CN110703382A - High-integration-level lithium niobate/silicon nitride optical waveguide integrated structure and preparation method thereof - Google Patents

High-integration-level lithium niobate/silicon nitride optical waveguide integrated structure and preparation method thereof Download PDF

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CN110703382A
CN110703382A CN201910022839.8A CN201910022839A CN110703382A CN 110703382 A CN110703382 A CN 110703382A CN 201910022839 A CN201910022839 A CN 201910022839A CN 110703382 A CN110703382 A CN 110703382A
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silicon oxide
oxide layer
layer
lithium niobate
silicon
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CN110703382B (en
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李真宇
张秀全
张涛
李洋洋
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Huawei Technologies Co Ltd
Jinan Jingzheng Electronics Co Ltd
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Jinan Jingzheng Electronics Co Ltd
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    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
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    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
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    • 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
    • C23C14/48—Ion implantation
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    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
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    • C23C16/345—Silicon nitride
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    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/40—Oxides
    • C23C16/401—Oxides containing silicon
    • C23C16/402—Silicon dioxide
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    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/10—Oxidising
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12035—Materials
    • G02B2006/1204—Lithium niobate (LiNbO3)
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12166—Manufacturing methods
    • G02B2006/12176—Etching

Abstract

The method discloses a high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure and a preparation method thereof, and the high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a third silicon dioxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 10-100 nm; in the high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure, a silicon oxide layer of dozens of nanometers is arranged between the silicon nitride optical waveguide and the lithium niobate thin film, the silicon oxide layer has controllable thickness, small thickness deviation, smooth surface and good uniformity, and optical signals can be well coupled between the lithium niobate and the silicon nitride after the device is prepared, so that the prepared device has wide bandwidth, low loss and good device consistency.

Description

High-integration-level lithium niobate/silicon nitride optical waveguide integrated structure and preparation method thereof
Technical Field
The invention relates to the technical field of high-speed optical modulation chips of optical communication wave bands, in particular to a high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure and a preparation method thereof.
Background
With the development of science and technology and the arrival of the big data era, the demand on the broadband of a communication network is rapidly increased, and the demand on the integration level of devices is higher and higher. The lithium niobate crystal has large electro-optic coefficient, nonlinear optical coefficient, excellent photorefractive, piezoelectric and acoustic properties and low material cost, is widely applied to the aspect of optical modulators, and the modulator manufactured by integrating the lithium niobate and silicon nitride optical waveguides has low loss and wide application prospect in the aspect of manufacturing wide bandwidth chips.
The lithium niobate/silicon nitride optical waveguide integrated structure can be prepared into a modulator, has the characteristics of low loss and wide bandwidth, wherein the silicon nitride optical waveguide and the lithium niobate film are directly provided with a silicon oxide layer, the thickness and the precision of the silicon oxide layer directly influence the final performance of the device, the thickness of the silicon oxide layer is only tens of nanometers in general, the silicon oxide layer is connected with the lithium niobate thin film layer and the silicon nitride optical waveguide structure, optical signals can be coupled in the lithium niobate thin film layer and the silicon nitride optical waveguide through the silicon oxide layer, the thickness of the layer of silicon oxide is related to the design of the device, and because the layer of silicon oxide is the necessary path for coupling optical signals in the lithium niobate thin film layer and the silicon nitride optical waveguide structure, therefore, the quality of the layer of silicon oxide, such as thickness uniformity, thickness variation, surface quality, etc., has a great influence on the performance and uniformity of the final device.
At present, after an optical waveguide is prepared, a layer of silicon oxide is generally deposited by adopting a chemical vapor deposition method (PECVD), and then a Chemical Mechanical Polishing (CMP) is adopted to polish the silicon oxide layer to a required thickness, but in the actual preparation process, the defect of poor thickness controllability of the silicon oxide layer exists in the direct CMP, and due to the existence of the optical waveguide, the deposited silicon oxide surface is a rugged undulating surface, but the silicon oxide surface polished by the CMP still presents an undulating state, so that the thickness deviation of the silicon oxide layer is large, the thickness uniformity is poor, the surface flatness is poor, and the coupling of light in a lithium niobate and silicon nitride optical waveguide is uncontrollable, so that the consistency of a device is poor, and the device is not suitable for industrial production.
Disclosure of Invention
In order to solve the above problems, the present invention provides a high-integration lithium niobate/silicon nitride optical waveguide integrated structure and a method for manufacturing the same.
In order to achieve the purpose, the invention is realized by the following technical scheme:
the high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a third silicon dioxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 10-100 nm.
Preferably, the thickness of the fourth silicon oxide layer is 10-40 nm.
Preferably, the silicon substrate layer and the second silicon dioxide layer further comprise a first silicon oxide layer therebetween.
Preferably, the thickness of the silicon substrate layer is 0.2-1 mm, the thickness of the second silicon dioxide layer is 1-5 μm, the thickness of the third silicon oxide layer is 100-1000 nm, and the thickness of the lithium niobate thin film layer is 50-1000 nm.
Preferably, the total thickness of the first silicon oxide layer and the second silicon oxide layer is 1-5 μm; the thickness of the silicon substrate layer is 0.2-1 mm, the thickness of the third silicon oxide layer is 100-1000 nm, and the thickness of the lithium niobate thin film layer is 50-1000 nm.
The invention also comprises a preparation method of the high-integration lithium niobate/silicon nitride optical waveguide integrated structure, which comprises the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the fourth silicon oxide layer is prepared by a thermal oxidation method or a deposition method, and the thickness of the fourth silicon oxide layer is 10-100 nm;
② depositing a silicon nitride film on the fourth silicon oxide layer by deposition method, and preparing a silicon nitride waveguide layer by photolithography method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the thickness of the third silicon oxide layer is the same as that of the silicon nitride waveguide layer;
④ bonding the surface-polished silicon substrate to the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with a target thickness on the surface of the fourth silicon oxide layer to obtain the high-integration lithium niobate/silicon nitride optical waveguide integrated structure.
In a preferred method, step ④ is to deposit a first silicon oxide layer on the surface of the silicon substrate, and then to polish the first silicon oxide layer and bond it to the polished surface of the second silicon oxide layer.
Preferably, the method for bonding the lithium niobate thin film with the target thickness in step ⑥ is an intelligent lift-off method, and specifically comprises the steps of implanting ions into the lithium niobate crystal by using an ion implantation method, so that the lithium niobate crystal is divided into a thin film layer, a separation layer and a residual layer from top to bottom, bonding the lithium niobate thin film layer and the fourth silicon oxide layer by using a wafer bonding method, heating to separate the separation layer and the residual layer of the lithium niobate, and finally polishing the lithium niobate thin film layer, so that the lithium niobate thin film layer with the target thickness can be bonded on the surface of the fourth silicon oxide layer.
The preferable preparation method comprises the step of bonding the lithium niobate thin film with the target thickness in the step ⑥, namely bonding the LNOISI lithium niobate thin film with the polished upper surface with the surface of a fourth silicon oxide layer, wherein the lower surface of the LNOISI lithium niobate thin film is provided with a first sacrificial silicon oxide layer and a second sacrificial silicon substrate layer in sequence, and then removing the first sacrificial silicon oxide layer and the second sacrificial silicon substrate layer by adopting a grinding process and a wet etching process.
The preferred preparation method comprises the step of bonding the lithium niobate thin film with the target thickness in the step ⑥, namely bonding the LNOI lithium niobate thin film with the polished upper surface with the surface of a fourth silicon oxide layer, wherein the lower surface of the LNOI lithium niobate thin film is a second sacrificial silicon oxide layer and a sacrificial lithium niobate substrate layer, and then removing the second sacrificial silicon oxide layer and the sacrificial lithium niobate substrate layer by adopting a grinding process and a wet etching process.
Compared with the prior art, the invention has the following advantages:
in the high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure, a silicon oxide layer of dozens of nanometers is arranged between the silicon nitride optical waveguide and the lithium niobate thin film, the silicon oxide layer has controllable thickness, small thickness deviation, smooth surface and good uniformity, and optical signals can be well coupled between the lithium niobate and the silicon nitride after the device is prepared, so that the prepared device has wide bandwidth, low loss and good device consistency.
According to the preparation method of the high-integration lithium niobate/silicon nitride optical waveguide integrated structure, the fourth silicon oxide layer is formed on the silicon substrate by adopting a thermal oxidation method or a deposition method, the surface of the fourth silicon oxide bonded with the lithium niobate thin film has smaller thickness deviation, small surface roughness and good uniformity, and the bonding strength of the lithium niobate thin film and the silicon oxide layer is high, so that the integrated structure has higher stability and reliability in the subsequent process; the preparation method is ingenious in conception, but the operation steps are mature processes such as a deposition method and polishing, the steps are easy to operate, the preparation method is suitable for industrial production, and the yield is high.
According to the preparation method of the high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure, the quality of the final lithium niobate film is not influenced by the early process because the lithium niobate film is the film prepared by the last layer. The problems in the existing method are avoided: the silicon nitride optical waveguide can be deposited by an LPCVD method, the process temperature of the deposition method is higher (more than 800 ℃), the Curie temperature of the lithium niobate is only 1100 ℃, and the lithium niobate has the phenomena of surface domain inversion, Li loss and the like at higher temperature, so that the electro-optic performance of the lithium niobate is influenced.
Drawings
FIG. 1 is a schematic structural diagram of a high-integration lithium niobate/silicon nitride optical waveguide integrated structure;
FIG. 2 is a schematic structural diagram of a lithium niobate/optical waveguide integrated structure including a first silicon oxide layer;
FIG. 3 is a schematic diagram of a silicon nitride waveguide fabricated on a fourth silicon oxide layer;
FIG. 4 is a schematic structural view after a second silicon oxide layer and a third silicon oxide layer are formed on the silicon nitride waveguide layer;
FIG. 5 is a schematic view of a silicon substrate bonded to a polished surface of a second silicon dioxide layer;
FIG. 6 is a schematic view of the structure without the first silicon oxide layer after the first sacrificial silicon substrate is removed;
FIG. 7 is a schematic view of a structure bonded to a polished surface of a second silicon oxide layer when the first silicon oxide layer is included on a silicon substrate;
FIG. 8 is a schematic view of the structure after the first sacrificial silicon substrate is removed when the first silicon oxide layer is included;
fig. 9 is a schematic flow chart of a method for manufacturing a high-integration lithium niobate/silicon nitride optical waveguide integrated structure.
Reference numerals: the silicon nitride waveguide structure comprises a silicon substrate 1, a second silicon dioxide layer 2, a third silicon oxide layer 3, a fourth silicon oxide layer 4, a lithium niobate thin film layer 5, a silicon nitride waveguide 6, a first silicon oxide layer 7 and a first sacrificial silicon substrate 9.
Detailed Description
The invention aims to provide a high-integration lithium niobate/silicon nitride optical waveguide integrated structure and a preparation method thereof, and the high-integration lithium niobate/silicon nitride optical waveguide integrated structure is realized by the following technical scheme:
a high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a third silicon dioxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top as shown in figure 1, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 10-100 nm.
The preferable high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a first silicon oxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top as shown in fig. 2, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 10-100 nm.
The invention also includes a method for preparing the high-integration lithium niobate/silicon nitride optical waveguide integrated structure, as shown in the flow chart of fig. 9, which comprises the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the fourth silicon oxide layer is prepared by a thermal oxidation method or a deposition method, the thickness of the fourth silicon oxide layer is 10-100 nm, and the step of preparing the fourth silicon oxide layer on the first sacrificial silicon substrate by the thermal oxidation method comprises the steps of putting the first sacrificial silicon substrate into an oxidation furnace, introducing oxygen for oxidation, wherein the oxidation temperature is 900-1100 ℃, and the oxidation time is adjusted within 0.1-10 hours according to the thickness of the first silicon oxide layer.
② depositing a silicon nitride film on the fourth silicon oxide layer by deposition and forming a silicon nitride waveguide layer by photolithography, as shown in FIG. 3;
③ depositing silicon oxide on the silicon nitride waveguide layer by a deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the thickness of the third silicon oxide layer is the same as that of the silicon nitride waveguide layer, as shown in FIG. 4;
④ bonding the surface-polished silicon substrate to the polished surface of the second silicon oxide layer, as shown in FIG. 5;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate using a wet etch process, leaving the fourth silicon oxide layer, as shown in FIG. 6;
⑥ bonding a lithium niobate thin film layer with a target thickness on the surface of the fourth silicon oxide layer to obtain a high-integration lithium niobate/silicon nitride optical waveguide integrated structure, as shown in FIG. 1.
The preferred preparation method comprises the steps of ④, depositing a first silicon oxide layer on the surface of a silicon substrate, polishing the first silicon oxide layer, bonding the first silicon oxide layer with the polished surface of a second silicon oxide layer, as shown in fig. 7, then performing ⑤, covering the silicon substrate with a protective film, etching away the first sacrificial silicon substrate by using a wet etching process, leaving the fourth silicon oxide layer, as shown in fig. 8, and then performing ⑥, bonding a lithium niobate thin film layer with a target thickness on the surface of the fourth silicon oxide layer, thereby obtaining the high-integration lithium niobate/silicon nitride optical waveguide integrated structure, as shown in fig. 2.
The method for removing the sacrificial silicon substrate and the sacrificial silicon oxide layer is the conventional method adopting corrosion solution immersion corrosion, wherein TMAH aqueous solution with the mass fraction of 10-25%, KOH aqueous solution with the mass fraction of 10-30%, NaOH aqueous solution with the mass fraction of 10-30% or HF, HNO can be adopted for removing the sacrificial silicon substrate (comprising the first sacrificial silicon substrate and the second sacrificial silicon substrate)3And CH3Mixed solution of COOH, HF and HNO3The volume ratio is 1: 3 to 6, CH3COOH volumes HF and HNO350% -150% of the total volume; the etching solution used for removing the sacrificial silicon oxide layer is 35-40% of HF aqueous solution in mass fraction.
The thickness of the sacrificial silicon substrate is generally between 0.2 and 1mm, and the thickness of the sacrificial silicon oxide layer is generally between 1 and 5 μm.
The method comprises the specific steps of adopting an intelligent stripping method to bond a lithium niobate thin film with a target thickness, namely adopting an ion implantation method to implant ions into the lithium niobate crystal, so that the lithium niobate crystal is divided into a thin film layer, a separation layer and a residual layer from top to bottom, then adopting a wafer bonding method to bond the lithium niobate thin film layer and a fourth silicon oxide layer, heating to separate the separation layer and the residual layer of the lithium niobate, and finally polishing the lithium niobate thin film layer, namely bonding the lithium niobate thin film layer on the surface of the fourth silicon oxide layerA lithium niobate thin film layer of a target thickness; wherein the implantation ions are H ions or He ions, and the implantation dosage is 3 × 10 when implanting H ions16ions/cm2～8×1016ions/cm2The injection energy is 120 KeV-400 KeV; when implanting ion He ion, the implantation dose is 3X 1016ions/cm2～9×1016ions/cm2The implantation energy is 90 KeV-400 KeV.
The invention is further described with reference to specific examples.
Example 1
A high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a third silicon dioxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top as shown in figure 1, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 10 nm;
the thickness of the fourth silicon oxide layer can be adjusted between 10nm and 100nm according to actual needs, and selectable data can be 15nm, 20nm, 18nm, 30nm, 35nm, 40nm, 48nm, 50nm, 54nm, 60nm, 62nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 98nm, 100nm and the like;
the thickness of the fourth silicon oxide layer is preferably 10-40 nm, optional data such as 12nm, 15nm, 20nm, 25nm, 30nm, 32nm, 38nm, 40nm and the like can be selected, and the thinner and more uniform the thickness of the layer, the better the optical signal coupling is, and the better the uniformity of the device is.
Example 2
A high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a third silicon dioxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 10 nm;
wherein the thickness of the silicon substrate layer is 0.2mm, the thickness of the second silicon dioxide layer is 1 μm, the thickness of the third silicon oxide layer is 100nm, and the thickness of the lithium niobate thin film layer is 50 nm.
Example 3
A high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a third silicon dioxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 100 nm;
the thickness of the silicon substrate layer is 1mm, the thickness of the second silicon dioxide layer is 5 microns, the thickness of the third silicon oxide layer is 1000nm, and the thickness of the lithium niobate thin film layer is 1000 nm.
Example 4
A high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a third silicon dioxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 40 nm;
the thickness of the silicon substrate layer is 0.4mm, the thickness of the second silicon dioxide layer is 2 μm, the thickness of the third silicon oxide layer is 250nm, and the thickness of the lithium niobate thin film layer is 300 nm.
Example 5
A high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a third silicon dioxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 70 nm;
the thickness of the silicon substrate layer is 0.8mm, the thickness of the second silicon dioxide layer is 4 μm, the thickness of the third silicon oxide layer is 700nm, and the thickness of the lithium niobate thin film layer is 800 nm.
Example 6
A high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a first silicon oxide layer, a second silicon oxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 10 nm;
the thickness of the fourth silicon oxide layer can be adjusted between 10nm and 100nm according to actual needs, and selectable data can be 15nm, 20nm, 18nm, 30nm, 35nm, 40nm, 48nm, 50nm, 54nm, 60nm, 62nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 98nm, 100nm and the like;
the thickness of the fourth silicon oxide layer is preferably 10-40 nm, optional data such as 12nm, 15nm, 20nm, 25nm, 30nm, 32nm, 38nm, 40nm and the like can be selected, and the thinner and more uniform the thickness of the layer, the better the optical signal coupling is, and the better the uniformity of the device is.
Example 7
A high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a first silicon oxide layer, a second silicon oxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 10 nm;
the thickness of the first silicon oxide layer is 0.5 μm, and the thickness of the second silicon oxide layer is 0.5 μm; the thickness of the silicon substrate layer is 0.2mm, the thickness of the third silicon oxide layer is 100nm, and the thickness of the lithium niobate thin film layer is 1000 nm.
Example 8
A high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a first silicon oxide layer, a second silicon oxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 100 nm;
the thickness of the first silicon oxide layer is 2 μm, and the thickness of the second silicon oxide layer is 3 μm; the thickness of the silicon substrate layer is 1mm, the thickness of the third silicon oxide layer is 1000nm, and the thickness of the lithium niobate thin film layer is 50 nm.
Example 9
A high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a first silicon oxide layer, a second silicon oxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 35 nm;
the thickness of the first silicon oxide layer is 1 μm, and the thickness of the second silicon oxide layer is 2 μm; the thickness of the silicon substrate layer is 0.5mm, the thickness of the third silicon oxide layer is 300nm, and the thickness of the lithium niobate thin film layer is 400 nm.
Example 10
A high-integration-level lithium niobate/silicon nitride optical waveguide integrated structure comprises a silicon substrate layer, a first silicon oxide layer, a second silicon oxide layer, a third silicon oxide layer, a fourth silicon oxide layer and a lithium niobate thin film layer from bottom to top, wherein the middle of the third silicon oxide layer comprises an etched silicon nitride waveguide layer, the thickness of the silicon nitride waveguide layer is consistent with that of the third silicon oxide layer, and the thickness of the fourth silicon oxide layer is 85 nm;
the thickness of the first silicon oxide layer is 3 mu m; the thickness of the second silicon dioxide layer is 1 μm, the thickness of the silicon substrate layer is 0.8mm, the thickness of the third silicon oxide layer is 600nm, and the thickness of the lithium niobate thin film layer is 550 nm.
Example 11
The preparation method of the high-integration lithium niobate/silicon nitride optical waveguide integrated structure in embodiment 1 includes the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the thickness of the fourth silicon oxide layer is 10 nm;
② depositing a silicon nitride film on the fourth silicon oxide layer by deposition method, and preparing a silicon nitride waveguide layer by photolithography method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the thickness of the third silicon oxide layer is the same as that of the silicon nitride waveguide layer;
④ bonding the surface-polished silicon substrate to the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with a target thickness on the surface of the fourth silicon oxide layer to obtain the high-integration lithium niobate/silicon nitride optical waveguide integrated structure.
In the other optical waveguide integrated structure according to embodiment 1, the thickness parameter of the prepared fourth silicon oxide layer may be adjusted according to the thickness of the fourth silicon oxide layer, so as to obtain a corresponding high-integration lithium niobate/silicon nitride optical waveguide integrated structure.
Example 12
The preparation method of the high-integration lithium niobate/silicon nitride optical waveguide integrated structure described in embodiment 2 includes the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the thickness of the fourth silicon oxide layer is 10 nm;
② depositing a silicon nitride film with a thickness of 100nm on the fourth silicon oxide layer by a deposition method, and preparing a silicon nitride waveguide layer by a photoetching method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the thickness of the third silicon oxide layer is 100nm and the thickness of the second silicon oxide layer is 1 μm;
④ bonding the surface-polished silicon substrate to the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with a thickness of 50nm on the surface of a fourth silicon oxide layer to obtain a high-integration lithium niobate/silicon nitride optical waveguide integrated structure, wherein the method for bonding the lithium niobate thin film with a target thickness is an intelligent stripping method, and comprises the specific steps of implanting ions into the lithium niobate crystal by an ion implantation method to divide the lithium niobate crystal into a thin film layer, a separation layer and a residual layer from top to bottom, bonding the lithium niobate thin film layer and the fourth silicon oxide layer by a wafer bonding method, heating to separate the separation layer and the residual layer of the lithium niobate, and polishing the lithium niobate thin film layer to bond the lithium niobate thin film layer with the target thickness on the surface of the fourth silicon oxide layer, wherein the implanted ions are He ions, and implanting and measuring 3 × 1016ions/cm2The implantation energy is 90 KeV.
Example 13
The method for preparing a high-integration lithium niobate/silicon nitride optical waveguide integrated structure according to embodiment 3 includes the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the thickness of the fourth silicon oxide layer is 100 nm;
② depositing a silicon nitride film with a thickness of 1000nm on the fourth silicon oxide layer by deposition method, and preparing a silicon nitride waveguide layer by photolithography method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the thickness of the third silicon oxide layer is 1000nm and the thickness of the second silicon oxide layer is 5 μm;
④ bonding the surface-polished silicon substrate to the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with the thickness of 1000nm on the surface of the fourth silicon oxide layer to obtain the high-integration lithium niobate/silicon nitride optical waveguide integrated structure, wherein the step of bonding the lithium niobate thin film with the target thickness is bonding the LNOISI lithium niobate thin film with the polished upper surface with the surface of the fourth silicon oxide layer, wherein the lower surface of the LNOISI lithium niobate thin film is sequentially provided with a first sacrificial silicon oxide layer and a second sacrificial silicon substrate layer, and then removing the first sacrificial silicon oxide layer and the second sacrificial silicon substrate layer by adopting a grinding process and a wet etching process.
Example 14
The preparation method of the high-integration lithium niobate/silicon nitride optical waveguide integrated structure described in embodiment 4 includes the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the thickness of the fourth silicon oxide layer is 40 nm;
② depositing a silicon nitride film with a thickness of 250nm on the fourth silicon oxide layer by a deposition method, and preparing a silicon nitride waveguide layer by a photoetching method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the thickness of the third silicon oxide layer is 250nm and the thickness of the second silicon oxide layer is 2 μm;
④ bonding the surface-polished silicon substrate to the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with thickness of 300nm on the surface of the fourth silicon oxide layer to obtain a high-integration lithium niobate/silicon nitride optical waveguide integrated structure, wherein the step of bonding the lithium niobate thin film with target thickness comprises bonding the LNOI lithium niobate thin film with polished upper surface with the surface of the fourth silicon oxide layer, wherein the lower surface of the LNOI lithium niobate thin film is a second sacrificial silicon oxide layer and a sacrificial lithium niobate substrate layer, and then removing the second sacrificial silicon oxide layer and the sacrificial lithium niobate substrate layer by grinding process and wet etching process.
Example 15
The preparation method of the high-integration lithium niobate/silicon nitride optical waveguide integrated structure described in embodiment 5 includes the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the thickness of the fourth silicon oxide layer is 70 nm;
② depositing a silicon nitride film with a thickness of 700nm on the fourth silicon oxide layer by a deposition method, and preparing a silicon nitride waveguide layer by a photoetching method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the thickness of the third silicon oxide layer is 700nm and the thickness of the second silicon oxide layer is 4 μm;
④ bonding the surface-polished silicon substrate to the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with the thickness of 800nm on the surface of the fourth silicon oxide layer to obtain the high-integration lithium niobate/silicon nitride optical waveguide integrated structure, wherein the step of bonding the lithium niobate thin film with the target thickness is bonding the LNOISI lithium niobate thin film with the polished upper surface with the surface of the fourth silicon oxide layer, wherein the lower surface of the LNOISI lithium niobate thin film is sequentially provided with a first sacrificial silicon oxide layer and a second sacrificial silicon substrate layer, and then removing the first sacrificial silicon oxide layer and the second sacrificial silicon substrate layer by adopting a grinding process and a wet etching process.
Example 16
The method for preparing a high-integration lithium niobate/silicon nitride optical waveguide integrated structure according to embodiment 6 includes the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the thickness of the fourth silicon oxide layer is 10 nm;
② depositing a silicon nitride film on the fourth silicon oxide layer by deposition method, and preparing a silicon nitride waveguide layer by photolithography method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the thickness of the third silicon oxide layer is the same as that of the silicon nitride waveguide layer;
④ depositing a first silicon oxide layer on the surface of the silicon substrate, polishing the first silicon oxide layer, and bonding with the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with a target thickness on the surface of the fourth silicon oxide layer to obtain the high-integration lithium niobate/silicon nitride optical waveguide integrated structure.
In another optical waveguide integrated structure according to embodiment 6, the thickness parameter of the prepared fourth silicon oxide layer may be adjusted to obtain a corresponding high-integration lithium niobate/silicon nitride optical waveguide integrated structure.
Example 17
The method for preparing a high-integration lithium niobate/silicon nitride optical waveguide integrated structure according to embodiment 7 includes the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the thickness of the fourth silicon oxide layer is 10 nm;
② depositing a silicon nitride film with a thickness of 100nm on the fourth silicon oxide layer by a deposition method, and preparing a silicon nitride waveguide layer by a photoetching method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the third silicon oxide layer has a thickness of 100nm, the first silicon oxide layer has a thickness of 0.5 μm, and the second silicon oxide layer has a thickness of 0.5 μm;
④ depositing a first silicon oxide layer on the surface of the silicon substrate, polishing the first silicon oxide layer, and bonding with the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with a thickness of 1000nm on the surface of a fourth silicon oxide layer to obtain a high-integration lithium niobate/silicon nitride optical waveguide integrated structure, wherein the method for bonding the lithium niobate thin film with a target thickness is an intelligent stripping method, and the method comprises the specific steps of adopting an ion implantation method to implant ions into the lithium niobate crystal, enabling the lithium niobate crystal to be divided into a thin film layer, a separation layer and a residual layer from top to bottom, then adopting a wafer bonding method to bond the lithium niobate thin film layer and the fourth silicon oxide layer, heating to separate the separation layer and the residual layer of the lithium niobate, and finally polishing the lithium niobate thin film layer, namely bonding the lithium niobate thin film layer with the target thickness on the surface of the fourth silicon oxide layer, implanting ions H, and implanting and measuring 8 to 10 ions16ions/cm2And the implantation energy is 200 KeV.
Example 18
The method for preparing a high-integration lithium niobate/silicon nitride optical waveguide integrated structure according to embodiment 8 includes the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the thickness of the fourth silicon oxide layer is 100 nm;
② depositing a silicon nitride film with a thickness of 1000nm on the fourth silicon oxide layer by deposition method, and preparing a silicon nitride waveguide layer by photolithography method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the third silicon oxide layer has a thickness of 1000nm, the first silicon oxide layer has a thickness of 2 μm, and the second silicon oxide layer has a thickness of 3 μm;
④ depositing a first silicon oxide layer on the surface of the silicon substrate, polishing the first silicon oxide layer, and bonding with the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with the thickness of 50nm on the surface of the fourth silicon oxide layer to obtain the high-integration lithium niobate/silicon nitride optical waveguide integrated structure, wherein the step of bonding the lithium niobate thin film with the target thickness is bonding the LNOISI lithium niobate thin film with the polished upper surface with the surface of the fourth silicon oxide layer, wherein the lower surface of the LNOISI lithium niobate thin film is sequentially provided with a first sacrificial silicon oxide layer and a second sacrificial silicon substrate layer, and then removing the first sacrificial silicon oxide layer and the second sacrificial silicon substrate layer by adopting a grinding process and a wet etching process.
Example 19
The method for preparing a high-integration lithium niobate/silicon nitride optical waveguide integrated structure according to embodiment 9 includes the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the thickness of the fourth silicon oxide layer is 35 nm;
② depositing a silicon nitride film with a thickness of 300nm on the fourth silicon oxide layer by a deposition method, and preparing a silicon nitride waveguide layer by a photoetching method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the third silicon oxide layer has a thickness of 300nm, the first silicon oxide layer has a thickness of 1 μm, and the second silicon oxide layer has a thickness of 2 μm;
④ depositing a first silicon oxide layer on the surface of the silicon substrate, polishing the first silicon oxide layer, and bonding with the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with thickness of 400nm on the surface of the fourth silicon oxide layer to obtain a high-integration lithium niobate/silicon nitride optical waveguide integrated structure, wherein the step of bonding the lithium niobate thin film with target thickness is bonding the LNOI lithium niobate thin film with polished upper surface with the surface of the fourth silicon oxide layer, wherein the lower surface of the LNOI lithium niobate thin film is a second sacrificial silicon oxide layer and a sacrificial lithium niobate substrate layer, and then removing the second sacrificial silicon oxide layer and the sacrificial lithium niobate substrate layer by adopting a grinding process and a wet etching process.
Example 20
The method for preparing a high-integration lithium niobate/silicon nitride optical waveguide integrated structure according to embodiment 10 includes the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the thickness of the fourth silicon oxide layer is 35 nm;
② depositing a silicon nitride film with a thickness of 300nm on the fourth silicon oxide layer by a deposition method, and preparing a silicon nitride waveguide layer by a photoetching method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the third silicon oxide layer has a thickness of 300nm, the first silicon oxide layer has a thickness of 1 μm, and the second silicon oxide layer has a thickness of 2 μm;
④ depositing a first silicon oxide layer on the surface of the silicon substrate, polishing the first silicon oxide layer, and bonding with the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with thickness of 400nm on the surface of the fourth silicon oxide layer to obtain a high-integration lithium niobate/silicon nitride optical waveguide integrated structure, wherein the step of bonding the lithium niobate thin film with target thickness comprises bonding an LNOI lithium niobate thin film with polished upper surface with the surface of the fourth silicon oxide layer, wherein the lower surface of the LNOI lithium niobate thin film is a second sacrificial silicon oxide layer and a sacrificial lithium niobate substrate layer, and then removing the second sacrificial silicon oxide layer and the sacrificial lithium niobate substrate layer by adopting a grinding process and a wet etching process.

Claims (10)

1. A high-integration lithium niobate/silicon nitride optical waveguide integrated structure is characterized in that: from the bottom up includes silicon substrate layer, third silicon dioxide layer, third silicon oxide layer, fourth silicon oxide layer and lithium niobate thin film layer, wherein includes the silicon nitride waveguide layer by the sculpture in the middle of the third silicon oxide layer to the thickness of silicon nitride waveguide layer is unanimous with third silicon oxide layer thickness, and the thickness of fourth silicon oxide layer is 10 ~ 100 nm.
2. The integrated structure of the high-integration lithium niobate/silicon nitride optical waveguide of claim 1, wherein: the thickness of the fourth silicon oxide layer is 10-40 nm.
3. The integrated structure of the high-integration lithium niobate/silicon nitride optical waveguide of claim 1, wherein: the silicon substrate layer and the second silicon dioxide layer also comprise a first silicon oxide layer.
4. The integrated structure of the high-integration lithium niobate/silicon nitride optical waveguide of claim 1, wherein: the thickness of the silicon substrate layer is 0.2-1 mm, the thickness of the second silicon dioxide layer is 1-5 μm, the thickness of the third silicon oxide layer is 100-1000 nm, and the thickness of the lithium niobate thin film layer is 50-1000 nm.
5. The integrated structure of the high-integration lithium niobate/silicon nitride optical waveguide of claim 2, wherein: the total thickness of the first silicon oxide layer and the second silicon oxide layer is 1-5 mu m; the thickness of the silicon substrate layer is 0.2-1 mm, the thickness of the third silicon oxide layer is 100-1000 nm, and the thickness of the lithium niobate thin film layer is 50-1000 nm.
6. A preparation method of a high-integration lithium niobate/silicon nitride optical waveguide integrated structure is characterized by comprising the following steps: the method comprises the following steps:
① preparing a first sacrificial silicon substrate with a fourth silicon oxide layer on the surface, wherein the fourth silicon oxide layer is prepared by a thermal oxidation method or a deposition method, and the thickness of the fourth silicon oxide layer is 10-100 nm;
② depositing a silicon nitride film on the fourth silicon oxide layer by deposition method, and preparing a silicon nitride waveguide layer by photolithography method;
③ depositing silicon oxide on the silicon nitride waveguide layer by deposition method to cover the silicon nitride waveguide layer, polishing to a target thickness, preparing a second silicon oxide layer and a third silicon oxide layer at one time, and polishing the surface of the second silicon oxide layer, wherein the thickness of the third silicon oxide layer is the same as that of the silicon nitride waveguide layer;
④ bonding the surface-polished silicon substrate to the polished surface of the second silicon oxide layer;
⑤ covering the silicon substrate with a protective film, and etching away the first sacrificial silicon substrate by wet etching process to leave the fourth silicon oxide layer;
⑥ bonding a lithium niobate thin film layer with a target thickness on the surface of the fourth silicon oxide layer to obtain the high-integration lithium niobate/silicon nitride optical waveguide integrated structure.
7. The method according to claim 6, wherein step ④ comprises depositing a first silicon oxide layer on the surface of the silicon substrate, polishing the first silicon oxide layer, and bonding the first silicon oxide layer to the polished surface of the second silicon oxide layer.
8. The method for preparing a highly integrated lithium niobate/silicon nitride optical waveguide integrated structure according to any one of claims 6 or 7, wherein the method for bonding a lithium niobate thin film of a target thickness in step ⑥ is an intelligent lift-off method, and comprises the steps of implanting ions into the lithium niobate crystal by ion implantation, dividing the lithium niobate crystal into a thin film layer, a separation layer and a residual layer from top to bottom, bonding the lithium niobate thin film layer and a fourth silicon oxide layer by wafer bonding, heating to separate the separation layer and the residual layer of the lithium niobate, and polishing the lithium niobate thin film layer, thereby bonding the lithium niobate thin film layer of the target thickness on the surface of the fourth silicon oxide layer.
9. The method for preparing a highly integrated lithium niobate/silicon nitride optical waveguide integrated structure according to any one of claims 6 or 7, wherein the step of bonding the lithium niobate thin film of the target thickness in step ⑥ is bonding an LNOISI lithium niobate thin film with a polished upper surface to a fourth silicon oxide layer, wherein the lower surface of the LNOISI lithium niobate thin film is a first sacrificial silicon oxide layer and a second sacrificial silicon substrate layer in sequence, and then removing the first sacrificial silicon oxide layer and the second sacrificial silicon substrate layer by a grinding process and a wet etching process.
10. The method for preparing a highly integrated lithium niobate/silicon nitride optical waveguide integrated structure as claimed in any one of claims 6 or 7, wherein the step of bonding the lithium niobate thin film of the target thickness in step ⑥ is bonding the LNOI lithium niobate thin film with a polished upper surface to a fourth silicon oxide layer, wherein the lower surface of the LNOI lithium niobate thin film is the second sacrificial silicon oxide layer and the sacrificial lithium niobate substrate layer, and then removing the second sacrificial silicon oxide layer and the sacrificial lithium niobate substrate layer by using a grinding process and a wet etching process.
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