CN115182052A - 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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- CN115182052A CN115182052A CN202210928731.7A CN202210928731A CN115182052A CN 115182052 A CN115182052 A CN 115182052A CN 202210928731 A CN202210928731 A CN 202210928731A CN 115182052 A CN115182052 A CN 115182052A
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- lithium niobate
- 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 89
- 239000010409 thin film Substances 0.000 title claims abstract description 76
- 238000000034 method Methods 0.000 title claims abstract description 53
- 239000000758 substrate Substances 0.000 claims abstract description 81
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 31
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 31
- 239000011651 chromium Substances 0.000 claims abstract description 31
- 239000010408 film Substances 0.000 claims abstract description 31
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 27
- 239000000463 material Substances 0.000 claims abstract description 24
- 238000001259 photo etching Methods 0.000 claims abstract description 17
- 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
- 238000001039 wet etching Methods 0.000 claims abstract description 13
- 239000000126 substance Substances 0.000 claims abstract description 11
- 238000001816 cooling Methods 0.000 claims abstract description 9
- 230000001681 protective effect Effects 0.000 claims abstract description 9
- 239000011259 mixed solution Substances 0.000 claims abstract description 7
- 239000011241 protective layer Substances 0.000 claims abstract description 7
- 238000007789 sealing Methods 0.000 claims abstract description 6
- 230000002093 peripheral effect Effects 0.000 claims abstract description 5
- 238000007517 polishing process Methods 0.000 claims abstract description 4
- 238000003776 cleavage reaction Methods 0.000 claims abstract description 3
- 230000007017 scission Effects 0.000 claims abstract description 3
- 239000000243 solution Substances 0.000 claims description 15
- 238000000227 grinding Methods 0.000 claims description 14
- 239000007788 liquid Substances 0.000 claims description 14
- 238000005498 polishing Methods 0.000 claims description 12
- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 claims description 10
- 238000001035 drying Methods 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 7
- 239000012188 paraffin wax Substances 0.000 claims description 7
- 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
- 238000005566 electron beam evaporation Methods 0.000 claims description 5
- 238000010894 electron beam technology Methods 0.000 claims description 5
- 238000001704 evaporation Methods 0.000 claims description 5
- 239000004519 grease Substances 0.000 claims description 5
- 238000001755 magnetron sputter deposition Methods 0.000 claims description 5
- 229920002120 photoresistant polymer Polymers 0.000 claims description 5
- 230000007797 corrosion Effects 0.000 claims description 3
- 238000005260 corrosion Methods 0.000 claims description 3
- 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
- 238000009987 spinning Methods 0.000 claims description 3
- 239000002253 acid Substances 0.000 claims description 2
- 230000003746 surface roughness Effects 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 30
- 239000011521 glass Substances 0.000 description 13
- 238000005406 washing Methods 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 11
- 239000002184 metal Substances 0.000 description 11
- 230000003287 optical effect Effects 0.000 description 10
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 8
- 238000012545 processing Methods 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 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
- 239000013078 crystal Substances 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 238000005520 cutting process Methods 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 238000001459 lithography 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
- 238000007664 blowing Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000001312 dry etching 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
- 230000010354 integration Effects 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
- 238000002360 preparation method Methods 0.000 description 2
- 238000004528 spin coating 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
- 239000013590 bulk material Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method 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
- 239000007789 gas Substances 0.000 description 1
- 239000012212 insulator Substances 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
- 238000005459 micromachining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 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
- 230000005693 optoelectronics Effects 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
- 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
- 229910052905 tridymite Inorganic materials 0.000 description 1
Images
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
Abstract
The invention discloses a method for preparing a micro-nano device on the surface of thin film lithium niobate, which comprises the following steps: respectively forming chromium films on the upper surface and the lower surface of the cleaned and dried thin-film lithium niobate substrate, wherein the chromium films are used as a mask on the upper surface and a protective layer on the lower surface; transferring the pattern of the photoetching plate to an upper surface mask, and then putting the substrate into a proton exchange furnace for proton exchange; cooling the substrate after proton exchange, and sealing the periphery of the substrate by using a protective material; putting the sealed thin 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 peripheral seal, and carrying out end face treatment by using a chemical mechanical polishing process after the substrate is subjected to scribing and cleavage. According to the invention, a proton exchange process is combined with a 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 increased, 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 thin film lithium niobate.
Background
The lithium niobate crystal is a negative uniaxial crystal, has non-centrosymmetry, has a wide 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 has the title of optical silicon. The traditional lithium niobate material has mature related technology development and is widely applied to the fields of modulators, fiber optic gyroscopes, fiber optic sensors and the like. Lithium Niobate On Insulator (LNOI) prepared by adopting ion implantation and wafer bonding technology is used as a new thin film material, has the advantages of high single crystal performance, large refractive index difference (about 0.7) between a waveguide core layer and a cladding layer, strong light limiting capability, capability of realizing micro-nano size and the like, and is an ideal platform for developing large-scale integrated optoelectronic devices; at present, researchers have implemented Y-branch optical waveguides, electro-optical modulators, micro-ring resonators, second harmonic generators, and the like on LNOI substrates, respectively.
At present, the lithium niobate-based micro-nano device based on the traditional body material is mainly prepared by two methods of proton exchange and titanium (Ti) diffusion based on the diffusion technology, and the weak waveguide constraint causes the whole size of the device to be larger, so that the lithium niobate-based micro-nano device is not suitable for the current development trend of photonic monolithic integration. The thin film lithium niobate is one of the most potential materials in integrated optics, and due to the stable physicochemical property of the lithium niobate, it is difficult to directly prepare a micro-nano structure on the thin film lithium niobate by adopting a dry etching technology, and lithium fluoride (LiF) is generated on the surface of the thin film lithium niobate by combining lithium (Li) ions in crystals with fluorine (F) ions in etching gas in the dry etching process, so that the etching is prevented from continuing and the etching side wall is rough; the temperature (higher than 1000 ℃) related to the Ti diffusion preparation method of the traditional bulk material is far beyond the highest temperature (500 ℃) which can be born by the thin film lithium niobate because of the influence of bonding strength among heterogeneous materials; although the proton exchange preparation method successfully verifies feasibility of the thin-film lithium niobate material by Lutong Cai and the like of Shandong university in 2015, the refractive index difference of the prepared optical waveguide is still small (about 0.149), the refractive index of the abnormal light can be only 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. all require additional auxiliary processes, increase the processing cost to a certain extent, and are incompatible with the conventional lithium niobate material processing line.
Wet etching, a commonly used processing means for semiconductor processing, was as early as 1992, laurell et al verified that proton exchanged lithium niobate crystals could be converted to hydrofluoric acid (HF) and nitric acid (HNO) 3 ) The mixed solution is etched, and then, in more than twenty years, scientific researchers optimize and explore the wet etching process of the lithium niobate material, and at present, a mature theoretical system is used as a supporting foundation.
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 thin film lithium niobate, which comprises the following steps:
cleaning and drying the thin film lithium niobate substrate;
respectively forming chromium films on the upper surface and the lower surface of the cleaned and dried thin-film lithium niobate substrate, wherein the chromium films are used as a mask on the upper surface and a protective layer on the lower surface;
transferring the pattern of the photoetching plate to an upper surface mask;
putting the thin-film lithium niobate substrate with the photoetching pattern on the upper surface into a proton exchange furnace for proton exchange;
cooling the thin film lithium niobate substrate after proton exchange, and sealing the periphery of the substrate by using a protective material;
placing the sealed thin-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 peripheral seal, and carrying out end face treatment by using a chemical mechanical polishing process after the substrate is subjected to scribing and cleavage.
As a further improvement of the invention, chromium films are respectively formed on the upper surface and the lower surface of the cleaned and dried thin-film lithium niobate substrate; the method comprises the following steps:
respectively depositing chromium films on the upper surface and the lower surface of the cleaned and dried thin-film lithium niobate substrate by adopting magnetron sputtering; or the like, or a combination thereof,
and respectively evaporating chromium films on the upper surface and the lower surface 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 chromium films on the upper surface and the lower surface is 100-320 nm.
As a further improvement of the present invention, the transferring of the reticle pattern onto the upper surface mask comprises:
a photoresist is coated on the upper surface of the thin film lithium niobate substrate in a spinning mode;
and after photoetching, developing and hardening the thin-film lithium niobate substrate, transferring the pattern of the photoetching plate to an upper surface mask.
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 exchange proton source 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 ℃.
As a further improvement of the invention, the protective material is a material which resists the corrosion of hydrofluoric acid and nitric acid and comprises fluorine grease or paraffin.
As a further improvement of the invention, the volume ratio of the hydrofluoric acid solution 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 invention, 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 And (3) grinding liquid.
As a further improvement of the invention, the size of the micro-nano device is in submicron order.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, a proton exchange process is combined with a 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 increased, and the thin film lithium niobate-based micro-nano device with excellent performance and low surface roughness is obtained; meanwhile, no complex process is additionally introduced, so that the method can be directly compatible with the existing lithium niobate material processing process line.
Drawings
Fig. 1 is a flowchart of a method for preparing a micro-nano device on a thin film lithium niobate surface according to an embodiment of the present invention;
fig. 2 is a process diagram of a method for preparing a micro-nano device on the surface of thin film lithium niobate according to an embodiment of the present invention;
FIG. 3 is a cross-sectional electron scanning microscope (SEM) view of a spinal optical waveguide fabricated by a proton exchange post-wet etching method using a thin film lithium niobate substrate according to an embodiment of the present invention;
fig. 4 is an atomic force scanning mirror (AFM) diagram of a spinal optical waveguide prepared by a thin film lithium niobate substrate using a wet etching method after proton exchange according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present 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 thin film lithium niobate, which comprises the following steps:
wherein, the first and the second end of the pipe are connected with each other,
the bottom layer 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;
the cleaning and drying method of the thin film lithium niobate substrate comprises the following steps: 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 cleanly under deionized water, drying the glass and naturally cooling the glass.
Step 2, forming chromium films on the upper surface and the lower surface of the cleaned and dried thin film lithium niobate substrate respectively, wherein the chromium films are used as a mask on the upper surface and a protective layer on the lower surface, as shown in (a) in fig. 2;
wherein the content of the first and second substances,
respectively forming chromium films on the upper surface and the lower surface of the cleaned and dried thin film lithium niobate substrate; the method comprises the following steps: respectively depositing chromium films on the upper surface and the lower surface of the cleaned and dried thin film lithium niobate substrate by adopting magnetron sputtering; or, respectively evaporating chromium films on the upper surface and the lower surface 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; furthermore, the metal adhesion of the magnetron sputtering process is superior to that of electron beam evaporation.
Step 3, transferring the pattern of the photoetching plate to an upper surface mask, as shown in (b) to (e) of fig. 2;
the method specifically comprises the following steps:
and (3) coating photoresist on the upper surface mask of the thin film lithium niobate substrate in a spinning mode, and transferring the pattern of the photoetching plate to the upper surface mask after the processes of photoetching, developing, hardening and the like are carried out on the thin film lithium niobate substrate. Further, the lithography includes one of electron beam exposure, ultraviolet exposure, and general lithography; generally, electron beam exposure is often used in photonic integration design due to the small feature size of the device.
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 the content of the first and second substances,
the proton exchange proton source comprises benzoic acid, pyrophosphoric acid, oxalic acid, lithium benzoate or mixed molten solution thereof, and the exchange temperature of proton exchange is 200-250 ℃.
Step 5, cooling the thin film lithium niobate substrate after proton exchange, and sealing the periphery of the substrate by using a protective material;
wherein, the first and the second end of the pipe are connected with each other,
after the proton exchange thin film lithium niobate substrate is naturally cooled, the periphery of the substrate is protected by using a protection material which is resistant to hydrofluoric acid and nitric acid corrosion, so that an oxygen burying layer SiO in the substrate is prevented from being corroded by a wet method 2 Underetching damage; further, the protective material includes one of fluorine grease and paraffin.
Step 6, putting the sealed thin film lithium niobate substrate into a mixed solution of hydrofluoric acid and nitric acid for wet etching according to the design of a device, as shown in (g) of fig. 2;
wherein the content of the first and second substances,
the mass ratio of the hydrofluoric acid to the nitric acid is 1:2, and the etching depth of the wet etching does not exceed the proton exchange depth; furthermore, heating, ultrasonic and other processes can be adopted in an auxiliary manner in the etching process to accelerate the etching efficiency.
Step 7, removing the mask on the upper surface, the protective layer on the lower surface and the peripheral seal, dicing and cleaving the substrate, and then performing end face treatment by using a chemical mechanical polishing process, as shown in (h) of fig. 2;
wherein the content of the first and second substances,
the chemical mechanical polishing comprises coarse grinding, fine grinding and polishing, wherein the grinding liquid and the polishing liquid are respectively Al 2 O 3 Polishing liquid and SiO 2 The size of the grinding fluid and the micro-nano device is in submicron order.
Example 1
Selecting X-cut LNOI substrate with structure of 500 μm Si layer as bottom layer support layer and 2 μm thick SiO layer as intermediate insulating layer 2 The layer and the top layer are LN layers with the thickness of 500nm, and an insulating layer SiO is used 2 The large difference in refractive index of the layers and the LN layers strongly limits the transmitted light of the waveguide core.
A method for preparing a micro-nano device on the surface of thin film lithium niobate comprises the following steps:
s11, cleaning and drying the thin-film lithium niobate substrate; the method comprises the following specific steps: soaking the prepared glass washing liquor for 10 minutes, then respectively carrying out water bath in an acetone solution at 60 ℃ for 10 minutes and in an ethanol solution at 80 ℃ for 10 minutes, then putting the glass washing liquor in hydrogen peroxide at 80 ℃ for 10 minutes, finally washing the glass washing liquor cleanly under deionized water, and drying and naturally cooling the glass washing liquor;
s12, depositing a metal chromium film with the thickness of 100nm on the lower surface of the substrate as a protective film by adopting magnetron sputtering, and 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, then exposing, developing and hardening the substrate by using an electron beam exposure machine under proper accelerating voltage and beam current, and transferring the designed photoetching plate pattern to a metal mask on the upper surface of the substrate;
s14, putting the substrate into a molten benzoic acid solution, performing proton exchange at 240 ℃ according to the designed depth of the device, taking out the substrate, and naturally cooling the substrate;
s15, placing the substrate on a hot plate, sealing the periphery of the substrate by using paraffin under a specific fixture, 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 a mixed solution of hydrofluoric acid and nitric acid with 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 paraffin on the periphery by using ethanol water bath, blowing the paraffin to dry, placing the dried paraffin into a cutting machine, scribing and cleaving the substrate according to the positions of cutting channels, 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
A Z-cut LNOI substrate is selected, which has a structure comprising a 500 μm Si layer at the bottom support layer, a 2 μm thick SiO2 layer at the middle insulating layer, and a 400nm thick LN layer at the top. Using insulating layer SiO 2 The large difference in refractive index between the layers and the LN layer strongly confines the transmitted light of the waveguide coreAnd (5) preparing.
A method for preparing a micro-nano device on the surface of thin film lithium niobate comprises the following steps:
s21, cleaning and drying the thin-film lithium niobate substrate; the method comprises the following specific steps: soaking the prepared glass washing liquor for 10 minutes, then respectively carrying out water bath in an acetone solution at 60 ℃ for 10 minutes and in an ethanol solution at 80 ℃ for 10 minutes, then putting the glass washing liquor in hydrogen peroxide at 80 ℃ for 10 minutes, finally washing the glass washing liquor cleanly under deionized water, and drying and naturally cooling the glass washing liquor;
s22, evaporating a metal chromium film with the thickness of 100nm on the lower surface of the substrate as a protective film by adopting an electron beam evaporation technology, and evaporating a metal chromium film with the thickness of 280nm on the upper surface of the substrate as a mask;
s23, uniformly spin-coating AZ5214 photoresist on the surface of the substrate at a proper rotating speed, then carrying out processes such as exposure, development, hardening and the like on the substrate by using an ultraviolet exposure machine at a proper exposure time, and transferring the designed pattern of the photoetching plate to a metal mask on the upper surface of the substrate;
s24, putting the substrate into a molten benzoic acid/lithium benzoate solution, performing proton exchange at 240 ℃ according to the designed depth of the device, 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 edge protected in a mixed solution of hydrofluoric acid and nitric acid with the proportion of 1:2, carrying out wet etching according to the required etching depth, and optionally heating in a water bath to increase the etching rate;
s27, removing the metal chromium films on the upper surface and the lower surface of the substrate by using chromium corrosive liquid, removing fluorine grease on the periphery by using acetone and ethanol water bath, drying the metal chromium films in a blowing way, putting the metal chromium films into a cutting machine, scribing and cleaving the substrate according to the positions of cutting lines, 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-sectional electron scanning mirror (SEM) image of the ridge optical waveguide is shown in figure 3, and an atomic force scanning mirror (AFM) image is shown in figure 4.
The invention has the advantages that:
according to the invention, a proton exchange process is combined with a 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 increased, and the thin film lithium niobate-based micro-nano device with excellent performance and low surface roughness is obtained; meanwhile, no complex process is additionally introduced, so that the method can be directly compatible with the existing lithium niobate material processing process line.
The present invention has been described in terms of the preferred embodiment, and it is not intended to be limited to the embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for preparing a micro-nano device on the surface of thin film lithium niobate is characterized by comprising the following steps:
cleaning and drying the thin-film lithium niobate substrate;
respectively forming chromium films on the upper surface and the lower surface of the cleaned and dried thin-film lithium niobate substrate, wherein the chromium films are used as a mask on the upper surface and a protective layer on the lower surface;
transferring the pattern of the photoetching plate to an upper surface mask;
putting the thin-film lithium niobate substrate with the photoetching pattern on the upper surface into a proton exchange furnace for proton exchange;
cooling the thin film lithium niobate substrate after proton exchange, and sealing the periphery of the substrate by using a protective material;
putting the sealed thin film lithium niobate substrate into a mixed solution of hydrofluoric acid and nitric acid for wet etching;
and removing the chromium film and the peripheral seal of the substrate, and carrying out end face treatment by using a chemical mechanical polishing process after the substrate is subjected to scribing and cleavage.
2. The method for preparing a micro-nano device on the surface of thin film lithium niobate according to claim 1, wherein chromium films are respectively formed on the upper surface and the lower surface of the cleaned and dried thin film lithium niobate substrate; the method comprises the following steps:
respectively depositing chromium films on the upper surface and the lower surface of the cleaned and dried thin film lithium niobate substrate by adopting magnetron sputtering; or the like, or, alternatively,
and respectively evaporating chromium films on the upper surface and the lower surface of the cleaned and dried thin-film lithium niobate substrate by adopting electron beam evaporation.
3. The method for preparing a micro-nano device on the surface of the thin film lithium niobate according to claim 1 or 2, wherein the thickness of the chromium film on the upper surface and the lower surface is 100-320 nm.
4. The method for preparing a micro-nano device on the surface of the thin film lithium niobate of claim 1, wherein the transferring the pattern of the photoetching plate to the upper surface mask comprises the following steps:
a photoresist is coated on the upper surface of the thin film lithium niobate substrate in a spinning mode;
and after photoetching, developing and hardening the thin-film lithium niobate substrate, transferring the pattern of the photoetching plate to an upper surface mask.
5. The method for preparing a micro-nano device on the surface of the thin film lithium niobate according to claim 4, wherein the photoetching comprises one of electron beam exposure and ultraviolet exposure.
6. The method for preparing a micro-nano device on the surface of the thin film lithium niobate according to claim 1, wherein the proton exchange proton source 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 ℃.
7. The method for preparing a micro-nano device on the surface of 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.
8. The method for preparing a micro-nano device on the surface of the thin film lithium niobate of claim 1, wherein the volume ratio of the hydrofluoric acid to the nitric acid is 1:2, and the etching depth of the wet etching is not more than the proton exchange depth.
9. The method for preparing a micro-nano device on the surface of thin film lithium niobate according to claim 1, wherein the chemical mechanical polishing comprises 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 (3) grinding liquid.
10. The method for preparing the micro-nano device on the surface of the thin film lithium niobate according to claim 1, wherein the size of the micro-nano device is in a submicron order.
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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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