Silicon grating coupler, preparation method of stack structure and electronic device

Abstract

The application provides a silicon grating coupler, a preparation method of a stack structure and electronic equipment, and relates to the technical field of optical communication. The silicon grating coupler comprises an optical waveguide, an optical fiber and a stack structure; the stack structure is arranged between the optical waveguide and the optical fiber; in a vertical direction perpendicular to a horizontal plane on which the optical waveguide is placed, the stack structure comprises at least two optical film layers; the optical film layers are etched with optical patterns; wherein the optical film layers adjust the optical characteristics of an initial light beam emitted by the optical waveguide based on the optical patterns, obtain an adjusted light beam, and transmit the adjusted light beam to the optical fiber; the optical characteristics include at least one of the propagation direction, the divergence angle and the mode profile of the light beam. The optical film layers with optical patterns are arranged on the stack structure of the back-end metal interconnection layer, so that the propagation direction, the divergence angle, the mode profile and the like of the light beam emitted by the optical waveguide are adjusted through the stack structure, so that the shaping and turning of the light beam are realized, and the quality of the light beam is improved through a low-cost device structure.

Description

Technical Field

[0001] This application relates to the field of optical communication technology, and more specifically, to a silicon grating coupler, a method for fabricating a stacked structure, and an electronic device. Background Technology

[0002] Silicon grating couplers are key interface devices for silicon photonic chips to connect optical signals with external fiber arrays. Currently, traditional grating couplers manufactured using standard silicon photonics processes (such as those based on SOI wafers) generally suffer from the following problems: Mode mismatch: The optical mode size in silicon waveguides is very small, while the mode field diameter (MFD) of standard single-mode fiber (SMF-28) is large. Although grating couplers can achieve size expansion, the mode profile of their emitted light does not match the near-Gaussian mode of the fiber well. Large divergence angle: Due to the relatively small diffraction aperture of the grating, the divergence angle of its emitted beam is usually large. This results in an excessively large spot size when the light propagates to the fiber endface, preventing most of the light energy from being collected by the fiber and causing high coupling loss. Unfavorable exit angle: Standard grating couplers typically have a tilted exit angle (e.g., 10-15 degrees off-center from the vertical) to couple first-order diffracted light to the fiber while preventing second-order reflected light from returning to the waveguide. This tilted coupling increases the difficulty and cost of alignment during packaging. Small coupling tolerance: Due to the large divergence angle and poor mode matching, the coupling efficiency is highly sensitive to the position and angular deviation of the fiber, meaning the coupling tolerance is very small, requiring extremely high precision in the packaging process.

[0003] In existing solutions, to address the aforementioned issues, complex apodization or subwavelength structures are typically designed within the silicon layer itself, inverted conical lenses are used in conjunction with optical fibers, or polymer lenses are added during post-processing on the chip surface. These methods are limited by the two-dimensional planar structure of the silicon layer itself, resulting in limited control over the vertical optical field. Furthermore, they add extra process steps and packaging costs, hindering large-scale, low-cost CMOS-compatible manufacturing. Consequently, existing silicon grating couplers are complex in structure, high in cost, and poor in performance, making them impractical and unable to meet current optical communication needs. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a silicon grating coupler, a method for fabricating a stacked structure, and an electronic device, so as to improve the problem of poor practicality of silicon grating couplers in the prior art.

[0005] To address the aforementioned issues, this application provides a silicon grating coupler, which includes an optical waveguide, an optical fiber, and a stacked structure.

[0006] The stack structure is disposed between the optical waveguide and the optical fiber;

[0007] In a direction perpendicular to the plane where the optical waveguide is placed, the stacked structure includes at least two optical film layers; optical patterns are etched on the optical film layers; wherein, the optical film layers adjust the optical characteristics of the initial beam emitted from the optical waveguide based on the optical patterns to obtain an adjusted beam, and transmit the adjusted beam to the optical fiber;

[0008] The optical characteristics include at least one of the following: beam propagation direction, divergence angle, and pattern profile.

[0009] In the above implementation process, the original stacked structure of the back-end metal interconnect layer in the silicon grating coupler was redesigned. The stacked structure now includes multiple layers of optically patterned films in the vertical direction. This stacked structure is positioned between the optical waveguide and the optical fiber. The optical patterns in the optical films within the stacked structure adjust the optical characteristics of the initial beam emitted from the waveguide, thereby adjusting the propagation direction, divergence angle, or mode profile of the initial beam. This achieves beam shaping and redirection, resulting in a corrected, adjusted beam, which is then transmitted to the optical fiber for processing. This approach eliminates the need for complex lens structures within the silicon grating coupler for beam processing, resulting in lower device costs, packaging complexity, and packaging costs. Furthermore, the stacked structure effectively processes beams from various directions, providing good beam adjustment. This low-cost device structure improves beam quality and meets the optical communication needs of various application scenarios.

[0010] Optionally, the stack structure further includes: a bottom layer structure, a middle layer structure, and a top layer structure;

[0011] In the vertical direction, the optical film layer is disposed between the bottom layer and the top layer;

[0012] An intermediate layer structure is provided between two adjacent optical film layers; wherein the intermediate layer structure is used to physically isolate the two adjacent optical film layers.

[0013] In the above implementation process, the stack structure also includes a corresponding bottom layer structure, intermediate layer structure and top layer structure. In the vertical direction, the optical film layer is set between the bottom layer structure and the top layer structure to protect and encapsulate the optical film layer through the bottom layer structure and the top layer structure. In addition, in order to ensure the physical independence of each optical film layer, a corresponding intermediate layer structure is also set between two adjacent optical film layers to physically isolate the two adjacent optical film layers through the intermediate layer structure and support the optical film layer, so as to obtain a stack structure with stable structure and stable function.

[0014] Optionally, the intermediate layer structure is a transparent dielectric material.

[0015] In the above implementation process, since the light beam needs to be transmitted through the stack structure, in order to enable the light beam to be transmitted normally, the intermediate layer structure can be set as a transparent dielectric material so that the light beam can pass through the intermediate layer structure normally.

[0016] Optionally, a metallic material is deposited in the non-patterned regions of the optical film layer that do not have the optical pattern.

[0017] The non-patterned areas are used as etching stop layers or diffusion barrier layers.

[0018] In the above implementation process, since this application does not introduce new materials, non-standard deposition processes, or new device structures into the silicon grating coupler, corresponding metal materials are deposited in the unpatterned areas of the optical film layer based on the original fabrication process of the back-end metal interconnect layer. This allows the unpatterned areas to serve as etching stop layers or diffusion barrier layers, thus fulfilling the original function of the back-end metal interconnect layer. This enables the back-end metal interconnect layer to simultaneously achieve multiple different types of functions, effectively improving beam quality within a low-cost silicon grating coupler.

[0019] Optionally, the optical waveguide is provided with a light outlet, through which the initial beam transmitted by the optical waveguide is emitted;

[0020] The pattern area of ​​the optical pattern on each optical film layer is determined based on the light emission parameters of the light emission port; wherein, the light emission parameters include: the position, size and light emission angle of the light emission port.

[0021] In the above implementation process, an output port is provided on the optical waveguide to emit the initial beam transmitted through the output port. In order to transmit the initial beam in a targeted manner, the position and size of the pattern area on each optical film layer in the stack structure can be determined based on the output parameters such as the position, size, and output angle of the output port. This allows the optical pattern in each optical film layer to effectively process the initial beam, thereby improving the effect of each optical film layer in adjusting the optical characteristics of the beam and improving the beam quality of the final output adjusted beam.

[0022] Optionally, in the vertical direction, the multiple optical film layers form a multilayer diffractive lens, a metamaterial lens, or a cascaded metasurface based on multiple optical patterns.

[0023] In the above implementation process, in the vertical direction, the multilayer optical film can form various optical device structures with different functions, such as multilayer diffractive lenses, metamaterial lenses, or cascaded metasurfaces, based on multiple optical patterns. Different functional optical device structures can be selected and set according to actual needs, so as to adjust the optical characteristics of the initial beam accordingly through different functional optical device structures.

[0024] Optionally, the optical pattern includes at least one of concentric rings, nanopillars, and lines.

[0025] In the above implementation process, the optical pattern can include various patterns of different shapes such as concentric rings, nanopillars, and lines obtained after specific patterning etching, so as to adjust the optical properties of the initial beam accordingly through different optical patterns.

[0026] Optionally, the multiple optical patterns on the multiple optical film layers are different.

[0027] In the above implementation process, in order to achieve different functional structures, the functions of the multilayer optical films may differ. Correspondingly, the multiple optical patterns set on the multilayer optical films may also differ, so as to achieve a variety of different functions such as correcting the beam propagation direction, reducing the beam divergence angle, and reshaping the beam pattern profile.

[0028] Optionally, the optical film layer comprises a silicon-based nitride thin film layer.

[0029] In the above implementation process, the optical film layer may include a silicon-based nitride thin film layer. Without introducing new materials, the optical properties of the beam can be adjusted on the optical film layer, as well as the corresponding etching stop and diffusion blocking functions.

[0030] Secondly, embodiments of this application provide a method for fabricating a stack structure, the method comprising:

[0031] Deposit optical film materials in the underlying structure;

[0032] The optical film material is photolithographically etched and etched based on a defined photomask to obtain an optical film with an optical pattern.

[0033] An intermediate layer material is deposited on the optical film to obtain an intermediate layer structure, and the intermediate layer structure is polished.

[0034] The optical film layer is further fabricated on the intermediate layer structure, and the intermediate layer structure is further fabricated on the optical film layer until the top optical film layer is obtained;

[0035] A top-layer structure is deposited on the top-layer optical film.

[0036] In the above implementation process, corresponding optical film materials can be deposited on the underlying structure, and photolithography and etching can be performed on the optical film materials based on a pre-determined photomask to obtain an optical film with an optical pattern. An intermediate layer material is then deposited on the optical film to obtain an intermediate layer structure, which is then polished to improve its flatness. This process continues, with optical films and intermediate layers fabricated alternately, until the final optical film layer, the top optical film layer, is fabricated. The top structure is then deposited on the top optical film layer, resulting in a complete stacked structure. This method allows for the addition of photolithography and etching processes to the existing standard back-end metal interconnect layer process to obtain the corresponding optical patterns. The overall fabrication process of the stacked structure is relatively simple and highly precise, making it easy to mass-produce.

[0037] Optionally, the method for determining the photomask includes:

[0038] Determine the beam parameters of the initial beam emitted by the light waveguide; wherein, the beam parameters include beam angle, light field, and mode;

[0039] Based on the adjustment requirements of the initial beam, the target parameters of the output adjusted beam are determined;

[0040] Based on the beam parameters and the target parameters, and in conjunction with the design structure of the stack structure, reverse design or iterative optimization is performed to determine the photomask for each optical film layer in the stack structure; wherein the photomask corresponds to the optical pattern on the corresponding optical film layer.

[0041] In the above implementation process, the target parameters of the initial beam emitted by the light waveguide, combined with the adjustment requirements of the initial beam, can be determined. Based on the beam parameters and target parameters, reverse design or iterative optimization is performed to determine the photomask corresponding to the optical pattern of each optical film layer in the stack structure that can adjust the initial beam into the adjusted beam. Photolithography and etching processes are then performed based on the photomask to set the corresponding optical pattern on the optical film layer. This allows for the determination of the actual required optical pattern according to the specific beam adjustment needs, satisfying adjustment requirements in various application scenarios.

[0042] Thirdly, embodiments of this application also provide an electronic device, which includes the silicon grating coupler described in any one of the first aspects above.

[0043] In summary, the embodiments of this application provide a silicon grating coupler, a method for fabricating a stacked structure, and an electronic device. An optical film layer with an optical pattern is disposed on the stacked structure of the back-end metal interconnect layer, so as to adjust the propagation direction, divergence angle, mode profile, etc. of the light beam emitted by the light waveguide through the stacked structure, so as to realize the shaping and steering of the light beam and improve the quality of the light beam through a low-cost device structure. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of the structure of a silicon grating coupler provided in an embodiment of this application;

[0046] Figure 2 This is a schematic diagram of a stack structure provided in an embodiment of this application;

[0047] Figure 3 A schematic diagram of an optical pattern provided for an embodiment of this application;

[0048] Figure 4 A schematic flowchart illustrating a method for fabricating a stack structure according to an embodiment of this application;

[0049] Figure 5 This is a schematic flowchart illustrating another method for preparing a stack structure provided in an embodiment of this application.

[0050] Icons: 110-Optical waveguide; 120-Fiber optic cable; 130-Stacked structure; 131-Optical film layer; 111-Placement plane; 112-Vertical direction; 132-Bottom layer structure; 133-Intermediate layer structure; 134-Top layer structure; 135-Metallic material. Detailed Implementation

[0051] 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 a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of the embodiments of this application.

[0052] In existing solutions, to address issues such as mode mismatch, large divergence angle, emission angle deviation, and small coupling tolerance in silicon grating couplers, complex apodization or subwavelength structures are typically designed within the silicon layer itself, inverted conical lenses are used in conjunction with optical fibers, or polymer lenses are added during post-processing on the chip surface. These methods are either limited by the two-dimensional planar structure of the silicon layer itself, resulting in limited control over the vertical optical field, and also add extra process steps and packaging costs. This hinders large-scale, low-cost CMOS-compatible manufacturing, leading to existing silicon grating couplers being complex in structure, high in cost, and poor in performance, thus limiting their practicality and failing to meet current optical communication needs.

[0053] To address the aforementioned issues, this application provides a silicon grating coupler, a method for fabricating a stacked structure, and an electronic device. An optical film layer with an optical pattern is disposed on the stacked structure of the back-end metal interconnect layer. The propagation direction, divergence angle, and mode profile of the light beam emitted by the light waveguide are adjusted through the stacked structure to achieve beam shaping and steering, thereby improving the quality of the light beam through a low-cost device structure.

[0054] Optionally, the silicon grating coupler provided in this application embodiment can be installed in various types of electronic devices, such as optical sensing and measurement devices, laser devices, optical communication and information processing devices, imaging and display devices, etc.

[0055] Please see Figure 1 , Figure 1 This is a schematic diagram of a silicon grating coupler provided in an embodiment of the present application. The silicon grating coupler may include: an optical waveguide 110, an optical fiber 120, and a stacked structure 130.

[0056] The stack structure 130 is disposed between the optical waveguide 110 and the optical fiber 120.

[0057] It should be noted that the stack structure 130 is the BEOL (back-end metal interconnect layer) structure in the standard semiconductor CMOS process flow. The optical waveguide 110 may include devices such as silicon waveguides that can transmit optical signals. The optical fiber 120 may include various types of devices such as single-mode fiber, polarization-maintaining fiber, multimode fiber, lens fiber, and fiber array. The corresponding optical waveguide 110 and optical fiber 120 can be designed according to actual needs.

[0058] It should be noted that, on the vertical direction 112 perpendicular to the plane 111 of the optical waveguide 110, the stack structure 130 includes at least two optical film layers 131; optical patterns are etched on the optical film layers 131; wherein, the optical film layers 131 adjust the optical characteristics of the initial beam emitted from the optical waveguide 110 based on the optical patterns to obtain an adjusted beam, and transmit the adjusted beam to the optical fiber 120. The original stack structure 130 of the back-end metal interconnect layer in the silicon grating coupler was redesigned so that the stack structure 130 includes multiple optical film layers 131 with etched optical patterns in the vertical direction 112. The stack structure 130 is disposed between the optical waveguide 110 and the optical fiber 120. The optical characteristics of the initial beam emitted from the optical waveguide 110 are adjusted by the optical patterns in the optical film layers 131 in the stack structure 130, thereby adjusting the propagation direction, divergence angle or mode profile of the initial beam, realizing the shaping and turning of the initial beam, obtaining the corrected adjusted beam, and transmitting the adjusted beam to the optical fiber 120 for processing.

[0059] The optical characteristics may include one or more beam-related properties such as beam propagation direction, divergence angle, and mode profile. The process by which the optical film layer 131 adjusts the optical characteristics of the initial beam may include: correcting the propagation direction: correcting the tilted initial beam of the optical waveguide 110 to a near-vertical exit beam, greatly facilitating vertical alignment with the fiber optic array 120. Reducing the divergence angle (collimation): compensating for the diverging wavefront through the phase modulation capability of the multilayer optical film layer 131, collimating or slightly focusing it, thereby reducing the divergence angle. Reshaping the mode profile: making the energy distribution of the exit spot of the adjusted beam closer to a Gaussian distribution, thereby improving the overlap integral with the mode of the fiber optic array 120.

[0060] It should be noted that the silicon grating coupler provided in this application does not introduce new materials or non-standard deposition steps. It utilizes the multilayer films already present in the BEOL stack of standard CMOS processes (e.g., 45nm, 90nm, 130nm process nodes). In standard dual-damascene copper interconnect processes, thin film layers are typically deposited between each metal (Cu) layer and / or via as etch-stop layers (ESL) or copper diffusion barrier layers. Furthermore, multiple optical film layers 131 can be set in the stack structure 130. Each optical film layer 131 is specifically patterned and etched to obtain a corresponding optical pattern. Multiple optical patterns are multiple separate two-dimensional patterns in the vertical direction 112, thereby constituting a whole three-dimensional optical element. Compared with a single-layer structure, this multilayer structure provides more layers and more times the design freedom, enabling more precise and independent control of the phase, amplitude, and polarization of the initial beam.

[0061] exist Figure 1 The illustrated embodiment provides a novel grating coupler structure that is low-cost, fully compatible with CMOS processes, and can effectively control the emitted light field profile (including divergence angle and propagation direction). This effectively solves problems such as the mismatch between the emitted light mode and the fiber 120 mode in existing silicon grating couplers, excessive divergence angle, and unfavorable emission angle for packaging, leading to low coupling efficiency and small alignment tolerance. It eliminates the need for complex lens structures in silicon grating couplers to process the beam, resulting in lower device cost, packaging process difficulty, and packaging cost. Furthermore, the stacked structure 130 can effectively process beams in various directions, providing good beam adjustment. This low-cost device structure improves beam quality and meets the optical communication needs of various application scenarios.

[0062] Please see Figure 2 , Figure 2This is a schematic diagram of a stacked structure provided in an embodiment of this application. The stacked structure 130 further includes a bottom layer structure 132, an intermediate layer structure 133, and a top layer structure 134. In the vertical direction 112, an optical film layer 131 is disposed between the bottom layer structure 132 and the top layer structure 134, and an intermediate layer structure 133 is disposed between two adjacent optical film layers 131. The intermediate layer structure 133 is used to physically isolate two adjacent optical film layers 131. The stack structure 130 also includes a bottom layer structure 132, an intermediate layer structure 133, and a top layer structure 134. In the vertical direction 112, an optical film layer 131 is disposed between the bottom layer structure 132 and the top layer structure 134 to protect and encapsulate the optical film layer 131. In order to ensure the physical independence of each optical film layer 131, an intermediate layer structure 133 is also disposed between two adjacent optical film layers 131 to physically isolate the two adjacent optical film layers 131 and support the optical film layers 131, thereby obtaining a structurally stable and functionally stable stack structure 130.

[0063] For example, the optical film layer 131 can be a BEOL optical structure, that is, an existing multilayer silicon nitride (SiN) thin film layer in the back-end metal interconnect layer, on which a specific optical pattern is etched, so that the multilayer SiN thin film layers work together to form an optical element located between the optical waveguide 110 and the optical fiber 120.

[0064] Optionally, the bottom layer structure 132 may include a silicon substrate and a silicon dioxide layer, and the top layer structure 134 may also include a corresponding silicon dioxide layer or silicon layer structure.

[0065] It should be noted that, since the light beam needs to be transmitted through the stack structure 130, the intermediate layer structure 133 is made of a transparent dielectric material in order to enable the light beam to be transmitted normally, so that the light beam can pass through the intermediate layer structure 133 normally.

[0066] For example, transparent dielectric materials can include a variety of materials such as silicon dioxide, silicon nitride, silicon oxynitride, aluminum oxide, and titanium dioxide, and the appropriate material can be selected according to the actual refractive index requirements.

[0067] It should be noted that, Figure 2 Only one feasible embodiment with three optical film layers 131 is shown in the diagram; the structures of other numbers of optical film layers 131 will not be described in detail.

[0068] It should be noted that only a portion of the optical film layer 131 has optical patterns. In the unpatterned areas of the optical film layer 131, a metal material 135 is deposited, serving as an etch stop layer or a diffusion barrier layer. Since this application does not introduce new materials, non-standard deposition processes, or new device structures into the silicon grating coupler, the unpatterned areas of the optical film layer 131, based on the existing fabrication process of the back-end metal interconnect layer, have corresponding metal materials 135 deposited, enabling the unpatterned areas to function as etch stop layers or diffusion barrier layers, thus fulfilling the original function of the back-end metal interconnect layer. This allows the back-end metal interconnect layer to simultaneously achieve multiple different functions, effectively improving beam quality within a low-cost silicon grating coupler.

[0069] For example, the deposited metal material 135 may include various materials such as copper, aluminum, tungsten, and alloys. Corresponding vias can be etched on the deposited metal using standard processes, and then the pathways in the multilayer structure can be connected to complete the metal interconnection of BEOL.

[0070] Optionally, the optical film 131 is an etching stop layer used for metal interconnects (such as copper interconnects) in standard CMOS processes, and the corresponding optical pattern is obtained by etching on the basis of the original film layer.

[0071] Optionally, the optical waveguide 110 is provided with a light exit port through which the initial beam transmitted by the optical waveguide 110 is emitted. The pattern area of ​​the optical pattern on each optical film layer 131 is determined based on the light exit parameters of the light exit port. These light exit parameters may include the position, size, and exit angle of the light exit port. The optical waveguide 110 is provided with a light exit port to emit the initial beam transmitted by the light exit port. To achieve targeted transmission of the initial beam, the position and size of the pattern area containing the optical pattern on each optical film layer 131 in the stacked structure 130 can be determined based on the light exit parameters such as the position, size, and exit angle of the light exit port. This allows the optical pattern in each optical film layer 131 to effectively process the initial beam, thereby improving the effect of each optical film layer 131 in adjusting the optical characteristics of the beam and improving the beam quality of the final output adjusted beam.

[0072] For example, the shape of the optical pattern area can correspond to the shape of the light exit port. For instance, when the light exit port is circular, the optical pattern can also be set as a circular area. The area of ​​the optical pattern can be slightly larger than the size of the light exit port so that the optical pattern can completely cover the area of ​​the light exit port in the vertical direction 112. When the light exit angle of the light exit port is parallel to the vertical direction 112, multiple optical patterns can be located in an overlapping area in the vertical direction 112. When the light exit angle of the light exit port has an angle with the vertical direction 112, that is, when the light exit angle is tilted, multiple optical patterns can also be set in a relatively tilted position in the vertical direction 112 to adapt to the actual situation of the light exit port.

[0073] Optionally, in the vertical direction 112, the multilayer optical film layer 131 forms a multilayer diffractive lens, a metamaterial lens, or a cascaded metasurface based on multiple optical patterns. In the vertical direction 112, the multilayer optical film layer 131 can form various optical device structures with different functions, such as a multilayer diffractive lens, a metamaterial lens, or a cascaded metasurface, based on multiple optical patterns. Different functional optical device structures can be selected according to actual needs to adjust the optical characteristics of the initial beam accordingly.

[0074] For example, the number of optical film layers 131 can be adjusted, and the optical patterns on each optical film layer 131 can be designed in a coordinated manner to achieve optical device structures with different functions. This can simultaneously achieve beam steering (e.g., from 12 degrees to 0 degrees) and collimation (e.g., reducing the divergence angle from 10 degrees to 2 degrees), thereby optimizing the mode field diameter (MFD) from a divergent state to close to the MFD of the fiber 120, significantly improving coupling efficiency and alignment tolerance (especially the tolerance and angular tolerance on the Z-axis, i.e., the vertical direction 112).

[0075] For example, please refer to Figure 3 , Figure 3 This is a schematic diagram of an optical pattern provided in an embodiment of this application. The optical pattern may include various patterns of different shapes, such as concentric rings, nanopillars, and lines, obtained after specific patterning etching, so as to adjust the optical properties of the initial beam accordingly through different optical patterns.

[0076] For example, concentric rings can achieve lens functions, and nanopillars and lines can achieve metasurface functions.

[0077] For example, nanopillars may include subwavelength nanopillars or arrays of nanopores.

[0078] It should be noted that the multiple optical patterns on the multilayer optical film 131 are different. In order to achieve different functional structures, the functions of the multilayer optical film 131 may be different, and correspondingly, the multiple optical patterns set on the multilayer optical film 131 may also be different, so as to achieve a variety of different functions such as correcting the beam propagation direction, reducing the beam divergence angle, and reshaping the beam pattern profile.

[0079] For example, taking a three-layer optical film 131 as an example, the optical pattern on the first optical film 131 can be a line, the optical pattern on the second optical film 131 can be a nanopillar, and the optical pattern on the third optical film 131 can be a concentric circle.

[0080] Optionally, the optical film 131 may include a silicon-based nitride thin film layer. Without introducing new materials, it is possible to achieve optical beam characteristic adjustment functions, as well as corresponding etching stop and diffusion blocking functions, on the optical film 131.

[0081] For example, the silicon-based nitride thin film layer can be a thin film layer deposited based on Silicon Nitride material.

[0082] Please see Figure 4 , Figure 4 This is a flowchart illustrating a method for fabricating a stack structure according to an embodiment of this application. The method may include steps S210-S250.

[0083] Step S210: Deposit optical film material in the underlying structure.

[0084] The optical film layer can include materials that meet the requirements of thin film layer materials in the back-end process node stack, such as Silicon Nitride material, and can be fabricated based on standard CMOS processes.

[0085] Alternatively, the underlying structure can be obtained by depositing silica material.

[0086] Step S220: Photolithography and etching are performed on the optical film material based on the determined photomask to obtain an optical film with an optical pattern.

[0087] In this process, optical film materials can be photolithographically etched and etched based on a pre-determined photomask to obtain an optical film with an optical pattern.

[0088] Optionally, the etching method can be various etching methods such as reactive ion etching. First, the optical film material is photolithographically etched based on a photomask, and then the optical pattern is obtained through reactive ion etching.

[0089] Optionally, after obtaining the optical film, a corresponding metal material can be deposited on it, and corresponding metal vias can be etched for multilayer interconnection.

[0090] In step S230, an intermediate layer material is deposited on the optical film to obtain an intermediate layer structure, and the intermediate layer structure is polished.

[0091] In this process, an intermediate layer material can be deposited on the optical film layer to obtain an intermediate layer structure, and the intermediate layer structure can be polished to improve its flatness.

[0092] Alternatively, the polishing process may include chemical mechanical polishing.

[0093] Step S240: Continue to prepare an optical film layer on the intermediate layer structure, and continue to prepare an intermediate layer structure on the optical film layer until the top optical film layer is obtained.

[0094] In this process, optical films can be prepared on the intermediate layer structure, and intermediate layer structures can be prepared on the optical films. That is, optical films and intermediate layer structures can be prepared alternately until the last optical film layer, i.e., the top optical film layer, is prepared.

[0095] Step S250: Deposit the top structure on the top optical film layer.

[0096] Among them, a top-level structure can be deposited on the top-level film layer to obtain a complete stack structure.

[0097] Optionally, the top layer structure is a corresponding top passivation layer.

[0098] Optionally, the thickness, position, refractive index, etc. of each layer structure in the vertical direction can be set based on the corresponding process requirements and actual needs.

[0099] It should be noted that the prepared stack structure can correct the tilt angle of the initial beam emitted by the light wave to a direction angle that is basically perpendicular to the substrate surface. It can also reduce the divergence of the initial beam to improve the mode matching degree between the final output adjusted beam and the optical fiber. It can also simultaneously correct the propagation direction and reduce the divergence angle, thereby improving the coupling efficiency and alignment tolerance with the optical fiber.

[0100] exist Figure 4 In the embodiments described above, photolithography and etching processes can be added to the existing standard process flow of back-end metal interconnect layers to obtain corresponding optical patterns. The overall fabrication process of the stack structure is less difficult and more precise, making it easy to mass-produce.

[0101] Optionally, please refer to Figure 5 , Figure 5This is a flowchart illustrating another method for preparing a stack structure provided in an embodiment of this application. The method may further include steps S261-S263.

[0102] Step S261: Determine the beam parameters of the initial beam emitted by the light waveguide.

[0103] The beam parameters can include various beam-related parameters such as beam angle, optical field, and mode. The corresponding beam parameters can be determined based on the actual structure of the optical waveguide of the silicon grating coupler and the actual situation of the input optical signal.

[0104] Step S262: Based on the adjustment requirements of the initial beam, determine the target parameters of the output adjusted beam.

[0105] Specifically, based on the beam parameters of the emitted beam and the user's actual needs for the beam, the adjustment requirements for adjusting the initial beam can be determined, and based on the adjustment requirements, the target parameters of the required output adjusted beam can be determined.

[0106] Optionally, the target parameters may also include parameters such as the beam angle, light field, and mode of the beam.

[0107] Step S263: Based on the beam parameters and target parameters, and combined with the design structure of the stack structure, perform reverse design or iterative optimization to determine the photomask for each optical film layer in the stack structure.

[0108] In this system, the photomask corresponds to the optical pattern on the corresponding optical film layer. It can perform reverse design or iterative optimization based on beam parameters and target parameters to determine the photomask corresponding to the optical pattern of each optical film layer in the stacked structure that can adjust the initial beam into an adjusted beam. This allows for photolithography and etching processes based on the photomask, setting the corresponding optical pattern on the optical film layer.

[0109] Optionally, the iterative optimization algorithm can include various algorithms such as particle swarm optimization and genetic algorithm. It can take beam parameters as input data and target parameters as the required output data for optimization processing. The optimization objective includes maximizing the coupling efficiency of the adjusted beam fiber mode.

[0110] It should be noted that when determining multiple photomasks, multiple photomasks with multiple layers of optical films can be synergistically optimized to obtain multiple optical patterns of the final overall stacked structure.

[0111] Optionally, during the optimization process, the near-field emitted light field of the optical waveguide can be simulated based on the process parameters such as the thickness, position, and refractive index of each optical film layer. An optimization model can be established with the objective function of "maximum overlap integral with fiber mode" and the pattern of the multilayer optical film layers (e.g., the radius and width of the ring; the size and period of the nanopillar) as optimization variables. An optimization algorithm (such as reverse design, genetic algorithm, etc.) can be run to obtain the optimal multilayer pattern and generate the corresponding GDSII layout file as a photomask.

[0112] For example, the reverse engineering process may include: using the initial beam from the optical waveguide as the light source, discretizing the region of the multilayer optical film into a pixel grid, where each pixel has only two states: retaining the original refractive index (n=2), or being etched away to create an optical pattern, resulting in a change in refractive index (n=1.45). Optimization is performed using the adjoint method or other gradient descent algorithms (such as the Objective-First Algorithm), iteratively calculating the optimal arrangement of tens of thousands of pixels on the multilayer optical film until the objective function converges to its maximum value. The optimization algorithm ultimately generates a complex multilayer two-dimensional pattern (GDSII file). These patterns work together physically; taking a three-layer optical film as an example: SiN_1 (bottom layer) first interacts with the initial beam, beginning to correct its phase plane and angle. SiN_2 (middle layer) performs further phase compensation and focusing. SiN_3 (top layer) completes the final wavefront shaping, forming a collimated, Gaussian-like spot in the far field (at the fiber end face).

[0113] exist Figure 5 In the illustrated embodiment, the actual optical pattern required can be determined according to the actual beam adjustment needs, satisfying the adjustment requirements in various application scenarios.

[0114] For example, optionally, in a typical 90nm CMOS process flow, a BEOL stack sits atop a silicon waveguide layer (220nm thick). This BEOL stack is primarily composed of silicon oxide (refractive index 1.45), with embedded layers of metals (such as copper) and multiple silicon-based nitride thin films (refractive index 2.0). Assume the process provides three silicon-based nitride thin films as etch stop layers, located at different heights relative to the waveguide surface in the vertical direction, each with a thickness of 50nm. First, a standard one-dimensional grating coupler can be designed on the 220nm SOI top silicon layer. For example, a period Lambda = 630nm, a duty cycle FF = 0.5, and an etch depth d = 70nm. Using FDTD simulation software (such as Lumerical FDTD), its output light field at a wavelength of 1550nm is obtained. This light field has an output angle of approximately 12 degrees and a relatively large divergence angle. Within the BEOL (Optical Array Optical Cortex) above the base grating, three silicon nitride thin film layers are patterned. A moderate refractive index difference exists between these three silicon nitride thin film layers, sufficient for effective phase modulation of the optical field. To convert a 12-degree tilting divergent beam into a 0-degree collimated beam, the optical pattern within these three silicon nitride thin film layers can be designed as a cascaded set of diffractive lenses / metasurfaces. Design objective: Maximize the overlap integral between the final emitted beam and the fiber mode (Gaussian mode, MFD=10.4).

[0115] In summary, this application provides a silicon grating coupler, a method for fabricating a stacked structure, and an electronic device. By adjusting the optical characteristics of the initial beam through the stacked structure, the divergence angle and propagation direction of the initial beam can be controlled simultaneously, significantly improving coupling efficiency (e.g., from -3dB to below -1dB) and relaxing packaging alignment tolerances, thus significantly improving beam quality. Furthermore, the stacked structure of this application only involves patterning existing thin film layers in the BEOL (adding photolithography and etching steps), without involving new materials, non-standard deposition, or bonding steps, and is fully compatible with standard CMOS and silicon photonics manufacturing processes. Since it utilizes the stop layer inherent in the process, the material cost is zero. In some processes, the etching of the thin film layer may even be combined with the etching of metal vias, thereby achieving extremely low additional costs. The multilayer structure composed of multiple optical film layers in the stacked structure provides powerful light field manipulation capabilities, allowing for customized designs for different wavelengths and fiber types, offering high design flexibility and meeting the needs of various application scenarios.

[0116] In addition, the components in the various embodiments of this application can be integrated together to form an independent part, or each component can exist independently, or two or more components can be integrated to form an independent part.

[0117] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application. It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0118] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes 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.

[0119] It should be noted that, in this document, relational terms such as "first" and "second" are used merely 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, 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, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes said element.

Claims

1. A silicon grating coupler, characterized in that, The silicon grating coupler includes: an optical waveguide, an optical fiber, and a stacked structure; The stack structure is disposed between the optical waveguide and the optical fiber; In a direction perpendicular to the plane where the optical waveguide is placed, the stacked structure includes at least two optical film layers; optical patterns are etched on the optical film layers; wherein, the optical film layers adjust the optical characteristics of the initial beam emitted from the optical waveguide based on the optical patterns to obtain an adjusted beam, and transmit the adjusted beam to the optical fiber; The optical characteristics include at least one of the following: beam propagation direction, divergence angle, and pattern profile; The stack structure further includes: a bottom layer structure, an intermediate layer structure, and a top layer structure; in the vertical direction, the optical film layer is disposed between the bottom layer structure and the top layer structure; the intermediate layer structure is disposed between two adjacent optical film layers; wherein, the intermediate layer structure is used to physically isolate two adjacent optical film layers.

2. The silicon grating coupler according to claim 1, characterized in that, in, The intermediate layer structure is a transparent dielectric material.

3. The silicon grating coupler according to any one of claims 1-2, characterized in that, in, Metal material is deposited in the non-patterned areas of the optical film layer that do not have the optical pattern. The non-patterned areas are used as etching stop layers or diffusion barrier layers.

4. The silicon grating coupler according to any one of claims 1-2, characterized in that, The optical waveguide is provided with a light outlet, through which the initial beam transmitted by the optical waveguide is emitted. The pattern area of ​​the optical pattern on each optical film layer is determined based on the light emission parameters of the light emission port; wherein, the light emission parameters include: the position, size and light emission angle of the light emission port.

5. The silicon grating coupler according to any one of claims 1-2, characterized in that, In the vertical direction, the multiple optical film layers form a multilayer diffractive lens, a metamaterial lens, or a cascaded metasurface based on multiple optical patterns.

6. The silicon grating coupler according to any one of claims 1-2, characterized in that, in, The optical pattern includes at least one of the following: concentric rings, nanopillars, and lines.

7. The silicon grating coupler according to any one of claims 1-2, characterized in that, in, The multiple optical patterns on the multilayer optical film are different.

8. The silicon grating coupler according to any one of claims 1-2, characterized in that, in, The optical film layer includes a silicon-based nitride thin film layer.

9. A method for fabricating a stack structure, characterized in that, The method prepares the stacked structure of the silicon grating coupler according to any one of claims 1-8, the method comprising: Deposit optical film materials in the underlying structure; The optical film material is photolithographically etched and etched based on a defined photomask to obtain an optical film with an optical pattern. An intermediate layer material is deposited on the optical film to obtain an intermediate layer structure, and the intermediate layer structure is polished. The optical film layer is further fabricated on the intermediate layer structure, and the intermediate layer structure is further fabricated on the optical film layer until the top optical film layer is obtained; A top-layer structure is deposited on the top-layer optical film.

10. The method according to claim 9, characterized in that, in, The method for determining the photomask includes: Determine the beam parameters of the initial beam emitted by the light waveguide; wherein, the beam parameters include beam angle, light field, and mode; Based on the adjustment requirements of the initial beam, the target parameters of the output adjusted beam are determined; Based on the beam parameters and the target parameters, and in conjunction with the design structure of the stack structure, reverse design or iterative optimization is performed to determine the photomask for each optical film layer in the stack structure; wherein the photomask corresponds to the optical pattern on the corresponding optical film layer.

11. An electronic device, characterized in that, The electronic device includes the silicon grating coupler as described in any one of claims 1-8.

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