Optical waveguide structure and method for manufacturing same, electro-optical modulator, optical module

Abstract

The application provides an optical waveguide structure and a preparation method thereof, an electro-optical modulator and an optical module, and relates to the field of optical communication. The resonant wavelength of the optical waveguide structure is adjusted by adjusting the carrier concentration in the second silicon substrate. The optical waveguide structure comprises an SOI substrate and a transistor arranged on the SOI substrate. The SOI substrate comprises a first silicon substrate, an oxide layer and a second silicon substrate arranged in layers. The refractive index of the second silicon substrate is greater than that of the oxide layer, and the second silicon substrate is used for transmitting an optical signal. The side of the second silicon substrate away from the oxide layer has a protrusion. The transistor comprises a channel layer, a gate dielectric, a gate electrode, a first electrode and a second electrode. The second silicon substrate is multiplexed as the channel layer. In the direction of the first silicon substrate pointing to the oxide layer, the channel layer, the gate dielectric and the gate electrode are arranged in layers. The first electrode and the second electrode are arranged on the channel layer, and the first electrode and the second electrode are arranged on the two sides of the protrusion.

Description

Technical Field

[0001] This application relates to the field of optical communication, and more particularly to an optical waveguide structure and its fabrication method, an electro-optic modulator, an optical module, and an optical communication system. Background Technology

[0002] Silicon photonics (SiP) technology uses silicon as its core material and integrates different optical devices (such as optical waveguides, electro-optic modulators, photodetectors, etc.) onto the same chip through complementary metal oxide semiconductor (CMOS) compatible processes. These optical devices are then used to receive, process, transmit, and transmit optical signals, enabling applications in optical communication, optical sensing, optical transmission, optical computing, and optical storage.

[0003] Electro-optic modulators are one of the key components in silicon photonics, converting electrical signals into optical signals. Common electro-optic modulator structures are divided into two types: micro ring resonators (MRRs) and Mach-Zehnder interferometers (MZIs), both of which are based on silicon-based optical waveguides.

[0004] Taking MRR as an example, it is very challenging to achieve precise control and stability of the resonant wavelength of MRR because it is very sensitive to deviations in the fabrication process and changes in the surrounding environment. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides an optical waveguide structure and its fabrication method, an electro-optic modulator, an optical module, and an optical communication system. By adjusting the carrier concentration in the second silicon substrate, the resonant wavelength of the optical waveguide structure can be adjusted to achieve precise and stable control of the resonant wavelength of the optical waveguide structure.

[0006] In a first aspect, this application provides an optical waveguide structure comprising: a silicon-on-insulator (SOI) substrate and a transistor disposed on the SOI substrate. The SOI substrate includes a first silicon substrate, an oxide layer, and a second silicon substrate stacked together. The refractive index of the second silicon substrate is greater than that of the oxide layer, and the second silicon substrate is used to transmit optical signals. A protrusion is present on the side of the second silicon substrate facing away from the oxide layer. The transistor includes a channel layer, a gate dielectric, a gate electrode, a first electrode, and a second electrode. The second silicon substrate is multiplexed as the channel layer. Along the direction from the first silicon substrate to the oxide layer, the channel layer, the gate dielectric, and the gate electrode are stacked together. The first electrode and the second electrode are disposed on the channel layer, and are located on opposite sides of the protrusion.

[0007] By applying a first voltage to the first and second electrodes and a second voltage to the gate, the charge on the gate can affect the carrier concentration of the channel layer, thus changing the carrier concentration of the silicon waveguide. In this way, the carrier concentration in the second silicon substrate can be effectively adjusted electrically, and the refractive index of the second silicon substrate can be adjusted through the plasma dispersion effect. The change Δn in the refractive index of the second silicon substrate can change the propagation state of light in the second silicon substrate; that is, the change Δn in the refractive index of the second silicon substrate can change the effective refractive index n of the optical mode. eff This allows for the adjustment of the resonant wavelength of the optical waveguide structure, thereby achieving precise and stable control over its resonant wavelength. Specifically:

[0008]

[0009] In Formula 1, Δn represents the change in the refractive index of the second silicon substrate, ΔN e ΔN represents the change in electron concentration. h ΔN represents the change in hole concentration. e and ΔN e Both are proportional to Δn. Those skilled in the art should know that the carrier concentration of the channel layer 11 is, i.e., the electron concentration and the hole concentration. Therefore, adjusting the carrier concentration of the channel layer is equivalent to adjusting the electron and hole concentrations, thereby adjusting the change in the refractive index of the second silicon substrate.

[0010]

[0011] In some possible implementations, the transistor is a ferroelectric transistor, which also includes a floating gate layer and a ferroelectric layer disposed between the gate dielectric and the gate, with the ferroelectric layer disposed between the floating gate layer and the gate.

[0012] By applying a first voltage to the first and second electrodes and a second voltage to the gate, the electric field between the gate and the floating gate layer can change the polarization state of the ferroelectric layer, thereby altering the carrier concentration in the channel layer. Furthermore, the charge on the gate can tunnel into the floating gate layer and remain there, further changing the carrier concentration in the channel layer. In this way, the carrier concentration in the second silicon substrate can be effectively adjusted electrically, and the refractive index of the second silicon substrate can be adjusted through the plasma dispersion effect. The change in the refractive index Δn of the second silicon substrate can change the propagation state of light in the second silicon substrate; that is, the change in the refractive index Δn of the second silicon substrate can change the effective refractive index n of the light mode. eff This allows for the adjustment of the resonant wavelength of the optical waveguide structure, thereby achieving precise and stable control of the resonant wavelength.

[0013] Based on this, this application applies a single voltage pulse to the gate of the ferroelectric transistor, thereby changing the polarization state of the ferroelectric layer and adjusting the carrier concentration in the channel layer, thus regulating the resonant wavelength of the optical waveguide structure. Compared to related technologies that require continuous current supply to the microheater, the solution provided in this application also reduces power consumption.

[0014] In some possible implementations, the overlapping area of ​​the floating gate layer and the second silicon substrate is larger than the overlapping area of ​​the gate and the second silicon substrate. Since the area of ​​a capacitor is proportional to its capacitance, the capacitance of the first capacitor can be made smaller by having a smaller capacitance area, thereby enhancing ferroelectric polarization switching and effectively increasing the adjustable range of carrier concentration.

[0015] The surface of the second silicon substrate facing away from the oxide layer is the upper surface, which includes a plane located around the periphery of the bump. The gate dielectric and the floating gate layer extend from the side of the bump facing away from the oxide layer and from the sidewall of the bump to the plane; the orthogonal projections of the ferroelectric layer and the gate onto the bump are located within the bump area. In this way, the overlapping area of ​​the floating gate layer and the second silicon substrate can be made larger than the overlapping area of ​​the gate and the second silicon substrate, thereby making the capacitance area of ​​the first capacitor smaller than the capacitance area of ​​the second capacitor.

[0016] In some possible implementations, the first and second terminals are electrically connected to a first voltage terminal, and the gate is electrically connected to a second voltage terminal; the absolute value of the first voltage at the first voltage terminal is less than the absolute value of the second voltage at the second voltage terminal. Wherein, in the case of a ferroelectric transistor, the second voltage is a voltage pulse. In this way, the resonant wavelength of the optical waveguide structure can be adjusted using the first and second voltage terminals.

[0017] In some possible implementations, the second silicon substrate includes a first sub-silicon substrate and a second sub-silicon substrate, both of which include a silicon substrate body. The first sub-silicon substrate also includes an n-type doped portion located on the periphery of the first silicon substrate and a p-type doped portion opposite to the n-type doped portion. The transistor is disposed on the second sub-silicon substrate.

[0018] Secondly, this application provides an electro-optic modulator, which includes an input terminal, an output terminal, and the optical waveguide structure described in the first aspect, wherein the optical waveguide structure is connected between the input terminal and the output terminal.

[0019] The second aspect and any implementation thereof correspond to the first aspect and any implementation thereof, respectively. The technical effects of the second aspect and any implementation thereof are similar to those of the first aspect and any implementation thereof, and will not be repeated here.

[0020] Thirdly, this application provides an optical module comprising a light source and the electro-optic modulator described in the second aspect. The light source is used to generate a carrier optical signal and transmit the carrier optical signal to the electro-optic modulator. The electro-optic modulator is used to modulate the carrier optical signal to generate a modulated optical signal.

[0021] The third aspect and any implementation thereof correspond to the first aspect and any implementation thereof, respectively. The technical effects of the third aspect and any implementation thereof are similar to those of the first aspect and any implementation thereof, and will not be repeated here.

[0022] Fourthly, this application provides an optical communication system, which includes a local optical communication device, an optical transmission device, and a remote optical communication device. The local optical communication device includes the optical module described in the third aspect. Optical signals are transmitted between the local optical communication device and the remote optical communication device via the optical transmission device.

[0023] The fourth aspect and any implementation thereof correspond to the first aspect and any implementation thereof, respectively. The technical effects of the fourth aspect and any implementation thereof are similar to those of the first aspect and any implementation thereof, and will not be repeated here.

[0024] Fifthly, this application provides a method for fabricating an optical waveguide structure, comprising: providing an SOI substrate, the SOI substrate comprising a first silicon substrate, an oxide layer, and a second silicon substrate stacked thereon, the refractive index of the second silicon substrate being greater than the refractive index of the oxide layer, the second silicon substrate being used for transmitting optical signals; the second silicon substrate having a protrusion on the side opposite to the oxide layer. A gate dielectric, a gate electrode, a first electrode, and a second electrode of a transistor are formed on the SOI substrate, the second silicon substrate being reused as the channel layer of the transistor; the channel layer, the gate dielectric, and the gate electrode are stacked along the direction from the first silicon substrate to the oxide layer, the first electrode and the second electrode are disposed on the channel layer, and the first electrode and the second electrode are respectively disposed on opposite sides of the protrusion.

[0025] In some possible implementations, after forming the gate dielectric of the transistor on the SOI substrate and before forming the gate, first electrode, and second electrode of the transistor, the fabrication method of the optical waveguide structure further includes: sequentially forming a floating gate layer and a ferroelectric layer on the side of the gate facing away from the SOI substrate.

[0026] The fifth aspect and any implementation thereof correspond to the first aspect and any implementation thereof, respectively. The technical effects of the fifth aspect and any implementation thereof are similar to those of the first aspect and any implementation thereof, and will not be repeated here. Attached Figure Description

[0027] Figure 1 Interaction diagram of each module in the optical communication system provided in the embodiments of this application;

[0028] Figure 2 A schematic diagram of each module in the local optical communication system provided in the embodiments of this application;

[0029] Figure 3 A structural schematic diagram of MRR provided for related technologies;

[0030] Figure 4 MRR transmission spectrum;

[0031] Figure 5a A structural schematic diagram of MRR provided for related technologies;

[0032] Figure 5b A structural schematic diagram of MRR provided for related technologies;

[0033] Figure 5c for Figure 5a and Figure 5b A sectional view along the A1-A2 direction;

[0034] Figure 5d for Figure 5a A sectional view along the B1-B2 direction;

[0035] Figure 6 This is a schematic diagram of the optical waveguide structure provided in the embodiments of this application;

[0036] Figure 7 This is a schematic diagram of the optical waveguide structure provided in the embodiments of this application;

[0037] Figure 8a A schematic diagram of the structure of the MRR provided in the embodiments of this application;

[0038] Figure 8b This is a schematic diagram of the structure of MZI provided in an embodiment of this application;

[0039] Figure 8c A schematic diagram of the structure of a time-delay-based MZI multiplexer provided in an embodiment of this application;

[0040] Figure 8d This is a schematic diagram of the structure of a multiplexer based on an arrayed waveguide grating provided in an embodiment of this application;

[0041] Figure 9 This is a flowchart illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application.

[0042] Figure 10a This is a diagram illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application;

[0043] Figure 10b This is a diagram illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application;

[0044] Figure 10c This is a diagram illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application;

[0045] Figure 11a This is a diagram illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application;

[0046] Figure 11b This is a diagram illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application;

[0047] Figure 11c This is a diagram illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application;

[0048] Figure 11d This is a diagram illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application;

[0049] Figure 11e This is a diagram illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application;

[0050] Figure 12a This is a diagram illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application;

[0051] Figure 12b This is a diagram illustrating the fabrication process of the optical waveguide structure provided in the embodiments of this application;

[0052] Figure 12c This is a diagram illustrating the fabrication process of the optical waveguide structure provided in an embodiment of this application. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0054] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0055] The terms "first" and "second," etc., used in the specification and claims of this application are used to distinguish different objects, not to describe a specific order of objects. For example, "first target object" and "second target object," etc., are used to distinguish different target objects, not to describe a specific order of target objects.

[0056] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0057] In the description of the embodiments in this application, unless otherwise stated, "multiple" means two or more. For example, multiple processing units means two or more processing units; multiple systems means two or more systems.

[0058] This application provides an optical communication system, such as... Figure 1 As shown, the optical communication system includes a signal processor 100, a local optical communication device 200, an optical transmission device 300, and a remote optical communication device 400. When the local optical communication device 200 transmits an optical signal, the remote optical communication device 400 can receive the optical signal; conversely, when the remote optical communication device 400 transmits an optical signal, the local optical communication device 200 can receive the optical signal. For ease of description, the following explanation uses the example of the local optical communication device 200 transmitting an optical signal and the remote optical communication device 400 receiving the optical signal.

[0059] The signal processor 100 processes image, voice, and other data information to generate a first electrical signal, which is then transmitted to the local optical communication device 200. The local optical communication device 200 generates an optical signal based on the received first electrical signal and sends it to the optical transmission device 300. The optical transmission device 300 transmits the received optical signal to the peer optical communication device 400; optionally, the optical transmission device may include an optical fiber. The peer optical communication device 400 extracts information from the received optical signal to obtain image, voice, and other data information corresponding to the first electrical signal generated by the signal processor 100.

[0060] like Figure 2As shown, the local optical communication device 200 includes an optical module, which comprises a light source 201 and an electro-optic modulator 202. The light source 201 generates a carrier optical signal and transmits it to the electro-optic modulator 202. The electro-optic modulator modulates the carrier optical signal according to a first electrical signal sent by the signal processor 100, generating a modulated optical signal, which is then transmitted to the remote optical communication device 400 via the optical transmission device 300.

[0061] The peer optical communication device 400 includes an electro-optic modulator, which receives a modulated optical signal sent by an electro-optic modulator and modulates the modulated optical signal to generate a second electrical signal, so that the peer optical communication device 400 can extract information based on the second electrical signal to obtain image, voice and other data information corresponding to the first electrical signal generated by the signal processor 100.

[0062] As mentioned in the background section, electro-optic modulators are one of the key devices in silicon photonics. Common electro-optic modulator structures are divided into two types: MRR and MZI, both of which are devices based on silicon-based optical waveguides.

[0063] Compared to MZI, MRR devices are smaller, enabling higher density integration and lower power consumption. For example... Figure 3 As shown, the MRR device consists of a bus waveguide and a ring waveguide. Its working principle is as follows: light of a specific wavelength enters the bus waveguide from the input terminal and propagates to the ring waveguide, where it is coupled. Resonance occurs when the phase change of the coupled light after completing a full path in the ring waveguide is an integer multiple of 2π. At resonance, the power of the light of that specific wavelength will be greatly attenuated, and the unattenuated light is then output from the output terminal. Figure 4 The diagram shows a typical transmission spectrum of an MRR, which acts as a stopband filter to filter light at a specific wavelength (i.e., the wavelength at which resonance occurs). For example, light with a wavelength of 1573.90 nm is filtered out when an applied voltage of 0.58 V and a current of less than 0.1 μA is applied.

[0064] Although MRR has certain advantages over MZI, achieving precise control and stability of the resonant wavelength is very challenging due to the high sensitivity of MRR to deviations in the fabrication process and changes in the surrounding environment. Therefore, in current silicon photonics chips, large-size MZI electro-optic modulators have greater applications, but the large size of MZI inherently limits its high-frequency performance.

[0065] Based on this, such as Figures 5a-5cAs shown, this application provides an optical waveguide structure, which includes an SOI substrate and a transistor disposed on the SOI substrate. Figure 5a and Figure 5b A schematic diagram of an optical waveguide structure is shown using MRR as an example. However, the embodiments of this application are not limited to MRR. For ease of explanation, unless otherwise specified, the embodiments of this application are described using MRR as an example.

[0066] The SOI substrate includes a first silicon substrate 101, an oxide layer 102, and a second silicon substrate 103 stacked together. The refractive index of the second silicon substrate 103 is greater than that of the oxide layer 102. The second silicon substrate 103 acts as a silicon waveguide for transmitting optical signals. In this way, the optical signal can undergo total internal reflection in the second silicon substrate 103, preventing the optical signal from being refracted from the second silicon substrate 103 into the oxide layer 102. The optical signal can be transmitted throughout the entire second silicon substrate 103; optionally, most of the light is transmitted in the bumps.

[0067] The second silicon substrate 103 has a protrusion on the side opposite to the oxide layer. The transistor includes a channel layer 11, a gate dielectric 12, a gate electrode 13, a first electrode 14, and a second electrode 15, with the second silicon substrate 103 serving as the channel layer 11. Along the direction from the first silicon substrate 101 to the oxide layer 102, the channel layer 11, the gate dielectric 12, and the gate electrode 13 are stacked. The first electrode 14 and the second electrode 15 are disposed on the channel layer 11, and are located on opposite sides of the protrusion. The first electrode 14 is the source, and the second electrode 15 is the drain; or, the first electrode 14 is the drain, and the second electrode 15 is the source.

[0068] By applying a first voltage to the first electrode 14 and the second electrode 15, and a second voltage to the gate 13, the charge on the gate 13 can affect the carrier concentration of the channel layer 11, that is, change the carrier concentration of the silicon waveguide. In this way, the carrier concentration in the second silicon substrate 103 can be effectively adjusted electrically, and the refractive index of the second silicon substrate 103 can be adjusted through the plasma dispersion effect. The change Δn in the refractive index of the second silicon substrate 103 can change the propagation state of light in the second silicon substrate 103; that is, the change Δn in the refractive index of the second silicon substrate 103 can change the effective refractive index n of the optical mode. eff This allows for the adjustment of the resonant wavelength of the optical waveguide structure, thereby achieving precise and stable control over its resonant wavelength. Specifically:

[0069]

[0070] In Formula 1, Δn represents the change in the refractive index of the second silicon substrate 103, ΔN e ΔN represents the change in electron concentration.h ΔN represents the change in hole concentration. e and ΔN e Both are proportional to Δn. Those skilled in the art should know that the carrier concentration of the channel layer 11 is, i.e., the electron concentration and the hole concentration. Therefore, adjusting the carrier concentration of the channel layer 11 is equivalent to adjusting the electron concentration and the hole concentration, thereby adjusting the change in the refractive index of the second silicon substrate 103.

[0071]

[0072] As mentioned earlier, the change Δn in the refractive index of the second silicon substrate 103 can alter the propagation state of light within the second silicon substrate 103; that is, the change Δn in the refractive index of the second silicon substrate 103 can change the effective refractive index n of the light mode. eff Furthermore, in Formula 2, the change in the effective refractive index Δn eff The change in resonant wavelength Δλ res Proportional to each other, therefore, adjusting the carrier concentration of the channel layer 11 can adjust the change in the refractive index of the second silicon substrate 103 and the effective refractive index n of the optical mode. eff This allows for adjustment of the resonant wavelength Δλ of the optical signal transmitted in the second silicon substrate 103. res .

[0073] It should be understood that this application adjusts the resonant wavelength of the optical waveguide structure by regulating the carrier concentration in the channel layer 11. No transistor switching function is used in this application.

[0074] In some possible implementations, the number of transistors in the optical waveguide structure is not limited in the embodiments of this application. Optionally, the number of transistors in the optical waveguide structure can be one or more. When there are multiple transistors, the multiple transistors can be arranged at different positions in the optical waveguide structure.

[0075] In some possible implementations, other structures can be used instead of the SOI substrate. These structures may include a first substrate and a second substrate stacked together. The second substrate is used to transmit optical signals and is multiplexed as the channel layer 11, and the refractive index of the second substrate is greater than that of the first substrate. Optionally, the material of the second substrate may also include germanium (Ge).

[0076] In some possible ways of implementation, such as Figure 5a As shown, the second silicon substrate 103 includes a first sub-silicon substrate and a second sub-silicon substrate, both of which include a silicon substrate body. Figure 5d As shown, the first sub-silicon substrate also includes an n-type doped portion located on the periphery of the first silicon substrate, and a p-type doped portion opposite to the n-type doped portion. Wherein, as... Figure 5cAs shown, the transistor is disposed on the second sub-silicon substrate.

[0077] Based on this, such as Figure 5d As shown, the silicon waveguide structure may further include a first conductive line 21 and a second conductive line 22. The first conductive line 21 is electrically connected to the n-type doped portion, and the second conductive line is electrically connected to the p-type doped portion. The n-type doped portion can be electrically connected to other conductive structures through the first conductive line 21, and the p-type doped portion can be electrically connected to other conductive structures through the second conductive line 22. Voltages are applied to the n-type doped portion and the p-type doped portion through other conductive structures to modulate the carrier optical signal.

[0078] In some embodiments, to address the impact of fabrication process errors and the surrounding environment on the MRR (Medium Resonance Waveform), the industry typically employs a post-fabrication fine-tuning technique to adjust or trim the MRR resonant wavelength to the design wavelength. Microheaters are commonly used for fine-tuning and precise control of the MRR's resonant wavelength. The principle is to pass current through the microheater, generating heat that alters the refractive index of the waveguide material (i.e., the silicon layer), thereby adjusting the waveguide's resonant frequency. However, microheaters have low thermal fine-tuning efficiency and are volatile, requiring continuous current flow and resulting in significant power consumption.

[0079] Based on this, such as Figure 6 As shown, the transistor in this embodiment can be a ferroelectric transistor. The ferroelectric transistor further includes a floating gate layer 16 and a ferroelectric layer 17. The floating gate layer 16 and the ferroelectric layer 17 are disposed between the gate dielectric 12 and the gate 13, and the ferroelectric layer 17 is disposed between the floating gate layer 16 and the gate 13.

[0080] By applying a first voltage to the first electrode 14 and the second electrode 15, and a second voltage to the gate 13, the electric field between the gate 13 and the floating gate layer 16 can change the polarization state of the ferroelectric layer 17, thereby changing the carrier concentration in the channel layer 11. Furthermore, the charge on the gate 13 can tunnel to the floating gate layer 16 and remain there, further altering the carrier concentration in the channel layer 11. In this way, the carrier concentration in the second silicon substrate 103 can be effectively adjusted electrically, and the refractive index of the second silicon substrate 103 can be adjusted through the plasma dispersion effect. The change Δn in the refractive index of the second silicon substrate 103 can change the propagation state of light in the second silicon substrate 103; that is, the change Δn in the refractive index of the second silicon substrate 103 can change the effective refractive index n of the light mode. eff This allows for the adjustment of the resonant wavelength of the optical waveguide structure, thereby achieving precise and stable control of the resonant wavelength.

[0081] Based on this, in this embodiment, applying a voltage pulse to the gate 13 of the ferroelectric transistor can adjust the carrier concentration in the channel layer 11 by changing the polarization state of the ferroelectric layer 17, thereby adjusting the resonant wavelength of the optical waveguide structure. Compared to related technologies that require continuous current supply to the microheater, the solution provided in this embodiment can also reduce power consumption.

[0082] In some possible ways of implementation, such as Figure 7 As shown, the first electrode 14 and the second electrode 15 are electrically connected to the first voltage terminal V1, and the gate 13 is electrically connected to the second voltage terminal V2. The absolute value of the first voltage applied by the first voltage terminal V1 to the first electrode 14 and the second electrode 15 is less than the absolute value of the second voltage applied by the second voltage terminal V2 to the gate 13. In this way, the resonant wavelength of the optical waveguide structure can be adjusted using the first voltage terminal V1 and the second voltage terminal V2.

[0083] Optionally, the first voltage terminal V1 can be grounded (GND). The magnitude of the second voltage on the second voltage terminal V2 is adjustable, and the second voltage can be positive or negative, as long as the absolute value of the second voltage is greater than the absolute value of the first voltage. Wherein, in the case of a non-ferroelectric transistor, the second voltage applied to the gate 13 by the second voltage terminal V2 is a voltage pulse.

[0084] In some embodiments, the gate 13, the ferroelectric layer 17, and the floating gate layer 16 can constitute a first capacitor, and the floating gate layer 16, the gate dielectric 12, and the channel layer 11 can constitute a second capacitor. The smaller the capacitance of the first capacitor, the larger the voltage drop, which is more conducive to ferroelectric switching.

[0085] Based on this, in this embodiment, the overlapping area of ​​the floating gate layer 16 and the second silicon substrate 103 can be greater than the overlapping area of ​​the gate 13 and the second silicon substrate 103, that is, the capacitance area of ​​the second capacitor is greater than the capacitance value of the second capacitor. Since the capacitance area is proportional to the capacitance value, a smaller capacitance value can be achieved by making the first capacitor have a smaller capacitance area, thereby enhancing ferroelectric polarization reversal and effectively increasing the adjustable range of carrier concentration.

[0086] In some possible implementations, the surface of the second silicon substrate 103 facing away from the oxide layer 102 is the upper surface, which includes a plane located around the periphery of the bump. The gate dielectric 12 and the floating gate layer extend from the side of the bump facing away from the oxide layer 102 and from the sidewall of the bump to the plane; the orthogonal projections of the ferroelectric layer 17 and the gate 13 onto the bump are located within the bump area. In this way, the overlapping area of ​​the floating gate layer 16 and the second silicon substrate 103 can be made larger than the overlapping area of ​​the gate 13 and the second silicon substrate 103, thereby making the capacitance area of ​​the first capacitor smaller than the capacitance area of ​​the second capacitor.

[0087] In some possible implementations, the embodiments of this application do not limit the area ratio of the first capacitor to the second capacitor. Optionally, the area ratio of the first capacitor to the second capacitor may be less than or equal to 1:10.

[0088] In another embodiment, this application also provides an electro-optic modulator, such as... Figures 8a-8d As shown, the electro-optic modulator includes an input terminal (Input), an output terminal (Output), and the optical waveguide structure described in the previous embodiment, with the optical waveguide structure connected between the input terminal (Input) and the output terminal (Output).

[0089] The electro-optic modulator of this application embodiment is applicable to... Figure 8a The MRR and shown Figure 8b The MZI shown. Among them, as... Figure 8a As shown, the MRR includes a bus waveguide and a ring waveguide. The transistors in this embodiment can be disposed at any position on the second sub-silicon substrate within the ring waveguide and at any position on the bus waveguide; as... Figure 8b As shown, the MZI includes a beam splitter, a first modulation arm, a second modulation arm, and a beam combiner. The beam splitter is connected to the input terminal (Input), and the beam combiner is connected to the output terminal (Output). The first and second modulation arms are connected between the beam combiner and the beam splitter. The first and second modulation arms also include a first sub-silicon substrate and a second sub-silicon substrate. Both the first and second sub-silicon substrates include a silicon substrate body. The first sub-silicon substrate further includes an n-type doped portion and a p-type doped portion respectively disposed on the silicon substrate body. Figure 8b The rectangle filled with diagonal lines includes the first sub-silicon substrate. The transistor in this embodiment can be disposed at any position on the second sub-silicon substrate in the first modulation arm and the second modulation arm.

[0090] In addition, electro-optic modulators can also be applied to other silicon waveguide-based wavelength division multiplexing devices, for example, Figure 8c A time-delay-based MZI de-multiplexer is illustrated. The time-delay-based MZI de-multiplexer includes an input terminal, an output terminal, and an optical waveguide structure connecting the input terminal and the output terminal. Alternatively, Figure 8d An arrayed waveguide grating (AWG) based multiplexer is shown. The AWG based multiplexer includes an input terminal, a beam combiner, an output terminal, and an optical waveguide structure connecting the input terminal and the output terminal.

[0091] Furthermore, the other explanations and beneficial effects of the embodiments of this application are the same as those of the previous embodiment, and will not be repeated here.

[0092] In another embodiment, this application also provides a method for fabricating an optical waveguide structure, such as... Figure 9 As shown, this can be achieved through the following steps:

[0093] S110, such as Figure 10a As shown, an SOI substrate is provided. The SOI substrate includes a first silicon substrate 101, an oxide layer 102, and a second silicon substrate 103 stacked together. The refractive index of the second silicon substrate 103 is greater than that of the oxide layer 102. The second silicon substrate 103 is used to transmit optical signals. The side of the second silicon substrate 103 opposite to the oxide layer 102 has a protrusion.

[0094] In some possible implementations, other structures can be used instead of the SOI substrate. These structures may include a first substrate and a second substrate stacked together. The second substrate is used to transmit optical signals and is multiplexed as the channel layer 11, and the refractive index of the second substrate is greater than that of the first substrate. Optionally, the material of the second substrate may also include germanium (Ge).

[0095] S120, a transistor's gate dielectric 12, gate 13, first electrode 14, and second electrode 15 are formed on an SOI substrate, and a second silicon substrate 103 is reused as the transistor's channel layer 11. The channel layer 11, gate dielectric 12, and gate electrode 13 are stacked along the direction from the first silicon substrate 101 to the oxide layer 102, and the first electrode 14 and second electrode 15 are disposed on the channel layer 11, with the first electrode 14 and second electrode 15 respectively disposed on both sides of the protrusion.

[0096] Specifically, such as Figure 10b As shown, an insulating layer 121 and a first conductive layer 131 are sequentially deposited on the second silicon substrate 103. Next, as... Figure 10c As shown, the first conductive layer 131 and the insulating layer 121 are etched. After the first conductive layer 131 is etched, the gate 13 is obtained, and after the insulating layer 121 is etched, the gate dielectric is obtained. Next, as... Figure 5c As shown, a first electrode 14 and a second electrode 15 are formed on both sides of the protrusion. Optionally, dry etching can be used to etch the first conductive layer 131 and the insulating layer 121.

[0097] By applying a first voltage to the first electrode 14 and the second electrode 15, and a second voltage to the gate 13, the charge on the gate 13 can affect the carrier concentration of the channel layer 11, that is, change the carrier concentration of the silicon waveguide. In this way, the carrier concentration in the second silicon substrate 103 can be effectively adjusted electrically, and the refractive index of the second silicon substrate 103 can be adjusted through the plasma dispersion effect. The change Δn in the refractive index of the second silicon substrate 103 can change the propagation state of light in the second silicon substrate 103; that is, the change Δn in the refractive index of the second silicon substrate 103 can change the effective refractive index n of the optical mode. eff This allows for the adjustment of the resonant wavelength of the optical waveguide structure, thereby achieving precise and stable control over its resonant wavelength. Specifically:

[0098]

[0099] In Formula 1, Δn represents the change in the refractive index of the second silicon substrate 103, ΔN e ΔN represents the change in electron concentration. h ΔN represents the change in hole concentration. e and ΔN e Both are proportional to Δn. Those skilled in the art should know that the carrier concentration of the channel layer 11 is, i.e., the electron concentration and the hole concentration. Therefore, adjusting the carrier concentration of the channel layer 11 is equivalent to adjusting the electron concentration and the hole concentration, thereby adjusting the change in the refractive index of the second silicon substrate 103.

[0100]

[0101] As mentioned earlier, the change Δn in the refractive index of the second silicon substrate 103 can alter the propagation state of light within the second silicon substrate 103; that is, the change Δn in the refractive index of the second silicon substrate 103 can change the effective refractive index n of the light mode. eff Furthermore, in Formula 2, the change in the effective refractive index Δn eff The change in resonant wavelength Δλ res Proportional to each other, therefore, adjusting the carrier concentration of the channel layer 11 can adjust the change in the refractive index of the second silicon substrate 103 and the effective refractive index n of the optical mode. eff This allows for adjustment of the resonant wavelength Δλ of the optical signal transmitted in the second silicon substrate 103. res .

[0102] In some embodiments, the transistor is a ferroelectric transistor, and after forming the gate dielectric 12 on the SOI substrate and before forming the gate 13, the first electrode 14, and the second electrode 15, the fabrication method of the optical waveguide structure further includes: as follows: Figure 11aAs shown, an insulating layer 121 and a second conductive layer 161 are sequentially deposited on the second silicon substrate 103; then, as... Figure 11b As shown, the second conductive layer 161 and the insulating layer 121 are etched. After the second conductive layer 161 is etched, the floating gate layer 16 is obtained, and after the insulating layer 121 is etched, the gate dielectric 12 is obtained. Figure 11c and Figure 11d As shown, a ferroelectric material layer 171 and a first conductive layer 131 are sequentially deposited on the floating gate layer 16. Then, as... Figure 11e As shown, the ferroelectric material layer 171 and the first conductive layer 131 are etched. After the first conductive layer 131 is etched, the gate 13 is obtained, and after the ferroelectric material layer 171 is etched, the ferroelectric layer 17 is obtained. Optionally, dry etching can be used to etch the second conductive layer 161 and the insulating layer 121, as well as the ferroelectric material layer 171 and the first conductive layer 131. Next, as... Figure 6 As shown, a first pole 14 and a second pole 15 are formed on both sides of the protrusion.

[0103] Alternatively, if the transistor is a ferroelectric transistor, and the optical waveguide structure is fabricated after the gate dielectric 12 is formed on the SOI substrate and before the gate 13, the first electrode 14, and the second electrode 15 are formed, the fabrication method further includes: Figure 12a As shown, an insulating layer 121, a second conductive layer 161, a ferroelectric material layer 171, and a first conductive layer 131 are sequentially deposited on a second silicon substrate 103; then, as... Figure 12b As shown, using the same semiconductor process, the first conductive layer 131, the ferroelectric material layer 171, the second conductive layer 161, and the insulating layer 121 are etched for the first time. After etching the first conductive layer 131, a conductive layer intermediate pattern 132 is obtained; after etching the ferroelectric material layer 171, a ferroelectric layer intermediate pattern 172 is obtained; after etching the second conductive layer 161, a floating gate layer 16 is obtained; and after etching the insulating layer 121, a gate dielectric 12 is obtained. Next, as... Figure 12c As shown, the conductive layer intermediate pattern 132 and the ferroelectric layer intermediate pattern 172 are etched a second time. After the conductive layer intermediate pattern 132 is etched, the gate 13 is obtained, and after the ferroelectric layer intermediate pattern 172 is etched, the ferroelectric layer 17 is obtained.

[0104] Of course, other processes can also be used to fabricate ferroelectric transistors, and this application does not limit the specific methods used in the embodiments.

[0105] By applying a first voltage to the first electrode 14 and the second electrode 15, and a second voltage to the gate 13, the electric field between the gate 13 and the floating gate layer 16 can change the polarization state of the ferroelectric layer 17, thereby changing the carrier concentration in the channel layer 11. Furthermore, the charge on the gate 13 can tunnel to the floating gate layer 16 and remain there, further altering the carrier concentration in the channel layer 11. In this way, the carrier concentration in the second silicon substrate 103 can be effectively adjusted electrically, and the refractive index of the second silicon substrate 103 can be adjusted through the plasma dispersion effect. The change Δn in the refractive index of the second silicon substrate 103 can change the propagation state of light in the second silicon substrate 103; that is, the change Δn in the refractive index of the second silicon substrate 103 can change the effective refractive index n of the light mode. eff This allows for the adjustment of the resonant wavelength of the optical waveguide structure, thereby achieving precise and stable control of the resonant wavelength.

[0106] Based on this, in this embodiment, applying a voltage pulse to the gate 13 of the ferroelectric transistor can adjust the carrier concentration in the channel layer 11 by changing the polarization state of the ferroelectric layer 17, thereby adjusting the resonant wavelength of the optical waveguide structure. Compared to related technologies that require continuous current supply to the microheater, the solution provided in this embodiment can also reduce power consumption.

[0107] In some possible implementations, the material of the gate dielectric 12 may include SiO2 and high-k dielectric materials. The material of the floating gate layer 16 may include conductive materials, such as transparent oxide semiconductors like tungsten (W), titanium nitride (TiN), and indium tin oxide (ITO). The material of the ferroelectric layer 17 may include hafnium-based ferroelectric materials.

[0108] Furthermore, the other explanations and beneficial effects of the embodiments of this application are the same as those of the first embodiment, and will not be repeated here.

[0109] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An optical waveguide structure, characterized in that, include: The SOI substrate includes a first silicon substrate, an oxide layer, and a second silicon substrate stacked together. The refractive index of the second silicon substrate is greater than that of the oxide layer. The second silicon substrate is used to transmit optical signals. The side of the second silicon substrate facing away from the oxide layer has a protrusion. The transistor disposed on the SOI substrate includes a channel layer, a gate dielectric, a gate, a first electrode, and a second electrode. The second silicon substrate is reused as the channel layer. The channel layer, the gate dielectric, and the gate are stacked along the direction from the first silicon substrate to the oxide layer. The first electrode and the second electrode are disposed on the channel layer and are respectively disposed on both sides of the protrusion.

2. The optical waveguide structure according to claim 1, characterized in that, The transistor is a ferroelectric transistor, which further includes a floating gate layer and a ferroelectric layer. The floating gate layer and the ferroelectric layer are disposed between the gate dielectric and the gate, and the ferroelectric layer is disposed between the floating gate layer and the gate.

3. The optical waveguide structure according to claim 2, characterized in that, The overlapping area of ​​the floating gate layer and the second silicon substrate is greater than the overlapping area of ​​the gate and the second silicon substrate.

4. The optical waveguide structure according to claim 3, characterized in that, The surface of the second silicon substrate facing away from the oxide layer is the upper surface, and the upper surface includes a plane located around the protrusion; The gate dielectric and the floating gate layer extend from the side of the protrusion away from the oxide layer and from the sidewall of the protrusion to the plane; the orthogonal projection of the ferroelectric layer and the gate onto the protrusion is located within the protrusion area.

5. The optical waveguide structure according to any one of claims 1-4, characterized in that, The first electrode and the second electrode are electrically connected to the first voltage terminal, and the gate is electrically connected to the second voltage terminal; the absolute value of the first voltage at the first voltage terminal is less than the absolute value of the second voltage at the second voltage terminal. Wherein, if the transistor is a ferroelectric transistor, the second voltage is a voltage pulse.

6. The optical waveguide structure according to any one of claims 1-5, characterized in that, The second silicon substrate includes a first sub-silicon substrate and a second sub-silicon substrate. Both the first sub-silicon substrate and the second sub-silicon substrate include a silicon substrate body. The first sub-silicon substrate also includes an n-type doped portion located on the periphery of the first silicon substrate and a p-type doped portion opposite to the n-type doped portion. The transistor is disposed on the second sub-silicon substrate.

7. An electro-optic modulator, characterized in that, It includes an input terminal, an output terminal, and the optical waveguide structure according to any one of claims 1-6, wherein the optical waveguide structure is connected between the input terminal and the output terminal.

8. An optical module, characterized in that, Includes a light source and the electro-optic modulator as described in claim 7; The light source is used to generate a carrier optical signal and transmit the carrier optical signal to the electro-optic modulator; The electro-optic modulator is used to modulate the carrier optical signal to generate a modulated optical signal.

9. An optical communication system, characterized in that, It includes local optical communication equipment, optical transmission equipment, and remote optical communication equipment, wherein the local optical communication equipment includes the optical module as described in claim 8; The optical communication device at the local end and the optical communication device at the remote end transmit optical signals through the optical transmission device.

10. A method for fabricating an optical waveguide structure, characterized in that, include: An SOI substrate is provided, the SOI substrate comprising a first silicon substrate, an oxide layer, and a second silicon substrate stacked thereon, the refractive index of the second silicon substrate being greater than the refractive index of the oxide layer, the second silicon substrate being used for transmitting optical signals; the second silicon substrate having a protrusion on the side opposite to the oxide layer; A gate dielectric, a gate electrode, a first electrode, and a second electrode of a transistor are formed on the SOI substrate, and the second silicon substrate is reused as the channel layer of the transistor. The channel layer, the gate dielectric, and the gate electrode are stacked along the direction from the first silicon substrate to the oxide layer. The first electrode and the second electrode are disposed on the channel layer and are respectively disposed on both sides of the protrusion.

11. The method for fabricating the optical waveguide structure according to claim 10, characterized in that, The method for fabricating the optical waveguide structure after forming the gate dielectric of the transistor on the SOI substrate and before forming the gate, the first electrode, and the second electrode of the transistor further includes: A floating gate layer and a ferroelectric layer are sequentially formed on the side of the gate that is away from the SOI substrate.

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