A method for fabricating an electro-optic modulating device

Abstract

The application relates to a preparation method of an electro-optical modulation device. The preparation method comprises the following steps: thinning a first substrate of an electro-optical material wafer from a side opposite to a first compressive stress layer, so that the electro-optical material wafer is warped and protrudes from a side of an initial electro-optical material layer; grinding the warped protruding part of the initial electro-optical material layer, so that a plurality of strip-shaped grooves with slope surface structures are formed on two sides of the initial electro-optical material layer; the strip-shaped grooves at least penetrate the initial electro-optical material layer in a depth direction; the electro-optical material wafer is cut and the first substrate and the compressive stress layer are removed, and the remaining initial electro-optical material layer is used as an electro-optical material layer; and the electro-optical material layer is bonded to a surface of a bonding medium layer opposite to a waveguide core. The electro-optical material layer corresponds to the waveguide core, and the slope surface structures are located on two sides of the waveguide core in a length direction. The preparation method can avoid or reduce etching process on the electro-optical material layer, improve process efficiency and utilization rate of the electro-optical material, simplify a process flow, and effectively reduce optical field transition loss of the electro-optical modulation device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and particularly relates to a preparation method of an electro-optical modulation device. BACKGROUND

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

[0003] One of the problems faced by the heterogeneous integration of lithium niobate and silicon nitride waveguide platform is the low-loss transition of the optical field between the silicon nitride waveguide and the silicon nitride-lithium niobate composite waveguide. The existing technical solutions for realizing the transition of the optical field between lithium niobate and silicon nitride waveguide all have certain defects: scheme one: a two-dimensional tapered structure of lithium niobate is integrated into the silicon nitride platform by a transfer process to realize the transition of the optical field, but this scheme requires high alignment accuracy between the two-dimensional tapered structure and the silicon nitride optical waveguide core, increasing the process difficulty; scheme two: lithium niobate is etched multiple times to form multiple steps on both sides of the silicon nitride waveguide core to realize the transition of the optical field. Since the dry etching of lithium niobate is relatively difficult, the process difficulty is high, and there is a potential pollution problem which will lead to incompatibility with CMOS (complementary metal oxide semiconductor) process equipment; scheme three: a thickness-graduated mask is formed on the surface of the thin film by sputtering, and the lithium niobate thin film is formed to have a thickness gradient by chemical mechanical polishing (CMP). However, this scheme has the problems of low mask manufacturing efficiency, difficulty in forming multiple thickness-graduated masks on the same substrate, or difficulty in accurately controlling the size of the mask (resulting in the size of the thickness-graduated thin film).

[0004] Therefore, a preparation method of an electro-optical modulation device is needed, which uses one-step or no-lithium niobate etching process to realize 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-optical phase modulation device. SUMMARY

[0005] Therefore, the present application provides a preparation method of an electro-optical modulation device to solve the problems of high difficulty in transferring two-dimensional tapered structure lithium niobate, the need for multiple steps of lithium niobate dry etching, and the difficulty in accurately controlling the thickness gradient mask in the preparation method of the existing electro-optical modulation device, resulting in high optical field transition loss between a silicon nitride waveguide and a silicon nitride-lithium niobate composite waveguide.

[0006] The present application provides a preparation method of an electro-optical modulation device, comprising:

[0007] An electro-optical material wafer is provided, which comprises a first substrate, a first compressive stress layer, and an initial electro-optical material layer in sequence;

[0008] The first substrate is thinned on the side opposite to the first compressive stress layer, and at the same time, the electro-optical material wafer is warped and protrudes towards the initial electro-optical material layer;

[0009] The first substrate is fixed, and the warped protruding part of the initial electro-optical material layer is ground until part 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 grooves at least penetrate the initial electro-optical material layer in the depth direction and extend into the first compressive stress layer;

[0010] The electro-optical material wafer after grinding is cut to form an electro-optical material wafer chip; the electro-optical material wafer chip comprises 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;

[0011] The first substrate and the first compressive stress layer in the electro-optical material wafer chip are removed, and the remaining initial electro-optical material layer serves as an electro-optical material layer;

[0012] A second substrate is provided, and a lower cladding layer, a waveguide core, and a bonding medium layer are formed in sequence on one side surface of the second substrate, and the bonding medium layer covers the side surface of the waveguide core opposite to the second substrate and the side surface of the waveguide core;

[0013] The electro-optical material layer is bonded to the side surface of the bonding medium layer opposite to the waveguide core; wherein the electro-optical material layer corresponds to the waveguide core; the slope structure is located on both sides of the length direction of the waveguide core;

[0014] An electrode is formed on the side surface of the electro-optical material layer opposite to the bonding medium layer, and the electrode is located at the corresponding position on both sides of the waveguide core.

[0015] Optionally, in the step of providing the electro-optical material wafer, the electro-optical material wafer comprises, in sequence, a first substrate, a plurality of parallel first compressive stress layers, and a plurality of parallel initial electro-optical 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-optical material layers; each of the initial electro-optical material layers is located on at least one of the first compressive stress layers.

[0016] In the step of thinning the first substrate from the side opposite to the first compressive stress layers, and causing the electro-optical material wafer to warp and bulge towards the initial electro-optical material layers, the electro-optical material wafer warps along the length direction of each of the initial electro-optical material layers.

[0017] In the step of fixing the first substrate, and grinding the bulging part of the initial electro-optical material layers until part of the first compressive stress layers or the first substrate is exposed, to form a plurality of strip-shaped grooves with slope structures on two sides, the length direction of the strip-shaped grooves is perpendicular to the length direction of the plurality of initial electro-optical material layers.

[0018] Optionally, in the step of providing the electro-optical material wafer, the step comprises:

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

[0020] forming the initial electro-optical material layer on the side surface of the first compressive stress layer opposite to the first substrate;

[0021] performing a patterning process on the first compressive stress layer and the initial electro-optical material layer to form the plurality of parallel first compressive stress layers and the plurality of parallel initial electro-optical material layers.

[0022] Optionally, in the step of providing the electro-optical material wafer, the step comprises:

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

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

[0025] forming the initial electro-optical material layer on the side surface of the plurality of first compressive stress layers opposite to the first substrate;

[0026] performing a patterning process on the initial electro-optical material layer to form the plurality of parallel initial electro-optical 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-optical material layers; each of the initial electro-optical material layers is located on at least one of the first compressive stress layers.

[0027] Optionally, in the step of forming the initial electro-optical material layer on the side surface of the plurality of first compressive stress layers opposite to 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 plurality of compressive stress layers.

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

[0029] forming a plurality of sacrificial layers on the plurality of first compressive stress layers, wherein the plurality of sacrificial layers cover the side surface of the plurality of first compressive stress layers away from the first substrate and the side surface of the plurality of first compressive stress layers;

[0030] In the step of forming the initial electro-optical material layer on the side surface of the plurality of first compressive stress layers away from the first substrate, the method further comprises:

[0031] forming the initial electro-optical material layer on the side surface of the plurality of sacrificial layers away from the plurality of first compressive stress layers.

[0032] Optionally, the plurality of sacrificial layers are photoresist layers or temporary bonding glue layers.

[0033] The thickness of the plurality of sacrificial layers above the plurality of first compressive stress layers is 1-5 μm.

[0034] Optionally, in the step of cutting the ground electro-optical material wafer to form the electro-optical material wafer chips, the method further comprises:

[0035] cutting the ground electro-optical material wafer along the length direction of the strip-shaped groove and the length direction of the plurality of initial electro-optical material layers to form the electro-optical material wafer chips.

[0036] Optionally, the plurality of first compressive stress layers are complete strip-shaped first compressive stress layers exposing part of the surface of the first substrate or ridge-shaped strip-shaped first compressive stress layers not exposing the surface of the first substrate.

[0037] Optionally, in the step of fixing the first substrate and grinding the warped convex part of the initial electro-optical material layer until part of the first compressive stress layers or the first substrate is exposed to form the plurality of strip-shaped grooves with the slope structure on both sides, the method further comprises:

[0038] fixing the warped electro-optical material wafer on a support table with a cylindrical surface, wherein the side of the first substrate away from the plurality of first compressive stress layers is in contact with the support table.

[0039] grinding the warped convex part of the initial electro-optical material layer by a chemical mechanical polishing process until part of the first compressive stress layers or the first substrate is exposed, and simultaneously forming two slope structures on the initial electro-optical material layer in a direction perpendicular to the warping direction.

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

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

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

[0043] The electro-optical material wafer piece is adsorbed by a transfer device, and the transfer device is in contact with the side of the initial electro-optical material layer away from the first compressive stress layer.

[0044] The electro-optical material wafer piece is immersed in an etching solution to remove the first compressive stress layer, so that 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 left as the electro-optical material layer.

[0045] The electro-optical material layer is cleaned.

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

[0047] The electro-optical material wafer piece is adsorbed by a transfer device, and the transfer device is in contact with the side of the initial electro-optical material layer away from the first compressive stress layer.

[0048] The electro-optical material wafer piece is immersed in an organic solvent to remove the sacrificial layer, so that the initial electro-optical material layer is separated from the first compressive stress layer and the first substrate, the initial electro-optical material layer is restored to be flat, and the remaining initial electro-optical material layer is left as the electro-optical material layer.

[0049] The electro-optical material layer is cleaned.

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

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

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

[0053] Optionally, the electro-optical material wafer further comprises a second compressive stress layer located on the side surface of the first substrate 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 away from the first compressive stress layer, the method further comprises:

[0055] Removing the second compressive stress layer.

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

[0057] Forming the lower cladding layer on the side surface of the second substrate;

[0058] Forming the waveguide core and the bonding medium layer on the side surface of the lower cladding layer away from the second substrate, and the bonding medium layer covering the side surface of the waveguide core away from the second substrate and the side surface of the waveguide core.

[0059] The technical scheme of the present application has the following advantages:

[0060] (1) The method for manufacturing an electro-optical modulation device provided by the present application, on the one hand, by thinning the side of the first substrate away from the first compressive stress layer, the wafer of electro-optical material generates a warp that makes the initial electro-optical material layer protrude, and the protruding part of the initial electro-optical material layer is ground, so as to form a smooth and thickness-gradually-changing slope structure on the initial electro-optical material layer, and by controlling the radius of curvature of the warp and the grinding depth, the slope and size of the slope structure can be controlled, so that the finally formed electro-optical material layer has a slope structure with a smaller surface roughness and an easily controlled slope. The present application uses the process of warping + grinding to form a smooth and thickness-gradually-changing slope structure on the initial electro-optical material layer, which is simple in process, high in process efficiency, and high in utilization rate of electro-optical material, reduces the 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 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 optical field transition loss of the electro-optical modulation device. At the same time, the slope structure preparation method in the present application has a lower alignment accuracy requirement, the surface roughness of the formed slope structure is smaller and the slope is easily controlled, and there is no absorption loss caused by additional materials, so that the electro-optical modulation device has a lower transition loss. Therefore, the method for manufacturing an electro-optical modulation device provided by the present application can improve the process efficiency and the utilization rate of electro-optical material, simplify the process flow, reduce the process difficulty, and effectively reduce the optical field transition loss of the electro-optical modulation device.

[0061] (2) The preparation method of the electro-optical modulation device provided by the application, the electro-optical material wafer sequentially comprises a first substrate, a plurality of parallel first compressive stress layers and a plurality of parallel initial electro-optical 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-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 when being ground, the length direction of the strip-shaped groove formed is perpendicular to the length direction of the plurality of initial electro-optical material layers, so that 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 direction of the plurality of first compressive stress layers and the crystal direction of the plurality of initial electro-optical material layers, the electro-optical modulation device can have high electro-optical modulation efficiency, and the transition loss between the waveguide core and the waveguide core-electro-optical material hybrid waveguide can be further reduced.

[0062] (3) The preparation method of the electro-optical modulation device provided by the application, in the step of providing the electro-optical material wafer, the first compressive stress layer and the initial electro-optical material layer are sequentially formed on the first substrate, and then the first compressive stress layer and the initial electro-optical material layer are subjected to a patterning process to form the plurality of parallel first compressive stress layers and the plurality of parallel initial electro-optical material layers, so that only one step of patterning process is needed, the process flow can be simplified, 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 direction of the plurality of first compressive stress layers and the crystal direction of the plurality of initial electro-optical material layers, so that the electro-optical modulation device can have high electro-optical modulation efficiency.

[0063] (4) The preparation method of the electro-optical modulation device provided by the application, in the step of providing the electro-optical material wafer, the plurality of parallel first compressive stress layers are first formed, then the initial electro-optical material layer is formed on the side surface of the plurality of first compressive stress layers away from the first substrate, and the initial electro-optical material layer is subjected to a patterning process to form the plurality of parallel initial electro-optical material layers, so that only one step of patterning process is needed on the initial electro-optical material layer, different sizes of electro-optical material layers can be obtained according to requirements, the initial electro-optical material layer is formed on the plurality of first compressive stress layers, the relative relationship between the crystal direction of the initial electro-optical material layer and the length direction of the plurality of first compressive stress layers can be better controlled, the relative relationship between the direction of the slope structure and the crystal direction of the electro-optical material layer can be better controlled, the electro-optical modulation device can have high electro-optical modulation efficiency. In addition, in the preparation method of the electro-optical modulation device provided by the present embodiment, the plurality of first compressive stress layers can correspond to the plurality of initial electro-optical material layers below each 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 to the initial electro-optical material layer caused by the etching liquid can be reduced.

[0064] (5) The preparation method of the electro-optical modulation device provided by the application, in the step of forming an initial electro-optical material layer on the side surface of the plurality of first compressive stress layers away from the first substrate, the crystal direction of the initial electro-optical material layer is parallel, perpendicular or at a certain angle to the length direction of the plurality of compressive stress layers, which can make the direction of the slope structure formed parallel, perpendicular or at a certain angle to the crystal direction of the electro-optical material layer, and is beneficial to ensuring that the electro-optical modulation device has a high electro-optical modulation efficiency.

[0065] (6) The preparation method of the electro-optical modulation device provided by the application, the electro-optical material wafer piece is adsorbed by using the transfer device, the transfer device is in contact with the side of the initial electro-optical material layer away from the first compressive stress layer, the electro-optical material wafer piece is immersed in the 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, 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 piece through a wet process, and meanwhile, the transfer device can be used to facilitate the subsequent bonding of the electro-optical material to the bonding medium layer, so that the process flow is simplified and the process efficiency is improved.

[0066] (7) The preparation method of the electro-optical modulation device provided by the application, the electro-optical material layer is bonded to the side surface of the bonding medium layer away from the waveguide core by using the transfer device, wherein the electro-optical material layer corresponds to the waveguide core, and the slope surface of the electro-optical material layer is away from the waveguide core; the slope structure makes the edge thickness of the electro-optical material layer gradually decrease from inside to outside, and further makes the transition between the waveguide core and the waveguide core-electro-optical material composite waveguide smoother, so that the optical field transition loss of the electro-optical modulation device is reduced.

[0067] (8) The preparation method of the electro-optical modulation device provided by the application, the electro-optical material wafer piece is adsorbed by using the transfer device, the transfer device is in contact with the side of the initial electro-optical material layer away from the first compressive stress layer, wherein a plurality of first compressive stress layers correspond to each column of initial electro-optical material layers, the electro-optical material wafer piece is immersed in the 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 the process efficiency, and reduce the etching damage that the etching solution may cause to the initial electro-optical material layer.

[0068] (9) The preparation method of the electro-optical modulation device provided by the application, the electro-optical material wafer piece is adsorbed by using the transfer device, the transfer device is in contact with the side of the initial electro-optical material layer away from the first compressive stress layer, and a sacrificial layer is arranged between the initial electro-optical material layer and the first compressive stress layer, so that the initial electro-optical material layer can be separated from the first compressive stress layer / first substrate by immersing the electro-optical material wafer piece in an organic solvent to remove the sacrificial layer, without using etching solution to remove the first compressive stress layer to separate the initial electro-optical material layer and the first substrate, thereby avoiding the etching damage that the etching solution may cause to the initial electro-optical material layer. BRIEF DESCRIPTION OF DRAWINGS

[0069] In order to more clearly illustrate the technical solutions of the specific embodiments or the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0070] Figure 1 Flowchart of a preparation method of an electro-optical modulation device according to an embodiment of the present application;

[0071] Figure 2 Flowchart of another preparation method of an electro-optical modulation device according to an embodiment of the present application;

[0072] Figure 3 Flowchart of a forming method of an electro-optical material wafer according to an embodiment of the present application;

[0073] Figure 4 Flowchart of another forming method of an electro-optical material wafer according to an embodiment of the present application;

[0074] Figure 5 Flowchart of still another forming method of an electro-optical material wafer according to an embodiment of the present application;

[0075] Figure 6 、 Figure 7 、 Figure 8 、 Figure 9A 、 Figure 9B and Figure 9C Structure diagram of each flow of the forming method of the electro-optical material wafer according to an embodiment of the present application;

[0076] Figure 9A 、 Figure 9B and Figure 9C Structure diagram of a completely strip-shaped first compressive stress layer according to an embodiment of the present application;

[0077] Figure 10A and Figure 10B Structure diagram of a ridge-shaped strip-shaped first compressive stress layer according to an embodiment of the present application;

[0078] Figure 11A and Figure 11B Structure diagram of the thinning first substrate step in the preparation method of the electro-optical modulation device according to an embodiment of the present application;

[0079] Figure 12 、 Figure 13A and Figure 13BA structure diagram of a step of grinding a warped convex part of an initial electro-optical material layer in a preparation method of an electro-optical modulation device according to an embodiment of the present application;

[0080] Figure 14 A structure diagram of an electro-optical material wafer in a preparation method of an electro-optical modulation device according to an embodiment of the present application;

[0081] Figure 15 A structure diagram of a step of removing a first substrate and a first compressive stress layer in a preparation method of an electro-optical modulation device according to an embodiment of the present application;

[0082] Figure 16 A structure diagram of an electro-optical material layer in a preparation method of an electro-optical modulation device according to an embodiment of the present application;

[0083] Figure 17 、 Figure 18A 、 Figure 18B and Figure 18C A structure diagram of a step of bonding the electro-optical material layer to a bonding medium layer in a preparation method of an electro-optical modulation device according to an embodiment of the present application;

[0084] Figure 19A 、 Figure 19B and Figure 19C A structure diagram of a step of forming an electrode and an upper cladding layer in a preparation method of an electro-optical modulation device according to an embodiment of the present application;

[0085] Figure 20 、 Figure 21 、 Figure 22A and Figure 22B Structure diagrams of respective processes of another electro-optical material wafer forming method according to an embodiment of the present application;

[0086] Figure 23A 、 Figure 23B and Figure 23C Structure diagrams of respective processes of still another electro-optical material wafer forming method according to an embodiment of the present application;

[0087] Figure 24 A specific process diagram of a preparation method of an electro-optical modulation device according to an embodiment of the present application.

[0088] BRIEF DESCRIPTION OF THE DRAWINGS

[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 layer; 23 - waveguide core; 24 - bonding medium layer; 26 - electrode; 27 - upper cladding layer; 100 - electro-optic material substrate; 200 - support table; 300 - polishing pad; 400 - transfer device; 500 - etching liquid; 600 - an electro-optic modulator. DETAILED DESCRIPTION

[0090] In the prior art, one of the problems faced by the 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 existing technical solutions for realizing the transition of the optical field between lithium niobate and silicon nitride waveguides all have certain defects: Solution one: a two-dimensional tapered structure of lithium niobate is integrated into a silicon nitride platform by a transfer process to realize the transition of the optical field, but this solution requires a high alignment accuracy between the two-dimensional tapered structure and the silicon nitride waveguide core, increasing the process difficulty; Solution two: lithium niobate is subjected to multiple dry etching processes to form multiple steps along the two sides of the silicon nitride waveguide core to realize the transition of the optical field. Since dry etching of lithium niobate is relatively difficult, the process difficulty is high, and there is a potential pollution problem that will lead to incompatibility with CMOS process equipment; Solution three: a thickness-gradually-changing mask is formed on the surface of the thin film by sputtering, and the lithium niobate thin film is made to have a gradually changing thickness by chemical mechanical polishing (CMP). However, this solution has problems such as low mask manufacturing efficiency, difficulty in forming multiple thickness-gradually-changing masks on the same substrate, or inability to accurately control the size of the mask (resulting in the size of the thickness-gradually-changing thin film).

[0091] In addition, there is also a solution of gray-tone lithography and dry etching process to form a slope structure on lithium niobate or a material with a refractive index close to that of lithium niobate to realize the transition of the optical field. However, it is relatively difficult to form a slowly-varying slope structure on a relatively thin (a few hundred nanometers thick) electro-optic material thin film by gray-tone lithography + etching process: First, gray-tone lithography requires a relatively high-cost mask or a complex coding process; second, dry etching of lithium niobate is relatively difficult to control the thickness and surface roughness; third, the dry etching of the slope structure on lithium niobate is usually dominated by physical etching (with a relatively low etching selectivity for photoresist, electro-optic material, and waveguide substrate surface material), which is easy to cause damage to the waveguide substrate itself; fourth, the formation of a slope structure on other materials with a refractive index close to that of lithium niobate will also cause light scattering and increase the optical transition loss due to the deviation of the refractive index and thickness of the other materials from the electro-optic material.

[0092] To address the challenges of high optical field transition loss between silicon nitride (SiN) waveguides and SiN-LiNO composite waveguides in existing electro-optic modulation device fabrication methods, including the difficulty in transferring two-dimensional conical lithium niobate structures, the need for multi-step dry etching of lithium niobate, and the difficulty in precisely controlling the thickness of gradient masks, resulting in low optical field transition loss between SiN and SiN-LiNO composite waveguides, this invention provides a method for fabricating an electro-optic modulation device. The method includes: providing an electro-optic material wafer, which sequentially comprises a first substrate, a first compressive stress layer, and an initial electro-optic material layer; thinning the side of the first substrate away from the first compressive stress layer while simultaneously warping the electro-optic material wafer to bulge towards the initial electro-optic material layer; fixing the first substrate; and grinding the warped and bulging portion of the initial electro-optic material layer until a portion of the first compressive stress layer or the first substrate is exposed, forming multiple strip-shaped grooves with sloping sides; the strip-shaped grooves... The process penetrates at least the initial electro-optic material layer and extends into the first compressive stress layer in the depth direction; the polished electro-optic material wafer is cut to form an electro-optic material wafer piece; the electro-optic material wafer piece includes a portion of the first substrate, a portion of the first compressive stress layer, and a portion of the initial electro-optic material layer with slope structures on both sides; the first substrate and the first compressive stress layer in the electro-optic material wafer piece are removed, and the remaining initial electro-optic material layer is used as the electro-optic material layer; a second substrate is provided, and a lower cladding layer, a waveguide core, and a bonding dielectric layer are sequentially formed on one side surface of the second substrate, the bonding dielectric layer covering the side surface of the waveguide core facing away from the second substrate and the side surface of the waveguide core; the electro-optic material layer is bonded to the side surface of the bonding dielectric layer facing away from the waveguide core; wherein, the electro-optic material layer corresponds to the waveguide core; the slope structure is located on both sides of the waveguide core in the length direction; electrodes are formed on the side surface of the electro-optic material layer facing away from the bonding dielectric 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 now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort 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 should not be construed as indicating or implying relative importance.

[0094] Example 1

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

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

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

[0098] S102, thinning the first substrate 11 on the side opposite to the first compressive stress layer 12, and at the same time, causing the electro-optical material wafer to be warped and protrude towards the initial electro-optical material layer 13, as shown in Figure 11B

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

[0100] S103, fixing the first substrate 11, and grinding the warped and protruding 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, as shown in Figure 12 The strip-shaped grooves at least penetrate the initial electro-optical material layer 13 in the depth direction and extend into the first compressive stress layer 12, as shown in Figure 13A

[0101] S104, cutting the ground electro-optical material wafer to form electro-optical material wafer chips; the electro-optical material wafer chip includes part of the first substrate 11, part of the first compressive stress layer 12 and part of the initial electro-optical material layer 13 with slope structures on both sides, as shown in Figure 14

[0102] S105, removing the first substrate 11 and the first compressive stress layer 12 in the electro-optical material wafer chip, and the remaining initial electro-optical material layer 13 serves as an electro-optical material layer 130, as shown in Figures 15-16

[0103] S106, providing a second substrate 21, and sequentially forming a lower cladding layer 22, a waveguide core 23 and a bonding medium layer 24 on the side surface of the second substrate 21, the bonding medium layer 24 covering the side surface of the waveguide core 23 opposite to the second substrate 21 and the side surface of the waveguide core 23, as shown in Figure 17

[0104] S107, bonding the electro-optical material layer 130 to the side surface of the bonding medium layer 24 opposite to the waveguide core 23; wherein the electro-optical material layer 130 corresponds to the waveguide core 23; and the slope structure is located on both sides of the waveguide core 23 in the length direction, as shown in Figures 18A-18C

[0105] ​​​​​​S108, an electrode 26 is formed on the surface of the electro-optic material layer 130 on the side opposite to the bonding dielectric layer 24. The electrode 26 is located at corresponding positions on both sides of the waveguide core, such as... Figures 19A-19C As shown.

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

[0107] The method for fabricating the electro-optic modulation device provided in this embodiment involves, on the one hand, thinning the side of the first substrate away from the first compressive stress layer, causing the electro-optic material wafer to warp and protrude from the initial electro-optic material layer. Grinding the warped protrusions of the initial electro-optic material layer forms a smooth, gradually thickened slope structure on the initial electro-optic material layer. Furthermore, by controlling the radius of curvature of the warp and the grinding depth, the slope and size of the slope structure can be controlled, resulting in a final electro-optic material layer with a low surface roughness and easily controllable slope. This solution utilizes a warping + grinding process to form a smooth, gradually thickened slope on the initial electro-optic material layer. The slope structure of this method is simple to implement, highly efficient, and maximizes the utilization of electro-optic materials. It reduces the number of etching operations on the electro-optic material layer during fabrication, simplifying the process, reducing complexity, and improving efficiency and material utilization. Furthermore, the slope structure of the electro-optic material layer, located on both sides of the waveguide core's length, reduces the optical field transition loss of the electro-optic modulator. The slope structure fabrication method in this embodiment also has lower alignment accuracy requirements, resulting in a smaller surface roughness and easier slope control. Moreover, it eliminates absorption losses caused by additional materials, leading to even lower transition losses in the electro-optic modulator. Therefore, the fabrication method for the electro-optic modulator provided in this embodiment improves process efficiency and material utilization, simplifies the process, reduces complexity, and effectively lowers the optical field transition loss of the electro-optic modulator.

[0108] Furthermore, in some embodiments, in the step of providing the electro-optic material wafer, the electro-optic material wafer sequentially includes a first substrate 11, multiple parallel rows of first compressive stress layers 12, and multiple parallel rows of initial electro-optic material layers 13; the length direction of the multiple rows of first compressive stress layers 12 is the same as the length direction of the multiple rows of initial electro-optic material layers 13; each row of initial electro-optic material layers 13 is located on at least one row of first compressive stress layers 12;

[0109] In the step of thinning the first substrate 11 on the side opposite to the first compressive stress layer 12 and simultaneously causing the electro-optic material wafer to warp and bulge toward the initial electro-optic material layer 13, the electro-optic material wafer forms warp along the length direction of each column of the initial electro-optic material layer 13.

[0110] In the step of fixing the first substrate 11 and grinding the warped protrusions of the initial electro-optic material layer 13 until the first compressive stress layer 12 or the first substrate 11 is exposed to form a plurality of strip grooves with sloped structures on both sides, the length direction of the strip grooves is perpendicular to the length direction of the plurality of rows of initial electro-optic material layers 13.

[0111] In specific implementation, such as Figure 2 As shown, this embodiment also provides another method for fabricating an electro-optic modulation device, including steps S201 to S208.

[0112] S201, an electro-optic material wafer is provided, the electro-optic material wafer comprising, in sequence, a first substrate 11 stacked, multiple rows of mutually parallel first compressive stress layers 12, and multiple rows of mutually parallel initial electro-optic material layers 13; the length direction of the multiple rows of first compressive stress layers 12 is the same as the length direction of the multiple rows of initial electro-optic material layers 13; each row of initial electro-optic material layers 13 is located on at least one row of first compressive stress layers 12, such as... Figures 9A-9C or Figures 10A-10B As shown.

[0113] S202, the first substrate 11 is thinned on the side opposite to the first compressive stress layer 12, while simultaneously causing the electro-optic material wafer to warp and bulge towards the initial electro-optic material layer 13; the electro-optic material wafer forms warpage along the length direction of each column of the initial electro-optic material layer 13, such as Figure 11A and Figure 11B As shown.

[0114] In practice, the electro-optic material wafer warps along the length of each column of initial electro-optic material layers 13. For example... Figure 11A for Figure 9A The cross-sectional view at position ① in the top view of the electro-optic material wafer, that is, the width direction of each column of initial electro-optic material layer 13, shows that the warpage of the electro-optic material wafer is relatively small; as shown in the figure. Figure 11B for Figure 9A The cross-sectional view at position ② in the top view of the electro-optic material wafer, which is the length direction of each column of initial electro-optic material layer 13, shows that the warpage of the electro-optic material wafer is relatively large, and it bulges towards the initial electro-optic material layer 13.

[0115] S203, fix the first substrate 11, and grind the warped protrusions of the initial electro-optic material layer 13 until the first compressive stress layer 12 or the first substrate 11 is exposed, forming multiple strip-shaped grooves with sloping structures on both sides, such as... Figure 12As shown in FIG. 2, the strip-shaped groove extends in the depth direction through the initial electro-optical material layer 13 and into the first compressive stress layer 12; the length direction of the strip-shaped groove is perpendicular to the length direction of the plurality of columns of initial electro-optical material layers 13. Figure 13A and Figure 13B As shown in FIG. 3.

[0116] In particular implementation, Figure 13B FIG. 4 is a top view of the electro-optical material wafer after grinding, Figure 13A FIG. 5 is a cross-sectional view of the position ② in FIG. 4. Figure 13B

[0117] S204, cutting the electro-optical material wafer after grinding to form electro-optical material wafer chips; the electro-optical material wafer chips include part of the first substrate 11, part of the first compressive stress layer 12, and part of the initial electro-optical material layer 13 with slope structures on both sides, as shown in FIG. 6. Figure 14

[0118] S205, removing the first substrate 11 and the first compressive stress layer 12 in the electro-optical material wafer chips, and the remaining initial electro-optical material layer 13 serves as an electro-optical material layer 130, as shown in FIG. 7. Figures 15-16

[0119] S206, providing a second substrate 21, sequentially forming a lower cladding layer 22, a waveguide core 23, and a bonding medium layer 24 on one side surface of the second substrate 21, the bonding medium layer 24 covering the side surface of the waveguide core 23 away from the second substrate 21, as shown in FIG. 8. Figure 17

[0120] S207, bonding the electro-optical material layer 130 to the side surface of the bonding medium layer 24 away from the waveguide core 23; wherein the electro-optical 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, as shown in FIG. 9. Figures 18A-18C

[0121] S208, forming an electrode 26 on the side surface of the electro-optical material layer 130 away from the bonding medium layer 24, the electrode 26 being located at the corresponding position on both sides of the waveguide core, as shown in FIG. 10. Figures 19A-19C

[0122] ​​​​​​The application provides a preparation method of an electro-optical modulation device. The electro-optical material wafer sequentially comprises a first substrate, a plurality of parallel first compressive stress layers and a plurality of parallel initial electro-optical 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-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 when being ground, the length direction of the strip-shaped groove formed is perpendicular to the length direction of the plurality of initial electro-optical material layers, so that 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 direction of the plurality of first compressive stress layers and the crystal direction of the plurality of initial electro-optical material layers, the electro-optical modulation device has high electro-optical modulation efficiency, and the transition loss between the waveguide core and the waveguide core-electro-optical material hybrid waveguide can be further reduced.

[0123] Further, in some embodiments, Figure 3 The application provides a flowchart of the forming method of the electro-optical material wafer, and the steps of providing the electro-optical material wafer comprise the following steps.

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

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

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

[0127] The application provides a preparation method of an electro-optical modulation device. The application provides an electro-optical material wafer, and the steps of providing the electro-optical material wafer comprise the following steps. First, a first compressive stress layer and an initial electro-optical material layer are sequentially formed on a first substrate, and then a patterning process is performed on the first compressive stress layer and the initial electro-optical material layer to form a plurality of parallel first compressive stress layers and a plurality of parallel initial electro-optical material layers. Only one step of patterning process is needed, so that the process flow can be simplified, 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 direction of the plurality of first compressive stress layers and the crystal direction of the plurality of initial electro-optical material layers, so that the electro-optical modulation device has high electro-optical modulation efficiency.

[0128] Further, in some embodiments, Figure 4 The application provides a flowchart of the forming method of the electro-optical material wafer, and the steps of providing the electro-optical material wafer comprise the following steps.

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

[0130] S22, performing a patterning process on the first compressive stress layer 12 to form a plurality of parallel columns of the first compressive stress layer 12, as shown in Figure 21 .

[0131] S23, forming an initial electro-optical material layer 13 on a side surface of the plurality of columns of the first compressive stress layer 12 away from the first substrate 11, as shown in Figure 22A .

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

[0133] The preparation method of the electro-optical modulation device provided in the embodiment, in the step of providing the electro-optical material wafer, a plurality of parallel columns of the first compressive stress layer are first formed, then an initial electro-optical material layer is formed on a side surface of the plurality of columns of the first compressive stress layer away from the first substrate, a patterning process is performed on the initial electro-optical material layer to form a plurality of parallel columns of the initial electro-optical material layer, only one step of patterning process is needed for the initial electro-optical material layer, and electro-optical material layers of different sizes can be obtained according to requirements, meanwhile, the initial electro-optical material layer is formed on the plurality of columns of the first compressive stress layer, so that the relative relationship between the crystal direction of the initial electro-optical material layer and the length direction of the plurality of columns of the first compressive stress layer can be better controlled, thereby the relative relationship between the direction of the slope structure and the crystal direction of the electro-optical material layer can be better controlled, and the electro-optical modulation device has a higher electro-optical modulation efficiency. In addition, the preparation method of the electro-optical modulation device provided in the embodiment can correspond to the plurality of columns of the first compressive stress layer below each column of the 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 to the initial electro-optical material layer caused by the etching liquid can be reduced.

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

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

[0136] The preparation method of the electro-optical modulation device provided in the embodiment can make the direction of the slope structure parallel, perpendicular or at a certain angle to the crystal direction of the electro-optical material layer, which is beneficial to ensuring that the electro-optical modulation device has higher electro-optical modulation efficiency.

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

[0138] forming a sacrificial layer 14 on the plurality of first compressive stress layers 12; the sacrificial layer 14 covers the surface of the first compressive stress layer 12 away from the first substrate 11 and the side surface of the plurality of first compressive stress layers 12;

[0139] In the step of forming the initial electro-optical material layer 13 on the side surface of the plurality of first compressive stress layers 12 away from the first substrate 11, the step comprises:

[0140] forming the initial electro-optical material layer 13 on the side surface of the sacrificial layer 14 away from the first compressive stress layer 12.

[0141] In practice, Figure 5 For another flowchart of the forming method of the electro-optical material wafer, the step of providing the electro-optical material wafer comprises:

[0142] S31, forming a first compressive stress layer 12 on a first substrate 11, as shown in Figure 20 ;

[0143] S32, performing a patterning process on the first compressive stress layer 12 to form a plurality of first compressive stress layers 12 parallel to each other, as shown in Figure 21 ;

[0144] S33, forming a sacrificial layer 14 on the plurality of first compressive stress layers 12; the sacrificial layer 14 covers the surface of the first compressive stress layer 12 away from the first substrate 11 and the side surface of the plurality of first compressive stress layers 12, as shown in Figure 23A ;

[0145] S34, forming an initial electro-optical material layer 13 on the side surface of the sacrificial layer 14 away from the first compressive stress layer 12, as shown inFigure 23B As shown;

[0146] S35, a patterning process is performed on the initial electro-optic material layer 13 to form multiple parallel rows of initial electro-optic material layers 13; the length direction of the multiple rows of first compressive stress layers 12 is the same as the length direction of the multiple rows of initial electro-optic material layers 13; each row of initial electro-optic material layers 13 is located on at least one row of first compressive stress layers 12, such as Figure 23C As shown.

[0147] The method for fabricating an electro-optic modulation device provided by this invention includes the following steps in the electro-optic material wafer process: First, a multi-column first compressive stress layer is formed parallel to each other. Then, a sacrificial layer is formed on the multi-column first compressive stress layer. An initial electro-optic material layer is formed on the side of the sacrificial layer facing away from the first compressive stress layer. Finally, the initial electro-optic material layer is patterned to form a multi-column initial electro-optic material layer parallel to each other. By setting a sacrificial layer between the multi-column first compressive stress layer and the initial electro-optic material layer, the initial electro-optic material layer and the first compressive stress layer / first substrate can be separated by dissolving the sacrificial layer with an organic solvent. This avoids 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] Furthermore, in some embodiments, the sacrificial layer 14 is a photoresist or a temporary bonding adhesive layer;

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

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

[0151] 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 using a smart ion cutting process, such as... Figure 7 As shown.

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

[0153] Provide electro-optic material substrate 100;

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

[0155] One side surface of the initial electro-optic material layer 13 of the electro-optic material substrate 100 is bonded 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 location of the ion implantation damage layer 101 by thermal annealing, and the ion implantation damage layer 101 is removed.

[0157] Furthermore, in some embodiments, the step of cutting the polished electro-optic material wafer to form small electro-optic material wafer pieces includes:

[0158] The polished electro-optic material wafer is cut along the length of the strip groove and the length of the multiple rows of initial electro-optic material layers 13 to form small electro-optic material wafer pieces.

[0159] Furthermore, in some embodiments, the multiple rows of first compressive stress layers 12 are either fully 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 specific implementations, in some embodiments, such as Figures 9A-9C As shown, the multi-row first compressive stress layer 12 is a fully strip-shaped first compressive stress layer that exposes a portion of the surface of the first substrate 11. Figure 9A This is a top view of the complete strip-shaped first compressive stress layer. Figure 9B for Figure 9A Cross-sectional view at position ① in the middle. Figure 9C for Figure 9A Cross-sectional view at position ② in the middle.

[0161] In other embodiments, such as Figures 10A-10B As shown, the multiple rows of first compressive stress layers 12 are ridge-shaped or strip-shaped first compressive stress layers that do not expose the surface of the first substrate 11. Figure 10A This is a top view of the ridge-shaped strip-shaped first compressive stress layer. Figure 10B for Figure 10A Cross-sectional view at position ①.

[0162] Furthermore, in some embodiments, such as Figure 12 As shown, the step of fixing the first substrate 11 and grinding the warped protrusions of the initial electro-optic material layer 13 until the first compressive stress layer 12 or the first substrate 11 is exposed to form a plurality of strip-shaped grooves with sloping structures on both sides includes:

[0163] The warped electro-optic material wafer is fixed on a support stage 200 with 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 stage 200.

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

[0165] Further, in some embodiments, the length of the slope structure of the initial electro-optical material layer 13 is positively correlated with the radius of curvature of the first substrate 11 or the support table 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 length of the slope of the initial electro-optical material layer 13.

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

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

[0169] Further, in some embodiments, as shown in FIG. 6, in the step of removing the first substrate 11 and the first compressive stress layer 12 in the electro-optical material wafer piece and leaving the initial electro-optical material layer 13 as the electro-optical material layer 130, the method comprises: Figure 15

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

[0171] The electro-optical material wafer piece is immersed in the etching liquid 500 to remove the first compressive stress layer 12, so that 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;

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

[0173] In particular implementation, the etching liquid 500 is an etching liquid for the first compressive stress layer, which 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 structures on both sides make the edge thickness of the electro-optical material layer 130 gradually decrease to 0 from the inside to the outside.

[0174] ​The preparation method of the electro-optical modulation device provided in the embodiment utilizes the transfer device to adsorb the electro-optical material wafer piece, the transfer device contacts the initial electro-optical material layer on the side opposite to the first compressive stress layer, the electro-optical material wafer piece is immersed in the etching liquid, 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, the remaining initial electro-optical material layer serves as the electro-optical material layer, the electro-optical material layer is extracted from the electro-optical material wafer piece through the wet process, and meanwhile, the transfer device can be used to facilitate the subsequent bonding of the electro-optical material to the bonding medium layer, so that the process flow is simplified and the process efficiency is improved.

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

[0176] The transfer device is used to adsorb the electro-optical material wafer piece, and the transfer device contacts the initial electro-optical material layer on the side opposite to the first compressive stress layer.

[0177] The electro-optical material wafer piece is immersed in the organic solvent, the sacrificial layer is removed, the initial electro-optical material layer is separated from the compressive stress layer and the first substrate, the initial electro-optical material layer is restored to be flat, and the remaining initial electro-optical material layer serves as the electro-optical material layer.

[0178] The electro-optical material layer is cleaned.

[0179] The preparation method of the electro-optical modulation device provided in the embodiment utilizes the transfer device to adsorb the electro-optical material wafer piece, the transfer device contacts the initial electro-optical material layer on the side opposite to the first compressive stress layer, the electro-optical material wafer piece is immersed in the etching liquid, 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, the remaining initial electro-optical material layer serves as the electro-optical material layer, the electro-optical material layer is extracted from the electro-optical material wafer piece through the wet process, and meanwhile, the transfer device can be used to facilitate the subsequent bonding of the electro-optical material to the bonding medium layer, so that the process flow is simplified and the process efficiency is improved.

[0180] Further, in some embodiments, the step of bonding the electro-optical material layer 130 to the side surface of the bonding medium layer 24 opposite to the waveguide core 23 includes:

[0181] The transfer device 400 is used to bond the electro-optical material layer 130 to the side surface of the bonding medium layer 24 opposite to the waveguide core 23; wherein the electro-optical material layer 130 corresponds to the waveguide core 23; and the slope surface of the electro-optical material layer 130 is opposite to the waveguide core 23.

[0182] In specific implementation, as shown in Figures 18A-18C , Figure 18A is a top view after the electro-optical material layer 130 is bonded to the bonding medium layer 24, Figure 18B is Figure 18A a cross-sectional view of a position AA in Figure 18C , Figure 18A is a cross-sectional view of a position BB in .

[0183] The method for manufacturing the electro-optical modulation device provided by the embodiment uses a transfer device to bond an electro-optical material layer to a side surface of a bonding medium layer opposite to a waveguide core, wherein the electro-optical material layer corresponds to the waveguide core, and the slope surface of the electro-optical material layer is opposite to the waveguide core. The slope surface structure gradually reduces the edge thickness of the electro-optical material layer from inside to outside to 0, thereby making the transition between the waveguide core and the waveguide core-electro-optical material composite waveguide smoother, and reducing the optical field transition loss of the electro-optical modulation device.

[0184] Further, in some embodiments, the curvature radius of the warping of the thinned electro-optical material wafer 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 thinned first substrate 11.

[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 warping of the electro-optical material wafer can 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] Further, in some embodiments, the electro-optical material wafer further comprises a second compressive stress layer located on the side surface of the first substrate 11 opposite to 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 opposite to the first compressive stress layer 12, the method further comprises:

[0192] The second compressive stress layer is removed.

[0193] Further, in some embodiments, the method for sequentially forming the under cladding layer 22, the waveguide core 23, and the bonding medium layer 24 on the side surface of the second substrate 21 comprises:

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

[0195] A waveguide core 23 and a bonding medium layer 24 are formed on the side surface of the lower cladding layer 22 facing away from the second substrate 21, and the bonding medium layer 24 covers the side 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 layer 22 is silicon dioxide, etc., the thickness of the lower cladding layer 22 is 4 μm to 20 μm, 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 silicon dioxide, aluminum oxide, benzocyclobutene (BCB), derivatives thereof, or other inorganic or organic materials or a combination thereof. The thickness of the bonding medium layer 24 above the waveguide core 23 is 10 nm to 300 nm.

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

[0198] A upper cladding layer 27 is formed on the side surface of the bonding medium layer 24 facing away from the lower cladding layer 22, and the upper cladding layer 27 covers the bonding medium layer 24, the electro-optical material layer 130, and the electrode 26, as shown in Figure 19A 、 Figure 19B and Figure 19C .

[0199] A planarization process is performed on the upper cladding layer 27.

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

[0201] In some embodiments, referring to Figure 24 , the embodiment further provides a specific flow of a preparation method of the electro-optical modulation device 600, including steps S301-S312:

[0202] S301, a first compressive stress layer 12 is formed on a first substrate 11, as shown in Figure 20 . The material of the first compressive stress layer 12 can be silicon dioxide, and the thickness of the first compressive stress layer 12 is 0.5 μm to 10 μm.

[0203] S302, a planarization process is performed on the first compressive stress layer 12 to form a plurality of parallel columns of the first compressive stress layer 12, as shown in Figure 21 .

[0204] S303, an intelligent ion cutting process is performed, as shown inFigures 7-8 As shown, an initial electro-optical material layer 13 is formed on the side surface of the plurality of first compressive stress layers 12 away from the first substrate 11, and the Z-axis orientation of the initial electro-optical material layer 13 is adjusted to be perpendicular to the length direction of the plurality of first compressive stress layers 12, as shown. Figure 22A As shown, the initial electro-optical material layer 13 is an X-cut lithium niobate film.

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

[0206] S305, the first substrate 11 away from the first compressive stress layer 12 is thinned, and the electro-optical material wafer is warped to protrude towards the initial electro-optical material layer 13; the electro-optical material wafer is warped along the length direction of each column of initial electro-optical material layers 13, as shown. Figure 11A Figure 11B

[0207] S306, the warped electro-optical material wafer is fixed on a support table 200 with a cylindrical surface, wherein the side of the first substrate 11 away from the first compressive stress layer 12 is in contact with the support table 200; the protruding part of the initial electro-optical material layer 13 is ground by a polishing pad 300 of a chemical mechanical polishing process until part of the first compressive stress layer 12 is exposed, forming a plurality of strip-shaped grooves with slope structures on both sides, as shown. Figure 12 The strip-shaped grooves at least penetrate the initial electro-optical material layer 13 in the depth direction and extend into the first compressive stress layer 12; the length direction of the strip-shaped grooves is perpendicular to the length direction of the plurality of initial electro-optical material layers 13, as shown. Figure 13A Figure 13B

[0208] S307, the ground electro-optical material wafer is cut along the length direction of the strip-shaped grooves and the length direction of the plurality of initial electro-optical material layers 13, respectively, to form electro-optical material wafer chips; the electro-optical material wafer chips include part of the first substrate 11, part of the first compressive stress layer 12, and part of the initial electro-optical material layer 13 with slope structures on both sides, as shown. Figure 14

[0209] ​​​​​​S308, using the transfer device 400 to adsorb the electro-optical material wafer, the transfer device 400 contacts the initial electro-optical material layer 13 on the side opposite to the first compressive stress layer 12; the electro-optical material wafer is immersed in the etching solution 500 to remove the first compressive stress layer 12, so that 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 is cleaned, such as Figures 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 medium layer 24 on one side surface of the second substrate 21, the bonding medium layer 24 covers the side surface of the waveguide core 23 on the side opposite to the second substrate 21, such as Figure 17 shown.

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

[0212] S311, forming an electrode 26 on the side surface of the electro-optical material layer 130 on the side opposite to the bonding medium layer 24, the electrode 26 is located at the corresponding position on both sides of the waveguide core, such as Figures 19A-19C shown.

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

[0214] Obviously, the above embodiments are only examples for clear illustration, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for fabricating an electro-optic modulation device, characterized in that, include: An electro-optic material wafer is provided, the electro-optic material wafer comprising, in sequence, a first substrate, a first compressive stress layer and an initial electro-optic material layer; Thinning the side of the first substrate away from the first compressive stress layer, while simultaneously causing the electro-optic material wafer to warp and bulge towards the initial electro-optic material layer; Fix the first substrate, and grind the warped protrusion of the initial electro-optic material layer until the first compressive stress layer or the first substrate is exposed, forming a plurality of strip-shaped grooves with sloped structures on both sides. The strip-shaped groove penetrates at least the initial electro-optic material layer and extends into the first compressive stress layer in the depth direction; The polished electro-optic material wafer is cut to form small electro-optic material wafer pieces; The electro-optic material wafer includes a portion of the first substrate, a portion of the first compressive stress layer, and a portion of the initial electro-optic material layer having a sloped structure on both sides; Remove the first substrate and the first compressive stress layer from the electro-optic material wafer, and the remaining initial electro-optic material layer is used as the electro-optic material layer; A second substrate is provided, and a lower cladding layer, a waveguide core, and a bonding dielectric layer are sequentially formed on one side surface of the second substrate. The bonding dielectric layer covers the side surface of the waveguide core facing away from the second substrate and the side surface of the waveguide core. The electro-optic material layer is bonded to the bonding dielectric layer on the side surface facing away from the waveguide core; wherein the electro-optic material layer corresponds to the waveguide core; the slope structure is located on both sides of the waveguide core along its length. An electrode is formed on the surface of the electro-optic material layer facing away from the bonding dielectric layer, and the electrode is located at corresponding positions on both sides of the waveguide core.

2. The method for fabricating the electro-optic modulation device according to claim 1, characterized in that, In the step of providing an electro-optic material wafer, the electro-optic material wafer sequentially includes a first substrate, multiple parallel rows of first compressive stress layers, and multiple parallel rows of initial electro-optic material layers; the length direction of the multiple rows of first compressive stress layers is the same as the length direction of the multiple rows of initial electro-optic material layers; each row of initial electro-optic material layers is located on at least one row of first compressive stress layers. In the step of thinning the first substrate on the side opposite to the first compressive stress layer and simultaneously causing the electro-optic material wafer to warp and bulge toward the initial electro-optic material layer, the electro-optic material wafer forms warp along the length direction of each column of the initial electro-optic material layer. In the step of fixing the first substrate, grinding the warped protrusions of the initial electro-optic material layer until the first compressive stress layer or the first substrate is exposed, and forming a plurality of strip grooves with sloping 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-optic material layers.

3. The method for fabricating the electro-optic modulation device according to claim 2, characterized in that, The step of providing electro-optic material wafers includes: A first compressive stress layer is formed on the first substrate; An initial electro-optic material layer is formed on the surface of the first compressive stress layer facing away from the first substrate; The first compressive stress layer and the initial electro-optic material layer are patterned to form multiple parallel rows of the first compressive stress layer and multiple parallel rows of the initial electro-optic material layer.

4. The method for fabricating the electro-optic modulation device according to claim 2, characterized in that, The step of providing electro-optic material wafers includes: A first compressive stress layer is formed on the first substrate; The first compressive stress layer is patterned to form multiple parallel rows of the first compressive stress layer. An initial electro-optic material layer is formed on the surface of the first compressive stress layer on the side opposite to the first substrate; The initial electro-optic material layer is patterned to form multiple parallel columns of the initial electro-optic material layer; the length direction of the multiple columns of the first compressive stress layer is the same as the length direction of the multiple 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 fabricating the electro-optic modulation device according to claim 4, characterized in that, In the step of forming an initial electro-optic material layer on the side surface of the multiple rows of the first compressive stress layer facing away from the first substrate, the crystal orientation of the initial electro-optic material layer is parallel to or at a certain angle to the length direction of the multiple rows of the compressive stress layer.

6. The method for fabricating the electro-optic modulation device according to claim 4, characterized in that, The step of forming an initial electro-optic material layer on the side surface of the multiple rows of the first compressive stress layers facing away from the first substrate further includes: A sacrificial layer is formed on the plurality 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 surface of the plurality of first compressive stress layers; The step of forming an initial electro-optic material layer on the surface of the plurality of first compressive stress layers facing away from the first substrate includes: An initial electro-optic material layer is formed on the side surface of the sacrificial layer opposite to the first compressive stress layer.

7. The method for fabricating the electro-optic 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 fabricating the electro-optic modulation device according to claim 1, characterized in that, The step of cutting the polished electro-optic material wafer to form small electro-optic material wafer pieces includes: The polished electro-optic material wafer is cut along the length direction of the strip groove and the length direction of the multiple rows of the initial electro-optic material layers to form small electro-optic material wafer pieces.

9. The method for fabricating the electro-optic modulation device according to claim 2, characterized in that, The first compressive stress layer can be a fully strip-shaped first compressive stress layer that exposes a portion of the surface of the first substrate, or a ridge-shaped strip-shaped first compressive stress layer that does not expose the surface of the first substrate.

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

11. The method for fabricating the electro-optic modulation device according to claim 10, characterized in that, In the electro-optic material wafer, 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 stage; The length of the slope structure of the initial electro-optic material layer is negatively correlated with the depth of penetration into the first compressive stress layer during grinding. The deeper the penetration into the first compressive stress layer during grinding, the shorter the slope length of the initial electro-optic material layer.

12. The method for fabricating the electro-optic modulation device according to claim 1, characterized in that, The step of removing the first substrate and the compressive stress layer from the electro-optic material wafer, and using the remaining initial electro-optic material layer as the electro-optic material layer, includes: The electro-optic material wafer is adsorbed using a transfer device, and the transfer device is in contact with the side of the initial electro-optic material layer that is away from the first compressive stress layer. The electro-optic material wafer is immersed in an etching solution to remove the compressive stress layer, thereby separating the initial electro-optic material layer from the first substrate. The initial electro-optic material layer is restored to flatness, and the remaining initial electro-optic material layer serves as the electro-optic material layer. Clean the electro-optic material layer.

13. The method for fabricating the electro-optic modulation device according to claim 6, characterized in that, The step of removing the first substrate and the compressive stress layer from the electro-optic material wafer, and using the remaining initial electro-optic material layer as the electro-optic material layer, includes: The electro-optic material wafer is adsorbed using a transfer device, and the transfer device is in contact with the side of the initial electro-optic material layer that is away from the first compressive stress layer. The electro-optic material wafer is immersed in an organic solvent to remove the sacrificial layer, thereby separating the initial electro-optic material layer from the compressive stress layer and the first substrate. The initial electro-optic material layer is restored to flatness, and the remaining initial electro-optic material layer serves as the electro-optic material layer. Clean the electro-optic material layer.

14. The method for fabricating the electro-optic modulation device according to claim 12 or 13, characterized in that, The step of bonding the electro-optic material layer to the side surface of the bonding dielectric layer facing away from the waveguide core includes: The electro-optic material layer is bonded to the bonding medium layer on the side of the waveguide core that is opposite to 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 fabricating the electro-optic modulation device according to claim 1, characterized in that, The radius of curvature of the thinned electro-optic material wafer is controlled by the stress of the first compressive stress layer, the thickness of the first compressive stress layer, and the thickness of the thinned first substrate.

16. The method for fabricating the electro-optic modulation device according to claim 1, characterized in that, The electro-optic material wafer further includes a second compressive stress layer, which is located on the 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 opposite to the first compressive stress layer, the method further includes: Remove the second compressive stress layer.

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

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