Heterogeneous integrated electro-optical modulator with upper and lower electrode structure and preparation method thereof

Abstract

The invention relates to the technical field of semiconductors, and discloses a heterogeneous integrated electro-optical modulator with an upper and lower electrode structure and a preparation method thereof, and the preparation method comprises the steps: forming a first waveguide core and a lower electrode groove at one side, opposite to a first substrate, of a lower cladding, and forming a lower electrode in the lower electrode groove; forming a bonding dielectric layer wrapping the lower electrode, the first waveguide core and the lower wrapping layer; forming an electro-optical material layer on the partial surface of one side, back to the lower electrode, of the bonding dielectric layer; forming an intermediate layer, a second waveguide core and an upper electrode on the surface of the electro-optical material layer, wherein the projection part of the second waveguide core on the first substrate covers the projection of the first tapered part of the first waveguide core on the first substrate; the projection of the electro-optical material layer on the first substrate at least partially covers the projection of the second waveguide core on the first substrate. The integration level of the optical device and the design flexibility of the optical device can be improved, the manufacturing difficulty of the lower electrode is reduced, and the process efficiency and the yield are improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a heterogeneous integrated electro-optical modulation device with upper and lower electrode structures and a preparation method thereof. Background Art

[0002] The integrated photonics platform based on stoichiometric silicon nitride waveguide core has the advantages of CMOS process compatibility and low propagation loss in a wide spectral range. Since the electro-optical effect of silicon nitride material is weak, it is necessary to heterogeneously integrate thin film materials with strong electro-optical effect, such as lithium niobate, so that the silicon nitride waveguide core and thin film lithium niobate form a composite waveguide core, thereby realizing efficient electro-optic modulation devices on the silicon nitride photonics platform. Existing silicon nitride-lithium niobate electro-optic modulation devices are generally divided into horizontal electrode structure devices and upper and lower electrode structure devices.

[0003] For the electro-optic modulator with horizontal electrode structure, X-cut thin-film lithium niobate and silicon nitride waveguide core are used to form a composite waveguide core. The silicon nitride waveguide core is arranged along the Y direction of the thin-film lithium niobate, and the electrodes are located on both sides of the silicon nitride waveguide core to generate an electric field parallel to the Z direction of the lithium niobate. The disadvantages are: 1) The anisotropy of the electro-optic coefficient of lithium niobate, when the electrode and the waveguide core are bent or folded at the same time, the optical phase modulation efficiency will be reduced or the optical phase modulation before and after the folding will cancel each other out, so the electro-optic modulator is usually configured in a straight line; 2) The electrode and the silicon nitride waveguide core in the device structure are at the same horizontal position or the distance in the vertical direction is small, and when the waveguide core is close to the electrode, it will cause a higher absorption loss, resulting in no waveguide core distribution in the area where the electrode is located; Therefore, the design flexibility of the photonic integrated circuit of the heterogeneous integrated electro-optic modulator with horizontal electrode structure is limited and the integration is reduced.

[0004] For the electro-optic modulation device with upper and lower electrode structure, a composite waveguide core is formed by using Z-cut thin film lithium niobate and silicon nitride waveguide core. The electrodes are located on the upper and lower sides of the silicon nitride-lithium niobate composite waveguide core to generate an electric field parallel to the Z direction of lithium niobate, and the TM mode light propagates along the composite waveguide core. However, there are also certain defects: the metal electrode located below the silicon nitride waveguide core cannot withstand the high temperature process when the stoichiometric silicon nitride film is deposited, which makes it difficult to manufacture the device with this structure.

[0005] Therefore, a solution is needed to prevent the electro-optical modulation device with an upper and lower electrode structure from being subjected to a high temperature process when forming a metal electrode located below the silicon nitride waveguide core, thereby reducing the process difficulty, improving the process efficiency, and improving the reliability and process of the electro-optical modulation device. Summary of the invention

[0006] In view of this, the present invention provides a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure and a preparation method thereof, so as to solve the problems that the design flexibility of the photonic integrated circuit of the electro-optic modulation device with a horizontal electrode structure in the related art is limited, the integration degree is reduced, and the metal electrode under the silicon nitride waveguide core in the electro-optic modulation device with an upper and lower electrode structure cannot withstand the high-temperature process during the deposition of the stoichiometric silicon nitride thin film, and the process difficulty is relatively high.

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

[0008] Providing a first substrate with a lower cladding covered on its surface, and forming at least two first waveguide cores on a partial surface of the lower cladding on the side facing away from the first substrate, each first waveguide core including a first intermediate portion having a first width and a first tapered portion with a width gradually decreasing from the first width;

[0009] Forming a lower electrode groove on a partial surface of the lower cladding on the side facing away from the first substrate, and forming a lower electrode in the lower electrode groove; the lower electrode groove penetrates into a partial thickness of the lower cladding; the thickness of the lower electrode is less than or equal to the depth of the lower electrode groove; the projection of the lower electrode on the first substrate does not overlap with the projection of the first waveguide core on the first substrate;

[0010] Forming a bonding dielectric layer on the side surface of the lower cladding on the side facing away from the first substrate, and the bonding dielectric layer covers the lower electrode, the first waveguide core and the lower cladding;

[0011] Bonding and forming an electro-optic material layer on a partial surface of the bonding dielectric layer on the side facing away from the lower electrode; the projection of the electro-optic material layer on the first substrate covers a partial projection of the lower electrode on the first substrate; the electro-optic material layer includes an equal-thickness region in the middle and a slope structure at the edge; the thickness of the slope structure gradually decreases along the direction away from the equal-thickness region;

[0012] Forming an intermediate layer on the side surface of the electro-optic material layer on the side facing away from the bonding dielectric layer, and the intermediate layer covers the side surface of the electro-optic material layer on the side facing away from the bonding dielectric layer and the side surface of the electro-optic material layer;

[0013] Forming a second waveguide core on a partial surface of the intermediate layer on the side facing away from the lower electrode, and the projection of the second waveguide core on the first substrate partially covers the projection of the first tapered portion of the first waveguide core on the first substrate; the projection of the first waveguide core on the first substrate is located at both ends of the projection of the second waveguide core on the first substrate; the projection of the electro-optic material layer on the first substrate at least partially covers the projection of the second waveguide core on the first substrate;

[0014] Forming an upper electrode on the side surface of the second waveguide core on the side facing away from the electro-optic material layer.

[0015] The preparation method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided by the present invention first forms the first waveguide core, then forms the lower electrode and the electro-optic material layer, and finally forms the second waveguide core and the lower electrode. The light propagating in the first waveguide core (such as stoichiometric silicon nitride) can be coupled to the second waveguide core (such as non-stoichiometric silicon nitride waveguide core) through layer coupling, and then transition to the second waveguide core - electro-optic material layer composite waveguide core through the slope structure of the electro-optic material layer. Or the light propagating in the first waveguide core can be transitioned to the first waveguide core - electro-optic material layer composite waveguide core with low loss through the slope structure of the electro-optic material layer, and then coupled to the second waveguide core - electro-optic material layer composite waveguide core through layer coupling. On the one hand, by arranging the upper electrode and the lower electrode at the corresponding position of the second waveguide core to form a heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure, the defect that the electrodes and the waveguide core are linearly configured in the horizontal electrode structure device can be solved, so that the waveguide core and the electrodes in the device can be bent and folded as needed, improving the integration degree of the optical device and the flexibility of the optical device design. On the other hand, the lower electrode is formed after the first waveguide core, and there is no overlap between the projection of the lower electrode on the first substrate and the projection of the first waveguide core on the first substrate, which can solve the problem that it is difficult to fabricate the lower electrode when forming a heterogeneous integrated electro-optic modulation device with the upper and lower electrode configuration on the stoichiometric silicon nitride photonics platform, making the fabrication of the lower electrode not affected by the preparation process of the first waveguide core, reducing the fabrication difficulty of the lower electrode, and improving the process efficiency and process yield. Therefore, the preparation method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided by the present invention can improve the integration degree of the optical device and the flexibility of the optical device design, reduce the fabrication difficulty of the lower electrode, and improve the process efficiency and process yield. In addition, the slope structure of the electro-optic material layer can provide a low-loss optical transition between the waveguide core and / or the composite waveguide core, without requiring the refractive index of the second waveguide core to be higher than that of the electro-optic material layer, relaxing the restrictions on the material of the second waveguide core. For example, it can avoid using rich silicon nitride with a refractive index higher than that of the electro-optic material layer but higher absorption loss for the second waveguide core.

[0016] In an alternative embodiment, in the step of forming the second waveguide core, the second waveguide core includes a second middle portion having a second width and two second tapered portions with widths gradually decreasing from the second width; the projections of the second tapered portions at both ends of the second waveguide core on the first substrate respectively overlap with the projections of a first tapered portion on the first substrate, and the taper directions of the overlapping first tapered portion and the second tapered portion are inverted;

[0017] The projection of the equal-thickness region of the electro-optic material layer on the first substrate at least partially covers the projection of the second middle portion on the first substrate; the projection of the slope structure of the electro-optic material layer on the first substrate covers a part of the projection of the first waveguide core on the first substrate or a part of the projection of the second waveguide core on the first substrate.

[0018] The preparation method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided by the present invention forms a second waveguide core - electro-optic material layer composite waveguide core through the second waveguide core and the electro-optic material layer, and the first tapered portion and the second tapered portion can provide optical field coupling transition between the second waveguide core and the first waveguide core, or between the second waveguide core - electro-optic material layer composite waveguide core and the first waveguide core - electro-optic material layer composite waveguide core, so that the optical signal propagated by the first waveguide core enters the second waveguide core - electro-optic material layer composite waveguide core through the first tapered portion, the second tapered portion and the electro-optic material layer for electro-optic modulation, and then returns to the first waveguide core through the second tapered portion, the first tapered portion and the electro-optic material layer, which can reduce the loss in the optical signal transmission process and solve the problem that it is difficult to fabricate the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure on the silicon nitride photonics platform. In the transition part between the first waveguide core and the second waveguide core, or between the first waveguide core - electro-optic material layer composite waveguide core and the second waveguide core - electro-optic material layer composite waveguide core, by setting the first tapered portion and the second tapered portion to be inverted and partially overlapped, the optical field transition loss can be reduced.

[0019] In an alternative embodiment, the projection of the equal-thickness region of the electro-optic material layer on the first substrate completely covers the projection of the second middle portion on the first substrate, the projection of the second tapered portion on the first substrate, and the projection of the first tapered portion on the first substrate;

[0020] The projection of the slope structure of the electro-optic material layer on the first substrate covers a partial projection of the first middle portion on the first substrate.

[0021] The preparation method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structures provided by the present invention is such that the projection of the equal-thickness region of the electro-optic material layer on the first substrate completely covers the projection of the second middle part on the first substrate, the projection of the second tapered part on the first substrate, and the projection of the first tapered part on the first substrate; the projection of the slope structure of the electro-optic material layer on the first substrate covers a partial projection of the first middle part on the first substrate, and the first waveguide core - electro-optic material layer composite waveguide core and the second waveguide core - electro-optic material layer composite waveguide core can be formed simultaneously. In the electro-optic modulation device, the optical signal first passes through the slope structure of the electro-optic material layer, transitions from the first waveguide core to the first waveguide core - electro-optic material layer composite waveguide core, and then passes through the first tapered part and the second tapered part, transitioning from the first waveguide core - electro-optic material layer composite waveguide core to the second waveguide core - electro-optic material layer composite waveguide core; after the optical signal in the second waveguide core - electro-optic material layer composite waveguide core is electro-optically modulated, it passes through the second tapered part and the first tapered part again, transitioning from the second waveguide core - electro-optic material layer composite waveguide core to the first waveguide core - electro-optic material layer composite waveguide core, and then passes through the slope structure of the electro-optic material layer, transitioning from the first waveguide core - electro-optic material layer composite waveguide core to the first waveguide core. Therefore, the formed electro-optic modulation device can reduce the loss during the optical signal transmission process and improve the optical field transition efficiency. In addition, since only the optical transition between two structures is involved in each step of the optical field transition, there are fewer variables, and the optimization design is relatively simple, and a higher transition efficiency can be achieved.

[0022] In an alternative embodiment, the projection of the electro-optic material layer on the first substrate partially covers the projection of the second middle part on the first substrate;

[0023] The projection of the electro-optic material layer on the first substrate does not overlap with the projection of the first tapered part on the first substrate; the projection of the electro-optic material layer on the first substrate does not overlap with the projection of the second tapered part on the first substrate.

[0024] The preparation method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structures provided by the present invention is such that the projected part of the electro-optic material layer on the first substrate covers the projection of the second middle part on the first substrate; the projection of the electro-optic material layer on the first substrate does not overlap with the projection of the first tapered part on the first substrate; the projection of the electro-optic material layer on the first substrate does not overlap with the projection of the second tapered part on the first substrate, and the overlapping part of the second waveguide core and the electro-optic material layer can form a second waveguide core - electro-optic material layer composite waveguide core. In the electro-optic modulation device, the optical signal first passes through the first tapered part and the second tapered part, transitions from the first waveguide core to the second waveguide core, and then passes through the slope structure of the electro-optic material layer to transition from the second waveguide core to the second waveguide core - electro-optic material layer composite waveguide core; after the optical signal in the second waveguide core - electro-optic material layer composite waveguide core is electro-optically modulated, it passes through the slope structure of the electro-optic material layer to transition from the second waveguide core - electro-optic material layer composite waveguide core to the second waveguide core, and then passes through the second tapered part and the first tapered part to transition from the second waveguide core to the first waveguide core. Therefore, the formed electro-optic modulation device can reduce the loss during the optical signal transmission and improve the optical field transition efficiency. In addition, since only the optical transition between two structures is involved in each step of the optical field transition, there are fewer variables, and the optimization design is relatively simple, and a higher transition efficiency can be achieved.

[0025] In an optional implementation manner, in the step of forming the lower electrode, the lower electrode includes a first electro-optic modulation part, a first contact part, and a first transition part; the first transition part is located between the first electro-optic modulation part and the first contact part;

[0026] In the step of forming the electro-optic material layer, the projection of the electro-optic material layer on the first substrate covers the projection of the first electro-optic modulation part on the first substrate;

[0027] In the step of forming the upper electrode, the upper electrode includes a second electro-optic modulation part, a second contact part, and a second transition part; the second transition part is located between the second electro-optic modulation part and the second contact part; the projection of the second electro-optic modulation part on the first substrate at least partially overlaps with the projection of the first electro-optic modulation part on the first substrate, and the overlapping projection at least covers a part of the projection of the second middle part on the first substrate.

[0028] In an optional implementation manner, the projections of the second tapered parts at both ends of the second waveguide core on the first substrate are respectively centered and aligned with the projections of the first tapered parts of a first waveguide core on the first substrate;

[0029] The second middle part of the second waveguide core is one or a combination of a straight waveguide core, a bent waveguide core, and a spiral waveguide core; the projection of the lower electrode on the first substrate at least covers a part of the projection of the second middle part on the first substrate.

[0030] The preparation method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided by the present invention is such that the projection of the second electro-optic modulation part on the first substrate overlaps at least partially with the projection of the first electro-optic modulation part on the first substrate, and the overlapping projection covers at least part of the projection of the second intermediate part on the first substrate. The projection of the electro-optic material layer on the first substrate covers the projection of the first electro-optic modulation part on the first substrate, so that the electric field provided by this electrode structure can always be parallel to the crystal orientation with a high electro-optic coefficient of the electro-optic material layer, and the optical phase modulation efficiency does not decrease or even cancel out with the bending and folding of the waveguide core. Thus, the waveguide core can be flexibly designed according to needs. The second intermediate part of the second waveguide core can be set as one or a combination of a straight waveguide core, a bent waveguide core, and a spiral waveguide core according to requirements, which can improve the integration degree of the photonic integrated circuit.

[0031] In an alternative embodiment, after the step of forming the bonding dielectric layer, it includes:

[0032] Form a first via on the side of the bonding dielectric layer facing away from the first contact part. The first via penetrates the bonding dielectric layer and exposes part of the first contact part;

[0033] Fill the first via to form a first metal plug.

[0034] In an alternative embodiment, the step of forming the upper electrode on the side of the second waveguide core facing away from the electro-optic material layer includes:

[0035] Form an upper cladding layer on the side surface of the second waveguide core facing away from the electro-optic material layer. The upper cladding layer also covers the side surface of the second waveguide core and the side surface of the intermediate layer facing away from the bonding dielectric layer;

[0036] Form a second via on the side surface of the upper cladding layer facing away from the first metal plug. The second via penetrates the upper cladding layer and the intermediate layer and exposes at least part of the first metal plug;

[0037] Fill the second via to form a second metal plug; the second metal plug is connected to the first contact part of the lower electrode through the first metal plug;

[0038] Form an upper electrode on the side of the electro-optic material layer facing away from the intermediate layer, and form a lower electrode pad on the side of the upper cladding layer facing away from the second metal plug; the lower electrode pad contacts and connects with the second metal plug; the lower electrode pad is connected to the first contact part of the lower electrode through the first metal plug and the second metal plug.

[0039] In an alternative embodiment, the process of forming the first waveguide core is the LPCVD process; the material of the first waveguide core is stoichiometric silicon nitride or a silicon nitride / silicon dioxide stack;

[0040] The process of forming the second waveguide core is the PECVD process; the material of the second waveguide core is silicon or silicon nitride.

[0041] The preparation method of the heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure provided by the present invention first forms a stoichiometric silicon nitride as the first waveguide core through a high-temperature LPCVD process. Then, after forming the lower electrode, a second waveguide core is formed through a low-temperature PECVD process, so that the production of the lower electrode does not go through a high-temperature process, which can avoid the influence of the high-temperature process of the first waveguide core on the lower electrode, reduce the production difficulty of the lower electrode, improve the process efficiency and process yield, and thus solve the problem that it is not easy to fabricate the lower electrode when forming a heterogeneous integrated electro-optic modulation device with an upper and lower electrode configuration on a stoichiometric silicon nitride photonics platform.

[0042] Second, the present invention provides a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure. The heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure includes:

[0043] A first substrate;

[0044] A lower cladding layer located on one side surface of the first substrate;

[0045] At least two first waveguide cores located on a partial surface of the lower cladding layer on the side facing away from the first substrate. Each first waveguide core includes a first intermediate portion with a first width and a first tapered portion with a width gradually decreasing from the first width;

[0046] A lower electrode groove located on the side of the lower cladding layer facing away from the first substrate, and the lower electrode groove penetrates into a part of the thickness of the lower cladding layer;

[0047] A lower electrode located in the lower electrode groove; the thickness of the lower electrode is less than or equal to the depth of the lower electrode groove; the projection of the electrode on the first substrate does not overlap with the projection of the first waveguide core on the first substrate;

[0048] A bonding dielectric layer located on the side surface of the lower cladding layer facing away from the first substrate, and the bonding dielectric layer covers the lower electrode, the first waveguide core, and the lower cladding layer;

[0049] An electro-optic material layer located on a partial surface of the bonding dielectric layer on the side facing away from the lower electrode; the projection on the first substrate covers a part of the projection of the lower electrode on the first substrate; the electro-optic material layer includes an equal-thickness region in the middle and a slope structure at the edge; the thickness of the slope structure gradually decreases along the direction away from the equal-thickness region;

[0050] An intermediate layer located on the side surface of the electro-optic material layer facing away from the bonding dielectric layer, and the intermediate layer covers the side surface of the electro-optic material layer facing away from the bonding dielectric layer and the side surface of the electro-optic material layer;

[0051] The second waveguide core is located on a partial surface of the middle layer on the side facing away from the lower electrode; the projection of the second waveguide core on the first substrate partially covers the projection of the first tapered portion of the first waveguide core on the first substrate; the projection of the first waveguide core on the first substrate is located at both ends of the projection of the second waveguide core on the first substrate; the projection of the electro-optic material layer on the first substrate at least partially covers the projection of the second waveguide core on the first substrate;

[0052] The upper electrode is located on the side of the second waveguide core facing away from the electro-optic material layer.

[0053] The heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided by the present invention is prepared by the preparation method of the heterogeneous integrated electro-optic modulation device with the above upper and lower electrode structure. The upper electrode and the lower electrode are arranged at the corresponding positions of the second waveguide core to form a heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure, which can solve the defect that the electrodes and the waveguide core in the horizontal electrode structure device are linearly configured, so that the waveguide core and the electrodes in the device can be bent and folded as needed, improving the integration degree of the optical device and the flexibility of the optical device design.

[0054] In an optional embodiment, the second waveguide core includes a second middle portion with a second width and two second tapered portions with widths gradually decreasing from the second width;

[0055] The projections of the second tapered portions at both ends of the second waveguide core on the first substrate respectively overlap partially with the projection of a first tapered portion on the first substrate, and the tapered directions of the overlapping first tapered portion and the second tapered portion are inverted;

[0056] The projection of the equal-thickness region of the electro-optic material layer on the first substrate at least partially covers the projection of the second middle portion on the first substrate; the projection of the slope structure of the electro-optic material layer on the first substrate covers a partial projection of the first waveguide core on the first substrate or a partial projection of the second waveguide core on the first substrate.

[0057] In an optional embodiment, the projection of the equal-thickness region of the electro-optic material layer on the first substrate completely covers the projection of the second middle portion on the first substrate, the projection of the second tapered portion on the first substrate, and the projection of the first tapered portion on the first substrate;

[0058] The projection of the slope structure of the electro-optic material layer on the first substrate covers a partial projection of the first middle portion on the first substrate.

[0059] In an optional embodiment, the projection of the electro-optic material layer on the first substrate partially covers the projection of the second middle portion on the first substrate;

[0060] The projection of the electro-optic material layer on the first substrate does not overlap with the projection of the first tapered portion on the first substrate; the projection of the electro-optic material layer on the first substrate does not overlap with the projection of the second tapered portion on the first substrate.

[0061] In an alternative embodiment, the lower electrode includes a first electro-optic modulation portion, a first contact portion, and a first transition portion: the first transition portion is located between the first electro-optic modulation portion and the first contact portion; the projection of the first electro-optic modulation portion on the first substrate at least covers part of the projection of the second intermediate portion on the first substrate; the projection of the electro-optic material layer on the first substrate covers the projection of the first electro-optic modulation portion on the first substrate;

[0062] The upper electrode includes a second electro-optic modulation portion, a second contact portion, and a second transition portion: the second transition portion is located between the second electro-optic modulation portion and the second contact portion; the projection of the second electro-optic modulation portion on the first substrate at least partially overlaps with the projection of the first electro-optic modulation portion on the first substrate, and the overlapping projection at least covers part of the projection of the second intermediate portion on the first substrate.

[0063] For the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structures provided by the present invention, the projection of the second electro-optic modulation portion on the first substrate at least partially overlaps with the projection of the first electro-optic modulation portion on the first substrate, and the overlapping projection at least covers part of the projection of the second intermediate portion on the first substrate. The projection of the electro-optic material layer on the first substrate covers the projection of the first electro-optic modulation portion on the first substrate, so that the electric field provided by this electrode structure can always be parallel to the crystal orientation with a high electro-optic coefficient of the electro-optic material layer. The optical phase modulation efficiency does not decrease or even cancel due to the bending and folding of the waveguide core. Therefore, the waveguide core can be flexibly designed according to needs. The second intermediate portion of the second waveguide core can be set as one or a combination of a straight waveguide core, a bent waveguide core, and a spiral waveguide core according to requirements, which can improve the integration degree of the photonic integrated circuit.

[0064] In an alternative embodiment, the heterogeneous integrated electro-optic modulation device further includes:

[0065] A first metal plug, passing through the bonding dielectric layer and contacting and connecting with part of the first contact portion;

[0066] An upper cladding layer, located on the side surface of the second waveguide core facing away from the electro-optic material layer, and the upper cladding layer also covers the side surface of the second waveguide core and the side surface of the intermediate layer facing away from the bonding dielectric layer;

[0067] A second metal plug, passing through the upper cladding layer and the intermediate layer, and at least contacting and connecting with part of the first metal plug;

[0068] A lower electrode pad, located on the surface of the second metal plug exposed by the upper cladding layer; the lower electrode pad contacts and connects with the second metal plug; the lower electrode pad is connected to the first contact portion of the lower electrode through the first metal plug and the second metal plug. Brief Description of the Drawings

[0069] 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, without creative efforts, other drawings can also be obtained based on these drawings.

[0070] Figure 1 It is a schematic flowchart of a method for preparing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention.

[0071] Figure 2 It is a specific flowchart of a method for preparing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention.

[0072] Figure 3A It is a top view schematic diagram of the structure for forming the first waveguide core in a method for preparing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention.

[0073] Figure 3B It is in a method for preparing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention Figure 3A Cross-sectional view on the AA plane.

[0074] Figure 4 It is in a method for preparing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention Figure 3A Top view schematic diagram of the structure for forming the lower electrode groove and the lower electrode on this basis.

[0075] Figure 5A It is in a method for preparing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention Figure 4 Top view schematic diagram of the structure for forming the first metal plug on this basis.

[0076] Figure 5B It is in a method for preparing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention Figure 5A Cross-sectional view on the AA plane.

[0077] Figure 5C It is in a method for preparing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention Figure 5A Cross-sectional view on the BB plane.

[0078] Figure 6 It is in Example 1 of a method for preparing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present inventionFigure 5A Top view schematic diagram of the structure of the electro-optic material layer formed thereon.

[0079] Figure 7 Example 2 of the preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention, in Figure 5A Top view schematic diagram of the structure of the electro-optic material layer formed thereon.

[0080] Figure 8A Example 1 of the preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention, in Figure 6 Top view schematic diagram of the structure of the second waveguide core formed thereon.

[0081] Figure 8B The preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention Figure 8A Cross-sectional view on the AA plane.

[0082] Figure 9A Example 2 of the preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention, in Figure 7 Top view schematic diagram of the structure of the second waveguide core formed thereon.

[0083] Figure 9B The preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention Figure 9A Cross-sectional view on the AA plane.

[0084] Figure 10A Example 1 of the preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention, in Figure 8A Top view schematic diagram of the structure of the second metal plug formed thereon.

[0085] Figure 10B The preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention Figure 10A Cross-sectional view on the BB plane.

[0086] Figure 11A The preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention, in Figure 10A Top view schematic diagram of the structure of the upper electrode and the lower electrode pad formed thereon.

[0087] Figure 11B The preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to an embodiment of the present invention Figure 11A Cross-sectional view on the AA plane.

[0088] Reference numerals:

[0089] 10. First substrate; 21. Lower cladding; 22. Upper cladding; 30. First waveguide core; 400. Lower electrode groove; 40. Lower electrode; 401. First electro-optic modulation part; 402. First transition part; 403. First contact part; 41. First metal plug; 42. Second metal plug; 43. Lower electrode pad; 50. Bonding dielectric layer; 60. Electro-optic material layer; 70. Intermediate layer; 80. Second waveguide core; 90. Upper electrode; 901. Second electro-optic modulation part; 902. Second transition part; 903. Second contact part. Detailed implementation manners

[0090] The present invention will be further described in detail below with reference to the accompanying 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 convenience of description, only parts related to the present invention are shown in the drawings, rather than all the structures.

[0091] In the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention. Various structural schematic diagrams according to embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, and 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 only exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can 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.

[0092] The integrated photonics platform based on the stoichiometric silicon nitride waveguide core has advantages such as CMOS process compatibility and low propagation loss in a wide spectral range. Due to the weak electro-optic effect of the silicon nitride material, it is necessary to hetero-integrate a thin film material with a strong electro-optic effect, such as lithium niobate, so that the silicon nitride waveguide core and the thin film lithium niobate form a composite waveguide core, thereby realizing an efficient electro-optic modulation device on the silicon nitride photonics platform. Existing silicon nitride-lithium niobate electro-optic modulation devices are generally divided into horizontal electrode structure devices and upper and lower electrode structure devices.

[0093] For an electro-optic modulation device with a horizontal electrode structure, a composite waveguide core is formed by using X-cut thin-film lithium niobate and a silicon nitride waveguide core. The silicon nitride waveguide core is arranged along the Y direction of the thin-film lithium niobate, and the electrodes are located on both sides of the silicon nitride waveguide core to generate an electric field parallel to the Z direction of the lithium niobate. The disadvantages are as follows: 1) Due to the anisotropy of the electro-optic coefficient of lithium niobate, when the electrodes and the waveguide core are bent or folded simultaneously, the optical phase modulation efficiency will be reduced or the optical phase modulation before and after folding will cancel each other out. Therefore, the electro-optic modulation device is usually in a straight configuration; 2) In the device structure, the electrodes and the silicon nitride waveguide core are in the same horizontal position or the vertical distance is small. When the waveguide core approaches the electrodes, it will cause a high absorption loss, resulting in no waveguide core distribution in the area where the electrodes are located. Therefore, the design flexibility of the photonic integrated circuit of the heterogeneous integrated electro-optic modulation device with a horizontal electrode structure is limited and the integration degree is reduced.

[0094] For an electro-optic modulation device with an upper and lower electrode structure, a composite waveguide core is formed by using Z-cut thin-film lithium niobate and a silicon nitride waveguide core. The electrodes are located on the upper and lower sides of the silicon nitride-lithium niobate composite waveguide core to generate an electric field parallel to the Z direction of the lithium niobate, and the light of the TM mode propagates along the composite waveguide core. However, there are also certain defects: The metal electrode located under the silicon nitride waveguide core cannot withstand the high-temperature process during the deposition of the stoichiometric silicon nitride thin film, which causes difficulties in the fabrication of the device with this structure.

[0095] As Figure 1 shown, this embodiment provides a preparation method for a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure. The preparation method includes but is not limited to steps S101 to S107.

[0096] Step S101: Provide a first substrate 10 with a lower cladding 21 on its surface. On a part of the surface of the lower cladding 21 on the side facing away from the first substrate 10, form at least two first waveguide cores 30. Each first waveguide core 30 includes a first middle part with a first width and a first tapered part with a width gradually decreasing from the first width, as Figure 3A and Figure 3B shown.

[0097] Step S102: On a part of the surface of the lower cladding 21 on the side facing away from the first substrate 10, form a lower electrode groove 400, and form a lower electrode 40 in the lower electrode groove 400; the lower electrode groove 400 penetrates into a part of the thickness of the lower cladding 21; the thickness of the lower electrode 40 is less than or equal to the depth of the lower electrode groove 400; the projection of the lower electrode 40 on the first substrate 10 does not overlap with the projection of the first waveguide core 30 on the first substrate 10, as Figure 4 shown.

[0098] Step S103: A bonding dielectric layer 50 is formed on the surface of the lower cladding 21 facing away from the first substrate 10. The bonding dielectric layer 50 covers the lower electrode 40, the first waveguide core 30, and the lower cladding 21, as Figure 5A , 5B and Figure 5C shown.

[0099] Step S104: An electro-optic material layer 60 is bonded and formed on a partial surface of the bonding dielectric layer 50 facing away from the lower electrode 40; the projection of the electro-optic material layer 60 on the first substrate 10 covers a partial projection of the lower electrode 40 on the first substrate 10; the electro-optic material layer 60 includes an isotropic thickness region in the middle and a slope structure at the edge; the thickness of the slope structure gradually decreases along the direction away from the isotropic thickness region, as Figure 6 and Figure 7 shown.

[0100] Step S105: An intermediate layer 70 is formed on the surface of the electro-optic material layer 60 facing away from the bonding dielectric layer 50. The intermediate layer 70 covers the surface of the electro-optic material layer 60 facing away from the bonding dielectric layer 50 and the side surface of the electro-optic material layer 60.

[0101] Step S106: A second waveguide core 80 is formed on a partial surface of the intermediate layer 70 facing away from the lower electrode 40. The projection of the second waveguide core 80 on the first substrate 10 partially covers the projection of the first tapered portion of the first waveguide core 30 on the first substrate 10; the projection of the first waveguide core 30 on the first substrate 10 is located at both ends of the projection of the second waveguide core 80 on the first substrate 10; the projection of the electro-optic material layer 60 on the first substrate 10 at least partially covers the projection of the second waveguide core 80 on the first substrate 10, as Figure 8A and Figure 8B , and Figure 9A and Figure 9B shown.

[0102] Step S107: An upper electrode 90 is formed on the side of the second waveguide core 80 facing away from the electro-optic material layer 60, as Figure 11A and Figure 11B shown.

[0103] The manufacturing method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided by this embodiment first forms the first waveguide core, then forms the lower electrode and the electro-optic material layer, and finally forms the second waveguide core and the lower electrode. It can make the light propagated by the first waveguide core (such as stoichiometric silicon nitride) be coupled to the second waveguide core (such as non-stoichiometric silicon nitride waveguide core) through interlayer coupling, and then transition to the second waveguide core - electro-optic material layer composite waveguide core through the slope structure of the electro-optic material layer, or make the light propagated by the first waveguide core transition to the first waveguide core - electro-optic material layer composite waveguide core with low loss through the slope structure of the electro-optic material layer, and then be coupled to the second waveguide core - electro-optic material layer composite waveguide core through interlayer coupling. On the one hand, by setting the upper electrode and the lower electrode at the corresponding position of the second waveguide core to form a heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure, the defect that the electrode and the waveguide core are linearly arranged in the horizontal electrode structure device can be solved, so that the waveguide core and the electrode in the device can be bent and folded as needed, improving the integration degree of the optical device and the flexibility of the optical device design. On the other hand, the lower electrode is formed after the first waveguide core, and there is no overlap between the projection of the lower electrode on the first substrate and the projection of the first waveguide core on the first substrate, which can solve the problem that it is not easy to fabricate the lower electrode when forming a heterogeneous integrated electro-optic modulation device with the upper and lower electrode configuration on the stoichiometric silicon nitride photonics platform, making the fabrication of the lower electrode not affected by the preparation process of the first waveguide core, reducing the fabrication difficulty of the lower electrode, and improving the process efficiency and process yield. Therefore, the manufacturing method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided by this embodiment can improve the integration degree of the optical device and the flexibility of the optical device design, reduce the fabrication difficulty of the lower electrode, and improve the process efficiency and process yield. In addition, the slope structure of the electro-optic material layer can provide a low-loss optical transition between the waveguide core and / or the composite waveguide core, without requiring the refractive index of the second waveguide core to be higher than that of the electro-optic material layer, relaxing the restriction on the material of the second waveguide core. For example, it can avoid using rich-silicon nitride with a refractive index higher than that of the electro-optic material layer but higher absorption loss for the second waveguide core.

[0104] In some alternative embodiments, in the step of forming the second waveguide core 80, the second waveguide core 80 includes a second middle part with a second width and two second tapered parts with widths gradually decreasing from the second width; the projections of the second tapered parts at both ends of the second waveguide core 80 on the first substrate 10 respectively overlap partially with the projection of one first tapered part on the first substrate 10, and the tapered directions of the overlapping first tapered part and the second tapered part are inverted;

[0105] The projection of the equal-thickness region of the electro-optic material layer 60 on the first substrate 10 at least partially covers the projection of the second intermediate portion on the first substrate 10; the projection of the slope structure of the electro-optic material layer 60 on the first substrate 10 covers a partial projection of the first waveguide core 30 on the first substrate 10 or a partial projection of the second waveguide core 80 on the first substrate 10.

[0106] The preparation method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structures provided in this embodiment forms a second waveguide core-electro-optic material layer composite waveguide core through the second waveguide core and the electro-optic material layer, and the first tapered portion and the second tapered portion can provide optical field coupling transition between the second waveguide core and the first waveguide core, or between the second waveguide core-electro-optic material layer composite waveguide core and the first waveguide core-electro-optic material layer composite waveguide core, so that the optical signal propagated by the first waveguide core enters the second waveguide core-electro-optic material layer composite waveguide core through the first tapered portion, the second tapered portion and the electro-optic material layer for electro-optic modulation, and then returns to the first waveguide core through the second tapered portion, the first tapered portion and the electro-optic material layer, which can reduce the loss in the optical signal transmission process and solve the problem of difficult fabrication of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structures on the silicon nitride photonics platform. In the transition part between the first waveguide core and the second waveguide core, or between the first waveguide core-electro-optic material layer composite waveguide core and the second waveguide core-electro-optic material layer composite waveguide core, by setting the first tapered portion and the second tapered portion to be inverted and partially overlapped, the optical field transition loss can be reduced.

[0107] In some alternative embodiments, the projection of the equal-thickness region of the electro-optic material layer 60 on the first substrate 10 completely covers the projection of the second intermediate portion on the first substrate 10, the projection of the second tapered portion on the first substrate 10, and the projection of the first tapered portion on the first substrate 10;

[0108] The projection of the slope structure of the electro-optic material layer 60 on the first substrate 10 covers a partial projection of the first intermediate portion on the first substrate 10.

[0109] The preparation method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structures provided by this embodiment is such that the projection of the equal-thickness region of the electro-optic material layer on the first substrate completely covers the projection of the second middle part on the first substrate, the projection of the second tapered part on the first substrate, and the projection of the first tapered part on the first substrate; the projection of the slope structure of the electro-optic material layer on the first substrate covers a partial projection of the first middle part on the first substrate, and a first waveguide core - electro-optic material layer composite waveguide core and a second waveguide core - electro-optic material layer composite waveguide core can be formed simultaneously. In the electro-optic modulation device, the optical signal first passes through the slope structure of the electro-optic material layer, transitions from the first waveguide core to the first waveguide core - electro-optic material layer composite waveguide core, and then passes through the first tapered part and the second tapered part, transitioning from the first waveguide core - electro-optic material layer composite waveguide core to the second waveguide core - electro-optic material layer composite waveguide core; after the optical signal in the second waveguide core - electro-optic material layer composite waveguide core is electro-optically modulated, it passes through the second tapered part and the first tapered part again, transitioning from the second waveguide core - electro-optic material layer composite waveguide core to the first waveguide core - electro-optic material layer composite waveguide core, and then passes through the slope structure of the electro-optic material layer, transitioning from the first waveguide core - electro-optic material layer composite waveguide core to the first waveguide core. Therefore, the formed electro-optic modulation device can reduce the loss during the optical signal transmission process and improve the optical field transition efficiency. In addition, since only the optical transition between two structures is involved in each step of the optical field transition, there are fewer variables, the optimization design is relatively simple, and a higher transition efficiency can be achieved.

[0110] In some alternative embodiments, the projection of the electro-optic material layer 60 on the first substrate 10 partially covers the projection of the second middle part on the first substrate 10;

[0111] The projection of the electro-optic material layer 60 on the first substrate 10 does not overlap with the projection of the first tapered part on the first substrate 10; the projection of the electro-optic material layer 60 on the first substrate 10 does not overlap with the projection of the second tapered part on the first substrate 10.

[0112] The manufacturing method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided in this embodiment is such that the projection of the electro-optic material layer on the first substrate partially covers the projection of the second middle part on the first substrate; the projection of the electro-optic material layer on the first substrate does not overlap with the projection of the first tapered part on the first substrate; the projection of the electro-optic material layer on the first substrate does not overlap with the projection of the second tapered part on the first substrate, and the overlapping part of the second waveguide core and the electro-optic material layer can form a second waveguide core - electro-optic material layer composite waveguide core. In the electro-optic modulation device, the optical signal first passes through the first tapered part and the second tapered part, transitions from the first waveguide core to the second waveguide core, and then passes through the slope structure of the electro-optic material layer to transition from the second waveguide core to the second waveguide core - electro-optic material layer composite waveguide core; after the optical signal in the second waveguide core - electro-optic material layer composite waveguide core is electro-optically modulated, it passes through the slope structure of the electro-optic material layer, transitions from the second waveguide core - electro-optic material layer composite waveguide core to the second waveguide core, and then passes through the second tapered part and the first tapered part to transition from the second waveguide core to the first waveguide core. Therefore, the formed electro-optic modulation device can reduce the loss during the optical signal transmission process and improve the optical field transition efficiency. In addition, since only the optical transition between two structures is involved in each step of the optical field passing, there are fewer variables, and the optimization design is relatively simple, and a higher transition efficiency can be achieved.

[0113] In some alternative embodiments, in the step of forming the lower electrode 40, the lower electrode 40 includes a first electro-optic modulation part 401, a first contact part 403, and a first transition part 402; the first transition part 402 is located between the first electro-optic modulation part 401 and the first contact part 403, as Figure 4 shown;

[0114] In the step of forming the electro-optic material layer 60, the projection of the electro-optic material layer 60 on the first substrate 10 covers the projection of the first electro-optic modulation part on the first substrate 10;

[0115] In the step of forming the upper electrode 90, the upper electrode 90 includes a second electro-optic modulation part 901, a second contact part 903, and a second transition part 902; the second transition part 902 is located between the second electro-optic modulation part 901 and the second contact part 903; the projection of the second electro-optic modulation part 901 on the first substrate 10 at least partially overlaps with the projection of the first electro-optic modulation part 401 on the first substrate 10, and the overlapping projection at least covers a part of the projection of the second middle part on the first substrate 10, as Figure 11A and Figure 11B shown.

[0116] Specifically, when implemented, the projection of one of the second electro-optic modulation part 901 and the first electro-optic modulation part 401 on the first substrate 10 covers the projection of the other on the first substrate 10. In one example, as Figure 11AAs shown, the projection of the first electro-optic modulation part 401 on the first substrate 10 completely covers the projection of the second electro-optic modulation part 901 on the first substrate 10. In other examples, the projection of the second electro-optic modulation part 901 on the first substrate 10 completely overlaps with the projection of the first electro-optic modulation part 401 on the first substrate 10.

[0117] In some alternative embodiments, the projections of the second tapered portions at both ends of the second waveguide core 80 on the first substrate 10 are respectively centered and aligned with the projections of the first tapered portions of a first waveguide core 30 on the first substrate 10;

[0118] The second intermediate portion of the second waveguide core 80 is one or a combination of a straight waveguide core, a bent waveguide core, and a spiral waveguide core; the projection of the lower electrode 40 on the first substrate 10 at least covers a part of the projection of the second intermediate portion on the first substrate 10.

[0119] In the manufacturing method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided in this embodiment, the projection of the second electro-optic modulation part on the first substrate at least partially overlaps with the projection of the first electro-optic modulation part on the first substrate, and the overlapping projection at least covers a part of the projection of the second intermediate portion on the first substrate. The projection of the electro-optic material layer on the first substrate covers the projection of the first electro-optic modulation part on the first substrate, so that the electric field provided by this electrode structure can always be parallel to the crystal orientation with a high electro-optic coefficient of the electro-optic material layer, and the optical phase modulation efficiency does not decrease or even cancel due to the bending and folding of the waveguide core. Therefore, the waveguide core can be flexibly designed according to needs, and the second intermediate portion of the second waveguide core can be set as one or a combination of a straight waveguide core, a bent waveguide core, and a spiral waveguide core according to requirements, which can improve the integration degree of the photonic integrated circuit.

[0120] In some alternative embodiments, after the step of forming the bonding dielectric layer 50, it includes:

[0121] Form a first via hole on the side of the bonding dielectric layer 50 facing away from the first contact portion. The first via hole penetrates through the bonding dielectric layer 50 and exposes a part of the first contact portion;

[0122] Fill the first via hole to form a first metal plug 41.

[0123] In some alternative embodiments, the step of forming the upper electrode 90 on the side of the second waveguide core 80 facing away from the electro-optic material layer 60 includes:

[0124] Form an upper cladding layer 22 on the side surface of the second waveguide core 80 facing away from the electro-optic material layer 60. The upper cladding layer 22 also covers the side surface of the second waveguide core 80 and the side surface of the intermediate layer 70 facing away from the bonding dielectric layer 50;

[0125] A second via hole is formed on a surface of the upper cladding layer 22 facing away from the first metal plug 41. The second via hole penetrates through the upper cladding layer 22 and the intermediate layer 70 and exposes at least a part of the first metal plug 41.

[0126] The second via hole is filled to form a second metal plug 42. The second metal plug 42 is connected to a first contact portion of the lower electrode 40 through the first metal plug 41.

[0127] An upper electrode 90 is formed on a side of the electro-optic material layer 60 facing away from the intermediate layer 70, and a lower electrode pad 43 is formed on a side of the upper cladding layer 22 facing away from the second metal plug 42. The lower electrode pad 43 is in contact with and connected to the second metal plug 42. The lower electrode pad 43 is connected to the first contact portion of the lower electrode 40 through the first metal plug 41 and the second metal plug 42.

[0128] In some other alternative embodiments, the first metal plug 41 may be formed after the step of forming the intermediate layer 70 and before the step of forming the second waveguide core 80.

[0129] After the step of forming the intermediate layer 70 includes:

[0130] A first via hole is formed on a side of the intermediate layer 70 facing away from the first contact portion. The first via hole penetrates through the intermediate layer 70 and the bonding dielectric layer 50 and exposes a part of the first contact portion.

[0131] The first via hole is filled to form the first metal plug 41.

[0132] The step of forming the upper electrode 90 includes:

[0133] An upper cladding layer 22 is formed on a surface of the second waveguide core 80 facing away from the electro-optic material layer 60. The upper cladding layer 22 also covers the side surface of the second waveguide core 80 and a surface of the intermediate layer 70 facing away from the bonding dielectric layer 50.

[0134] A second via hole is formed on a surface of the upper cladding layer 22 facing away from the first metal plug 41. The second via hole penetrates through the upper cladding layer 22 and exposes at least a part of the first metal plug 41.

[0135] The second via hole is filled to form a second metal plug 42. The second metal plug 42 is connected to a first contact portion of the lower electrode 40 through the first metal plug 41.

[0136] An upper electrode 90 is formed on a side of the electro-optic material layer 60 facing away from the intermediate layer 70, and a lower electrode pad 43 is formed on a side of the upper cladding layer 22 facing away from the second metal plug 42. The lower electrode pad 43 is in contact with and connected to the second metal plug 42. The lower electrode pad 43 is connected to the first contact portion of the lower electrode 40 through the first metal plug 41 and the second metal plug 42.

[0137] In some alternative embodiments, the material of the first waveguide core 30 is stoichiometric silicon nitride, silicon, a silicon nitride / silicon dioxide stack, or a silicon / silicon dioxide stack.

[0138] In some alternative embodiments, the process for forming the first waveguide core 30 is the LPCVD process; the material of the first waveguide core 30 is stoichiometric silicon nitride or a silicon nitride / silicon dioxide stack;

[0139] The process for forming the second waveguide core 80 is the PECVD process; the material of the second waveguide core 80 is silicon or silicon nitride.

[0140] In some alternative embodiments, the material of the second waveguide core 80 is non-stoichiometric silicon nitride.

[0141] In some alternative embodiments, the steps of forming the first waveguide core 30 include:

[0142] Forming a first waveguide core layer on the surface of the lower cladding 21 facing away from the first substrate 10 by the LPCVD process;

[0143] Performing a patterning process on the first waveguide core layer to form at least two first waveguide cores 30; the material of the first waveguide core 30 is stoichiometric silicon nitride;

[0144] The steps of forming the second waveguide core 80 include:

[0145] Forming a second waveguide core layer on the surface of the intermediate layer 70 facing away from the lower electrode 40 by the PECVD process;

[0146] Performing a patterning process on the second waveguide core layer to form the second waveguide core 80.

[0147] For the method of manufacturing a heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided in this embodiment, first, stoichiometric silicon nitride is formed as the first waveguide core through the LPCVD process with a relatively high temperature. Then, after forming the lower electrode, the second waveguide core is formed through the PECVD process with a relatively low temperature. This enables the fabrication of the lower electrode without undergoing a high-temperature process, avoiding the influence of the high-temperature process of the first waveguide core on the lower electrode, reducing the fabrication difficulty of the lower electrode, improving the process efficiency and process yield, and thus solving the problem of the difficulty in fabricating the lower electrode when forming a heterogeneous integrated electro-optic modulation device with an upper and lower electrode configuration on a stoichiometric silicon nitride photonics platform.

[0148] In some alternative embodiments, the thickness of the lower cladding 21 is 3 μm to 20 μm;

[0149] The thickness of the bonding dielectric layer 50 above the first waveguide core 30 is 10 nm to 1000 nm;

[0150] The thickness of the bonding dielectric layer 50 located above the lower electrode 40 is 2 μm to 5 μm;

[0151] The material of the electro-optic material layer 60 is lithium niobate, lithium tantalate, barium titanate, etc.;

[0152] The thickness of the electro-optic material layer 60 is 100 nm to 500 nm;

[0153] The ratio of the horizontal length of the slope structure of the electro-optic material layer 60 to the thickness of the equal-thickness part is 10:1 to 500:1;

[0154] The thickness of the intermediate layer 70 located above the electro-optic material layer 60 is 10 nm to 300 nm;

[0155] The thickness of the upper cladding 22 located above the second waveguide core 80 is 2 μm to 5 μm.

[0156] As Figure 2 shown, the present invention also provides a schematic flow chart of a preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure, including but not limited to steps S201 to S212.

[0157] Step S201: Provide a first substrate 10, and form a lower cladding 21 on one side surface of the first substrate 10.

[0158] Specifically, the material of the first substrate 10 can be silicon, etc.; the material of the lower cladding 21 can be silicon dioxide, etc., and the thickness of the lower cladding 21 is 3 μm to 20 μm.

[0159] Step S202: Form at least two first waveguide cores 30 on a partial surface of the lower cladding 21 on the side facing away from the first substrate 10. Each first waveguide core 30 includes a first intermediate part having a first width and a first tapered part with a width gradually decreasing from the first width, as Figure 3A and Figure 3B shown.

[0160] In some embodiments, two first waveguide cores 30 are formed, and the first tapered parts of the two first waveguide cores 30 are arranged oppositely.

[0161] Specifically, first, a first waveguide core layer is formed on the surface of the lower cladding 21 on the side facing away from the first substrate 10 by LPCVD process; then, a patterning process is performed on the first waveguide core layer to form at least two first waveguide cores 30. The material of the first waveguide core 30 can be a single layer of silicon nitride, silicon, etc. or a stacked layer composed of silicon dioxide.

[0162] Step S203: Form a lower electrode groove 400 on a partial surface of the lower cladding 21 on the side facing away from the first substrate 10; the lower electrode groove 400 penetrates into a part of the thickness of the lower cladding 21.

[0163] In some embodiments, the lower electrode groove 400 is formed on the surface of the lower cladding 21 between the two first waveguide cores 30. The projection of the lower electrode groove 400 on the first substrate 10 does not overlap with the projections of the two first waveguide cores 30 on the first substrate 10.

[0164] Step S204: Form the lower electrode 40 in the lower electrode groove 400; the thickness of the lower electrode 40 is less than or equal to the depth of the lower electrode groove 400; the projection of the lower electrode 40 on the first substrate 10 does not overlap with the projection of the first waveguide core 30 on the first substrate 10; the lower electrode 40 includes a first electro-optic modulation portion, a first contact portion, and a first transition portion; the first transition portion is located between the first electro-optic modulation portion and the first contact portion, as Figure 4 shown.

[0165] Specifically, the material of the lower electrode 40 can be Al, Cu, etc. In some embodiments, the projection of the first electro-optic modulation portion on the first substrate 10 is located between the projections of two adjacent first waveguide cores 30 on the first substrate 10.

[0166] Step S205: Form a bonding dielectric layer 50 on the surface of the lower cladding 21 facing away from the first substrate 10, and the bonding dielectric layer 50 covers the lower electrode 40, the first waveguide core 30, and the lower cladding 21.

[0167] Specifically, after forming the bonding dielectric layer 50, a flat surface can also be formed by the CMP process. The material of the bonding dielectric layer 50 can be silicon dioxide, aluminum oxide, etc. or a combination thereof; the thickness of the bonding dielectric layer 50 above the first waveguide core 30 is 10 nm to 1000 nm; the thickness of the bonding dielectric layer 50 above the lower electrode 40 is 2 μm to 5 μm.

[0168] Step S206: Form a first via hole on the side of the bonding dielectric layer 50 facing away from the first contact portion, and the first via hole penetrates through the bonding dielectric layer 50 and exposes part of the first contact portion; fill the first via hole to form a first metal plug 41, as Figure 5A , Figure 5B and Figure 5C shown.

[0169] Specifically, the first metal plug 41 is filled with metal in the first via hole by the damascene process; the material of the first metal plug 41 can be W, Cu, etc. Figure 5A is the top view of the structure after forming the first metal plug 41, Figure 5B is Figure 5A the cross-sectional view on the AA plane, Figure 5C is Figure 5A the cross-sectional view on the BB plane.

[0170] Step S207: On a partial surface of the bonding dielectric layer 50 facing away from the lower electrode 40, an electro-optic material layer 60 is bonded and formed; the electro-optic material layer 60 includes an isometric-thickness region in the middle and a slope structure at the edge; the thickness of the slope structure gradually decreases along the direction away from the isometric-thickness region; the projection of the electro-optic material layer 60 on the first substrate 10 covers the projection of the first electro-optic modulation part on the first substrate 10, as Figure 6 and Figure 7 shown.

[0171] In specific implementation, the projection of the electro-optic material layer 60 on the first substrate 10 may cover the projection of the first tapered portion of the first waveguide core 30 on the first substrate 10, or may not cover the projection of the first waveguide core 30 on the first substrate 10, as Figure 6 and Figure 7 shown. The slope structure is located at both side edges of the electro-optic material layer 60 close to the first waveguide core 30. The electro-optic material layer 60 may be a thin film material with electro-optic effect such as lithium niobate, barium titanate, lithium tantalate, etc. The thickness of the electro-optic material layer 60 is 100 nm to 500 nm, and the ratio of the horizontal length of the slope structure of the electro-optic material layer 60 to the thickness of the isometric-thickness portion is 10:1 to 500:1.

[0172] Step S208: On a surface of the electro-optic material layer 60 facing away from the bonding dielectric layer 50, an intermediate layer 70 is formed, and the intermediate layer 70 covers the surface of the electro-optic material layer 60 facing away from the bonding dielectric layer 50 and the side surface of the electro-optic material layer 60.

[0173] In specific implementation, the material of the intermediate layer 70 is silicon dioxide; after forming the intermediate layer 70, the surface of the intermediate layer 70 can also be flattened by a CMP process, and the thickness of the intermediate layer 70 above the electro-optic material layer 60 is 10 nm to 300 nm.

[0174] Step S209: On a partial surface of the intermediate layer 70 facing away from the lower electrode 40, a second waveguide core 80 is formed. The projection of the second waveguide core 80 on the first substrate 10 partially covers the projection of the first tapered portion of the first waveguide core 30 on the first substrate 10; the projection of the first waveguide core 30 on the first substrate 10 is located at both ends of the projection of the second waveguide core 80 on the first substrate 10; the projection of the electro-optic material layer 60 on the first substrate 10 at least partially covers the projection of the second waveguide core 80 on the first substrate 10;

[0175] In some embodiments, the second waveguide core 80 includes a second middle portion having a second width and two second tapered portions with widths gradually decreasing from the second width; the projections of the second tapered portions at both ends of the second waveguide core 80 on the first substrate 10 respectively overlap partially with the projections of one first tapered portion on the first substrate 10, and the tapered directions of the overlapping first tapered portion and second tapered portion are inverted; the projection of the equal-thickness region of the electro-optic material layer 60 on the first substrate 10 at least partially covers the projection of the second middle portion on the first substrate 10; the projection of the slope structure of the electro-optic material layer 60 on the first substrate 10 covers a partial projection of the first waveguide core 30 on the first substrate 10 or a partial projection of the second waveguide core 80 on the first substrate 10. The material of the second waveguide core 80 is silicon or silicon nitride.

[0176] In Example 1, as Figure 8A and Figure 8B shown, the projection of the equal-thickness region of the electro-optic material layer 60 on the first substrate 10 completely covers the projection of the second middle portion on the first substrate 10, the projection of the second tapered portion on the first substrate 10, and the projection of the first tapered portion on the first substrate 10; the projection of the slope structure of the electro-optic material layer 60 on the first substrate 10 covers a partial projection of the first middle portion on the first substrate 10. Figure 8A FIG. is a top view of the structure after forming the second waveguide core 80 in Example 1, Figure 8B For Figure 8A is a cross-sectional view taken along the AA plane.

[0177] In Example 2, as Figure 9A and Figure 9B shown, the projection of the electro-optic material layer 60 on the first substrate 10 partially covers the projection of the second middle portion on the first substrate 10; the projection of the electro-optic material layer 60 on the first substrate 10 does not overlap with the projection of the first tapered portion on the first substrate 10; the projection of the electro-optic material layer 60 on the first substrate 10 does not overlap with the projection of the second tapered portion on the first substrate 10, Figure 9A FIG. is a top view of the structure after forming the second waveguide core 80 in Example 2, Figure 9B For Figure 9A is a cross-sectional view taken along the AA plane.

[0178] Step S210, form an upper cladding 22 on the surface of the second waveguide core 80 facing away from the electro-optic material layer 60, and the upper cladding 22 also covers the side surface of the second waveguide core 80 and the surface of the intermediate layer 70 facing away from the bonding dielectric layer 50.

[0179] Specifically, after forming the upper cladding 22, a flat surface can also be formed by a CMP process. The material of the upper cladding 22 is silicon dioxide; the thickness of the upper cladding 22 located above the second waveguide core 80 is 2 μm to 5 μm.

[0180] Step S211: Form a second via hole on the surface of the upper cladding 22 on the side facing away from the first metal plug 41. The second via hole penetrates through the upper cladding 22 and the intermediate layer 70 and exposes at least a part of the first metal plug 41; fill the second via hole to form a second metal plug 42; the second metal plug 42 is connected to the first contact portion of the lower electrode 40 through the first metal plug 41, as Figure 10A and Figure 10B shown.

[0181] Specifically, in implementation, a metal is filled in the second via hole through a damascene process to form the second metal plug 42; the material of the second metal plug 42 can be W, Cu, etc. Figure 10A Fig. is a top view of the structure after the second metal plug 42 is formed, Figure 10B and Figure 10A Fig. is a cross-sectional view taken along the BB plane.

[0182] Step S212: Form an upper electrode 90 on the side of the electro-optic material layer 60 facing away from the intermediate layer 70, and form a lower electrode pad 43 on the side of the upper cladding 22 facing away from the second metal plug 42; the lower electrode pad 43 is in contact with and connected to the second metal plug 42; the lower electrode pad 43 is connected to the first contact portion of the lower electrode 40 through the first metal plug 41 and the second metal plug 42; the projection of the upper electrode 90 on the first substrate 10 covers the projection of the first electro-optic modulation portion on the first substrate 10, as Figure 11A and Figure 11B shown.

[0183] In some embodiments, the upper electrode 90 includes a second electro-optic modulation portion 901, a second contact portion 903, and a second transition portion 902; the second transition portion 902 is located between the second electro-optic modulation portion 901 and the second contact portion 903; the projection of the second electro-optic modulation portion 901 on the first substrate 10 overlaps at least partially with the projection of the first electro-optic modulation portion 401 on the first substrate 10, and the overlapping projection covers at least a part of the projection of the second intermediate portion on the first substrate 10; the projection of the first electro-optic modulation portion 401 on the first substrate 10 covers at least a part of the projection of the second intermediate portion on the first substrate 10. Figure 11A Fig. is a top view of the structure after the upper electrode 90 and the lower electrode pad 43 are formed, Figure 11B and Figure 11A Fig. is a cross-sectional view taken along the AA plane. In Figure 11A , at least a part of the second intermediate portion of the second waveguide core 80 is located within the overlapping portion of the first electro-optic modulation portion 401 and the second electro-optic modulation portion 901.

[0184] Specifically, in implementation, first form a metal layer covering the surfaces of the upper cladding 22 and the second metal plug 42, and then perform a patterning process on the metal layer to form the upper electrode 90 and the lower electrode pad 43 connected to the second metal plug 42.

[0185] This embodiment also provides a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure, such as Figure 11A and Figure 11B shown. The heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure includes:

[0186] A first substrate 10;

[0187] A lower cladding layer 21, located on one side surface of the first substrate 10;

[0188] At least two first waveguide cores 30, located on a partial surface of the lower cladding layer 21 on the side facing away from the first substrate 10. Each first waveguide core 30 includes a first intermediate portion with a first width and a first tapered portion with a width gradually decreasing from the first width;

[0189] A lower electrode groove 400, located on the side of the lower cladding layer 21 facing away from the first substrate 10, and the lower electrode groove 400 penetrates into the lower cladding layer 21 with a partial thickness;

[0190] A lower electrode 40, located in the lower electrode groove 400; the thickness of the lower electrode 40 is less than or equal to the depth of the lower electrode groove 400; the projection of the lower electrode 40 on the first substrate 10 does not overlap with the projection of the first waveguide core 30 on the first substrate 10;

[0191] A bonding dielectric layer 50, located on the side surface of the lower cladding layer 21 facing away from the first substrate 10, and the bonding dielectric layer 50 covers the lower electrode 40, the first waveguide core 30, and the lower cladding layer 21;

[0192] An electro-optic material layer 60, located on a partial surface of the bonding dielectric layer 50 on the side facing away from the lower electrode 40; the projection on the first substrate 10 covers a partial projection of the lower electrode 40 on the first substrate 10; the electro-optic material layer 60 includes an equal-thickness region in the middle and a slope structure at the edge; the thickness of the slope structure gradually decreases along the direction away from the equal-thickness region;

[0193] An intermediate layer 70, located on the side surface of the electro-optic material layer 60 facing away from the bonding dielectric layer 50, and the intermediate layer 70 covers the side surface of the electro-optic material layer 60 facing away from the bonding dielectric layer 50 and the side surface of the electro-optic material layer 60;

[0194] A second waveguide core 80, located on a partial surface of the intermediate layer 70 on the side facing away from the lower electrode 40; the projection of the second waveguide core 80 on the first substrate 10 partially covers the projection of the first tapered portion of the first waveguide core 30 on the first substrate 10; the projection of the first waveguide core 30 on the first substrate 10 is located at both ends of the projection of the second waveguide core 80 on the first substrate 10; the projection of the electro-optic material layer 60 on the first substrate 10 at least partially covers the projection of the second waveguide core 80 on the first substrate 10;

[0195] The upper electrode 90 is located on the side of the second waveguide core 80 facing away from the electro-optic material layer 60.

[0196] The heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure provided in this embodiment is prepared by the preparation method of the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure. An upper electrode and a lower electrode are arranged at corresponding positions of the second waveguide core to form a heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure, which can solve the defect that the electrodes and the waveguide core in the horizontal electrode structure device are linearly arranged, so that the waveguide core and the electrodes in the device can be bent and folded as needed, improving the integration of optical devices and the flexibility of the design of optical devices.

[0197] In some optional embodiments, the second waveguide core 80 includes a second middle part with a second width and two second tapered parts with widths gradually decreasing from the second width;

[0198] The projections of the second tapered parts at both ends of the second waveguide core 80 on the first substrate 10 respectively overlap with the projections of one first tapered part on the first substrate 10, and the tapered directions of the overlapping first tapered part and the second tapered part are inverted;

[0199] The projection of the equal-thickness region of the electro-optic material layer 60 on the first substrate 10 at least partially covers the projection of the second middle part on the first substrate 10; the projection of the slope structure of the electro-optic material layer 60 on the first substrate 10 covers a part of the projection of the first waveguide core 30 on the first substrate 10 or a part of the projection of the second waveguide core 80 on the first substrate 10.

[0200] In some optional embodiments, the projection of the equal-thickness region of the electro-optic material layer 60 on the first substrate 10 completely covers the projection of the second middle part on the first substrate 10, the projection of the second tapered part on the first substrate 10, and the projection of the first tapered part on the first substrate 10;

[0201] The projection of the slope structure of the electro-optic material layer 60 on the first substrate 10 covers a part of the projection of the first middle part on the first substrate 10.

[0202] In some optional embodiments, the projection of the electro-optic material layer 60 on the first substrate 10 partially covers the projection of the second middle part on the first substrate 10;

[0203] The projection of the electro-optic material layer 60 on the first substrate 10 does not overlap with the projection of the first tapered part on the first substrate 10; the projection of the electro-optic material layer 60 on the first substrate 10 does not overlap with the projection of the second tapered part on the first substrate 10.

[0204] In some alternative embodiments, the lower electrode 40 includes a first electro-optic modulation portion, a first contact portion, and a first transition portion: the first transition portion is located between the first electro-optic modulation portion and the first contact portion; the projection of the first electro-optic modulation portion on the first substrate 10 at least covers the projection of at least part of the second intermediate portion on the first substrate 10; the projection of the electro-optic material layer 60 on the first substrate 10 covers the projection of the first electro-optic modulation portion on the first substrate 10;

[0205] The upper electrode 90 includes a second electro-optic modulation portion 901, a second contact portion 903, and a second transition portion 902: the second transition portion 902 is located between the second electro-optic modulation portion 901 and the second contact portion 903; the projection of the second electro-optic modulation portion 901 on the first substrate 10 at least partially overlaps with the projection of the first electro-optic modulation portion 401 on the first substrate 10, and the overlapping projection at least covers the projection of at least part of the second intermediate portion on the first substrate 10.

[0206] For the heterogeneous integrated electro-optic modulation device with the upper and lower electrode structures provided in this embodiment, the projection of the second electro-optic modulation portion on the first substrate at least partially overlaps with the projection of the first electro-optic modulation portion on the first substrate, and the overlapping projection at least covers the projection of at least part of the second intermediate portion on the first substrate. The projection of the electro-optic material layer on the first substrate covers the projection of the first electro-optic modulation portion on the first substrate, so that the electric field provided by this electrode structure can always be parallel to the crystal orientation with a high electro-optic coefficient of the electro-optic material layer. The light phase modulation efficiency does not decrease or even cancel due to the bending and folding of the waveguide core. Therefore, the waveguide core can be flexibly designed according to needs, and the second intermediate portion of the second waveguide core can be set as one or a combination of a straight waveguide core, a bent waveguide core, and a spiral waveguide core according to requirements, which can improve the integration degree of the photonic integrated circuit.

[0207] In some alternative embodiments, the heterogeneous integrated electro-optic modulation device further includes:

[0208] A first metal plug 41, passing through the bonding dielectric layer 50 and contacting and connecting with part of the first contact portion;

[0209] An upper cladding layer 22, located on the surface of the second waveguide core 80 facing away from the electro-optic material layer 60. The upper cladding layer 22 also covers the side surface of the second waveguide core 80 and the surface of the intermediate layer 70 facing away from the bonding dielectric layer 50;

[0210] A second metal plug 42, passing through the upper cladding layer 22 and the intermediate layer 70, and at least contacting and connecting with part of the first metal plug 41;

[0211] A lower electrode pad 43, located on the surface of the exposed second metal plug 42 of the upper cladding layer 22; the lower electrode pad 43 contacts and connects with the second metal plug 42; the lower electrode pad 43 is connected to the first contact portion of the lower electrode 40 through the first metal plug 41 and the second metal plug 42.

[0212] In some alternative embodiments, the material of the first waveguide core 30 is stoichiometric silicon nitride, silicon, a silicon nitride / silicon dioxide stack, or a silicon / silicon dioxide stack.

[0213] In some alternative embodiments, the first waveguide core 30 is adapted to be formed by an LPCVD process; the material of the first waveguide core 30 is stoichiometric silicon nitride or a silicon nitride / silicon dioxide stack;

[0214] The second waveguide core 80 is adapted to be formed by a PECVD process; the material of the second waveguide core 80 is silicon or silicon nitride;

[0215] The thickness of the lower cladding 21 is 3 μm to 20 μm;

[0216] The thickness of the bonding dielectric layer 50 above the first waveguide core 30 is 10 nm to 1000 nm;

[0217] The thickness of the bonding dielectric layer 50 above the lower electrode 40 is 2 μm to 5 μm;

[0218] The material of the electro-optic material layer is lithium niobate, lithium tantalate, barium titanate, etc.;

[0219] The thickness of the electro-optic material layer 60 is 100 nm to 500 nm;

[0220] The ratio of the horizontal length of the sloped surface structure of the electro-optic material layer 60 to the thickness of the equal-thickness portion is 10:1 to 500:1;

[0221] The thickness of the intermediate layer 70 above the electro-optic material layer 60 is 10 nm to 300 nm;

[0222] The thickness of the upper cladding 22 above the second waveguide core 80 is 2 μm to 5 μm.

[0223] In the description of this specification, the descriptions referring to terms such as "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 expressions 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" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0224] In the above description, no detailed description is made of 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 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.

[0225] 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, and the protection scope of the present invention is determined by the scope of the appended claims.

Claims

1. A preparation method of a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure, characterized in that, Comprising: providing a first substrate with a surface-covered undercladding, forming at least two first waveguide cores on a partial surface of the undercladding on a side facing away from the first substrate, each of the first waveguide cores including a first intermediate portion having a first width and a first tapered portion with a width gradually decreasing from the first width; forming a lower electrode groove on a partial surface of the undercladding on a side facing away from the first substrate, and forming a lower electrode in the lower electrode groove; the lower electrode groove penetrates into a partial thickness of the undercladding; the thickness of the lower electrode is less than or equal to the depth of the lower electrode groove; the projection of the lower electrode on the first substrate does not overlap with the projection of the first waveguide core on the first substrate; forming a bonding dielectric layer on a surface of the undercladding on a side facing away from the first substrate, the bonding dielectric layer covering the lower electrode, the first waveguide core, and the undercladding; bonding and forming an electro-optic material layer on a partial surface of the bonding dielectric layer on a side facing away from the lower electrode; the projection of the electro-optic material layer on the first substrate covers a partial projection of the lower electrode on the first substrate; the electro-optic material layer includes an isotropic thickness region in the middle and a slope structure at the edge; the thickness of the slope structure gradually decreases along a direction away from the isotropic thickness region; forming an intermediate layer on a surface of the electro-optic material layer on a side facing away from the bonding dielectric layer, the intermediate layer covering the surface of the electro-optic material layer on a side facing away from the bonding dielectric layer and the side surface of the electro-optic material layer; forming a second waveguide core on a partial surface of the intermediate layer on a side facing away from the lower electrode, the projection of the second waveguide core on the first substrate partially covering the projection of the first tapered portion of the first waveguide core on the first substrate; the projection of the first waveguide core on the first substrate is located at both ends of the projection of the second waveguide core on the first substrate; the projection of the electro-optic material layer on the first substrate at least partially covers the projection of the second waveguide core on the first substrate; forming an upper electrode on a side of the second waveguide core facing away from the electro-optic material layer.

2. The method for manufacturing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 1, characterized in that, in the step of forming the second waveguide core, the second waveguide core includes a second intermediate portion having a second width and two second tapered portions with a width gradually decreasing from the second width; the projections of the second tapered portions at both ends of the second waveguide core on the first substrate respectively partially overlap with the projection of one of the first tapered portions on the first substrate, and the tapering directions of the overlapping first tapered portion and the second tapered portion are inverted; the projection of the isotropic thickness region of the electro-optic material layer on the first substrate at least partially covers the projection of the second intermediate portion on the first substrate; the projection of the slope structure of the electro-optic material layer on the first substrate covers a partial projection of the first waveguide core on the first substrate or a partial projection of the second waveguide core on the first substrate.

3. The method for manufacturing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 2, characterized in that, The projection of the equal-thickness region of the electro-optic material layer on the first substrate completely covers the projection of the second intermediate portion on the first substrate, the projection of the second tapered portion on the first substrate, and the projection of the first tapered portion on the first substrate; The projection of the slope structure of the electro-optic material layer on the first substrate covers a partial projection of the first intermediate portion on the first substrate.

4. The method for manufacturing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 2, wherein The projection of the electro-optic material layer on the first substrate partially covers the projection of the second intermediate portion on the first substrate; The projection of the electro-optic material layer on the first substrate does not overlap with the projection of the first tapered portion on the first substrate; The projection of the electro-optic material layer on the first substrate does not overlap with the projection of the second tapered portion on the first substrate.

5. The method for manufacturing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 2, wherein In the step of forming the lower electrode, the lower electrode includes a first electro-optic modulation portion, a first contact portion, and a first transition portion; the first transition portion is located between the first electro-optic modulation portion and the first contact portion; In the step of forming the electro-optic material layer, the projection of the electro-optic material layer on the first substrate covers the projection of the first electro-optic modulation portion on the first substrate; In the step of forming the upper electrode, the upper electrode includes a second electro-optic modulation portion, a second contact portion, and a second transition portion; the second transition portion is located between the second electro-optic modulation portion and the second contact portion; the projection of the second electro-optic modulation portion on the first substrate at least partially overlaps with the projection of the first electro-optic modulation portion on the first substrate, and the overlapping projection at least covers a part of the projection of the second intermediate portion on the first substrate.

6. The method for manufacturing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 5, wherein The projections of the second tapered portions at both ends of the second waveguide core on the first substrate are respectively centered and aligned with the projections of the first tapered portions of one of the first waveguide cores on the first substrate; The second intermediate portion of the second waveguide core is one or a combination of a straight waveguide core, a curved waveguide core, and a spiral waveguide core; the projection of the lower electrode on the first substrate at least covers a part of the projection of the second intermediate portion on the first substrate.

7. The method for manufacturing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 5, wherein After the step of forming the bonding dielectric layer, it includes: Forming a first via hole on a side of the bonding dielectric layer facing away from the first contact portion, the first via hole penetrating through the bonding dielectric layer and exposing a part of the first contact portion; Filling the first via hole to form a first metal plug.

8. The method for manufacturing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 7, wherein The step of forming the upper electrode on a side of the second waveguide core facing away from the electro-optic material layer includes: An upper cladding is formed on a surface of the second waveguide core facing away from the electro-optic material layer, and the upper cladding also covers a side surface of the second waveguide core and a surface of the intermediate layer facing away from the bonding dielectric layer; A second via hole is formed on a surface of the upper cladding facing away from the first metal plug, and the second via hole penetrates through the upper cladding and the intermediate layer and exposes at least a part of the first metal plug; The second via hole is filled to form a second metal plug; the second metal plug is connected to the first contact portion of the lower electrode through the first metal plug; An upper electrode is formed on a side of the electro-optic material layer facing away from the intermediate layer, and a lower electrode pad is formed on a side of the upper cladding facing away from the second metal plug; the lower electrode pad is in contact with and connected to the second metal plug; the lower electrode pad is connected to the first contact portion of the lower electrode through the first metal plug and the second metal plug.

9. The method for manufacturing a heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 1, wherein The process for forming the first waveguide core is the LPCVD process; the material of the first waveguide core is stoichiometric silicon nitride or a silicon nitride / silicon dioxide stack; The process for forming the second waveguide core is the PECVD process; the material of the second waveguide core is silicon or silicon nitride.

10. A heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure, characterized in that Comprising: A first substrate; A lower cladding located on a surface of the first substrate; At least two first waveguide cores located on a partial surface of the lower cladding facing away from the first substrate, each of the first waveguide cores including a first intermediate portion having a first width and a first tapered portion with a width gradually decreasing from the first width; A lower electrode groove located on a side of the lower cladding facing away from the first substrate, and the lower electrode groove penetrates into a part of the thickness of the lower cladding; A lower electrode located in the lower electrode groove; the thickness of the lower electrode is less than or equal to the depth of the lower electrode groove; the projection of the lower electrode on the first substrate does not overlap with the projection of the first waveguide core on the first substrate; A bonding dielectric layer located on a surface of the lower cladding facing away from the first substrate, and the bonding dielectric layer covers the lower electrode, the first waveguide core, and the lower cladding; An electro-optic material layer located on a partial surface of the bonding dielectric layer facing away from the lower electrode; the projection on the first substrate covers a part of the projection of the lower electrode on the first substrate; the electro-optic material layer includes an isotropic thickness region in the middle and a slope structure at the edge; the thickness of the slope structure gradually decreases along a direction away from the isotropic thickness region; An intermediate layer located on a surface of the electro-optic material layer facing away from the bonding dielectric layer, and the intermediate layer covers a surface of the electro-optic material layer facing away from the bonding dielectric layer and a side surface of the electro-optic material layer; A second waveguide core located on a partial surface of the intermediate layer facing away from the lower electrode; the projection of the second waveguide core on the first substrate partially covers the projection of the first tapered portion of the first waveguide core on the first substrate; The projection of the first waveguide core on the first substrate is located at both ends of the projection of the second waveguide core on the first substrate; The projection of the electro-optic material layer on the first substrate at least partially covers the projection of the second waveguide core on the first substrate; The upper electrode is located on a side of the second waveguide core facing away from the electro-optic material layer.

11. The heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 10, characterized in that The second waveguide core includes a second intermediate portion having a second width and two second tapered portions with widths gradually decreasing from the second width; The projections of the second tapered portions at both ends of the second waveguide core on the first substrate respectively overlap partially with the projection of one of the first tapered portions on the first substrate, and the tapered directions of the overlapping first tapered portion and the second tapered portion are inverted; The projection of the equal-thickness region of the electro-optic material layer on the first substrate at least partially covers the projection of the second intermediate portion on the first substrate; The projection of the slope structure of the electro-optic material layer on the first substrate covers a partial projection of the first waveguide core on the first substrate or a partial projection of the second waveguide core on the first substrate.

12. The heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 11, characterized in that The projection of the equal-thickness region of the electro-optic material layer on the first substrate completely covers the projection of the second intermediate portion on the first substrate, the projection of the second tapered portion on the first substrate, and the projection of the first tapered portion on the first substrate; The projection of the slope structure of the electro-optic material layer on the first substrate covers a partial projection of the first intermediate portion on the first substrate.

13. The heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 11, characterized in that The projection of the electro-optic material layer on the first substrate partially covers the projection of the second intermediate portion on the first substrate; The projection of the electro-optic material layer on the first substrate does not overlap with the projection of the first tapered portion on the first substrate; The projection of the electro-optic material layer on the first substrate does not overlap with the projection of the second tapered portion on the first substrate.

14. The heterogeneous integrated electro-optic modulation device with an upper and lower electrode structure according to claim 11, characterized in that The lower electrode includes a first electro-optic modulation portion, a first contact portion, and a first transition portion: the first transition portion is located between the first electro-optic modulation portion and the first contact portion; the projection of the first electro-optic modulation portion on the first substrate at least covers a part of the projection of the second intermediate portion on the first substrate; The projection of the electro-optic material layer on the first substrate covers the projection of the first electro-optic modulation portion on the first substrate; The upper electrode includes a second electro-optic modulation portion, a second contact portion, and a second transition portion: the second transition portion is located between the second electro-optic modulation portion and the second contact portion; the projection of the second electro-optic modulation portion on the first substrate at least partially overlaps with the projection of the first electro-optic modulation portion on the first substrate, and the overlapping projection at least covers a part of the projection of the second intermediate portion on the first substrate.

15. The heterogeneous integrated electro-optic modulation device with the upper and lower electrode structure according to claim 14, characterized in that the heterogeneous integrated electro-optic modulation device further comprises: a first metal plug, passing through the bonding dielectric layer and contacting and connecting with part of the first contact portion; an upper cladding layer, located on a surface of the second waveguide core facing away from the electro-optic material layer, and the upper cladding layer further covers a side surface of the second waveguide core and a surface of the intermediate layer facing away from the bonding dielectric layer; a second metal plug, passing through the upper cladding layer and the intermediate layer, and at least contacting and connecting with part of the first metal plug; a lower electrode pad, located on a surface of the second metal plug exposed by the upper cladding layer; the lower electrode pad contacts and connects with the second metal plug; the lower electrode pad is connected to the first contact portion of the lower electrode through the first metal plug and the second metal plug.

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