Interlayer coupler and forming method thereof
By designing a grating structure with complementary light exit and incident angles, the problem of low coupling efficiency of existing interlayer couplers is solved, and efficient optical mode field matching and three-dimensional integration are achieved.
Patent Information
- Application Number
- CN202411917562.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2025-03-18
AI Technical Summary
The coupling efficiency of existing interlayer couplers is relatively low, especially in the grating-based implementation method, and its coupling efficiency can only reach 50% to 60%.
By designing the first and second grating structures, the light exit angle and light incident angle are complementary, so as to achieve the matching of the optical mode field of the upper and lower grating structures as much as possible, and the coupling efficiency of the inter-layer coupler is improved.
By rationally designing the grating structure, the coupling efficiency of the inter-layer coupler is improved, the loss during optical transmission is reduced, and the three-dimensional integration of any material is possible.
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Figure CN119644509A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the field of optical communication technology, and in particular to an interlayer coupler and a method for forming the same. Background Art
[0002] As Moore's Law approaches the physical limit, the size of semiconductor microelectronic chips has approached the theoretical limit. Optoelectronic integration solutions with advantages such as high bandwidth, low loss, and small size have become an important trend for future development. At present, lasers, modulators, photodetectors, and various passive photonic devices can be compactly integrated on the same substrate, but integrating each device two-dimensionally on the same plane greatly limits the flexibility and integration of the overall chip, so three-dimensional photonic integrated structures have emerged.
[0003] Interlayer couplers can realize the three-dimensional free transmission of light between different planes, making it possible to realize the optical interconnection between devices on different planes in a three-dimensional photonic integrated structure. With the rapid development of optical communication and photonic integration technology, efficient optical coupling technology has become a key link in system design, which puts forward high requirements on the coupling efficiency of interlayer couplers. Summary of the invention
[0004] The technical problem solved by the present disclosure is how to improve the coupling efficiency of the interlayer coupler.
[0005] To solve the above technical problems, an embodiment of the present disclosure provides an interlayer coupler, comprising: a first waveguide layer, formed with a first grating structure, the first grating structure being a one-dimensional periodic grating; a second waveguide layer, located above the first waveguide layer and formed with a second grating structure, the second grating structure being a one-dimensional periodic grating; wherein the light exit angle of one of the first grating structure and the second grating structure is complementary to the light incident angle of the other one.
[0006] Optionally, an extension direction of the outgoing light of one of the first grating structure and the second grating structure is parallel to an extension direction of the incident light of the other one of them.
[0007] Optionally, for any one of the first grating structure and the second grating structure, the grating parameters of the grating structure are constant; and the correlation between the grating parameters of the first grating structure and the grating parameters of the second grating structure is determined according to materials of the first grating structure and the second grating structure.
[0008] Optionally, the first grating structure and the second grating structure are made of the same material, and the grating parameters of the first grating structure and the grating parameters of the second grating structure satisfy at least one of the following conditions: a period of the first grating structure is greater than a period of the second grating structure; a height of the first grating structure is equal to a height of the second grating structure; an etching depth of the first grating structure is equal to an etching depth of the second grating structure; and the first grating structure and the second grating structure have the same duty cycle.
[0009] Optionally, the materials of the first grating structure and the second grating structure are both silicon.
[0010] Optionally, the materials of the first grating structure and the second grating structure are different, and the grating parameters of the first grating structure and the grating parameters of the second grating structure satisfy at least one of the following conditions: the period of the first grating structure is greater than the period of the second grating structure; the height of the first grating structure is greater than the height of the second grating structure; the etching depth of the first grating structure is greater than the etching depth of the second grating structure; the duty cycle of the first grating structure is less than the duty cycle of the second grating structure.
[0011] Optionally, the first grating structure is made of silicon nitride, and the second grating structure is made of silicon.
[0012] Optionally, one of the first waveguide layer and the second waveguide layer is used to receive incident light, and the other one is used to emit outgoing light, and a transmission direction of the incident light is opposite to a transmission direction of the outgoing light.
[0013] Optionally, the first grating structure and / or the second grating structure is a rectangular grating.
[0014] Optionally, the lengths of the first grating structure and the second grating structure are consistent.
[0015] Optionally, the interlayer coupler further includes: a first reflector layer located on a side of the first waveguide layer away from the second waveguide layer; and a second reflector layer located on a side of the second waveguide layer away from the first waveguide layer.
[0016] Optionally, the first waveguide layer and the second waveguide layer are respectively selected from a candidate library, the candidate library includes a plurality of standard waveguide layers, the materials and / or grating parameters of the grating structures formed in different standard waveguide layers are at least partially different, and each of the standard waveguide layers has the same optical mode field.
[0017] To solve the above technical problems, an embodiment of the present disclosure further provides a method for forming an interlayer coupler, comprising: providing a first wafer, wherein the first wafer has a first surface and a second surface opposite to each other; preparing a first grating structure on the first surface of the first wafer to obtain a first waveguide layer, wherein the first grating structure is a one-dimensional periodic grating; preparing a second grating structure on the second surface of the first wafer to obtain a second waveguide layer, wherein the second grating structure is a one-dimensional periodic grating, wherein a light exit angle of one of the first grating structure and the second grating structure is complementary to a light incident angle of the other one of them.
[0018] Optionally, after the first waveguide layer is prepared, the forming method further includes: depositing a first isolation layer on the surface of the first waveguide layer; and preparing a first reflector layer on the surface of the first isolation layer.
[0019] Optionally, preparing a second grating structure on the second surface of the first wafer to obtain a second waveguide layer includes: inverting the first wafer on which the first waveguide layer is prepared to bond to a semiconductor substrate, wherein the second surface of the inverted first wafer faces upward; and preparing a second grating structure on the second surface of the first wafer to obtain a second waveguide layer.
[0020] Optionally, after the second waveguide layer is prepared, the forming method further includes: depositing a second isolation layer on the surface of the second waveguide layer; and preparing a second reflector layer on the surface of the second isolation layer.
[0021] Compared with the prior art, the technical solution of the embodiment of the present disclosure has the following beneficial effects:
[0022] An embodiment of the present disclosure provides an interlayer coupler, comprising: a first waveguide layer, formed with a first grating structure, the first grating structure being a one-dimensional periodic grating; a second waveguide layer, located above the first waveguide layer and formed with a second grating structure, the second grating structure being a one-dimensional periodic grating; wherein a light exit angle of one of the first grating structure and the second grating structure is complementary to a light incident angle of the other one.
[0023] By adopting this embodiment, by making the first grating structure and the second grating structure satisfy the predetermined condition that the light exit angle of one of them and the light incident angle of the other are complementary, the optical mode fields of the upper and lower grating structures are matched as much as possible to improve the coupling efficiency of the interlayer coupler. Specifically, the smaller the angle between the light exit direction and the light incident direction of the upper and lower grating structures, the more the peaks of the optical mode fields of the upper and lower grating structures are aligned in the upper and lower directions, so that the loss of light when entering the other grating structure after exiting from one grating structure is smaller. Therefore, by reasonably designing the first grating structure and the second grating structure, the coupling efficiency of the grating-based interlayer coupler is improved.
[0024] Furthermore, the materials and / or grating parameters of the first grating structure and the second grating structure are adapted to ensure that the first grating structure and the second grating structure satisfy that the angle of the outgoing light of one of them and the angle of the incident light of the other of them are complementary. Therefore, the material selection and structural design of the upper and lower grating structures are no longer carried out independently, but the adaptability between the two is comprehensively considered to ensure that the optical mode fields of the upper and lower grating structures are matched to reduce the loss in the light transmission process and improve the coupling efficiency.
[0025] Furthermore, the light emitting direction of the interlayer coupler is opposite to the light incident direction, which is beneficial to improving the coupling efficiency and reducing the manufacturing difficulty of the interlayer coupler.
[0026] Furthermore, the interlayer coupler provided in this embodiment is conducive to the three-dimensional integration of any material. Based on the above predetermined conditions, the corresponding grating parameters are designed according to the materials selected for the upper and lower grating structures, so that the material selection of the upper and lower grating layers is no longer restricted, and the interlayer coupler obtained by any material combination has a better coupling efficiency.
[0027] Furthermore, the first waveguide layer and the second waveguide layer are selected from a candidate library, the candidate library includes a plurality of standard waveguide layers, the materials and / or grating parameters of the grating structures formed in different standard waveguide layers are at least partially different, and each of the standard waveguide layers has the same optical mode field. Thus, a standard layer for interlayer coupling is provided, and corresponding grating parameters are designed according to material characteristics so that each standard waveguide layer has the same optical mode field, and users can arbitrarily select standard waveguide layers of different materials as light output layers and light input layers to combine and obtain an interlayer coupler with high coupling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 It is a schematic diagram of the optical mode field distribution of an interlayer coupler in the prior art;
[0029] Figure 2 is a structural schematic diagram of an interlayer coupler according to an embodiment of the present disclosure;
[0030] Figure 3 yes Figure 2 Schematic diagram of optical mode field distribution of the interlayer coupler shown;
[0031] Figure 4 is a schematic diagram of an interlayer coupler in the first typical application scenario of the present disclosure;
[0032] Figure 5 yes Figure 4 Schematic diagram of optical coupling simulation of the interlayer coupler shown;
[0033] Figure 6 is a schematic diagram of an interlayer coupler in a second typical application scenario of the present disclosure;
[0034] Figure 7 yes Figure 6 Schematic diagram of optical coupling simulation of the interlayer coupler shown;
[0035] Figure 8 is a flow chart of a method for forming an interlayer coupler according to an embodiment of the present disclosure;
[0036] Figures 9 to 15 It is a schematic diagram of the device cross-sectional structure corresponding to each step in the method for forming an interlayer coupler described in an embodiment of the present disclosure. DETAILED DESCRIPTION
[0037] As mentioned in the background art, coupling efficiency is one of the important indicators for measuring the performance of an interlayer coupler.
[0038] At present, most of the more common interlayer couplers use stacked gradient waveguides to form an inverse taper coupler to achieve optical coupling. This implementation method has strict restrictions on the spacing between the upper and lower layers of gradient waveguides. If the spacing is too large, it will seriously affect the optical coupling effect. In addition, there are also strict restrictions on the material selection of the upper and lower layers of gradient waveguides, resulting in great limitations in the application scenarios of this type of interlayer coupler.
[0039] Another type of interlayer coupler is based on gratings to achieve optical coupling between different layers. This implementation method has small restrictions on the spacing between the upper and lower gratings, and is more flexible in the selection of grating materials. However, the coupling efficiency of existing grating-based interlayer couplers is not satisfactory (for example, it can only reach 50% to 60%).
[0040] The inventor of this application has found through analysis that one of the reasons for the above problems is that when designing the existing interlayer coupler based on gratings, the upper grating and the lower grating are designed independently. As long as the light emitted by one grating can be received by the other grating, the optical mode field matching of the upper and lower gratings is not considered. The mismatch of the optical mode field will lead to high loss when light is transmitted from one grating to another. Figure 1 The interlayer coupler 100 is designed based on the optical fiber mode field. The optical mode field of the grating can be equivalent to Gaussian light (that is, the distribution of light conforms to Gaussian distribution). The peaks of the optical mode field 111 generated by the upper grating 11 and the peaks of the optical mode field 121 of the lower grating 12 are completely staggered, resulting in most of the light entering from the lower grating 12 being lost when coupled to the upper grating 11. Figure 1 The coupling efficiency of the designed interlayer coupler is very low.
[0041] In order to solve the above technical problems, the disclosed solution provides an interlayer coupler, comprising: a first waveguide layer, formed with a first grating structure, the first grating structure is a one-dimensional periodic grating; a second waveguide layer, located above the first waveguide layer and formed with a second grating structure, the second grating structure is a one-dimensional periodic grating; wherein the light exit angle of one of the first grating structure and the second grating structure is complementary to the light incident angle of the other one.
[0042] By adopting this embodiment, by making the first grating structure and the second grating structure satisfy the predetermined condition that the light exit angle of one of them and the light incident angle of the other are complementary, the optical mode fields of the upper and lower grating structures are matched as much as possible to improve the coupling efficiency of the interlayer coupler. Specifically, the smaller the angle between the light exit direction and the light incident direction of the upper and lower grating structures, the more the peaks of the optical mode fields of the upper and lower grating structures are aligned in the upper and lower directions, so that the loss of light when entering the other grating structure after exiting from one grating structure is smaller. Therefore, by reasonably designing the first grating structure and the second grating structure, the coupling efficiency of the grating-based interlayer coupler is improved.
[0043] In order to make the above-mentioned objects, features and beneficial effects of the present disclosure more obvious and easy to understand, the specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.
[0044] Figure 2 It is a schematic structural diagram of an interlayer coupler 200 according to an embodiment of the present disclosure.
[0045] The interlayer coupler 200 of this embodiment can be applied to a hybrid integrated circuit, for example, used for light transmission between different layers of the hybrid integrated circuit.
[0046] For ease of description, the stacking direction of the multilayer structure included in the interlayer coupler 200 is recorded as the up-down direction. The up-down direction may be parallel to the stacking direction of different layers in the hybrid integrated circuit. Figures 2 to 14 In the figure, areas with the same fill pattern indicate that the same material is used.
[0047] Specifically, refer to Figure 2 The interlayer coupler 200 may include a first waveguide layer 220 and a second waveguide layer 260 stacked one above the other. Figure 2 From a viewing angle, the second waveguide layer 260 is located above the first waveguide layer 220. Stacked up and down means that the projection of the first waveguide layer 220 in the up and down direction and the second waveguide layer 260 at least partially overlap.
[0048] Continue to refer Figure 2, the first waveguide layer 220 may be formed with a first grating structure 221, and the first grating structure 221 may include a plurality of grating teeth arranged at intervals. Further, the first waveguide layer 220 may also be formed with a first waveguide 222 at the end along the arrangement direction of the plurality of grating teeth, and the first waveguide 222 is connected to the first grating structure 221 to receive light output from the first grating structure 221 or transmit light to the first grating structure 221. In some embodiments, the first grating structure 221 and the first waveguide 222 may be made of the same material. In some embodiments, the first grating structure 221 and the first waveguide 222 may be formed in the same process.
[0049] Continue to refer Figure 2 , the second waveguide layer 260 may be formed with a second grating structure 261, and the second grating structure 261 may include a plurality of grating teeth arranged at intervals. Further, a second waveguide 262 may be formed at the ends of the plurality of grating teeth along the arrangement direction, and the second waveguide 262 is connected to the second grating structure 261 to receive light output from the second grating structure 261 or transmit light to the second grating structure 261. In some embodiments, the second grating structure 261 and the second waveguide 262 may be made of the same material. In some embodiments, the second grating structure 261 and the second waveguide 262 may be formed in the same process.
[0050] The light output from the first grating structure 221 can be coupled and transmitted to the second grating structure 261. Accordingly, the second grating structure 261 receives the light emitted from the first grating structure 221. At this time, the transmission path of the light is as follows: Figure 2 As shown, light enters the interlayer coupler 200 from the first waveguide 222, is coupled to the second grating structure 261 via the first grating structure 221, and then leaves the interlayer coupler 200 via the second waveguide 262. Alternatively, the light output from the second grating structure 261 can be coupled to the first grating structure 221, and accordingly, the first grating structure 221 receives the light emitted from the second grating structure 261. At this time, the transmission path of the light is as follows: Figure 2 The direction is opposite to the direction of the arrow shown. In this way, light transmission between different layers can be achieved.
[0051] Furthermore, the interlayer coupler 200 may include a semiconductor substrate for supporting the device structures of each layer included in the interlayer coupler 200. The substrate may be, for example, a silicon substrate. Figure 2 , the first waveguide layer 220 is located above the second semiconductor substrate 250, and the second waveguide layer 260 is located above the first waveguide layer 220. In some embodiments, the first waveguide layer 220 and the second waveguide layer 260 can be formed on the surface of the semiconductor substrate in sequence, and the order of their formation can be interchanged according to different preparation processes.
[0052] Further, for any grating structure in the first grating structure 221 and the second grating structure 261, the grating structure is a one-dimensional periodic grating. That is, the grating parameters of the single-layer grating structure are constant. The grating parameters may include, for example, period, height, etching depth, duty cycle (also called grating duty cycle), etc. Among them, the period is specifically the sum of the grating tooth width and the spacing between adjacent grating teeth. The height refers to the height of the waveguide layer forming the grating structure. For example, the height of the first grating structure 221 refers to the height of the first waveguide layer 220, and the height of the second grating structure 261 refers to the height of the second waveguide layer 260. The etching depth refers to the etching depth when the waveguide layer is etched to form the grating structure. Figure 2 Full etching is used as an example for exemplary display, that is, the etching depth of the first grating structure 221 is equal to its height, and the adjacent grating teeth obtained by etching are not connected. Similarly, the etching depth of the second grating structure 261 is equal to its height, and the adjacent grating teeth obtained by etching are not connected. In some embodiments, the etching depth of the single-layer grating structure can be less than its height, such as half etching. Figure 4 and Figure 6 The exemplary embodiment shows the case where the etching depth of a single-layer grating structure is smaller than its height.
[0053] Further, the grating structure includes a plurality of grating teeth uniformly distributed along one direction. Figure 2 , an arrangement direction of the plurality of grating teeth included in the first grating structure 221 is parallel to an arrangement direction of the plurality of grating teeth included in the second grating structure 261 .
[0054] Furthermore, the light exit angle of one of the first grating structure 221 and the light incident angle of the other one of the second grating structure 261 is complementary. That is, the sum of the light exit angle of one of the two grating structures and the light incident angle of the other one of the two grating structures is equal to 180°. Figure 2 Taking the exemplary light transmission direction as an example, the light emission angle of the first grating structure 221 is recorded as α, and the light incident angle of the second grating structure 261 is recorded as β. Then, the transmission of light between the upper and lower grating layers in the interlayer coupler 200 can meet the predetermined condition of α+β=180°. Experiments show that, reference Figure 3 The more the light exit angle and light incident angle of the upper and lower grating structures meet the aforementioned predetermined conditions, the higher the alignment of the wave crests of the optical mode field 223 of the first grating structure 221 and the wave crests of the optical mode field 263 of the second grating structure 261 in the up and down directions will be, thereby reducing the loss of light when it is transmitted from one grating structure to another, and the higher the coupling efficiency of the interlayer coupler 200 will be.
[0055] Furthermore, the materials and / or grating parameters of the first grating structure 221 and the second grating structure 261 are adapted. By designing the grating parameters of the first grating structure 221 and the second grating structure 261 in association, it is possible to ensure that the transmission of light in the interlayer coupler 200 meets the above-mentioned predetermined conditions, that is, to ensure that the extension direction of the outgoing light of one of the two grating structures is parallel to the extension direction of the incident light of the other one. Furthermore, as the material selected for the first grating structure 221 and the material selected for the second grating structure 261 change, the correlation between the grating parameters of the first grating structure 221 and the grating parameters of the second grating structure 261 also changes accordingly, so that the selection of materials is more flexible, and any combination of materials can achieve an interlayer coupler 200 with high coupling efficiency.
[0056] In a specific implementation, the materials of the first grating structure 221 and the second grating structure 261 may be the same. Further, the grating parameters of the first grating structure 221 and the second grating structure 261 may satisfy at least one of the following conditions: the period of the first grating structure 221 is greater than the period of the second grating structure 261; the height of the first grating structure 221 is equal to the height of the second grating structure 261; the etching depth of the first grating structure 221 is equal to the etching depth of the second grating structure 261; the duty ratios of the first grating structure 221 and the second grating structure 261 are the same.
[0057] For example, for the same material, in order to meet a higher coupling efficiency, the output incident angles of the upper and lower grating structures are complementary (for example, the first grating structure 221 can be emitted at a positive angle of 8°, and the second grating structure 261 needs to receive at a negative angle of 8°). According to the grating diffraction angle formula, the period of the second grating structure 261 is preferably smaller than the period of the first grating structure 221.
[0058] In a typical application scenario, refer to Figure 4 The materials of the first grating structure 221 and the second grating structure 261 can both be silicon (Si). The second grating structure 261 has a height of 220 nanometers (nm), an etching depth of 70nm, a period of 566nm, and a duty cycle of 0.55; the first grating structure 221 has a height of 220nm, an etching depth of 70nm, a period of 600nm, and a duty cycle of 0.55. Simulation shows that the use of Figure 4 The optical coupling efficiency of the interlayer coupler 200 can reach 97%. Figure 5 shown. Figure 5 (and the following Figure 7), the x direction is the extension direction of the grating structure (i.e., the arrangement direction of the plurality of grating teeth included in the first grating structure 221), and the y direction is the up-down direction of the interlayer coupler 200. The figure shows the spectrum of light transmitted on the upper and lower grating structures. The brighter the color, the greater the intensity of the light. The units of the x direction and the y direction are both meters (×10^-6).
[0059] In a specific implementation, the materials of the first grating structure 221 and the second grating structure 261 may be different. Further, the grating parameters of the first grating structure 221 and the grating parameters of the second grating structure 261 may satisfy at least one of the following conditions: the period of the first grating structure 221 is greater than the period of the second grating structure 261; the height of the first grating structure 221 is greater than the height of the second grating structure 261; the etching depth of the first grating structure 221 is greater than the etching depth of the second grating structure 261; the duty cycle of the first grating structure 221 is less than the duty cycle of the second grating structure 261.
[0060] In a typical application scenario, refer to Figure 6 , the material of the first grating structure 221 can be silicon, and the material of the second grating structure 261 can be silicon nitride (SiN). The height of the grating teeth in the first grating structure 221 is 220nm, the etching depth is 70nm, the period is 566nm, and the duty cycle is 0.55; the height of the grating teeth in the second grating structure 261 is 400nm, the etching depth is 250nm, the period is 980nm, and the duty cycle is 0.5. Simulation shows that the use of Figure 6 The optical coupling efficiency of the interlayer coupler 200 can reach 97%. Figure 7 shown.
[0061] In a specific implementation, the length of the first grating structure 221 may be substantially consistent with the length of the second grating structure 261. That is, the projections of the first grating structure 221 and the second grating structure 261 along the vertical direction substantially completely overlap.
[0062] Assuming that the periods of the upper and lower grating structures are different, the lengths of the upper and lower grating structures can be made close by adjusting the number of grating teeth included in each grating structure. Figure 6 The period of the first grating structure 221 is significantly greater than the period of the second grating structure 261 , and accordingly, the number of grating teeth in the first grating structure 221 is less than the number of grating teeth in the second grating structure 261 .
[0063] In this way, the loss of light during transmission between the two layers of grating structures can be further reduced, thereby improving the coupling efficiency.
[0064] In a specific implementation, the first grating structure 221 and / or the second grating structure 261 may be a rectangular grating. Different from the conventional gradually deformed chirped grating, the rectangular grating can ensure the one-dimensional periodicity of the grating structure. Further, the rectangular grating means that any grating structure of the first grating structure 221 and the second grating structure 261 has a rectangular outer contour in a plane perpendicular to the up and down direction. The design of the periodic grating is also conducive to reducing the difficulty of the process.
[0065] In a specific implementation, continue to refer to Figure 2 One of the first waveguide layer 220 and the second waveguide layer 260 is used to receive incident light, and the other one is used to emit outgoing light, and the transmission direction of the incident light is opposite to the transmission direction of the outgoing light.
[0066] Specifically, the first waveguide 222 and the second waveguide 262 may be located on the same side of the grating structure (the first grating structure 221 or the second grating structure 261) along the extension direction. Figure 2 From the perspective, the projections of the first waveguide 222 and the second waveguide 262 in the up and down directions are both located on the right side of the first grating structure 221. The light enters the first waveguide 222 from the right side of the interlayer coupler 200, is coupled to the second grating structure 261 via the first grating structure 221, and then is output from the right side of the interlayer coupler 200 via the second waveguide 262.
[0067] Furthermore, the projections of the first waveguide 222 and the second waveguide 262 in the vertical direction may at least partially overlap, completely overlap, or not overlap. Thus, the incident and / or emitted positions of light may be set as required, so that the interlayer coupler 200 can flexibly coordinate with the position layout of other devices in the hybrid integrated circuit.
[0068] Therefore, compared with the low coupling efficiency caused by co-directional light transmission (i.e., the light incident direction and the light emission direction are the same), the light emission direction of the interlayer coupler 200 in this embodiment is opposite to the light incident direction, thereby improving the coupling efficiency. Furthermore, it is also helpful to reduce the difficulty of manufacturing the interlayer coupler 200.
[0069] In a specific implementation, continue to refer to Figure 2 The interlayer coupler 200 may further include a first reflector layer 240 located on a side of the first waveguide layer 220 away from the second waveguide layer 260 . That is, the first reflector layer 240 may be located below the first waveguide layer 220 .
[0070] Furthermore, the projection of the first reflector layer 240 in the up-down direction at least covers the first grating structure 221 to reflect (and / or refract) the light emitted from the first grating structure 221 to improve the coupling efficiency.
[0071] Similarly, the interlayer coupler 200 may further include a second reflector layer 270 located on a side of the second waveguide layer 260 facing away from the first waveguide layer 220 . That is, the second reflector layer 270 may be located above the second waveguide layer 260 .
[0072] Furthermore, the projection of the second reflector layer 270 in the up and down directions at least covers the second grating structure 261 to reflect (and / or refract) the light emitted from the first grating structure 221 to the second grating structure 261, ensuring that more light can be received by the second grating structure 261, thereby improving coupling efficiency.
[0073] In some embodiments, for any one of the first reflector layer 240 and the second reflector layer 270 , the reflector layer may be made of a metal material.
[0074] In a specific implementation, continue to refer to Figure 2 , Figure 4 and Figure 6 An insulating layer 212 may be formed between the first waveguide layer 220 and the second waveguide layer 260 to isolate the upper and lower grating structures. The insulating layer 212 may be, for example, an oxide layer, such as silicon dioxide (SiO2).
[0075] Furthermore, a first isolation layer 230 may be filled between the first waveguide layer 220 and the first reflector layer 240 to provide isolation and protection between the two structures. For example, the first isolation layer 230 may cover the surface of the first grating structure 221 and the first waveguide 232 and fill the gap between adjacent grating teeth. The first isolation layer 230 may be, for example, an oxide layer, such as made of silicon dioxide (SiO2).
[0076] Similarly, a second isolation layer 232 may be filled between the second waveguide layer 260 and the second reflector layer 270 to provide isolation and protection between the two structures. For example, the second isolation layer 232 may cover the surfaces of the second grating structure 261 and the second waveguide 262 and fill the gaps between adjacent grating teeth. The second isolation layer 232 may be, for example, an oxide layer, such as made of silicon dioxide (SiO2).
[0077] Furthermore, a first protective layer 231 may be formed between the first reflector layer 240 and the second semiconductor substrate 250 to provide isolation and protection between the two layers. The first protective layer 231 may be, for example, an oxide layer, such as made of silicon dioxide (SiO2).
[0078] Similarly, the second reflector layer 270 may be covered with a second protective layer 233. The second protective layer 233 may be, for example, an oxide layer, such as made of silicon dioxide (SiO2).
[0079] In one specific implementation, reference Figure 8 , the method for forming the interlayer coupler 200 may include the following steps:
[0080] Step S120, providing a first wafer, wherein the first wafer has a first surface and a second surface opposite to each other;
[0081] Step S140, preparing a first grating structure on the first surface of the first wafer to obtain a first waveguide layer, wherein the first grating structure is a one-dimensional periodic grating;
[0082] Step S160, preparing a second grating structure on the second surface of the first wafer to obtain a second waveguide layer, wherein the second grating structure is a one-dimensional periodic grating, wherein the light exit angle of one of the first grating structure and the second grating structure is complementary to the light incident angle of the other one.
[0083] Next, combine Figures 9 to 15 The formation process of the interlayer coupler 200 is described in detail.
[0084] Specifically, refer to Fig. 9 In step S120, the first wafer 210 provided may be made of SOI (Silicon-On-Insulator) material. The first wafer 210 includes, from bottom to top, a first semiconductor substrate 211, an insulating layer 212, and a semiconductor film layer 213, wherein the first semiconductor substrate 211 and the semiconductor film layer 213 may both be Si, and the insulating layer 212 may be SiO2. The insulating layer 212 may also be called a buried oxide layer.
[0085] according to Fig. 9 From a perspective, the first surface 210 a of the first wafer 210 may specifically refer to the upper surface (ie, the front surface) of the semiconductor film layer 213 , and the second surface 210 b of the first wafer 210 may specifically refer to the lower surface (ie, the back surface) of the first semiconductor substrate 211 .
[0086] Further, refer to Fig.10 In step S140, the semiconductor film layer 213 may be etched to obtain the first grating structure 221 and the first waveguide 222. In response to the first grating structure 221 and the first waveguide 222 being obtained by processing the semiconductor film layer 213, the first waveguide layer 220 may be formed.
[0087] The specific etching process and corresponding process parameters can be determined according to the grating parameters of the first grating structure 221 to be formed and the material of the semiconductor film layer 213. The etching process may include a wet etching process and / or a dry etching process. Among them, the etching solution used in the wet etching process includes one or more of ammonia water, potassium hydroxide aqueous solution, and hydrofluoric acid; the etching gas used in the dry etching process includes one or more of octafluoroisobutylene, hydrobromic acid, boron trichloride, carbon tetrafluoride, chlorine, and trifluoromethane. The process parameters may include etching rate, reaction time, etc.
[0088] Further, refer to Fig.11 After performing step S140 to form the first waveguide layer 220, a deposition process may be used to form the first isolation layer 230 on the surface of the first waveguide layer 220. The deposition process may be a physical vapor deposition process, a chemical vapor deposition process, an atomic layer deposition process, or the like.
[0089] For example, a layer of SiO2 can be deposited on the semiconductor film layer 213 etched in step S140 by plasma enhanced chemical vapor deposition (PECVD) technology as the first isolation layer 230, and the SiO2 covers the surface of the first waveguide 222 and the first grating structure 221 and fills the recesses between adjacent grating teeth.
[0090] Further, refer to Fig.12 After forming the first isolation layer 230, the first reflector layer 240 can be prepared on the surface of the first isolation layer 230. For example, the first reflector layer 240 can be prepared on the surface of the first isolation layer 230 by using an evaporation process. Further, the first protective layer 231 is formed on the surface of the first reflector layer 240 and the first isolation layer 230 by using a deposition process.
[0091] Further, in step S160, Fig.12 The first wafer 210 with the first waveguide layer 220 is bonded invertedly to a semiconductor substrate (eg, a second semiconductor substrate 250) to obtain a Fig.13 The second surface 210 b of the first wafer 210 is shown facing upward.
[0092] Then, a second grating structure 261 is prepared on the second surface 210b of the first wafer 210 to obtain a second waveguide layer 260. Fig.14, the second surface 210b of the first wafer 210 can be processed by a grinding process and / or an etching process to remove the first semiconductor substrate 211 and thin the insulating layer 212. Further, a semiconductor film layer is deposited on the surface of the thinned insulating layer 212, and the semiconductor film layer is etched by an etching process to obtain a second grating structure 261 and a second waveguide 262. In response to the second grating structure 261 and the second waveguide 262 obtained by the processing, a second waveguide layer 260 can be formed, such as Fig.15 shown.
[0093] The specific etching process and corresponding process parameters can be determined according to the grating parameters of the second grating structure 261 to be formed and the material of the semiconductor film layer. The semiconductor film layer deposited in this step can be, for example, a SiN layer, which can be prepared by low pressure chemical vapor deposition (LPCVD).
[0094] Further, after the second waveguide layer 260 is prepared by executing step S160, a deposition process may be used to form a second isolation layer 232 on the surface of the second waveguide layer 260. Further, after the second isolation layer 232 is formed, a second reflector layer 270 may be prepared by an evaporation process on the surface of the second isolation layer 232. Further, a second protective layer 233 may be formed on the surface of the second reflector layer 270 and the second isolation layer 2320 by a deposition process. Thus, the following can be prepared: Figure 2 An interlayer coupler 200 is shown.
[0095] It should be pointed out that the above Figures 8 to 15 Only one possible preparation method of the interlayer coupler 200 is described exemplarily. In practical applications, under the premise of ensuring that the materials and / or grating parameters of the first grating structure and the second grating structure are adapted so that the first grating structure and the second grating structure satisfy the complementarity between the outgoing light angle of one of them and the incident light angle of the other, the interlayer coupler can be prepared by different process steps as needed. For example, Figure 4 and Figure 6The preparation process of the interlayer coupler 200 shown can be: a first protective layer 231 can be deposited on the surface of the second semiconductor substrate 250, a first reflector layer 240 can be prepared by an evaporation process on the surface of the first protective layer 231, a first isolation layer 230 can be deposited on the surface of the first reflector layer 240, a first grating structure 221 can be deposited and half-etched on the surface of the first isolation layer 230, an insulating layer 212 can be deposited on the surface of the first grating structure 221, a second grating structure 261 can be deposited and half-etched on the surface of the insulating layer 212, a second isolation layer 232 can be deposited on the surface of the second grating structure, a second reflector layer 270 can be prepared by an evaporation process on the surface of the second isolation layer 232, and a second protective layer 233 can be formed by a deposition process on the surfaces of the second reflector layer 270 and the second isolation layer 2320.
[0096] From the above, by adopting this embodiment, by making the first grating structure 221 and the second grating structure 261 satisfy the predetermined condition that the light exit angle of one of them and the light incident angle of the other one are complementary, the optical mode fields of the upper and lower grating structures are matched as much as possible to improve the coupling efficiency of the interlayer coupler. Specifically, the smaller the angle between the light exit direction and the light incident direction of the upper and lower grating structures, the more the peaks of the optical mode fields of the upper and lower grating structures are aligned in the upper and lower directions, so that the loss of light when entering the other grating structure after exiting from one grating structure is smaller. Therefore, by reasonably designing the first grating structure 221 and the second grating structure 261, the coupling efficiency of the grating-based interlayer coupler 200 is improved.
[0097] Furthermore, the material selection and structural design of the upper and lower grating structures are no longer carried out independently, but the compatibility between the two is comprehensively considered to ensure that the optical mode fields of the upper and lower grating structures are matched to reduce the loss in the light transmission process and improve the coupling efficiency.
[0098] Furthermore, the interlayer coupler 200 provided in this embodiment is conducive to the three-dimensional integration of any material. Based on the above predetermined conditions, the corresponding grating parameters are designed according to the materials selected for the upper and lower grating structures, so that the material selection of the upper and lower grating layers is no longer restricted, and the interlayer coupler 200 obtained by any material combination has a better coupling efficiency.
[0099] For example, the materials of the first waveguide layer 220 and the second waveguide layer 260 may be active SOI and SiN, respectively. For another example, the materials of the first waveguide layer 220 and the second waveguide layer 260 may be active SOI and lithium niobate, respectively. For another example, the materials of the first waveguide layer 220 and the second waveguide layer 260 may be active SOI and laser, respectively.
[0100] In some embodiments, the interlayer coupler 200 may further include a third waveguide layer (not shown) located above the second waveguide layer 260, and the third waveguide layer includes a third grating structure. The grating parameters and / or materials of the second grating structure 261 are adapted to the grating parameters and / or materials of the third grating structure so that the light exit angle of one of the second grating structure 261 and the third grating structure and the light incident angle of the other are complementary. Thus, this embodiment can realize the optical coupling of any number of layers, and can apply the advantages of multiple materials to monolithic integration to realize a multi-layer optical integrated chip. For example, the materials of the first waveguide layer 220, the second waveguide layer 260 and the third waveguide layer can be active SOI, SiN and laser, respectively. In this example, the position of the second reflector 270 can be moved to the side of the third waveguide layer away from the second waveguide layer 260.
[0101] In a specific implementation, the first waveguide layer 220 and the second waveguide layer 260 may be selected from a candidate library, respectively. The candidate library may include a plurality of standard waveguide layers, the materials and / or grating parameters of the grating structures formed in different standard waveguide layers are at least partially different, and each standard waveguide layer has the same optical mode field.
[0102] Specifically, the materials that may be used in the grating structure can be expanded or traversed in advance, and the grating parameters are determined for each material according to the same optical mode field to obtain a standard waveguide layer corresponding to the material.
[0103] When designing a chip, users (e.g., designers) can select corresponding standard waveguide layers from the candidate library as the optical input layer and optical output layer, respectively, based on the materials of the upper and lower layers that need to be optically coupled. For example, if a chip includes an upper laser layer and a lower silicon layer, and these two layers need to be optically coupled, the user can select from the candidate library a standard waveguide layer corresponding to the laser and a standard waveguide layer corresponding to the silicon material to combine and obtain an interlayer coupler. Thus, the interlayer optical coupler obtained by the combination is an interlayer coupler material determined based on the materials of the two-layer structure that needs to be optically coupled in the chip, so that users are not restricted by the materials that can be selected for the interlayer coupler when designing the chip.
[0104] Furthermore, since the standard waveguide layers corresponding to any material have the same optical mode field, the interlayer coupler obtained by the user's arbitrary design of the upper and lower layer combination can have the highest coupling efficiency.
[0105] Therefore, all kinds of material chips are designed with standard male and female optical input and output (InOut, referred to as IO) ports to facilitate interlayer coupling and hybrid integration. Specifically, a standard layer for interlayer coupling is provided, and the corresponding grating parameters are designed according to the material characteristics so that each standard waveguide layer has the same optical mode field. Users can arbitrarily select standard waveguide layers of different materials as the light output layer and the light input layer to combine and obtain an interlayer coupler with high coupling efficiency.
[0106] In a specific implementation, the interlayer coupler of this embodiment can be applied to an optical chiplet adapter board, that is, the interlayer coupler can be set on a carrier as a functional chip (also called a functional circuit block). A plurality of other functional chips are also arranged on the carrier, and each functional chip is interconnected with the interlayer coupler through the carrier, and the interlayer coupler is used to realize the optical connection between other functional chips. Other functional chips can be, for example, laser chips, filter chips, etc.
[0107] In a specific implementation, the interlayer coupler of this embodiment can be used as an interface in a splicable optical field programmable gate array (FPGA). For example, the chip is programmable and universal, and the chip provides multiple programmable output ports. Different output ports of the chip can be connected to different functional modules, and the interlayer coupler also connects the output ports of the chip to realize the optical connection between the functional modules. The functional modules may include filter modules, laser modules, etc.
[0108] In some embodiments, the interlayer coupler of this embodiment can provide a universal optical interconnection interface standard.
[0109] In some embodiments, the interlayer coupler of this embodiment can realize a monolithically integrated high-speed optical module.
[0110] In some embodiments, the interlayer coupler of this embodiment can be applied to high-speed control and low-loss phased array radar.
[0111] In some embodiments, the interlayer coupler of this embodiment can be applied to a high-speed tunable ultra-narrow linewidth monolithically integrated laser.
[0112] Although the disclosure is disclosed as above, the disclosure is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the disclosure, so the protection scope of the disclosure should be based on the scope defined by the claims.
Claims
1. An interlayer coupler, characterized in that: include: A first waveguide layer is formed with a first grating structure, wherein the first grating structure is a one-dimensional periodic grating; a second waveguide layer, located above the first waveguide layer and formed with a second grating structure, wherein the second grating structure is a one-dimensional periodic grating; The light exit angle of one of the first grating structure and the second grating structure is complementary to the light incident angle of the other one of them.
2. The interlayer coupler according to claim 1, characterized in that: An extending direction of the outgoing light of one of the first grating structure and the second grating structure is parallel to an extending direction of the incident light of the other one of them.
3. The interlayer coupler according to claim 1 or 2, characterized in that: For any one of the first grating structure and the second grating structure, the grating parameters of the grating structure are constant; and the correlation between the grating parameters of the first grating structure and the grating parameters of the second grating structure is determined according to the materials of the first grating structure and the second grating structure.
4. The interlayer coupler according to claim 3, characterized in that: The first grating structure and the second grating structure are made of the same material, and the grating parameters of the first grating structure and the second grating structure satisfy at least one of the following conditions: The period of the first grating structure is greater than the period of the second grating structure; The height of the first grating structure is equal to the height of the second grating structure; The etching depth of the first grating structure is equal to the etching depth of the second grating structure; The first grating structure and the second grating structure have the same duty cycle.
5. The interlayer coupler according to claim 4, characterized in that: The first grating structure and the second grating structure are both made of silicon.
6. The interlayer coupler according to claim 3, characterized in that: The first grating structure and the second grating structure are made of different materials, and the grating parameters of the first grating structure and the second grating structure satisfy at least one of the following conditions: The period of the first grating structure is greater than the period of the second grating structure; The height of the first grating structure is greater than the height of the second grating structure; The etching depth of the first grating structure is greater than the etching depth of the second grating structure; The duty cycle of the first grating structure is smaller than the duty cycle of the second grating structure.
7. The interlayer coupler according to claim 6, characterized in that: The first grating structure is made of silicon nitride, and the second grating structure is made of silicon.
8. The interlayer coupler according to claim 1, characterized in that: One of the first waveguide layer and the second waveguide layer is used to receive incident light, and the other one of the first waveguide layer and the second waveguide layer is used to emit outgoing light, and the transmission direction of the incident light is opposite to the transmission direction of the outgoing light; and / or The first grating structure and / or the second grating structure is a rectangular grating; and / or The lengths of the first grating structure and the second grating structure are consistent.
9. The interlayer coupler according to claim 1, characterized in that: Also includes: a first reflector layer, located on a side of the first waveguide layer facing away from the second waveguide layer; The second reflector layer is located on a side of the second waveguide layer facing away from the first waveguide layer.
10. The interlayer coupler according to claim 1, characterized in that: The first waveguide layer and the second waveguide layer are respectively selected from a candidate library, the candidate library includes a plurality of standard waveguide layers, the materials and / or grating parameters of the grating structures formed in different standard waveguide layers are at least partially different, and each of the standard waveguide layers has the same optical mode field.
11. A method for forming an interlayer coupler, characterized in that: include: Providing a first wafer, the first wafer having a first side and a second side opposite to each other; Preparing a first grating structure on the first surface of the first wafer to obtain a first waveguide layer, wherein the first grating structure is a one-dimensional periodic grating; A second grating structure is prepared on the second surface of the first wafer to obtain a second waveguide layer, wherein the second grating structure is a one-dimensional periodic grating, wherein a light exit angle of one of the first grating structure and the light incident angle of the other of the first grating structure and the second grating structure are complementary.
12. The forming method according to claim 11, characterized in that: After the first waveguide layer is prepared, the method further includes: Depositing a first isolation layer on the surface of the first waveguide layer; A first reflector layer is prepared on the surface of the first isolation layer.
13. The forming method according to claim 11, characterized in that: The step of preparing a second grating structure on the second surface of the first wafer to obtain a second waveguide layer comprises: Invertingly bonding the first wafer on which the first waveguide layer is prepared to a semiconductor substrate, wherein the second surface of the inverted first wafer faces upward; A second grating structure is prepared on the second surface of the first wafer to obtain a second waveguide layer.
14. The forming method according to claim 11, characterized in that: After the second waveguide layer is prepared, the method further comprises: Depositing a second isolation layer on the surface of the second waveguide layer; A second reflector layer is prepared on the surface of the second isolation layer.