Golf tee nano-pillar array diamond reflector machining method

Abstract

The invention discloses a method for processing a'golf tee 'nano-pillar array diamond reflector, which comprises the following steps of: S1, analyzing and acquiring optical parameters of polycrystalline diamond, and constructing a'golf tee' nano-pillar array three-dimensional model; s2, preparing a'golf tee 'nanopore array on the monocrystalline silicon substrate by adopting photoetching and anisotropic etching methods; s3, epitaxially growing polycrystalline diamond by adopting a microwave plasma chemical vapor deposition (MPCVD) method and taking the silicon substrate prepared in the step S2 as a growth substrate; s4, the amorphous polycrystalline diamond on the periphery is removed through a laser cutting method, and polishing of the upper surface of the epitaxial diamond is completed through mechanical polishing; and S5, wet etching is adopted to remove the monocrystalline silicon substrate, and finally, the nano-pillar array diamond reflecting mirror with the golf ball seat is obtained. The method has the advantages of being simple, low in equipment requirement, low in cost, capable of achieving wafer-level machining and the like, and is suitable for mass production of diamond reflectors.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical device manufacturing, and particularly relates to a processing method of a "golf tee" nano-pillar array diamond mirror. BACKGROUND

[0002] High-power continuous wave (CW) lasers are widely used in various fields such as industry, medicine, communication and national defense, and these high-power continuous wave (CW) laser applications require optical components, especially mirrors. The optical components such as the currently widely used multilayer coated mirrors are difficult to withstand the continuous heat accumulation under strong laser irradiation, and are prone to performance degradation or even physical damage. This fundamental defect not only limits the effective output power and reliability of the laser system, but also increases the operating cost and maintenance complexity of the system, ultimately affecting the overall performance and market expansion prospects of high-power continuous wave (CW) laser applications.

[0003] Diamond is used because of its excellent performance, such as relatively high refractive index, wide band gap, high mechanical hardness and chemical resistance, and the highest material thermal conductivity at room temperature. Unlike traditional multilayer coated mirrors, by etching "golf tee" nanostructures on the surface of single crystal diamond, a nanostructured mirror is obtained from the diamond substrate using surface plasmon resonance effects. This mirror not only has excellent reflective performance, but also can withstand high-power continuous laser. However, the processing of optical components such as multilayer coated mirrors is strongly dependent on reactive ion beam etching equipment (RIBE) and the maturity of diamond processing technology. Currently, RIBE equipment is expensive and has low processing efficiency, and high-energy particle bombardment can easily introduce surface damage; the existing maturity of diamond processing technology cannot achieve the manufacture of optical components such as multilayer coated mirrors, and the existing diamond processing technology cannot achieve high-quality, low-cost processing of large-size diamond mirrors. In addition, the limitations of RIBE equipment manufacturing technology and the immaturity of diamond processing technology severely limit the manufacture of "golf tee" nanostructure diamond mirrors. SUMMARY

[0004] Based on the technical problems existing in the prior art, the present application provides a "golf tee" nano-pillar array diamond mirror processing method. The present application solves the technical problems that the processing technology based on the RIBE method is limited by the RIBE equipment and the diamond processing technology, and it is difficult to achieve high-quality, low-cost processing of large-size diamond mirrors. The present application is based on silicon micro-nano processing technology and MPCVD technology to prepare a "golf tee" nano-pillar array diamond mirror, which has the advantages of simple process, low cost, low equipment requirement, and large-area processing.

[0005] According to the technical scheme adopted by the present application, a "golf tee" nano-pillar array diamond mirror processing method is provided, which comprises the following steps: Step S1: Analyzing and obtaining optical parameters, and constructing a "golf tee" nanocolumn array three-dimensional model; Step S2: Preparing a "golf tee" nanopore array on a silicon substrate through photolithography and anisotropic etching; Step S3: Epitaxial growth of polycrystalline diamond by microwave plasma chemical vapor deposition; Step S4: Laser cutting and mechanical polishing of the epitaxial diamond obtained in step S3; Step S5: Removing the single crystal silicon substrate by wet etching to obtain a "golf tee" nanocolumn array diamond mirror.

[0006] In step S1, the polycrystalline diamond optical parameters are analyzed and obtained, and a "golf tee" nanocolumn array three-dimensional model is constructed. The key structure parameters of the "golf tee" are determined based on the simulation results of the "golf tee" nanocolumn array three-dimensional model.

[0007] Preferably, the analysis and acquisition of the polycrystalline diamond optical parameters specifically use an ultraviolet-visible light spectrophotometer to measure the reflectivity of the polycrystalline diamond in the 200 nm-800 nm wavelength band, and an ellipsometer is used to obtain the refractive index (n) and extinction coefficient (k).

[0008] More preferably, in the analysis and acquisition of the polycrystalline diamond optical parameters, the optical properties in the deep ultraviolet band are focused on.

[0009] Further, based on step S1, a "golf tee" nanocolumn array three-dimensional model is constructed, a "golf tee" nanopore array is prepared on a single crystal silicon substrate using photolithography and anisotropic etching, and an ion beam polisher is used to polish the nanopore array with high precision.

[0010] More further, the specific parameters of photolithography in step S2 include: coating LOR and S1805 double-layer photoresist, electron beam exposure as the exposure method, beam current density of 10 pA / cm²; AZ300MIF as the developing solution, developing time of 60 seconds; Preferably, the specific implementation method of high-precision polishing in step S2 includes: using an ion beam polisher to polish the surface of the nanopore, fine-tuning the polishing parameters, and finally achieving a sub-nanometer surface roughness; Further, the specific implementation method of step S3 includes: placing the cleaned silicon wafer in an MPCVD device, growing a diamond film under the conditions of hydrogen flow rate 400 sccm, methane flow rate 10 sccm, cavity pressure 20 kPa, substrate temperature 900℃, microwave power 7 kW, and growth time 100 hours; Further, the step S5 specifically realizes the method, which comprises: etching the silicon substrate by using a mixed solution of hydrofluoric acid and nitric acid to separate the diamond film from the silicon wafer, and further cleaning the diamond film by using a standard RAC process, so that the diamond mirror film with sub-nanometer roughness can be obtained without polishing process. According to the second aspect of the technical scheme of the present application, a "golf tee" nanometer pillar array diamond mirror is provided, which is processed by using the "golf tee" nanometer pillar array diamond mirror processing method.

[0011] Compared with the prior art, the "golf tee" nanometer pillar array diamond mirror processing method has the following beneficial technical effects: 1. The "golf tee" nanometer pillar array diamond mirror is prepared based on the silicon micro-nano processing technology and the MPCVD technology, which has the advantages of simplified process steps, low cost, low equipment requirement, and large-area processing.

[0012] 2. The silicon wet etching is used to replace the diamond ICP etching process and the MPCVD diamond epitaxial growth technology, which avoids high-energy particle damage and can obtain a mirror sheet with high-regular surface structure and high surface quality.

[0013] 3. The diamond "golf tee" nanometer pillar array three-dimensional structure processing method combines the "silicon-based MEMS technology" with the "diamond MPCVD epitaxy", solves the problems of difficult processing and high cost of the diamond mirror micro-nano structure, and improves the processing efficiency and safety of the diamond mirror. DETAILED DESCRIPTION

[0014] In order to more clearly illustrate the technical scheme in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. Figure 1 The flowchart of the "golf tee" nanometer pillar array diamond mirror method according to the present application is shown. Figure 2 The cross-sectional structure of the silicon wafer obtained by wet etching silicon according to the method of the present application is shown. Figure 3 The growth cross-sectional structure of the diamond film on the surface of the silicon wafer after wet etching processing according to the MPCVD of the present application is shown. Figure 4 The cross-sectional structure of the diamond mirror formed by processing according to the present application is shown. DETAILED DESCRIPTION

[0015] In order to make the technical problems solved by the present application, the technical solutions adopted and the beneficial effects obtained more clear and understandable, the present application is further described in detail below in combination with specific embodiments. The specific embodiments described herein are only used to explain the present application and do not constitute any limitation on the present application. Unless otherwise defined, all terms used in the present application have the same meaning as commonly used in the field of the present application.

[0016] The application discloses a diamond mirror processing method with a "golf tee" nanocolumn structure, comprising the following steps: step S1: analyzing and obtaining optical parameters of polycrystalline diamond, and constructing a three-dimensional model of a "golf tee" nanocolumn array; step S2: using photolithography and anisotropic etching to prepare a "golf tee" nanohole array on a single crystal silicon substrate; step S3: using a microwave plasma chemical vapor deposition (MPCVD) method, taking the silicon substrate prepared in step S2 as a growth substrate, and epitaxially growing polycrystalline diamond; step S4: removing the surrounding amorphous polycrystalline diamond by using a laser cutting method, and completing polishing of the upper surface of the epitaxial diamond by using mechanical polishing; step S5: removing the single crystal silicon substrate by using a wet etching method, and finally obtaining a diamond mirror with a "golf tee" nanocolumn array. The "golf tee" nanocolumn array diamond mirror processing method provided by the application only relies on a mature silicon-based MEMS processing technology, and is free from the limitations of immature diamond micro-nano processing technology and high-end etching equipment. The "golf tee" nanocolumn is located in an ingrowth surface, and low roughness avoids the difficulty of non-planar polishing process. The application has the advantages of simple method, low equipment requirement, low cost and wafer-level processing, and is suitable for mass production of diamond mirrors.

[0017] The technical solutions of the "golf tee" nanocolumn array diamond mirror processing method of the application are further described below in combination with the drawings.

[0018] As shown in Figure 1 The application provides a "golf tee" nanocolumn array diamond mirror processing method, which comprises the following steps: Step S1: analyzing and obtaining optical parameters, and constructing a three-dimensional model of the "golf tee" nanocolumn array; specifically, analyzing and obtaining the optical parameters of the polycrystalline diamond, and constructing a three-dimensional model of the "golf tee" nanocolumn array, determining the key structural parameters of the "golf tee" according to the simulation results of the three-dimensional model of the "golf tee" nanocolumn array; specifically, using an ultraviolet-visible light spectrophotometer to measure the reflectivity of the polycrystalline diamond in the 200 nm-800 nm waveband, the test sample is mechanically polished (Ra<0.5 nm), the test scanning step is 1 nm, and the measurement is performed three times to take the average value; the refractive index (n) and the extinction coefficient (k) are obtained by an ellipsometer, the Ψ / Δ spectrum is collected at an incident angle of 65°, the refractive index n=2.410±0.005 and the extinction coefficient k≤0.01 at 220 nm are obtained by model fitting; in the analysis and obtaining of the optical parameters of the polycrystalline diamond, the optical properties in the deep ultraviolet waveband (<250 nm) are focused on.

[0019] Specifically, based on the optical parameters of the polycrystalline diamond obtained in the previous stage, the finite time domain difference method (FDTD) is used to simulate the light field distribution, and the measured n / k value is imported to establish a diamond material library; a "golf tee" unit is constructed: a bottom cylinder (diameter Db=300-500 nm, height 0.8H), a top cylinder (diameter Dt=50-100 nm, height 0.2H), and a constraint Dt / Db≤0.25 (anti-collapse angle); the grid is set as Δx=Δy=2 nm, Δz=1 nm (λ / 110@220 nm), and the periodic boundary (period Pitch=Db+100 nm); a Gaussian light source (center 220 nm, bandwidth 20 nm) is irradiated, and scanning is performed on the Db (step 50 nm), Dt (step 10 nm), and H (400 / 500 / 600 nm) combinations, and the optimal solution of the reflectivity peak value is output to optimize the nanocolumn size to improve the reflectivity in a specific waveband (such as 220 nm). In the preferred embodiment of the present application, the low absorption of diamond at 220 nm combined with the Mie resonance effect of the nanocolumn array can enhance the reflection in the target waveband (such as 220 nm). Further, the narrow diameter of the "golf tee" structure adopted in the present application reduces light scattering loss, and the wide diameter of the bottom enhances mechanical stability; the nanocolumn array diamond mirror processing method of the present application avoids direct etching of diamond by modeling first and then modular growth, which avoids high cost.

[0020] Step S2: photoetching and anisotropic etching to prepare the "golf tee" nanohole array on the silicon substrate; specifically, a three-dimensional model of the "golf tee" nanopillar array is constructed based on step S1, a "golf tee" nanohole array is prepared on a single-crystal silicon substrate by photoetching and anisotropic etching, and the nanohole array is polished with high precision by an ion beam polisher. The specific parameters of photoetching in this step S2 include: LOR and S1805 double-layer photoresist are coated on the single-crystal silicon substrate, the exposure mode is electron beam exposure, the beam current density is 5 pA / cm2-15 pA / cm2, preferably 10 pA / cm2, the developing solution is AZ300MIF, the developing time is 40 seconds-70 seconds, preferably 60 seconds, and the "golf tee" nanohole array is prepared by wet etching.

[0021] In an embodiment, the method of this step S2 specifically includes: Step a. Forming a nanocircular array on a silicon wafer by coating, exposing, and developing; Step b. Depositing 50 nm Au and 250 nm Cr on the surface in sequence by magnetron sputtering; Step c. Fixing the silicon wafer obtained in step b to a single-side cleaning clamp, immersing it in an anisotropic wet etching solution to perform etching, wherein the anisotropic wet etching solution is composed of 20wt%-35 wt% potassium hydroxide and 6wt%-8.5wt% isopropyl alcohol, and the volume ratio of the two is in the range of 2:1 to 3:1; the etching temperature is 60°C-90°C, and the etching time is 50 minutes-150 minutes; preferably, the anisotropic wet etching solution is composed of 30 wt% potassium hydroxide and 7.5 wt% isopropyl alcohol, and the volume ratio of the two is 2.4:1; the etching temperature is 70°C, and the etching time is 90 minutes-120 minutes; in another preferred embodiment, the anisotropic wet etching solution is composed of 35wt% potassium hydroxide and 7wt% isopropyl alcohol, and the volume ratio of the two is 2.9:1, the etching temperature is 75°C, and the etching time is 100 minutes; Step d. After the etching of step c, the chromium layer is removed using cerium ammonium nitrate solution, and then isopropanol, acetone, alcohol solution are used for ultrasonic cleaning for 10 min, specifically, isopropanol with a concentration of 70%-75%, acetone with a concentration of ≥99.5%, and alcohol (absolute ethanol) with a concentration of 99.5%, and the cleaning time is 10 min for each ultrasonic cleaning. After that, it is dried with a nitrogen gun, preferably at a temperature of 35-70 degrees Celsius for 5-8 minutes; the specific implementation method of high-precision polishing includes: using an ion beam polisher to polish the surface of the nanopore, and adjusting the polishing parameters; preferably, the ion beam polishing parameters are: ion energy: 100-300 eV, beam current density: 0.8-1.5 mA / cm², scanning mode: spiral scanning, polishing time: 20-30 min; finally, a sub-nanometer level surface roughness is achieved. The cross-section of the obtained sample is shown in Figure 2 .

[0022] Step S3: epitaxial growth of polycrystalline diamond by microwave plasma chemical vapor deposition; specifically, using the silicon substrate prepared in step S2 as a growth substrate, polycrystalline diamond is epitaxially grown by microwave plasma chemical vapor deposition (MPCVD) method; The cleaned silicon wafer is placed in an MPCVD device, and the diamond film is grown under the conditions of hydrogen flow rate 300-500 sccm, methane flow rate 8-25 sccm, chamber pressure 15-30 kPa, substrate temperature 800-950℃, microwave power 6-8 kW, and growth time 60-120 hours; preferably, the diamond film is grown under the conditions of hydrogen flow rate 400 sccm, methane flow rate 10 sccm, chamber pressure 20 kPa, substrate temperature 900℃, microwave power 7 kW, and growth time 100 hours; In a preferred embodiment, pure hydrogen plasma and methane are used for cleaning in sequence, pure hydrogen plasma is used for bombardment in the first stage (0-2h) to activate the nucleation sites on the silicon surface; high methane flow rate (for example, methane flow rate 10 sccm) is used for long-time growth in the second stage (2h-100h) to ensure complete filling of the nanopores. The cross-section of the obtained sample is shown in Figure 3 .

[0023] Step S4: laser cutting and mechanical polishing are used to process the epitaxial diamond obtained in step S3, specifically, laser cutting is used to remove the amorphous polycrystalline diamond around the diamond, and mechanical polishing is used to complete the polishing of the upper surface of the epitaxial diamond.

[0024] In an embodiment, the epi diamond obtained in step 3 is fixed by using 502 glue, the polycrystalline diamond obtained by laser scanning step S3 is positioned and cut by a confocal microscope, the boundary of the amorphous polycrystalline diamond is marked, a cutting path is designed using CAD software, and the single crystal diamond epitaxial layer is avoided; the laser scans the polycrystalline diamond along the marked path, the laser ablates the amorphous polycrystalline layer, and the laser is repeatedly circulated until the single crystal epitaxial layer substrate is exposed; and the single crystal epitaxial layer substrate is polished by using a cast iron plate and diamond grinding paste, coarse polishing: diamond grinding paste particle size 15 μm, pressure 15-20 N / cm 2 , rotation speed 80-100 rpm, time 60-90 min; fine polishing: nano diamond suspension 0.25 μm, pressure 0.5-1 N / cm 2 , rotation speed 40-50 rpm, time 120-180 min; after the polishing technology, acetone, ethanol, and deionized water are used in sequence for ultrasonic cleaning for 5-10 min to remove polishing residues, and the mechanical polishing can remove the subsurface damage layer caused by laser cutting.

[0025] Step S5: removing the single crystal silicon substrate by wet etching to obtain a "golf tee" nanorod array diamond mirror; specifically, the single crystal silicon substrate is removed by wet etching, and finally a "golf tee" nanorod array diamond mirror is obtained. The silicon substrate is etched by a mixed solution of hydrofluoric acid and nitric acid, preferably, hydrofluoric acid (HF): nitric acid (HNO3) = 1:3 (volume ratio), wherein the concentrations are: 49% hydrofluoric acid and 69% nitric acid; the diamond film is separated from the silicon wafer, and the diamond film is further cleaned by a standard RAC process, and a nanometer-level roughness diamond mirror film can be obtained without polishing process. In a preferred embodiment, the sample after step S4 is immersed in a constant-temperature mixed acid (hydrofluoric acid (HF): nitric acid (HNO3) = 1:3 (volume ratio)) solution at 25°C, and the etching time is 45-60 min. The silicon layer is completely dissolved, the diamond film is automatically peeled off, the solution becomes brownish yellow, and the diamond film floats on the liquid surface. The RAC cleaning solution formula is: 30% H2O2: 28% NH4OH: Dl water = 1:1:5 (volume ratio), immersed in the RAC solution at 80°C for 15 min, washed with deionized water, and dried with high-purity nitrogen. A "golf tee" nanorod array diamond mirror is obtained. The cross section of the obtained diamond mirror is shown in Figure 4 .

[0026] Finally, it should be pointed out that the above detailed description is of the preferred embodiments of the present application. However, the present application is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application. These simple modifications all belong to the protection scope of the present application.

[0027] It should also be noted that any of the technical features described in the above embodiments can be combined with each other, in so far as they are not mutually exclusive. In order to avoid unnecessary repetition, the present application does not describe each possible combination of the various features. Furthermore, any of the various embodiments of the present application can be combined with each other, in so far as they are not mutually exclusive, and should be considered as disclosed herein.

Claims

1. A method for fabricating a "golf tee" nanopillar array diamond mirror, characterized in that, Includes the following steps: Step S1: Analyze and obtain optical parameters to construct a three-dimensional model of the "golf ball seat" nanopillar array; Step S2: Photolithography and anisotropic etching are used to fabricate a "golf ball seat" nanopore array on a silicon substrate; Step S3: Microwave plasma chemical vapor deposition epitaxial growth of polycrystalline diamond; Step S4: The epitaxial diamond obtained in step S3 is processed by laser cutting and mechanical polishing; Step S5: Wet etching removes the single-crystal silicon substrate to obtain a 'golf tee' nanopillar array diamond mirror.

2. The method for fabricating a "golf tee" nanopillar array diamond mirror according to claim 1, characterized in that, Step S1 specifically involves analyzing and obtaining the optical parameters of polycrystalline diamond, constructing a three-dimensional model of the "golf ball seat" nanopillar array, and determining the key structural parameters of the "golf ball seat" based on the simulation results of the three-dimensional model of the "golf ball seat" nanopillar array.

3. The method for fabricating a "golf tee" nanopillar array diamond mirror according to claim 2, characterized in that, The optical parameters of polycrystalline diamond were obtained by analyzing and measuring the reflectance of polycrystalline diamond in the 200nm-800nm ​​wavelength range using a UV-Vis spectrophotometer, and obtaining the refractive index (n) and extinction coefficient (k) using an ellipsometer.

4. The method for fabricating a "golf tee" nanopillar array diamond mirror according to claim 3, characterized in that, In analyzing and obtaining the optical parameters of polycrystalline diamond, we focus on its optical properties in the deep ultraviolet band.

5. The method for fabricating a "golf tee" nanopillar array diamond mirror according to claim 3, characterized in that, Based on step S1, a three-dimensional model of the "golf ball seat" nanopillar array was constructed. The "golf ball seat" nanopore array was fabricated on a single-crystal silicon substrate using photolithography and anisotropic etching methods. The nanopore array was then polished with high precision using an ion beam polisher.

6. The method for fabricating a "golf tee" nanopillar array diamond mirror according to claim 1, characterized in that, The specific parameters for photolithography in step S2 include: coating with a double layer of LOR and S1805 photoresist, exposure method is electron beam exposure, beam current density is 10 pA / cm², developer is AZ300MIF, and development time is 60 seconds.

7. The method for fabricating a "golf tee" nanopillar array diamond mirror according to claim 6, characterized in that, The specific implementation method of high-precision polishing in step S2 includes: polishing the surface of the nanopores using an ion beam polisher, fine-tuning the polishing parameters, and finally achieving a sub-nanometer level surface roughness.

8. The method for fabricating a "golf tee" nanopillar array diamond mirror according to claim 1, characterized in that, The specific implementation method of step S3 includes: placing the cleaned silicon wafer in an MPCVD equipment, and growing a diamond film under the conditions of hydrogen flow rate of 400 sccm, methane flow rate of 10 sccm, chamber pressure of 20 kPa, substrate temperature of 900℃, and microwave power of 7 kW for 100 hours.

9. The method for fabricating a "golf tee" nanopillar array diamond mirror according to claim 1, characterized in that, The specific implementation method of step S5 includes: using a mixed solution of hydrofluoric acid and nitric acid to wet etch the silicon substrate to separate the diamond film from the silicon wafer, and then using the standard RAC process to clean the diamond film, so as to obtain a diamond mirror film with sub-nanometer roughness without polishing process.

10. A "golf tee" nanopillar array diamond reflector, characterized in that, It is manufactured using the method for processing a "golf tee" nanopillar array diamond mirror according to any one of claims 1 to 9.

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