Preparation method of electro-optical modulator

Abstract

The invention relates to a preparation method of an electro-optical modulator. The preparation method comprises the following steps: thinning one side, opposite to a first pressure stress layer, of a first substrate of an electro-optical material wafer, so that the electro-optical material wafer warps and protrudes towards one side of an initial electro-optical material layer; grinding the warped convex part of the initial electro-optical material layer to form a plurality of strip-shaped grooves with slope structures on two sides; the strip-shaped grooves at least penetrate through the initial electro-optical material layer in the depth direction; cutting the electro-optical material wafer and removing the first substrate and the pressure stress layer, wherein the residual initial electro-optical material layer is used as an electro-optical material layer; the electro-optical material layer is bonded to the surface of the side, back on to the waveguide core, of the bonding dielectric layer; wherein the electro-optical material layer corresponds to the waveguide core; the slope structures are located on the two sides of the waveguide core in the length direction. According to the preparation method, the etching process on the electro-optical material layer can be avoided or reduced, the process efficiency and the utilization rate of the electro-optical material are improved, the process flow is simplified, and the light field transition loss of the electro-optical modulator is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for preparing an electro-optical modulation device. Background Art

[0002] The stoichiometric silicon nitride (Si3N4) film / waveguide core prepared by low pressure chemical vapor deposition (LPCVD) has transparency in a wide wavelength range (400nm~2350nm), low optical propagation loss at high optical power, and uses wafer-level manufacturing process. The waveguide platform composed of silicon nitride waveguide core, silicon (Si) substrate, and silicon dioxide (SiO2) cladding realizes a wide range of planar integrated devices and chip-level solutions. Phase modulator is one of the core devices of photonic integrated circuits. Photonic platforms based on silicon nitride can usually use thermo-optical effect, stress-optical effect, etc. to achieve optical phase modulation. However, due to the limitations of material properties such as thermal conduction speed, charging and discharging time, and device structure, these modulators are still insufficient in speed, power, and efficiency. A popular alternative is electro-optic modulation, but the electro-optical effect of silicon nitride is very weak, and it must be combined with materials with significant electro-optical effect to achieve efficient electro-optical phase modulation. Among them, single crystal lithium niobate (LiNbO3) has a strong electro-optical effect (1550nm: r 33 =30.8pm / V), larger refractive index (1550nm: n o =2.21,n e =2.14), a wide light transmission window (400nm~5μm) and stable physical and chemical properties, making it the most competitive electro-optical modulation material.

[0003] One of the challenges facing heterogeneous integration of lithium niobate and silicon nitride waveguide platforms is the low-loss transition of the optical field between silicon nitride waveguide and silicon nitride-lithium niobate composite waveguide. The solutions for realizing the light field transition between lithium niobate and silicon nitride waveguide in the existing technical solutions all have certain defects: Solution 1: Integrate lithium niobate with a two-dimensional conical structure into a silicon nitride platform through a transfer process to realize the light field transition, but this solution requires that the two-dimensional conical structure and the silicon nitride optical waveguide core have a high alignment accuracy, which increases the process difficulty; Solution 2: Perform multiple dry etching on lithium niobate so that lithium niobate forms multiple steps along both sides of the silicon nitride waveguide core to realize the light field transition. Since dry etching of lithium niobate is relatively difficult, the process difficulty is high, and there is a potential contamination problem, which will lead to incompatibility with CMOS (complementary metal oxide semiconductor) process equipment; Solution 3: Use sputtering to form a mask with a gradient thickness on the surface of the film, and use chemical mechanical polishing (CMP) to make the lithium niobate film have a gradient thickness, but this solution has the problems of low mask production efficiency, difficulty in forming multiple gradient thickness masks on the same substrate, or the mask size (resulting in the size of the gradient thickness film) cannot be accurately controlled.

[0004] Therefore, a method for preparing an electro-optical modulation device is needed, which uses a one-step or lithium niobate-free etching process to achieve a low-loss transition between a silicon nitride waveguide and a silicon nitride-lithium niobate composite waveguide, thereby reducing the transition loss of a heterogeneous integrated electro-optic phase modulation device. Summary of the invention

[0005] Therefore, the present invention provides a method for preparing an electro-optical modulation device to solve the problems in the existing method for preparing an electro-optical modulation device that the transfer of the two-dimensional conical structure lithium niobate is difficult, multiple steps of lithium niobate dry etching are required, and the thickness gradient mask is difficult to accurately control, resulting in high light field transition loss between the silicon nitride waveguide and the silicon nitride-lithium niobate composite waveguide.

[0006] The present invention provides a method for preparing an electro-optical modulation device, comprising:

[0007] Providing an electro-optic material wafer, the electro-optic material wafer sequentially comprising a first substrate, a first compressive stress layer and an initial electro-optic material layer stacked;

[0008] Thinning the side of the first substrate facing away from the first compressive stress layer, and causing the electro-optical material wafer to warp and bulge toward the initial electro-optical material layer;

[0009] The first substrate is fixed, and the warped convex part of the initial electro-optical material layer is ground until a part of the first compressive stress layer or the first substrate is exposed, so as to form a plurality of strip-shaped grooves with slope structures on both sides; the strip-shaped grooves at least penetrate the initial electro-optical material layer and penetrate into the first compressive stress layer in the depth direction;

[0010] Cutting the ground electro-optical material wafer to form electro-optical material wafer chips; the electro-optical material wafer chips include a portion of the first substrate, a portion of the first compressive stress layer, and a portion of the initial electro-optical material layer with slope structures on both sides;

[0011] removing the first substrate and the first compressive stress layer in the electro-optic material wafer die, and using the remaining initial electro-optic material layer as the electro-optic material layer;

[0012] Providing a second substrate, and sequentially forming a lower cladding layer, a waveguide core, and a bonding dielectric layer on a surface of one side of the second substrate, wherein the bonding dielectric layer covers a surface of the waveguide core that is away from the second substrate and a side surface of the waveguide core;

[0013] Bonding the electro-optic material layer to the surface of the bonding medium layer facing away from the waveguide core; wherein the electro-optic material layer corresponds to the waveguide core; and the slope structure is located on both sides of the length direction of the waveguide core;

[0014] Electrodes are formed on a surface of the electro-optic material layer that is opposite to the bonding medium layer, and the electrodes are located at corresponding positions on both sides of the waveguide core.

[0015] Optionally, in the step of providing an electro-optical material wafer, the electro-optical material wafer sequentially comprises a stacked first substrate, a plurality of mutually parallel columns of first compressive stress layers, and a plurality of mutually parallel columns of initial electro-optical material layers; the length direction of the plurality of columns of first compressive stress layers is the same as the length direction of the plurality of columns of initial electro-optical material layers; each column of initial electro-optical material layers is located on at least one column of first compressive stress layers;

[0016] In the step of thinning the side of the first substrate facing away from the first compressive stress layer and causing the electro-optic material wafer to warp and bulge toward the side of the initial electro-optic material layer, the electro-optic material wafer is warped along the length direction of each column of the initial electro-optic material layer;

[0017] Fix the first substrate and grind the warped raised portion of the initial electro-optical material layer until a portion of the first compressive stress layer or the first substrate is exposed, thereby forming a plurality of strip grooves with slope structures on both sides, wherein the length direction of the strip grooves is perpendicular to the length direction of the plurality of columns of the initial electro-optical material layer.

[0018] Optionally, the step of providing an electro-optical material wafer includes:

[0019] forming a first compressive stress layer on a first substrate;

[0020] forming an initial electro-optical material layer on a surface of the first compressive stress layer facing away from the first substrate;

[0021] The first compressive stress layer and the initial electro-optic material layer are subjected to a patterning process to form a plurality of mutually parallel columns of the first compressive stress layer and a plurality of mutually parallel columns of the initial electro-optic material layer.

[0022] Optionally, the step of providing an electro-optical material wafer includes:

[0023] forming a first compressive stress layer on a first substrate;

[0024] Performing a patterning process on the first compressive stress layer to form a plurality of mutually parallel rows of first compressive stress layers;

[0025] forming an initial electro-optical material layer on a surface of the plurality of columns of first compressive stress layers facing away from the first substrate;

[0026] The initial electro-optic material layer is patterned to form multiple parallel columns of initial electro-optic material layers; the length direction of the multiple columns of first compressive stress layers is the same as the length direction of the multiple columns of initial electro-optic material layers; each column of initial electro-optic material layers is located on at least one column of first compressive stress layers.

[0027] Optionally, in the step of forming an initial electro-optic material layer on a surface of the plurality of columns of first compressive stress layers facing away from the first substrate, a crystal orientation of the initial electro-optic material layer is parallel to, perpendicular to or at a certain angle to a length direction of the plurality of columns of compressive stress layers.

[0028] Optionally, before the step of forming an initial electro-optical material layer on a surface of a side of the plurality of columns of first compressive stress layers facing away from the first substrate, the method further includes:

[0029] Forming a sacrificial layer on the multiple columns of first compressive stress layers; the sacrificial layer covers the surface of the first compressive stress layer facing away from the first substrate and the side surfaces of the multiple columns of first compressive stress layers;

[0030] The step of forming an initial electro-optical material layer on a surface of a plurality of columns of first compressive stress layers facing away from the first substrate comprises:

[0031] An initial electro-optical material layer is formed on a surface of the sacrificial layer facing away from the first compressive stress layer.

[0032] Optionally, the sacrificial layer is a photoresist or a temporary bonding adhesive layer;

[0033] The thickness of the sacrificial layer above the first compressive stress layer is 1 μm to 5 μm.

[0034] Optionally, the step of cutting the ground electro-optical material wafer to form electro-optical material wafer chips includes:

[0035] The ground electro-optic material wafer is cut along the length direction of the strip grooves and the length direction of the multiple columns of initial electro-optic material layers to form electro-optic material wafer chips.

[0036] Optionally, the plurality of columns of first compressive stress layers are completely strip-shaped first compressive stress layers that expose a portion of the surface of the first substrate, or ridge-shaped strip-shaped first compressive stress layers that do not expose the surface of the first substrate.

[0037] Optionally, the step of fixing the first substrate, grinding the warped raised portion of the initial electro-optical material layer until a portion of the first compressive stress layer or the first substrate is exposed, and forming a plurality of strip-shaped grooves with slope structures on both sides includes:

[0038] Fixing the warped electro-optical material wafer on a support platform having a cylindrical surface, wherein a side of the first substrate facing away from the first compressive stress layer is in contact with the support platform;

[0039] The warped protruding portion of the initial electro-optical material layer is ground by a chemical mechanical polishing process until a portion of the first compressive stress layer or the first substrate is exposed, and two slope structures are simultaneously formed on the initial electro-optical material layer in a direction perpendicular to the warping direction.

[0040] Optionally, in the electro-optic material wafer chip, the length of the slope structure of the initial electro-optic material layer is positively correlated with the radius of curvature of the first substrate or the support platform;

[0041] The length of the slope structure of the initial electro-optical material layer is negatively correlated with the depth of entering the first compressive stress layer during grinding. The deeper the depth of entering the first compressive stress layer during grinding, the shorter the slope length of the initial electro-optical material layer.

[0042] Optionally, the step of removing the first substrate and the first compressive stress layer in the electro-optical material wafer and using the remaining initial electro-optical material layer as the electro-optical material layer includes:

[0043] Adsorbing the electro-optic material wafer chip by using a transfer device, wherein the transfer device is in contact with a side of the initial electro-optic material layer facing away from the first compressive stress layer;

[0044] Immersing the electro-optic material wafer in an etching solution to remove the first compressive stress layer, separate the initial electro-optic material layer from the first substrate, restore the initial electro-optic material layer to be flat, and use the remaining initial electro-optic material layer as the electro-optic material layer;

[0045] Cleaning the electro-optical material layer.

[0046] Optionally, the step of removing the first substrate and the compressive stress layer in the electro-optical material wafer and using the remaining initial electro-optical material layer as the electro-optical material layer includes:

[0047] Adsorbing the electro-optic material wafer chip by using a transfer device, wherein the transfer device is in contact with a side of the initial electro-optic material layer facing away from the first compressive stress layer;

[0048] Immersing the electro-optic material wafer chip in an organic solvent, removing the sacrificial layer, separating the initial electro-optic material layer from the compressive stress layer and the first substrate, restoring the initial electro-optic material layer to be flat, and using the remaining initial electro-optic material layer as the electro-optic material layer;

[0049] Cleaning the electro-optical material layer.

[0050] Optionally, the step of bonding the electro-optical material layer to a surface of the bonding medium layer on a side facing away from the waveguide core comprises:

[0051] The electro-optic material layer is bonded to the surface of the bonding medium layer on one side facing away from the waveguide core by using a transfer device; wherein the electro-optic material layer corresponds to the waveguide core; and the slope surface of the electro-optic material layer faces away from the waveguide core.

[0052] Optionally, the radius of curvature of the warped electro-optical material wafer after thinning is controlled by the stress of the first compressive stress layer, the thickness of the first compressive stress layer and the thickness of the first substrate after thinning.

[0053] Optionally, the electro-optical material wafer further includes a second compressive stress layer, which is located on a surface of the first substrate facing away from the first compressive stress layer; the second compressive stress layer is used to reduce or balance the compressive stress of the first compressive stress layer;

[0054] Before the step of thinning the side of the first substrate facing away from the first compressive stress layer, the method further includes:

[0055] The second compressive stress layer is removed.

[0056] Optionally, the method of sequentially forming a lower cladding layer, a waveguide core, and a bonding dielectric layer on a surface of one side of the second substrate includes:

[0057] forming a lower cladding layer on a surface of one side of the second substrate;

[0058] A waveguide core and a bonding dielectric layer are formed on a surface of the lower cladding layer facing away from the second substrate, and the bonding dielectric layer covers a surface of the waveguide core facing away from the second substrate and a side surface of the waveguide core.

[0059] The technical solution of the present invention has the following advantages:

[0060] (1) The method for preparing an electro-optical modulation device provided by the present invention, on the one hand, by thinning the side of the first substrate facing away from the first compressive stress layer, the electro-optical material wafer is warped to make the initial electro-optical material layer convex, and the warped convex part of the initial electro-optical material layer is ground, so that a smooth, thickness-gradient slope structure can be formed on the initial electro-optical material layer, and the slope and size of the slope structure can be controlled by controlling the curvature radius of the warping and the grinding depth, so that the finally formed electro-optical material layer has a slope structure with a small surface roughness and an easily controllable slope. This scheme uses the warping + grinding process to form a smooth, thickness-gradient slope structure on the initial electro-optical material layer. The slope structure has a simple process, high process efficiency, and a high utilization rate of electro-optical materials. The number of etching times of the electro-optical material layer in the preparation process is reduced, the preparation process flow is simplified, the process difficulty is reduced, and the process efficiency and the utilization rate of the electro-optical material are improved; on the other hand, the slope structure of the electro-optical material layer is located on both sides of the length direction of the waveguide core, which can reduce the light field transition loss of the electro-optical modulator. At the same time, the slope structure preparation method in this scheme has low requirements for alignment accuracy, the surface roughness of the formed slope structure is small, and the slope is easy to control, and there is no absorption loss caused by additional materials, so that the electro-optical modulator has a lower transition loss. Therefore, the preparation method of the electro-optical modulator provided by the present invention can improve the process efficiency and the utilization rate of the electro-optical material, simplify the process flow, reduce the process difficulty, and effectively reduce the light field transition loss of the electro-optical modulator.

[0061] (2) The present invention provides a method for preparing an electro-optical modulation device, wherein an electro-optical material wafer comprises a stacked first substrate, a plurality of mutually parallel first compressive stress layers and a plurality of mutually parallel initial electro-optical material layers in sequence; the length direction of the plurality of first compressive stress layers is the same as the length direction of the plurality of initial electro-optical material layers; each initial electro-optical material layer is located on at least one first compressive stress layer, so that the electro-optical material wafer is warped along the length direction of each initial electro-optical material layer; and during grinding, the length direction of the formed strip groove is perpendicular to the length direction of the plurality of initial electro-optical material layers, so that the direction of the slope structure and the relative relationship between the crystal directions of the electro-optical material layers can be controlled according to the relative relationship between the length directions of the plurality of first compressive stress layers and the crystal directions of the plurality of initial electro-optical material layers, so as to ensure that the electro-optical modulator has a high electro-optical modulation efficiency and further reduce the transition loss between the waveguide core and the waveguide core-electro-optical material hybrid waveguide.

[0062] (3) In the preparation method of the electro-optical modulation device provided by the present invention, in the step of providing an electro-optical material wafer, a first compressive stress layer and an initial electro-optical material layer are first formed in sequence on a first substrate, and then the first compressive stress layer and the initial electro-optical material layer are patterned to form multiple parallel columns of first compressive stress layers and multiple parallel columns of initial electro-optical material layers. Only one patterning process is required, which can simplify the process flow, and the direction of the slope structure and the relative relationship between the crystal directions of the electro-optical material layers can be controlled according to the relative relationship between the length directions of the multiple columns of first compressive stress layers and the crystal directions of the multiple columns of initial electro-optical material layers, thereby ensuring that the electro-optical modulator has a higher electro-optical modulation efficiency.

[0063] (4) In the preparation method of the electro-optical modulator provided by the present invention, in the step of providing an electro-optical material wafer, a plurality of mutually parallel columns of first compressive stress layers are first formed, and then an initial electro-optical material layer is formed on the surface of the plurality of columns of first compressive stress layers facing away from the first substrate, and the initial electro-optical material layer is patterned to form a plurality of mutually parallel columns of initial electro-optical material layers. Only one patterning process is required for the initial electro-optical material layer, and electro-optical material layers of different sizes can be obtained as required. At the same time, the initial electro-optical material layer is formed on the plurality of columns of first compressive stress layers, so that the relative relationship between the crystal orientation of the initial electro-optical material layer and the length direction of the plurality of columns of first compressive stress layers can be better controlled, thereby better controlling the relative relationship between the direction of the slope structure and the crystal orientation of the electro-optical material layer, thereby ensuring that the electro-optical modulator has a higher electro-optical modulation efficiency. In addition, in the method for preparing the electro-optical modulation device provided in this embodiment, multiple columns of first compressive stress layers can correspond under each column of initial electro-optical material layer. When the first compressive stress layer is removed by wet etching and the initial electro-optical material layer is separated from the first substrate, the etching time can be shortened, the process efficiency can be improved, and the etching damage that the etching solution may cause to the initial electro-optical material layer can be reduced.

[0064] (5) In the method for preparing the electro-optical modulation device provided by the present invention, in the step of forming an initial electro-optical material layer on the surface of the side of the multiple columns of first compressive stress layers facing away from the first substrate, the crystal orientation of the initial electro-optical material layer is parallel, perpendicular, or at a certain angle to the length direction of the multiple columns of compressive stress layers. This can make the direction of the formed slope structure parallel, perpendicular, or at a certain angle to the crystal orientation of the electro-optical material layer, which is beneficial to ensure that the electro-optical modulator has a higher electro-optical modulation efficiency.

[0065] (6) The preparation method of the electro-optical modulation device provided by the present invention utilizes a transfer device to absorb a small piece of electro-optical material wafer, the transfer device contacts the side of the initial electro-optical material layer facing away from the first compressive stress layer, the small piece of electro-optical material wafer is immersed in an etching solution, the first compressive stress layer is removed, the initial electro-optical material layer is separated from the first substrate, the initial electro-optical material layer is restored to be flat, and the remaining initial electro-optical material layer is used as the electro-optical material layer. The electro-optical material layer is extracted from the small piece of electro-optical material wafer through a wet process. At the same time, the use of the transfer device can facilitate the subsequent bonding of the electro-optical material to the bonding medium layer, which can simplify the process flow and improve the process efficiency.

[0066] (7) The preparation method of the electro-optical modulator provided by the present invention uses a transfer device to bond the electro-optical material layer to the surface of the bonding medium layer on the side facing away from the waveguide core, wherein the electro-optical material layer corresponds to the waveguide core, and the slope surface of the electro-optical material layer faces away from the waveguide core; the slope surface structure makes the edge thickness of the electro-optical material layer gradually decrease from the inside to the outside, thereby making the transition between the waveguide core and the waveguide core-electro-optical material composite waveguide smoother, which can reduce the optical field transition loss of the electro-optical modulator.

[0067] (8) The preparation method of the electro-optical modulation device provided by the present invention utilizes a transfer device to absorb a small piece of electro-optical material wafer, the transfer device contacts the side of the initial electro-optical material layer facing away from the first compressive stress layer, wherein a plurality of columns of first compressive stress layers correspond to each column of the initial electro-optical material layer, the small piece of electro-optical material wafer is immersed in an etching solution, the first compressive stress layer is removed, and the initial electro-optical material layer is separated from the first substrate, which can shorten the time required for removing the first compressive stress layer, improve process efficiency, and reduce the etching damage that the etching solution may cause to the initial electro-optical material layer.

[0068] (9) The method for preparing the electro-optical modulation device provided by the present invention utilizes a transfer device to absorb a small piece of electro-optical material wafer, and the transfer device contacts the side of the initial electro-optical material layer facing away from the first compressive stress layer, wherein a sacrificial layer is arranged between the initial electro-optical material layer and the first compressive stress layer. The initial electro-optical material layer can be separated from the first compressive stress layer / first substrate by immersing the small piece of electro-optical material wafer in an organic solvent to remove the sacrificial layer, without using an etching solution to remove the first compressive stress layer to separate the initial electro-optical material layer and the first substrate, thereby avoiding possible etching damage to the initial electro-optical material layer caused by the etching solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0070] Figure 1 A schematic diagram of a process for preparing an electro-optical modulation device according to an embodiment of the present invention;

[0071] Figure 2 A schematic flow chart of another method for preparing an electro-optical modulation device according to an embodiment of the present invention;

[0072] Figure 3 A schematic diagram of a process for forming an electro-optical material wafer according to an embodiment of the present invention;

[0073] Figure 4 A schematic diagram of a process of forming another electro-optical material wafer according to an embodiment of the present invention;

[0074] Figure 5 A schematic diagram of a process of forming another electro-optical material wafer according to an embodiment of the present invention;

[0075] Figure 6 , Figure 7 , Figure 8 , Fig. 9A , Fig. 9B and Fig. 9C It is a structural schematic diagram of each process of a method for forming an electro-optical material wafer according to an embodiment of the present invention;

[0076] Fig. 9A , Fig. 9B and Fig. 9C This is a schematic structural diagram of a completely strip-shaped first compressive stress layer according to an embodiment of the present invention;

[0077] Fig. 10A and Fig. 10B This is a schematic structural diagram of a ridge-shaped strip-shaped first compressive stress layer according to an embodiment of the present invention;

[0078] Fig.11A and Fig. 11B It is a structural schematic diagram of a step of thinning a first substrate in a method for preparing an electro-optical modulation device according to an embodiment of the present invention;

[0079] Fig.12 , Fig.13A and Fig. 13BIt is a structural schematic diagram of a step of grinding a warped raised portion of an initial electro-optic material layer in a method for preparing an electro-optic modulation device according to an embodiment of the present invention;

[0080] Fig.14 A schematic structural diagram of an electro-optic material wafer chip in a method for preparing an electro-optic modulation device according to an embodiment of the present invention;

[0081] Fig.15 It is a structural schematic diagram of a step of removing a first substrate and a first compressive stress layer in a method for preparing an electro-optical modulation device according to an embodiment of the present invention;

[0082] Fig.16 A schematic structural diagram of an electro-optic material layer in a method for preparing an electro-optic modulation device according to an embodiment of the present invention;

[0083] Fig.17 , Fig.18A , Fig.18B and Fig. 18C It is a structural schematic diagram of the step of bonding an electro-optic material layer to a bonding medium layer in a method for preparing an electro-optic modulation device according to an embodiment of the present invention;

[0084] Fig.19A , Fig.19B and Fig.19C It is a structural schematic diagram of the step of forming electrodes and an upper cladding layer in a method for preparing an electro-optical modulation device according to an embodiment of the present invention;

[0085] Fig. 20 , Fig.21 , Fig.22A and Fig. 22B It is a structural schematic diagram of each process of another method for forming an electro-optical material wafer according to an embodiment of the present invention;

[0086] Fig.23A , Fig. 23B and Fig.23C It is a structural schematic diagram of each process of another method for forming an electro-optical material wafer according to an embodiment of the present invention;

[0087] Fig.24 The present invention is a schematic diagram of a specific process of a method for preparing an electro-optical modulation device according to an embodiment of the present invention.

[0088] Description of reference numerals:

[0089] 11-first substrate; 12-first compressive stress layer; 13-initial electro-optic material layer; 130-electro-optic material layer; 14-sacrificial layer; 21-second substrate; 22-lower cladding; 23-waveguide core; 24-bonding medium layer; 26-electrode; 27-upper cladding; 100-electro-optic material substrate; 200-support table; 300-polishing pad; 400-transfer device; 500-etching liquid; 600-an electro-optic modulation device. DETAILED DESCRIPTION

[0090] In the prior art, one of the problems faced by heterogeneous integration of lithium niobate and silicon nitride waveguide platforms is the low-loss transition of the optical field between the silicon nitride waveguide and the silicon nitride-lithium niobate composite waveguide. The solutions for realizing the light field transition between lithium niobate and silicon nitride waveguide in the existing technical solutions all have certain defects: Solution 1: Integrate lithium niobate with a two-dimensional conical structure into a silicon nitride platform through a transfer process to realize the light field transition, but this solution requires that the two-dimensional conical structure and the silicon nitride optical waveguide core have a high alignment accuracy, which increases the process difficulty; Solution 2: Perform multiple dry etching on lithium niobate so that lithium niobate forms multiple steps along both sides of the silicon nitride waveguide core to realize the light field transition. Since dry etching of lithium niobate is relatively difficult, the process difficulty is high, and there is a potential contamination problem that will lead to incompatibility with CMOS process equipment; Solution 3: Use sputtering to form a mask with a gradient thickness on the surface of the film, and use chemical mechanical polishing (CMP) to make the lithium niobate film have a gradient thickness. However, this solution has the problems of low mask production efficiency, difficulty in forming multiple gradient thickness masks on the same substrate, or the mask size (resulting in the size of the gradient thickness film) cannot be accurately controlled.

[0091] In addition, there is another solution that uses grayscale lithography and dry etching to form a slope structure on lithium niobate or a material with a refractive index similar to that of lithium niobate to achieve light field transition. However, it is difficult to form a gradually changing slope structure on a thinner (several hundred nanometers thick) electro-optical material film using grayscale lithography + etching process: first, grayscale lithography requires a costly mask or a complex encoding process; second, dry etching of lithium niobate is relatively difficult, and it is not easy to control the thickness and surface roughness. Third, when forming a slope structure on lithium niobate, its dry etching is usually based on physical etching (the etching selectivity for photoresist, optoelectronic materials, and waveguide substrate surface materials is relatively low), which can easily cause damage to the waveguide substrate itself; fourth, when forming a slope structure on other materials with a refractive index similar to that of lithium niobate, the refractive index and thickness deviations of other materials and optoelectronic materials will also cause light scattering and increase the light transition loss.

[0092] In order to solve the problem that the transfer of two-dimensional conical structure lithium niobate in the existing preparation method of electro-optical modulation device is difficult, multi-step lithium niobate dry etching is required, and the thickness gradient mask is difficult to accurately control, resulting in high light field transition loss between silicon nitride waveguide and silicon nitride-lithium niobate composite waveguide, and low light field transition loss between silicon nitride waveguide and silicon nitride-lithium niobate composite waveguide is achieved, the present invention provides a preparation method of electro-optical modulation device, comprising: providing an electro-optical material wafer, the electro-optical material wafer sequentially comprising a stacked first substrate, a first compressive stress layer and an initial electro-optical material layer; thinning the side of the first substrate facing away from the first compressive stress layer, and at the same time causing the electro-optical material wafer to warp and bulge toward the side of the initial electro-optical material layer; fixing the first substrate, grinding the warped bulging part of the initial electro-optical material layer until part of the first compressive stress layer or the first substrate is exposed, and forming a plurality of strip grooves with slope structures on both sides; the strip grooves At least penetrate the initial electro-optical material layer and penetrate into the first compressive stress layer in the depth direction; cut the ground electro-optical material wafer to form electro-optical material wafer chips; the electro-optical material wafer chips include part of the first substrate, part of the first compressive stress layer and part of the initial electro-optical material layer with slope structures on both sides; remove the first substrate and the first compressive stress layer in the electro-optical material wafer chips, and use the remaining initial electro-optical material layer as the electro-optical material layer; provide a second substrate, and sequentially form a lower cladding layer, a waveguide core and a bonding medium layer on one side surface of the second substrate, the bonding medium layer covers the side surface of the waveguide core facing away from the second substrate and the side surface of the waveguide core; bond the electro-optical material layer to the side surface of the bonding medium layer facing away from the waveguide core; wherein the electro-optical material layer corresponds to the waveguide core; the slope structures are located on both sides of the length direction of the waveguide core; electrodes are formed on the side surface of the electro-optical material layer facing away from the bonding medium layer, and the electrodes are located at corresponding positions on both sides of the waveguide core.

[0093] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the description of the present invention, it should be noted that the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0094] Example 1

[0095] like Figure 1 As shown, this embodiment provides a method for preparing an electro-optic modulation device, including steps S101 to S108.

[0096] S101 , providing an electro-optic material wafer, wherein the electro-optic material wafer includes a first substrate 11 , a first compressive stress layer 12 , and an initial electro-optic material layer 13 stacked in sequence.

[0097] In specific implementation, the structure of the electro-optical material thin film wafer is as follows: Figure 8 As shown, the material of the first compressive stress layer 12 can be silicon dioxide, and the thickness of the first compressive stress layer 12 is 0.5μm to 10μm; the material of the initial electro-optical material layer 13 can be a single crystal film of lithium niobate, lithium tantalate, barium titanate and the like, and the thickness of the initial electro-optical material layer 13 is 100nm to 500nm.

[0098] S102, thinning the side of the first substrate 11 facing away from the first compressive stress layer 12, and causing the electro-optical material wafer to warp and bulge toward the initial electro-optical material layer 13, such as Fig. 11B shown.

[0099] In a specific implementation, the thickness of the thinned first substrate is 10 μm to 300 μm.

[0100] S103, fixing the first substrate 11, grinding the warped convex part of the initial electro-optical material layer 13 until part of the first compressive stress layer 12 or the first substrate 11 is exposed, forming a plurality of strip-shaped grooves with slope structures on both sides, such as Fig.12 As shown; the strip-shaped groove at least penetrates the initial electro-optical material layer 13 and penetrates the first compressive stress layer 12 in the depth direction, such as Fig.13A shown.

[0101] S104, cutting the ground electro-optical material wafer to form electro-optical material wafer chips; the electro-optical material wafer chips include a portion of the first substrate 11, a portion of the first compressive stress layer 12 and a portion of the initial electro-optical material layer 13 with slope structures on both sides, such as Fig.14 shown.

[0102] S105, removing the first substrate 11 and the first compressive stress layer 12 in the electro-optic material wafer, and the remaining initial electro-optic material layer 13 is used as the electro-optic material layer 130, such as Figure 15-16 shown.

[0103] S106, providing a second substrate 21, and sequentially forming a lower cladding layer 22, a waveguide core 23, and a bonding dielectric layer 24 on a side surface of the second substrate 21, wherein the bonding dielectric layer 24 covers a side surface of the waveguide core 23 facing away from the second substrate 21 and a side surface of the waveguide core 23, such as Fig.17 shown.

[0104] S107, bonding the electro-optic material layer 130 to the surface of the bonding medium layer 24 facing away from the waveguide core 23; wherein the electro-optic material layer 130 corresponds to the waveguide core 23; the slope structure is located on both sides of the length direction of the waveguide core 23, such as Figures 18A to 18C shown.

[0105] S108, forming electrodes 26 on the surface of the electro-optic material layer 130 facing away from the bonding medium layer 24, and the electrodes 26 are located at corresponding positions on both sides of the waveguide core, such as Figures 19A to 19C shown.

[0106] In specific implementation, the material of the electrode 26 can be a conductive material such as Au, Al, Cu, W, ITO, etc. The distance between the two electrodes 26 is preferably 4μm to 10μm, the thickness of the electrode 26 is 0.3μm to 1.2μm, and the length direction of the electrode 26 is consistent with the length direction of the waveguide core 23. Fig.19A is a top view of an electro-optic modulation device 600, Fig.19B for Fig.19A The cross-sectional view at position AA, Fig.19C for Fig.19A Side view of BB in mid position.

[0107] The preparation method of the electro-optic modulation device provided in this embodiment, on the one hand, by thinning the side of the first substrate facing away from the first compressive stress layer, the electro-optic material wafer generates a warp that makes the initial electro-optic material layer convex, and the warped convex part of the initial electro-optic material layer is ground, so that a smooth, thickness-gradient slope structure can be formed on the initial electro-optic material layer, and the slope and size of the slope structure can be controlled by controlling the curvature radius of the warp and the grinding depth, so that the finally formed electro-optic material layer has a slope structure with a small surface roughness and an easily controllable slope. This solution uses the warping + grinding process to form a smooth, thickness-gradient slope structure on the initial electro-optic material layer. The slope structure has a simple process, high process efficiency, and a high utilization rate of electro-optical materials. It reduces the number of etching times of the electro-optical material layer in the preparation process, simplifies the preparation process flow, reduces the process difficulty, and improves the process efficiency and the utilization rate of the electro-optical material. On the other hand, the slope structure of the electro-optical material layer is located on both sides of the length direction of the waveguide core, which can reduce the light field transition loss of the electro-optical modulator. At the same time, the slope structure preparation method in this scheme has low requirements for alignment accuracy, and the surface roughness of the formed slope structure is small and the slope is easy to control, and there is no absorption loss caused by additional materials, so that the electro-optical modulator has a lower transition loss. Therefore, the preparation method of the electro-optical modulator provided in this embodiment can improve the process efficiency and the utilization rate of the electro-optical material, simplify the process flow, reduce the process difficulty, and effectively reduce the light field transition loss of the electro-optical modulator.

[0108] Further, in some embodiments, in the step of providing an electro-optic material wafer, the electro-optic material wafer sequentially includes a stacked first substrate 11, a plurality of mutually parallel columns of first compressive stress layers 12, and a plurality of mutually parallel columns of initial electro-optic material layers 13; the length direction of the plurality of columns of first compressive stress layers 12 is the same as the length direction of the plurality of columns of initial electro-optic material layers 13; each column of initial electro-optic material layers 13 is located on at least one column of first compressive stress layers 12;

[0109] In the step of thinning the side of the first substrate 11 facing away from the first compressive stress layer 12 and causing the electro-optic material wafer to warp and bulge toward the side of the initial electro-optic material layer 13, the electro-optic material wafer is warped along the length direction of each column of the initial electro-optic material layer 13;

[0110] Fix the first substrate 11 and grind the warped raised portion of the initial electro-optical material layer 13 until a portion of the first compressive stress layer 12 or the first substrate 11 is exposed, thereby forming a plurality of strip grooves having slope structures on both sides, wherein the length direction of the strip grooves is perpendicular to the length direction of the plurality of columns of the initial electro-optical material layer 13.

[0111] When implementing it, Figure 2 As shown, this embodiment also provides another method for preparing an electro-optic modulation device, including steps S201 to S208.

[0112] S201, providing an electro-optic material wafer, wherein the electro-optic material wafer sequentially comprises a stacked first substrate 11, a plurality of mutually parallel columns of first compressive stress layers 12, and a plurality of mutually parallel columns of initial electro-optic material layers 13; the length direction of the plurality of columns of first compressive stress layers 12 is the same as the length direction of the plurality of columns of initial electro-optic material layers 13; each column of initial electro-optic material layers 13 is located on at least one column of first compressive stress layers 12, such as Figures 9A to 9C or Figure 10A to Figure 10B shown.

[0113] S202, thinning the side of the first substrate 11 facing away from the first compressive stress layer 12, and causing the electro-optic material wafer to warp and bulge toward the initial electro-optic material layer 13; the electro-optic material wafer is warped along the length direction of each column of the initial electro-optic material layer 13, such as Fig.11A and Fig. 11B shown.

[0114] In a specific implementation, the electro-optic material wafer is warped along the length direction of each column of the initial electro-optic material layer 13. Fig.11A for Fig. 9A The cross-sectional view at position ① in the top view of the electro-optical material wafer, that is, the width direction of each column of the initial electro-optical material layer 13, the warping of the electro-optical material wafer is relatively small; Fig. 11B for Fig. 9A In the cross-sectional view at position ② in the top view of the electro-optic material wafer, that is, in the length direction of each column of the initial electro-optic material layer 13 , the electro-optic material wafer is warped greatly and bulges toward one side of the initial electro-optic material layer 13 .

[0115] S203, fixing the first substrate 11, grinding the warped convex part of the initial electro-optical material layer 13 until part of the first compressive stress layer 12 or the first substrate 11 is exposed, forming a plurality of strip-shaped grooves with slope structures on both sides, such as Fig.12As shown; the strip groove at least penetrates the initial electro-optic material layer 13 and penetrates into the first compressive stress layer 12 in the depth direction; the length direction of the strip groove is perpendicular to the length direction of the multiple columns of the initial electro-optic material layer 13, as shown Fig.13A and Fig. 13B shown.

[0116] When implementing it specifically, Fig. 13B This is a top view of the electro-optical material wafer after grinding. Fig.13A for Fig. 13B Cross-sectional view at position ② in the middle.

[0117] S204, cutting the ground electro-optical material wafer to form electro-optical material wafer chips; the electro-optical material wafer chips include a portion of the first substrate 11, a portion of the first compressive stress layer 12 and a portion of the initial electro-optical material layer 13 with slope structures on both sides, such as Fig.14 shown.

[0118] S205, removing the first substrate 11 and the first compressive stress layer 12 in the electro-optic material wafer, and the remaining initial electro-optic material layer 13 is used as the electro-optic material layer 130, such as Figure 15-16 shown.

[0119] S206, providing a second substrate 21, and sequentially forming a lower cladding layer 22, a waveguide core 23, and a bonding dielectric layer 24 on a side surface of the second substrate 21, wherein the bonding dielectric layer 24 covers a side surface of the waveguide core 23 facing away from the second substrate 21 and a side surface of the waveguide core 23, such as Fig.17 shown.

[0120] S207, bonding the electro-optic material layer 130 to the surface of the bonding medium layer 24 facing away from the waveguide core 23; wherein the electro-optic material layer 130 corresponds to the waveguide core 23; the slope structure is located on both sides of the length direction of the waveguide core 23, such as Figures 18A to 18C shown.

[0121] S208, forming electrodes 26 on the surface of the electro-optic material layer 130 facing away from the bonding medium layer 24, and the electrodes 26 are located at corresponding positions on both sides of the waveguide core, such as Figures 19A to 19C shown.

[0122] The present invention provides a method for preparing an electro-optic modulation device, wherein an electro-optic material wafer sequentially comprises a stacked first substrate, a plurality of mutually parallel first compressive stress layers and a plurality of mutually parallel initial electro-optic material layers; the length direction of the plurality of first compressive stress layers is the same as the length direction of the plurality of initial electro-optic material layers; each initial electro-optic material layer is located on at least one first compressive stress layer, so that the electro-optic material wafer forms a warp along the length direction of each initial electro-optic material layer; and during grinding, the length direction of the formed strip groove is perpendicular to the length direction of the plurality of initial electro-optic material layers, so that the relative relationship between the direction of the slope structure and the crystal direction of the electro-optic material layer can be controlled according to the relative relationship between the length direction of the plurality of first compressive stress layers and the crystal direction of the plurality of initial electro-optic material layers, so that the electro-optic modulator can be ensured to have a high electro-optic modulation efficiency, and the transition loss between the waveguide core and the waveguide core-electro-optic material hybrid waveguide can be further reduced.

[0123] Furthermore, in some embodiments, Figure 3 The present invention is a flow chart of a method for forming an electro-optical material wafer, wherein the steps of providing the electro-optical material wafer include:

[0124] S11, forming a first compressive stress layer 12 on the first substrate 11, such as Figure 6 shown.

[0125] S12, forming an initial electro-optic material layer 13 on a surface of the first compressive stress layer 12 facing away from the first substrate 11, such as Figure 8 shown.

[0126] S13, performing a patterning process on the first compressive stress layer 12 and the initial electro-optic material layer 13 to form a plurality of mutually parallel rows of the first compressive stress layer 12 and a plurality of mutually parallel rows of the initial electro-optic material layer 13, such as Figures 9A to 9C or Figure 10A to Figure 10B shown.

[0127] In the preparation method of the electro-optical modulation device provided in the present embodiment, in the step of providing an electro-optical material wafer, a first compressive stress layer and an initial electro-optical material layer are first formed in sequence on a first substrate, and then the first compressive stress layer and the initial electro-optical material layer are patterned to form multiple parallel columns of first compressive stress layers and multiple parallel columns of initial electro-optical material layers. Only one patterning process is required, which can simplify the process flow, and the relative relationship between the direction of the slope structure and the crystal direction of the electro-optical material layer can be controlled according to the relative relationship between the length directions of the multiple columns of first compressive stress layers and the crystal directions of the multiple columns of initial electro-optical material layers, thereby ensuring that the electro-optical modulator has a higher electro-optical modulation efficiency.

[0128] Furthermore, in some embodiments, Figure 4 The present invention is a flow chart of a method for forming an electro-optical material wafer, wherein the steps of providing the electro-optical material wafer include:

[0129] S21, forming a first compressive stress layer 12 on the first substrate 11, such as Fig. 20 shown.

[0130] S22, performing a patterning process on the first compressive stress layer 12 to form a plurality of parallel rows of first compressive stress layers 12, such as Fig.21 shown.

[0131] S23, forming an initial electro-optic material layer 13 on the surface of the first compressive stress layer 12 on the side facing away from the first substrate 11, such as Fig.22A shown.

[0132] S24, performing a patterning process on the initial electro-optic material layer 13 to form a plurality of parallel columns of initial electro-optic material layers 13; the length direction of the plurality of columns of first compressive stress layers 12 is the same as the length direction of the plurality of columns of initial electro-optic material layers 13; each column of initial electro-optic material layers 13 is located on at least one column of first compressive stress layers, such as Fig. 22B shown.

[0133] The preparation method of the electro-optical modulation device provided in the present embodiment provides an electro-optical material wafer. In the step of first forming a plurality of mutually parallel columns of first compressive stress layers, an initial electro-optical material layer is then formed on the surface of the plurality of columns of first compressive stress layers facing away from the first substrate. The initial electro-optical material layer is patterned to form a plurality of mutually parallel columns of initial electro-optical material layers. Only one patterning process is required for the initial electro-optical material layer, and electro-optical material layers of different sizes can be obtained as required. At the same time, the initial electro-optical material layer is formed on the plurality of columns of first compressive stress layers, so that the relative relationship between the crystal orientation of the initial electro-optical material layer and the length direction of the plurality of columns of first compressive stress layers can be better controlled, thereby better controlling the relative relationship between the direction of the slope structure and the crystal orientation of the electro-optical material layer, and ensuring that the electro-optical modulator has a higher electro-optical modulation efficiency. In addition, in the method for preparing the electro-optical modulation device provided in this embodiment, multiple columns of first compressive stress layers can correspond under each column of initial electro-optical material layer. When the first compressive stress layer is removed by wet etching and the initial electro-optical material layer is separated from the first substrate, the etching time can be shortened, the process efficiency can be improved, and the etching damage that the etching solution may cause to the initial electro-optical material layer can be reduced.

[0134] Furthermore, in some embodiments, in the step of forming the initial electro-optic material layer 13 on the surface of the multiple columns of first compressive stress layers 12 facing away from the first substrate 11 , the crystal orientation of the initial electro-optic material layer 13 is parallel, perpendicular or at a certain angle to the length direction of the multiple columns of first compressive stress layers 12 .

[0135] In specific implementation, the crystal orientation of the initial electro-optic material layer 13 can be adjusted according to actual needs to be parallel, perpendicular or at a certain angle to the length direction of the multiple columns of first compressive stress layers 12. In a specific example, the initial electro-optic material layer 13 is an X-cut lithium niobate film. To obtain higher electro-optic modulation efficiency, the Z-axis orientation of the lithium niobate film is perpendicular to the length direction of the multiple columns of first compressive stress layers 12.

[0136] In the method for preparing the electro-optical modulation device provided in the present embodiment, in the step of forming an initial electro-optical material layer on the surface of the side of the multiple columns of first compressive stress layers facing away from the first substrate, the crystal orientation of the initial electro-optical material layer is parallel, perpendicular, or at a certain angle to the length direction of the multiple columns of compressive stress layers. This allows the direction of the formed slope structure to be parallel, perpendicular, or at a certain angle to the crystal orientation of the electro-optical material layer, which is beneficial to ensuring that the electro-optical modulator has a higher electro-optical modulation efficiency.

[0137] Furthermore, in some embodiments, before the step of forming the initial electro-optical material layer 13 on the surface of the plurality of columns of first compressive stress layers 12 facing away from the first substrate 11, the step further includes:

[0138] A sacrificial layer 14 is formed on the plurality of columns of the first compressive stress layer 12; the sacrificial layer 14 covers the surface of the first compressive stress layer 12 facing away from the first substrate 11 and the side surfaces of the plurality of columns of the first compressive stress layer 12;

[0139] The step of forming an initial electro-optical material layer 13 on a surface of a plurality of columns of first compressive stress layers 12 facing away from the first substrate 11 includes:

[0140] An initial electro-optical material layer 13 is formed on a surface of the sacrificial layer 14 facing away from the first compressive stress layer 12 .

[0141] When implementing it specifically, Figure 5 The present invention is a flow chart of another method for forming an electro-optical material wafer, wherein the steps of providing the electro-optical material wafer include:

[0142] S31, forming a first compressive stress layer 12 on the first substrate 11, such as Fig. 20 As shown;

[0143] S32, performing a patterning process on the first compressive stress layer 12 to form a plurality of parallel rows of first compressive stress layers 12, such as Fig.21 As shown;

[0144] S33, forming a sacrificial layer 14 on the plurality of columns of the first compressive stress layer 12; the sacrificial layer 14 covers the surface of the first compressive stress layer 12 facing away from the first substrate 11 and the side surfaces of the plurality of columns of the first compressive stress layer 12, such as Fig.23A As shown;

[0145] S34, forming an initial electro-optic material layer 13 on a surface of the sacrificial layer 14 facing away from the first compressive stress layer 12, such as Fig. 23B As shown;

[0146] S35, performing a patterning process on the initial electro-optic material layer 13 to form a plurality of parallel columns of initial electro-optic material layers 13; the length direction of the plurality of columns of first compressive stress layers 12 is the same as the length direction of the plurality of columns of initial electro-optic material layers 13; each column of initial electro-optic material layers 13 is located on at least one column of first compressive stress layers 12, such as Fig.23C shown.

[0147] The preparation method of the electro-optic modulation device provided by the present invention provides an electro-optic material wafer. In the step of first forming a plurality of mutually parallel columns of first compressive stress layers, then forming a sacrificial layer on the plurality of columns of first compressive stress layers, forming an initial electro-optic material layer on a surface of the sacrificial layer facing away from the first compressive stress layer, and finally performing a patterning process on the initial electro-optic material layer to form a plurality of mutually parallel columns of initial electro-optic material layers. By arranging the sacrificial layer between the plurality of columns of first compressive stress layers and the initial electro-optic material layer, the initial electro-optic material layer and the first compressive stress layer / first substrate can be separated in a subsequent manner by dissolving the sacrificial layer with an organic solvent, thereby avoiding the problem that the etching solution may damage the electro-optic material layer when the first compressive stress layer is removed by wet etching to separate the initial electro-optic material layer.

[0148] Further, in some embodiments, the sacrificial layer 14 is a photoresist or a temporary bonding adhesive layer;

[0149] The thickness of the sacrificial layer 14 on the first compressive stress layer 12 is 1 μm to 5 μm.

[0150] Furthermore, in some embodiments, the step of forming the initial electro-optical material layer 13 on the surface of the first compressive stress layer 12 facing away from the first substrate 11 includes:

[0151] By means of the intelligent ion cutting process, an initial electro-optic material layer 13 is formed on the surface of the first compressive stress layer 12 facing away from the first substrate 11. Figure 7 shown.

[0152] Furthermore, in some embodiments, Figure 7-8 As shown, the intelligent ion cutting process includes:

[0153] Providing an electro-optical material substrate 100;

[0154] Ions are implanted into the electro-optic material substrate 100 to form an ion implantation damaged layer 101 and an initial electro-optic material layer 13 separated by the ion implantation damaged layer 101;

[0155] Bonding one side surface of the initial electro-optic material layer 13 of the electro-optic material substrate 100 to the side surface of the first compressive stress layer 12 facing away from the first substrate 11;

[0156] The electro-optic material substrate 100 is peeled off from the position of the ion implantation damaged layer 101 by thermal annealing, and the ion implantation damaged layer 101 is removed.

[0157] Furthermore, in some embodiments, the step of cutting the ground electro-optical material wafer to form electro-optical material wafer chips includes:

[0158] The ground electro-optic material wafer is cut along the length direction of the strip grooves and the length direction of the multiple columns of initial electro-optic material layers 13 to form electro-optic material wafer chips.

[0159] Furthermore, in some embodiments, the plurality of columns of first compressive stress layers 12 are completely strip-shaped first compressive stress layers that expose a portion of the surface of the first substrate 11 or ridge-shaped strip-shaped first compressive stress layers that do not expose the surface of the first substrate 11 .

[0160] In some embodiments, for example, Figures 9A to 9C As shown, the plurality of columns of first compressive stress layers 12 are completely strip-shaped first compressive stress layers exposing a portion of the surface of the first substrate 11 . Fig. 9A This is a top view of the first completely strip-shaped compressive stress layer. Fig. 9B for Fig. 9A The cross-sectional view at position ① in the middle. Fig. 9C for Fig. 9A Cross-sectional view at position ② in the middle.

[0161] In other embodiments, Figure 10A to Figure 10B As shown, the plurality of columns of first compressive stress layers 12 are ridge-shaped and strip-shaped first compressive stress layers that do not expose the surface of the first substrate 11 . Fig. 10A is a top view of the ridge-shaped strip-shaped first compressive stress layer. Fig. 10B for Fig. 10A Cross-sectional view at position ① in the middle.

[0162] Furthermore, in some embodiments, Fig.12 As shown, the first substrate 11 is fixed, and the warped convex part of the initial electro-optical material layer 13 is ground until a part of the first compressive stress layer 12 or the first substrate 11 is exposed, and the step of forming a plurality of strip-shaped grooves with slope structures on both sides includes:

[0163] The warped electro-optical material wafer is fixed on a support platform 200 having a cylindrical surface, wherein the side of the first substrate 11 facing away from the first compressive stress layer 12 is in contact with the support platform 200;

[0164] The warped protruding portion of the initial electro-optic material layer 13 is polished by a polishing pad 300 using a chemical mechanical polishing process until a portion of the first compressive stress layer 12 or the first substrate 11 is exposed, and two slope structures are simultaneously formed on the initial electro-optic material layer 13 in a direction perpendicular to the warping direction.

[0165] Further, in some embodiments, in the electro-optic material wafer die, the length of the slope structure of the initial electro-optic material layer 13 is positively correlated with the radius of curvature of the first substrate 11 or the support platform 200;

[0166] The length of the slope structure of the initial electro-optical material layer 13 is negatively correlated with the depth of the first compressive stress layer 12 during grinding. The deeper the depth of the first compressive stress layer 12 during grinding, the shorter the slope length of the initial electro-optical material layer 13.

[0167] In a specific implementation, the length of the slope structure can be controlled by controlling the radius of curvature of the first substrate 11 or the support platform 200 and the depth of entering the first compressive stress layer 12 during grinding.

[0168] Furthermore, in some embodiments, the ratio of the projection length of the slope structure on the horizontal plane to the thickness of the initial electro-optical material layer is 10:1 to 500:1, for example, 10:1, 100:1, 250:1, 400:1 or 500:1.

[0169] Furthermore, in some embodiments, Fig.15 As shown, the step of removing the first substrate 11 and the first compressive stress layer 12 in the electro-optical material wafer and using the remaining initial electro-optical material layer 13 as the electro-optical material layer 130 includes:

[0170] The electro-optic material wafer chip is adsorbed by the transfer device 400, and the transfer device 400 is in contact with the side of the initial electro-optic material layer 13 facing away from the first compressive stress layer 12;

[0171] Immerse the electro-optic material wafer in an etching solution 500 to remove the first compressive stress layer 12, separate the initial electro-optic material layer 13 from the first substrate 11, restore the initial electro-optic material layer 13 to be flat, and use the remaining initial electro-optic material layer 13 as the electro-optic material layer 130;

[0172] The electro-optic material layer 130 is cleaned.

[0173] In a specific implementation, the etching solution 500 is an etching solution for the first compressive stress layer, and only reacts with the first compressive stress layer 12 to dissolve the first compressive stress layer 12. After the first compressive stress layer 12 is dissolved, the initial electro-optical material layer 13 is separated from the first substrate 11, the initial electro-optical material layer 13 is restored to be flat, and the remaining initial electro-optical material layer 13 is used as the electro-optical material layer 130. The electro-optical material layer 130 has a slope structure on both sides, and the slope structure on both sides makes the edge thickness of the electro-optical material layer 130 gradually decrease from the inside to the outside to 0.

[0174] The preparation method of the electro-optical modulation device provided in this embodiment utilizes a transfer device to absorb an electro-optical material wafer chip, the transfer device contacts the side of the initial electro-optical material layer facing away from the first compressive stress layer, the electro-optical material wafer chip is immersed in an etching solution, the first compressive stress layer is removed, the initial electro-optical material layer is separated from the first substrate, the initial electro-optical material layer is restored to be flat, and the remaining initial electro-optical material layer is used as the electro-optical material layer. The electro-optical material layer is extracted from the electro-optical material wafer chip through a wet process. At the same time, the use of the transfer device can facilitate the subsequent bonding of the electro-optical material to the bonding medium layer, which can simplify the process flow and improve process efficiency.

[0175] Furthermore, in some embodiments, the step of removing the first substrate and the compressive stress layer in the electro-optical material wafer die and using the remaining initial electro-optical material layer as the electro-optical material layer includes:

[0176] Adsorbing the electro-optic material wafer chip by using a transfer device, wherein the transfer device is in contact with a side of the initial electro-optic material layer facing away from the first compressive stress layer;

[0177] Immersing the electro-optic material wafer chip in an organic solvent, removing the sacrificial layer, separating the initial electro-optic material layer from the compressive stress layer and the first substrate, restoring the initial electro-optic material layer to be flat, and using the remaining initial electro-optic material layer as the electro-optic material layer;

[0178] Cleaning the electro-optical material layer.

[0179] In the method for preparing the electro-optical modulation device provided in this embodiment, a sacrificial layer is arranged under the initial electro-optical material layer. The initial electro-optical material layer can be separated from the first compressive stress layer / first substrate by dissolving the sacrificial layer with an organic solvent, without having to use an etching solution to remove the first compressive stress layer to separate the initial electro-optical material layer and the first substrate, thereby avoiding possible etching damage to the initial electro-optical material layer caused by the etching solution.

[0180] Furthermore, in some embodiments, the step of bonding the electro-optic material layer 130 to the surface of the bonding medium layer 24 facing away from the waveguide core 23 includes:

[0181] The electro-optic material layer 130 is bonded to the surface of the bonding medium layer 24 facing away from the waveguide core 23 using a transfer device 400 ; wherein the electro-optic material layer 130 corresponds to the waveguide core 23 ; and the slope of the electro-optic material layer 130 faces away from the waveguide core 23 .

[0182] When implementing it, Figures 18A to 18C As shown, Fig.18A is a top view after the electro-optic material layer 130 is bonded to the bonding medium layer 24, Fig.18B for Fig.18A The cross-sectional view at position AA, Fig. 18C for Fig.18A Cross-sectional view at position BB.

[0183] The preparation method of the electro-optical modulation device provided in this embodiment uses a transfer device to bond the electro-optical material layer to the surface of the bonding medium layer on the side facing away from the waveguide core, wherein the electro-optical material layer corresponds to the waveguide core, and the slope surface of the electro-optical material layer faces away from the waveguide core; the slope surface structure makes the edge thickness of the electro-optical material layer gradually decrease from the inside to the outside to 0, thereby making the transition between the waveguide core and the waveguide core-electro-optical material composite waveguide smoother, which can reduce the optical field transition loss of the electro-optical modulation device.

[0184] Furthermore, in some embodiments, the radius of curvature of the warped electro-optical material wafer after thinning is controlled by the stress of the first compressive stress layer 12 , the thickness of the first compressive stress layer 12 , and the thickness of the first substrate 11 after thinning.

[0185] Further, in some embodiments, the thickness of the first compressive stress layer 12 is 0.5 μm to 10 μm, for example, 0.5 μm, 3 μm, 5 μm, 7 μm or 10 μm;

[0186] The thickness of the thinned first substrate 11 is 10 μm to 300 μm, for example, 10 μm, 100 μm, 150 μm, 220 μm or 300 μm;

[0187] The compressive stress of the first compressive stress layer 12 is -100 MPa to -2000 MPa, for example, -100 MPa, -500 MPa, -1000 MPa, -1500 MPa or -2000 MPa;

[0188] The curvature radius of the electro-optical material wafer warpage may be 0.5 m to 10 m, for example 0.5 m, 3 m, 5 m, 7 m or 10 m;

[0189] The thickness of the initial electro-optical material layer 13 is 100 nm to 500 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm or 500 nm.

[0190] Furthermore, in some embodiments, the electro-optical material wafer further includes a second compressive stress layer, which is located on a surface of the first substrate 11 facing away from the first compressive stress layer 12; the second compressive stress layer is used to reduce or balance the compressive stress of the first compressive stress layer 12;

[0191] Before the step of thinning the side of the first substrate 11 facing away from the first compressive stress layer 12, the method further includes:

[0192] The second compressive stress layer is removed.

[0193] Furthermore, in some embodiments, the method of sequentially forming the lower cladding layer 22, the waveguide core 23 and the bonding medium layer 24 on one side surface of the second substrate 21 includes:

[0194] A lower cladding layer 22 is formed on one side surface of the second substrate 21;

[0195] A waveguide core 23 and a bonding dielectric layer 24 are formed on the surface of the lower cladding layer 22 facing away from the second substrate 21 . The bonding dielectric layer 24 covers the surface of the waveguide core 23 facing away from the second substrate 21 and the side surface of the waveguide core 23 .

[0196] In specific implementation, the material of the second substrate 21 is silicon, silicon carbide, etc., the material of the lower cladding 22 is silicon dioxide, etc., the thickness of the lower cladding 22 is 4μm to 20μm, the waveguide core 23 can be silicon nitride, silicon, etc., the waveguide core 23 can be a strip waveguide, a double strip waveguide or a combination thereof, the waveguide core 23 can be straight or curved, and the width and height of the waveguide core 23 are determined according to optical requirements. The material of the bonding medium layer 24 can be inorganic or organic materials such as silicon dioxide, aluminum oxide, benzocyclobutene (BCB) and its derivatives, or a combination thereof. The thickness of the bonding medium layer 24 above the waveguide core 23 is 10nm to 300nm.

[0197] Furthermore, in some embodiments, after the electrode 26 is formed on the surface of the electro-optic material layer 130 facing away from the bonding medium layer 24, the method further includes:

[0198] An upper cladding layer 27 is formed on the surface of the bonding dielectric layer 24 facing away from the lower cladding layer 22. The upper cladding layer 27 covers the bonding dielectric layer 24, the electro-optical material layer 130 and the electrode 26. Fig.19A , Fig.19B and Fig.19C As shown;

[0199] The upper cladding layer 27 is subjected to a planarization process.

[0200] In a specific implementation, the material of the upper cladding layer 27 is silicon dioxide, and the thickness of the upper cladding layer 27 is 0-10 μm.

[0201] In some embodiments, reference Fig.24 This embodiment also provides a specific process of a method for preparing an electro-optic modulation device 600, including steps S301-S312:

[0202] S301, forming a first compressive stress layer 12 on a first substrate 11, such as Fig. 20 As shown, the material of the first compressive stress layer 12 may be silicon dioxide, and the thickness of the first compressive stress layer 12 is 0.5 μm to 10 μm.

[0203] S302, performing a patterning process on the first compressive stress layer 12 to form a plurality of parallel rows of first compressive stress layers 12, such as Fig.21 shown.

[0204] S303, through intelligent ion cutting process, such as Figure 7-8 As shown, an initial electro-optic material layer 13 is formed on the surface of the first compressive stress layer 12 on one side facing away from the first substrate 11, and the Z-axis orientation of the initial electro-optic material layer 13 is adjusted to be perpendicular to the length direction of the first compressive stress layer 12 on the multiple columns, as shown in FIG. Fig.22A Wherein, the initial electro-optical material layer 13 is an X-cut lithium niobate film.

[0205] S304, the initial electro-optic material layer 13 is patterned to form a plurality of parallel columns of initial electro-optic material layers 13; the length direction of the plurality of columns of first compressive stress layers 12 is the same as the length direction of the plurality of columns of initial electro-optic material layers 13; each column of initial electro-optic material layers 13 is located on at least one column of first compressive stress layers, such as Fig. 22B shown.

[0206] S305, thinning the side of the first substrate 11 facing away from the first compressive stress layer 12, and causing the electro-optic material wafer to warp and bulge toward the initial electro-optic material layer 13; the electro-optic material wafer is warped along the length direction of each column of the initial electro-optic material layer 13, such as Fig.11A and Fig. 11B shown.

[0207] S306, fixing the warped electro-optical material wafer on a support platform 200 having a cylindrical surface, wherein the side of the first substrate 11 facing away from the first compressive stress layer 12 is in contact with the support platform 200; grinding the warped convex part of the initial electro-optical material layer 13 by a polishing pad 300 of a chemical mechanical polishing process until a part of the first compressive stress layer 12 is exposed, forming a plurality of strip-shaped grooves with slope structures on both sides, such as Fig.12 As shown; the strip groove at least penetrates the initial electro-optic material layer 13 and penetrates into the first compressive stress layer 12 in the depth direction; the length direction of the strip groove is perpendicular to the length direction of the multiple columns of the initial electro-optic material layer 13, as shown Fig.13A and Fig. 13B shown.

[0208] S307, cutting the ground electro-optic material wafer along the length direction of the strip grooves and the length direction of the multiple columns of the initial electro-optic material layer 13 to form electro-optic material wafer chips; the electro-optic material wafer chip includes a portion of the first substrate 11, a portion of the first compressive stress layer 12 and a portion of the initial electro-optic material layer 13 with a slope structure on both sides, such as Fig.14 shown.

[0209] S308, using the transfer device 400 to absorb the electro-optic material wafer chip, the transfer device 400 is in contact with the side of the initial electro-optic material layer 13 facing away from the first compressive stress layer 12; immersing the electro-optic material wafer chip in the etching solution 500, removing the first compressive stress layer 12, separating the initial electro-optic material layer 13 from the first substrate 11, restoring the initial electro-optic material layer 13 to be flat, and the remaining initial electro-optic material layer 13 is used as the electro-optic material layer 130; cleaning the electro-optic material layer 130, such as Figure 15-16 shown.

[0210] S309, providing a second substrate 21, and sequentially forming a lower cladding layer 22, a waveguide core 23, and a bonding dielectric layer 24 on a side surface of the second substrate 21, wherein the bonding dielectric layer 24 covers a side surface of the waveguide core 23 facing away from the second substrate 21 and a side surface of the waveguide core 23, such as Fig.17 shown.

[0211] S310, using a transfer device 400 to bond the electro-optic material layer 130 to the surface of the bonding medium layer 24 facing away from the waveguide core 23; wherein the electro-optic material layer 130 corresponds to the waveguide core 23; the slope structure is located on both sides of the length direction of the waveguide core 23, such as Figures 18A to 18C shown.

[0212] S311, forming electrodes 26 on the surface of the electro-optic material layer 130 facing away from the bonding medium layer 24, and the electrodes 26 are located at corresponding positions on both sides of the waveguide core, such as Figures 19A to 19C shown.

[0213] S312, forming an upper cladding layer 27 on the surface of the bonding dielectric layer 24 facing away from the lower cladding layer 22, the upper cladding layer 27 covering the bonding dielectric layer 24, the electro-optical material layer 130 and the electrode 26; performing a planarization process on the upper cladding layer 27, such as Figures 19A to 19C shown.

[0214] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing an electro-optical modulation device, characterized in that: include: Providing an electro-optic material wafer, wherein the electro-optic material wafer sequentially comprises a first substrate, a first compressive stress layer, and an initial electro-optic material layer stacked; Thinning the first substrate on a side facing away from the first compressive stress layer, and causing the electro-optical material wafer to warp and bulge toward the initial electro-optical material layer; Fixing the first substrate, grinding the warped convex portion of the initial electro-optical material layer until a portion of the first compressive stress layer or the first substrate is exposed, forming a plurality of strip-shaped grooves with slope structures on both sides; The strip-shaped groove at least penetrates the initial electro-optical material layer and penetrates into the first compressive stress layer in the depth direction; Cutting the ground electro-optical material wafer to form electro-optical material wafer chips; The electro-optical material wafer chip comprises a portion of the first substrate, a portion of the first compressive stress layer, and a portion of the initial electro-optical material layer having slope structures on both sides; removing the first substrate and the first compressive stress layer in the electro-optical material wafer, and using the remaining initial electro-optical material layer as an electro-optical material layer; Providing a second substrate, and sequentially forming a lower cladding layer, a waveguide core, and a bonding dielectric layer on a surface of one side of the second substrate, wherein the bonding dielectric layer covers a surface of the waveguide core that is away from the second substrate and a side surface of the waveguide core; Bonding the electro-optic material layer to the surface of the bonding medium layer facing away from the waveguide core; wherein the electro-optic material layer corresponds to the waveguide core; and the slope structure is located on both sides of the length direction of the waveguide core; Electrodes are formed on a surface of the electro-optical material layer that is opposite to the bonding medium layer, and the electrodes are located at corresponding positions on both sides of the waveguide core.

2. The method for preparing an electro-optical modulation device according to claim 1, characterized in that: In the step of providing the electro-optical material wafer, the electro-optical material wafer sequentially comprises a stacked first substrate, a plurality of mutually parallel columns of first compressive stress layers, and a plurality of mutually parallel columns of initial electro-optical material layers; the length direction of the plurality of columns of the first compressive stress layers is the same as the length direction of the plurality of columns of the initial electro-optical material layers; each column of the initial electro-optical material layers is located on at least one column of the first compressive stress layers; In the step of thinning the side of the first substrate facing away from the first compressive stress layer and causing the electro-optical material wafer to warp and bulge toward the side of the initial electro-optical material layer, the electro-optical material wafer is warped along the length direction of each column of the initial electro-optical material layer; In the step of fixing the first substrate and grinding the warped raised portion of the initial electro-optical material layer until a portion of the first compressive stress layer or the first substrate is exposed to form a plurality of strip grooves with slope structures on both sides, the length direction of the strip grooves is perpendicular to the length direction of the plurality of columns of the initial electro-optical material layer.

3. The method for preparing an electro-optical modulation device according to claim 2, characterized in that: The step of providing an electro-optical material wafer comprises: forming a first compressive stress layer on a first substrate; forming an initial electro-optical material layer on a surface of the first compressive stress layer facing away from the first substrate; The first compressive stress layer and the initial electro-optical material layer are subjected to a patterning process to form a plurality of mutually parallel columns of the first compressive stress layer and a plurality of mutually parallel columns of the initial electro-optical material layer.

4. The method for preparing an electro-optical modulation device according to claim 2, characterized in that: The step of providing an electro-optical material wafer comprises: forming a first compressive stress layer on a first substrate; Performing a patterning process on the first compressive stress layer to form a plurality of mutually parallel rows of the first compressive stress layers; forming an initial electro-optical material layer on a surface of a plurality of columns of the first compressive stress layers facing away from the first substrate; The initial electro-optic material layer is patterned to form a plurality of parallel columns of the initial electro-optic material layer; the length direction of the plurality of columns of the first compressive stress layer is the same as the length direction of the plurality of columns of the initial electro-optic material layer; each column of the initial electro-optic material layer is located on at least one column of the first compressive stress layer.

5. The method for preparing an electro-optical modulation device according to claim 4, characterized in that: In the step of forming an initial electro-optic material layer on the surface of the first compressive stress layers of the plurality of columns facing away from the first substrate, the crystal direction of the initial electro-optic material layer is parallel, perpendicular or at a certain angle to the length direction of the compressive stress layers of the plurality of columns.

6. The method for preparing an electro-optical modulation device according to claim 4, characterized in that: Before the step of forming an initial electro-optical material layer on the surface of the first compressive stress layer on one side facing away from the first substrate, the step further includes: forming a sacrificial layer on the plurality of columns of the first compressive stress layers; the sacrificial layer covers the surface of the first compressive stress layer facing away from the first substrate and the side surfaces of the plurality of columns of the first compressive stress layers; The step of forming an initial electro-optical material layer on a surface of a plurality of columns of the first compressive stress layers facing away from the first substrate comprises: An initial electro-optical material layer is formed on a surface of the sacrificial layer facing away from the first compressive stress layer.

7. The method for preparing an electro-optical modulation device according to claim 6, characterized in that: The sacrificial layer is a photoresist or a temporary bonding adhesive layer; The thickness of the sacrificial layer above the first compressive stress layer is 1 μm to 5 μm.

8. The method for preparing an electro-optical modulation device according to claim 1, characterized in that: The step of cutting the ground electro-optical material wafer to form electro-optical material wafer chips includes: The electro-optic material wafer after grinding is cut along the length direction of the strip-shaped grooves and the length direction of the multiple columns of the initial electro-optic material layers to form electro-optic material wafer chips.

9. The method for preparing an electro-optical modulation device according to claim 2, characterized in that: The plurality of columns of the first compressive stress layers are completely strip-shaped first compressive stress layers that partially expose the surface of the first substrate or ridge-shaped strip-shaped first compressive stress layers that do not expose the surface of the first substrate.

10. The method for preparing an electro-optical modulation device according to claim 1, characterized in that: The step of fixing the first substrate, grinding the warped raised portion of the initial electro-optical material layer until a portion of the first compressive stress layer or the first substrate is exposed, and forming a plurality of strip-shaped grooves with slope structures on both sides includes: Fixing the warped electro-optical material wafer on a support platform having a cylindrical surface, wherein a side of the first substrate facing away from the first compressive stress layer is in contact with the support platform; The warped protruding portion of the initial electro-optical material layer is ground by a chemical mechanical polishing process until a portion of the first compressive stress layer or the first substrate is exposed, and two slope structures are simultaneously formed on the initial electro-optical material layer in a direction perpendicular to the warping direction.

11. The method for preparing an electro-optical modulation device according to claim 10, characterized in that: In the electro-optical material wafer, the length of the slope structure of the initial electro-optical material layer is positively correlated with the curvature radius of the first substrate or the support platform; The length of the slope structure of the initial electro-optical material layer is negatively correlated with the depth of entering the first compressive stress layer during grinding. The deeper the depth of entering the first compressive stress layer during grinding, the shorter the slope length of the initial electro-optical material layer.

12. The method for preparing an electro-optical modulation device according to claim 1, characterized in that: The step of removing the first substrate and the compressive stress layer in the electro-optical material wafer and using the remaining initial electro-optical material layer as the electro-optical material layer comprises: Adsorbing the electro-optical material wafer chip by using a transfer device, wherein the transfer device is in contact with a side of the initial electro-optical material layer facing away from the first compressive stress layer; Immersing the electro-optical material wafer in an etching solution to remove the compressive stress layer, separate the initial electro-optical material layer from the first substrate, restore the initial electro-optical material layer to be flat, and use the remaining initial electro-optical material layer as the electro-optical material layer; The electro-optical material layer is cleaned.

13. The method for preparing an electro-optical modulation device according to claim 6, characterized in that: The step of removing the first substrate and the compressive stress layer in the electro-optical material wafer and using the remaining initial electro-optical material layer as the electro-optical material layer comprises: Adsorbing the electro-optical material wafer chip by using a transfer device, wherein the transfer device is in contact with a side of the initial electro-optical material layer facing away from the first compressive stress layer; Immersing the electro-optic material wafer chip in an organic solvent, removing the sacrificial layer, separating the initial electro-optic material layer from the compressive stress layer and the first substrate, restoring the initial electro-optic material layer to be flat, and using the remaining initial electro-optic material layer as the electro-optic material layer; The electro-optical material layer is cleaned.

14. The method for preparing an electro-optical modulation device according to claim 12 or 13, characterized in that: The step of bonding the electro-optical material layer to a surface of the bonding medium layer facing away from the waveguide core comprises: The electro-optic material layer is bonded to the surface of the bonding medium layer facing away from the waveguide core using the transfer device; wherein the electro-optic material layer corresponds to the waveguide core; and the slope of the electro-optic material layer faces away from the waveguide core.

15. The method for preparing an electro-optical modulation device according to claim 1, characterized in that: The curvature radius of the warpage of the electro-optical material wafer after thinning is controlled by the stress of the first compressive stress layer, the thickness of the first compressive stress layer and the thickness of the first substrate after thinning.

16. The method for preparing an electro-optical modulation device according to claim 1, characterized in that: The electro-optical material wafer further includes a second compressive stress layer, which is located on a surface of the first substrate facing away from the first compressive stress layer; the second compressive stress layer is used to reduce or balance the compressive stress of the first compressive stress layer; Before the step of thinning the side of the first substrate facing away from the first compressive stress layer, the method further includes: The second compressive stress layer is removed.

17. The method for preparing an electro-optical modulation device according to claim 1, characterized in that: The method of sequentially forming a lower cladding layer, a waveguide core and a bonding medium layer on a surface of one side of the second substrate comprises: forming the lower cladding layer on a surface of one side of the second substrate; A waveguide core and a bonding dielectric layer are formed on a surface of the lower cladding layer facing away from the second substrate, and the bonding dielectric layer covers a surface of the waveguide core facing away from the second substrate and a side surface of the waveguide core.

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