A heterogeneous integrated photonic architecture and method of fabrication thereof

Abstract

This invention relates to the field of optoelectronic integration, and particularly to a multi-material heterogeneous integrated photonic architecture and its fabrication method, comprising a substrate, an intermediate transition layer, and a top functional layer. The intermediate transition layer is disposed above the substrate and includes transport layers and fill layers alternately stacked in the vertical direction, with the refractive index of the transport layers being higher than that of the fill layers. The intermediate transition layer is divided into multiple horizontally arranged functional regions in the horizontal direction, with different total thicknesses of the fill layers in different functional regions. An optical coupling device for interlayer optical signal transmission is disposed within the intermediate transition layer. The top functional layer is disposed on the upper surface of the intermediate transition layer. This invention breaks the design constraints of traditional uniform substrate environments, enabling customized substrate environments for devices in or above different functional regions, taking into account the differentiated substrate environment requirements of various types of devices, and improving the overall performance of the chip.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic integration, and in particular to a heterogeneous integrated photonic architecture and its fabrication method. Background Technology

[0002] Optoelectronic integration technology is developing towards higher integration and higher overall performance. Silicon-based optoelectronics is compatible with CMOS (Complementary Metal-Oxide-Semiconductor) processes, but it is limited by the material properties of silicon, resulting in physical limitations in active devices such as light sources and high-speed modulators. Therefore, multi-material heterogeneous integration, combining the performance advantages of various materials such as III-V group materials (providing light sources) and thin-film lithium niobate (providing high-speed modulation), has become the development trend of on-chip integrated optics.

[0003] However, different types of devices have different, and sometimes contradictory, requirements for the substrate environment. For example, lasers require a substrate with high thermal conductivity to achieve efficient heat dissipation and ensure stable device performance and high output power; while high-speed modulators need to be located away from low-resistivity silicon substrates to reduce microwave signal loss and increase bandwidth. In existing monolithic integration solutions, the substrate environment is often uniform across different regions of the chip. A single substrate environment specification cannot simultaneously meet the needs of multiple different types of devices. During the design process, trade-offs must be made between the performance of different devices, resulting in the overall chip performance not reaching its optimal level.

[0004] Therefore, how to provide an integrated photonic architecture that can take into account the different substrate environment requirements of various types of devices is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a heterogeneous integrated photonic architecture and its fabrication method to solve the problem that the uniform substrate environment in the prior art cannot simultaneously meet the needs of multiple different types of devices, resulting in the chip's overall performance not reaching its optimal level.

[0006] To address the aforementioned technical problems, this invention provides a heterogeneous integrated photonic architecture, comprising a substrate, an intermediate transition layer, and a top functional layer;

[0007] The intermediate transition layer is disposed above the substrate and includes a transport layer and a fill layer that are alternately stacked in the vertical direction, wherein the refractive index of the transport layer is higher than that of the fill layer;

[0008] The intermediate transition layer is divided into multiple horizontally arranged functional areas in the horizontal direction, and the total thickness of the filling layer in different functional areas is different.

[0009] The intermediate transition layer is equipped with an optical coupling device for interlayer optical signal transmission.

[0010] The top functional layer is disposed on the upper surface of the intermediate transition layer.

[0011] Optionally, the heterogeneous integrated photonic architecture includes multiple functional layers, and the top functional layer is one of the multiple functional layers;

[0012] The difference in the total thickness of the filler layer between the different functional layers and the substrate is greater than or equal to 1 micrometer.

[0013] Optionally, in the heterogeneous integrated photonic architecture, the optical coupling device is an interlayer grating coupler pair;

[0014] The interlayer grating coupler includes a radiation grating and a receiving grating. The radiation grating is disposed in one of the transmission layers, and the receiving grating is disposed in another transmission layer above the radiation grating and aligned with the radiation grating.

[0015] Optionally, in the heterogeneous integrated photonic architecture, the radiation principal axis of the radiation grating and the receiving principal axis of the receiving grating both form an inclined coupling angle with the normal direction of the substrate;

[0016] The tilt coupling angle ranges from 6 degrees to 12 degrees, including the endpoint value.

[0017] Optionally, in the heterogeneous integrated photonic architecture, the transport layer is made of silicon nitride, and the filling layer is made of silicon dioxide.

[0018] Optionally, in the heterogeneous integrated photonic architecture, the radiation grating and / or the receiving grating is at least one of a subwavelength grating structure, an apodized grating structure, and a gradient periodic grating structure.

[0019] Optionally, in the heterogeneous integrated photonic architecture, a reflective layer is provided vertically below the radiation grating and / or vertically above the receiving grating;

[0020] The reflective layer includes at least one of a metallic reflective layer and a distributed Bragg reflective layer.

[0021] Optionally, in the heterogeneous integrated photonic architecture, a passive optical loop device is further provided in the intermediate transition layer;

[0022] The passive optical loop devices are distributed in different layers of the transmission layer;

[0023] The passive optical circuit device is at least one of the following: cross-waveguide, directional coupler, multimode interference beam splitter, microring resonator, arrayed waveguide grating, and Bragg grating.

[0024] A method for fabricating a heterogeneous integrated photonic architecture, the method comprising:

[0025] Provide substrate;

[0026] An intermediate transition layer is formed by alternately distributing a fill layer and a transport layer above the substrate; the total thickness of the fill layer in different functional areas is different, and mutually aligned grating structures are formed in the transport layers of different layers; the intermediate transition layer is divided into multiple horizontally arranged functional areas in the horizontal direction.

[0027] After planarizing the upper surface of the intermediate transition layer, a second functional material substrate is set.

[0028] The second functional material substrate is patterned to form the top functional layer.

[0029] Optionally, in the fabrication method of the heterogeneous integrated photonic architecture, before forming the intermediate transition layer, the method further includes:

[0030] A first functional material substrate is disposed on the upper surface of the substrate, and a first functional layer is patterned to form it; when forming the intermediate transition layer, the filling layer above the first functional layer is controlled to a preset target thickness.

[0031] The heterogeneous integrated photonic architecture provided by this invention includes a substrate, an intermediate transition layer, and a top functional layer. The intermediate transition layer is disposed above the substrate and includes a transport layer and a fill layer that are alternately stacked in the vertical direction. The refractive index of the transport layer is higher than that of the fill layer. The intermediate transition layer is divided into multiple horizontally arranged functional regions in the horizontal direction, and the total thickness of the fill layer in different functional regions is different. An optical coupling device for interlayer optical signal transmission is provided in the intermediate transition layer. The top functional layer is disposed on the upper surface of the intermediate transition layer.

[0032] This invention divides the intermediate transition layer horizontally into multiple laterally arranged functional regions, with varying total thicknesses of the filling layers in different functional regions. This breaks free from the design constraints of traditional uniform substrate environments. Devices in or above functional regions with smaller total filling layer thicknesses can utilize the substrate more closely, while devices above functional regions with larger total filling layer thicknesses can be positioned further away from the substrate. This provides customized substrate environments for different types of devices, accommodating the diverse substrate requirements of various device types and optimizing the overall performance of the chip. Simultaneously, the optical coupling devices within the intermediate transition layer enable interlayer optical signal transmission, allowing optical interconnection between devices mounted at different vertical heights and ensuring the integrity of optical signal transmission within the architecture. This invention also provides a method for fabricating a heterogeneous integrated photonic architecture with the aforementioned beneficial effects. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A schematic diagram of a specific embodiment of the heterogeneous integrated photonic architecture provided by the present invention;

[0035] Figure 2-1 A top view schematic diagram of a specific embodiment of the interlayer grating coupler pair in the heterogeneous integrated photonic architecture provided by the present invention;

[0036] Figure 2-2 This is a side view of a specific embodiment of the interlayer grating coupler pair in the heterogeneous integrated photonic architecture provided by the present invention.

[0037] Figure 3 A schematic flowchart illustrating a specific embodiment of the fabrication method for the heterogeneous integrated photonic architecture provided by the present invention;

[0038] Figure 4-1 A two-dimensional distribution diagram of the optical mode field intensity of the interlayer grating coupler corresponding to the heterogeneous integrated photonic architecture provided by the present invention on the propagation cross section;

[0039] Figure 4-2 The interlayer energy coupling efficiency spectrum of the interlayer grating coupler corresponding to the heterogeneous integrated photonic architecture provided by the present invention;

[0040] Figure 5 A comparison of microwave loss as a function of frequency for coplanar waveguide electrodes with different filler layer thicknesses;

[0041] Figures 6-1 to 6-14 This is a schematic diagram of the structure corresponding to each step in a specific embodiment of the method for fabricating the heterogeneous integrated photonic architecture provided by the present invention.

[0042] Figure label:

[0043] 10-Substrate; 20-Intermediate transition layer; 21-Transmission layer; 22-Fill layer; 30-Top functional layer; 40-First functional layer; 51-Radiation grating; 52-Receiver grating; 60-Reflective layer; 70-Passive optical loop device. Detailed Implementation

[0044] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] The core of this invention is to provide a heterogeneous integrated photonic architecture, the structural schematic diagram of one specific embodiment of which is shown below. Figure 1 As shown, this is referred to as Specific Implementation Method 1, which includes a substrate 10, an intermediate transition layer 20, and a top functional layer 30.

[0046] An intermediate transition layer 20 is disposed above the substrate 10 and includes a transport layer 21 and a fill layer 22 that are alternately stacked in the vertical direction. The refractive index of the transport layer 21 is higher than that of the fill layer 22.

[0047] The intermediate transition layer 20 is divided into multiple horizontally arranged functional areas in the horizontal direction, and the total thickness of the filling layer 22 in different functional areas is different.

[0048] The intermediate transition layer 20 is equipped with an optical coupling device for interlayer optical signal transmission;

[0049] The top functional layer 30 is located on the upper surface of the intermediate transition layer 20.

[0050] In this invention, "above", "below", and "vertical direction" are all based on the upper surface of the substrate 10. "Above" means the direction away from the substrate 10, and "horizontal direction" means the direction parallel to the upper surface of the substrate 10. These will not be elaborated further below.

[0051] The substrate 10 can be a single-crystal silicon substrate, an SOI (Silicon On Insulator) substrate, or other hard substrates, such as quartz, sapphire, diamond, silicon nitride, and other substrate materials with high thermal conductivity or high insulation. The substrate can be selected according to actual needs, and the present invention does not limit it.

[0052] The refractive index of the transmission layer 21 is higher than that of the fill layer 22. The transmission layer 21, which is covered by the fill layer 22, can confine the optical signal and form an optical waveguide. That is, the transmission layer 21 is the waveguide layer that carries the optical signal transmission, while the fill layer 22 serves to both cover the waveguide and isolate the layers. The alternatingly stacked multiple transmission layers 21 are located at different vertical heights, providing multiple independent wiring layers for the optical signal.

[0053] The intermediate transition layer 20 is divided into multiple horizontally arranged functional regions in the horizontal direction, and the total thickness of the filling layer 22 in different functional regions is different. That is, the filling layer 22 of the intermediate transition layer 20 exhibits a non-uniform spatial thickness distribution in the horizontal direction. Devices in or above functional regions with a smaller total thickness of filling layer 22 are closer to the substrate 10 and can utilize the physical properties of the substrate 10 nearby, such as heat dissipation by taking advantage of the high thermal conductivity of the substrate 10. Devices above functional regions with a larger total thickness of filling layer 22 are farther from the substrate 10, thus avoiding adverse effects from the physical properties of the substrate 10, such as preventing high-frequency signals from leaking into the semiconductor substrate. Therefore, the present invention can provide a customized substrate environment for different types of devices on the same substrate 10.

[0054] Optical coupling devices are disposed within the intermediate transition layer 20 to enable the transmission of optical signals between layers at different vertical heights, allowing optical interconnection between devices carried in different functional areas and at different vertical heights.

[0055] The top functional layer 30 is disposed on the upper surface of the intermediate transition layer 20. Preferably, the top functional layer 30 is disposed on the upper surface of the intermediate transition layer 20 by heterobonding. The material of the top functional layer 30 can be thin-film lithium niobate or thin-film lithium tantalate, or it can be III-V semiconductor materials such as barium titanate, high-molecular electro-optic polymers, lead zirconate titanate, indium phosphide or gallium arsenide, silicon-based materials, germanium-based materials, as well as two-dimensional materials such as graphene and transition metal sulfides. The material can be selected according to actual needs, and the present invention does not limit it.

[0056] In a preferred embodiment, the heterogeneous integrated photonic architecture includes multiple functional layers, with the top functional layer 30 being one of the multiple functional layers; the difference in the total thickness of the filling layer 22 between the different functional layers and the substrate 10 is greater than or equal to 1 micrometer.

[0057] You can refer to this. Figure 1 In this preferred embodiment, the multiple functional layers include a first functional layer 40 and a top functional layer 30. The first functional layer 40 is formed on the upper surface of the substrate 10, for example, a laser active layer made of a III-V group material; the top functional layer 30 is disposed on the upper surface of the intermediate transition layer 20, for example, a modulator functional layer made of thin-film lithium niobate. There is no filler layer 22 between the first functional layer 40 and the substrate 10, or the thickness of the filler layer 22 above the first functional layer 40 is small, preferably controlled to be 2 micrometers or less, and more preferably controlled to be less than 1 micrometer. This forms a low thermal resistance heat dissipation channel that runs directly from the first functional layer 40 to the highly thermally conductive substrate 10, shortening the heat conduction path, significantly reducing thermal resistance, lowering the junction temperature of the laser, and improving output power and long-term reliability. Meanwhile, the total thickness of the filler layer 22 in the functional region where the top functional layer 30 is located is large, preferably greater than 8 micrometers, and more preferably greater than 10 micrometers. This allows the high-frequency electrodes on the top functional layer 30 to be completely away from the underlying semiconductor substrate 10, physically blocking the leakage of high-frequency microwave signals to the substrate 10, reducing radio frequency loss, and improving the bandwidth performance of the modulator.

[0058] You can refer to this. Figure 5 , Figure 5 This is a comparison graph showing the microwave loss of coplanar waveguide electrodes with different filler layer thicknesses as a function of frequency. The horizontal axis represents the modulation frequency of the microwave signal (0 to 100 GHz), and the vertical axis represents the RF transmission parameter S21 of the coplanar waveguide electrode (in dB), used to quantify the microwave RF loss per unit length. Figure 5 It can be seen that when the filler layer thickness is 2 micrometers, the distance between the substrate and the metal electrode is too close, and the high-frequency signal is significantly attenuated; while when the total thickness of the filler layer is greater than 8 micrometers, the device still maintains low loss at a high frequency of 100 gigahertz, which verifies that its high-frequency electrical transmission performance has been significantly improved.

[0059] Therefore, this preferred embodiment simultaneously satisfies the high heat dissipation efficiency requirement of the laser and the high-frequency electro-optic performance requirement of the modulator on the same chip, realizing the decoupling of the thermal and electrical environments of different functional layers, and making the overall performance of the entire chip optimal.

[0060] It should be noted that for functional areas with a small total thickness of the filling layer 22, thermally conductive vias can be made through the filling layer 22 by deep etching, and the thermally conductive vias can be filled with high thermal conductivity metals such as tungsten or high thermal conductivity non-metallic media such as aluminum nitride and diamond, so that the heat generated by the functional layer can be directly conducted vertically downward to the substrate 10 for heat dissipation. The choice can be made according to actual needs, and the present invention does not limit it.

[0061] In a preferred embodiment, the optical coupling device is an interlayer grating coupler pair; the interlayer grating coupler pair includes a radiation grating 51 and a receiving grating 52, the radiation grating 51 is disposed in a transmission layer 21, and the receiving grating 52 is disposed in another transmission layer 21 above the radiation grating 51 and is aligned with the radiation grating 51.

[0062] Traditional evanescent wave coupling schemes rely on the overlap of mode fields at the tails of the upper and lower waveguides to achieve energy exchange. Their coupling efficiency decreases exponentially with the vertical spacing between the two waveguides, which is typically limited to within 1 micrometer and has small process tolerances. When optical signals need to cross thicker fill layers, to achieve acceptable coupling efficiency, the length of the tapered transition region must be extended to hundreds of micrometers or even millimeters, resulting in low chip integration, high process complexity, and high device insertion loss. This preferred embodiment converts the waveguide mode into a radiation mode that propagates in free space within the fill layer 22. The radiation grating 51 radiates the horizontally propagating waveguide mode obliquely towards the upper fill layer 22. The receiving grating 52, aligned with the radiation grating 51, receives this radiation beam and converts it back into the waveguide mode in the upper transmission layer 21. Spatial optical transmission does not decrease exponentially with distance like evanescent waves, thus overcoming the physical constraint of vertical interlayer distance in evanescent wave coupling. This enables efficient cross-layer transmission with large vertical spacing, and the large alignment tolerance between the two gratings simplifies the manufacturing process.

[0063] Specifically, the thickness of the filling layer 22 spanned in the vertical direction by the interlayer grating coupler can be greater than 10 micrometers. With this large vertical spacing, this preferred embodiment does not need to increase the device size of the coupling region. It only requires a device size of less than 100 micrometers × 30 micrometers to achieve compact and efficient cross-layer transmission with a theoretical insertion loss of less than 2 dB. Under the same vertical span and device performance, the traditional thermally adiabatic tapered waveguide scheme may require a tapered waveguide with a length greater than 500 micrometers.

[0064] You can refer to this. Figure 2-1 and Figure 2-2 The two figures above are schematic diagrams of a specific embodiment of an interlayer grating coupler, wherein... Figure 2-1 This is a top view. Figure 2-2As shown in the side view, the interlayer grating coupler is divided into a transition region, a gradient region, and a radiation region along the direction of optical signal propagation. The entire waveguide loop and grating structure are surrounded by a low-refractive-index filling layer 22. The transition region is located at the front end of the coupler and contains a locally spatially overlapping structure of the functional layer and the transmission layer 21. The end of the functional layer is processed into an adiabatic gradient pointed structure with a gradually decreasing width. The corresponding starting end of the transmission layer 21 spatially overlaps with it in the vertical direction. Through the adiabatic transition of the tapered waveguide, the horizontally propagating optical field can be smoothly transferred from the functional layer to the transmission layer 21 with extremely low insertion loss and a high mode overlap factor. The gradient region is located between the rear end of the transition region and the front end of the radiation region. In the gradient region, the transverse width of the transmission layer 21 gradually widens adiabatably in the horizontal direction, and the mode volume of the optical mode gradually increases during propagation to match the size of the optical field reaching the leading edge of the radiation region with the grating structure of the subsequent radiation region. The radiation region is located at the end of the gradient region. It is formed by micro- and nano-etching on the widened transmission layer 21, creating a row of periodic grating lines with a preset period, duty cycle and etching depth. When the optical mode is transmitted to the radiation region, the periodic grating structure converts the horizontally propagating mode into a free beam radiating obliquely upward, enabling it to cross the thick filling layer 22 and achieve three-dimensional interlayer optical interconnection with a large vertical distance.

[0065] You can refer to this. Figure 4-1 and Figure 4-2 The two figures above show the simulation results of the interlayer grating coupler with a vertical spacing of 10 micrometers. The simulation uses the finite difference time-domain method. Figure 4-1 The two-dimensional distribution of the optical mode field intensity on the propagation cross section intuitively demonstrates the complete three-dimensional transmission process of the optical signal after it is transmitted from the lower waveguide to the radiation grating 51, radiates obliquely upward at a preset angle through the 10-micrometer-thick filling layer 22, and is efficiently received and converted into a horizontal waveguide mode by the receiving grating 52. Figure 4-2 The image shows the interlayer energy coupling efficiency spectrum after structural parameter optimization for a specific center wavelength (taking 1550 nm as an example). The peak center of its spectral response curve is located at 1550 nm, and the peak interlayer energy coupling efficiency exceeds 0.75, which verifies the cross-layer transmission performance of this preferred embodiment.

[0066] Furthermore, a scheme of cascading multiple interlayer grating couplers can be adopted to realize continuous transmission routing of optical signals between three or more vertical transmission layers 21. The selection can be made according to actual needs, and the present invention does not limit it.

[0067] In a preferred embodiment, the radiation principal axis of the radiation grating 51 and the receiving principal axis of the receiving grating 52 both form an inclined coupling angle with the normal direction of the substrate 10, and the inclined coupling angle ranges from 6 degrees to 12 degrees, including the endpoint value.

[0068] The grating period and duty cycle of the radiation grating 51 are optimized to ensure that the radiation angle of the light field matches the tilt coupling angle of the grating. The receiving grating 52 is aligned with the radiation grating 51, and their tilt coupling angles are matched, thus achieving efficient coupling of the light field. The aforementioned tilt coupling angle range is an optimal range obtained through simulation optimization. Within this range, back reflection of light can be effectively suppressed, improving the coupling efficiency of spatial transmission.

[0069] In a preferred embodiment, the transport layer 21 is made of silicon nitride, and the filler layer 22 is made of silicon dioxide.

[0070] Silicon nitride is a high-refractive-index dielectric material with low optical loss. Its refractive index is stable at around 2.0 in the communication band, while silicon dioxide has a refractive index of approximately 1.45. The significant difference in refractive index between the two provides excellent confinement of optical signals, and both are compatible with CMOS processes. Of course, the material of the transmission layer 21 can also be alumina, amorphous silicon, or other dielectrics deposited using CMOS-compatible processes. The material of the filling layer 22 can also be a doped or undoped low-dielectric-constant dielectric, benzocyclobutene, or other polymer materials to obtain a thicker isolation layer. The choice can be made according to actual needs, and this invention does not impose any limitations on this.

[0071] In a preferred embodiment, the radiation grating 51 and / or the receiving grating 52 are at least one of a subwavelength grating structure, an apodized grating structure, and a gradient periodic grating structure.

[0072] For conventional periodic grating structures, the transmission spectrum of interlayer grating couplers exhibits wavelength selectivity, with a preset 1 dB operating bandwidth, which is approximately 30 to 40 nanometers in conventional designs. This preferred embodiment configures the radiation grating 51 and / or the receiving grating 52 as a subwavelength grating structure, an apodized grating structure, or a graded periodic grating structure, etc., to further broaden the 1 dB operating bandwidth and accommodate a wider spectral response.

[0073] It should be noted that the heterogeneous integrated photonic architecture provided by this invention has an extremely wide wavelength adaptive customization capability. The structural parameters of the interlayer grating coupler pair, including grating period, duty cycle and etching depth, can be adjusted and configured according to the center wavelength of the device response band to adapt to any specific communication band from 1260 to 1360 nm (O band), 1360 to 1460 nm (E band), 1460 to 1530 nm (S band), 1530 to 1565 nm (C band), 1565 to 1625 nm (L band) to 1625 to 1675 nm (U band). The selection can be made according to actual needs, and this invention does not limit it.

[0074] In a preferred embodiment, a reflective layer 60 is provided vertically below the radiation grating 51 and / or vertically above the receiving grating 52; the reflective layer 60 includes at least one of a metallic reflective layer and a distributed Bragg reflective layer.

[0075] You can refer to this. Figure 1 A reflective layer 60 is formed vertically below the radiation grating 51 and / or vertically above the receiving grating 52. The metal reflective layer can be an aluminum reflective layer or a gold reflective layer. The reflective layer 60 can reflect the light that originally leaked or was lost by upward scattering to the substrate 10 back to the preset tilt coupling direction, thereby improving the directivity of the interlayer grating to close to 100% and further reducing the insertion loss of the interlayer grating coupler pair.

[0076] In a preferred embodiment, a passive optical loop device 70 is also provided in the intermediate transition layer 20; the passive optical loop device 70 is distributed in the transmission layers 21 of different layers; the passive optical loop device 70 is at least one of the following: cross optical waveguide, directional coupler, multimode interference beam splitter, micro-ring resonator, arrayed waveguide grating, and Bragg grating.

[0077] In large-scale and complex integrated optical circuits, traditional single-layer optical waveguide wiring can limit chip integration density and routing flexibility due to crosstalk. This preferred embodiment distributes the passive optical loop device 70 in transmission layers 21 at different vertical heights, making full use of the multi-layer wiring space of the intermediate transition layer 20, avoiding crosstalk from single-layer wiring, and improving the overall chip integration density and routing flexibility.

[0078] The heterogeneous integrated photonic architecture provided by the present invention includes a substrate 10, an intermediate transition layer 20, and a top functional layer 30. The intermediate transition layer 20 is disposed above the substrate 10 and includes a transmission layer 21 and a fill layer 22 that are alternately stacked in the vertical direction. The refractive index of the transmission layer 21 is higher than that of the fill layer 22. The intermediate transition layer 20 is divided into multiple horizontally arranged functional regions in the horizontal direction, and the total thickness of the fill layer 22 in different functional regions is different. An optical coupling device for interlayer optical signal transmission is provided in the intermediate transition layer 20. The top functional layer 30 is disposed on the upper surface of the intermediate transition layer 20. This invention divides the intermediate transition layer 20 into multiple horizontally arranged functional regions in the horizontal direction, and makes the total thickness of the filling layer 22 in different functional regions different. This breaks the design constraints of the traditional uniform substrate environment and can provide a customized substrate environment for different types of devices on the same substrate 10. It takes into account the different needs of various types of devices for the substrate environment, so that the overall performance of the chip can be optimized. At the same time, the optical coupling device in the intermediate transition layer 20 realizes the optical signal transmission between layers, enabling optical interconnection between devices carried in different functional regions and at different vertical heights, ensuring the integrity of optical signal transmission within the architecture.

[0079] This invention also provides a method for fabricating a heterogeneous integrated photonic architecture, the flowchart of one specific embodiment of which is shown below. Figure 3 As shown, referred to as Specific Implementation Method Two, the method for fabricating heterogeneous integrated photonic architectures is used to fabricate any of the above-mentioned heterogeneous integrated photonic architectures, including:

[0080] S101: Provides substrate 10.

[0081] As mentioned above, the substrate 10 can be a single-crystal silicon substrate, an SOI substrate, or other rigid substrates, and this invention does not limit the scope of the invention.

[0082] S102: Filling layer 22 and transport layer 21 are alternately disposed above substrate 10 to form intermediate transition layer 20; the total thickness of filling layer 22 in different functional areas is different, and grating structures aligned with each other are formed in transport layer 21 in different layers; intermediate transition layer 20 is divided into multiple horizontally arranged functional areas in the horizontal direction.

[0083] Specifically, this step can be achieved by alternately performing a cyclic process of "filler layer deposition, planarization, transport layer deposition, and transport layer patterning": First, a dielectric material (such as silicon dioxide) is globally deposited on the substrate 10 to form a filler layer 22 with surface undulations; then, the filler layer 22 is globally planarized using a chemical mechanical polishing process until a preset flatness is achieved; then, a high refractive index dielectric material (such as silicon nitride deposited by plasma-enhanced chemical vapor deposition) is globally deposited on the surface of the planarized filler layer 22 to form a transport layer 21; then, the patterning transfer of the transport layer 21 is completed by ultraviolet exposure and etching processes to fabricate a passive optical waveguide, a passive optical loop device 70, and a radiation grating 51 for upward radiating light field. Repeat the above cycle, deposit the filler layer 22 again and perform chemical mechanical polishing. Repeat the photolithography and etching process on the planarized surface to fabricate another transmission layer 21. Precisely align the underlying structure to form the receiving grating 52, thereby constructing a large vertically spaced interlayer grating coupler pair. Subsequently, the top transmission layer 21 can be deposited and patterned to form a top passive waveguide loop for docking with subsequent heteromaterials. By controlling the deposition and planarization of the filler layer 22 in each functional region in the above cycle, the total thickness of the filler layer 22 in different functional regions can be made different.

[0084] S103: After planarizing the upper surface of the intermediate transition layer 20, a second functional material substrate is set.

[0085] Specifically, a chemical mechanical polishing (CMP) process can be implemented to precisely control the total thickness of the intermediate transition layer 20 and polish it to produce an ultra-smooth, high-cleanliness upper surface that meets wafer-level bonding requirements. Subsequently, a high-quality secondary functional material substrate (such as a thin-film lithium niobate substrate) is bonded to the upper surface of the intermediate transition layer 20 using heterogeneous bonding technology. Planarization ensures the flatness and cleanliness of the bonding interface, making it unaffected by the roughness of the underlying structure. This provides a more favorable substrate environment for heterogeneous integration of multiple materials, reduces bonding failures caused by roughness or defects, and thus improves the process yield of multi-material heterogeneous integration.

[0086] It should be noted that, in addition to using chip-level or wafer-level direct bonding processes, the second functional material substrate can also be grown using direct heteroepitaxial growth processes, utilizing techniques such as molecular beam epitaxy or metal-organic chemical vapor deposition to directly grow single-crystal or polycrystalline electro-optic thin films in situ on the planarized upper surface; alternatively, spin coating, dip coating, or spray coating techniques can be used to uniformly coat the polymer electro-optic precursor solution onto the upper surface, which then forms an electro-optic functional layer after curing; or it can be prepared using precision thin film deposition techniques such as atomic layer deposition or pulsed laser deposition, which can be selected according to actual needs, and this invention does not limit the choice.

[0087] S104: Pattern the second functional material substrate to form the top functional layer 30.

[0088] The top functional layer 30 was fabricated by patterning etching, and finally an on-chip integrated multi-material heterogeneous photonic chip was obtained.

[0089] As a more specific implementation method, the above preparation method can be further refined into the following steps:

[0090] Step 1, as follows Figure 6-1 As shown, a substrate 10 is provided, which can be a single-crystal silicon substrate, an SOI substrate, or other rigid substrates.

[0091] Step two, as Figure 6-2 As shown, a first functional material substrate is integrated on the upper surface of the substrate 10 using heterogeneous bonding technology. The first functional material substrate can be a III-V group epitaxial wafer, and it is patterned by photolithography and etching processes to form a first functional layer 40 located in a specific functional region.

[0092] Step 3, as Figure 6-3 As shown, a dielectric material is globally deposited on the substrate 10 and the first functional layer 40 to form a filling layer 22 with surface morphology undulations.

[0093] Step four, as Figure 6-4As shown, a chemical mechanical polishing process is used to planarize the filler layer 22 globally until a preset flatness is achieved, and the filler layer 22 above the first functional layer 40 is controlled at a preset target thickness.

[0094] Step 5, as Figure 6-5 As shown, a high refractive index dielectric material is globally deposited on the surface of the planarized filling layer 22 to form the bottom transport layer 21.

[0095] Step six, as Figure 6-6 As shown, the patterned transfer of the transmission layer 21 is completed by ultraviolet exposure and etching process, and a passive optical waveguide, a passive optical loop device 70 and a radiation grating 51 for upward radiating optical field are fabricated. The passive optical loop device 70 can be a micro ring resonator, a beam splitter, etc.

[0096] Step seven, as Figure 6-7 As shown, a dielectric material is deposited globally again as a new fill layer 22, which covers the patterned transport layer 21.

[0097] Step eight, as Figure 6-8 As shown, a chemical mechanical polishing process is performed again to planarize the entire surface, providing a high-precision plane for the next layer of micro-nano processing.

[0098] Step nine, as Figure 6-9 As shown, deposition, photolithography and etching processes are repeated on the planarized surface to process another transmission layer 21, and the underlying structure is precisely aligned to form a receiving grating 52, thereby constructing a large vertically spaced interlayer grating coupler pair.

[0099] Step 10, as follows Figure 6-10 As shown, the upper waveguide core material is globally deposited to form the top transmission layer 21.

[0100] Step eleven, as follows Figure 6-11 As shown, the top transmission layer 21 is etched and patterned to form a top passive waveguide loop for docking with subsequent heteromaterials.

[0101] Step twelve, as follows Figure 6-12 As shown, the last fill layer 22 of the global deposition is used to cover the passive waveguide structure at the top.

[0102] Step thirteen, as follows Figure 6-13 As shown, a chemical mechanical polishing process is implemented to precisely control the total thickness of the intermediate transition layer 20. Figure 6-13 The reference numerals of the intermediate transition layer 20 point to the bidirectional arrows indicating the total thickness of the intermediate transition layer 20, and the upper surface is polished to meet the requirements of wafer-level bonding, resulting in an ultra-smooth, high-cleanliness surface.

[0103] Step fourteen, as follows Figure 6-14 As shown, a high-quality second functional material substrate is bonded to the upper surface of the intermediate transition layer 20 using heterogeneous bonding technology. The second functional material substrate can be a thin-film lithium niobate substrate. Subsequently, the top functional layer 30 is fabricated by patterned etching, and finally an on-chip integrated multi-material heterogeneous photonic chip is obtained.

[0104] Steps three through twelve above involve alternatingly performing a cyclic process of "filler layer deposition, planarization, transport layer deposition, and transport layer patterning." By controlling the number of depositions of the filler layer 22 in each functional region and the remaining thickness after planarization, the total thickness of the filler layer 22 in different functional regions can be made different. This allows for the simultaneous construction of functional regions with smaller total filler layer thicknesses and functional regions with larger total filler layer thicknesses on the same substrate 10. Simultaneously, by fabricating radiation gratings 51 and receiving gratings 52 within the transport layers 21 of different layers in the cycle, interlayer grating couplers and passive optical loop devices 70 can be embedded at different vertical heights. It should be noted that the specific process types and parameters in the above steps are merely examples and can be adjusted according to actual conditions. This invention does not limit these aspects.

[0105] In a preferred embodiment, before forming the intermediate transition layer 20, the method further includes:

[0106] A first functional material substrate is disposed on the upper surface of the substrate 10, and a first functional layer 40 is patterned to form it; when forming the intermediate transition layer 20, the filling layer 22 above the first functional layer 40 is controlled to a preset target thickness.

[0107] Specifically, a first functional material substrate (such as a III-V epitaxial wafer) can be integrated on the upper surface of the substrate 10 using heterogeneous bonding technology, and patterned by photolithography and etching processes to form a first functional layer 40 located in a specific functional region. In the subsequent formation of the intermediate transition layer 20, the filling layer 22 above the first functional layer 40 is controlled to a preset target thickness by chemical mechanical polishing. The target thickness is preferably 2 micrometers or less, and more preferably 1 micrometer or less, so as to form a low thermal resistance heat dissipation channel from the first functional layer 40 directly to the highly thermally conductive substrate 10. The specific beneficial effects can be referred to above and will not be repeated here.

[0108] The method for fabricating the heterogeneous integrated photonic architecture provided in this specific embodiment is in contrast to the heterogeneous integrated photonic architecture described above. For specific technical details, please refer to the previous text. This invention will not repeat them here.

[0109] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0110] It should be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0111] The heterogeneous integrated photonic architecture and its fabrication method provided by this invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of this invention.

Claims

1. A heterogeneous integrated photonic architecture, characterized in that, Includes a substrate, an intermediate transition layer, and a top functional layer; The intermediate transition layer is disposed above the substrate and includes a transport layer and a fill layer that are alternately stacked in the vertical direction, wherein the refractive index of the transport layer is higher than that of the fill layer; The intermediate transition layer is divided into multiple horizontally arranged functional areas in the horizontal direction, and the total thickness of the filling layer in different functional areas is different. The intermediate transition layer is equipped with an optical coupling device for interlayer optical signal transmission. The top functional layer is disposed on the upper surface of the intermediate transition layer.

2. The heterogeneous integrated photonic architecture as described in claim 1, characterized in that, It includes multiple functional layers, and the top functional layer is one of the multiple functional layers; The difference in the total thickness of the filler layer between the different functional layers and the substrate is greater than or equal to 1 micrometer.

3. The heterogeneous integrated photonic architecture as described in claim 1, characterized in that, The optical coupling device is an interlayer grating coupler pair; The interlayer grating coupler includes a radiation grating and a receiving grating. The radiation grating is disposed in one of the transmission layers, and the receiving grating is disposed in another transmission layer above the radiation grating and aligned with the radiation grating.

4. The heterogeneous integrated photonic architecture as described in claim 3, characterized in that, The radiation principal axis of the radiation grating and the receiving principal axis of the receiving grating both form an inclined coupling angle with the normal direction of the substrate; The tilt coupling angle ranges from 6 degrees to 12 degrees, including the endpoint value.

5. The heterogeneous integrated photonic architecture as described in claim 3, characterized in that, The transport layer is made of silicon nitride, and the filling layer is made of silicon dioxide.

6. The heterogeneous integrated photonic architecture as described in claim 3, characterized in that, The radiation grating and / or the receiving grating are at least one of the following: a subwavelength grating structure, an apodized grating structure, and a gradient periodic grating structure.

7. The heterogeneous integrated photonic architecture as described in claim 3, characterized in that, A reflective layer is provided vertically below the radiation grating and / or vertically above the receiving grating; The reflective layer includes at least one of a metallic reflective layer and a distributed Bragg reflective layer.

8. The heterogeneous integrated photonic architecture as described in any one of claims 1 to 7, characterized in that, The intermediate transition layer is also equipped with a passive optical circuit device. The passive optical loop devices are distributed in different layers of the transmission layer; The passive optical circuit device is at least one of the following: cross-waveguide, directional coupler, multimode interference beam splitter, microring resonator, arrayed waveguide grating, and Bragg grating.

9. A method for fabricating a heterogeneous integrated photonic architecture, characterized in that, The method for fabricating the heterogeneous integrated photonic architecture is used to fabricate the heterogeneous integrated photonic architecture as described in any one of claims 1 to 8, comprising: Provide substrate; An intermediate transition layer is formed by alternately distributing a fill layer and a transport layer above the substrate; the total thickness of the fill layer in different functional areas is different, and mutually aligned grating structures are formed in the transport layers of different layers; the intermediate transition layer is divided into multiple horizontally arranged functional areas in the horizontal direction. After planarizing the upper surface of the intermediate transition layer, a second functional material substrate is set. The second functional material substrate is patterned to form the top functional layer.

10. The method for fabricating the heterogeneous integrated photonic architecture as described in claim 9, characterized in that, Before forming the intermediate transition layer, the following is also included: A first functional material substrate is disposed on the upper surface of the substrate, and a first functional layer is patterned to form it; when forming the intermediate transition layer, the filling layer above the first functional layer is controlled to a preset target thickness.

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