Heterogeneous integrated electro-optical modulator and preparation method thereof

Abstract

The invention relates to the technical field of semiconductors, and discloses a heterogeneous integrated electro-optical modulator and a preparation method thereof, and the preparation method comprises the steps: sequentially forming a buried layer, a first waveguide core layer and a first bonding dielectric layer on the surface of one side of a first substrate; performing a chemical mechanical polishing process on the surface of the first bonding dielectric layer; forming an electro-optical thin film layer on the surface of one side, back to the first waveguide core layer, of the first bonding dielectric layer to form a first waveguide core substrate; providing a bonding platform; enabling the electro-optical thin film layer of the first waveguide core substrate to be in contact and bonding connection with a bonding platform; removing the first substrate, performing a patterning process on the buried layer and the first waveguide core layer to form a first waveguide core, and exposing a part of the first bonding dielectric layer; and forming an electrode on the surface of the first bonding dielectric layer at the side part of the first waveguide core. The thickness uniformity and flatness of the first bonding dielectric layer can be improved, and the uniformity of the heterogeneous integrated electro-optical modulator and the bonding strength, stability and reliability of the electro-optical thin film layer are improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a heterogeneous integrated electro-optic modulation device and a preparation method thereof. Background Art

[0002] The stoichiometric silicon nitride (Si 3 N 4 ) thin film / waveguide core prepared by low-pressure chemical vapor deposition (LPCVD) uses a wafer-level manufacturing process, and has advantages such as transparency in a wide wavelength range (400–2350 nm) and low optical propagation loss at high optical power. However, in an electro-optic phase modulation device in which a silicon nitride optical waveguide is combined with a material having a significant electro-optic effect (such as lithium niobate, etc.), due to the large difference in thermal expansion coefficient between lithium niobate and silicon and silicon dioxide, the lithium niobate thin film will crack due to high thermal stress at high temperatures. Therefore, it is impossible to deposit a silicon nitride thin film on the surface of the lithium niobate thin film on a silicon substrate by LPCVD. In addition, the metal elements contained in lithium niobate will potentially contaminate complementary metal oxide semiconductor (CMOS) process equipment, and the etching of lithium niobate is relatively difficult.

[0003] The prior art solution forms a composite waveguide and an electro-optic modulation device by heterogeneous integration of a silicon nitride waveguide core and a lithium niobate thin film. Specifically, the lithium niobate thin film is bonded above the stoichiometric silicon nitride waveguide core to form a lithium niobate-silicon nitride composite waveguide or an electro-optic modulation device. However, this solution requires a thin (typical thickness ~100 nm), flat, and uniform bonding dielectric layer between the lithium niobate thin film and the patterned stoichiometric silicon nitride. This bonding dielectric layer is usually controlled by a chemical mechanical polishing (CMP) process, and the process difficulty is high, which will result in non-uniform thickness and poor flatness of the bonding dielectric layer, and further lead to low bonding strength of the lithium niobate thin film, poor reliability and performance uniformity of the electro-optic modulation device. Summary of the Invention

[0004] In view of this, the present invention provides a heterogeneous integrated electro-optic modulation device and a preparation method thereof to solve the problem in the related art that it is difficult to control the thickness and flatness of the bonding dielectric layer on the surface of the patterned stoichiometric silicon nitride waveguide core by the CMP process, resulting in poor thickness uniformity and flatness of the bonding dielectric layer, and further leading to low bonding strength of the lithium niobate thin film, poor reliability and performance uniformity of the electro-optic modulation device.

[0005] In a first aspect, the present invention provides a preparation method of a heterogeneous integrated electro-optic modulation device, and the preparation method includes:

[0006] Providing a first substrate, and sequentially forming a buried layer, a first waveguide core layer, and a first bonding dielectric layer on one side surface of the first substrate;

[0007] Perform a chemical mechanical polishing process on the surface of the first bonding dielectric layer facing away from the first waveguide core layer;

[0008] Form an electro-optic thin film layer on the surface of the first bonding dielectric layer facing away from the first waveguide core layer to form a first waveguide core substrate;

[0009] Provide a bonding platform;

[0010] Bring the electro-optic thin film layer of the first waveguide core substrate into contact with the bonding platform and bond them together;

[0011] Remove the first substrate, and on the side of the buried layer facing away from the first waveguide core layer, perform a patterning process on the buried layer and the first waveguide core layer to form a first waveguide core, exposing a part of the first bonding dielectric layer;

[0012] Form an electrode on the surface of the first bonding dielectric layer on the side of the first waveguide core.

[0013] The preparation method of the heterogeneous integrated electro-optic modulation device provided by the present invention, on the one hand, forms a first bonding dielectric layer on the entire surface of the first waveguide core layer, and performs a chemical mechanical polishing process on the first bonding dielectric layer, which can reduce the difficulty of the chemical mechanical polishing process, improve the thickness uniformity and flatness of the first bonding dielectric layer, improve the uniformity of the heterogeneous integrated electro-optic modulation device and the bonding strength of the electro-optic thin film layer, and further improve the reliability of the heterogeneous integrated electro-optic modulation device; it can alleviate problems such as poor uniformity of electro-optic modulation characteristics and low bonding strength of the electro-optic thin film layer caused by uneven thickness and poor flatness of the bonding dielectric layer. On the other hand, after bonding the first waveguide core substrate to the bonding platform, a patterned first waveguide core is formed, which can form a composite waveguide of the first waveguide core - electro-optic thin film layer. The first bonding dielectric layer can be used as a protective layer during the etching of the first waveguide core layer to avoid etching damage to the electro-optic thin film layer, and avoid the increase in light propagation loss and the deterioration of the uniformity of electro-optic modulation characteristics caused by the damage of the electro-optic thin film layer. In addition, by bonding the first waveguide core substrate to bonding platforms with different structures, electro-optic modulation devices with different performances can be obtained, which can add electro-optic modulation functions and application scenarios to the bonding platform.

[0014] In an optional implementation manner, the bonding platform is a second waveguide core substrate;

[0015] The step of providing the bonding platform includes:

[0016] Provide a second substrate, and sequentially form a first cladding layer, a second waveguide core, and a second cladding layer on one surface of the second substrate; the second cladding layer covers the surface and sides of the second waveguide core;

[0017] On the surface of the second cladding layer facing away from the second waveguide core, a transition waveguide core and a second bonding dielectric layer are sequentially formed to form a second waveguide core substrate; the second bonding dielectric layer covers the surface and sides of the transition waveguide core; the projection of the second waveguide core on the second substrate partially overlaps with the projection of the transition waveguide core on the second substrate to form a second transition structure;

[0018] The steps of bringing the electro-optic thin film layer of the first waveguide core substrate into contact with the bonding platform and bonding them together include:

[0019] Bring the electro-optic thin film layer of the first waveguide core substrate into corresponding contact with the second bonding dielectric layer of the second waveguide core substrate and bond them together; the projection of the electro-optic thin film layer on the second substrate at least covers part of the projection of the transition waveguide core on the second substrate;

[0020] In the step of forming the first waveguide core, the projection of the first waveguide core on the second substrate partially overlaps with the projection of the transition waveguide core on the second substrate to form a first transition structure.

[0021] The preparation method of the heterogeneous integrated electro-optic modulation device provided by the present invention can integrate the first waveguide core - electro-optic thin film layer composite waveguide core onto the waveguide platform where the second waveguide core is located by bonding the electro-optic thin film layer of the first waveguide core substrate to the second bonding dielectric layer of the second waveguide core substrate. After the optical signal propagated by the second waveguide core enters the first waveguide core - electro-optic thin film layer composite waveguide core through the transition waveguide core for electro-optic modulation, it then returns to the second waveguide core through the transition waveguide core, and other functions can be realized in the waveguide formed by the second waveguide core, which can reduce the loss during the optical signal transmission process and add electro-optic modulation functions and application scenarios to the second waveguide core substrate.

[0022] In an optional implementation manner, at least one end of the first waveguide core in the length direction includes a first tapered portion;

[0023] At least one end of the second waveguide core in the length direction includes a second tapered portion;

[0024] Both ends of the transition waveguide core in the length direction respectively include a third tapered portion and a fourth tapered portion; the region between the third tapered portion and the fourth tapered portion is an intermediate transition region;

[0025] The projection of the third tapered portion on the second substrate partially overlaps with the projection of the first tapered portion on the second substrate, and the third tapered portion and the first tapered portion form a first transition structure; the tapered directions of the third tapered portion and the first tapered portion are inverted;

[0026] The projection of the fourth tapered portion on the second substrate partially overlaps with the projection of the second tapered portion on the second substrate, and the fourth tapered portion and the second tapered portion form a second transition structure; the tapered directions of the fourth tapered portion and the second tapered portion are inverted;

[0027] In the step of correspondingly contacting and bonding the electro-optic thin film layer of the first waveguide core substrate with the second bonding dielectric layer of the second waveguide core substrate together, the projection of the electro-optic thin film layer on the second substrate at least covers the projection of the third tapered portion on the second substrate and the projection of a part of the intermediate transition region on the second substrate.

[0028] In the method for preparing a heterogeneous integrated electro-optic modulation device provided by the present invention, the projection of the third tapered portion on the second substrate overlaps with the projection of the first tapered portion on the second substrate partially to form a first transition structure; the tapered directions of the third tapered portion and the first tapered portion are inverted; the projection of the fourth tapered portion on the second substrate overlaps with the projection of the second tapered portion on the second substrate partially to form a second transition structure; the tapered directions of the fourth tapered portion and the second tapered portion are inverted; efficient optical field transition can be achieved, and the loss during the optical signal transmission process can be reduced.

[0029] In an alternative embodiment, the heterogeneous integrated electro-optic modulation device includes at least one first waveguide core, at least two transition waveguide cores, and at least two second waveguide cores; both ends of the first waveguide core in the length direction respectively include a first tapered portion;

[0030] One transition waveguide core is respectively arranged at both ends of each first waveguide core in the length direction; the third tapered portion of each transition waveguide core and the first tapered portion form a first transition structure;

[0031] The second waveguide core is located on one side of the fourth tapered portion of the transition waveguide core, and the fourth tapered portion of each transition waveguide core and the second tapered portion form a second transition structure.

[0032] In the method for preparing a heterogeneous integrated electro-optic modulation device provided by the present invention, there is one first transition structure at each end of at least one first waveguide core, and the transition waveguide core in this first transition structure further forms a second transition structure with each of the two second waveguide cores; therefore, the optical signal propagated by one of the second waveguide cores in this structure can enter the first waveguide core - electro-optic thin film layer composite waveguide core successively via a second transition structure and a first transition structure. At the other end of the first waveguide core - electro-optic thin film layer composite waveguide core, the optical signal reaches the other second waveguide core successively via another first transition structure and another second transition structure, and other functions can be realized in the waveguide formed by the two second waveguide cores, the loss during the optical signal transmission process can be reduced, and the electro-optic modulation function and application scenarios can be added to the second waveguide core substrate.

[0033] In an alternative embodiment, the heterogeneous integrated electro-optic modulation device includes one first waveguide core, two transition waveguide cores, and two second waveguide cores;

[0034] The two transition waveguide cores are respectively located at both ends of the first waveguide core in the length direction; the two second waveguide cores are respectively located on one side of the fourth tapered portions of the two transition waveguide cores.

[0035] In an alternative embodiment, the bonding platform does not include a waveguide;

[0036] The steps of providing the bonding platform include:

[0037] Providing a third substrate;

[0038] Forming a third cladding layer on the third substrate;

[0039] The steps of bringing the electro-optic thin film layer of the first waveguide core substrate into contact with the bonding platform and bonding them together include:

[0040] Bringing the electro-optic thin film layer of the first waveguide core substrate into corresponding contact with the third cladding layer and bonding them together.

[0041] In an alternative embodiment, the first waveguide core and the electro-optic thin film layer form a composite waveguide core;

[0042] The process for forming the first waveguide core layer is a deposition process; the first waveguide core layer is a stoichiometric silicon nitride thin film or a stack of stoichiometric silicon nitride thin film - silicon dioxide thin film - stoichiometric silicon nitride thin film;

[0043] The process for forming the first bonding dielectric layer is a deposition process; the first bonding dielectric layer is a silicon dioxide thin film, an aluminum oxide thin film, or a stack of silicon dioxide thin film - aluminum oxide thin film;

[0044] The process for forming the electro-optic thin film layer is an intelligent ion cutting process or a wafer thinning process; the material of the electro-optic thin film layer is lithium niobate, lithium tantalate, or barium titanate;

[0045] The material of the first substrate is silicon;

[0046] The material of the buried layer is silicon dioxide; the thickness of the buried layer is 0.1 μm to 2 μm;

[0047] The thickness of the first waveguide core layer is 100 nm to 500 nm;

[0048] The thickness of the first bonding dielectric layer is 10 nm to 300 nm;

[0049] The thickness of the electro-optic thin film layer is 100 nm to 500 nm.

[0050] The preparation method of the heterogeneous integrated electro-optic modulation device provided by the present invention forms the first waveguide core layer as a stoichiometric silicon nitride thin film or a stack of stoichiometric silicon nitride thin film - silicon dioxide thin film - stoichiometric silicon nitride thin film through a deposition process; compared with non-stoichiometric silicon nitride (SiN x) A thin film, a stoichiometric silicon nitride (Si 3 N 4 ) thin film has very low optical propagation loss and can reduce the insertion loss of an electro-optic modulation device.

[0051] In an alternative embodiment, the process for forming the first waveguide core layer is a low-pressure chemical vapor deposition process; the first waveguide core layer is a stoichiometric silicon nitride thin film;

[0052] The first waveguide core is a stoichiometric silicon nitride core;

[0053] The electro-optic thin film layer is a lithium niobate thin film;

[0054] The stoichiometric silicon nitride core and the lithium niobate thin film form a silicon nitride-lithium niobate composite waveguide core.

[0055] The method for manufacturing a heterogeneous integrated electro-optic modulation device provided by the present invention forms the first waveguide core layer through a low-pressure chemical vapor deposition process, and then forms the first waveguide core. The first waveguide core is a stoichiometric silicon nitride core, and the stoichiometric silicon nitride core and the lithium niobate thin film form a silicon nitride-lithium niobate composite waveguide core. Since the stoichiometric silicon nitride waveguide core has very low optical propagation loss, the obtained silicon nitride-lithium niobate composite waveguide core also has low optical propagation loss and can reduce the insertion loss of the electro-optic modulation device. In addition, the method for manufacturing a heterogeneous integrated electro-optic modulation device provided by the present invention can form a stoichiometric silicon nitride waveguide core above the lithium niobate thin film on the premise that the lithium niobate thin film does not withstand high-temperature processes.

[0056] In an alternative embodiment, the refractive index of the second waveguide core is greater than the refractive indices of the first cladding and the second cladding;

[0057] The refractive index of the transition waveguide core is greater than the refractive index of the electro-optic thin film layer;

[0058] The material of the second substrate is silicon;

[0059] The material of the first cladding is silicon dioxide;

[0060] The material of the second cladding is silicon dioxide;

[0061] The material of the second bonding dielectric layer is one or more of silicon dioxide, aluminum oxide, and bonding glue;

[0062] The thickness of the first cladding is 2 μm to 20 μm;

[0063] The thickness of the second cladding above the second waveguide core is 0.1 μm to 1.5 μm; the thickness of the second bonding dielectric layer above the transition waveguide core is 0.2 μm to 1.5 μm.

[0064] In an alternative embodiment, the second waveguide core is one layer of silicon thin film or silicon nitride thin film, or a multi-layer structure composed of them and silicon dioxide thin film;

[0065] The material of the transition waveguide core is silicon-rich silicon nitride or silicon.

[0066] In a second aspect, the present invention provides a heterogeneous integrated electro-optic modulation device, which includes:

[0067] A bonding platform;

[0068] An electro-optic thin film layer located on one surface of the bonding platform;

[0069] A first bonding dielectric layer located on the surface of the electro-optic thin film layer facing away from the bonding platform;

[0070] A first waveguide core located on a partial surface of the first bonding dielectric layer facing away from the electro-optic thin film layer, exposing a part of the first bonding dielectric layer;

[0071] A buried layer located on the surface of the first waveguide core facing away from the first bonding dielectric layer;

[0072] An electrode on the surface of the first bonding dielectric layer on the side of the first waveguide core.

[0073] The heterogeneous integrated electro-optic modulation device provided by the present invention is prepared by the above-mentioned preparation method of the heterogeneous integrated electro-optic modulation device, which can improve the thickness uniformity and flatness of the first bonding dielectric layer, improve the uniformity of the electro-optic modulation device and the bonding strength of the electro-optic thin film layer, and further improve the reliability of the heterogeneous integrated device. It can alleviate problems such as poor uniformity of electro-optic modulation characteristics and low bonding strength of the electro-optic thin film layer caused by uneven thickness and poor flatness of the bonding dielectric layer; at the same time, it can also improve the reliability of the electro-optic thin film layer, and further improve the reliability of the heterogeneous integrated device. In addition, the first waveguide core - electro-optic thin film layer composite waveguide core is bonded to bonding platforms with different structures, and electro-optic modulation devices with different performances can be obtained, which can add electro-optic modulation functions and application scenarios to the bonding platform.

[0074] In an alternative embodiment, the bonding platform is a second waveguide core substrate;

[0075] The second waveguide core substrate includes a second substrate, a first cladding layer, a second waveguide core, a second cladding layer, a transition waveguide core, and a second bonding dielectric layer stacked in sequence; the second cladding layer covers the surface and sides of the second waveguide core; the second bonding dielectric layer covers the surface and sides of the transition waveguide core;

[0076] The second waveguide core substrate is located on the surface of the electro-optic thin film layer facing away from the first bonding dielectric layer; wherein, the second bonding dielectric layer is in contact with the electro-optic thin film layer; the projection of the electro-optic thin film layer on the second substrate at least covers a part of the projection of the transition waveguide core on the second substrate;

[0077] The projection of the first waveguide core on the second substrate overlaps partially with the projection of the transition waveguide core on the second substrate; the projection of the second waveguide core on the second substrate overlaps partially with the projection of the transition waveguide core on the second substrate.

[0078] In an alternative embodiment, the heterogeneous integrated electro-optic modulation device includes at least one first waveguide core, at least two transition waveguide cores, and at least two second waveguide cores;

[0079] Both ends of the first waveguide core in the length direction respectively include a first tapered portion; at least one end of the second waveguide core in the length direction includes a second tapered portion; both ends of the transition waveguide core in the length direction respectively include a third tapered portion and a fourth tapered portion; the region between the third tapered portion and the fourth tapered portion is an intermediate transition region;

[0080] One transition waveguide core is respectively arranged at both ends of each first waveguide core in the length direction; the third tapered portion of each transition waveguide core and the first tapered portion form a first transition structure;

[0081] The second waveguide core is located on one side of the fourth tapered portion of the transition waveguide core, and the fourth tapered portion of each transition waveguide core and the second tapered portion form a second transition structure;

[0082] The projection of the electro-optic thin film layer on the second substrate at least covers the projection of the third tapered portion on the second substrate and the projection of a part of the intermediate transition region on the second substrate. Description of the Drawings

[0083] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the related art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the related art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0084] Figure 1 is a schematic flowchart of a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0085] Figure 2 is a schematic structural diagram of a first substrate in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0086] Figure 3 is a schematic structural diagram of forming a buried layer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0087] Figure 4It is a schematic structural diagram of forming a first waveguide core layer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0088] Figure 5 It is a schematic structural diagram of forming a first bonding dielectric layer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0089] Figure 6 It is a schematic structural diagram of forming an electro-optic thin film layer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0090] Figure 7A It is a top view schematic structural diagram of forming a second waveguide core and a first cladding layer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0091] Figure 7B It is in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention Figure 7A Cross-sectional view on the AA plane.

[0092] Figure 8A It is a top view schematic structural diagram of forming a transition waveguide core and a second bonding dielectric layer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0093] Figure 8B It is in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention Figure 8A Cross-sectional view on the AA plane.

[0094] Figure 9 It is a schematic structural diagram of bonding and connecting a first waveguide core substrate and a second waveguide core substrate together in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0095] Figure 10A It is a top view schematic structural diagram of removing a first substrate in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0096] Figure 10B It is in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention Figure 10A Cross-sectional view on the BB plane.

[0097] Figure 11A It is a top view schematic structural diagram of forming a first waveguide core in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0098] Figure 11B It is in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention Figure 11ACross-sectional view of the BB surface.

[0099] Figure 11C It is in the method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention Figure 11A Cross-sectional view of the CC surface.

[0100] Figure 12A It is a top-down schematic view of the structure for forming an electrode in the method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0101] Figure 12B It is in the method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention Figure 12A Cross-sectional view of the CC surface.

[0102] Figure 13 It is a schematic flow chart of the method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0103] Figure 14 It is a top-down schematic view of the structure of a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0104] Figure 15 It is a cross-sectional schematic view of a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0105] Reference numerals:

[0106] 10. First substrate; 11. Buried layer; 12. First waveguide core layer; 120. First waveguide core; 13. First bonding dielectric layer; 14. Electro-optic thin film layer; 20. Second substrate; 21. First cladding layer; 22. Second waveguide core; 23. Second cladding layer; 24. Transition waveguide core; 25. Second bonding dielectric layer; 40. Electrode; 100. First waveguide core substrate; 200. Second waveguide core substrate. Detailed implementation manners

[0107] The present invention will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention are shown in the drawings, rather than all structures.

[0108] In the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of the present invention. Various structural schematic diagrams according to embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, where for the purpose of clear expression, certain details are enlarged and certain details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art can additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs. In the context of the present invention, when a layer / component is referred to as being "on" another layer / component, the layer / component can be directly on the other layer / component, or there can be an intermediate layer / component between them. Additionally, if a layer / component is "on" another layer / component in one orientation, then when the orientation is reversed, the layer / component can be "under" the other layer / component.

[0109] The stoichiometric silicon nitride (Si 3 N 4 ) thin film / waveguide core prepared by low-pressure chemical vapor deposition (LPCVD) uses a wafer-level manufacturing process and has advantages such as transparency in a wide wavelength range (400–2350 nm), low optical propagation loss at high optical power, etc. A waveguide platform composed of a silicon nitride waveguide core on a silicon (Si) substrate and a silica (SiO 2 ) cladding enables a wide range of planar integrated devices and chip-level solutions.

[0110] The phase modulator is one of the core devices of a photonic integrated circuit. Photonic platforms based on silicon nitride can generally use the thermo-optic effect, the stress-optic effect, etc. to achieve optical phase modulation. However, limited by material properties such as the heat conduction speed and charge / discharge time, and device structure limitations, these modulators still have deficiencies in terms of speed, power, and modulation efficiency. A popular alternative is electro-optic modulation, but the electro-optic effect of silicon nitride is very weak and must be combined with materials having a significant electro-optic effect to achieve efficient electro-optic phase modulation. Among them, the ferroelectric material single crystal lithium niobate (LiNbO 3 ) has a strong electro-optic effect (1550 nm: r 33 = 27 pm / V), a relatively large refractive index (1550 nm: n o = 2.21, n e = 2.14), a wide light transmission window (400 nm to 5 μm), and stable physical and chemical properties, making it the most competitive material.

[0111] Due to the large difference in thermal expansion coefficients between lithium niobate and silicon and silicon dioxide, the lithium niobate thin film will crack due to high thermal stress at high temperatures. Therefore, it is impossible to deposit a silicon nitride thin film on the surface of the lithium niobate thin film on a silicon substrate by LPCVD. In addition, the metal elements contained in lithium niobate will potentially contaminate complementary metal oxide semiconductor (CMOS) process equipment, and the etching of lithium niobate is relatively difficult. Existing technical solutions form a composite waveguide and an electro-optic modulation device through the heterogeneous integration of a silicon nitride waveguide core and a lithium niobate thin film. Specifically, the lithium niobate thin film is bonded above a stoichiometric silicon nitride waveguide core to form a lithium niobate-silicon nitride composite waveguide or an electro-optic modulation device. However, this solution requires a thin (typical thickness ~100 nm), flat, and uniform bonding dielectric layer between the lithium niobate thin film and the patterned stoichiometric silicon nitride. This bonding dielectric layer is usually controlled by a chemical mechanical polishing (CMP) process, and the process is difficult. It will result in uneven thickness and poor flatness of the bonding dielectric layer, and further lead to poor uniformity of the heterogeneous integrated electro-optic modulation device and low bonding strength of the lithium niobate thin film.

[0112] In the existing technical solution, the bonding dielectric layer is covered above the waveguide core after the patterned silicon nitride waveguide core is formed. This causes the surface of the bonding dielectric layer to be uneven, and it is necessary to use a chemical mechanical polishing (CMP) process (to gradually reduce the height difference between the convex and concave parts of the thin film through chemical and mechanical actions) to polish the surface of the bonding dielectric layer to meet the flatness required for bonding. First, since the thickness of the deposited bonding dielectric layer is larger than the thickness of the waveguide core to ensure that the bonding layer completely covers the waveguide core and there is still a sufficient thickness (typical ~100 nm) of the bonding dielectric layer above the waveguide core after planarization; in addition, the thickness of the bonding layer above different waveguide cores should be as the same as possible (related to the uniformity of the characteristics of different electro-optic modulation devices), and it is relatively difficult to control the thickness of the bonding dielectric layer (thinning to a specified thickness) by CMP. Usually, the thickness of the bonding dielectric layer above several structures with the same film layer structure as that at the waveguide core but outside the waveguide core region is monitored to indirectly reflect the thickness of the bonding layer above the waveguide core, and there is a certain error, and the uniformity is difficult to guarantee.

[0113] As Figure 1 shown, this embodiment provides a method for fabricating a heterogeneous integrated electro-optic modulation device, and the fabrication method includes but is not limited to steps S101 to S107.

[0114] Step S101, provide a first substrate 10, and sequentially form a buried layer 11, a first waveguide core layer 12, and a first bonding dielectric layer 13 on one side surface of the first substrate 10, as Figures 2 - 5 shown.

[0115] In specific implementation, a first waveguide core layer 12 can be formed on the surface of the buried layer 11 through a deposition process. The first waveguide core layer 12 can be a stoichiometric silicon nitride thin film or a stack of a stoichiometric silicon nitride thin film - a silicon dioxide thin film - a stoichiometric silicon nitride thin film. Since the first waveguide core layer 12 is a whole-surface thin film, forming a first bonding dielectric layer 13 on the whole-surface first waveguide core layer 12 can improve the thickness uniformity and flatness of the first bonding dielectric layer 13.

[0116] Step S102: Perform a chemical mechanical polishing process on the surface of the first bonding dielectric layer 13 on the side facing away from the first waveguide core layer 12.

[0117] In specific implementation, in the chemical mechanical polishing process, since the lower layer of the first bonding dielectric layer 13 is the whole-surface first waveguide core layer 12, the difficulty of the CMP process can be reduced, and the thickness uniformity and flatness of the first bonding dielectric layer 13 can be improved.

[0118] Step S103: Form an electro-optic thin film layer 14 on the surface of the first bonding dielectric layer 13 on the side facing away from the first waveguide core layer 12 to form a first waveguide core substrate 100, as Figure 6 shown.

[0119] Step S104: Provide a bonding platform.

[0120] In specific implementation, the bonding platform can be a wafer that contains or does not contain other waveguides.

[0121] Step S105: Bring the electro-optic thin film layer 14 of the first waveguide core substrate 100 into contact with the bonding platform and bond them together, as Figure 9 shown.

[0122] Step S106: Remove the first substrate 10. On the side of the buried layer 11 facing away from the first waveguide core layer 12, perform a patterning process on the buried layer 11 and the first waveguide core layer 12 to form a first waveguide core 120, exposing a part of the first bonding dielectric layer 13.

[0123] In specific implementation, as Figure 11A , Figure 11B , and Figure 11C shown, after the patterning process, the shape of the first waveguide core 120 is the same as that of the buried layer 11 above it, and the first waveguide core 120 and the electro-optic thin film layer 14 form a first waveguide core - electro-optic thin film layer composite waveguide core.

[0124] Step S107: Form an electrode 40 on the surface of the first bonding dielectric layer 13 on the side of the first waveguide core 120, as Figure 12A and Figure 12B shown.

[0125] The preparation method of the heterogeneous integrated electro-optic modulation device provided by this embodiment, on the one hand, forms a first bonding dielectric layer on the entire first waveguide core layer. Performing a chemical mechanical polishing process on the first bonding dielectric layer can reduce the difficulty of the chemical mechanical polishing process, improve the thickness uniformity and flatness of the first bonding dielectric layer, improve the uniformity of the heterogeneous integrated electro-optic modulation device and the bonding strength of the electro-optic thin film layer, and further improve the stability and reliability of the heterogeneous integrated electro-optic modulation device; it can alleviate problems such as poor uniformity of electro-optic modulation characteristics and low bonding strength of the electro-optic thin film layer caused by uneven thickness and poor flatness of the bonding dielectric layer. On the other hand, after bonding and connecting the first waveguide core substrate to the bonding platform, a patterned first waveguide core is formed, and a composite waveguide core of the first waveguide core - electro-optic thin film layer can be formed. The first bonding dielectric layer can be used as a protective layer during the etching of the first waveguide core layer to avoid etching damage to the electro-optic thin film layer, and avoid the increase in light propagation loss and poor uniformity of electro-optic modulation characteristics caused by damage to the electro-optic thin film layer. In addition, by bonding the first waveguide core substrate to bonding platforms with different structures, electro-optic modulation devices with different performances can be obtained, and electro-optic modulation functions and application scenarios can be added to the bonding platform.

[0126] In some alternative embodiments, the heterogeneous integrated electro-optic modulation device is an electro-optic modulator based on a composite waveguide core composed of a first waveguide core and an electro-optic thin film layer.

[0127] In some alternative embodiments, the bonding platform is a second waveguide core substrate 200;

[0128] The steps of providing the bonding platform include:

[0129] Provide a second substrate 20, and sequentially form a first cladding layer 21, a second waveguide core 22, and a second cladding layer 23 on one side surface of the second substrate 20; the second cladding layer 23 covers the surface and sides of the second waveguide core 22;

[0130] Sequentially form a transition waveguide core 24 and a second bonding dielectric layer 25 on the surface of the second cladding layer 23 facing away from the second waveguide core 22 to form a second waveguide core substrate 200; the second bonding dielectric layer 25 covers the surface and sides of the transition waveguide core 24; the projection of the second waveguide core 22 on the second substrate 20 overlaps partially with the projection of the transition waveguide core 24 on the second substrate 20 to form a second transition structure;

[0131] The steps of bringing the electro-optic thin film layer 14 of the first waveguide core substrate 100 into contact with the bonding platform and bonding and connecting them together include:

[0132] The electro-optic thin film layer 14 of the first waveguide core substrate 100 is brought into corresponding contact with the second bonding dielectric layer 25 of the second waveguide core substrate 200 and bonded together; the projection of the electro-optic thin film layer 14 on the second substrate 20 at least covers the projection of at least a part of the transition waveguide core 24 on the second substrate 20.

[0133] In the step of forming the first waveguide core 120, the projection of the first waveguide core 120 on the second substrate 20 partially overlaps with the projection of the transition waveguide core 24 on the second substrate 20, forming a first transition structure.

[0134] In the method for manufacturing a heterogeneous integrated electro-optic modulation device provided in this embodiment, by bonding the electro-optic thin film layer of the first waveguide core substrate to the second bonding dielectric layer of the second waveguide core substrate, the first waveguide core - electro-optic thin film layer composite waveguide core can be integrated onto the waveguide platform where the second waveguide core is located. The optical signal propagated by the second waveguide core enters the first waveguide core - electro-optic thin film layer composite waveguide core through the transition waveguide core for electro-optic modulation, and then returns to the second waveguide core through the transition waveguide core, and other functions can be realized in the waveguide formed by the second waveguide core, which can reduce the loss during the optical signal transmission process and add electro-optic modulation functions and application scenarios to the second waveguide core substrate.

[0135] In some optional embodiments, at least one end of the first waveguide core 120 in the length direction includes a first tapered portion;

[0136] At least one end of the second waveguide core 22 in the length direction includes a second tapered portion;

[0137] Both ends of the transition waveguide core 24 in the length direction respectively include a third tapered portion and a fourth tapered portion; the region between the third tapered portion and the fourth tapered portion is an intermediate transition region;

[0138] The projection of the third tapered portion on the second substrate 20 partially overlaps with the projection of the first tapered portion on the second substrate 20, and the third tapered portion and the first tapered portion form a first transition structure; the tapered directions of the third tapered portion and the first tapered portion are inverted.

[0139] The projection of the fourth tapered portion on the second substrate 20 partially overlaps with the projection of the second tapered portion on the second substrate 20, and the fourth tapered portion and the second tapered portion form a second transition structure; the tapered directions of the fourth tapered portion and the second tapered portion are inverted.

[0140] In the step of bringing the electro-optic thin film layer 14 of the first waveguide core substrate 100 into corresponding contact with the second bonding dielectric layer 25 of the second waveguide core substrate 200 and bonding them together, the projection of the electro-optic thin film layer 14 on the second substrate 20 at least covers the projection of the third tapered portion on the second substrate 20 and the projection of a part of the intermediate transition region on the second substrate 20.

[0141] In specific implementation, the inverted conical direction of the third conical part and the first conical part means that when the width of the third conical part gradually narrows, the width of the first conical part gradually widens, and when the width of the third conical part gradually widens, the width of the first conical part gradually narrows (that is, the tips of the third conical part and the first conical part face each other). The inversion of other conical parts is in the same way.

[0142] In the preparation method of the heterogeneous integrated electro-optic modulation device provided in this embodiment, the projection of the third conical part on the second substrate overlaps with the projection of the first conical part on the second substrate to form a first transition structure; the conical directions of the third conical part and the first conical part are inverted; the projection of the fourth conical part on the second substrate overlaps with the projection of the second conical part on the second substrate to form a second transition structure; the conical directions of the fourth conical part and the second conical part are inverted; efficient optical field transition can be achieved, and the loss during the optical signal transmission process can be reduced.

[0143] In some alternative embodiments, the heterogeneous integrated electro-optic modulation device includes at least one first waveguide core 120, at least two transition waveguide cores 24, and at least two second waveguide cores 22; both ends of the first waveguide core 120 in the length direction respectively include first conical parts;

[0144] One transition waveguide core 24 is respectively arranged at both ends of each first waveguide core 120 in the length direction; the third conical part of each transition waveguide core 24 and the first conical part form a first transition structure;

[0145] The second waveguide core 22 is located on one side of the fourth conical part of the transition waveguide core 24, and the fourth conical part of each transition waveguide core 24 and the second conical part form a second transition structure.

[0146] In the preparation method of the heterogeneous integrated electro-optic modulation device provided in this embodiment, there is one first transition structure at each end of at least one first waveguide core, and the transition waveguide core in this first transition structure forms a second transition structure with each of the two second waveguide cores; therefore, the optical signal propagated by one of the second waveguide cores in this structure can sequentially enter the first waveguide core - electro-optic thin film layer composite waveguide core via one second transition structure and one first transition structure. At the other end of the first waveguide core - electro-optic thin film layer composite waveguide core, the optical signal sequentially reaches the other second waveguide core via the other first transition structure and the other second transition structure, and other functions can be realized in the waveguide composed of the two second waveguide cores, which can reduce the loss during the optical signal transmission process and add electro-optic modulation functions and application scenarios to the second waveguide core substrate.

[0147] In some alternative embodiments, the heterogeneous integrated electro-optic modulation device includes a first waveguide core 120, two transition waveguide cores 24, and two second waveguide cores 22;

[0148] The two transition waveguide cores 24 are respectively located at both ends of the first waveguide core 120 in the length direction; the two second waveguide cores 22 are respectively located on one side of the fourth tapered portions of the two transition waveguide cores 24;

[0149] In the step of vertically aligning and bonding the first waveguide core substrate 100 and the second waveguide core substrate 200 together, the projection of the electro-optic thin film layer 14 on the second substrate 20 covers a part of the projection of the transition waveguide core 24 on the second substrate 20.

[0150] In some alternative embodiments, the intermediate transition region of the transition waveguide core 24 is an equal-width portion, and the third tapered portion and the fourth tapered portion are portions with gradually decreasing widths at both ends.

[0151] The first waveguide core 120 further includes an equal-width portion between the first tapered portions at both ends, and the first tapered portions are portions with gradually decreasing widths;

[0152] The second waveguide core 22 further includes an equal-width portion other than the second tapered portion, and the second tapered portion is a portion with gradually decreasing width at at least one end.

[0153] In some alternative embodiments, the bonding platform does not include a waveguide;

[0154] The steps of providing the bonding platform include:

[0155] Providing a third substrate;

[0156] Forming a third cladding on the third substrate;

[0157] The steps of bringing the electro-optic thin film layer 14 of the first waveguide core substrate 100 into contact with the bonding platform and bonding them together include:

[0158] Bringing the electro-optic thin film layer 14 of the first waveguide core substrate 100 into corresponding contact with the third cladding and bonding them together.

[0159] In some alternative embodiments, the first waveguide core 120 and the electro-optic thin film layer 14 form a composite waveguide core;

[0160] The process of forming the first waveguide core layer 12 is a deposition process; the first waveguide core layer 12 is a stoichiometric silicon nitride thin film or a stack of stoichiometric silicon nitride thin film - silicon dioxide thin film - stoichiometric silicon nitride thin film;

[0161] The process of forming the first bonding dielectric layer 13 is a deposition process; the first bonding dielectric layer 13 is a silicon dioxide thin film, an aluminum oxide thin film, or a silicon dioxide thin film-aluminum oxide thin film stack;

[0162] The process of forming the electro-optic thin film layer 14 is an intelligent ion cutting process or a wafer thinning process; the material of the electro-optic thin film layer 14 is lithium niobate, lithium tantalate, or barium titanate;

[0163] The material of the first substrate 10 is silicon;

[0164] The material of the buried layer 11 is silicon dioxide; the thickness of the buried layer 11 is 0.1 μm to 2 μm;

[0165] The thickness of the first waveguide core layer 12 is 100 nm to 500 nm;

[0166] The thickness of the first bonding dielectric layer 13 is 10 nm to 300 nm;

[0167] The thickness of the electro-optic thin film layer 14 is 100 nm to 500 nm.

[0168] The preparation method of the heterogeneous integrated electro-optic modulation device provided by the present invention forms the first waveguide core layer as a stoichiometric silicon nitride thin film or a stoichiometric silicon nitride thin film-silicon dioxide thin film-stoichiometric silicon nitride thin film stack through a deposition process; compared with a non-stoichiometric silicon nitride (SiN x ) thin film, the stoichiometric silicon nitride (Si 3 N 4 ) thin film has very low optical propagation loss and can reduce the insertion loss of the electro-optic modulation device.

[0169] In some alternative embodiments, the process of forming the first waveguide core layer 12 is a low-pressure chemical vapor deposition process; the first waveguide core layer 12 is a stoichiometric silicon nitride thin film;

[0170] The first waveguide core 120 is a stoichiometric silicon nitride core;

[0171] The electro-optic thin film layer 14 is a lithium niobate thin film;

[0172] The stoichiometric silicon nitride core and the lithium niobate thin film form a silicon nitride-lithium niobate composite waveguide core.

[0173] The manufacturing method of the heterogeneous integrated electro-optic modulation device provided in this embodiment forms the first waveguide core layer through a low-pressure chemical vapor deposition process, and then forms the first waveguide core. The first waveguide core is a stoichiometric silicon nitride core. The stoichiometric silicon nitride core and the lithium niobate thin film form a silicon nitride-lithium niobate composite waveguide core. Since the stoichiometric silicon nitride waveguide core has very low optical propagation loss, the obtained silicon nitride-lithium niobate composite waveguide core also has low optical propagation loss, which can reduce the insertion loss of the electro-optic modulation device. In addition, the manufacturing method of the heterogeneous integrated electro-optic modulation device provided in this embodiment can form a stoichiometric silicon nitride waveguide core above the lithium niobate thin film without the lithium niobate thin film being subjected to high-temperature processes.

[0174] In some alternative embodiments, the refractive index of the second waveguide core 22 is greater than the refractive indices of the first cladding layer 21 and the second cladding layer 23;

[0175] The refractive index of the transition waveguide core 24 is greater than the refractive index of the electro-optic thin film layer 14;

[0176] The material of the second substrate 20 is silicon;

[0177] The material of the first cladding layer 21 is silicon dioxide;

[0178] The material of the second cladding layer 23 is silicon dioxide;

[0179] The material of the second bonding dielectric layer 25 is one or more of silicon dioxide, alumina, and bonding glue;

[0180] The thickness of the first cladding layer 21 and the third cladding layer is 2 μm to 20 μm;

[0181] The thickness of the second cladding layer 23 above the second waveguide core 22 is 0.1 μm to 1.5 μm; the thickness of the second bonding dielectric layer 25 above the transition waveguide core 24 is 0.2 μm to 1.5 μm.

[0182] In some alternative embodiments, the second waveguide core 22 is one layer of silicon thin film, silicon nitride thin film, or a multi-layer composed of it and silicon dioxide thin film;

[0183] The material of the transition waveguide core 24 is silicon-rich silicon nitride or silicon.

[0184] In some alternative embodiments, the material of the third cladding layer is silicon dioxide.

[0185] As Figure 13 shown, the present invention also provides a specific process schematic diagram of a manufacturing method of a heterogeneous integrated electro-optic modulation device, including but not limited to steps S201 to S209.

[0186] Step S201, provide a first substrate 10, as Figure 2As shown, a buried layer 11, a first waveguide core layer 12, and a first bonding dielectric layer 13 are sequentially formed on one side surface of the first substrate 10; as Figures 3 - 5 shown.

[0187] In specific implementation, first, a buried layer 11 is formed on one side surface of the first substrate 10. As Figure 3 shown, the material of the first substrate 10 is silicon, the material of the buried layer 11 is silicon dioxide, and the thickness of the buried layer 11 is 0.1 μm to 2 μm; for example, a silicon dioxide thin film is obtained by thermal oxidation of the first substrate 10. Secondly, a first waveguide core layer 12 is formed on the side surface of the buried layer 11 facing away from the first substrate 10. As Figure 4 shown, the process of forming the first waveguide core layer 12 is a deposition process; the first waveguide core layer 12 is a stoichiometric silicon nitride thin film or a stack of stoichiometric silicon nitride thin film - silicon dioxide thin film - stoichiometric silicon nitride thin film; the thickness of the first waveguide core layer 12 is 100 nm to 500 nm. Finally, a first bonding dielectric layer 13 is formed on the side surface of the first waveguide core layer 12 facing away from the buried layer 11. As Figure 5 shown, the process of forming the first bonding dielectric layer 13 is a deposition process; the first bonding dielectric layer 13 is a silicon dioxide thin film, an aluminum oxide thin film, or a stack of silicon dioxide thin film - aluminum oxide thin film; the thickness of the first bonding dielectric layer 13 is 10 nm to 300 nm.

[0188] In one example, the process of forming the first waveguide core layer 12 is a low-pressure chemical vapor deposition process; the first waveguide core layer 12 is a stoichiometric silicon nitride thin film; the process of forming the first bonding dielectric layer 13 is a low-pressure chemical vapor deposition process, for example, a silicon dioxide thin film deposited by a low-pressure chemical vapor deposition process.

[0189] In one example, an aluminum oxide thin film is deposited on the surface of a flat silicon dioxide thin film by atomic layer deposition process, and the two together form the first bonding dielectric layer 13.

[0190] Step S202, perform a chemical mechanical polishing process on the side surface of the first bonding dielectric layer 13 facing away from the first waveguide core layer 12.

[0191] Step S203, form an electro-optic thin film layer 14 on the side surface of the first bonding dielectric layer 13 facing away from the first waveguide core layer 12, and form a first waveguide core substrate 100. As Figure 6 shown;

[0192] In specific implementation, the process of forming the electro-optic thin film layer 14 is an intelligent ion cutting process or a wafer thinning process; the material of the electro-optic thin film layer 14 is an electro-optic crystal material such as lithium niobate, lithium tantalate, or barium titanate; the thickness of the electro-optic thin film layer 14 is 100 nm to 500 nm.

[0193] In one example, the electro-optic thin film layer 14 is a lithium niobate thin film.

[0194] Step S204: Provide a second substrate 20, and sequentially form a first cladding layer 21, a second waveguide core 22, and a second cladding layer 23 on one side surface of the second substrate 20; the second cladding layer 23 covers the surface and sides of the second waveguide core 22, as Figure 7A and Figure 7B shown.

[0195] Specifically, the material of the first substrate 10 is silicon; the material of the first cladding layer 21 is silicon dioxide; the material of the second cladding layer 23 is silicon dioxide; the second waveguide core 22 is one layer of a silicon thin film or a silicon nitride thin film or a multi-layer structure composed of it and a silicon dioxide thin film; the thickness of the first cladding layer 21 is 2 μm to 20 μm; the thickness of the second cladding layer 23 located above the second waveguide core 22 is 0.1 μm to 1.5 μm. At least one end of the second waveguide core 22 in the length direction includes a second tapered portion; the second tapered portion is a portion where the width of the second waveguide core 22 gradually decreases. Figure 7A is a top view of the structure for forming the second waveguide core 22 and the second cladding layer 23, Figure 7B is Figure 7A a cross-sectional view taken along the AA plane.

[0196] Step S205: Sequentially form a transition waveguide core 24 and a second bonding dielectric layer 25 on the surface of the second cladding layer 23 facing away from the second waveguide core 22 to form a second waveguide core substrate 200; the second bonding dielectric layer 25 covers the surface and sides of the transition waveguide core 24; the projection of the second waveguide core 22 on the second substrate 20 partially overlaps with the projection of a part of the transition waveguide core 24 on the second substrate 20 to form a second transition structure, as Figure 8A and Figure 8B shown.

[0197] Specifically, the material of the transition waveguide core 24 is silicon-rich silicon nitride or silicon; the material of the second bonding dielectric layer 25 is one or more of silicon dioxide, alumina, and bonding glue; the thickness of the second bonding dielectric layer 25 located above the transition waveguide core 24 is 0.2 μm to 1.5 μm. Both ends of the transition waveguide core 24 in the length direction respectively include a third tapered portion and a fourth tapered portion; the region between the third tapered portion and the fourth tapered portion is an intermediate transition region, where the intermediate transition region is a constant-width portion, and the third tapered portion and the fourth tapered portion are portions where the width gradually decreases at both ends. The projection of the fourth tapered portion on the second substrate 20 partially overlaps with the projection of the second tapered portion on the second substrate 20 to form a second transition structure; the tapered directions of the fourth tapered portion and the second tapered portion are inverted. Figure 8A is a top view of the structure of the second waveguide core substrate 200, Figure 8B is Figure 8A a cross-sectional view taken along the AA plane.

[0198] In one example, the second waveguide core 22 and the transition waveguide core 24 forming the second transition structure are centered and aligned;

[0199] Step S206: The electro-optic thin film layer 14 of the first waveguide core substrate 100 is brought into corresponding contact with the second bonding dielectric layer 25 of the second waveguide core substrate 200 and bonded together, as Figure 9 shown; the projection of the electro-optic thin film layer 14 on the second substrate 20 at least covers the projection of at least part of the transition waveguide core 24 on the second substrate 20.

[0200] In specific implementation, the projection of the electro-optic thin film layer 14 on the second substrate 20 at least covers the projection of the third tapered portion on the second substrate 20 and the projection of part of the intermediate transition region on the second substrate 20.

[0201] In one example, the projection of the electro-optic thin film layer 14 on the second substrate 20 covers the projection of at least part of the transition waveguide core 24 on the second substrate 20.

[0202] Step S207: Remove the first substrate 10, as Figure 10A and Figure 10B shown.

[0203] In specific implementation, Figure 10A is a top view of the structure after removing the first substrate 10, Figure 10B is Figure 10A a cross-sectional view taken along the BB plane.

[0204] Step S208: On the side of the buried layer 11 facing away from the first waveguide core layer 12, a patterning process is performed on the buried layer 11 and the first waveguide core layer 12 to form the first waveguide core 120, exposing part of the first bonding dielectric layer 13, as Figure 11A , Figure 11B and Figure 11C shown; the projection of the electro-optic thin film layer 14 on the second substrate 20 covers the projection of the first waveguide core 120 on the second substrate 20; the projection of the first waveguide core 120 on the second substrate 20 partially overlaps with the projection of the transition waveguide core 24 on the second substrate 20, forming the first transition structure.

[0205] In specific implementation, the first waveguide core 120 and the electro-optic thin film layer 14 and the dielectric around them form a composite waveguide; both ends of the first waveguide core 120 in the length direction respectively include a first tapered portion, the first waveguide core 120 further includes an equal-width portion between the two first tapered portions at both ends, and the first tapered portion is a portion with a gradually decreasing width. The projection of the third tapered portion on the second substrate 20 partially overlaps with the projection of the first tapered portion on the second substrate 20, forming the first transition structure; the tapered directions of the third tapered portion and the first tapered portion are inverted. Figure 11ATop view of the structure after forming the first waveguide core Figure 11B is Figure 11A a cross-sectional view on the BB plane Figure 11B is a cross-sectional view of the first transition structure. It can be seen that the projection of the third tapered portion on the second substrate 20 overlaps with the projection of the first tapered portion on the second substrate 20 Figure 11C is Figure 11A a cross-sectional view on the CC plane

[0206] In one example, a stoichiometric silicon nitride core, a lithium niobate thin film, and the dielectric around them form a silicon nitride-lithium niobate composite waveguide

[0207] Step S209, forming an electrode 40 on the surface of the first bonding dielectric layer 13 on the side of the first waveguide core 120, as Figure 12A and Figure 12B shown

[0208] Specifically, electrodes 40 are respectively formed on the surfaces of the first bonding dielectric layer 13 on the two sides of the equal-width portion of the first waveguide core 120. The material of the electrodes 40 can be Au, Al, Cu, etc. The distance between the two electrodes 40 is 4-10 μm, and the thickness of the electrodes 40 is 0.5 μm-2 μm; as Figure 12B is Figure 12A a cross-sectional view on the CC plane

[0209] This embodiment also provides a heterogeneous integrated electro-optic modulation device, as Figure 14 and as Figure 15 shown. The heterogeneous integrated electro-optic modulation device includes

[0210] a bonding platform

[0211] an electro-optic thin film layer 14 located on one surface of the bonding platform

[0212] a first bonding dielectric layer 13 located on the surface of the electro-optic thin film layer 14 facing away from the bonding platform

[0213] a first waveguide core 120 located on a partial surface of the first bonding dielectric layer 13 facing away from the electro-optic thin film layer 14, exposing a part of the first bonding dielectric layer 13

[0214] a buried layer 11 located on the surface of the first waveguide core 120 facing away from the first bonding dielectric layer 13

[0215] an electrode 40 on the surface of the first bonding dielectric layer 13 on the side of the first waveguide core 120

[0216] The heterogeneous integrated electro-optic modulation device provided in this embodiment is prepared by the preparation method of the above heterogeneous integrated electro-optic modulation device, which can improve the thickness uniformity and flatness of the first bonding dielectric layer, improve the uniformity of the electro-optic modulation device and the bonding strength of the electro-optic thin film layer, and further improve the stability and reliability of the heterogeneous integrated device. It can alleviate problems such as poor uniformity of electro-optic modulation characteristics and low bonding strength of the electro-optic thin film layer caused by uneven thickness and poor flatness of the bonding dielectric layer. In addition, the first waveguide core - electro-optic thin film layer composite waveguide core is bonded to bonding platforms with different structures, which can increase the functions and application scenarios of the bonding platforms.

[0217] In some alternative embodiments, the bonding platform is the second waveguide core substrate 200;

[0218] The second waveguide core substrate 200 includes a second substrate 20, a first cladding layer 21, a second waveguide core 22, a second cladding layer 23, a transition waveguide core 24, and a second bonding dielectric layer 25 stacked in sequence; the second cladding layer 23 covers the surface and sides of the second waveguide core 22; the second bonding dielectric layer 25 covers the surface and sides of the transition waveguide core 24;

[0219] The second waveguide core substrate 200 is located on the surface of the electro-optic thin film layer 14 facing away from the first bonding dielectric layer 13; wherein, the second bonding dielectric layer 25 is in contact with the electro-optic thin film layer 14; the projection of the electro-optic thin film layer 14 on the second substrate 20 at least covers part of the projection of the transition waveguide core 24 on the second substrate 20;

[0220] The projection of the first waveguide core 120 on the second substrate 20 partially overlaps with the projection of the transition waveguide core 24 on the second substrate 20; the projection of the second waveguide core 22 on the second substrate 20 partially overlaps with the projection of the transition waveguide core 24 on the second substrate 20.

[0221] In some alternative embodiments, the heterogeneous integrated electro-optic modulation device includes at least one first waveguide core 120, at least two transition waveguide cores 24, and at least two second waveguide cores 22;

[0222] Both ends of the first waveguide core 120 in the length direction respectively include a first tapered portion; at least one end of the second waveguide core 22 in the length direction includes a second tapered portion; both ends of the transition waveguide core 24 in the length direction respectively include a third tapered portion and a fourth tapered portion; the region between the third tapered portion and the fourth tapered portion is an intermediate transition region;

[0223] One transition waveguide core 24 is respectively arranged at both ends of each first waveguide core 120 in the length direction; the third tapered portion of each transition waveguide core 24 and the first tapered portion form a first transition structure;

[0224] The second waveguide core 22 is located on one side of the fourth tapered portion of the transition waveguide core 24, and the fourth tapered portion and the second tapered portion of each transition waveguide core 24 form a second transition structure;

[0225] The projection of the electro-optic thin film layer 14 on the second substrate 20 at least covers the projection of the third tapered portion on the second substrate 20 and the projection of a part of the intermediate transition region on the second substrate 20.

[0226] In the description of this specification, the descriptions with reference to the terms "this embodiment", "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0227] In the above description, technical details such as the layout and etching of each layer are not elaborated in detail. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. of the required shapes. In addition, in order to form the same structure, those skilled in the art can also design methods that are not exactly the same as the methods described above. In addition, although the above embodiments are described separately, this does not mean that the measures in each embodiment cannot be used advantageously in combination.

[0228] The above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the above specific embodiments, and various obvious changes, re-adjustments, combinations with each other, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included. The protection scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing a heterogeneous integrated electro-optical modulation device, characterized in that: include: Providing a first substrate, and sequentially forming a buried layer, a first waveguide core layer, and a first bonding medium layer on a surface of one side of the first substrate; Performing a chemical mechanical polishing process on a surface of the first bonding medium layer facing away from the first waveguide core layer; forming an electro-optical thin film layer on a surface of the first bonding medium layer facing away from the first waveguide core layer to form a first waveguide core substrate; Provide bonding platform; The electro-optical thin film layer of the first waveguide core substrate is brought into contact with the bonding platform and bonded together; removing the first substrate, and performing a patterning process on the buried layer and the first waveguide core layer on a side of the buried layer facing away from the first waveguide core layer to form a first waveguide core, exposing a portion of the first bonding medium layer; An electrode is formed on a surface of the first bonding medium layer at a side portion of the first waveguide core.

2. The method for preparing a heterogeneous integrated electro-optical modulation device according to claim 1, characterized in that: The bonding platform is a second waveguide core substrate; The step of providing a bonding platform comprises: Providing a second substrate, and sequentially forming a first cladding, a second waveguide core, and a second cladding on a surface of one side of the second substrate; the second cladding covers the surface and side of the second waveguide core; A transition waveguide core and a second bonding medium layer are sequentially formed on the surface of the second cladding layer facing away from the second waveguide core to form a second waveguide core substrate; the second bonding medium layer covers the surface and side of the transition waveguide core; the projection of the second waveguide core on the second substrate partially overlaps with the projection of the transition waveguide core on the second substrate to form a second transition structure; The step of contacting and bonding the electro-optical thin film layer of the first waveguide core substrate to the bonding platform comprises: The electro-optical thin film layer of the first waveguide core substrate and the second bonding medium layer of the second waveguide core substrate are contacted and bonded together accordingly; the projection of the electro-optical thin film layer on the second substrate at least covers a portion of the projection of the transition waveguide core on the second substrate; In the step of forming the first waveguide core, the projection of the first waveguide core on the second substrate partially overlaps with the projection of the transition waveguide core on the second substrate to form a first transition structure.

3. The method for preparing a heterogeneous integrated electro-optical modulation device according to claim 2, characterized in that: The first waveguide core comprises a first tapered portion at at least one end in the length direction; The second waveguide core comprises a second tapered portion at at least one end in the length direction; The transition waveguide core comprises a third tapered portion and a fourth tapered portion at both ends in the length direction respectively; the area between the third tapered portion and the fourth tapered portion is an intermediate transition area; The projection of the third tapered portion on the second substrate partially overlaps with the projection of the first tapered portion on the second substrate, and the third tapered portion and the first tapered portion form a first transition structure; the tapered directions of the third tapered portion and the first tapered portion are inverted; The projection of the fourth tapered portion on the second substrate partially overlaps with the projection of the second tapered portion on the second substrate, and the fourth tapered portion and the second tapered portion form a second transition structure; the tapered directions of the fourth tapered portion and the second tapered portion are inverted; In the step of bringing the electro-optical thin film layer of the first waveguide core substrate into corresponding contact with and bonding the second bonding medium layer of the second waveguide core substrate together, the projection of the electro-optical thin film layer on the second substrate at least covers the projection of the third conical portion on the second substrate and a portion of the projection of the intermediate transition region on the second substrate.

4. The method for preparing a heterogeneous integrated electro-optical modulation device according to claim 3, characterized in that: The heterogeneous integrated electro-optical modulation device comprises at least one of the first waveguide cores, at least two of the transition waveguide cores and at least two second waveguide cores; the first waveguide core comprises first tapered portions at both ends of the length direction; Each of the first waveguide cores is provided with a transition waveguide core at both ends in the length direction; the third tapered portion of each transition waveguide core and the first tapered portion form a first transition structure; The second waveguide core is located at one side of the fourth tapered portion of the transition waveguide core, and the fourth tapered portion of each transition waveguide core and the second tapered portion form a second transition structure.

5. The method for preparing a heterogeneous integrated electro-optical modulation device according to claim 4, characterized in that: The heterogeneous integrated electro-optical modulation device comprises one of the first waveguide cores, two of the transition waveguide cores and two second waveguide cores; The two transition waveguide cores are respectively located at two ends of the first waveguide core in the length direction; the two second waveguide cores are respectively located at one side of the fourth tapered portion of the two transition waveguide cores.

6. The method for preparing a heterogeneous integrated electro-optical modulation device according to claim 1, characterized in that: The bonding platform does not include a waveguide; The steps to provide a bonding platform include: providing a third substrate; forming a third cladding layer on a third substrate; The step of contacting and bonding the electro-optical thin film layer of the first waveguide core substrate to the bonding platform comprises: The electro-optical thin film layer of the first waveguide core substrate and the third cladding layer are contacted with each other and bonded together.

7. The method for preparing a heterogeneous integrated electro-optical modulation device according to claim 1, characterized in that: The first waveguide core and the electro-optical thin film layer form a composite waveguide core; The process of forming the first waveguide core layer is a deposition process; the first waveguide core layer is a stoichiometric silicon nitride film or a stoichiometric silicon nitride film-silicon dioxide film-stoichiometric silicon nitride film stack; The process for forming the first bonding dielectric layer is a deposition process; the first bonding dielectric layer is a silicon dioxide film, an aluminum oxide film, or a silicon dioxide film-aluminum oxide film stack; The process for forming the electro-optical thin film layer is an intelligent ion cutting process or a wafer thinning process; The material of the electro-optical thin film layer is lithium niobate, lithium tantalate or barium titanate; The material of the first substrate is silicon; The material of the buried layer is silicon dioxide; the thickness of the buried layer is 0.1 μm to 2 μm; The thickness of the first waveguide core layer is 100nm to 500nm; The thickness of the first bonding medium layer is 10nm to 300nm; The thickness of the electro-optical thin film layer is 100nm to 500nm.

8. The method for preparing a heterogeneous integrated electro-optical modulation device according to claim 7, characterized in that: The process for forming the first waveguide core layer is a low pressure chemical vapor deposition process; the first waveguide core layer is a stoichiometric silicon nitride film; The first waveguide core is a stoichiometric silicon nitride core; The electro-optical thin film layer is a lithium niobate thin film; The stoichiometric silicon nitride core and the lithium niobate film constitute a silicon nitride-lithium niobate composite waveguide core.

9. The method for preparing a heterogeneous integrated electro-optical modulation device according to claim 2, characterized in that: The refractive index of the second waveguide core is greater than the refractive index of the first cladding and the second cladding; The refractive index of the transition waveguide core is greater than the refractive index of the electro-optical thin film layer; The material of the first substrate is silicon; The material of the first cladding layer is silicon dioxide; The material of the second cladding layer is silicon dioxide; The material of the second bonding medium layer is one or more of silicon dioxide, aluminum oxide, and bonding glue; The thickness of the first cladding layer is 2 μm to 20 μm; The thickness of the second cladding layer located above the second waveguide core is 0.1 μm to 1.5 μm; the thickness of the second bonding medium layer located above the transition waveguide core is 0.2 μm to 1.5 μm.

10. The method for preparing a heterogeneous integrated electro-optical modulation device according to claim 9, characterized in that: The second waveguide core is a layer of a silicon film, a silicon nitride film, or a multilayer composed of a silicon dioxide film and a silicon nitride film; The material of the transition waveguide core is silicon-rich silicon nitride or silicon.

11. A heterogeneous integrated electro-optical modulation device, characterized in that: The heterogeneous integrated electro-optical modulation device is prepared by the method for preparing a heterogeneous integrated electro-optical modulation device according to any one of claims 1 to 10, comprising: Bonding platform; An electro-optical thin film layer, located on one surface of the bonding platform; A first bonding medium layer is located on a surface of the electro-optical thin film layer facing away from the bonding platform; A first waveguide core is located on a portion of the surface of the first bonding medium layer facing away from the electro-optical thin film layer, exposing a portion of the first bonding medium layer; A buried layer, located on a surface of the first waveguide core facing away from the first bonding dielectric layer; An electrode is provided on a surface of the first bonding medium layer at a side portion of the first waveguide core.

12. The heterogeneous integrated electro-optic modulation device according to claim 11, characterized in that: The bonding platform is a second waveguide core substrate; The second waveguide core substrate comprises a second substrate, a first cladding, a second waveguide core, a second cladding, a transition waveguide core and a second bonding medium layer stacked in sequence; the second cladding covers the surface and side surfaces of the second waveguide core; the second bonding medium layer covers the surface and side surfaces of the transition waveguide core; The second waveguide core substrate is located on a surface of the electro-optical thin film layer that is opposite to the first bonding medium layer; wherein the second bonding medium layer is in contact with the electro-optical thin film layer; The projection of the electro-optical thin film layer on the second substrate at least covers a portion of the projection of the transition waveguide core on the second substrate; The projection of the first waveguide core on the second substrate partially overlaps with the projection of the transition waveguide core on the second substrate; the projection of the second waveguide core on the second substrate partially overlaps with the projection of the transition waveguide core on the second substrate.

13. The heterogeneous integrated electro-optical modulation device according to claim 12, characterized in that: The heterogeneous integrated electro-optic modulation device comprises at least one of the first waveguide cores, at least two of the transition waveguide cores and at least two second waveguide cores; The first waveguide core comprises first tapered portions at both ends in the length direction; the second waveguide core comprises a second tapered portion at at least one end in the length direction; the transition waveguide core comprises a third tapered portion and a fourth tapered portion at both ends in the length direction; the region between the third tapered portion and the fourth tapered portion is an intermediate transition region; Each of the first waveguide cores is provided with a transition waveguide core at both ends in the length direction; the third tapered portion of each transition waveguide core and the first tapered portion form a first transition structure; The second waveguide core is located on one side of the fourth tapered portion of the transition waveguide core, and the fourth tapered portion of each transition waveguide core and the second tapered portion form a second transition structure; The projection of the electro-optical thin film layer on the second substrate at least covers the projection of the third conical portion on the second substrate and a portion of the projection of the intermediate transition region on the second substrate.

Images