CN115182052B - Method for preparing micro-nano device on surface of thin film lithium niobate - Google Patents
Method for preparing micro-nano device on surface of thin film lithium niobate Download PDFInfo
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- CN115182052B CN115182052B CN202210928731.7A CN202210928731A CN115182052B CN 115182052 B CN115182052 B CN 115182052B CN 202210928731 A CN202210928731 A CN 202210928731A CN 115182052 B CN115182052 B CN 115182052B
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- lithium niobate
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- film lithium
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 title claims abstract description 78
- 239000010409 thin film Substances 0.000 title claims abstract description 51
- 238000000034 method Methods 0.000 title claims abstract description 42
- 239000000758 substrate Substances 0.000 claims abstract description 79
- 239000010408 film Substances 0.000 claims abstract description 42
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 27
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 27
- 239000011651 chromium Substances 0.000 claims abstract description 27
- 239000000463 material Substances 0.000 claims abstract description 23
- 238000005530 etching Methods 0.000 claims abstract description 15
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 13
- 238000001259 photo etching Methods 0.000 claims abstract description 13
- 238000001039 wet etching Methods 0.000 claims abstract description 13
- 230000001681 protective effect Effects 0.000 claims abstract description 10
- 238000001816 cooling Methods 0.000 claims abstract description 9
- 239000000126 substance Substances 0.000 claims abstract description 8
- 239000011241 protective layer Substances 0.000 claims abstract description 7
- 239000011259 mixed solution Substances 0.000 claims abstract description 6
- 238000007789 sealing Methods 0.000 claims abstract description 6
- 238000007517 polishing process Methods 0.000 claims abstract description 4
- 239000010410 layer Substances 0.000 claims description 34
- 239000007788 liquid Substances 0.000 claims description 20
- 239000000243 solution Substances 0.000 claims description 15
- 238000000227 grinding Methods 0.000 claims description 14
- 238000005498 polishing Methods 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 11
- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 claims description 10
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 9
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 9
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims description 6
- 238000004140 cleaning Methods 0.000 claims description 6
- 229910052731 fluorine Inorganic materials 0.000 claims description 6
- 239000011737 fluorine Substances 0.000 claims description 6
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 5
- 239000005711 Benzoic acid Substances 0.000 claims description 5
- 235000010233 benzoic acid Nutrition 0.000 claims description 5
- 238000000151 deposition Methods 0.000 claims description 5
- 238000010894 electron beam technology Methods 0.000 claims description 5
- 239000012530 fluid Substances 0.000 claims description 5
- 238000001755 magnetron sputter deposition Methods 0.000 claims description 5
- 239000012188 paraffin wax Substances 0.000 claims description 5
- 229920002120 photoresistant polymer Polymers 0.000 claims description 5
- 238000004528 spin coating Methods 0.000 claims description 5
- 230000007797 corrosion Effects 0.000 claims description 4
- 238000005260 corrosion Methods 0.000 claims description 4
- 238000011161 development Methods 0.000 claims description 4
- 239000004519 grease Substances 0.000 claims description 4
- 230000002093 peripheral effect Effects 0.000 claims description 4
- XPPKVPWEQAFLFU-UHFFFAOYSA-N diphosphoric acid Chemical compound OP(O)(=O)OP(O)(O)=O XPPKVPWEQAFLFU-UHFFFAOYSA-N 0.000 claims description 3
- 235000006408 oxalic acid Nutrition 0.000 claims description 3
- 229940005657 pyrophosphoric acid Drugs 0.000 claims description 3
- 239000002253 acid Substances 0.000 claims description 2
- 230000000873 masking effect Effects 0.000 claims description 2
- 230000003746 surface roughness Effects 0.000 abstract description 3
- 238000003776 cleavage reaction Methods 0.000 abstract description 2
- 230000007017 scission Effects 0.000 abstract description 2
- 239000002344 surface layer Substances 0.000 abstract description 2
- 238000005406 washing Methods 0.000 description 12
- 239000011521 glass Substances 0.000 description 11
- 229910052751 metal Inorganic materials 0.000 description 11
- 239000002184 metal Substances 0.000 description 11
- 230000003287 optical effect Effects 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 6
- 238000012545 processing Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000005566 electron beam evaporation Methods 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 238000002791 soaking Methods 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000013590 bulk material Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000005468 ion implantation Methods 0.000 description 2
- 238000010884 ion-beam technique Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229940031993 lithium benzoate Drugs 0.000 description 2
- LDJNSLOKTFFLSL-UHFFFAOYSA-M lithium;benzoate Chemical compound [Li+].[O-]C(=O)C1=CC=CC=C1 LDJNSLOKTFFLSL-UHFFFAOYSA-M 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000000206 photolithography Methods 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229960004365 benzoic acid Drugs 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 239000012792 core layer Substances 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 238000001312 dry etching Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005459 micromachining Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- QPJSUIGXIBEQAC-UHFFFAOYSA-N n-(2,4-dichloro-5-propan-2-yloxyphenyl)acetamide Chemical compound CC(C)OC1=CC(NC(C)=O)=C(Cl)C=C1Cl QPJSUIGXIBEQAC-UHFFFAOYSA-N 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 229940116315 oxalic acid Drugs 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
- C30B33/08—Etching
- C30B33/10—Etching in solutions or melts
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00388—Etch mask forming
- B81C1/00396—Mask characterised by its composition, e.g. multilayer masks
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00436—Shaping materials, i.e. techniques for structuring the substrate or the layers on the substrate
- B81C1/00523—Etching material
- B81C1/00539—Wet etching
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/14—Metallic material, boron or silicon
- C23C14/18—Metallic material, boron or silicon on other inorganic substrates
- C23C14/185—Metallic material, boron or silicon on other inorganic substrates by cathodic sputtering
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
- C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
- C30B29/22—Complex oxides
- C30B29/30—Niobates; Vanadates; Tantalates
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B31/00—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor
- C30B31/04—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor by contacting with diffusion materials in the liquid state
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Optical Integrated Circuits (AREA)
Abstract
The invention discloses a method for preparing a micro-nano device on the surface of a thin film lithium niobate, which comprises the following steps: forming chromium films on the upper surface and the lower surface of the cleaned and dried film lithium niobate substrate respectively, wherein the chromium films are used as masks on the upper surface and protective layers on the lower surface; transferring the pattern of the photoetching plate onto an upper surface mask, and then placing the substrate into a proton exchange furnace for proton exchange; after cooling the substrate subjected to proton exchange, sealing the periphery of the substrate by using a protective material; placing the sealed film lithium niobate substrate into a mixed solution of hydrofluoric acid and nitric acid for wet etching; and removing the mask on the upper surface, the protective layer on the lower surface and the periphery seal, and performing end face treatment by using a chemical mechanical polishing process after dicing and cleavage of the substrate. According to the invention, the proton exchange process is combined with the wet process to etch the thin film lithium niobate material to prepare the micro-nano device, so that the etching rate of lithium niobate can be greatly accelerated, and the thin film lithium niobate-based micro-nano device with excellent performance and low surface roughness is obtained.
Description
Technical Field
The invention relates to the technical field of micro-nano processing, in particular to a method for preparing a micro-nano device on the surface of a thin film lithium niobate.
Background
The lithium niobate crystal is a negative uniaxial crystal, has non-central symmetry, has a wider wavelength transmission range of about 350-5500 nm, has excellent piezoelectric, dielectric, ferroelectric, electrooptical, acousto-optic and nonlinear optical properties, is a ferroelectric material with the best comprehensive index, and is named as optical silicon. The traditional lithium niobate material has mature development of related technology and has been widely applied in the fields of modulators, fiber optic gyroscopes, fiber optic sensing and the like. The Lithium Niobate On Insulator (LNOI) prepared by adopting ion implantation and wafer bonding technology is used as a novel film material, has the advantages of high monocrystal performance, large refractive index difference between a waveguide core layer and a cladding layer (about 0.7), strong light limiting capability, capability of achieving micro-nano size and the like, and is an ideal platform for developing large-scale integrated photoelectronic devices; currently, researchers have implemented Y-branch optical waveguides, electro-optic modulators, micro-ring resonators, second harmonic generators, and the like on LNOI substrates, respectively.
At present, a lithium niobate-based micro-nano device based on a traditional bulk material is mainly prepared by adopting two methods of proton exchange and titanium (Ti) diffusion based on a diffusion technology, and the whole size of the device is larger due to the constraint of weak wave conduction, so that the device is not suitable for the development trend of the current photon monolithic integration. The film lithium niobate is one of the most potential materials in integrated optics, and because of the stable physical and chemical properties of the lithium niobate, the direct preparation of the micro-nano structure on the film lithium niobate is difficult by adopting a dry etching technology, and lithium (Li) ions in the crystal can be combined with fluorine (F) ions in etching gas to generate lithium fluoride (LiF) on the surface, so that the etching is prevented from continuing and the etching side wall is rough; the method is limited by the influence of bonding strength among heterogeneous materials, and the temperature (higher than 1000 ℃) involved in the Ti diffusion preparation method of the traditional bulk material is far higher than the highest temperature (500 ℃) which can be born by the thin film lithium niobate; although the proton exchange preparation method successfully verifies the feasibility of the proton exchange preparation method on a thin film lithium niobate material in 2015 by Lutong Cai et al of Shandong university, the refractive index difference of the prepared optical waveguide is still small (about 0.149), the refractive index of abnormal light can only be improved, and the prepared micro-nano device can only support one polarization mode. Other processing methods, such as ion implantation assisted etching, focused ion beam, femtosecond laser micromachining combined with focused ion beam, etc., require additional auxiliary processes, add to the processing costs to some extent, and are not compatible with conventional lithium niobate material processing lines.
Wet etching as a common processing means for semiconductor processes, as early as 1992, laurell et al verified that proton exchanged lithium niobate crystals can be treated with hydrofluoric acid (HF) and nitric acid (HNO) 3 ) For more than twenty years, a plurality of researchers perform optimization exploration on the wet etching process of the lithium niobate material, and a mature theoretical system is used as a supporting foundation at present.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for preparing a micro-nano device on the surface of thin film lithium niobate.
The invention provides a method for preparing a micro-nano device on the surface of a thin film lithium niobate, which comprises the following steps:
cleaning and drying the thin film lithium niobate substrate;
forming chromium films on the upper surface and the lower surface of the cleaned and dried film lithium niobate substrate respectively, wherein the chromium films are used as masks on the upper surface and protective layers on the lower surface;
transferring the pattern of the photoetching plate onto a mask on the upper surface;
putting the thin film lithium niobate substrate with the upper surface provided with the photoetching pattern into a proton exchange furnace for proton exchange;
after cooling the proton-exchanged thin film lithium niobate substrate, sealing the periphery of the substrate by using a protective material;
placing the sealed film lithium niobate substrate into a mixed solution of hydrofluoric acid and nitric acid for wet etching;
and removing the mask on the upper surface, the protective layer on the lower surface and the periphery seal, and performing end face treatment by using a chemical mechanical polishing process after dicing and cleavage of the substrate.
As a further improvement of the invention, the upper and lower surfaces of the cleaned and dried thin film lithium niobate substrate are respectively formed with chromium films; comprising the following steps:
respectively depositing chromium films on the upper and lower surfaces of the cleaned and dried film lithium niobate substrate by magnetron sputtering; or alternatively, the first and second heat exchangers may be,
and respectively evaporating chromium films on the upper and lower surfaces of the cleaned and dried thin film lithium niobate substrate by adopting electron beam evaporation.
As a further improvement of the invention, the thickness of the upper and lower surface chromium films is 100-320 nm.
As a further improvement of the present invention, said transferring the lithographic plate pattern onto the top surface mask comprises:
masking and spin-coating photoresist on the upper surface of the thin film lithium niobate substrate;
and transferring the pattern of the photoetching plate onto the upper surface mask after photoetching, developing and hardening the film lithium niobate substrate.
As a further improvement of the present invention, the lithography includes one of electron beam exposure and ultraviolet exposure.
As a further improvement of the invention, the proton source of the proton exchange comprises a molten solution of benzoic acid, pyrophosphoric acid, oxalic acid or a mixed acid thereof, and the exchange temperature of the proton exchange is 200-250 ℃.
As a further improvement of the present invention, the protective material is a material resistant to corrosion by hydrofluoric acid and nitric acid, including fluorine grease or paraffin wax.
As a further improvement of the invention, the volume ratio of the hydrofluoric acid to the nitric acid solution is 1:2, and the etching depth of the wet etching does not exceed the proton exchange depth.
As a further improvement of the present invention, the chemical mechanical polishing includes coarse grinding, fine grinding and polishing, and the grinding liquid and the polishing liquid are respectively Al 2 O 3 Polishing liquid and SiO 2 And (5) grinding liquid.
As a further improvement of the invention, the micro-nano device has dimensions on the order of submicron.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the proton exchange process is combined with the wet process to etch the thin film lithium niobate material to prepare the micro-nano device, so that the etching rate of lithium niobate can be greatly accelerated, and the thin film lithium niobate-based micro-nano device with excellent performance and low surface roughness is obtained; meanwhile, the method has no additional introduction of any complex process, and can be directly compatible with the existing lithium niobate material processing process line.
Drawings
FIG. 1 is a flow chart of a method for preparing a micro-nano device on the surface of a thin film lithium niobate according to an embodiment of the present invention;
FIG. 2 is a process diagram of a method for fabricating a micro-nano device on a thin film lithium niobate surface according to an embodiment of the present invention;
FIG. 3 is a cross-sectional electron scanning mirror (SEM) image of a thin film lithium niobate substrate fabricated by a post-proton exchange wet etching fabrication method for fabricating a ridge optical waveguide in accordance with one embodiment of the present invention;
fig. 4 is an atomic force scanning mirror (AFM) diagram of a thin film lithium niobate substrate prepared by a post-proton exchange wet etching preparation method for fabricating a ridge optical waveguide in accordance with an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention is described in further detail below with reference to the attached drawing figures:
as shown in fig. 1 and 2, the invention provides a method for preparing a micro-nano device on the surface of a thin film lithium niobate, which comprises the following steps:
step 1, cleaning and drying a thin film lithium niobate substrate;
wherein,
the bottom supporting layer of the film lithium niobate substrate is a Si or LN layer, and the middle insulating layer is SiO 2 The layer and the top layer are LN layers;
the cleaning and drying method of the thin film lithium niobate substrate comprises the following steps: firstly, soaking the glass by using the prepared glass washing liquid, then, sequentially carrying out water bath in an acetone solution, an ethanol solution and hydrogen peroxide, finally, washing the glass in deionized water, drying and naturally cooling.
Step 2, forming chromium films on the upper and lower surfaces of the cleaned and dried thin film lithium niobate substrate respectively, wherein the chromium films serve as a mask on the upper surface and a protective layer on the lower surface, as shown in (a) of fig. 2;
wherein,
forming chromium films on the upper and lower surfaces of the cleaned and dried film lithium niobate substrate respectively; comprising the following steps: respectively depositing chromium films on the upper and lower surfaces of the cleaned and dried film lithium niobate substrate by magnetron sputtering; or, evaporating chromium films on the upper and lower surfaces of the cleaned and dried thin film lithium niobate substrate by adopting electron beam evaporation. Further, the thickness of the chromium film on the upper surface and the lower surface is 100-320 nm; further, the magnetron sputtering process has better metal adhesion than electron beam evaporation.
Step 3, transferring the pattern of the photoetching plate onto a mask on the upper surface, as shown in (b) - (e) in fig. 2;
the method specifically comprises the following steps:
spin-coating photoresist on the upper surface mask of the thin film lithium niobate substrate, and transferring the pattern of the photoetching plate onto the upper surface mask after photoetching, developing, hardening and other processes are carried out on the thin film lithium niobate substrate. Further, photolithography includes one of electron beam exposure, ultraviolet exposure, and general photolithography; generally, electron beam exposure is often used in photonic integrated designs due to the small device feature size.
Step 4, putting the thin film lithium niobate substrate with the photoetching pattern on the upper surface into a benzene proton exchange furnace for proton exchange, as shown in (f) in fig. 2;
wherein,
proton sources for proton exchange comprise molten solutions of benzoic acid, pyrophosphoric acid, oxalic acid, lithium benzoate or mixtures thereof, and the exchange temperature of the proton exchange is 200-250 ℃.
Step 5, cooling the proton-exchanged thin film lithium niobate substrate, and sealing the periphery of the substrate by using a protective material;
wherein,
after the proton exchange film lithium niobate substrate is naturally cooled, the periphery of the substrate is protected by using a protective material resistant to hydrofluoric acid and nitric acid corrosion, so that an oxygen buried layer SiO in the substrate is avoided during wet corrosion 2 Underetching damage; further, the protective material includes one of a fluorine resin and a paraffin wax.
Step 6, placing the sealed film lithium niobate substrate into a mixed solution of hydrofluoric acid and nitric acid to carry out wet etching according to the design of the device, as shown in (g) of fig. 2;
wherein,
the mass ratio of hydrofluoric acid to nitric acid is 1:2, and the etching depth of wet etching does not exceed the proton exchange depth; furthermore, the etching process can be assisted in adopting processes such as heating, ultrasonic and the like to accelerate the etching efficiency.
Step 7, removing the mask on the upper surface, the protective layer on the lower surface and the periphery seal, and performing end face treatment by using a chemical mechanical polishing process after dicing and cleaving the substrate, as shown in (h) of fig. 2;
wherein,
the chemical mechanical polishing comprises coarse grinding, fine grinding and polishing, wherein the grinding fluid and the polishing fluid are respectively Al 2 O 3 Polishing liquid and SiO 2 The size of the grinding liquid and the micro-nano device is submicron.
Example 1
Selecting an X-cut LNOI substrate, wherein the structure is a Si layer with a bottom supporting layer of 500 mu m and an intermediate insulating layer is a SiO with a thickness of 2 mu m 2 The layer and the top layer are LN layers with the thickness of 500nm and are made of an insulating layer SiO 2 The large refractive index difference of the layers and the LN layer places a strong limit on the light transmitted by the waveguide core.
A method for preparing a micro-nano device on the surface of a thin film lithium niobate, comprising the following steps:
s11, cleaning and drying the thin film lithium niobate substrate; the method comprises the following specific steps: firstly, soaking the prepared glass washing liquid for 10 minutes, then respectively carrying out water bath for 10 minutes at 60 ℃ in an acetone solution and water bath for 10 minutes at 80 ℃ in an ethanol solution, then placing the glass washing liquid in hydrogen peroxide for 10 minutes at 80 ℃, finally washing the glass washing liquid in deionized water, drying and naturally cooling the glass washing liquid;
s12, firstly depositing a metal chromium film with the thickness of 100nm on the lower surface of the substrate by adopting magnetron sputtering as a protective film, and then depositing a metal chromium film with the thickness of 280nm on the upper surface of the substrate as a mask;
s13, uniformly spin-coating HSQ FOX-16 photoresist on the surface of the substrate at a proper rotating speed, exposing, developing and hardening the substrate under proper accelerating voltage and beam current by using an electron beam exposure machine, and transferring a designed photoetching plate pattern onto a metal mask on the upper surface of the substrate;
s14, placing the substrate into a molten benzoic acid solution, carrying out proton exchange according to the designed depth of the device at the temperature of 240 ℃, and taking out and naturally cooling;
s15, placing the substrate on a hot plate, sealing the periphery of the substrate by using paraffin under a specific clamp, and protecting the buried SiO in the middle of the thin film lithium niobate substrate 2 A layer;
s16, placing the thin film lithium niobate substrate in mixed solution of hydrofluoric acid and nitric acid in a ratio of 1:2, and carrying out wet etching according to the required etching depth;
s17, removing the metal chromium films on the upper surface and the lower surface of the substrate by using chromium corrosive liquid, removing the peripheral paraffin by using ethanol water bath, drying the metal chromium films, putting the metal chromium films into a cutting machine, dicing and cleaving the substrate according to the position of a cutting channel, and then using Al 2 O 3 And SiO 2 And (5) carrying out end face treatment on the grinding liquid to finally obtain the required optical structure chip.
Example 2
The Z-cut LNOI substrate is selected, and the structure is a Si layer with a bottom supporting layer of 500 mu m, an SiO2 layer with a thickness of 2 mu m as an intermediate insulating layer and an LN layer with a thickness of 400nm as a top layer. By means of insulating layers SiO 2 The large refractive index difference of the layers and the LN layer places a strong limit on the light transmitted by the waveguide core.
A method for preparing a micro-nano device on the surface of a thin film lithium niobate, comprising the following steps:
s21, cleaning and drying the thin film lithium niobate substrate; the method comprises the following specific steps: firstly, soaking the prepared glass washing liquid for 10 minutes, then respectively carrying out water bath for 10 minutes at 60 ℃ in an acetone solution and water bath for 10 minutes at 80 ℃ in an ethanol solution, then placing the glass washing liquid in hydrogen peroxide for 10 minutes at 80 ℃, finally washing the glass washing liquid in deionized water, drying and naturally cooling the glass washing liquid;
s22, adopting an electron beam evaporation technology to evaporate a metal chromium film with the thickness of 100nm on the lower surface of the substrate to serve as a protective film, and evaporating a metal chromium film with the thickness of 280nm on the upper surface of the substrate to serve as a mask;
s23, uniformly spin-coating AZ5214 photoresist on the surface of the substrate at a proper rotating speed, and then using an ultraviolet exposure machine to perform processes such as exposure, development, hardening and the like on the substrate at a proper exposure time, so as to transfer a designed photoetching plate pattern onto a metal mask on the upper surface of the substrate;
s24, placing the substrate into a molten benzoic acid/lithium benzoate solution, carrying out proton exchange according to the designed depth of the device at the temperature of 240 ℃, and taking out and naturally cooling;
s25, placing the substrate on a hot plate, sealing the periphery of the substrate by using fluorine grease under a specific clamp, and protecting the buried SiO in the middle of the thin film lithium niobate substrate 2 A layer;
s26, placing the thin film lithium niobate substrate with the bottom surface and the peripheral edges protected in mixed solution of hydrofluoric acid and nitric acid in a ratio of 1:2, performing wet etching according to the required etching depth, and heating in a water bath to achieve the purpose of increasing the etching rate if necessary;
s27, removing metal chromium films on the upper surface and the lower surface of the substrate by using chromium corrosive liquid, removing the peripheral fluorine grease by using acetone and ethanol water bath, drying the substrate, putting the substrate into a cutting machine, scribing and cleaving the substrate according to the position of a cutting channel, and then using Al 2 O 3 And SiO 2 And (5) carrying out end face treatment on the grinding liquid to finally obtain the required optical structure chip.
The invention provides a ridge optical waveguide prepared based on the method, wherein a cross-section electron scanning mirror (SEM) diagram of the ridge optical waveguide is shown in fig. 3, and an atomic force scanning mirror (AFM) diagram is shown in fig. 4.
The invention has the advantages that:
according to the invention, the proton exchange process is combined with the wet process to etch the thin film lithium niobate material to prepare the micro-nano device, so that the etching rate of lithium niobate can be greatly accelerated, and the thin film lithium niobate-based micro-nano device with excellent performance and low surface roughness is obtained; meanwhile, the method has no additional introduction of any complex process, and can be directly compatible with the existing lithium niobate material processing process line.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. The method for preparing the micro-nano device on the surface of the thin film lithium niobate is characterized by comprising the following steps of:
cleaning and drying the thin film lithium niobate substrate; wherein the bottom supporting layer of the thin film lithium niobate substrate is a Si or LN layer, and the middle insulating layer is SiO 2 The layer and the top layer are LN layers;
respectively depositing chromium films on the upper surface and the lower surface of the cleaned and dried thin film lithium niobate substrate by magnetron sputtering to serve as a mask on the upper surface and a protective layer on the lower surface;
masking and spin-coating photoresist on the upper surface of the thin film lithium niobate substrate; transferring the pattern of the photoetching plate onto an upper surface mask after the thin film lithium niobate substrate is subjected to electron beam exposure, development and hardening;
putting the thin film lithium niobate substrate with the upper surface provided with the photoetching pattern into a proton exchange furnace for proton exchange; wherein the proton source of the proton exchange comprises a molten solution of benzoic acid, pyrophosphoric acid, oxalic acid or mixed acid thereof, and the exchange temperature of the proton exchange is 200-250 ℃;
after cooling the proton-exchanged thin film lithium niobate substrate, sealing the periphery of the substrate by using a protective material;
placing the sealed film lithium niobate substrate into a mixed solution of hydrofluoric acid and nitric acid for wet etching; wherein the solution volume ratio of hydrofluoric acid to nitric acid is 1:2, and the etching depth of the wet etching does not exceed the proton exchange depth;
removing a chromium film and peripheral seals of the substrate, and performing end face treatment by using a chemical mechanical polishing process after dicing and cleaving the substrate; wherein the chemical mechanical polishing comprises coarse grinding, fine grinding and polishing, and the grinding fluid and the polishing fluid are respectively Al 2 O 3 Polishing liquid and SiO 2 Grinding fluid; the micro-nano device has a size of submicron order.
2. The method for preparing a micro-nano device on the surface of the thin film lithium niobate according to claim 1, wherein the thickness of the upper and lower surface chromium films is 100-320 nm.
3. The method for preparing a micro-nano device on the surface of the thin film lithium niobate according to claim 1, wherein the protective material is a material resistant to corrosion by hydrofluoric acid and nitric acid, and comprises fluorine grease or paraffin.
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| JPS63250611A (en) * | 1987-04-08 | 1988-10-18 | Sumitomo Electric Ind Ltd | Production of light guide |
| CN110286439A (en) * | 2019-07-02 | 2019-09-27 | 山东大学 | The method of optical waveguide quantum chip is formed on gradual period poled lithium tantalate using proton exchange method |
| CN112965166A (en) * | 2021-03-08 | 2021-06-15 | 天津大学 | Z-cut lithium niobate tapered waveguide and preparation method thereof |
| CN114690316A (en) * | 2022-04-12 | 2022-07-01 | 山东建筑大学 | Etching process method for waveguide in quantum communication |
| CN114755761A (en) * | 2022-04-27 | 2022-07-15 | 北京航空航天大学 | Preparation method of lithium niobate thin film submicron line width ridge type optical waveguide based on chromium mask |
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| JPS63250611A (en) * | 1987-04-08 | 1988-10-18 | Sumitomo Electric Ind Ltd | Production of light guide |
| CN110286439A (en) * | 2019-07-02 | 2019-09-27 | 山东大学 | The method of optical waveguide quantum chip is formed on gradual period poled lithium tantalate using proton exchange method |
| CN112965166A (en) * | 2021-03-08 | 2021-06-15 | 天津大学 | Z-cut lithium niobate tapered waveguide and preparation method thereof |
| CN114690316A (en) * | 2022-04-12 | 2022-07-01 | 山东建筑大学 | Etching process method for waveguide in quantum communication |
| CN114755761A (en) * | 2022-04-27 | 2022-07-15 | 北京航空航天大学 | Preparation method of lithium niobate thin film submicron line width ridge type optical waveguide based on chromium mask |
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