CN113097343A - Large-area processing technology for preparing titanium dioxide super lens - Google Patents
Large-area processing technology for preparing titanium dioxide super lens Download PDFInfo
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 title claims abstract description 173
- 239000004408 titanium dioxide Substances 0.000 title claims abstract description 86
- 238000012545 processing Methods 0.000 title claims abstract description 12
- 238000005516 engineering process Methods 0.000 title claims abstract description 7
- 239000010410 layer Substances 0.000 claims abstract description 81
- 239000002086 nanomaterial Substances 0.000 claims abstract description 66
- 238000005530 etching Methods 0.000 claims abstract description 59
- 229910052751 metal Inorganic materials 0.000 claims abstract description 50
- 239000002184 metal Substances 0.000 claims abstract description 50
- 238000000034 method Methods 0.000 claims abstract description 49
- 239000012790 adhesive layer Substances 0.000 claims abstract description 39
- 239000000758 substrate Substances 0.000 claims abstract description 38
- 239000003292 glue Substances 0.000 claims abstract description 15
- 238000000151 deposition Methods 0.000 claims abstract description 11
- 230000008569 process Effects 0.000 claims description 27
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 24
- 229910052710 silicon Inorganic materials 0.000 claims description 24
- 239000010703 silicon Substances 0.000 claims description 24
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 22
- 238000000231 atomic layer deposition Methods 0.000 claims description 14
- 238000004140 cleaning Methods 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 239000000377 silicon dioxide Substances 0.000 claims description 11
- 235000012239 silicon dioxide Nutrition 0.000 claims description 11
- 238000012546 transfer Methods 0.000 claims description 9
- 238000004528 spin coating Methods 0.000 claims description 8
- 238000005566 electron beam evaporation Methods 0.000 claims description 3
- 229910021421 monocrystalline silicon Inorganic materials 0.000 claims description 3
- 230000003287 optical effect Effects 0.000 abstract description 16
- 238000002360 preparation method Methods 0.000 abstract description 7
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical group [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 abstract description 4
- 238000009987 spinning Methods 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 11
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 8
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 8
- 229910052581 Si3N4 Inorganic materials 0.000 description 5
- 238000010521 absorption reaction Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000010894 electron beam technology Methods 0.000 description 5
- 238000001259 photo etching Methods 0.000 description 5
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 5
- 239000007789 gas Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 239000000356 contaminant Substances 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 238000005137 deposition process Methods 0.000 description 2
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- 239000002245 particle Substances 0.000 description 2
- 230000001699 photocatalysis Effects 0.000 description 2
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 2
- FAQYAMRNWDIXMY-UHFFFAOYSA-N trichloroborane Chemical compound ClB(Cl)Cl FAQYAMRNWDIXMY-UHFFFAOYSA-N 0.000 description 2
- 230000005374 Kerr effect Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 239000011248 coating agent Substances 0.000 description 1
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- 239000000428 dust Substances 0.000 description 1
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- 238000003384 imaging method Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 230000003071 parasitic effect Effects 0.000 description 1
- 238000007146 photocatalysis Methods 0.000 description 1
- 229920002120 photoresistant polymer Polymers 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10F71/00—Manufacture or treatment of devices covered by this subclass
- H10F71/137—Batch treatment of the devices
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10F30/00—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors
- H10F30/20—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors
- H10F30/21—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10F77/00—Constructional details of devices covered by this subclass
- H10F77/40—Optical elements or arrangements
- H10F77/413—Optical elements or arrangements directly associated or integrated with the devices, e.g. back reflectors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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Abstract
The invention discloses a large-area processing technology for preparing a titanium dioxide superlens. Comprises depositing a titanium dioxide film on a substrate; depositing a metal layer on the titanium dioxide film; a layer of impressing glue layer is coated on the metal layer in a spinning mode, and a micro-nano structure pattern is obtained on the upper surface of the impressing glue layer by adopting a nano impressing method; firstly, etching the imprinting adhesive layer and the metal layer; and etching the metal layer and the titanium dioxide film, and obtaining the titanium dioxide in the micro-nano structure pattern on the substrate. The method has the advantages of high efficiency, low cost and large-area preparation, and the titanium dioxide obtained by the method has excellent depth-to-width ratio which is 10: 1; the invention solves the technical problem that large-area preparation is difficult in the prior art, and the verticality of the titanium dioxide structure prepared by the method is close to 90 degrees, so that the optical performance of the titanium dioxide structure is improved, and the optical sensing performance is improved.
Description
Technical Field
The invention relates to the technical field of photoelectric detection devices, in particular to a large-area processing technology for preparing a titanium dioxide superlens.
Technical Field
Titanium dioxide is a very promising material. Has unique photocatalytic characteristics and excellent optical properties, such as high refractive index, wide visible-infrared transparent window, low two-photon absorption and high nonlinear capacity. In addition, by means of a coating and etching process, titanium dioxide can be integrated on a chip, and high-performance nonlinear application such as supercontinuum and optical frequency comb is realized; or the titanium dioxide super surface is realized, and the titanium dioxide super surface is applied to the aspects of structural color, super lens, enhanced photocatalysis and the like; meanwhile, the optical microcavity can be applied to an echo wall optical microcavity, and the titanium dioxide optical microcavity with a high Q value is utilized to realize applications such as enhancement of interaction with a substance, optical sensing and the like.
During the last decades, materials with strong nonlinear effects have been sought along with materials for optical waveguides that are compatible with CMOS processes. Ultra-high speed all-optical processing requires near-instantaneous material response. For bit rates greater than 1Tb/s, this is currently only achieved by exploiting passive, non-resonant nonlinear effects, such as the electronic Kerr effect. Therefore, we need to maximize Kerr nonlinearity (Kerr nonlinearity) while minimizing the absorption of parasitic two-photons.
Silicon has a high refractive index and the ability to integrate with silicon-based integrated circuits. However, the electronic band gap of the silicon material is very small (1.12eV), so that Two-photon absorption (Two-photon absorption) limits the nonlinear performance of the silicon photonic device near the 1300/1550nm communication band. Although the kerr nonlinearity of silicon nitride is small compared to silicon, since silicon nitride has a small propagation loss (0.7dB/cm) and a large band gap (5eV) so that two-photon absorption can be almost negligible, research on silicon nitride and related fabrication processes, such as a supercontinuum generator and a frequency comb generator, have been extensively studied as an alternative material to silicon in the direction of fabricating critical nonlinear devices. However, the silicon nitride waveguide-based photonic device has a large packaging area due to the small refractive index of silicon nitride (about 2.0), which is not favorable for manufacturing a plurality of chips on the same wafer. The band gap of TiO2 is 3.1eV, and in the wavelength range of 800-1600nm, the band gap energy is just slightly higher than twice of single photon energy.
And TiO2 provides good transparency throughout the visible spectrum, as well as ultra-fast all-optical functionality at the communication wavelength 1300/1500 nm. Its nonlinearity is 25-30 times that of silicon. Higher linear refractive index (>2.2) enables dense on-chip integration of optical waveguides. In addition, TiO2 is inexpensive, abundant in reserves and non-toxic. The TiO2 is readily integrated into electronic or other photonic systems by conventional fabrication procedures. These properties make TiO2 an excellent candidate for all-optical processing.
Disclosure of Invention
Aiming at the problems of the existing titanium dioxide preparation process, the etching process is optimized by comparing three processing processes of stripping, atomic layer deposition and etching, and a large-area processing process for preparing the titanium dioxide super lens is developed. The obtained titanium dioxide has excellent longitudinal-width ratio, and can be widely applied to the fields of super surfaces, super lenses, holographic imaging, waveguides, photoelectric detection and the like.
The technical scheme adopted by the invention is as follows:
the process steps of the invention are as follows:
step S1: thoroughly cleaning the upper surface of the substrate, and depositing a layer of titanium dioxide film with a certain thickness on the upper surface by adopting an Atomic Layer Deposition (ALD) process;
step S2: depositing a metal layer on the upper surface of the titanium dioxide film by adopting an electron beam evaporation process;
step S3: spin-coating an imprinting adhesive layer on the upper surface of the metal layer, copying and transferring the micro-nano structure patterns with the concave-convex intervals on the soft template to the upper surface of the imprinting adhesive layer by adopting a nano imprinting method, and obtaining the micro-nano structure patterns with the concave-convex intervals on the upper surface of the imprinting adhesive layer; concave parts and convex parts are arranged in the micro-nano structure pattern, and the concave parts and the convex parts are alternately arranged.
Step S4: vertically etching the micro-nano structure pattern with alternate concave and convex on the imprinting adhesive layer until the metal layer below the concave part in the micro-nano structure pattern on the imprinting adhesive layer is exposed, at the moment, the micro-nano structure patterns in the concave parts on the imprinting adhesive layer are etched away, the micro-nano structure patterns in the convex parts on the imprinting adhesive layer are remained, then etching the exposed metal layer and the micro-nano structure patterns at the convex part on the imprinting adhesive layer, copying and transferring the micro-nano structure patterns at the concave-convex intervals on the imprinting adhesive layer to the metal layer until the titanium dioxide film at the lower part of the concave part in the micro-nano structure patterns is etched to be exposed, wherein the metal layer at the convex part in the micro-nano structure patterns still exists, cleaning the imprinting adhesive layer remained on the metal layer at the convex part in the micro-nano structure patterns, and finally obtaining the metal layer at the micro-nano structure patterns on the upper surface of the titanium dioxide film;
step S5: vertically etching the titanium dioxide film exposed in the step S4 and the metal layer in the micro-nano structure pattern, wherein the vertical etching refers to etching along the direction vertical to the surface of one side of the titanium dioxide film far away from the substrate; until the substrate below the concave part in the micro-nano structure pattern is exposed after etching, the titanium dioxide film at the convex part in the micro-nano structure pattern still exists, then the metal layer which is remained on the titanium dioxide film at the convex part in the micro-nano structure pattern and is in the micro-nano structure pattern is cleaned, the titanium dioxide in the micro-nano structure pattern is obtained on the substrate, and the large-area processing for preparing the titanium dioxide refers to obtaining a plurality of titanium dioxide super lenses in the micro-nano structure pattern on the substrate which is 12 inches in size.
In step S3, the specific process of nanoimprinting is as follows: the imprinting adhesive layer is used as a nanoimprint pattern transfer layer, a prepared soft template with concave-convex alternate micro-nano structure patterns is covered on the pattern transfer layer by adopting a soft template copying method, pressure is applied to transfer the concave-convex alternate micro-nano structure patterns on the soft template to the upper surface of the imprinting adhesive layer, and then ultraviolet curing and demolding are carried out, so that the concave-convex alternate micro-nano structure patterns are obtained on the upper surface of the imprinting adhesive layer.
In the step S3, a spin coating apparatus is used to spin a layer of imprint glue layer on the surface of one side of the metal layer far away from the titanium dioxide film at a rotation speed of 3000r/min, so as to ensure that the thickness of the imprint glue layer spin coated on the metal layer is uniform and consistent. If the spin coating is not uniform, the etching effect in the subsequent step S4 is affected, and the effect of the prepared titanium dioxide is not good.
In step S1, the substrate includes a silicon substrate located on an upper layer and a silicon dioxide film located on a lower layer, and a silicon dioxide film is plated on an upper surface of the Si substrate.
And the silicon in the silicon substrate is polished P-type monocrystalline silicon.
The thickness of a deposited film can be controlled to be a few nanometers through atomic layer deposition, the ALD deposition process of titanium dioxide is relatively mature, steps can be well and uniformly covered, and the interface quality is good.
In step S4, the exposed metal layer and the imprinting glue layer are etched with the etching speed selection ratio of 2:1 and the same etching parameters.
And in the step S5, vertically etching the exposed titanium dioxide film and the metal layer in the micro-nano structure pattern by using the etching speed selection ratio of 4:1 and the same etching parameters.
The etching parameters comprise the magnitude of etching power, the selected gas and the flow rate of the selected gas.
The problem of the selection ratio is solved firstly in the etching process, and if the selection ratio is not enough, the etching depth can not reach the requirement. The selectivity ratio generally represents the etch resistance of the mask layer in terms of the ratio of the etch rates of the material being etched and the material of the mask. The thicknesses of the materials etched away from the substrate and the mask are Δ h1 and Δ h2, respectively, in a certain time, and the ratio S is Δ h1/Δ h 2. The higher the selectivity ratio, the less the mask layer is consumed in the etching process, and the more favorable the deep etching is.
The invention has the beneficial effects that:
compared with the existing electron beam direct writing photoetching method for copying the pattern structure on the photoresist, the method for copying the pattern structure by adopting the nano imprinting method has the advantages of high efficiency, low cost and large-area preparation, saves the step of developing in the electron beam photoetching, is more convenient to prepare, and the titanium dioxide obtained by adopting the method has excellent depth-to-width ratio which is 10: 1; the invention solves the technical problem that large-area preparation is difficult in the prior art, and the verticality of the titanium dioxide structure prepared by the method is close to 90 degrees, so that the optical performance of the titanium dioxide structure is improved, and the optical sensing performance is improved.
Drawings
FIG. 1 is a schematic view of a substrate;
FIG. 2 is a schematic illustration of the deposition of titanium dioxide;
FIG. 3 is a schematic illustration of depositing Al metal;
FIG. 4 is a schematic view of spin-on imprint resist;
FIG. 5 is a schematic diagram of an imprinted micro-nano pattern;
FIG. 6 is a schematic diagram of an etching paste and Al metal;
FIG. 7 is a schematic view of cleaning cull;
FIG. 8 is a schematic illustration of etching titanium dioxide;
FIG. 9 is a schematic illustration of cleaning residual Al metal;
FIG. 10 is a graph of perpendicularity of titanium dioxide as a function of optical properties.
In the figure, 1, a substrate; 11. a silicon substrate; 12. a silicon dioxide film; 2. a titanium dioxide film; 3. a metal layer; 4. and (6) impressing the glue layer.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and those skilled in the art can easily understand the advantages and effects of the present invention from the disclosure of the present specification. The invention is capable of other and different embodiments and its several details are capable of modifications and variations in various respects, all without departing from the spirit of the invention.
The large-area processing technology for preparing titanium dioxide of the embodiment of the invention comprises the following steps:
as shown in fig. 2, step S1: thoroughly cleaning the upper surface of a substrate 1, and depositing a layer of titanium dioxide film 2 with a certain thickness on the upper surface by adopting an Atomic Layer Deposition (ALD) process;
as shown in fig. 3, step S2: depositing a metal layer 3 on the upper surface of the titanium dioxide film 2 by adopting an electron beam evaporation process; in this example, aluminum metal (Al) was deposited to a film thickness of 55 nm.
As shown in fig. 4, step S3: spin-coating an imprinting adhesive layer 4 on the upper surface of the metal layer 3, copying and transferring the micro-nano structure patterns with alternate concave and convex on the soft template to the upper surface of the imprinting adhesive layer 4 by adopting a nano imprinting method, and obtaining the micro-nano structure patterns with alternate concave and convex on the upper surface of the imprinting adhesive layer 4; concave parts and convex parts are arranged in the micro-nano structure pattern, and the concave parts and the convex parts are alternately arranged. The imprint glue used was sensitive to 365nm ultraviolet light.
As shown in fig. 5 to 7, step S4: vertically etching the micro-nano structure pattern with alternate concave and convex on the imprinting adhesive layer 4 until the metal layer 3 below the concave part in the micro-nano structure pattern on the imprinting adhesive layer 4 is exposed, at the moment, the micro-nano structure patterns in the concave parts on the imprinting adhesive layer 4 are etched away, the micro-nano structure patterns in the convex parts on the imprinting adhesive layer 4 are remained, then etching the micro-nano structure patterns at the convex positions on the exposed metal layer 3 and the imprinting adhesive layer 4, copying and transferring the micro-nano structure patterns at the concave-convex intervals on the imprinting adhesive layer 4 to the metal layer 3 until the titanium dioxide film 2 at the lower part of the concave position in the micro-nano structure patterns is etched to be exposed, wherein the metal layer 3 at the convex position in the micro-nano structure patterns still exists, cleaning the imprinting adhesive layer 4 remained on the metal layer 3 at the convex position in the micro-nano structure patterns, and finally obtaining the metal layer 3 at the micro-nano structure pattern on the upper surface of the titanium dioxide film 2;
as shown in fig. 8 and 9, step S5: vertically etching the titanium dioxide film 2 exposed in the step S4 and the metal layer 3 in the micro-nano structure pattern, wherein the vertical etching refers to etching along the direction vertical to the surface of one side of the titanium dioxide film 2 far away from the substrate 1; until the substrate 1 below the concave part in the micro-nano structure pattern is exposed after etching, the titanium dioxide film 2 at the convex part in the micro-nano structure pattern still exists, then the metal layer 3 which is remained on the titanium dioxide film 2 at the convex part in the micro-nano structure pattern and is in the micro-nano structure pattern is cleaned, the titanium dioxide in the micro-nano structure pattern is obtained on the substrate 1, and the large-area processing for preparing the titanium dioxide refers to the step of obtaining a plurality of titanium dioxide in the micro-nano structure pattern on a substrate which is 12 inches in size.
In step S3, the specific process of nanoimprinting is: taking the imprinting adhesive layer 4 as a nanoimprint pattern transfer layer, covering a prepared soft template with concave-convex alternate micro-nano structure patterns on the pattern transfer layer by adopting a soft template copying method, applying pressure to transfer the concave-convex alternate micro-nano structure patterns on the soft template to the upper surface of the imprinting adhesive layer 4, and then curing and demolding by ultraviolet light to obtain concave-convex alternate micro-nano structure patterns on the upper surface of the imprinting adhesive layer 4.
In step S3, a spin coating apparatus is used to uniformly spin coat a layer of imprint glue layer 4 on the surface of the side of the metal layer 3 away from the titanium dioxide film 2 at a rotation speed of 3000r/min, so as to ensure that the thickness of the imprint glue layer 4 spin coated on the metal layer 3 is uniform. If the spin coating is not uniform, the etching effect in the subsequent step S4 is affected, and the effect of the prepared titanium dioxide is not good. After the imprinting glue is uniformly coated in a spinning mode, baking the imprinting glue on a hot plate for 2min, then transferring the micro-nano structure on the working soft die to the imprinting glue, demolding after exposure of ultraviolet light for 3min, and obtaining a micro-nano structure pattern with concave-convex intervals on the upper surface of the imprinting glue layer 4.
As shown in fig. 1, in step S1, the substrate 1 includes a silicon substrate 11 located at an upper layer and a silicon dioxide film 12 located at a lower layer, a silicon dioxide film 12 is plated on an upper surface of the Si substrate 11, and the thickness of the silicon dioxide film 12 is 2 um. The silicon in the silicon substrate 11 is implemented by polished P-type monocrystalline silicon.
In a specific implementation, a substrate coated with silicon dioxide (SiO2) is first thoroughly cleaned until the surface is free of foreign objects. A 450nm thick titanium dioxide (TiO2) film was deposited on a silicon dioxide substrate using an Atomic Layer Deposition (ALD) process, as shown in fig. 2, which is a schematic diagram after the deposition of the titanium dioxide film. In the ALD process, titanium tetrachloride (TiCl4) and water are used at a temperature of 120 ℃.
The thickness of a deposited film can be controlled to be a few nanometers through atomic layer deposition, the ALD deposition process of titanium dioxide is relatively mature, steps can be well and uniformly covered, and the interface quality is good.
In step S4, the exposed metal layer 3 and the exposed imprint resist layer 4 are etched at an etching rate selection ratio of 2:1 and the same etching parameters. The etching parameters include the magnitude of the etching power, the selected gas, and the flow rate of the selected gas. Boron trichloride (BCl3) and argon (Ar) are selected as etching parameters for dry etching, the etching RF power is 50W, the ICP power is 100W until the titanium dioxide surface exposure at some places is finished, and then the residual imprint glue is washed away, so that the metal layer, the titanium dioxide film and the substrate structure shown in the figure 7 are obtained.
As shown in fig. 9, in step S5, the exposed titanium dioxide film 2 and the metal layer 3 in the micro-nano structure pattern are vertically etched in an etching rate selection ratio of 4:1 and the same etching parameters. The etching parameter is CF4And O2(50/16.6sccm), Bias Voltage (300V), and ICP power of 100W. And after etching, removing the residual metal layer by using an alkaline aqueous solution to obtain the large-area micro-nano structure of the titanium dioxide.
In the specific implementation, in step S1, the substrate needs to be thoroughly cleaned before plating because of the existence of many contaminants such as dust and small particles on the Si wafer. First, to avoid contamination of the substrate by contaminants or residues in the beaker, the beaker is cleaned. Sufficient acetone was added to the beaker and placed in an ultrasonic cleaner to clean for 20 minutes at 25 ℃. Taking out the beaker, pouring off the acetone, adding sufficient isopropanol solution, and putting the beaker into an ultrasonic cleaning machine again for cleaning for 20 minutes at the temperature of 25 ℃. After being taken out, the isopropanol solution is poured out, and deionized water is added to carry out the same steps. After the beaker cleaning is completed, the silicon wafer is placed into the beaker, and sufficient acetone solution is added to immerse the silicon wafer. The beaker was washed in a super-sonic washer for 15 minutes at 25 ℃. The same washing step was then carried out with isopropanol and water in sequence. And taking out the silicon wafer after the completion, and observing whether particles or other pollutants still exist after the silicon wafer is cleaned and dried by an air gun. And if the silicon wafer is available, purging the silicon wafer by using an acetone gun, then sequentially cleaning the silicon wafer by using isopropanol and deionized water, and blow-drying. Repeating the steps until no foreign matter exists on the surface of the silicon wafer.
The problem of the selection ratio is solved firstly in the etching process, and if the selection ratio is not enough, the etching depth can not reach the requirement. The selectivity ratio generally represents the etch resistance of the mask layer in terms of the ratio of the etch rates of the material being etched and the material of the mask. The thicknesses of the materials etched away from the substrate and the mask are Δ h1 and Δ h2, respectively, in a certain time, and the ratio S is Δ h1/Δ h 2. The higher the selectivity ratio, the less the mask layer is consumed in the etching process, and the more favorable the deep etching is. In the invention, the etching selection ratio is high, and the titanium dioxide morphology can be well obtained.
When the existing electron beam direct writing photoetching method is adopted to prepare titanium dioxide, the step of developing is needed in the electron beam photoetching, the area of the electron beam photoetching scratch is small, the area is 1 to 2 inches, the price is very high, about hundreds of thousands, and the large-area preparation of the titanium dioxide cannot be realized. The area which can be imprinted by adopting the nano imprinting method is 4 to 10 times of that of electron beam lithography, the price is only tens of thousands, the developing step is not needed, the preparation process is simple, and the problem that the electron beam lithography technology is difficult to carry out large-area titanium dioxide lithography is solved.
At present, the etching inclination angle of the traditional titanium dioxide is about 80 degrees, the overall profile is in a table shape, and if the distance between two unit structures is relatively small, the distance cannot be separated along with the increase of the etching depth. Also, this tilt angle may reduce the efficiency of the light. With the method of the present invention, collapse and fracture of the sample structure can be preferably avoided for structures with relatively small line widths.
As shown in fig. 10, which is a graph of the change of optical performance with angle, the optical performance is more excellent as the angle is closer to 90 degrees. The angle of the titanium dioxide prepared by the method is close to vertical, namely the angle is close to 90 degrees, each structural unit is independently distributed, and the optical performance of the titanium dioxide is more excellent.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the inventive concept, many simple variations of the technical solution of the invention are possible, and in order to avoid unnecessary repetition, the invention will not be described in detail with respect to the various possible combinations. Such simple modifications and combinations should be considered within the scope of the present disclosure.
Claims (8)
1. A large-area processing technology for preparing titanium dioxide super lenses is characterized in that: the method comprises the following steps:
step S1: cleaning the upper surface of the substrate (1), and depositing a layer of titanium dioxide film (2) on the upper surface of the substrate (1) by adopting an Atomic Layer Deposition (ALD) process;
step S2: depositing a metal layer (3) on the upper surface of the titanium dioxide film (2) by adopting an electron beam evaporation process;
step S3: spin-coating an imprinting adhesive layer (4) on the upper surface of the metal layer (3), copying and transferring the micro-nano structure patterns with the concave-convex intervals on the soft template to the upper surface of the imprinting adhesive layer (4) by adopting a nano imprinting method, and obtaining the micro-nano structure patterns with the concave-convex intervals on the upper surface of the imprinting adhesive layer (4);
step S4: firstly, vertically etching the imprinting adhesive layer (4) until a metal layer (3) below a concave part in a micro-nano structure pattern on the imprinting adhesive layer (4) is etched to be exposed, then etching the exposed metal layer (3) and the imprinting adhesive layer (4) until a titanium dioxide film (2) below the concave part in the micro-nano structure pattern is etched to be exposed, cleaning the residual imprinting adhesive layer (4) on the metal layer (3), and finally obtaining the metal layer (3) in the micro-nano structure pattern on the upper surface of the titanium dioxide film (2);
step S5: and vertically etching the titanium dioxide film (2) exposed in the step S4 and the metal layer (3) in the micro-nano structure pattern until the substrate (1) below the concave part in the micro-nano structure pattern is exposed, and then cleaning the metal layer (3) in the micro-nano structure pattern remained on the titanium dioxide film (2) to obtain the titanium dioxide in the micro-nano structure pattern on the substrate (1).
2. The large area process of manufacturing titanium dioxide superlenses according to claim 1, wherein: in step S3, the specific process of nanoimprinting is as follows: the imprinting adhesive layer (4) is used as a nanoimprint pattern transfer layer, a prepared soft template with concave-convex alternate micro-nano structure patterns is covered on the pattern transfer layer by adopting a soft template copying method, pressure is applied to transfer the concave-convex alternate micro-nano structure patterns on the soft template to the upper surface of the imprinting adhesive layer (4), and then ultraviolet curing and demolding are carried out, so that concave-convex alternate micro-nano structure patterns are obtained on the upper surface of the imprinting adhesive layer (4).
3. The large area process of manufacturing titanium dioxide superlenses according to claim 1, wherein: in the step S3, a spin coating device is adopted to uniformly spin a layer of imprinting adhesive layer (4) on the surface of one side of the metal layer (3) far away from the titanium dioxide film (2) at the rotating speed of 3000r/min, so that the thickness of the spin-coated imprinting adhesive layer (4) on the metal layer (3) is ensured to be uniform.
4. The large area process of manufacturing titanium dioxide superlenses according to claim 1, wherein: in step S1, the substrate (1) includes a silicon substrate (11) on an upper layer and a silicon dioxide film (12) on a lower layer, and the silicon dioxide film (12) is plated on an upper surface of the Si substrate (11).
5. The large area process of manufacturing titanium dioxide superlenses according to claim 4, wherein: the silicon in the silicon substrate (11) is polished P-type monocrystalline silicon.
6. The large area process of manufacturing titanium dioxide superlenses according to claim 1, wherein: in step S4, the exposed metal layer (3) and the imprinting glue layer (4) are etched with the etching speed selection ratio of 2:1 and the same etching parameters.
7. The large area process of manufacturing titanium dioxide superlenses according to claim 1, wherein: and in the step S5, vertically etching the exposed titanium dioxide film (2) and the metal layer (3) in the micro-nano structure pattern by using the etching speed selection ratio of 4:1 and the same etching parameters.
8. The large area process of manufacturing titanium dioxide superlenses according to claim 7, wherein: the etching parameters comprise the magnitude of etching power, the selected gas and the flow rate of the selected gas.
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