CN111983825A

CN111983825A - Electro-optic crystal film and preparation method thereof

Info

Publication number: CN111983825A
Application number: CN202010889148.0A
Authority: CN
Inventors: 张秀全; 刘桂银; 王金翠; 李真宇; 杨超; 连坤; 孔霞
Original assignee: Jinan Jingzheng Electronics Co Ltd
Current assignee: Jinan Jingzheng Electronics Co Ltd
Priority date: 2020-08-28
Filing date: 2020-08-28
Publication date: 2020-11-24
Anticipated expiration: 2040-08-28
Also published as: CN111983825B

Abstract

The application provides an electro-optic crystal film and a preparation method thereof, comprising the following steps: the substrate layer, the isolation layer, the compensation layer and the functional thin film layer are sequentially stacked; the refractive index of the functional thin film layer is larger than that of the compensation layer, wherein the compensation layer is made of doped inorganic materials, the doped inorganic materials are light-weight ions doped in the inorganic materials, and the light-weight ions are ions with relative atomic mass smaller than that of any element in the inorganic materials. The functional thin film layer is a doped electro-optic crystal material, the doped electro-optic crystal material is formed by doping heavy ions in the electro-optic crystal material, and the heavy ions are ions with relative atomic mass larger than that of any element in the electro-optic crystal material. By doping light-weight ions in the compensation layer and doping heavy-weight ions in the functional thin film layer, the electro-optic crystal thin film with larger refractive index difference is provided, so that the refractive index difference is not limited by the constraint of the refractive index of the material.

Description

Electro-optic crystal film and preparation method thereof

Technical Field

The application belongs to the field of semiconductor element preparation, and particularly relates to an electro-optic crystal film and a preparation method thereof.

Background

The electro-optical crystal (such as lithium niobate, lithium tantalate crystal, etc.) has excellent nonlinear optical characteristics, electro-optical characteristics, and acousto-optical characteristics, and thus has wide application in optical signal processing, information storage, etc. The application of the electro-optical crystal in the electro-optical modulator mainly utilizes the refractive index difference between the electro-optical crystal and the oxide isolation layer to limit light in the electro-optical crystal.

An electro-optic crystal thin film disclosed in the prior art includes a silicon substrate, an oxide isolation layer, and a lithium niobate piezoelectric thin film stacked in this order, and in the electro-optic crystal thin film, light is confined in lithium niobate by using a refractive index difference between the lithium niobate and the oxide isolation layer. Among them, the larger the refractive index difference is, the better the effect of light confinement in the lithium niobate layer is.

However, in the prior art, the refractive index difference is limited by the refractive indexes of the electro-optical crystal and the oxide isolation layer, for example, in order to achieve a better light confinement effect, the oxide isolation layer is generally made of a silicon dioxide material with a relatively small refractive index, and in order to obtain a better light confinement effect, two materials with a larger refractive index difference need to be excavated, which is a long and difficult problem, and the electro-optical crystal thin film with a larger refractive index difference cannot be provided at present.

Disclosure of Invention

The electro-optic crystal film with the larger refractive index difference is provided in order to solve the technical problem that the electro-optic crystal film with the larger refractive index difference cannot be provided in the prior art.

In a first aspect, the present application provides an electro-optic crystal film comprising: the substrate layer, the compensation layer and the functional film layer are sequentially stacked; the refractive index of the functional thin film layer is larger than that of the compensation layer, wherein the compensation layer is made of a doped inorganic material, the doped inorganic material is formed by doping light-weight ions in the inorganic material, and the light-weight ions are ions with relative atomic mass smaller than that of any element in the inorganic material.

Further, the functional thin film layer is a doped electro-optic crystal material, the doped electro-optic crystal material is formed by doping heavy ions in the electro-optic crystal material, and the heavy ions are ions with relative atomic mass larger than that of any element in the electro-optic crystal material.

Further, the heavy mass ions include rare earth ions having a photoluminescence effect.

Further, the rare earth ions having a photoluminescence effect include erbium ions, thulium ions, ytterbium ions, or lutetium ions.

Further, the heavy mass ions include germanium ions, copper ions, iron ions, or manganese ions.

Further, the light mass ions include lithium ions, boron ions, fluorine ions, or phosphorus ions.

Further, an isolation layer is also laminated between the substrate layer and the compensation layer.

Further, the isolation layer is made of silicon dioxide or silicon nitride materials, the electro-optic crystal material is made of lithium niobate crystal materials, lithium tantalate crystal materials, potassium titanyl phosphate crystal materials or rubidium titanyl phosphate crystal materials, and the inorganic material is made of silicon dioxide or silicon nitride.

Further, the isolation layer and the inorganic material are made of the same material.

In a second aspect, the present application provides an electro-optic modulator comprising the electro-optic crystal film of the first aspect.

In a third aspect, the present application provides a further electro-optic crystal film comprising: the photoelectric composite film comprises a substrate layer, an isolation layer and a functional thin film layer which are sequentially stacked, wherein the refractive index of the functional thin film layer is larger than that of the isolation layer, the functional thin film layer is a doped photoelectric crystal material, the doped photoelectric crystal material is formed by doping heavy ions in the photoelectric crystal material, and the heavy ions are ions with relative atomic mass larger than that of any element in the photoelectric crystal material.

Further, the isolation layer is made of silicon dioxide or silicon nitride materials, and the electro-optic crystal material is made of lithium niobate crystal materials, lithium tantalate crystal materials, potassium titanyl phosphate crystal materials or rubidium titanyl phosphate crystal materials.

In a fourth aspect, the present application provides a further electro-optic modulator comprising the electro-optic crystal film of the third aspect.

In a fifth aspect, the present application provides a method for preparing an electro-optic crystal film, the method comprising:

preparing a compensation layer on a substrate layer, wherein the compensation layer is a doped inorganic material, the doped inorganic material is formed by doping light-weight ions in the inorganic material, and the light-weight ions are ions with relative atomic mass smaller than that of any element in the inorganic material;

and preparing a functional thin film layer on the compensation layer, wherein the refractive index of the functional thin film layer is greater than that of the compensation layer.

Further, the method further comprises:

doping heavy mass ions in a film matrix, wherein the film matrix is an electro-optic crystal material, and the heavy mass ions refer to ions with relative atomic mass larger than that of any element in the electro-optic crystal material;

and preparing a functional thin film layer on the compensation layer by using the doped thin film substrate, wherein heavy ions are doped in the functional thin film layer.

Further, the method further comprises: preparing an isolation layer in advance between the substrate layer and the compensation layer, wherein the isolation layer is laminated between the substrate layer and the compensation layer.

Further, a functional thin film layer is formed on the compensation layer by an ion implantation method and a bonding separation method, or by a bonding method and a lapping polishing method.

In a sixth aspect, the present application provides a method for preparing a further electro-optic crystal film, the method comprising:

preparing a first compensation layer on a substrate layer, wherein the first compensation layer is a doped inorganic material, the doped inorganic material is formed by doping light-weight ions in the inorganic material, and the light-weight ions are ions with relative atomic mass smaller than that of any element in the inorganic material;

preparing a second compensation layer on a film substrate, wherein the film substrate is made of an electro-optic crystal material, and the second compensation layer is made of the same material as the first compensation layer;

bonding the first compensation layer and the second compensation layer to obtain a bonded body;

and grinding and polishing the film substrate on the bonding body to a preset thickness to obtain a functional film layer, wherein the refractive index of the functional film layer is greater than that of the first compensation layer.

Further, before the preparing the second compensation layer on the film substrate, the method further comprises:

and doping heavy mass ions in the thin film matrix, wherein the heavy mass ions refer to ions with relative atomic mass larger than that of any element in the electro-optical crystal material.

Further, after obtaining the bonding body, the method further includes:

and carrying out heat treatment on the bonding body, wherein the film substrate on the bonding body is placed in a diffusion device filled with heavy mass ion diffusion agent, and the film substrate on the bonding body is subjected to heat treatment under the condition of preset heat preservation temperature.

Further, the method further comprises: preparing an isolation layer in advance between the substrate layer and the first compensation layer, wherein the isolation layer is laminated between the substrate layer and the first compensation layer.

In a seventh aspect, the present application provides a method for preparing an electro-optic crystal film, the method comprising:

carrying out ion implantation on a film substrate, wherein the film substrate is an electro-optic crystal material;

preparing a second compensation layer on the ion implantation surface of the film substrate, wherein the second compensation layer is the same as the first compensation layer in material;

and carrying out heat treatment on the bonding body to obtain a functional thin film layer, wherein the refractive index of the functional thin film layer is greater than that of the first compensation layer.

Further, before the ion implantation is performed on the film substrate, the method further comprises the following steps:

Further, after obtaining the bonding body, the method further includes:

In an eighth aspect, the present application provides a method for preparing an electro-optic crystal film, the method comprising:

preparing an isolation layer with a target thickness on the substrate layer;

preparing a functional thin film layer on the isolation layer, wherein the refractive index of the functional thin film layer is greater than that of the isolation layer, the functional thin film layer is a doped electro-optic crystal material, the doped electro-optic crystal material is formed by doping heavy ions in the electro-optic crystal material, and the heavy ions are ions with relative atomic mass greater than that of any element in the electro-optic crystal material.

According to the electro-optic crystal film and the preparation method thereof, the electro-optic crystal film with larger refractive index difference is provided in a mode that light ions are doped in the compensation layer, or heavy ions are doped in the functional thin film layer, or the light ions are doped in the compensation layer, and the heavy ions are doped in the functional thin film layer. The scheme provided by the application can also adjust the refractive index difference between the functional thin film layer and the compensation layer or between the functional thin film layer and the isolation layer by adjusting the doping concentration, so that the refractive index difference is not limited by the constraint of the refractive index of the material.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

FIG. 1 is a schematic structural diagram of an electro-optic crystal film according to an embodiment of the present disclosure;

FIG. 2 is a schematic structural diagram of another electro-optic crystal film according to an embodiment of the present disclosure;

FIG. 3 is a schematic structural diagram of an electro-optic crystal film according to a second embodiment of the present disclosure;

fig. 4 is a schematic structural diagram of an electro-optic crystal film according to a third embodiment of the present application;

FIG. 5 is a schematic view of a working flow of a method for manufacturing an electro-optic crystal thin film according to a fifth embodiment of the present disclosure;

FIG. 6 is a schematic view of a work flow of a method for manufacturing an electro-optic crystal thin film according to a seventh embodiment of the present disclosure;

fig. 7 is a schematic workflow diagram of a method for manufacturing an electro-optic crystal thin film according to a tenth embodiment of the present application.

Description of the reference numerals

110-substrate layer, 120-isolation layer, 130-compensation layer, 140-functional thin film layer, 140A-thin film base body, 130A-first compensation layer and 130B-second compensation layer.

Detailed Description

In order to make the technical solutions of the present invention better understood, 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 only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", "left" and "right" and the like indicate orientations or positional relationships based on operational states of the present application, and are only used for convenience of description and simplification of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation and be operated, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

Example one

As shown in fig. 1, an embodiment of the present application provides an electro-optic crystal film, including: a substrate layer 110, a compensation layer 130 and a functional thin film layer 140 stacked in sequence; the refractive index of the functional thin film layer 140 is greater than that of the compensation layer 130, wherein the compensation layer 130 is a doped inorganic material, the doped inorganic material is formed by doping light-weight ions in the inorganic material, and the light-weight ions are ions with relative atomic mass less than that of any element in the inorganic material.

In the embodiment of the present application, an inorganic material layer is disposed between the substrate layer 110 and the functional thin film layer 140, and light ions are doped into the inorganic material to obtain the compensation layer 130, where the light ions refer to ions having a relative atomic mass smaller than that of any element in the inorganic material, so that the refractive index of the compensation layer 130 obtained after doping is smaller than that of the inorganic material before doping. Therefore, in the first embodiment of the present application, the refractive index difference between the functional thin film layer 140 and the compensation layer 130 is increased by doping light-mass ions in the inorganic material to reduce the refractive index of the inorganic material, and further, the refractive index difference between the functional thin film layer 140 and the compensation layer 130 can be adjusted by controlling the doping concentration, so that the refractive index difference between the functional thin film layer 140 and the compensation layer 130 is not constrained by the refractive index of the material.

In the embodiment of the present application, the inorganic material in the compensation layer 130 may be silicon dioxide, silicon nitride, or the like, which is not limited in the present application. In the embodiment of the present application, the doped light ions are not limited, as long as the refractive index of the compensation layer 130 obtained after doping is lower than that of the inorganic material before doping. In addition, the light-weight ions described in the examples of the present application mean ions having a relative atomic mass at least smaller than that of one of the elements in the inorganic material. For example, if the inorganic material in the compensation layer 130 is silicon dioxide, the relative atomic mass of the doped lightweight ions can be less than all of the ions of silicon or oxygen, and in one specific example, the doped lightweight ions are lithium ions, boron ions, fluorine ions, phosphorus ions, and the like.

Further, as shown in fig. 2, an isolation layer 120 may be further disposed between the substrate layer 110 and the compensation layer 130, and the refractive index of the isolation layer 120 is smaller than that of the functional thin film layer 140. The isolation layer 120 serves to prevent an optical signal of the functional thin film layer 140 from leaking into the substrate layer 110, wherein the isolation layer 120 may be made of silicon dioxide or silicon nitride, which is not limited in this application.

In one embodiment, in order to have a smaller interfacial stress between the isolation layer 120 and the compensation layer 130, the inorganic materials in the isolation layer 120 and the compensation layer 130 are selected from the same materials, for example, the inorganic materials in the isolation layer 120 and the compensation layer 130 are both silicon dioxide materials or both silicon nitride materials.

In the embodiment of the present invention, the substrate layer 110 mainly plays a role of supporting, and the substrate layer 110 may be a single-layer substrate or a composite substrate. If substrate layer 110 is a composite substrate, the materials of each substrate layer may be the same or different, and are not limited in this application. For example: the substrate layer material may be lithium niobate, lithium tantalate, SOI, quartz, silicon, sapphire, silicon carbide, silicon nitride, gallium arsenide, indium phosphide, or the like, which is not limited in the present application.

In the embodiment of the present application, the functional thin film layer 140 is used for transmitting optical signals, and the refractive index of the functional thin film layer is greater than that of the compensation layer 130; the functional thin film layer 140 may be any electro-optic crystal material with piezoelectric properties, such as a lithium niobate crystal material, a lithium tantalate crystal material, a potassium titanyl phosphate crystal material, or a rubidium titanyl phosphate crystal material, which is not limited in the present application. It should be noted that the functional film layer 140 in the embodiment of the present application may include one film layer or may include multiple film layers. If the functional thin film layer 140 includes a plurality of thin film layers, an isolation layer may be further disposed between adjacent thin film layers, and the isolation layer may prevent signal crosstalk between adjacent thin film layers. In addition, the plurality of thin film layers in the functional thin film layer 140 may be made of the same material or different materials, which is not limited in the present application.

It should be further noted that the thicknesses of the substrate layer 110, the isolation layer 120, the compensation layer 130 and the functional thin film layer 140 are not limited in the embodiments of the present application. For example, the thickness of the substrate layer 110 may be 0.3 to 0.8mm, the thickness of the isolation layer 120 may be 50nm to 1000nm, the thickness of the compensation layer 130 may be 100nm to 10um, and the thickness of the functional thin film layer 140 may be 50 to 3000 nm.

In a specific example, the thickness of the substrate layer 110 may be 0.5mm, the thickness of the isolation layer 120 may be 200nm, the thickness of the compensation layer 130 may be 2um or 2.5um, and the thickness of the functional thin film layer 140 may be 400 nm.

Example two

The second embodiment of the present application is substantially the same as the first embodiment, except that the functional thin film layer 140 in the second embodiment of the present application is a doped electro-optic crystal material, where the doped electro-optic crystal material is doped with heavy ions, and the heavy ions are ions with a relative atomic mass greater than that of any element in the electro-optic crystal material.

As shown in fig. 3, the electro-optic crystal thin film in the embodiment of the present invention includes not only the compensation layer 130 doped with light ions, but also the functional thin film layer 140 doped with heavy ions, and the functional thin film layer 140 is doped with heavy ions, so that the refractive index of the doped functional thin film layer 140 is increased. Compared with the first embodiment, in the electro-optic crystal thin film provided by the second embodiment of the present application, the refractive index difference between the functional thin film layer 140 and the compensation layer 130 is further increased, and the effect of confining light in the functional thin film layer 140 is better.

In the embodiment of the present application, the heavy ions are not limited as long as the refractive index of the doped functional thin film layer 140 is increased. In addition, it should be noted that the heavy ions described in the embodiments of the present application refer to ions having a relative atomic mass at least greater than the relative atomic mass of one element in the electro-optical crystal material. For example, if the electro-optic crystal material in the functional thin film layer 140 is a lithium niobate crystal, the relative atomic mass of the heavy ions doped may be all ions greater than niobium, lithium, or oxygen, and in one specific example, the heavy ions doped in the lithium niobate crystal are germanium ions, copper ions, iron ions, or manganese ions.

In another embodiment, the heavy ions doped in the functional thin film layer 140 are rare earth ions having photoluminescence effect, such as: erbium ion, thulium ion, ytterbium ion or lutetium ionAnd (4) adding the active ingredients. The rare earth ions with photoluminescence effect doped in the functional thin film layer 140 can not only improve the refractive index, but also reduce the loss during light guiding. Taking rare earth element doped erbium ion as an example, Er³⁺The energy difference between the metastable state and the ground state is equivalent to the energy of 1550nm photons, and the 1550nm waveband optical signal is amplified, so that the loss in light guiding can be reduced.

EXAMPLE III

The third embodiment of the present application is substantially the same as the second embodiment, except that the third embodiment of the present application does not include the compensation layer 130, as shown in fig. 4, the third embodiment of the present application provides an electro-optic crystal film, including: the photoelectric composite film comprises a substrate layer 110, an isolation layer 120 and a functional thin film layer 140 which are sequentially stacked, wherein the refractive index of the functional thin film layer 140 is larger than that of the isolation layer 120, the functional thin film layer 140 is a doped electro-optic crystal material, the doped electro-optic crystal material is formed by doping heavy ions in the electro-optic crystal material, and the heavy ions are ions with relative atomic mass larger than that of any element in the electro-optic crystal material.

In the third embodiment of the present application, heavy ions are doped in the functional thin film layer 140 to increase the refractive index difference between the remaining isolation layers 120 of the functional thin film layer 140, so that light is better confined in the functional thin film layer 140.

Example four

The embodiment of the application also provides an electro-optical modulator which comprises the electro-optical crystal film in any embodiment. Among them, the functional thin film layer 140 plays a role of electro-optical modulation.

EXAMPLE five

An embodiment of the present application provides a method for preparing an electro-optic crystal thin film according to the first embodiment, as shown in fig. 5, the method includes the following steps:

step 11, preparing an isolation layer 120 with a target thickness on the substrate layer 110.

The preparation method of step 11 is not limited in this application, and for example, a deposition method may be adopted to deposit the isolation layer 120 with a target thickness on the substrate layer 110; for another example, if the substrate layer 110 is a silicon material and the isolation layer 120 is a silicon dioxide material, an oxidation method may be used to oxidize a silicon dioxide layer on the substrate layer 110 as the isolation layer 120.

It should be noted that, if the electro-optic crystal film described in the first embodiment includes the isolation layer 120, the step 11 is required to be performed to prepare the isolation layer 120, and then the step 12 is continuously performed on the prepared isolation layer 120; if the electro-optic crystal film of the first embodiment does not include the isolation layer 120, the step 11 is not required to be performed, and the compensation layer 130 is directly formed on the substrate layer 110, wherein the method for forming the compensation layer 130 on the substrate layer 110 is the same as the method for forming the compensation layer 130 in the step 12.

Step 12, preparing a compensation layer 130 on the isolation layer 120, where the compensation layer 130 is a doped inorganic material, the doped inorganic material is an inorganic material doped with light-weight ions, and the light-weight ions are ions with relative atomic mass smaller than that of any element in the inorganic material.

The light-weight ions in the embodiments of the present application refer to ions having a relative atomic mass at least smaller than that of one element in the inorganic material of the compensation layer 130, and preferably, the light-weight ions are selected from elements having a smaller relative atomic mass in the periodic table, such as lithium ions, boron ions, fluorine ions, phosphorus ions, and the like, so that the refractive index of the compensation layer 130 obtained after doping is smaller than that of the undoped inorganic material. The inorganic material in the compensation layer 130 may be silicon dioxide, silicon nitride material, etc., which is not limited in this application.

The method of forming the compensation layer 130 on the isolation layer 120 is not limited in the present application, and for example, a diffusion method, an ion implantation method, a deposition method, or a sputtering method may be used.

In one embodiment, the plasma enhanced chemical vapor deposition method is used to deposit TEOS, O₂、SiF₄As a doping source, under the conditions of deposition temperature of 100-500 ℃, gas pressure of 50-1000 Pa in the reaction chamber, and radio frequency power of 50-1000W, wherein the gas flow rate of TEOS is 20sccm,O₂the gas flow rate of (1) is 5-60 sccm, SiF₄The gas flow of (2) is 5-60 sccm, and doped silicon dioxide is deposited on the isolation layer 120, wherein the doped silicon dioxide is silicon dioxide doped with fluorine atoms. Specifically, the silicon dioxide doped with different fluorine ion contents can be obtained by changing the gas flow of the doping source. Silica doped with different fluorine ion content will correspond to different refractive indices.

Step 13, preparing a functional thin film layer 140 on the compensation layer 130, wherein the refractive index of the functional thin film layer 140 is greater than that of the compensation layer 130.

The method of forming the functional thin film layer 140 on the compensation layer 130 is not limited in the present application, and for example, the functional thin film layer 140 may be formed on the compensation layer 130 by an ion implantation method and a bonding and separation method, or by a bonding method and a polishing and grinding method.

If the functional thin film layer 140 is formed on the compensation layer 130 by using an ion implantation and bonding separation method, in the embodiment of the present application, any feasible ion implantation method and any feasible bonding method may be combined to form the electro-optic crystal thin film, which is not limited in the present application.

In one implementation, the functional thin film layer 140 is fabricated on the compensation layer 130 by an ion implantation and bonding separation method, including the steps of:

step 131, performing ion implantation into the film substrate, and dividing the film substrate into a film layer, a separation layer and a residual layer in sequence.

The thin film substrate in step 131 is a base material with a certain thickness for obtaining the functional thin film layer, i.e. a wafer with a certain thickness. The thin film substrate may be an electro-optic crystal material such as lithium niobate or lithium tantalate, but is not limited in this application.

Ion implantation may be performed from one surface of the film substrate into the film substrate, thereby forming the thin film layer, the separation layer, and the remaining layer on the film substrate.

The ion implantation method in the embodiment of the present application is not particularly limited, and any one of the ion implantation methods in the prior art may be usedThe implanted ions may be ions that can generate gas by heat treatment, for example: hydrogen ions or helium ions. When implanting hydrogen ions, the implantation dose can be 3 × 10¹⁶ions/cm²～8×10¹⁶ions/cm²The implantation energy can be 120 KeV-400 KeV; when implanting helium ions, the implantation dose can be 1 × 10¹⁶ions/cm²～1×10¹⁷ions/cm²The implantation energy may be 50KeV to 1000 KeV. For example, when implanting hydrogen ions, the implantation dose may be 4 × 10¹⁶ions/cm²The implantation energy may be 180 KeV; when implanting helium ions, the implantation dose is 4 × 10¹⁶ions/cm²The implantation energy was 200 KeV.

In the embodiment of the application, the thickness of the thin film layer can be adjusted by adjusting the ion implantation depth, specifically, the larger the ion implantation depth is, the larger the thickness of the prepared thin film layer is; conversely, the smaller the depth of ion implantation, the smaller the thickness of the thin film layer produced.

And 132, bonding the ion implantation surface of the film substrate with the compensation layer 130 to obtain a bonded body.

In the embodiment of the present application, the bonded body refers to a bonded body formed after a thin film substrate is bonded to a compensation layer 130, wherein the thin film substrate is not peeled off from the compensation layer 130, and the ion implantation surface refers to a surface on which ions are implanted toward the thin film substrate.

The bonding method of the thin film substrate and the compensation layer 130 is not particularly limited in the present application, and any bonding method in the prior art may be adopted, for example, the bonding surface of the thin film substrate is surface-activated, the bonding surface of the compensation layer 130 is also surface-activated, and then the two activated surfaces are bonded to obtain a bonded body.

The method for surface activation of the bonding surface of the thin film substrate is not particularly limited, and any method for surface activation of the thin film substrate in the prior art, such as plasma activation and chemical solution activation, may be used; similarly, the bonding surface of the compensation layer 130 is not particularly limited, and any one of the methods available in the prior art for surface activation of the bonding surface of the compensation layer 130, such as plasma activation, may be used.

Step 133, performing a heat treatment on the bonded body to separate the remaining layer from the thin film layer.

In an implementation manner, the bonded body is subjected to heat treatment, the temperature of the heat treatment is 100-600 ℃, bubbles are formed in the separation layer during the heat treatment, for example, H ions form hydrogen, He ions form helium and the like, the bubbles in the separation layer are connected into one piece as the heat treatment progresses, finally, the separation layer is cracked, the residual layer is separated from the functional thin film layer, so that the residual layer is stripped from the bonded body, a functional thin film layer is formed on the surface of the compensation layer 130, and then the functional thin film layer is polished and thinned to 50-3000nm (for example, 400nm, 500nm, 600nm, 800nm, 1000nm and the like), so that the functional thin film layer with the nanometer-scale thickness is obtained. The functional film layer can be made of lithium niobate, lithium tantalate, potassium titanyl phosphate or rubidium titanyl phosphate.

In the embodiment of the present application, an achievable heat treatment manner is to put the bonding body into a heating device, first raise the temperature to a preset temperature, and then keep the temperature at the preset temperature. Among them, preferably, the heat-preserving conditions include: the holding time may be 1 minute to 48 hours, for example, 3 hours, the holding temperature may be 100 ℃ to 600 ℃, for example, 400 ℃, and the holding atmosphere may be in a vacuum atmosphere or in a protective atmosphere of at least one of nitrogen and an inert gas. Through the heat treatment, the bonding force between the thin film layer and the compensation layer can be improved to be more than 10MPa, and the damage of ion implantation to the thin film layer can be recovered, so that the properties of the obtained functional thin film layer and the electro-optic crystal material are close.

In another implementation, the functional thin film layer 140 is prepared on the compensation layer 130 by a bonding method and a grinding and polishing method, and the method comprises the following steps:

firstly, bonding the prepared film substrate and the compensation layer 130 to obtain a bonded body, wherein the manner of bonding the film substrate and the compensation layer 130 may refer to the description of step 132, and is not repeated herein. Then, the bonding body is subjected to heat treatment to improve the bonding force between the thin film substrate and the compensation layer 130. For example, the bonding body is placed in a heating device and is subjected to heat preservation at a high temperature, the heat preservation process is performed in a vacuum environment or in a protective atmosphere formed by at least one of nitrogen and inert gas, the heat preservation temperature can be 100 ℃ to 600 ℃, for example, the heat preservation time is 400 ℃, and the heat preservation time can be 1 minute to 48 hours, for example, the heat preservation time is 3 hours. And finally, mechanically grinding and polishing the film substrate on the bonding body, and thinning the film substrate to the thickness of the preset functional film layer. For example, if the thickness of the preset functional thin film layer is 20 μm, the electro-optic crystal material on the bonding body may be thinned to 22 μm by mechanical grinding, and then polished to 20 μm, so as to obtain the functional thin film layer. Wherein, the thickness of the functional film layer can be 400nm-100 μm, and the functional film layer can be made of lithium niobate or lithium tantalate.

EXAMPLE six

A sixth embodiment of the present application provides a method for preparing the electro-optic crystal thin film described in the second embodiment, which is substantially the same as the method provided in the fifth embodiment, except that the sixth embodiment of the present application further includes a step of doping heavy mass ions in the thin film matrix to form a doped electro-optic crystal material.

In the embodiment of the application, in order to enable optical signals to be better limited to be transmitted in the functional thin film layer, heavy ions are doped in the thin film substrate, and the refractive index of the functional thin film layer is further improved. The heavy ions may be rare earth ions having a photoluminescence effect, such as erbium ions, thulium ions, ytterbium ions, lutetium ions, or germanium ions, copper ions, iron ions, or manganese ions, which is not limited in this application, as long as the refractive index of the doped functional thin film layer is increased and the difference between the refractive index of the doped functional thin film layer and the refractive index of the compensation layer 130 is greater than or equal to 0.01. Wherein the refractive index difference of 0.01 is a critical value that the optical signal can be limited to be transmitted in a medium with a large refractive index. If the difference between the refractive indices of the functional thin film layer 140 and the compensation layer 130 is less than 0.01, the optical signal cannot be confined to be transmitted in the functional thin film layer 140.

It should be noted that, the doping concentration in the embodiment of the present application is not limited, and may be adjusted according to actual needs, for example, the doping concentration of the heavy ions doped in the functional thin film layer is 50-500ppm, and more preferably, the doping concentration is 120-200 ppm. In a specific example, erbium ions are doped in the lithium niobate crystal, wherein the doping concentration of the erbium ions is 120-200ppm, so that the refractive index of the doped lithium niobate crystal is larger than that of the undoped lithium niobate crystal.

In the embodiment of the present application, the functional thin film layer prepared on the compensation layer 130 is doped with heavy ions, specifically, a thin film substrate doped with heavy ions, that is, a doped electro-optic crystal material, may be prepared in advance, and then the functional thin film layer is prepared by using the doped electro-optic crystal material, for example, the functional thin film layer 140 is prepared on the compensation layer 130 by using an ion implantation method and a bonding and polishing method, or by using a bonding method and a grinding and polishing method.

In one embodiment, first, a doping treatment is performed on a thin film substrate, and heavy ions are doped in the thin film substrate to form a doped electro-optic crystal material, wherein the method for preparing the doped electro-optic crystal material is not limited in this application, and for example, the heavy ions may be diffused into the electro-optic crystal material by a diffusion method to form the doped electro-optic crystal material. And then, carrying out ion implantation in the doped film matrix, and sequentially dividing the doped film matrix into a film layer, a separation layer and a residual layer. And bonding the ion implantation surface of the doped film substrate with the compensation layer 130 to obtain a bonded body, and finally, carrying out heat treatment on the bonded body to separate the residual layer from the film layer. The functional thin film layer prepared by the method is a doped electro-optic crystal material doped with heavy ions.

In another embodiment, the film matrix is first doped to dope the heavy mass ions into the film matrix to form a doped electro-optic crystalline material. And then bonding the doped film substrate with the compensation layer 130 to obtain a bonding body, and performing heat treatment on the bonding body to improve the bonding force between the doped film substrate and the compensation layer 130. And finally, mechanically grinding and polishing the doped film substrate on the bonding body, and thinning the doped film substrate to the thickness of the preset functional film layer.

Further, after the bonded body is obtained, in the step of performing heat treatment on the bonded body in the embodiment of the present application, the doped thin film substrate on the bonded body is placed in a diffusion device filled with a heavy-mass ion diffusing agent, and the doped thin film substrate on the bonded body is subjected to heat treatment under a preset holding temperature condition.

In the embodiment of the application, because the electro-optical material in the obtained bonding body is doped with heavy ions, if the bonding body is directly heated, the heavy ions doped in the electro-optical crystal material can diffuse from the doped electro-optical crystal material with high chemical potential to the air, so that the heavy ions in the doped electro-optical crystal material are absent. Therefore, in order to avoid diffusion of heavy ions doped in the electro-optic crystal material in the step of heat treating the bonding body, the embodiment of the application places the film substrate doped with heavy ions on the bonding body in a diffusion device filled with a heavy ion diffusing agent during the heat treating of the bonding body, and heat treats the film substrate doped with heavy ions on the bonding body under the preset holding temperature condition, so that the heavy ions in the diffusing agent with high chemical potential are diffused into the film substrate with low chemical potential, the absence of the heavy ions doped in the film substrate is avoided, and the components in the doped film substrate are close to the ideal stoichiometric ratio.

In a specific embodiment, the electro-optical crystal material is a lithium niobate crystal, erbium ions are doped in the lithium niobate crystal, after the bonding body obtained in step 132 is obtained, the lithium niobate crystal doped with erbium ions in the bonding body is placed in a diffusion device filled with an erbium-containing ion diffusing agent, and the lithium niobate crystal is heated for less than 100 hours at 200-700 ℃, so that erbium phases in the diffusing agent with high chemical potential are diffused into the lithium niobate crystal with low chemical potential, thereby avoiding the loss of erbium elements in the lithium niobate crystal and enabling the components in the lithium niobate crystal to approach to an ideal stoichiometric ratio.

EXAMPLE seven

An embodiment seven of the present application provides another method for preparing an electro-optic crystal film according to the first embodiment, as shown in fig. 6, the method includes the following steps:

step 21, preparing an isolation layer 120 of a target thickness on the substrate layer 110.

It should be noted that, if the electro-optic crystal film described in the first embodiment includes the isolation layer 120, the step 21 is performed to prepare the isolation layer 120, and then the step 22 is performed on the prepared isolation layer 120; if the electro-optic crystal film of the first embodiment does not include the isolation layer 120, the step 21 is not required to be performed, and the first compensation layer 130A is directly formed on the substrate layer 110, wherein the method for forming the first compensation layer 130A on the substrate layer 110 is the same as the method for forming the first compensation layer 130A in the step 22.

Step 22, preparing a first compensation layer 130A on the isolation layer 120, where the first compensation layer 130A is a doped inorganic material, the doped inorganic material is an inorganic material doped with light-weight ions, and the light-weight ions are ions whose relative atomic mass is smaller than that of any element in the inorganic material.

The material and method of the first compensation layer 130A prepared in step 22 are the same as those of the compensation layer 130 prepared in step 12, except that the thickness of the first compensation layer 130A prepared in the seventh embodiment of the present application is smaller than that of the compensation layer 130, in the seventh embodiment of the present application, the first compensation layer 130A with the first thickness and the second compensation layer 130B with the second thickness are respectively prepared, and then the prepared first compensation layer 130A and the prepared second compensation layer 130B are bonded to obtain the compensation layer 130 with the thickness equivalent to that in step 12.

It should be noted that, in step 22, the light-weight ions doped in the inorganic material and the method for doping the light-weight ions can be referred to as step 12, and are not described herein again.

Step 23, preparing a second compensation layer 130B on the film substrate 140A, wherein the second compensation layer 130B is made of the same material as the first compensation layer 130A.

The second compensation layer 130B may be formed on the thin film substrate 140A in the same manner as the first compensation layer 130A is formed, for example, by depositing an inorganic material doped with light-weight ions on the thin film substrate 140A using a vapor deposition method of plasma enhanced chemistry. The light-weight ions doped in the inorganic material in step 23 and the method for doping the light-weight ions can be referred to as step 12, and are not described herein again.

The thickness of the second compensation layer 130B may be the same as or different from the thickness of the first compensation layer 130A, which is not limited in this application. However, the inorganic material, the light-weight ions doped, and the doping concentration in the first compensation layer 130A and the second compensation layer 130B are the same.

For the selection of the light-weight ions and inorganic materials to be doped, see example five, the details are not repeated here.

It should be noted that the thin film substrate in step 23 is the same as the thin film substrate 140A in step 131, and refers to a base material for obtaining a functional thin film layer, that is, a wafer having a certain thickness.

And 24, bonding the first compensation layer 130A and the second compensation layer 130B to obtain a bonded body.

Different from the way of directly bonding the compensation layer 130 and the film substrate in the fifth embodiment, in the seventh embodiment of the present application, the plasma activation processing is performed on the surfaces of the first compensation layer 130A and the second compensation layer 130B, then the two activated surfaces are bonded, and the substrate layer 110, the isolation layer 120, and the first compensation layer 130A are transferred onto the second compensation layer 130A to form a bonded body.

In an embodiment, the inorganic material in the first compensation layer 130A and the second compensation layer 130B is silicon dioxide, and the doped light ions are fluorine ions, and according to a seventh embodiment of the present disclosure, after the surface activation of the first compensation layer 130A and the second compensation layer 130B by plasma bombardment, the surface OH is activated^-The dangling bonds are increased, the hydrophilicity is enhanced, and the prebonding is realized. Further, the pre-bond may be annealed at 200 ℃ or higher to form OH on the surfaces of the first and

second compensation layers

130A and 130B^-The dangling bonds form O-O or Si-O covalent bonds, so that stronger bonding strength is obtained, and water molecules are released at the same time. Fluorine ions doped in the inorganic material and silicon dioxide form silicon oxyfluoride, and the silicon oxyfluoride has good water absorption, so that the silicon oxyfluoride can absorb water molecules released by a bonding interface to expand the volume, thereby increasing the contact area of the first compensation layer 130A and the second compensation layer 130B and improving the bonding force.

It should be noted that after the bonding body is obtained, the bonding body may be further subjected to heat treatment to improve the bonding force, and the specific processing method may refer to step 133, which is not described herein again.

Step 25, grinding and polishing the film substrate 140A on the bonding body to a preset thickness to obtain the functional film layer 140, wherein the refractive index of the functional film layer 140 is greater than that of the first compensation layer 130A.

For example, if the thickness of the predetermined functional thin film layer is 20 μm, the thin film substrate 140A on the bonding body may be first thinned to 22 μm by mechanical grinding, and then polished to 20 μm, so as to obtain the functional thin film layer. Wherein, the thickness of the functional film layer can be 400nm-100 μm, and the functional film layer can be made of lithium niobate or lithium tantalate.

Example eight

The eighth embodiment of the present application has the same basic idea as the seventh embodiment, and an electro-optical crystal thin film is obtained by bonding a first compensation layer and a second compensation layer which are respectively prepared, but the eighth embodiment of the present application is different from the seventh embodiment in that an ion implantation method and a bonding separation method are used to prepare the electro-optical crystal thin film.

The preparation method of the electro-optic crystal film provided by the eighth embodiment of the application comprises the following steps:

step 31, preparing an isolation layer 120 of a target thickness on the substrate layer 110.

It should be noted that, if the electro-optic crystal film described in the first embodiment includes the isolation layer 120, the step 31 is required to be performed to prepare the isolation layer 120, and then the step 32 is continuously performed on the prepared isolation layer 120; if the electro-optic crystal film of the first embodiment does not include the isolation layer 120, the step 31 is not required to be performed, and the first compensation layer 130A is directly formed on the substrate layer 110, wherein the method for forming the first compensation layer 130A on the substrate layer 110 is the same as the method for forming the first compensation layer 130A in the step 32.

Step 32, preparing a first compensation layer 130A on the isolation layer 120, where the first compensation layer 130A is a doped inorganic material, the doped inorganic material is an inorganic material doped with light-weight ions, and the light-weight ions are ions whose relative atomic mass is smaller than that of any element in the inorganic material.

Step 33, ion implantation is performed on the thin film substrate 140A to form a thin film layer, a separation layer, and a residual layer.

Step 31 and step 32 may refer to step 21 and step 22, and step 33 may refer to step 131, which are not described herein again.

Step 34, preparing a second compensation layer 130B on the ion implantation surface of the film substrate 140A, wherein the second compensation layer 130B is made of the same material as the first compensation layer 130A.

The ion implantation surface of the film substrate 140A in the step 34 is a surface close to the surface on which the thin film layer is formed, and the thin film layer is not yet peeled off from the film substrate 140A. For a specific method for preparing the second compensation layer, refer to step 23, and will not be described herein.

And step 35, bonding the first compensation layer 130A and the second compensation layer 130B to obtain a bonded body.

Step 35 can refer to step 24, and is not described herein.

And step 36, performing heat treatment on the bonding body to obtain a functional thin film layer 140, wherein the refractive index of the functional thin film layer 140 is greater than that of the first compensation layer.

And performing heat treatment on the bonding body obtained in the step 35, and separating the residual layer from the thin film layer to obtain a functional thin film layer stacked on the second compensation layer 130B.

The method for separating the residual layer from the thin film layer by performing heat treatment on the bonded body obtained in step 35 may refer to step 133, and details are not repeated here.

Example nine

The ninth embodiment is substantially the same as the seventh or eighth embodiment, except that the ninth embodiment further includes a step of doping heavy mass ions into the thin film substrate 140A.

In this embodiment, a film substrate doped with heavy ions may be prepared in advance, and then the second compensation layer 130B is prepared on the doped film substrate, and the electro-optic crystal film described in example two is further prepared by using a bonding method and a grinding and polishing method (e.g., the preparation method provided in example seven), or by using an ion implantation method and a bonding and separating method (e.g., the preparation method provided in example eight).

In one embodiment, first, doping the thin film substrate 140A to dope heavy ions into the thin film substrate 140A to form a doped electro-optic crystal material; then, preparing a second compensation layer 130B on the doped film substrate 140A, bonding the first compensation layer 130A prepared in step 22 with the second compensation layer 130B to obtain a bonded body, and performing heat treatment on the bonded body to improve the bonding force; and finally, mechanically grinding and polishing the doped film substrate 140A on the bonding body, and thinning the doped film substrate 140A to the thickness of the preset functional film layer.

In another specific implementation, first, the thin film substrate 140A is doped, and heavy ions are doped in the thin film substrate 140A to form a doped electro-optic crystal material, where the method for preparing the doped electro-optic crystal material is not limited in this application, and for example, the heavy ions may be diffused into the electro-optic crystal material by a diffusion method to form the doped electro-optic crystal material; and then, performing ion implantation on the doped film substrate 140A, dividing the doped film substrate 140A into a film layer, a separation layer and a residual layer in sequence, then, preparing a second compensation layer on the film layer, bonding the first compensation layer 130A prepared in the step 32 with the second compensation layer 130B to obtain a bonded body, performing heat treatment on the bonded body, and separating the residual layer from the film layer to obtain a functional film layer stacked on the second compensation layer.

Further, after the bonding body is obtained, in the step of performing heat treatment on the bonding body, the doped film substrate 140A on the bonding body is placed in a diffusion device filled with a heavy-mass ion diffusing agent, and the doped film substrate 140A on the bonding body is subjected to heat treatment under the condition of a preset heat preservation temperature. For details, reference may be made to embodiment six, which is not described herein again.

Example ten

An embodiment of the present application provides a method for preparing an electro-optic crystal thin film according to the third embodiment, as shown in fig. 7, where the method includes the following steps:

step 41, preparing an isolation layer 120 of a target thickness on the substrate layer 110.

Step 42, preparing a functional thin film layer 140 on the isolation layer 120, wherein the refractive index of the functional thin film layer 140 is greater than that of the isolation layer 120, the functional thin film layer 140 is a doped electro-optic crystal material, the doped electro-optic crystal material is formed by doping heavy ions in the electro-optic crystal material, and the heavy ions are ions with relative atomic mass greater than that of any element in the electro-optic crystal material.

In the tenth embodiment of the present application, the functional thin film layer 140 is directly prepared on the isolation layer 12, where the functional thin film layer 140 refers to an electro-optic crystal material doped with heavy ions, and for the method for doping heavy ions in the electro-optic crystal material, reference may be made to the sixth embodiment, which is not described herein again.

In the embodiment of the present application, the functional thin film layer 140 formed on the isolation layer 120 is doped with heavy ions, specifically, a thin film substrate doped with heavy ions may be prepared in advance, and then the doped thin film substrate is used to form the functional thin film layer, for example, the doped thin film substrate is used to form the functional thin film layer 140 on the isolation layer 120 by using an ion implantation method and a bonding separation method, or a bonding method and a grinding and polishing method. Specifically, reference may be made to embodiment six, which is not described herein again.

In addition, in this embodiment of the application, after the bonded body is obtained, in the step of performing heat treatment on the bonded body, the doped thin film substrate on the bonded body is placed in a diffusion device filled with a heavy-mass ion diffusing agent, and the doped thin film substrate on the bonded body is subjected to heat treatment under a preset holding temperature condition. Specifically, reference may be made to embodiment six, which is not described herein again.

The same and similar parts in the various embodiments in this specification may be referred to each other.

The present application has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to limit the application. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the presently disclosed embodiments and implementations thereof without departing from the spirit and scope of the present disclosure, and these fall within the scope of the present disclosure. The protection scope of this application is subject to the appended claims.

Claims

1. An electro-optic crystal film, comprising: the substrate layer, the compensation layer and the functional film layer are sequentially stacked; the refractive index of the functional thin film layer is larger than that of the compensation layer, wherein the compensation layer is made of a doped inorganic material, the doped inorganic material is formed by doping light-weight ions in the inorganic material, and the light-weight ions are ions with relative atomic mass smaller than that of any element in the inorganic material.

2. The electro-optic crystal film of claim 1, wherein the functional film layer is a doped electro-optic crystal material, and the doped electro-optic crystal material is doped with heavy ions, wherein the heavy ions are ions with a relative atomic mass greater than the relative atomic mass of any element in the electro-optic crystal material.

3. An electro-optic crystal film according to claim 2, wherein the heavy mass ions comprise rare earth ions having a photoluminescent effect.

4. The electro-optic crystal film of claim 3, wherein the rare earth ions having a photoluminescence effect comprise erbium ions, thulium ions, ytterbium ions, or lutetium ions.

5. The electro-optic crystal film of claim 2, wherein the heavy mass ions comprise germanium ions, copper ions, iron ions, or manganese ions.

6. The electro-optic crystal film of claim 1, wherein the light mass ions comprise lithium ions, boron ions, fluorine ions, or phosphorus ions.

7. The electro-optic crystal film of claim 1, further comprising an isolation layer laminated between the substrate layer and the compensation layer.

8. The electro-optic crystal film of claim 7, wherein the spacer layer is a silicon dioxide or silicon nitride material, the electro-optic crystal material is a lithium niobate crystal material, a lithium tantalate crystal material, a potassium titanyl phosphate crystal material, or a rubidium titanyl phosphate crystal material, and the inorganic material is a silicon dioxide or silicon nitride.

9. The electro-optic crystal film of claim 8, wherein the spacer layer is the same material as the inorganic material.

10. An electro-optic modulator comprising the electro-optic crystal film of any one of claims 1-9.

11. An electro-optic crystal film, comprising: the photoelectric composite film comprises a substrate layer, an isolation layer and a functional thin film layer which are sequentially stacked, wherein the refractive index of the functional thin film layer is larger than that of the isolation layer, the functional thin film layer is a doped photoelectric crystal material, the doped photoelectric crystal material is formed by doping heavy ions in the photoelectric crystal material, and the heavy ions are ions with relative atomic mass larger than that of any element in the photoelectric crystal material.

12. An electro-optic crystal film according to claim 11, wherein the heavy mass ions comprise rare earth ions having a photoluminescent effect.

13. The electro-optic crystal film of claim 12, wherein the rare earth ions having a photoluminescent effect comprise erbium ions, thulium ions, ytterbium ions, or lutetium ions.

14. The electro-optic crystal film of claim 11, wherein the heavy mass ions comprise germanium ions, copper ions, iron ions, or manganese ions.

15. An electro-optic modulator comprising the electro-optic crystal film of any one of claims 11-14.

16. A method of making an electro-optic crystal film, the method comprising:

17. The method of claim 16, further comprising:

18. The method of claim 16, further comprising:

preparing an isolation layer in advance between the substrate layer and the compensation layer, wherein the isolation layer is laminated between the substrate layer and the compensation layer.

19. The method according to any one of claims 16 to 18, wherein a functional thin film layer is formed on the compensation layer by an ion implantation method and a bonding separation method, or by a bonding method and an abrasive polishing method.

20. A method of making an electro-optic crystal film, the method comprising:

21. The method of claim 20, further comprising, prior to said preparing a second compensation layer on the thin film substrate:

22. The method of claim 21, further comprising, after obtaining the bond:

23. The method of claim 20, further comprising:

preparing an isolation layer in advance between the substrate layer and the first compensation layer, wherein the isolation layer is laminated between the substrate layer and the first compensation layer.

24. A method of making an electro-optic crystal film, the method comprising:

25. The method of claim 24, further comprising, prior to ion implanting the thin film substrate:

26. The method of claim 25, further comprising, after obtaining the bond:

27. The method of claim 24, further comprising:

28. A method of making an electro-optic crystal film, the method comprising:

preparing an isolation layer with a target thickness on the substrate layer;