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: forming a groove in the surface of one side of a first substrate, filling the groove to form a protection layer, sequentially forming a buried layer and an electro-optical material layer on the surface of one side, opposite to the first substrate, of the protection layer, and forming an electro-optical material wafer; a wrapping layer, a waveguide core and a bonding dielectric layer are sequentially formed on the surface of one side of the second substrate, the bonding dielectric layer wraps the surface of the side, back to the second substrate, of the waveguide core and the side face of the waveguide core, and a waveguide core wafer is formed; enabling the electro-optical material layer and the bonding dielectric layer to be in contact and bonding connection together; the projection of the protective layer on the second substrate at least partially covers the projection of the waveguide core on the second substrate; removing the first substrate; and forming a plurality of electrodes on one side of the buried layer, wherein the electrodes are located at corresponding positions on two sides of the waveguide core. According to the invention, the propagation loss of the electro-optical material layer-waveguide core composite waveguide can be reduced, and the electro-optical modulation efficiency and speed of the device can be 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] In existing heterogeneous integrated electro-optic modulation devices, an electro-optic material thin film (such as thin film lithium niobate) is generally bonded above a silicon nitride waveguide core to form a composite waveguide. One of the technical solutions is to bond a thin film lithium niobate wafer or chip (the structure is usually lithium niobate thin film / buried oxide layer / silicon substrate) to a silicon nitride photonics platform wafer, and then remove the silicon substrate of the thin film lithium niobate wafer to achieve the heterogeneous integration of lithium niobate-silicon nitride. The electro-optic material thin film generally has two forms: wafer and chip.

[0003] For bonding an electro-optic material thin film wafer (such as a thin film lithium niobate wafer) to the surface of a silicon nitride waveguide core wafer, a lithography process needs to be performed on the lithium niobate to achieve the integration of other silicon nitride-based photonic devices, metal interconnection, and wiring other than electro-optic modulation. However, performing lithography on lithium niobate reduces the compatibility of the preparation process with the CMOS process.

[0004] For bonding an electro-optic material thin film chip (such as a thin film lithium niobate chip) to the surface of a silicon nitride waveguide core wafer, the thin film lithium niobate chips are discretely distributed on the surface of the silicon nitride wafer. During the process of removing the silicon substrate of the thin film lithium niobate, due to the large thickness of the silicon substrate and the long removal time, there is uneven silicon removal, resulting in silicon residue or buried oxide layer damage, which leads to an increase in the propagation loss of the silicon nitride-lithium niobate composite waveguide. In addition, by increasing the thickness of the buried oxide layer of the thin film lithium niobate wafer, silicon residue or the buried oxide layer increasing the propagation loss of the silicon nitride-lithium niobate composite waveguide can be avoided, but it will affect the electro-optic modulation efficiency and speed.

[0005] Therefore, a solution is needed to avoid the increase in the propagation loss of the composite waveguide caused by substrate residue and surface damage during the substrate removal process, and at the same time minimize the impact on the electro-optic modulation efficiency and speed. Summary of the Invention

[0006] In view of this, the present invention provides a heterogeneous integrated electro-optic modulation device and a preparation method thereof to solve the problems in the related art that after bonding an electro-optic material thin film wafer or chip to the surface of a waveguide core wafer, during the process of removing the electro-optic material thin film substrate, problems such as long removal time, silicon substrate residue, and buried oxide layer damage occur, resulting in an increase in the propagation loss of the silicon nitride-lithium niobate composite waveguide, and the low compatibility of the preparation process with the CMOS process.

[0007] In a first aspect, the present invention provides a preparation method of a heterogeneous integrated electro-optic modulation device, and the preparation method includes:

[0008] Provide a first substrate, form a groove on one side surface of the first substrate, and the groove penetrates into a part of the first substrate;

[0009] Fill the groove to form a protective layer;

[0010] Form a buried layer and an electro-optic material layer in sequence on the side surface of the protective layer facing away from the first substrate to form an electro-optic material wafer;

[0011] Provide a second substrate, form a cladding layer, a waveguide core, and a bonding dielectric layer in sequence on one side surface of the second substrate, and 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 to form a waveguide core wafer;

[0012] Contact the electro-optic material layer with the bonding dielectric layer and bond them together; the projection of the protective layer on the second substrate at least partially covers the projection of the waveguide core on the second substrate;

[0013] Remove the first substrate;

[0014] Form a plurality of electrodes on the side of the buried layer facing away from the electro-optic material layer, and the electrodes are located at corresponding positions on both sides of the waveguide core.

[0015] The preparation method of the heterogeneous integrated electro-optic modulation device provided by the present invention, by providing a protective layer on the electro-optic material thin film wafer corresponding to the position of the waveguide core of the electro-optic material layer-waveguide core composite waveguide, enables the protective layer to protect each film layer within the optical field distribution region of the composite waveguide from etching damage during the step of removing the first substrate. At the same time, the protective layer can also make the optical field distribution of the composite waveguide not close to the surface of the protective layer. Therefore, it is possible to avoid scattering loss and absorption loss of the optical field caused by surface damage of the buried layer and residue of the first substrate, thereby reducing the propagation loss of the electro-optic material layer-waveguide core composite waveguide and improving the stability and reliability of the heterogeneous integrated electro-optic modulation device. In addition, the protective layer and the buried layer below it together serve as a protective cladding for the electro-optic material layer-waveguide core composite waveguide, which can reduce the damage to the electro-optic material layer-waveguide core composite waveguide during the process, improve the reliability and yield of the device; it can also reduce the influence of the relatively thick buried layer on the electro-optic modulation efficiency and speed, thereby improving the electro-optic modulation efficiency and speed of the heterogeneous integrated electro-optic modulation device.

[0016] In an optional embodiment, in the step of contacting the electro-optic material layer with the bonding dielectric layer and bonding them together, the projection of the protective layer on the second substrate completely covers the projection of the waveguide core on the second substrate.

[0017] The preparation method of the heterogeneous integrated electro-optic modulation device provided by the present invention is such that the projection of the protective layer on the second substrate completely covers the projection of the waveguide core on the second substrate, so that the protective layer can completely cover the optical field distribution region of the electro-optic material layer-waveguide core composite waveguide. During the process of removing the first substrate, the film layers in the optical field distribution region covered by the protective layer are not damaged. At the same time, the protective layer can also make the optical field distribution of the composite waveguide not close to the surface of the protective layer, avoiding the influence of the remaining part of the first substrate and the damage to the buried layer surface close to the optical field distribution region, thereby reducing the scattering loss and absorption loss of the electro-optic material layer-waveguide core composite waveguide. At the same time, the protective layer can also make the optical field distribution of the composite waveguide not close to the surface of the protective layer, avoiding the influence of the first substrate removal process on the optical field distribution of the composite waveguide.

[0018] In an alternative embodiment, the material of the protective layer is metal or SiO2.

[0019] In an alternative embodiment, the material of the protective layer is metal;

[0020] After the step of removing the first substrate and before the step of forming multiple electrodes, it further includes: removing the protective layer.

[0021] The preparation method of the heterogeneous integrated electro-optic modulation device provided by the present invention removes the protective layer before the step of forming multiple electrodes, which can further reduce the influence of the protective layer on the propagation loss, electro-optic modulation efficiency and speed, thereby improving the electro-optic modulation efficiency and speed of the heterogeneous integrated electro-optic modulation device. At the same time, it can reduce the device thickness and improve the device integration.

[0022] In an alternative embodiment, the material of the protective layer is metal;

[0023] The projection of the protective layer on the second substrate also covers both sides of the projection of the waveguide core on the second substrate;

[0024] The step of forming multiple electrodes includes:

[0025] Removing the part of the protective layer corresponding to the waveguide core and using the remaining part of the protective layer on both sides of the waveguide core as multiple electrodes.

[0026] The preparation method of the heterogeneous integrated electro-optic modulation device provided by the present invention removes part of the protective layer before the step of forming multiple electrodes and uses the remaining part of the protective layer as electrodes, which can improve the electro-optic modulation efficiency and speed of the heterogeneous integrated electro-optic modulation device. At the same time, it can simplify the process flow and improve the process efficiency.

[0027] In an alternative embodiment, the electro-optic material wafer includes multiple protective layers;

[0028] The waveguide core wafer includes multiple waveguide cores, and the bonding dielectric layer coats the multiple waveguide cores;

[0029] In the step of bringing the electro-optic material layer into contact with the bonding dielectric layer and bonding them together,

[0030] The projection of each protective layer on the second substrate at least partially covers the projection of a waveguide core on the second substrate.

[0031] In an alternative embodiment, at least one protective layer is a multi-step protective layer; the material of the multi-step protective layer is SiO2;

[0032] At least one waveguide core is a target waveguide core;

[0033] In the step of bringing the electro-optic material layer into contact with the bonding dielectric layer and bonding them together,

[0034] The projection of the multi-step protective layer on the second substrate at least partially covers the projection of the target waveguide core on the second substrate;

[0035] The step of forming a plurality of electrodes further includes:

[0036] Forming an electrode wiring on the side of the buried layer facing away from the electro-optic material layer, the electrode wiring also covering a part of the surface of the multi-step protective layer facing away from the buried layer and a part of the side surface of the multi-step protective layer, the electrode wiring connecting at least one electrode; the electrode wiring passes over the target waveguide core through the multi-step protective layer; there is a projection intersection area between the projection of the electrode wiring on the second substrate and the projection of the target waveguide core on the second substrate.

[0037] In an alternative embodiment, in the step of forming a groove, at least one groove is a multi-step groove, the multi-step groove includes a plurality of stepped grooves with different depths, and the depth of each stepped groove is 0.5 μm to 5 μm; the maximum width of the multi-step groove is 1 μm to 100 μm;

[0038] The step of filling the groove to form a protective layer includes:

[0039] Filling the groove with SiO2 to form a protective layer, wherein filling the multi-step groove forms a multi-step protective layer; the multi-step protective layer includes a plurality of steps with different thicknesses; the step with the largest thickness is the wiring protection area;

[0040] In the step of forming the electrode wiring, the projection of the wiring protection area on the second substrate covers the projection intersection area.

[0041] The manufacturing method of the heterogeneous integrated electro-optic modulation device provided by the present invention, by setting a multi-step protective layer, after the electro-optic material layer and the bonding dielectric layer are bonded, the multi-step protective layer is located above the target waveguide core, the electrode wiring passes above the multi-step protective layer and straddles the electro-optic material layer - target waveguide core composite waveguide, and the projection of the wiring protection area on the second substrate covers the projection intersection area, which can increase the distance between the electrode wiring and the electro-optic material layer - target waveguide core composite waveguide, avoid the problem that the electrode wiring causes an increase in the propagation loss of the composite waveguide, thereby reducing the propagation loss of the device while minimizing the impact on the electro-optic modulation efficiency and speed, and at the same time making the manufacturing process have high CMOS process compatibility.

[0042] In an optional implementation manner, before the step of bringing the electro-optic material layer into contact with the bonding dielectric layer and bonding them together, it further includes:

[0043] Longitudinally cut the electro-optic material wafer to obtain a plurality of electro-optic material chips; each electro-optic material chip sequentially includes a first substrate, at least one protective layer, a buried layer, and an electro-optic material layer;

[0044] The step of bringing the electro-optic material layer into contact with the bonding dielectric layer and bonding them together includes:

[0045] Bring the electro-optic material layer of the electro-optic material chip into contact with the bonding dielectric layer of the waveguide core wafer and bond them together; wherein, the electro-optic material layer of the electro-optic material chip corresponds to the waveguide core; the projection of the protective layer on the second substrate at least partially covers the projection of the waveguide core on the second substrate.

[0046] The manufacturing method of the heterogeneous integrated electro-optic modulation device provided by the present invention, by setting a protective layer corresponding to the position of the waveguide core of the electro-optic material layer - waveguide core composite waveguide on the electro-optic material thin film chip, in the step of removing the first substrate, the protective layer can protect each film layer in the optical field distribution area of the composite waveguide from etching damage, and at the same time the protective layer can also make the optical field distribution of the composite waveguide not close to the surface of the protective layer, so that it is possible to avoid the surface damage of the buried layer of the electro-optic material thin film chip and the scattering loss and absorption loss of the optical field caused by the residue of the first substrate, thereby reducing the propagation loss of the electro-optic material layer - waveguide core composite waveguide and improving the stability and reliability of the heterogeneous integrated electro-optic modulation device.

[0047] In an optional implementation manner, the step of filling the groove to form the protective layer includes:

[0048] Fill the groove to form an initial protective layer, the thickness of the initial protective layer is greater than the depth of the groove, or the thickness of the initial protective layer is greater than half of the width of the groove;

[0049] Perform a planarization process on the initial protective layer until the surface of the first substrate is exposed, and use the remaining initial protective layer as the protective layer.

[0050] In a second aspect, the present invention provides a heterogeneous integrated electro-optic modulation device, which includes:

[0051] A waveguide core wafer, which includes a stacked second substrate, a cladding layer, a waveguide core, and a bonding dielectric layer. The bonding dielectric layer coats the surface of the waveguide core facing away from the second substrate and the side surfaces of the waveguide core;

[0052] An electro-optic material layer, located on the surface of the bonding dielectric layer facing away from the waveguide core;

[0053] A buried layer, located on the surface of the electro-optic material layer facing away from the bonding dielectric layer;

[0054] A plurality of electrodes, located on the side of the buried layer facing away from the electro-optic material layer, and the electrodes are located at corresponding positions on both sides of the waveguide core.

[0055] The heterogeneous integrated electro-optic modulation device provided by the present invention is prepared by the preparation method of the above heterogeneous integrated electro-optic modulation device, which can avoid scattering loss and absorption loss of the optical field caused by buried layer damage and the residue of the first substrate, thereby reducing the propagation loss of the electro-optic material layer-waveguide core composite waveguide and improving the stability and reliability of the heterogeneous integrated electro-optic modulation device.

[0056] In an optional embodiment, the heterogeneous integrated electro-optic modulation device further includes:

[0057] A protective layer, located on the surface of the buried layer facing away from the waveguide core, and the projection of the protective layer on the second substrate at least partially covers the projection of the waveguide core on the second substrate;

[0058] The material of the protective layer is SiO2.

[0059] For the heterogeneous integrated electro-optic modulation device provided by the present invention, the protective layer and the buried layer below it together serve as the protective cladding of the electro-optic material layer-waveguide core composite waveguide, which can reduce the damage to the electro-optic material layer-waveguide core composite waveguide during the process, improve the reliability and yield of the device; and can also reduce the influence of the relatively thick buried layer on the electro-optic modulation efficiency and speed, thereby improving the electro-optic modulation efficiency and speed of the heterogeneous integrated electro-optic modulation device.

[0060] In an optional embodiment, the protective layer includes a single-layer protective layer;

[0061] The thickness of the single-layer protective layer is 0.5 μm to 5 μm; the width of the single-layer protective layer is 1 μm to 100 μm.

[0062] In an optional embodiment, the protective layer includes a multi-step protective layer;

[0063] The waveguide core wafer includes at least one target waveguide core;

[0064] The projection of the multi-step protective layer on the second substrate at least partially covers the projection of the target waveguide core on the second substrate;

[0065] The heterogeneous integrated electro-optic modulation device further includes:

[0066] Electrode wiring, located on the side of the buried layer facing away from the electro-optic material layer, the electrode wiring also covers a part of the surface of the multi-step protective layer facing away from the buried layer and a part of the side surface of the multi-step protective layer, and the electrode wiring is connected to at least one electrode; the electrode wiring crosses the target waveguide core through the multi-step protective layer; there is a projection intersection area between the projection of the electrode wiring on the second substrate and the projection of the target waveguide core on the second substrate.

[0067] In an optional implementation manner, the multi-step protective layer includes multiple steps with different thicknesses; the thickness of each step is 0.5 μm to 5 μm; the maximum width of the multi-step protective layer is 1 μm to 100 μm;

[0068] Among them, the step with the largest thickness is the wiring protection area; the projection of the wiring protection area on the second substrate covers the projection intersection area.

[0069] For the heterogeneous integrated electro-optic modulation device provided by the present invention, by setting the multi-step protective layer and the projection of the wiring protection area on the second substrate covering the projection intersection area, the distance between the electrode wiring and the electro-optic material layer - target waveguide core composite waveguide can be increased, and the propagation loss of the composite waveguide can be reduced. Description of the Drawings

[0070] In order to more clearly illustrate the specific implementation manners 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 implementation manners or the related art. Obviously, the following drawings are some implementation manners of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0071] Figure 1 It is a schematic flowchart of a preparation method of a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0072] Figure 2 It is a specific schematic flowchart of a preparation method of a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0073] Figure 3 It is a schematic structural diagram of a first substrate in a preparation method of a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0074] Figure 4A and Figure 4BIt is a schematic structural diagram of forming a groove in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention. Figure 4A is Figure 4B a cross-sectional view on the AA plane.

[0075] Figure 5 It is a schematic structural diagram of forming an initial protective layer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0076] Figure 6A and Figure 6B It is a schematic structural diagram of forming a protective layer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention. Figure 6A is Figure 6B a cross-sectional view on the AA plane.

[0077] Figure 7A and Figure 7B It is a schematic structural diagram of an electro-optic material wafer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention. Figure 7A is Figure 7B a cross-sectional view on the AA plane.

[0078] Figure 8A and Figure 8B It is a schematic structural diagram of forming a waveguide core in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention. Figure 8A is Figure 8B a cross-sectional view on the AA plane.

[0079] Figure 9 It is a schematic structural diagram of a waveguide core wafer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0080] Figure 10A and Figure 10B It is a schematic structural diagram after bonding an electro-optic material layer and a bonding dielectric layer in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention. Figure 10A is Figure 10B a cross-sectional view on the AA plane.

[0081] Figure 11A and Figure 11B It is a 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. Figure 11A is Figure 11B a cross-sectional view on the AA plane.

[0082] Figure 12 It is a schematic structural diagram of forming an electrode on the basis of Figure 11A in a method for manufacturing a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0083] Figure 13 It is a schematic diagram of the specific process of another method for fabricating a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0084] Figure 14A and Figure 14B It is in the method for fabricating another heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention Figure 11A and Figure 11B A schematic diagram of the structure after removing the protective layer on the basis of Figure 14A It is Figure 14B A cross-sectional view on the AA plane.

[0085] Figure 15 It is in the method for fabricating another heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention Figure 14A A schematic diagram of the structure for forming an electrode on the basis of

[0086] Figure 16 It is a schematic diagram of the specific process of yet another method for fabricating a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0087] Figure 17 A schematic diagram of the structure for forming a groove in yet another method for fabricating a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention.

[0088] Figure 18A 、 Figure 18B and Figure 18C A schematic diagram of the structure for forming a protective layer in yet another method for fabricating a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention, Figure 18A It is Figure 18B or Figure 18C A cross-sectional view on the AA plane.

[0089] Figure 19A 、 Figure 19B and Figure 19C A schematic diagram of the structure of an electro-optic material wafer in yet another method for fabricating a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention, Figure 19A It is Figure 19B or Figure 19C A cross-sectional view on the AA plane.

[0090] Figure 20A and Figure 20B A schematic diagram of the structure of a waveguide core wafer in yet another method for fabricating a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention, Figure 20A It is Figure 20B A cross-sectional view on the AA plane.

[0091] Figure 21A 、 Figure 21B and Figure 21CIt is a schematic structural diagram after bonding the electro-optic material layer and the bonding dielectric layer in another method for fabricating a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention. Figure 21A is Figure 21B or Figure 21C a cross-sectional view on the AA plane.

[0092] Figure 22A 、 Figure 22B and Figure 22C It is a schematic structural diagram of removing the first substrate in another method for fabricating a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention. Figure 22A is Figure 22B or Figure 22C a cross-sectional view on the AA plane.

[0093] Figure 23A 、 Figure 23B and Figure 23C It is a schematic structural diagram of forming electrodes and electrode wirings in another method for fabricating a heterogeneous integrated electro-optic modulation device according to an embodiment of the present invention. Figure 23A is Figure 23B or Figure 23C a cross-sectional view on the AA plane.

[0094] Reference numerals:

[0095] 10, the first substrate; 11, the groove; 111, the multi-step groove; 12, the protective layer, 121, the multi-step protective layer; 13, the buried layer; 14, the electro-optic material layer; 20, the second substrate; 21, the cladding layer; 22, the waveguide core; 221, the target waveguide core; 23, the bonding dielectric layer; 30, the electrode; 31, the electrode wiring. Detailed implementation manners

[0096] 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, not all structures.

[0097] 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, some details are enlarged and some 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 requirements. 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.

[0098] An electro-optic modulation device formed by hetero-integrating a stoichiometric silicon nitride (Si3N4) waveguide core prepared by low-pressure chemical vapor deposition (LPCVD) with thin-film lithium niobate fully combines the advantages of the two materials and has advantages such as low optical propagation loss, high-speed and low-power electro-optic modulation, and a wide spectral transparency range, thus attracting wide attention. Due to the large difference in thermal expansion coefficients between lithium niobate and silicon, and the difficulties in etching and the potential pollution risk to CMOS devices, improving the structure and manufacturing process of the silicon nitride-lithium niobate electro-optic modulation device to enhance CMOS process compatibility has become one of the research directions.

[0099] Existing hetero-integrated electro-optic modulation devices generally bond an electro-optic material thin film (such as thin-film lithium niobate) above a silicon nitride waveguide core to form a composite waveguide. One of the technical solutions is to bond a thin-film lithium niobate wafer or chip (the structure is usually a lithium niobate thin film / buried oxide layer / silicon substrate) to a silicon nitride photonics platform wafer, and then remove the silicon substrate of the thin-film lithium niobate wafer to achieve the hetero-integration of lithium niobate-silicon nitride. The electro-optic material thin film generally has two forms: wafer and chip.

[0100] For bonding an electro-optic material thin film wafer (such as a thin-film lithium niobate wafer) to the surface of a silicon nitride waveguide core wafer, a patterning process needs to be performed on the lithium niobate to achieve the integration of other silicon nitride-based photonic devices, metal interconnection, and wiring in addition to electro-optic modulation. However, performing lithium niobate patterning reduces the compatibility of the preparation process with the CMOS process.

[0101] For the bonding of a small piece of electro-optic material thin film (such as a lithium niobate small piece) to the surface of a silicon nitride waveguide core wafer, the thin film lithium niobate small pieces are discretely distributed on the surface of the silicon nitride wafer. During the process of removing the silicon substrate of the thin film lithium niobate, due to the large thickness of the silicon substrate and the long removal time, there is uneven silicon removal, resulting in silicon residue or buried oxide layer damage, which leads to an increase in the propagation loss of the silicon nitride-lithium niobate composite waveguide. In addition, by increasing the thickness of the buried oxide layer of the thin film lithium niobate wafer, silicon residue or the buried oxide layer increasing the propagation loss of the silicon nitride-lithium niobate composite waveguide can be avoided, but it will affect the electro-optic modulation efficiency and speed.

[0102] Therefore, a solution is needed to avoid residues during the substrate removal process, protect the waveguide core from damage, reduce the propagation loss of the composite waveguide, and at the same time not affect the electro-optic modulation efficiency and speed.

[0103] As Figure 1 shown, this embodiment provides a method for fabricating a heterogeneous integrated electro-optic modulation device, and this fabrication method includes but is not limited to steps S101 to S107.

[0104] Step S101: Provide a first substrate 10, and form a groove 11 on one side surface of the first substrate 10, and the groove 11 penetrates into part of the first substrate 10;

[0105] Step S102: Fill the groove 11 to form a protective layer 12;

[0106] Step S103: Sequentially form a buried layer 13 and an electro-optic material layer 14 on the side surface of the protective layer 12 facing away from the first substrate 10 to form an electro-optic material wafer;

[0107] Step S104: Provide a second substrate 20, and sequentially form a cladding layer 21, a waveguide core 22, and a bonding dielectric layer 23 on one side surface of the second substrate 20. The bonding dielectric layer 23 covers the side surface of the waveguide core 22 facing away from the second substrate 20 and the side surface of the waveguide core 22 to form a waveguide core wafer;

[0108] Step S105: Bring the electro-optic material layer 14 into contact with the bonding dielectric layer 23 and bond them together; the projection of the protective layer 12 on the second substrate 20 at least partially covers the projection of the waveguide core 22 on the second substrate 20;

[0109] Step S106: Remove the first substrate 10;

[0110] Step S107: Form a plurality of electrodes 30 on the side of the buried layer 13 facing away from the electro-optic material layer 14, and the electrodes 30 are located at corresponding positions on both sides of the waveguide core 22.

[0111] The preparation method of the heterogeneous integrated electro-optic modulation device provided by this embodiment is to set a protective layer corresponding to the waveguide core position of the electro-optic material layer-waveguide core composite waveguide on the electro-optic material thin film wafer, so that in the step of removing the first substrate, the protective layer can protect each film layer in the optical field distribution area of the composite waveguide from etching damage. At the same time, the protective layer can also make the optical field distribution of the composite waveguide not close to the surface of the protective layer. Therefore, it is possible to avoid scattering loss and absorption loss of the optical field caused by buried layer surface damage and first substrate residue, thereby reducing the propagation loss of the electro-optic material layer-waveguide core composite waveguide and improving the stability and reliability of the heterogeneous integrated electro-optic modulation device. In addition, the protective layer and the buried layer below it together serve as the protective cladding of the electro-optic material layer-waveguide core composite waveguide, which can reduce the damage to the electro-optic material layer-waveguide core composite waveguide during the process, improve the reliability and yield of the device; and can also reduce the influence of the relatively thick buried layer on the electro-optic modulation efficiency and speed, thereby improving the electro-optic modulation efficiency and speed of the heterogeneous integrated electro-optic modulation device.

[0112] In some optional embodiments, in the step of contacting and bonding the electro-optic material layer 14 and the bonding dielectric layer 23 together, the projection of the protective layer 12 on the second substrate 20 completely covers the projection of the waveguide core 22 on the second substrate 20.

[0113] The preparation method of the heterogeneous integrated electro-optic modulation device provided by this embodiment is that the projection of the protective layer on the second substrate completely covers the projection of the waveguide core on the second substrate, so that the protective layer can completely cover the optical field distribution area of the electro-optic material layer-waveguide core composite waveguide, so that in the process of removing the first substrate, each film layer in the optical field distribution area covered by the protective layer is not damaged. At the same time, the protective layer can also make the optical field distribution of the composite waveguide not close to the surface of the protective layer, avoiding the first substrate residue and buried layer surface damage approaching the optical field distribution area, thereby reducing the scattering loss and absorption loss of the electro-optic material layer-waveguide core composite waveguide.

[0114] In some optional embodiments, the material of the protective layer 12 is metal or SiO2.

[0115] In some optional embodiments, the protective layer 12 includes a single-layer protective layer;

[0116] The thickness of the single-layer protective layer is 0.5 μm to 5 μm; the width of the single-layer protective layer is 1 μm to 100 μm.

[0117] In some optional embodiments, in the step of forming a plurality of electrodes 30, the electrodes 30 are located on both sides of the protective layer 12. In the finally formed heterogeneous integrated electro-optic modulation device, the protective layer 12 is retained.

[0118] In some optional embodiments, the material of the protective layer 12 is SiO2;

[0119] After the step of removing the first substrate 10, before the step of forming a plurality of electrodes 30, it further includes: removing the protective layer 12.

[0120] In specific implementation, when the material of the protective layer 12 is SiO2, the protective layer 12 can be optionally removed or retained, without affecting the formation of the electrodes 30.

[0121] In some alternative embodiments, the material of the protective layer 12 is metal;

[0122] After the step of removing the first substrate 10, before the step of forming a plurality of electrodes 30, it further includes: removing the protective layer 12.

[0123] In the method for manufacturing a heterogeneous integrated electro-optic modulation device provided in this embodiment, removing the protective layer before the step of forming a plurality of electrodes can further reduce the influence of the protective layer on the propagation loss, electro-optic modulation efficiency, and speed, thereby improving the electro-optic modulation efficiency and speed of the heterogeneous integrated electro-optic modulation device. At the same time, the device thickness can be reduced, and the device integration can be improved.

[0124] In some alternative embodiments, the material of the protective layer 12 is metal;

[0125] The projection of the protective layer 12 on the second substrate 20 also covers both sides of the projection of the waveguide core 22 on the second substrate 20;

[0126] The step of forming a plurality of electrodes 30 includes:

[0127] Removing the corresponding part of the protective layer 12 of the waveguide core 22, and using the remaining part of the protective layer 12 on both sides of the waveguide core 22 as a plurality of electrodes 30.

[0128] In the method for manufacturing a heterogeneous integrated electro-optic modulation device provided in this embodiment, removing a part of the protective layer before the step of forming a plurality of electrodes and using the remaining part of the protective layer as electrodes can improve the electro-optic modulation efficiency and speed of the heterogeneous integrated electro-optic modulation device. At the same time, the process flow can be simplified, and the process efficiency can be improved.

[0129] In some alternative embodiments, the electro-optic material wafer includes a plurality of protective layers 12;

[0130] The waveguide core wafer includes a plurality of waveguide cores 22, and the bonding dielectric layer 23 coats the plurality of waveguide cores 22;

[0131] In the step of bringing the electro-optic material layer 14 into contact with the bonding dielectric layer 23 and bonding them together,

[0132] The projection of each protective layer 12 on the second substrate 20 at least partially covers the projection of one waveguide core 22 on the second substrate 20.

[0133] In some alternative embodiments, at least one protective layer 12 is a multi-step protective layer 121; the material of the multi-step protective layer 121 is SiO2;

[0134] At least one waveguide core 22 is a target waveguide core 221;

[0135] In the step of bringing the electro-optic material layer 14 into contact with the bonding dielectric layer 23 and bonding them together,

[0136] The projection of the multi-step protective layer 121 on the second substrate 20 at least partially covers the projection of the target waveguide core 221 on the second substrate 20;

[0137] The step of forming a plurality of electrodes 30 further includes:

[0138] Forming an electrode wiring 31 on the side of the buried layer 13 facing away from the electro-optic material layer 14, the electrode wiring 31 also covering a part of the surface of the multi-step protective layer 121 facing away from the buried layer 13 and a part of the side surface of the multi-step protective layer 121, the electrode wiring 31 connecting at least one electrode 30; the electrode wiring 31 passing over the target waveguide core 221 across the multi-step protective layer 121; there being a projection intersection area between the projection of the electrode wiring 31 on the second substrate 20 and the projection of the target waveguide core 221 on the second substrate 20.

[0139] In specific implementation, as Figure 23A 、 Figure 23B and Figure 23C shown, a part of the electrode wiring 31 is located above the buried layer 13 and a part is located above the multi-step protective layer 121; the electrode wiring 31 passes over the target waveguide core 221 across the multi-step protective layer 121 and is connected to at least one electrode 30, thereby leading out the electrode 30.

[0140] In some alternative embodiments, in the step of forming the groove 11, at least one groove 11 is a multi-step groove 111, the multi-step groove 111 including a plurality of stepped grooves with different depths, the depth of each stepped groove being 0.5 μm to 5 μm; the maximum width of the multi-step groove 111 being 1 μm to 100 μm;

[0141] The step of filling the groove 11 to form the protective layer 12 includes:

[0142] Filling the groove 11 with SiO2 to form the protective layer 12, wherein filling the multi-step groove 111 forms the multi-step protective layer 121; the multi-step protective layer 121 including a plurality of steps with different thicknesses; the step with the largest thickness being the wiring protection area;

[0143] In the step of forming the electrode wiring 31, the projection of the wiring protection area on the second substrate 20 covers the projection intersection area.

[0144] The manufacturing method of the heterogeneous integrated electro-optic modulation device provided by this embodiment, by setting a multi-step protective layer, after the electro-optic material layer and the bonding dielectric layer are bonded, the multi-step protective layer is located above the target waveguide core, the electrode wiring passes over the multi-step protective layer and crosses the electro-optic material layer - target waveguide core composite waveguide, and the projection of the wiring protection area on the second substrate covers the projection intersection area, which can increase the distance between the electrode wiring and the electro-optic material layer - target waveguide core composite waveguide, avoid the problem that the electrode wiring causes an increase in the propagation loss of the composite waveguide, thereby reducing the propagation loss of the device while minimizing the impact on the electro-optic modulation efficiency and speed, and at the same time making the manufacturing process have high CMOS process compatibility.

[0145] In some alternative embodiments, at least one protective layer 12 is a trapezoidal protective layer; the material of the trapezoidal protective layer is SiO2; the area with the largest thickness of the trapezoidal protective layer is the wiring protection area;

[0146] At least one waveguide core 22 is the target waveguide core 221;

[0147] In the step of bringing the electro-optic material layer 14 into contact with the bonding dielectric layer 23 and bonding them together,

[0148] The projection of the trapezoidal protective layer on the second substrate 20 at least partially covers the projection of the target waveguide core 221 on the second substrate 20;

[0149] The step of forming a plurality of electrodes 30 further includes:

[0150] Forming electrode wiring 31 on the side of the buried layer 13 facing away from the electro-optic material layer 14, the electrode wiring 31 also covers a part of the surface of the trapezoidal protective layer facing away from the buried layer 13 and a part of the side surface of the trapezoidal protective layer, the electrode wiring 31 is connected to at least one electrode 30; the electrode wiring 31 passes over the trapezoidal protective layer and crosses the target waveguide core 221; the projection of the electrode wiring 31 on the second substrate 20 and the projection of the target waveguide core 221 on the second substrate 20 have a projection intersection area; the projection of the wiring protection area on the second substrate 20 covers the projection intersection area.

[0151] In some alternative embodiments, before the step of bringing the electro-optic material layer 14 into contact with the bonding dielectric layer 23 and bonding them together, it further includes:

[0152] Longitudinally cutting the electro-optic material wafer to obtain a plurality of electro-optic material chips; each electro-optic material chip sequentially includes a first substrate 10, at least one protective layer 12, a buried layer 13, and an electro-optic material layer 14;

[0153] The step of bringing the electro-optic material layer 14 into contact with the bonding dielectric layer 23 and bonding them together includes:

[0154] The electro-optic material layer 14 of the electro-optic material chip is brought into contact with and bonded to the bonding dielectric layer 23 of the waveguide core wafer; wherein, the electro-optic material layer 14 of the electro-optic material chip corresponds to the waveguide core 22; the projection of the protective layer 12 on the second substrate 20 at least partially covers the projection of the waveguide core 22 on the second substrate 20.

[0155] In the related art, during the bonding process of the electro-optic material thin film chip and the silicon nitride waveguide core wafer, since the electro-optic material thin film chips are discretely distributed on the surface of the silicon nitride waveguide core wafer, during the process of removing the first substrate, due to the large thickness of the silicon substrate and the long removal time, there is uneven silicon removal, resulting in silicon residue or buried oxide layer damage, leading to an increase in the propagation loss of the silicon nitride-lithium niobate composite waveguide.

[0156] The preparation method of the heterogeneous integrated electro-optic modulation device provided in this embodiment, by providing a protective layer corresponding to the position of the waveguide core of the electro-optic material layer-waveguide core composite waveguide on the electro-optic material thin film chip, in the step of removing the first substrate, the protective layer can protect each film layer in the optical field distribution area of the composite waveguide from etching damage, and at the same time the protective layer can also make the optical field distribution of the composite waveguide not close to the surface of the protective layer, so as to avoid the buried layer surface damage of the electro-optic material thin film chip, the scattering loss and absorption loss of the optical field caused by the first substrate residue, thereby reducing the propagation loss of the electro-optic material layer-waveguide core composite waveguide and improving the stability and reliability of the heterogeneous integrated electro-optic modulation device.

[0157] In some alternative embodiments, the step of filling the groove 11 to form the protective layer 12 includes:

[0158] Filling the groove 11 to form an initial protective layer 120, the thickness of the initial protective layer 120 is greater than the depth of the groove 11, or the thickness of the initial protective layer 120 is greater than half of the width of the groove 11;

[0159] Performing a planarization process on the initial protective layer 120 until the surface of the first substrate 10 is exposed, and using the remaining initial protective layer 120 as the protective layer 12.

[0160] As Figure 2 shown, the present invention also provides a specific flow schematic diagram of a preparation method of a heterogeneous integrated electro-optic modulation device, including but not limited to steps S201 to step S208.

[0161] Step S201, providing a first substrate 10, forming a groove 11 on one side surface of the first substrate 10, the groove 11 penetrating into a part of the first substrate 10, as Figure 3 、 Figure 4A and Figure 4B shown.

[0162] In specific implementation, the material of the first substrate 10 is silicon. In some embodiments, as Figure 4A shown, the groove 11 is a single-layer groove, and the thickness of the single-layer groove is 0.5 μm to 5 μm; the width of the single-layer groove is 1 μm to 100 μm. In one example, as Figure 4B shown, two single-layer grooves with a bar-shaped and a ring-shaped top view are formed on the surface of the first substrate, corresponding to two waveguide cores in the waveguide core wafer to be formed subsequently.

[0163] Step S202, filling the groove 11 to form an initial protective layer 120, where the thickness of the initial protective layer 120 is greater than the depth of the groove 11, or the thickness of the initial protective layer 120 is greater than half of the width of the groove 11, as Figure 5 shown.

[0164] In specific implementation, the groove 11 is filled with metal or SiO2 to form an initial protective layer 120; the material of the initial protective layer 120 is SiO2 or a metal such as Cu or Al.

[0165] Step S203, performing a planarization process on the initial protective layer 120 until the surface of the first substrate 10 is exposed, and using the remaining initial protective layer 120 as the protective layer 12, as Figure 6A and Figure 6B shown.

[0166] In specific implementation, the material of the formed protective layer 12 is SiO2 or a metal such as Cu or Al. As Figure 6A shown, the surface of the formed protective layer 12 is flush with the surface of the first substrate 10, the thickness of the protective layer 12 is the same as the depth of the groove 11 of the first substrate 10, and the width of the protective layer 12 is the same as the width of the groove 11. In some embodiments, the protective layer 12 is a single-layer protective layer, and the thickness of the single-layer protective layer is 0.5 μm to 5 μm; the width of the single-layer protective layer is 1 μm to 100 μm. In one example, as Figure 6B shown, the protective layer 12 includes two single-layer protective layers with a bar-shaped and a ring-shaped top view, corresponding to two waveguide cores in the waveguide core wafer to be formed subsequently.

[0167] Step S204, forming a buried layer 13 and an electro-optic material layer 14 in sequence on the surface of the protective layer 12 facing away from the first substrate 10 to form an electro-optic material wafer, as Figure 7A and Figure 7B shown.

[0168] In specific implementation, the material of the buried layer 13 is SiO2, Al2O3, BCB thin film or a combination thereof, and the thickness of the buried layer 13 is 0.01 μm to 5 μm; the material of the electro-optic material layer 14 is a thin film material such as lithium niobate, barium titanate, or lithium tantalate; the thickness of the electro-optic material layer 14 is 0.1 μm to 0.5 μm. Among them, Figure 7BIt is a top view of the structure of an electro-optic material wafer. Figure 7A is Figure 7B a cross-sectional view taken along the AA plane.

[0169] Step S205: Provide a second substrate 20, and successively form a cladding layer 21, a waveguide core 22, and a bonding dielectric layer 23 on one side surface of the second substrate 20. The bonding dielectric layer 23 covers the side surface of the waveguide core 22 facing away from the second substrate 20 and the side surface of the waveguide core 22 to form a waveguide core wafer, as shown in Figure 8A , Figure 8B and Figure 9 .

[0170] In specific implementation, the material of the second substrate 20 can be silicon; the material of the cladding layer 21 can be silicon dioxide, and the thickness of the cladding layer 21 is 2 μm to 20 μm; for example, the second substrate 20 is a silicon substrate completely coated with thermally oxidized silicon dioxide; the material of the waveguide core 22 can be a material with a refractive index greater than that of the cladding layer 21, such as a single layer or a stack of silicon nitride, silicon, etc. (such as silicon nitride / silicon dioxide / silicon nitride); the material of the bonding dielectric layer 23 can be SiO2, Al2O3, BCB film, or a combination thereof, and the thickness of the bonding dielectric layer 23 located above the waveguide core 22 is 10 nm to 300 nm.

[0171] In one example, as shown in Figure 8A and Figure 8B , the waveguide core wafer includes two waveguide cores 22 with a strip-shaped and a ring-shaped top view, where the left one is a ring-shaped waveguide core and the right one is a strip-shaped waveguide core.

[0172] Step S206: Contact the electro-optic material layer 14 with the bonding dielectric layer 23 and bond them together; the projection of the protective layer 12 on the second substrate 20 completely covers the projection of the waveguide core 22 on the second substrate 20, as shown in Figure 10A and Figure 10B .

[0173] In specific implementation, in some embodiments, bond the electro-optic material wafer and the waveguide core wafer together, specifically by contacting and bonding the electro-optic material layer 14 with the bonding dielectric layer 23.

[0174] In other embodiments, first longitudinally cut the electro-optic material wafer to obtain a plurality of electro-optic material chips. Each electro-optic material chip successively includes a first substrate 10, a protective layer 12, a buried layer 13, and an electro-optic material layer 14; then bond the electro-optic material chip and the waveguide core wafer together, specifically by contacting and bonding the electro-optic material layer 14 of the electro-optic material chip with the bonding dielectric layer 23 of the waveguide core wafer.

[0175] In one example, as shown in Figure 10A and Figure 10BAs shown, the protective layer 12 on the left completely covers the ring waveguide core, and the protective layer 12 on the right completely covers the strip waveguide core.

[0176] Step S207, removing the first substrate 10, as Figure 11A and Figure 11B shown.

[0177] Step S208, forming a plurality of electrodes 30 on the side of the buried layer 13 facing away from the electro-optic material layer 14, and the electrodes 30 are located at corresponding positions on both sides of the waveguide core 22, as Figure 12 shown.

[0178] In specific implementation, the material of the electrode 30 can be Au, Al, Cu, etc. The distance between the electrodes 30 on both sides of the waveguide core 22 is 4 μm to 10 μm, and the thickness of the electrode 30 is 0.5 μm to 2 μm. In some examples, the electrode 30 is also located on the side of the protective layer 12.

[0179] As Figure 13 shown, the present invention also provides a specific process schematic diagram of another method for fabricating a heterogeneous integrated electro-optic modulation device, including but not limited to steps S301 to S309.

[0180] Steps S301 to S307 are the same as steps S201 to S207, and will not be elaborated here.

[0181] In specific implementation, the material of the formed protective layer 12 is metal.

[0182] Step S308, removing the protective layer 12, as Figure 14A and Figure 14B shown.

[0183] Step S309, forming a plurality of electrodes 30 on the side of the buried layer 13 facing away from the electro-optic material layer 14, and the electrodes 30 are located at corresponding positions on both sides of the waveguide core 22, as Figure 15 shown.

[0184] As Figure 16 shown, the present invention also provides a specific process schematic diagram of yet another method for fabricating a heterogeneous integrated electro-optic modulation device, including but not limited to steps S401 to S409.

[0185] Step S401, providing a first substrate 10, forming a plurality of grooves 11 on one side surface of the first substrate 10, and the grooves 11 penetrate into part of the first substrate 10; at least one groove 11 is a multi-step groove 111, and the multi-step groove 111 includes a plurality of step grooves with different depths, as Figure 17 shown.

[0186] During specific implementation, the depth of each stepped groove in the multi-stepped groove 111 is 0.5 μm to 5 μm; the maximum width of the multi-stepped groove 111 is 1 μm to 100 μm. In some embodiments, the other groove 11 is a single-layer groove, the thickness of the single-layer groove is 0.5 μm to 5 μm; the width of the single-layer groove is 1 μm to 100 μm.

[0187] Step S402, filling the groove 11 with SiO2 to form an initial protective layer 120; the thickness of the initial protective layer 120 is greater than the maximum depth of the multi-stepped groove 111, or the thickness of the initial protective layer 120 is greater than half of the maximum width of the multi-stepped groove 111.

[0188] Step S403, performing a planarization process on the initial protective layer 120 until the surface of the first substrate 10 is exposed, and using the remaining initial protective layer 120 as the protective layer 12 to form a plurality of protective layers 12; the multi-stepped groove 111 forms a multi-stepped protective layer 121; the multi-stepped protective layer 121 includes a plurality of steps with different thicknesses; the step with the largest thickness is the wiring protection area, as Figure 18A and Figure 18B shown.

[0189] In some embodiments, the projection of the multi-stepped protective layer 121 on the second substrate is adapted to completely cover the projection of the target waveguide core on the second substrate in the subsequent process, as Figure 18C shown.

[0190] During specific implementation, the material of the protective layer is SiO2, wherein the multi-stepped protective layer includes a plurality of steps with different thicknesses; the thickness of each step is 0.5 μm to 5 μm; the maximum width of the multi-stepped protective layer is 1 μm to 100 μm. In one example, as Figure 18B shown, the projection of the multi-stepped protective layer on the second substrate is adapted to partially cover the projection of the target waveguide core on the second substrate in the subsequent process; in another example, as Figure 18C shown, the projection of the multi-stepped protective layer on the second substrate is adapted to completely cover the projection of the target waveguide core on the second substrate in the subsequent process.

[0191] Step S404, sequentially forming a buried layer 13 and an electro-optic material layer 14 on the surface of the protective layer 12 facing away from the first substrate 10 to form an electro-optic material wafer, as Figure 19A and Figure 19B shown.

[0192] In some embodiments, the projection of the multi-stepped protective layer 121 on the second substrate is adapted to completely cover the projection of the target waveguide core on the second substrate in the subsequent process, as Figure 19C shown.

[0193] In one example, as Figure 19AAs shown, the electro-optical material wafer includes two protective layers 12, where the left one is a multi-step protective layer 121 and the right one is a single-layer protective layer.

[0194] Step S405: Provide a second substrate 20, and sequentially form a cladding layer 21, a plurality of waveguide cores 22, and a bonding dielectric layer 23 on one surface of the second substrate 20. At least one of the waveguide cores 22 is a target waveguide core 221. The bonding dielectric layer 23 covers the surface of the plurality of waveguide cores 22 facing away from the second substrate 20 and the side surfaces of the waveguide cores 22 to form a waveguide core wafer, as Figure 20A and Figure 20B shown.

[0195] In one example, as Figure 20A and Figure 20B shown, the waveguide core wafer includes two strip-shaped waveguide cores, where the left strip-shaped waveguide core is the target waveguide core 221.

[0196] Step S406: Bring the electro-optical material layer 14 into contact with the bonding dielectric layer 23 and bond them together; the projection of the protective layer 12 on the second substrate 20 completely covers the projection of the waveguide core 22 on the second substrate 20, where the projection of the multi-step protective layer 121 on the second substrate 20 at least partially covers the projection of the target waveguide core 221 on the second substrate 20, as Figure 21A and Figure 21B shown.

[0197] In some embodiments, the projection of the multi-step protective layer 121 on the second substrate 20 completely covers the projection of the target waveguide core 221 on the second substrate 20, as Figure 21C shown.

[0198] Specifically, the projection of each protective layer 12 on the second substrate 20 at least partially covers the projection of one waveguide core 22 on the second substrate 20, where the projection of the multi-step protective layer 121 on the second substrate 20 at least partially covers the projection of the target waveguide core 221 on the second substrate 20. In one example, as Figure 21A and Figure 21B shown, the projection of the left multi-step protective layer 121 on the second substrate 20 partially covers the projection of the target waveguide core 221 on the second substrate 20; the projection of the right single-layer protective layer on the second substrate 20 completely covers the projection of one waveguide core 22 on the second substrate 20. In another example, as Figure 21A and Figure 21C shown, the projection of the left multi-step protective layer 121 on the second substrate 20 completely covers the projection of the target waveguide core 221 on the second substrate 20.

[0199] Step S407: Remove the first substrate 10, as Figure 22A and Figure 22Bas shown

[0200] In some embodiments, the projection of the multi-step protective layer 121 on the second substrate 20 completely covers the projection of the target waveguide core 221 on the second substrate 20, as Figure 22C shown

[0201] Step S408: Form a plurality of electrodes 30 and electrode wirings 31 on the side of the buried layer 13 facing away from the electro-optic material layer 14. The electrodes 30 are located at corresponding positions on both sides of the waveguide core 22. The electrode wiring 31 also covers a part of the surface of the multi-step protective layer 121 facing away from the buried layer 13 and a part of the side surface of the multi-step protective layer 121. The electrode wiring 31 is connected to at least one electrode 30. The electrode wiring 31 passes over the target waveguide core 221 through the multi-step protective layer 121. The projection of the electrode wiring 31 on the second substrate 20 and the projection of the target waveguide core 221 on the second substrate 20 have a projection intersection area. The wiring protection area of the multi-step groove 111 covers the projection intersection area on the second substrate 20, as Figure 23A and Figure 23B shown

[0202] In some embodiments, the projection of the multi-step protective layer 121 on the second substrate 20 completely covers the projection of the target waveguide core 221 on the second substrate 20, as Figure 21C shown

[0203] In one example, two electrodes 30 and electrode wirings 31 are formed above the side of the buried layer 13 facing away from the electro-optic material layer 14. A part of the electrode wiring 31 is located above the buried layer 13, and a part is located above the multi-step protective layer 121. The electrode wiring 31 also covers a part of the surface of the multi-step protective layer 121 facing away from the buried layer 13 and a part of the side surface of the multi-step protective layer 121. The two electrodes 30 are respectively located at corresponding positions on both sides of the waveguide core 22. The electrode wiring 31 is connected to the left electrode 30, and then the left electrode 30 is led out. The electrode wiring 31 passes over the target waveguide core 221 through the left multi-step protective layer 121, as Figure 23A 、 Figure 23B and Figure 23C shown

[0204] This embodiment also provides a heterogeneous integrated electro-optic modulation device, as Figure 15 shown. The heterogeneous integrated electro-optic modulation device includes:

[0205] A waveguide core wafer, which includes a stacked second substrate 20, a cladding 21, a waveguide core 22, and a bonding dielectric layer 23. The bonding dielectric layer 23 covers the surface of the side of the waveguide core 22 facing away from the second substrate 20 and the side surface of the waveguide core 22;

[0206] An electro-optic material layer 14, which is located on the surface of the bonding dielectric layer 23 facing away from the waveguide core 22;

[0207] The buried layer 13 is located on one surface of the electro-optic material layer 14 facing away from the bonding dielectric layer 23;

[0208] A plurality of electrodes 30 are located on one side of the buried layer 13 facing away from the electro-optic material layer 14, and the electrodes 30 are located at corresponding positions on both sides of the waveguide core 22.

[0209] The heterogeneous integrated electro-optic modulation device provided in this embodiment is prepared by the preparation method of the heterogeneous integrated electro-optic modulation device as Figure 1 shown, which can avoid the scattering loss and absorption loss of the light field caused by buried layer damage and the residue of the first substrate, thereby reducing the propagation loss of the electro-optic material layer-waveguide core composite waveguide and improving the stability and reliability of the heterogeneous integrated electro-optic modulation device.

[0210] In some alternative embodiments, as Figure 12 shown, the heterogeneous integrated electro-optic modulation device further includes:

[0211] A protective layer 12 is located on one surface of the buried layer 13 facing away from the waveguide core 22, and the projection of the protective layer 12 on the second substrate 20 at least partially covers the projection of the waveguide core 22 on the second substrate 20;

[0212] The material of the protective layer 12 is SiO2.

[0213] For the heterogeneous integrated electro-optic modulation device provided in this embodiment, the protective layer and the buried layer below it together serve as the protective cladding of the electro-optic material layer-waveguide core composite waveguide, which can reduce the damage to the electro-optic material layer-waveguide core composite waveguide during the process, improve the reliability and yield of the device; and can also reduce the influence of the relatively thick buried layer on the electro-optic modulation efficiency and speed, thereby improving the electro-optic modulation efficiency and speed of the heterogeneous integrated electro-optic modulation device.

[0214] In some alternative embodiments, the protective layer 12 includes a single-layer protective layer;

[0215] The thickness of the single-layer protective layer is 0.5 μm to 5 μm; the width of the single-layer protective layer is 1 μm to 100 μm.

[0216] In some alternative embodiments, as Figure 23A 、 Figure 23B and Figure 23C shown, the protective layer 12 includes a multi-step protective layer 121;

[0217] The waveguide core wafer includes at least one target waveguide core 221;

[0218] The projection of the multi-step protective layer 121 on the second substrate 20 at least partially covers the projection of the target waveguide core 221 on the second substrate 20;

[0219] The heterogeneous integrated electro-optic modulation device further includes:

[0220] An electrode wiring 31, located on the side of the buried layer 13 facing away from the electro-optic material layer 14. The electrode wiring 31 also covers a part of the surface of the multi-step protective layer 121 facing away from the buried layer 13 and a part of the side surface of the multi-step protective layer 121. The electrode wiring 31 is connected to at least one electrode 30; the electrode wiring 31 passes over the target waveguide core 221 through the multi-step protective layer 121; there is a projection intersection area between the projection of the electrode wiring 31 on the second substrate 20 and the projection of the target waveguide core 221 on the second substrate 20.

[0221] In one example, as Figure 23B shown, the projection of the multi-step protective layer 121 on the second substrate 20 partially covers the projection of the target waveguide core 221 on the second substrate 20; in another example, as Figure 23C shown, the projection of the multi-step protective layer 121 on the second substrate 20 completely covers the projection of the target waveguide core 221 on the second substrate 20.

[0222] In some alternative embodiments, the multi-step protective layer 121 includes multiple steps with different thicknesses; the thickness of each step is 0.5 μm to 5 μm; the maximum width of the multi-step protective layer 121 is 1 μm to 100 μm;

[0223] Among them, the step with the largest thickness is the wiring protection area; the projection of the wiring protection area on the second substrate 20 covers the projection intersection area, as Figure 23A , Figure 23B and Figure 23C shown.

[0224] For the heterogeneous integrated electro-optic modulation device provided in this embodiment, by setting the multi-step protective layer and the projection of the wiring protection area on the second substrate covering the projection intersection area, the distance between the electrode wiring and the electro-optic material layer - target waveguide core composite waveguide can be increased, and the propagation loss of the composite waveguide can be reduced.

[0225] In some alternative embodiments, the material of the first substrate 10 is silicon;

[0226] The material of the buried layer 13 is SiO2, Al2O3, BCB thin film or a combination thereof, and the thickness of the buried layer 13 is 0.01 μm to 5 μm;

[0227] The material of the electro-optic material layer 14 is a thin film material such as lithium niobate, barium titanate, lithium tantalate, etc.; the thickness of the electro-optic material layer 14 is 0.1 μm to 0.5 μm;

[0228] The material of the protective layer 12 is SiO2.

[0229] In some alternative embodiments, the material of the second substrate 20 is silicon; the material of the cladding layer 21 is silicon dioxide, and the thickness of the cladding layer 21 is 2 μm to 20 μm;

[0230] The material of the waveguide core 22 has a refractive index greater than that of the cladding layer 21; optionally, the material of the waveguide core 22 is silicon nitride, a single layer or a stack of silicon, such as a silicon nitride / silicon dioxide / silicon nitride stack;

[0231] The material of the bonding dielectric layer 23 is SiO2, Al2O3, BCB thin film, or a combination thereof, and the thickness of the bonding dielectric layer 23 above the waveguide core 22 is 10 nm to 300 nm.

[0232] In some alternative embodiments, the second substrate 20 is a silicon substrate completely coated with thermally oxidized silicon dioxide.

[0233] In some alternative embodiments, the materials of the electrodes 30 and the electrode wiring 31 can be Au, Al, Cu, etc. The distance between the electrodes 30 on both sides of the waveguide core 22 is 4 μm to 10 μm, and the thickness of the electrodes 30 is 0.5 μm to 2 μm.

[0234] In the description of this specification, the descriptions with reference to terms such as "this embodiment", "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" 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. Furthermore, the terms "first" and "second" are only used for descriptive purposes and cannot be construed 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, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0235] In the above description, no detailed explanations are given for the technical details such as the composition and etching of each layer. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. of the desired shapes. Additionally, 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. Moreover, although the above embodiments are described separately, this does not mean that the measures in each embodiment cannot be advantageously combined and used.

[0236] 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 only. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and 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 Comprising: Providing a first substrate, forming a groove on one side surface of the first substrate, and the groove penetrating into a part of the first substrate; Filling the groove to form a protective layer; Successively forming a buried layer and an electro-optic material layer on the side surface of the protective layer facing away from the first substrate to form an electro-optic material wafer; Providing a second substrate, successively forming a cladding layer, a waveguide core, and a bonding dielectric layer on one side surface of the second substrate, and 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 to form a waveguide core wafer; Bringing the electro-optic material layer into contact with the bonding dielectric layer and bonding them together; the projection of the protective layer on the second substrate at least partially covers the projection of the waveguide core on the second substrate; Removing the first substrate; Forming a plurality of electrodes on the side of the buried layer facing away from the electro-optic material layer, and the electrodes being located at corresponding positions on both sides of the waveguide core.

2. The method for preparing a heterogeneous integrated electro-optic modulation device according to claim 1, wherein In the step of bringing the electro-optic material layer into contact with the bonding dielectric layer and bonding them together, the projection of the protective layer on the second substrate completely covers the projection of the waveguide core on the second substrate.

3. The method for preparing a heterogeneous integrated electro-optic modulation device according to claim 2, wherein The material of the protective layer is metal or SiO2.

4. The method for preparing a heterogeneous integrated electro-optic modulation device according to claim 3, wherein The material of the protective layer is metal; After the step of removing the first substrate and before the step of forming the plurality of electrodes, it further includes: removing the protective layer.

5. The method for preparing a heterogeneous integrated electro-optic modulation device according to claim 3, wherein The material of the protective layer is metal; The projection of the protective layer on the second substrate also covers both sides of the projection of the waveguide core on the second substrate; The step of forming the plurality of electrodes includes: Removing the part of the protective layer corresponding to the waveguide core, and using the remaining part of the protective layer corresponding to both sides of the waveguide core as the plurality of electrodes.

6. The method for preparing a heterogeneous integrated electro-optic modulation device according to claim 1, wherein The electro-optic material wafer includes a plurality of protective layers; The waveguide core wafer includes a plurality of waveguide cores, and the bonding dielectric layer covers the plurality of waveguide cores; In the step of bringing the electro-optic material layer into contact with the bonding dielectric layer and bonding them together, The projection of each protective layer on the second substrate at least partially covers the projection of one waveguide core on the second substrate.

7. The method for preparing a heterogeneous integrated electro-optic modulation device according to claim 6, wherein At least one of the protective layers is a multi-step protective layer; the material of the multi-step protective layer is SiO2; At least one of the waveguide cores is a target waveguide core; In the step of bringing the electro-optic material layer into contact with the bonding dielectric layer and bonding them together, The projection of the multi-step protective layer on the second substrate at least partially covers the projection of the target waveguide core on the second substrate; The step of forming a plurality of electrodes further includes: Forming an electrode wiring on a side of the buried layer facing away from the electro-optic material layer, the electrode wiring further covering a part of the surface of the multi-step protective layer facing away from the buried layer and a part of the side surface of the multi-step protective layer, the electrode wiring being connected to at least one of the electrodes; the electrode wiring passes through the multi-step protective layer and straddles the target waveguide core; a projection intersection area exists between a projection of the electrode wiring on the second substrate and a projection of the target waveguide core on the second substrate.

8. The method for manufacturing a heterogeneous integrated electro-optic modulation device according to claim 7, wherein In the step of forming the groove, at least one of the grooves is a multi-step groove, the multi-step groove includes a plurality of stepped grooves with different depths, and the depth of each stepped groove is 0.5 μm to 5 μm; The maximum width of the multi-step groove is 1 μm to 100 μm; The step of filling the groove to form a protective layer includes: Filling the groove with SiO2 to form a protective layer, wherein filling the multi-step groove forms a multi-step protective layer; the multi-step protective layer includes a plurality of steps with different thicknesses; the step with the largest thickness is the wiring protection area; In the step of forming the electrode wiring, a projection of the wiring protection area on the second substrate covers the projection intersection area.

9. The method for manufacturing a heterogeneous integrated electro-optic modulation device according to claim 1, wherein Before the step of bringing the electro-optic material layer into contact with the bonding dielectric layer and bonding them together, it further includes: Longitudinally cutting the electro-optic material wafer to obtain a plurality of electro-optic material chips; each electro-optic material chip sequentially includes a first substrate, at least one of the protective layers, a buried layer, and an electro-optic material layer; The step of bringing the electro-optic material layer into contact with the bonding dielectric layer and bonding them together includes: Bringing the electro-optic material layer of the electro-optic material chip into contact with the bonding dielectric layer of the waveguide core wafer and bonding them together; wherein, the electro-optic material layer of the electro-optic material chip corresponds to the waveguide core; a projection of the protective layer on the second substrate at least partially covers a projection of the waveguide core on the second substrate.

10. The method for manufacturing a heterogeneous integrated electro-optic modulation device according to claim 1, wherein The step of filling the groove to form a protective layer includes: Filling the groove to form an initial protective layer, the thickness of the initial protective layer being greater than the depth of the groove, or the thickness of the initial protective layer being greater than half of the width of the groove; Performing a planarization process on the initial protective layer until the surface of the first substrate is exposed, and using the remaining initial protective layer as the protective layer.

11. A heterogeneous integrated electro-optic modulation device, characterized in that Including: A waveguide core wafer, the waveguide core wafer includes a stacked second substrate, a cladding layer, a waveguide core, and a bonding dielectric layer, the bonding dielectric layer covering a surface of the waveguide core facing away from the second substrate and the side surface of the waveguide core; An electro-optic material layer, located on a surface of the bonding dielectric layer facing away from the waveguide core; A buried layer, located on a surface of the electro-optic material layer facing away from the bonding dielectric layer; Multiple electrodes are located on the side of the buried layer facing away from the electro-optic material layer, and the electrodes are located at corresponding positions on both sides of the waveguide core.

12. The heterogeneous integrated electro-optic modulation device according to claim 11, wherein the heterogeneous integrated electro-optic modulation device further comprises: a protective layer located on the surface of the buried layer facing away from the waveguide core, and the projection of the protective layer on the second substrate at least partially covers the projection of the waveguide core on the second substrate; the material of the protective layer is SiO2.

13. The heterogeneous integrated electro-optic modulation device according to claim 12, wherein the protective layer comprises a single-layer protective layer; the thickness of the single-layer protective layer is 0.5 μm to 5 μm; the width of the single-layer protective layer is 1 μm to 100 μm.

14. The heterogeneous integrated electro-optic modulation device according to claim 12, wherein the protective layer comprises a multi-step protective layer; the waveguide core wafer includes at least one target waveguide core; the projection of the multi-step protective layer on the second substrate at least partially covers the projection of the target waveguide core on the second substrate; the heterogeneous integrated electro-optic modulation device further comprises: electrode wiring located on the side of the buried layer facing away from the electro-optic material layer, the electrode wiring also covers a part of the surface of the multi-step protective layer facing away from the buried layer and a part of the side surface of the multi-step protective layer, the electrode wiring is connected to at least one of the electrodes; the electrode wiring passes over the target waveguide core through the multi-step protective layer; there is a projection intersection area between the projection of the electrode wiring on the second substrate and the projection of the target waveguide core on the second substrate.

15. The heterogeneous integrated electro-optic modulation device according to claim 14, wherein the multi-step protective layer comprises multiple steps with different thicknesses; the thickness of each step is 0.5 μm to 5 μm; the maximum width of the multi-step protective layer is 1 μm to 100 μm; wherein the step with the largest thickness is the wiring protection area; the projection of the wiring protection area on the second substrate covers the projection intersection area.

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