Grating coupling structure and silicon optical chip

Abstract

The application relates to a grating coupling structure and a silicon optical chip, wherein the grating coupling structure comprises: a waveguide layer provided with a grating coupler; the grating coupler is formed with a first coupling end face; the first coupling end face is used for coupling connection with an external optical device; the first coupling end face is parallel to the waveguide layer; a cladding layer covers the waveguide layer; a metal interconnection layer is arranged on a side surface of the cladding layer away from the waveguide layer; the metal interconnection layer comprises a first metal reflection region; a vertical projection of the first metal reflection region on the waveguide layer at least partially overlaps the grating coupler; and the first metal reflection region is used for reflecting diffracted light emitted by the grating coupler to the first metal reflection region. The grating coupling structure can reduce the coupling loss of the grating coupler, improve the yield of the grating coupling structure in mass production, and reduce the manufacturing cost.

Description

Technical Field

[0001] This application relates to the field of optoelectronic chips, and in particular to a grating coupling structure and a silicon photonic chip. Background Technology

[0002] In the field of optoelectronic chip technology, co-packaged optics (CPO) is mainly used to integrate photonic integrated circuits and electronic integrated circuits on the same substrate. By shortening the interconnect distance, it achieves high bandwidth density and low power consumption, and is a core technology direction for next-generation high-speed optical interconnects. In the existing CPO architecture, grating couplers have advantages such as their coupling end face being able to be set at any position on the chip surface and large alignment tolerance, and have been widely used. However, in practical applications, grating couplers generate diffracted light in multiple directions, resulting in high coupling loss. To address this, some related technologies deposit an additional metal reflective film on the surface of the optical chip. The metal reflective film can reflect the diffracted light generated by the grating coupler, returning the diffracted light to the optical transmission path and reducing coupling loss. However, this method requires an additional coating process after chip fabrication, which not only increases the number of process steps and costs, but may also lead to problems such as contamination of the chip surface and damage to active devices during the coating process, thereby reducing chip yield and increasing manufacturing costs. Summary of the Invention

[0003] Based on this, this application provides a grating coupling structure that can reduce the coupling loss of the grating coupler, improve the mass production yield of the grating coupling structure, and reduce manufacturing costs.

[0004] On one hand, this application provides a grating coupling structure, including: a waveguide layer with a grating coupler; the grating coupler having a first coupling end face; the first coupling end face being used for coupling connection with an external optical device; the first coupling end face being parallel to the waveguide layer; a cladding layer covering the waveguide layer; a metal interconnect layer disposed on the side surface of the cladding layer away from the waveguide layer; the metal interconnect layer including a first metal reflection region; the vertical projection of the first metal reflection region on the waveguide layer at least partially coinciding with the grating coupler; the first metal reflection region being used to reflect diffracted light emitted by the grating coupler towards the first metal reflection region.

[0005] Optionally, the size of the first metal reflective region is configured to cover the light spot diffracted by the grating coupler to the first metal reflective region.

[0006] Optionally, the grating coupling structure further includes: a semiconductor substrate disposed on the side of the waveguide layer away from the metal interconnect layer, and a first coupling end face located on the side surface of the semiconductor substrate away from the waveguide layer; wherein the semiconductor substrate is thinned.

[0007] Optionally, the thickness of the semiconductor substrate falls between 50 micrometers and 500 micrometers.

[0008] Optionally, a first window is provided on the semiconductor substrate at the position corresponding to the grating coupler; the first window penetrates the semiconductor substrate; the first window is filled with a transparent medium; the refractive index of the transparent medium is lower than the refractive index of the semiconductor substrate; wherein, the first window is configured to cover the waveguide core layer of the external optical device when the first coupling end face is coupled to the external optical device.

[0009] Optionally, the grating coupling structure further includes: a second metal reflective region disposed between the semiconductor substrate and the cladding; the second metal reflective region is penetrated by the first window; the vertical projection of the second metal reflective region on the waveguide layer at least partially coincides with the grating coupler; the second metal reflective region is used to reflect the diffracted light emitted by the grating coupler toward the second metal reflective region.

[0010] Optionally, the thickness of the first metal reflective region is greater than or equal to 50 nanometers; and / or, the thickness of the second metal reflective region is greater than or equal to 50 nanometers.

[0011] Optionally, the grating coupling structure further includes: a filling layer disposed on the side of the first metal reflection region away from the cladding; a first coupling end face located on the surface of the filling layer away from the first metal reflection region; a second window provided in the filling layer corresponding to the position of the grating coupler, the second window penetrating the filling layer and the first metal reflection region; the second window being filled with a transparent medium; the refractive index of the transparent medium being lower than the refractive index of the filling layer; wherein, the second window is configured to cover the waveguide core layer of the external optical device when the first coupling end face is coupled to the external optical device.

[0012] Optionally, the grating coupling structure further includes: a third metal reflective region disposed on the surface of the cladding away from the first metal reflective region; the vertical projection of the third metal reflective region on the waveguide layer at least partially coincides with the grating coupler; the third metal reflective region is used to reflect the diffracted light emitted by the grating coupler toward the third metal reflective region.

[0013] Optionally, the grating coupling structure further includes: an optical antireflection film disposed on and covering the first coupling end face, used to reduce light reflection at the first coupling end face.

[0014] On the other hand, this application also provides a silicon photonic chip, including the aforementioned grating coupling structure.

[0015] The embodiments provided in this application, by providing a first metal reflective region on the metal interconnect layer, can reflect the diffracted light emitted from the grating coupler towards the first metal reflective region, thereby returning the diffracted light to the optical transmission path and improving the coupling efficiency of the grating coupling structure. Simultaneously, since the metal interconnect layer is an existing metal interconnect layer in the standard CMOS process flow, no additional coating process is required, thus avoiding the risks of chip contamination and device damage caused by additional coating, improving the mass production yield of the grating coupling structure, and reducing manufacturing costs. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a grating coupling structure provided in one embodiment of this application;

[0017] Figure 2 This is a schematic diagram of a grating coupling structure provided in another embodiment of this application;

[0018] Figure 3 This is a schematic diagram of the grating coupling structure provided in another embodiment of this application;

[0019] Figure 4 This is a schematic diagram of a grating coupling structure provided in another embodiment of this application.

[0020] Explanation of reference numerals in the attached figures

[0021] 100 / 200 / 300 / 400, Grating coupling structure; 110, Waveguide layer; 111, Grating coupler; 112, First coupling end face; 120, Cladding layer; 130, Metal interconnect layer; 131, First metal reflection region; 140, Semiconductor substrate; 141, First window; 150, Second metal reflection region; 160, Filling layer; 161, Second window; 170, Third metal reflection region; 180, Optical antireflection coating; 500, External optical device; 510, Waveguide core layer. Detailed Implementation

[0022] To make the technical solution and beneficial effects of this application more apparent and understandable, a detailed description is provided below by listing specific embodiments. The accompanying drawings are not necessarily drawn to scale, and local features may be enlarged or reduced to more clearly show the details of the local features; unless otherwise defined, the technical and scientific terms used herein have the same meanings as those in the technical field to which this application pertains.

[0023] refer to Figure 1 Some embodiments of this application provide a grating coupling structure 100, which includes a waveguide layer 110, a cladding layer 120, and a metal interconnect layer 130.

[0024] The waveguide layer 110 includes a grating coupler 111. The grating coupler 111 has a first coupling end face 112. The first coupling end face 112 is used for coupling connection with an external optical device 500. The first coupling end face 112 is parallel to the waveguide layer 110. A cladding layer 120 covers the waveguide layer 110. A metal interconnect layer 130 is disposed on the surface of the cladding layer 120 away from the waveguide layer 110. The metal interconnect layer 130 includes a first metal reflective region 131. The vertical projection of the first metal reflective region 131 onto the waveguide layer 110 at least partially coincides with the grating coupler 111. The first metal reflective region 131 is used to reflect diffracted light emitted from the grating coupler 111 towards the first metal reflective region 131.

[0025] It is understood that the first coupling end face 112 refers to the physical surface of the grating coupling structure 100 used for optical coupling with the external optical device 500. The metal interconnect layer 130 is a layered structure used in the standard CMOS chip manufacturing process to realize the electrical interconnection of internal devices of the photonic integrated circuit chip. The first metal reflective region 131 is a block of metal in the metal interconnect layer 130, which is patterned and placed at the corresponding position of the grating coupler 111. The external optical device 500 refers to various devices that are optically coupled with the grating coupling structure 100, such as a single optical fiber or an optical fiber array composed of multiple optical fibers.

[0026] The aforementioned grating coupling structure 100 improves coupling efficiency by providing a first metal reflective region 131 on the metal interconnect layer 130. This first metal reflective region 131 reflects diffracted light emitted from the grating coupler 111 towards the first metal reflective region 131, returning the diffracted light to the optical transmission path. Simultaneously, since the metal interconnect layer 130 is constructed from existing metal interconnect layers in standard CMOS processes, no additional coating process is required, thus avoiding the risks of chip contamination and device damage associated with additional coating. This improves the mass production yield of the grating coupling structure 100 and reduces manufacturing costs.

[0027] Specifically, when the grating coupling structure 100 operates in emission mode, the optical signal from the optical chip is transmitted to the grating coupler 111 via the optical waveguide within the waveguide layer 110. Through grating diffraction, the signal is transmitted in two directions: towards the first coupling end face 112 and away from it. A portion of the diffracted light towards the first coupling end face 112 is transmitted to the external optical device 500, completing the optical signal transmission. At this time, the optical transmission path includes a portion of the optical path from the grating coupler 111 to the first coupling end face 112. Since the first coupling end face 112 is parallel to the waveguide layer 110, the main direction of the diffracted light is perpendicular to the waveguide layer 110. Because the vertical projected area of ​​the first metal reflection region 131 at least partially overlaps with the grating coupler 111, at least a portion of the diffracted light transmitted away from the first coupling end face 112 is transmitted to the first metal reflection region 131. Due to the high reflectivity of the metal material (usually copper), the first metal reflection region 131 can reflect this portion of the diffracted light towards the first coupling end face 112, thereby enabling constructive interference with the diffracted light towards the first coupling end face 112. This improves the diffraction efficiency of the grating coupler 111 and reduces its coupling loss. This achieves the effect of returning the diffracted light to the optical transmission path, thus improving the coupling efficiency of the grating coupling structure 100.

[0028] When the grating coupling structure 100 operates in incident mode, the optical signal from the external optical device 500 is transmitted to the grating coupler 111 through the first coupling end face 112. The grating coupler 111 forms a beam through diffraction coupling, which is then transmitted through the optical waveguide in the waveguide layer 110 until it reaches the optical chip, completing the optical signal transmission. At this time, the optical transmission path includes a portion of the optical path pointing from the first coupling end face 112 to the grating coupler 111. During this process, the grating coupler 111 also generates diffracted light in two directions: towards the first coupling end face 112 and away from it. The first metal reflection region 131 can reflect a portion of the diffracted light transmitted to the first metal reflection region 131 towards the waveguide layer 110, allowing the grating coupler 111 to couple this portion of the diffracted light, thereby reducing the coupling loss of the grating coupler 111. Thus, the effect of returning the diffracted light to the optical transmission path is achieved, improving the coupling efficiency of the grating coupling structure 100.

[0029] It should be noted that the grating coupling structure of this application can be applied to optical chips with various material substrates, such as SOI (silicon-on-insulator), SiN (silicon nitride), and TFLN (thin-film lithium niobate) optical chips.

[0030] refer to Figure 1 In this embodiment, the size of the first metal reflection region 131 is configured to cover the light spot diffracted by the grating coupler 111 to the first metal reflection region 131.

[0031] Specifically, during the diffraction process of the grating coupler 111, the diffracted light diffuses along its propagation path. When it passes through the cladding 120 and reaches the metal interconnect layer 130, the size of the diffracted light spot is larger than the physical size of the grating coupler 111 itself. The first metal reflective region 131 is mainly used to reflect the diffracted light back into the light propagation path. If the size of the first metal reflective region 131 is too small, it cannot completely cover the light spot, resulting in some diffracted light not being effectively recovered, causing energy waste.

[0032] Therefore, in the grating coupling structure 100 of the above embodiment, the size of the first metal reflection region 131 is configured to cover the light spot diffracted by the grating coupler 111 to the first metal reflection region 131, so as to ensure that the upward diffracted light energy is fully received by the first metal reflection region 131 and reflected back into the light transmission path, thereby improving the recovery efficiency of diffracted light, thereby improving the diffraction efficiency of the grating coupler 111 and reducing the coupling loss of the grating coupling structure 100.

[0033] Furthermore, it should be noted that the light spot diffracted by the grating coupler 111 to the first metal reflective region 131 is also affected by the vertical distance between the grating coupler 111 and the first metal reflective region 131. The larger this vertical distance, the longer the transmission distance of the diffracted light, and the larger the resulting light spot. Therefore, when setting the size of the first metal reflective region 131, this vertical distance can be determined first, and the light spot size can be determined through pre-calculation or simulation calibration, and then the size of the first metal reflective region 131 can be configured to cover the light spot.

[0034] refer to Figure 1 In this embodiment, the grating coupling structure 100 further includes a semiconductor substrate 140 disposed on the side of the waveguide layer 110 away from the metal interconnect layer 130, and a first coupling end face 112 located on the surface of the semiconductor substrate 140 away from the waveguide layer 110. The semiconductor substrate 140 is thinned.

[0035] Specifically, in conventional optical chip manufacturing processes, semiconductor substrates have a significant thickness, typically several hundred micrometers. In this case, if the first coupling end face is located on the surface of the semiconductor substrate, in the emission mode, the diffracted light from the grating coupler towards the substrate needs to pass through the thick substrate to reach the first coupling end face. Due to the long propagation path, the mode diffusion effect is significant, easily leading to a mismatch between the mode size reaching the first coupling end face 112 and the mode field of the external optical device, thus generating additional coupling loss. To compensate for the coupling loss caused by mode diffusion, existing technologies typically require the use of chirped collimating gratings with gradient period and gradient duty cycle as grating couplers, which increases the complexity of grating design and manufacturing difficulty.

[0036] In this embodiment, the grating coupling structure 100 thins the semiconductor substrate 140, which shortens the light propagation path in the substrate and suppresses mode diffusion. This ensures that the mode size of the grating diffracted light matches the mode field of the external optical device 500 when it reaches the first coupling end face 112, guaranteeing high coupling efficiency. Furthermore, the grating coupling structure 100 eliminates the need for complex gradient chirped structures to compensate for mode diffusion. For example, a conventional uniform grating or a weakly apodized grating can be used as the grating coupler 111. This significantly reduces the design workload of the grating coupler 111 and avoids the stringent requirements of gradient chirped structures on photolithography and etching processes. The process tolerance is significantly widened, thereby improving the mass production yield of the grating coupling structure 100 and reducing its manufacturing cost.

[0037] Optionally, in the grating coupling structure 100 of this embodiment, the thickness of the semiconductor substrate 140 falls between 50 micrometers and 500 micrometers. Setting the thickness of the semiconductor substrate 140 to be greater than or equal to 50 micrometers ensures that the semiconductor substrate 140 has sufficient mechanical strength, reducing the risk of breakage, warping, and other failures during the packaging process. Simultaneously, it also makes the thinning step of the semiconductor substrate 140 relatively easier, thereby improving the mass production yield of the grating coupling structure 100.

[0038] Furthermore, setting the thickness of the semiconductor substrate 140 to less than or equal to 500 micrometers can make the effect of suppressing the diffusion of the thinning step more obvious, thereby improving the coupling efficiency of the grating coupling structure 100.

[0039] refer to Figure 1 In this embodiment, the grating coupling structure 100 further includes an optical antireflection film 180, disposed on and covering the first coupling end face 112, for reducing light reflection at the first coupling end face 112. The optical antireflection film 180 can reduce interface reflection generated at the first coupling end face 112, thereby improving the coupling efficiency of the grating coupling structure 100.

[0040] refer to Figure 2 Some embodiments of this application also provide another grating coupling structure 200. Unlike the aforementioned grating coupling structure 100, in this grating coupling structure 200, a first window 141 is provided on the semiconductor substrate 140 corresponding to the position of the grating coupler 111. The first window 141 penetrates the semiconductor substrate 140. The first window 141 is filled with a transparent medium. The refractive index of the transparent medium is lower than the refractive index of the semiconductor substrate 140. The first window 141 is configured to cover the waveguide core layer 510 of the external optical device 500 when the first coupling end face 112 is coupled to it.

[0041] It is understood that the first window 141 refers to the opening region penetrating the semiconductor substrate 140, which can be formed using a through-silicon via (TSV) process. The first window 141 is filled with a transparent medium, which is a light-transmitting material with a refractive index lower than that of the semiconductor substrate 140. As a specific example, when the semiconductor substrate 140 is silicon (refractive index approximately 3.5), the transparent medium can be a low-refractive-index material such as silicon dioxide (refractive index approximately 1.45) or silicon nitride (refractive index approximately 2.0).

[0042] Specifically, during the transmission of optical signals through the semiconductor substrate 140, the high refractive index of the semiconductor substrate 140 causes mode diffusion, making it difficult for the mode size of the first coupling end face 112 to match the mode field of the external optical device 500. Therefore, this embodiment provides a first window 141 penetrating the semiconductor substrate 140 and fills the first window 141 with a low-refractive-index transparent medium. The optical signal can be transmitted between the first coupling end face 112 and the grating coupler 111 through the first window 141 without being affected by the high-refractive-index substrate material, thereby eliminating mode diffusion within the semiconductor substrate 140 and improving coupling efficiency.

[0043] Furthermore, in the aforementioned grating coupling structure 200, the size of the first window 141 is configured such that when the first coupling end face 112 is coupled to the external optical device 500, it can cover the waveguide core layer 510 of the external optical device 500. This can prevent some optical signals from being blocked or absorbed by the substrate material due to insufficient size of the first window 141, ensuring that the optical signal can be transmitted completely through the first window 141, thereby improving the coupling efficiency of the grating coupling structure 200.

[0044] refer to Figure 3 Some embodiments of this application also provide another grating coupling structure 300, which, unlike the aforementioned grating coupling structure 200, further includes a second metal reflective region 150 disposed between the semiconductor substrate 140 and the cladding layer 120. The second metal reflective region 150 is penetrated by a first window 141. The vertical projection of the second metal reflective region 150 onto the waveguide layer 110 at least partially coincides with the grating coupler 111. The second metal reflective region 150 is used to reflect diffracted light emitted from the grating coupler 111 towards the second metal reflective region 150.

[0045] Specifically, in the grating coupling structure 300, of the diffracted light from the grating coupler 111 towards the semiconductor substrate 140, a portion of the diffracted light directly targets the first window 141 region and is transmitted to the first coupling end face 112 via the low-refractive-index transparent medium within the window. Another portion of the diffracted light targets the substrate region surrounding the first window 141, propagating into the substrate region and causing coupling loss. In this embodiment, by providing a second metal reflective region 150 between the substrate and the cladding 120 around the first window 141, the diffracted light targeting the substrate region around the first window 141 is reflected back to the waveguide layer 110 by the second metal reflective region 150, thus recovering this portion of the diffracted light and further improving the coupling efficiency of the grating coupling structure 300.

[0046] Furthermore, the second metal reflective region 150 is a block metal structure disposed between the semiconductor substrate 140 and the cladding 120, and has a hole-like structure formed by the first window 141 penetrating through it. This ensures that the second metal reflective region 150 does not block the light signal, and that the light signal can be transmitted through the first window 141.

[0047] Optionally, in this embodiment, the thickness of the first metal reflective region 131 can be set to be greater than or equal to 50 nanometers. This allows the first metal reflective region 131 to have better light reflection performance to reflect diffracted light.

[0048] Similarly, in this embodiment, the thickness of the second metal reflective region 150 can also be set to be greater than or equal to 50 nanometers to give it better light reflection performance.

[0049] refer to Figure 4 Some embodiments of this application also provide another grating coupling structure 400, which, unlike the aforementioned grating coupling structure 100, further includes a filling layer 160. The filling layer 160 is disposed on the side of the first metal reflection region 131 away from the cladding layer 120. The first coupling end face 112 is located on the surface of the filling layer 160 away from the first metal reflection region 131. The filling layer 160 has a second window 161 at the position corresponding to the grating coupler 111, and the second window 161 penetrates the filling layer 160 and the first metal reflection region 131. The second window 161 is filled with a transparent medium. The refractive index of the transparent medium is lower than that of the filling layer 160. The second window 161 is configured to cover the waveguide core layer 510 of the external optical device 500 when the first coupling end face 112 is coupled to the external optical device 500.

[0050] Specifically, the first coupling end face 112 can be disposed on the surface of the filling layer 160 away from the first metal reflection region 131, so that the external optical device 500 can be coupled to the grating coupler 111 from the filling layer 160 side. In this case, a second window 161 can be provided through the filling layer 160 and the first metal reflection region 131, so that the optical signal can be transmitted between the grating coupler 111 and the first coupling end face 112 through the second window 161. At the same time, the first metal reflection region 131 can reflect the diffracted light directed towards the filling layer 160 region adjacent to the second window 161 back to the direction of the waveguide layer 110, thereby improving the coupling efficiency. The specific principle is similar to that of the first window 141 mentioned above, and will not be repeated here. Thus, the grating coupling structure 400 can achieve flexible placement of the first coupling end face 112 while maintaining the advantages of the multiplexed metal interconnect layer 130, thereby improving the flexibility of the grating coupling structure 400.

[0051] In addition, the low-refractive-index transparent medium filling the second window 161 can reduce the speckle diffusion generated when the light signal is transmitted in the filling layer 160. The principle is similar to the principle of the transparent medium in the first window 141 suppressing speckle diffusion, and will not be repeated here.

[0052] Further reference Figure 4 The grating coupling structure 400 further includes a third metallic reflective region 170, disposed on the surface of the cladding 120 away from the first metallic reflective region 131. The vertical projection of the third metallic reflective region 170 onto the waveguide layer 110 at least partially coincides with the grating coupler 111. The third metallic reflective region 170 is used to reflect diffracted light emitted from the grating coupler 111 towards the third metallic reflective region 170. The third metallic reflective region 170 can further improve the coupling efficiency, and its specific principle is similar to that of the first metallic reflective region 131 in the aforementioned grating coupling structure 100, and will not be elaborated here.

[0053] Based on the aforementioned embodiments of the grating coupling structure, some embodiments of this application also provide a silicon photonics chip, including the aforementioned grating coupling structure.

[0054] The aforementioned silicon photonics chip improves the coupling efficiency of the grating coupling structure by setting a first metal reflective region on the metal interconnect layer. This first metal reflective region reflects the diffracted light emitted from the grating coupler towards it, returning the diffracted light to the optical transmission path. Simultaneously, since the metal interconnect layer is already present in the standard CMOS process flow, no additional coating process is required. This avoids the risks of chip contamination and device damage associated with additional coating, improving the mass production yield of the grating coupling structure and reducing manufacturing costs.

[0055] In this application, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "height," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the purpose of simplifying the description of this application and do not indicate that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. In other words, they should not be construed as limitations on this application.

[0056] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating the relative importance of the indicated features or the number of indicated technical features. Therefore, a feature specified as "first" or "second" may explicitly include at least one of those features. In this application, "multiple" means at least two, such as two, three, etc.; "several" means at least one, such as one, two, three, etc., unless otherwise explicitly specified.

[0057] In this application, unless otherwise expressly defined, the terms "installation," "connection," "linking," "fixing," "setting," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can also refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0058] In this application, unless otherwise expressly defined, the terms "above," "on top of," "over," "above," "below," "below," "below," or "below" for "first feature over second feature" can refer to the first and second features being in direct contact, or to the first and second features being in indirect contact through an intermediate medium. Furthermore, "above," "over," and "below" for "first feature over second feature" can mean the first feature is directly above or diagonally above the second feature, or simply indicates that the horizontal height of the first feature is higher than the horizontal height of the second feature. Similarly, "below," "below," and "below" for "first feature over second feature" can mean the first feature is directly below or diagonally below the second feature, or simply indicates that the horizontal height of the first feature is lower than the horizontal height of the second feature.

[0059] It should be understood that the above embodiments are exemplary and are not intended to include all possible embodiments covered by the claims. Various modifications and changes can be made to the above embodiments without departing from the scope of this disclosure. Similarly, the various technical features of the above embodiments can be arbitrarily combined to form other embodiments of this application that may not be explicitly described. Therefore, the above embodiments only illustrate several embodiments of this application and do not limit the scope of protection of this patent application.

Claims

1. A grating coupling structure, characterized in that, include: A waveguide layer is provided with a grating coupler; the grating coupler has a first coupling end face; the first coupling end face is used for coupling connection with external optical devices; the first coupling end face is parallel to the waveguide layer; Cladding, covering the waveguide layer; A metal interconnect layer is disposed on the surface of the cladding away from the waveguide layer; the metal interconnect layer includes a first metal reflective region; the vertical projection of the first metal reflective region on the waveguide layer at least partially coincides with the grating coupler; the first metal reflective region is used to reflect the diffracted light emitted by the grating coupler toward the first metal reflective region.

2. The grating coupling structure according to claim 1, characterized in that, The size of the first metal reflective region is configured to cover the light spot diffracted by the grating coupler to the first metal reflective region.

3. The grating coupling structure according to claim 1, characterized in that, Also includes: A semiconductor substrate is disposed on the side of the waveguide layer away from the metal interconnect layer, and the first coupling end face is located on the surface of the semiconductor substrate away from the waveguide layer; wherein the semiconductor substrate is thinned.

4. The grating coupling structure according to claim 3, characterized in that, The thickness of the semiconductor substrate is between 50 micrometers and 500 micrometers.

5. The grating coupling structure according to claim 3, characterized in that, The semiconductor substrate has a first window corresponding to the position of the grating coupler; the first window penetrates the semiconductor substrate; the first window is filled with a transparent medium; the refractive index of the transparent medium is lower than the refractive index of the semiconductor substrate; The first window is configured to cover the waveguide core layer of the external optical device when the first coupling end face is coupled to the external optical device.

6. The grating coupling structure according to claim 5, characterized in that, Also includes: A second metal reflective region is disposed between the semiconductor substrate and the cladding layer; the second metal reflective region is penetrated by the first window; The vertical projection of the second metal reflective region onto the waveguide layer at least partially coincides with the grating coupler; the second metal reflective region is used to reflect the diffracted light emitted by the grating coupler toward the second metal reflective region.

7. The grating coupling structure according to claim 6, characterized in that, The thickness of the first metallic reflective region is greater than or equal to 50 nanometers; And / or, the thickness of the second metal reflective region is greater than or equal to 50 nanometers.

8. The grating coupling structure according to claim 1, characterized in that, Also includes: A filling layer is disposed on the side of the first metal reflective region away from the cladding layer; The first coupling end face is located on the side surface of the filling layer away from the first metal reflection area; the filling layer has a second window corresponding to the position of the grating coupler, the second window penetrating the filling layer and the first metal reflection area; the second window is filled with a transparent medium; the refractive index of the transparent medium is lower than the refractive index of the filling layer; wherein, the second window is configured to cover the waveguide core layer of the external optical device when the first coupling end face is coupled to the external optical device.

9. The grating coupling structure according to claim 8, characterized in that, Also includes: The third metal reflective region is disposed on the surface of the cladding that is away from the first metal reflective region; The vertical projection of the third metal reflection region on the waveguide layer at least partially coincides with the grating coupler; the third metal reflection region is used to reflect the diffracted light emitted by the grating coupler toward the third metal reflection region.

10. The grating coupling structure according to claim 1, characterized in that, Also includes: An optical antireflective coating is disposed on and covers the first coupling end face to reduce light reflection at the first coupling end face.

11. A silicon photonics chip, characterized in that, Includes the grating coupling structure according to any one of claims 1-10.

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