spacing, thickness, and arrangement). With the continuous development of micro-nano manufacturing technology, the advantages of such array structures are expected to be further exploited, providing more support for high-precision and high-tech fields.

[0004] In current academic frontier reports, the fabrication of micron-scale metal thin film arrays usually requires the use of complex micro-nano processing techniques such as photolithography and nanoimprinting. The equipment costs of these techniques are relatively high, and the process steps are complex. Therefore, the cost of large-scale manufacturing of such structures is relatively high, especially when high precision and complex geometries are required. At the same time, precise control of the film thickness and uniformity is a technical difficulty, especially for large-area thin film arrays. Any tiny error may affect the overall performance of the array, thereby reducing the effectiveness of the device.

[0005] Based on the current research status and main drawbacks of metal thin film arrays, there is an urgent need to develop a growth process for micron-scale metal thin film arrays that is suitable for large-area deposition and has high quality. Summary of the Invention

[0006] The object of the present invention is to overcome the deficiencies of the prior art and provide a method for preparing a micron-scale metal thin film array. (1) By combining a simple magnetron sputtering method with a mask layer, a circular metal array with the same diameter as the holes on the surface of the mask layer can be precisely prepared on a large scale; (2) By using an unbalanced magnetic field cathode, the plasma can be confined on the surface of the target, improving the target utilization rate. At the same time, the sputtered target atoms can be confined so that they can vertically pass through the holes in the mask layer and be deposited on the surface of the substrate.

[0007] (3) By adjusting the process parameters during magnetron sputtering, such as gas pressure, power, target-substrate distance, and rotation speed, a metal thin film array with uniform size and consistent thickness can be obtained, effectively reducing the difficulty of preparing the metal thin film array and improving the film quality at the same time.

[0008] The object of the present invention can be achieved by the following technical solutions:

[0009] A method for preparing a micron-scale metal thin film array, which uses an unbalanced magnetic field cathode and a vertical sputtering method to prepare a micron-scale metal thin film array. The thickness of the metal thin film is between 100 - 500 nm, and the film grain growth mode is nano-columnar crystals. Specifically, it includes the following steps:

[0010] Step 1: Take a single-sided polished single-crystalline silicon substrate with a 300-nm-thick SiO 2 layer, ultrasonically clean it in chemically pure acetone and ethanol for 15 min in sequence, and then quickly dry it with high-purity nitrogen.

[0011] Step 2: Spin-coat a layer of polyvinylpyrrolidone on the surface of the cleaned single-crystalline silicon substrate, heat and cure it at 80 °C for 1 h. Subsequently, use a femtosecond laser processing system to etch a circular hole dot matrix structure on the polyvinylpyrrolidone layer, and quickly dry it with high-purity nitrogen.

[0012] Step 3: Spin-coat a layer of photoresist on the surface of the pre-etched polyvinylpyrrolidone layer / single-crystalline silicon, and cure and dry it.

[0013] Step 4: Use the contact mode of an ultraviolet lithography machine to locally expose the photoresist with an exposure dose of 300 - 900 mj to define the pattern, and place the locally exposed sample on a hot plate and bake it at a temperature of 110 - 120 °C for 90 - 180 s to cure the underlayer glue. Subsequently, place the exposed sample in a 2.38% tetramethylammonium hydroxide solution and develop it for 50 - 80 s. After taking it out, place it in deionized water for 40 - 60 s for fixing, and then take out the sample and dry it with a nitrogen gun. At this time, a photolithography hole array is formed on the sample. Each photolithography hole in the photolithography hole array is cylindrical.

[0014] Through Step 2, Step 3, and Step 4, a composite mask layer is formed on the single-crystalline silicon substrate, and its specific structure is the lower polyvinylpyrrolidone layer and the upper photolithography layer.

[0015] Step 5: By the magnetron sputtering method, use an unbalanced magnetron to vertically sputter the etched sample to deposit a micron-scale metal thin film array.

[0016] Step 6: Use a physical method to clean the composite mask layer attached to the substrate, exposing the micron-scale metal thin film array on the surface of the single-crystalline silicon substrate.

[0017] Step 7, observe the micron-scale metal thin film array prepared on the surface of single crystal silicon by scanning electron microscope.

[0018] Furthermore, the thickness of the polyvinylpyrrolidone spin-coated in step 2 is about 1 - 5 μm, and a polyvinylpyrrolidone / ethanol mixed solution with a mass fraction of 10% is used. The mixed solution is pre-prepared from PVP-K30 powder and absolute ethanol.

[0019] Furthermore, the etching parameters of the circular hole lattice structure in step 2: the circular diameter is about 2 - 6 μm, and the laser energy density is 0.050 J / cm 2 .

[0020] Furthermore, the photoresist in step 3 is NR9-6000PY negative photoresist, and the spin-coated thickness is about 1 - 5 μm; the curing and drying parameters are: baking at a temperature of 130 °C for 400 s to evaporate the solvent of the photoresist.

[0021] Furthermore, in step 5, the metal target can be pure metals such as Ti / Al / Ag / Cu / Au / Pt / Mo, with a purity of 99.99 wt%. Among them, the Hipims DC power supply power applied to the metal target is 200 W, the substrate rotation speed is 25 ° / s, Ar gas is continuously introduced during the sputtering process, the gas flow rate is 15 sccm, the deposition pressure is maintained at 1.9 Pa, and the target-substrate distance is stabilized at 10 - 15 cm.

[0022] Furthermore, in step 6, the physical method is: use 3M tape, stick it on the surface of the sample composite mask layer, and remove the 3M tape; the composite mask layer can also be removed by chemical method, specifically: first use a negative photoresist stripper to remove the photoresist layer, and then use absolute ethanol to remove the polyvinylpyrrolidone layer.

[0023] Advantages of the present invention:

[0024] 1. By simply combining the magnetron sputtering method and the mask template layer, a high-precision circular metal array with the same hole diameter as the surface of the mask layer can be prepared on a large scale;

[0025] 2. The present invention utilizes an unbalanced magnetic field cathode, uses the vertical sputtering method, and simultaneously uses a high-frequency pulsed DC power supply. By setting the DC power supply output power and the distance between the sample and the target, the energy of the sputtered metal atoms falling on the Si substrate is adjusted, ensuring the uniformity of the metal thin film array and improving the overall quality of the thin film.

[0026] 3. The present invention uses a commercial magnetron sputtering method, which is easy to repeat and simple to operate, solves the problems of high equipment cost, complex process steps and low precision, and realizes the high precision and uniformity of preparing a large-range metal thin film array. Description of the Drawings

[0027] The present invention will be further described below in conjunction with the accompanying drawings.

[0028] Figure 1 Schematic diagram of the metal thin film array of the method steps of the present invention.

[0029] Figure 2 Cross-sectional scanning electron microscopy spectrum of the metal thin film array obtained in Example 1.

[0030] Figure 3 Surface scanning electron microscopy spectrum of the metal thin film array obtained in Example 1.

[0031] Figure 4 Cross-sectional scanning electron microscopy spectrum of the metal thin film array obtained in Example 2.

[0032] Figure 5 Surface scanning electron microscopy spectrum of the metal thin film array obtained in Example 2.

[0033] Figure 6 Cross-sectional scanning electron microscopy spectrum of the metal thin film array obtained in Example 3.

[0034] Figure 7 Surface scanning electron microscopy spectrum of the metal thin film array obtained in Example 3. Detailed implementation manners

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] As Figure 1 shown, it is a schematic diagram of the metal thin film array of the method steps of the present invention, and the meanings of the reference numerals in the accompanying drawings are: single crystal silicon substrate 1, polyvinylpyrrolidone layer 2, photoresist layer 3, and micron-scale metal thin film array 4.

[0037] The preparation method of the composite mask layer in the following embodiments is:

[0038] On the surface of the cleaned single crystal silicon substrate 1, a layer of polyvinylpyrrolidone layer 2 is spin-coated, with a thickness of about 1 - 5 μm, heated and cured at 80 °C for 1 h, and then the polyvinylpyrrolidone layer 2 is etched with a round hole dot matrix structure by using a femtosecond laser processing system, the circular diameter is about 2 - 6 μm, and the laser energy density is 0.050 J / cm 2 (The 10% polyvinylpyrrolidone / ethanol mixed solution by mass fraction is prepared in advance with PVP-K30 powder and absolute ethanol), and quickly dried with high-purity nitrogen.

[0039] On the surface of the pre-etched polyvinylpyrrolidone layer 2 / single-crystalline silicon substrate 1, a photoresist layer 3 is spin-coated. The reagent is NR9-6000PY negative photoresist, with a thickness of about 1-5 μm, and it is cured and dried (baked at a temperature of 130 °C for 400 s to evaporate the solvent of the photoresist).

[0040] The contact mode of an ultraviolet lithography machine is used to locally expose the photoresist layer 3 with an exposure dose of 300-900 mj to define the pattern, and the sample after local exposure is placed on a hot plate and baked at a temperature of 110-120 °C for 90-180 s to cure the underlayer glue. Subsequently, the exposed sample is placed in a 2.38% tetramethylammonium hydroxide solution and developed for 50-80 s. After taking it out, it is fixed in deionized water for 40-60 s, and then the sample is taken out and dried with a nitrogen gun. At this time, a photolithography hole array is formed on the sample. Each photolithography hole in the photolithography hole array is cylindrical in shape. Thus, a composite mask layer (polyvinylpyrrolidone layer 2 and photoresist layer 3) is formed on the single-crystalline silicon substrate 1, and the specific structure is the lower polyvinylpyrrolidone layer 2 and the upper photoresist layer 3.

[0041] Example 1

[0042] This example provides a method for preparing a micron-scale metal thin film array:

[0043] The micron-scale metal thin film array is prepared by magnetron sputtering. First, a 4-inch P-type (100) single-polished single-crystalline silicon is taken as the substrate. The single-crystalline silicon substrate 1 is successively immersed in acetone, absolute ethanol, and deionized water, ultrasonically cleaned for 15 min, and dried with a nitrogen gun. After preparing a composite mask layer with a surface hole diameter of 2.7 μm on the surface of the single-crystalline silicon substrate 1, it is reserved. A high-purity (99.99%) metal Ti target is installed in the sputtering chamber, and the substrate is fixed by a tray, and the target-substrate distance is controlled at 100 mm. Before deposition, the vacuum chamber is evacuated to 2×10 -5 Pa, high-purity argon gas is introduced, and the gas flow rate is 15 sccm. By controlling the opening of the gate valve, the sputtering gas pressure is adjusted to 1.9 Pa. A high-frequency pulsed DC power supply is used, the sputtering power is set to 100 W, and the target ignition phenomenon is observed. After ignition, the target cover is not opened for pre-sputtering for 10 min to remove the contaminants on the target surface. During the film deposition process, the argon gas flow rate is 15 sccm, the sputtering time is 1 h, the tray rotation speed is 25° / s. After deposition, the film is transferred to the loading chamber, taken out after cooling to room temperature, adhered tightly to the surface of the mask layer with 3M tape, and the mask layer is removed by physical methods.

[0044] As Figure 2Shown is the cross-sectional scanning electron microscopy (SEM) pattern of the metal thin film array obtained in Example 1. After sputter deposition, a metal thin film array with a certain thickness was successfully obtained on the surface of the Si substrate. The thickness of the mask layer is about 1.8 μm, the pore diameter on the surface of the mask layer is about 2.7 μm, and the internal pore diameter is about 5.5 μm.

[0045] As Figure 3 Shown is the surface scanning electron microscopy (SEM) pattern of the metal thin film array obtained in Example 1. The diameter of the metal thin film is 3 μm, and the spacing between adjacent metal thin films is about 1.5 μm.

[0046] Example 2

[0047] This example provides a method for preparing a micron-scale metal thin film array:

[0048] The micron-scale metal thin film array is prepared by magnetron sputtering. First, a 4-inch P-type (100) single-polished single-crystalline silicon is taken as the substrate. The single-crystalline silicon substrate 1 is successively immersed in acetone, absolute ethanol, and deionized water, ultrasonically cleaned for 15 min, and dried with a nitrogen gun. After preparing a composite mask layer with a surface hole diameter of 1.8 μm on the surface of the single-crystalline silicon substrate 1, it is reserved for use. A high-purity (99.99%) metal Ti target is installed in the sputtering chamber. The substrate is fixed by a tray, and the target-substrate distance is controlled at 150 mm. Before deposition, the vacuum chamber is evacuated to 2×10 -5 Pa, high-purity argon gas is introduced, and the gas flow rate is 15 sccm. By controlling the opening of the gate valve, the sputtering gas pressure is adjusted to 1.9 Pa. A high-frequency pulsed DC power supply is used, and the sputtering power is set to 100 W. Observe the target ignition phenomenon. After ignition, do not open the target cover and pre-sputter for 10 min to remove the contaminants on the surface of the target. During the thin film deposition process, the argon gas flow rate is 15 sccm, the sputtering time is 1 h, the tray rotation speed is 25° / s. After deposition, the thin film is transferred to the sample introduction chamber, taken out after cooling to room temperature, adhered tightly to the surface of the mask layer with 3M tape, and the mask layer is removed by physical methods.

[0049] As Figure 4 Shown is the cross-sectional scanning electron microscopy (SEM) pattern of the metal thin film array obtained in Example 2. After sputter deposition, a metal thin film array with a certain thickness was successfully obtained on the surface of the Si substrate. The thickness of the mask layer is about 2 μm, the pore diameter on the surface of the mask layer is about 1.8 μm, and the internal pore diameter is about 4.6 μm.

[0050] As Figure 5 Shown is the surface scanning electron microscopy (SEM) pattern of the metal thin film array obtained in Example 2. The diameter of the metal thin film is 1.8 μm, and the spacing between adjacent metal thin films is about 2.5 μm.

[0051] Example 3

[0052] This example provides a method for preparing a micron-scale metal thin film array:

[0053] The preparation of the micron-scale metal thin film array adopts the magnetron sputtering method. First, a 4-inch P-type (100) single-polished single-crystalline silicon is taken as the substrate. The single-crystalline silicon substrate 1 is successively immersed in acetone, absolute ethanol and deionized water, ultrasonically cleaned for 15 minutes and dried with a nitrogen gun. After preparing a composite mask layer with a surface hole diameter of 3 μm on the surface of the single-crystalline silicon substrate 1, it is reserved for use. A high-purity (99.99%) metal Ti target is installed in the sputtering chamber. The substrate is fixed by a tray, and the target-substrate distance is controlled at 150 mm. Before deposition, the vacuum chamber is evacuated to 2×10 -5 Pa, high-purity argon gas is introduced, and the gas flow rate is 15 sccm. By controlling the opening of the gate valve, the sputtering gas pressure is adjusted to 1.9 Pa. A high-frequency pulsed DC power supply is used, and the sputtering power is set at 200 W. Observe the target ignition phenomenon. After ignition, do not open the target cover and pre-sputter for 10 minutes to remove the contaminants on the target surface. During the film deposition process, the argon gas flow rate is 15 sccm, the sputtering time is 1 h, and the tray rotation speed is 25° / s. After deposition, the film is transferred to the sample introduction chamber, taken out after cooling to room temperature, adhered tightly to the surface of the mask layer with high-temperature tape, and the mask layer is removed by physical methods.

[0054] As Figure 6 shown is the cross-sectional scanning electron microscope spectrum of the metal thin film array obtained in Example 3. After sputtering deposition, a metal thin film array with a certain thickness is successfully obtained on the surface of the Si substrate. The thickness of the mask layer is about 1.8 μm, the surface pore diameter of the mask layer is about 3 μm, and the internal pore diameter is about 5.5 μm.

[0055] As Figure 7 shown is the surface scanning electron microscope spectrum of the metal thin film array obtained in Example 3. The diameter of the metal thin film is 3.5 μm, and the distance between adjacent metal thin films is about 1.2 μm.

[0056] The above specific embodiments part specifically introduces the analysis method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and idea of the present invention, rather than a limitation on the relevant content. Without departing from the principle of the present invention, those skilled in the art can also make appropriate adjustments or modifications to the present invention, and the above adjustments and modifications should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a micron-sized metal thin film array, characterized in that: The following steps are involved: Step 1, take a single-side polished single crystal silicon substrate with a 300 nm thick SiO2 layer on its surface, ultrasonically clean it in acetone and ethanol for 15 min in sequence, and then quickly blow dry it with high-purity nitrogen; Step 2, spin-coating a layer of polyvinyl pyrrolidone on the surface of the cleaned single crystal silicon substrate, heating and curing at 80° C. for 1 hour, then etching the polyvinyl pyrrolidone layer with a circular hole lattice structure using a femtosecond laser processing system, and quickly drying it with high-purity nitrogen; Step 3, spin coating a photoresist layer on the pre-etched polyvinyl pyrrolidone layer / single crystal silicon surface, and curing and drying; Step 4, using the contact mode of the ultraviolet lithography machine to locally expose the photoresist with an exposure dose of 300 to 900 mj to define the pattern, and placing the locally exposed sample on a heating plate and baking it at a temperature of 110 to 120° C. for 90 to 180 seconds to cure the primer; then placing the exposed sample in a 2.38% tetramethylammonium hydroxide solution, developing it for 50 to 80 seconds, taking it out and fixing it in deionized water for 40 to 60 seconds, then taking out the sample and blowing it dry with a nitrogen gun, at this time, a photolithography hole array is formed on the sample; each photolithography hole in the photolithography hole array is cylindrical; Step 5, using a magnetron sputtering method, using an unbalanced magnetron to vertically sputter the etched sample to deposit a micron-sized metal film array; Step 6, using a physical method to clean the composite mask layer attached to the substrate to expose the micron-sized metal film array on the surface of the single crystal silicon substrate; Step 7: Observe the micron-scale metal film array prepared on the surface of the single crystal silicon through a scanning electron microscope.

2. The method for preparing a micron-sized metal thin film array according to claim 1, characterized in that: The thickness of the polyvinyl pyrrolidone spin-coated in step 2 is 1-5 μm, and a polyvinyl pyrrolidone / ethanol mixed solution with a mass fraction of 10% is used, and the mixed solution is pre-prepared with PVP-K30 powder and anhydrous ethanol.

3. The method for preparing a micron-sized metal thin film array according to claim 1, characterized in that: The etching parameters of the circular hole lattice structure in step 2 are: the circular diameter is about 2-6μm, and the laser energy density is 0.050J / cm 2 .

4. The method for preparing a micron-sized metal thin film array according to claim 1, characterized in that: In step 3, the photoresist is NR9-6000PY negative photoresist, and the spin coating thickness is 1-5 μm; the curing and drying parameters are: baking at a temperature of 130° C. for 400 seconds to evaporate the solvent of the photoresist.

5. The method for preparing a micron-sized metal thin film array according to claim 1, characterized in that: In step 5, the metal target is any pure metal of Ti, Al, Ag, Cu, Au, Pt, and Mo with a purity of 99.99wt%.

6. The method for preparing a micron-sized metal thin film array according to claim 5, characterized in that: A Hipims DC power supply of 200 W was applied to the metal target, the substrate rotation speed was 25° / s, Ar gas was continuously introduced during the sputtering process, the gas flow rate was 15 sccm, the deposition gas pressure was maintained at 1.9 Pa, and the target-substrate distance was stabilized at 10-15 cm.

7. The method for preparing a micron-sized metal thin film array according to claim 1, characterized in that: In step 6, the physical method is: use 3M tape to stick it on the surface of the sample composite mask layer, and then remove the 3M tape.

8. The method for preparing a micron-sized metal thin film array according to claim 1, characterized in that: In step 6, the composite mask layer is removed by a chemical method, specifically, firstly using a negative photoresist stripper to remove the photoresist layer, and then using anhydrous ethanol to remove the polyvinyl pyrrolidone layer.

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