Waveguide structure and method of manufacturing the same

Abstract

The application discloses a waveguide structure and a manufacturing method thereof to solve the problem of excessive leakage loss and bending loss in the prior art. The waveguide structure comprises a substrate, a first support layer on the substrate, a core layer above the first support layer, light propagating in the core layer, and a second support layer on the first support layer, wherein the side of the second support layer adjacent to the first support layer has a cavity; the core layer is in the cavity, and part of the surface of the core layer is wrapped by the cavity. The core layer replaces the original cladding medium with air through the cavity, thereby improving the refractive index difference between the core layer and the cladding layer, making it easier for the propagating light to achieve total reflection, thereby reducing the leakage loss and the bending loss, and further reducing the bending radius of the waveguide, thereby reducing the chip size and improving the process integration. The manufacturing method of the waveguide structure involves mature processes, is simple, reliable and easy to implement, and has good practicability.

Description

Technical Field

[0001] This invention relates to the field of optical waveguide technology, specifically to a waveguide structure and its manufacturing method, and more particularly to a waveguide structure with an air cladding and its manufacturing method. Background Technology

[0002] Optical waveguides are the medium that confines the propagation of light waves. A typical optical waveguide employs a "core / cladding" structure where an optically less dense medium clad an optically denser medium. To achieve total internal reflection and ensure compatibility with semiconductor thin-film fabrication processes, SiO2 (refractive index approximately 1.45) is currently commonly used as the outer cladding layer of optical waveguides, while SiN (refractive index approximately 2.01) and Si (refractive index approximately 3.5) are used as the core layer.

[0003] However, due to the small difference in refractive index between SiO2 and SiN, the radius of curvature of optical waveguides is limited when considering leakage loss (caused by light scattering during transmission in a waveguide) and bending loss (caused by light leakage due to changes in the incident angle during transmission in a bent waveguide). Although the refractive index difference between Si and SiO2 is significant, the waveguide transmission loss is still substantial due to the inherent limitations of the Si material itself.

[0004] Therefore, given the limited availability of materials, finding a solution that can simultaneously accommodate waveguide loss, leakage loss, and bending loss is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide a waveguide structure and a method for manufacturing the same, which can have an air cladding while also providing good protection for the core layer.

[0006] To achieve the above objectives, a first aspect of the present invention provides a waveguide structure comprising: a substrate; a first support layer located on the substrate; a core layer located above the first support layer, wherein light propagates in the core layer; and a second support layer located on the first support layer, wherein the side of the second support layer adjacent to the first support layer has a cavity; wherein the core layer is located in the cavity, and a portion of the surface of the core layer is enclosed by the cavity.

[0007] Furthermore, the first support layer is the lower cladding layer of the core layer.

[0008] Furthermore, the first support layer includes at least one support portion, and a portion of the lower surface of the core layer is connected to the support portion to suspend the core layer.

[0009] Furthermore, the materials of the first support layer and the second support layer include silicon dioxide, and the material of the core layer includes at least one of silicon, silicon nitride, and lithium niobate.

[0010] Furthermore, the core layer comprises one or more layers, and the cross-section of each core layer is independently selected from convex or rectangular shapes.

[0011] Furthermore, the waveguide structure also includes a release hole that penetrates the second support layer and is connected to the cavity.

[0012] Furthermore, the distance between the surface of the core layer and the inner wall of the cavity is not less than 2 μm.

[0013] Furthermore, the waveguide structure also includes at least one of a grating, a photodetector, and a modulator, wherein at least a portion of the grating, photodetector, and modulator is located on the same substrate as the core layer.

[0014] Furthermore, the waveguide structure also includes a first metal layer and a second metal layer that are electrically connected. Both the first metal layer and the second metal layer are located on the second support layer. The first metal layer is a wiring layer, and the second metal layer is an electrode lead-out terminal.

[0015] A second aspect of the present invention is to provide a method for manufacturing a waveguide structure, comprising: forming a first support layer on a substrate; forming a core layer on the first support layer; forming a sacrificial layer on the first support layer and etching the sacrificial layer to retain a portion of the cavity to be formed; forming a second support layer on the first support layer and the sacrificial layer; etching the second support layer to form a release hole, and removing the sacrificial layer through the release hole to form the cavity.

[0016] Furthermore, the material of the sacrificial layer includes polyimide, and the sacrificial layer is formed on the first support layer. After the sacrificial layer is etched, the thickness of the sacrificial layer surrounding the core layer is not less than 2 μm.

[0017] Furthermore, the materials of the first support layer and the second support layer include silicon dioxide, and the material of the core layer includes at least one of silicon, silicon nitride, and lithium niobate.

[0018] Furthermore, the core layer comprises one or more layers, and the cross-section of each core layer is independently selected from a convex shape or a rectangle.

[0019] Furthermore, before etching the second support layer to form the release hole, the method further includes: forming a first metal layer and a second metal layer with electrical connection on the second support layer, wherein the first metal layer is a wiring layer, the second metal layer is an electrode lead-out end, and the release hole avoids the first metal layer and the second metal layer.

[0020] A third aspect of the present invention is to provide another method for manufacturing a waveguide structure, comprising: forming a first sacrificial layer on a substrate; etching the first sacrificial layer to retain a region to be formed of a lower cladding layer; forming a first support layer on the substrate; forming a core layer on the first sacrificial layer, wherein the end of the core layer is located on the first support layer; forming a second sacrificial layer on the first sacrificial layer, the core layer, and the first support layer, and etching the second sacrificial layer to retain a region to be formed of an upper cladding layer; forming a second support layer on the second sacrificial layer and the first support layer; etching the second support layer to form a release hole, and removing the first and second sacrificial layers through the release hole to form an upper cladding layer and a lower cladding layer respectively, wherein the upper and lower cladding layers are connected to form a cavity.

[0021] Furthermore, the materials of the first support layer and the second support layer include silicon dioxide, and the material of the core layer includes at least one of silicon, silicon nitride, and lithium niobate.

[0022] Furthermore, the materials of the first sacrificial layer and the second sacrificial layer include polyimide, and the thickness of both the first sacrificial layer and the second sacrificial layer is not less than 2 μm.

[0023] Furthermore, the core layer comprises one or more layers, and the cross-section of each core layer is independently selected from convex or rectangular shapes.

[0024] Furthermore, before etching the second support layer to form the release hole, the method further includes: forming a first metal layer and a second metal layer with electrical connection on the second support layer, wherein the first metal layer is a wiring layer, the second metal layer is an electrode lead-out end, and the release hole avoids the first metal layer and the second metal layer.

[0025] The waveguide structure provided by this invention uses a sacrificial layer to form a cavity. While ensuring the original function, it replaces the upper cladding medium or the upper and lower cladding media of the core layer with air, thereby increasing the refractive index difference between the core layer and the cladding layer. This makes it easier to achieve total internal reflection of propagating light, thereby reducing leakage loss and bending loss. While reducing losses, it also allows for a larger design space for the bending radius of the waveguide, thereby reducing chip size and improving process integration, providing a foundation for larger-scale silicon photonics chip process integration.

[0026] Furthermore, the waveguide structure of this invention not only provides an air cladding for the core layer, but also includes a second support layer on the outside of the air cladding as a protective structure. This prevents direct exposure of the core layer, avoiding damage during subsequent processing and use, and improving device reliability and lifespan. While protecting the core layer, the second support layer can also serve as a substrate for the metal interconnect layer, further facilitating the integration of the waveguide with other electronic components or enabling functions such as phase modulation of propagating light.

[0027] The two waveguide structure manufacturing methods provided by this invention involve mature semiconductor processes that are simple, reliable, and easy to implement, and have high practicality. Attached Figure Description

[0028] The above and other objects, features, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings. Furthermore, for clarity, the various parts in the drawings are not drawn to scale.

[0029] Figure 1 This is a cross-sectional schematic diagram of the waveguide structure according to the first embodiment of the present invention;

[0030] Figure 2 This is a cross-sectional schematic diagram of the waveguide structure according to the second embodiment of the present invention;

[0031] Figure 3a and Figure 3b This is a cross-sectional schematic diagram of the waveguide structure according to the third embodiment of the present invention;

[0032] Figure 4 This is a cross-sectional schematic diagram of the waveguide structure according to the fourth embodiment of the present invention;

[0033] Figure 5 This is a flowchart illustrating the manufacturing process of the waveguide structure according to the first embodiment of the present invention.

[0034] Figures 6a to 6h This is a cross-sectional schematic diagram of each manufacturing step of the waveguide structure in the first embodiment of the present invention;

[0035] Figure 7 This is a flowchart illustrating the manufacturing process of the waveguide structure according to the second embodiment of the present invention.

[0036] Figures 8a to 8f This is a cross-sectional schematic diagram of the waveguide structure manufacturing steps in the second embodiment of the present invention;

[0037] Figure 9 This is a flowchart illustrating the manufacturing process of the waveguide structure according to the third embodiment of the present invention.

[0038] Figures 10a to 10l This is a cross-sectional schematic diagram of each manufacturing step of the waveguide structure in the third embodiment of the present invention;

[0039] Figure 11 This is a flowchart illustrating the manufacturing process of the waveguide structure according to the fourth embodiment of the present invention.

[0040] Figures 12a to 12d This is a cross-sectional schematic diagram of the waveguide structure manufacturing steps in the fourth embodiment of the present invention;

[0041] Figures 13a to 13i This is a cross-sectional schematic diagram of each manufacturing step of the waveguide structure in the fifth embodiment of the present invention. Detailed Implementation

[0042] Various embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments. In the following detailed description of the invention, certain specific details are described in detail. Those skilled in the art will fully understand the invention even without these detailed descriptions. To avoid obscuring the essence of the invention, well-known methods, processes, and procedures are not described in detail.

[0043] Figure 1 This is a cross-sectional schematic diagram of the waveguide structure according to the first embodiment of the present invention; as shown Figure 1 As shown, in this embodiment, the waveguide structure includes a substrate 110, a first support layer 120, a core layer 130, a second support layer 140, and a cavity 151. The first support layer 120 is located on the substrate 110, and the core layer 130 is located on the first support layer 120, serving as the lower cladding layer for the core layer 130. The second support layer 140 is also located on the first support layer 120, with the core layer 130 enclosed within it. A cavity 151 exists between the core layer 130 and the second support layer 140. The second support layer 140 also has a release hole 152 above the cavity 151, communicating with the cavity 151. The cavity 151 communicates with the outside of the second support layer 140 through the release hole 152.

[0044] Specifically, the substrate 110 is, for example, a silicon-based substrate, and the first support layer 120 is, for example, made of silicon dioxide material, with a thickness of, for example, 5-8 μm. The core layer 130 is, for example, made of silicon nitride material, and is grown on the first support layer 120. The second support layer 140 is also located on the first support layer 120, and a cavity 151 is provided on the side of the second support layer 140 adjacent to the first support layer 120, with the core layer 130 located in the cavity 151. Experience shows that if the distance between the inner wall of the cavity 151 and the core layer 130 is too small, the light transmission loss will be relatively large. Therefore, the distance between the inner wall of the cavity 151 and the surface of the core layer 130 is, for example, not less than 2 μm, that is, the distance between the upper surface and the side surface of the core layer 130 and the inner wall of the cavity 151 is greater than or equal to 2 μm; or, in other words, the distance between the upper surface and the side surface of the core layer 130 and the inner surface of the second support layer 140 is greater than or equal to 2 μm, thereby preventing light leakage and avoiding increased loss. The cavity 151 contains air, which can form an air cladding. That is, the cavity 151 serves as the upper cladding of the core layer 130, so that except for the lower surface of the core layer 130 adjacent to the first support layer 120, the remaining surfaces of the core layer 130 are located in the cavity 151 and are wrapped by the air cladding.

[0045] Furthermore, in order to form the cavity 151, the second support layer 140 is also provided with a release hole 152 that communicates with the cavity 151. The release hole 152 is a process hole required to form the cavity 151. The number, position, size, shape and other aspects of the release hole 152 can be adjusted according to the processing requirements.

[0046] Figure 2 This is a cross-sectional schematic diagram of the waveguide structure according to the second embodiment of the present invention. The waveguide structure of the second embodiment is similar to that of the first embodiment. The positions and connections of the substrate 110, the first support layer 120, the core layer 130, the second support layer 140, the cavity 151, and the release hole 152 will not be described in detail here. The difference between the second embodiment and the first embodiment is that the waveguide structure of the second embodiment also includes a first metal layer 161 and a second metal layer 162 located on the second support layer 140.

[0047] It should be noted that, although in Figure 2 In the view, the second metal layer 162 appears to be located above the release hole 152 and blocking the release hole 152. However, in the actual structure, the second metal layer 162 and the release hole 152 are a certain distance apart in the direction perpendicular to the paper. They are staggered and avoid each other, so that the release hole 152 is not blocked by the second metal layer 162.

[0048] Specifically, the first metal layer 161 is, for example, a Ti / TiN thin film, which can be used as a metal wiring layer. The first metal layer 161 is located above the core layer 130. The material of the second metal layer 162 is, for example, AlCu. The second metal layer 162 can be used as an electrode lead-out terminal. The second metal layer 162 is connected to the first metal layer 161. Figure 2 In the embodiment shown, both the first metal layer 161 and the second metal layer 162 are adjacent to the second support layer 140. However, in other embodiments, the second metal layer 162, which serves as the electrode lead-out end, can also be located on the second metal layer 161 and the two can be in electrical contact.

[0049] Since a first metal layer 161 is provided above the core layer 130, the phase of the propagating light in the core layer 130 can be controlled by the first metal layer 161 through the thermo-optic effect, thereby achieving the function of optical phase modulation.

[0050] Figure 3aThis is a cross-sectional schematic diagram of a waveguide structure according to a third embodiment of the present invention. In this embodiment, the waveguide structure includes: a substrate 210, a first support layer 220, a core layer 230, a second support layer 240, and a cavity 251. The first support layer 220 is located on the substrate 210, and the core layer 230 is located above the first support layer 220 and suspended in the cavity 251, such that the lower surface of the core layer 230 has an air cladding. The second support layer 240 is located on the first support layer 220, and its side adjacent to the first support layer 220 has a concave structure opposite to the core layer 230. This concave structure can form a portion of the cavity 251, such that the upper surface and both sides of the core layer 230 are located within the cavity 251, thereby having an air cladding.

[0051] Similarly, in order to form the cavity 251, the second support layer 240 is also provided with a release hole 252 that communicates with the cavity 251. The release hole 252 is a process hole required to form the cavity 251. The number, position, size, shape and other aspects of the release hole 252 can be adjusted according to the processing requirements.

[0052] See Figure 3b The schematic diagram of the waveguide structure of the third embodiment of the present invention shown shows that at least a portion of the left and right ends of the core layer 230 is located on the first support layer 220, so that the core layer 230, except for the positions at both ends, can be suspended in the cavity 251. Compared with the first embodiment, more of the surface of the core layer 230 is exposed in the cavity 251, so that both the upper and lower cladding are air, realizing a larger area of ​​air cladding, thereby achieving a higher refractive index difference between the core layer and the cladding, concentrating the light more firmly in the waveguide, and reducing transmission loss.

[0053] Figure 4 This is a cross-sectional schematic diagram of the waveguide structure according to the fourth embodiment of the present invention. The waveguide structure of this fourth embodiment is similar to that of the third embodiment, except that the waveguide structure of this fourth embodiment further includes a first metal layer 261 and a second metal layer 262 located on the second support layer 240. Although in Figure 4 In the view, the first metal layer 261 appears to be located above the release hole 252 and blocking the release hole 252. However, in the actual structure, the first metal layer 261 and the release hole 252 are a certain distance apart in the direction perpendicular to the paper, and they are staggered from each other. The release hole 252 is not blocked by the first metal layer 261 or the second metal layer 262.

[0054] Specifically, the first metal layer 261 is, for example, a Ti / TiN thin film, which can be used as a metal wiring layer. The first metal layer 261 is located above the core layer 230. The material of the second metal layer 262 is, for example, AlCu. The second metal layer 262 can be used as an electrode lead-out terminal. The second metal layer 262 is connected to the first metal layer 261. Figure 4In the embodiment shown, both the first metal layer 261 and the second metal layer 262 are adjacent to the second support layer 240. However, in other embodiments, the second metal layer 262, which serves as the electrode lead-out end, can also be located on the second metal layer 261 and the two are electrically connected.

[0055] Since a first metal layer 261 is provided above the core layer 230, the phase of the propagating light in the core layer 230 can be controlled by the first metal layer 261 through the thermo-optic effect, thereby achieving the function of optical phase modulation.

[0056] Figure 5 A schematic diagram of the manufacturing steps of the waveguide structure according to the first embodiment of the present invention is shown. Figures 6a to 6h It shows the relationship with Figure 5 The corresponding cross-sectional views of each manufacturing step of the waveguide structure.

[0057] like Figure 5 and Figures 6a-6h As shown, the manufacturing method of the waveguide structure in the first embodiment includes the following steps:

[0058] In step S10, a first support layer is formed on the substrate; as shown Figure 6a As shown, a silicon dioxide layer with a thickness of 5-8 μm is grown on the substrate 110 as the first support layer 120. The first support layer 120 can serve as the lower cladding layer of the core layer 130. Of course, the thickness of the first support layer 120 can also be other sizes, which can be designed and adjusted according to product needs.

[0059] In step S20, a core layer is formed on the first support layer; as shown Figure 6b and Figure 6c As shown, silicon nitride is grown in the first support layer 120 to form a core layer film 131 covering the first support layer. Then, the core layer film 131 is etched to obtain the desired core layer 130.

[0060] In step S30, a sacrificial layer is formed on the first support layer, and the sacrificial layer is etched to preserve the portion of the cavity to be formed; for example... Figure 6d and Figure 6eAs shown, a sacrificial layer 150 is formed on the first support layer 120. The material of the sacrificial layer 150 is, for example, polyimide (PI adhesive). The thickness of the sacrificial layer 150 is greater than the thickness of the core layer 130. The sacrificial layer 150 covers the first support layer 120 and the core layer 130. Then, part of the sacrificial layer 150 is removed by photolithography and etching, so that the remaining sacrificial layer 150 surrounds the core layer 130 and has a certain thickness. In subsequent steps, the remaining sacrificial layer 150 can be released (removed) by etching, thereby forming a cavity that partially surrounds the core layer 130, so that the core layer 130 has a corresponding air cladding, more specifically, an upper cladding. Of course, the sacrificial layer 150 can also be made of other materials, as long as it is a medium that can be removed by a release process and has a high selectivity for etching compared to the first support layer 120.

[0061] In step S40, a second support layer is formed on the first support layer and the sacrificial layer; as shown Figure 6f As shown, a second support layer 140 is formed on the first support layer 120 and the sacrificial layer 150. The second support layer 140 is used to provide support and protection. Its material is, for example, silicon dioxide, to protect the core layer 130 from external damage.

[0062] In step S50, the second support layer is etched to form a release hole, and the sacrificial layer is removed through the release hole to form a cavity; as shown Figure 6g and Figure 6h As shown, the second support layer 140 is etched to form a release hole 152 that communicates with the sacrificial layer 150, so that the sacrificial layer 150 is partially exposed. The sacrificial layer 150 is removed by etching (release) process to form a cavity 151, so that the upper cladding of the core layer 130 is an air cladding.

[0063] Figure 7 A schematic diagram of the manufacturing steps of the waveguide structure according to the second embodiment of the present invention is shown. Steps S10 to S40 are similar to those of the first embodiment and will not be described again here. The difference of the second embodiment is that step S41 is added between step S40 and step S50, in which a first metal layer and a second metal layer are formed on the second support layer. Correspondingly, in step S50, the release hole needs to avoid the positions of the first metal layer and the second metal layer.

[0064] Specifically, such as Figure 8a and Figure 8bAs shown, a first metal layer 161 is formed on the second support layer 140. The first metal layer 161 is, for example, Ti / TiN. The first metal layer 161 is then patterned to give it a specific shape and position, such as being located above the core layer 130. A second metal layer 162, connected to the first metal layer 161, is then formed on the second support layer 140. The second metal layer 162 serves, for example, as an electrode lead-out terminal of the first metal layer 161. The second metal layer 162 is, for example, made of aluminum or copper. The first metal layer 161 can serve as the metal wiring layer of this waveguide structure, so that the phase of the light in the core layer 130 can be modulated by the thermo-optical effect using the first metal layer 161.

[0065] In step S50, the second support layer is etched to form a release hole, and the sacrificial layer is removed through the release hole; this step S50 corresponds to Figures 8c to 8f ,in, Figure 8d and Figure 8f They are respectively Figure 8c and Figure 8e A side sectional view. (See attached image.) Figure 8c and Figure 8d As shown, the second support layer 140 is etched to form a release hole 152 communicating with the sacrificial layer 150, so that a portion of the sacrificial layer 150 is exposed through the release hole 152; of course, the release hole 152 should avoid the locations of the first metal layer 161 and the second metal layer 162. Figure 8e and Figure 8f As shown, the sacrificial layer 150 is removed through the release hole 152 using a release process, forming a cavity 151 at the original location of the sacrificial layer 150, thereby making the upper cladding of the core layer 130 an air cladding.

[0066] Figure 9 A schematic diagram of the manufacturing steps of the waveguide structure according to the third embodiment of the present invention is shown. Figures 10a to 10l It shows the relationship with Figure 9 The corresponding cross-sectional views of each manufacturing step of the waveguide structure, wherein, Figure 10f for Figure 10e Side view sectional view, Figure 10l for Figure 10k Side view sectional view.

[0067] refer to Figure 9 and Figures 10a-10l The manufacturing method of the waveguide structure in the third embodiment includes the following steps:

[0068] In step S100, a first sacrificial layer is formed on the substrate; as shown Figure 10aAs shown, a 5-8 μm thick polyimide (PI adhesive) layer is grown on the substrate 210 as the first sacrificial layer 253. Of course, the material and thickness of the first sacrificial layer 253 can be designed according to product requirements, and its thickness can also be other dimensions.

[0069] In step S200, the first sacrificial layer is etched to preserve the area where the lower cladding layer will be formed; for example... Figure 10b As shown, the first sacrificial layer 253 is etched, for example, only the area below the core layer 230 in the subsequent steps is retained, that is, the lower cladding area corresponding to the core layer 230.

[0070] In step S300, a first support layer is formed on the substrate; as shown Figure 10c As shown, a first support layer 220 is formed on the substrate 210, and the top surface of the first support layer 220 is made flush or substantially flush with the top surface of the first sacrificial layer 253 by surface planarization processes such as chemical mechanical polishing (CMP).

[0071] In step S400, a core layer is formed on the first sacrificial layer, and the end of the core layer is located on the first support layer; as shown Figure 10d A core layer film 231 is formed on the first sacrificial layer 253 and the first support layer 220. The core layer film 231 is, for example, a silicon nitride film. Figure 10f for Figure 10e Side view sectional view, such as Figure 10e and Figure 10f As shown, the core layer film 231 is etched to form a core layer 230 of the required shape and size. Figure 10e In this configuration, the core layer 230 is located on the first sacrificial layer 253, and its width is smaller than the width of the first sacrificial layer 253; Figure 10f In this process, the core layer 230 is also located on the first sacrificial layer 253, and the left and right ends of the core layer 230 are respectively located on the first support layers 220 on both sides of the first sacrificial layer 253. Since the left and right ends of the core layer 230 are at least partially connected to the first support layers 220, when the first sacrificial layer 253 is removed in the subsequent process, most of the lower surface of the core layer 230 can be suspended in the cavity, so that the lower cladding of the core layer 230 is an air cladding.

[0072] In step S500, a second sacrificial layer is formed on the first sacrificial layer, the core layer, and the first support layer, and the second sacrificial layer is etched to preserve the area where the upper cladding layer will be formed; for example Figure 10g to Figure 10hAs shown, a second sacrificial layer 254 is formed on the first sacrificial layer 253, the core layer 230 and the first support layer 220, and the second sacrificial layer 254 is etched so that the second sacrificial layer 254 only retains the part that wraps the core layer 230, and the second sacrificial layer 254 corresponds to the first sacrificial layer 253. The two are connected on the outside of the core layer 230, so that the core layer 230 is surrounded by the two sacrificial layers.

[0073] In step S600, a second support layer is formed on the second sacrificial layer and the first support layer; as shown Figure 10i As shown, a second support layer 240 is formed on the second sacrificial layer 253 and the first support layer 220. The second support layer 240 is made of silicon dioxide, for example. Furthermore, the upper surface of the second support layer 240 can be planarized using a CMP process to facilitate subsequent processing.

[0074] In step S700, the second support layer is etched to form a release hole, and the second sacrificial layer and the first sacrificial layer are removed through the release hole, thereby forming an upper cladding layer and a lower cladding layer, which are connected to form a cavity; Figure 10j As shown, the second support layer 240 is etched to form a release hole 252. The release hole 252 penetrates the second support layer 240, exposing a portion of the second sacrificial layer 253 through the release hole 252. Figure 10k and Figure 10l As shown, where, Figure 10l for Figure 10k These are cross-sectional views from different angles. The second sacrificial layer 254 and the first sacrificial layer 253 are removed using a release process through the release hole 252, forming a cavity 251. The cavity 251 encloses the core layer 230, resulting in air cladding on both the top and bottom of the core layer 230. Figure 10l As can be seen, when the first sacrificial layer 253 and the second sacrificial layer 254 are removed, the left and right ends of the core layer 230 are "overlapped" onto the first support layer 220; in other words, the first support layer 220 includes one or more support parts, and the left and right ends of the core layer 230 are "overlapped" onto the support parts, so that the middle part of the core layer 230 is suspended, thereby achieving the effect that both the upper and lower cladding layers are air cladding layers.

[0075] Figure 11 A schematic diagram of the manufacturing steps of the waveguide structure according to the fourth embodiment of the present invention is shown. Steps S100 to S600 are similar to those of the third embodiment and will not be described again here. The difference of the fourth embodiment is that step S610 is added between step S600 and step S700, in which a first metal layer and a second metal layer are formed on the second support layer. Correspondingly, in step S700, the release hole needs to avoid the positions of the first metal layer and the second metal layer.

[0076] Specifically, in step S610, a first metal layer and a second metal layer are formed on the second support layer; as shown... Figure 12a As shown, a first metal layer 261 is formed on the second support layer 240. The first metal layer 261 is, for example, Ti / TiN. The first metal layer 261 is then patterned to give it a specific shape and position, such as being located above the core layer 230. A second metal layer 262, connected to the first metal layer 261, is then formed on the second support layer 240. The second metal layer 262 serves, for example, as an electrode lead-out terminal of the first metal layer 261. The second metal layer 262 is, for example, made of aluminum or copper. The first metal layer 261 can serve as the metal wiring layer of this waveguide structure, so that the phase of the light in the core layer 230 can be modulated by the thermo-optical effect using the first metal layer 261.

[0077] In step S700, the second support layer is etched to form a release hole, and the first and second sacrificial layers are removed through the release hole; this step S700 corresponds to Figures 12b to 12d .like Figure 12b As shown, the second support layer 240 is etched to form a release hole 252 communicating with the second sacrificial layer 254, so as to expose the second sacrificial layer 254. This release hole 252 should avoid the locations of the first metal layer 261 and the second metal layer 262. Figure 12c As shown, the second sacrificial layer 254 and the first sacrificial layer 253 are removed through the release hole 252 using a release process, creating a cavity 251 at the original sacrificial layer location, thus making both the upper and lower cladding layers of the core layer 230 air cladding layers. Wherein, Figure 12d for Figure 12c The side view section, from Figure 12d As can be seen, the left and right ends of the core layer 230 are located on the first support layer 220, thereby allowing the middle section of the core layer 230 to be suspended.

[0078] Figures 13a to 13i Cross-sectional views of the manufacturing steps of the waveguide structure according to the fifth embodiment of the present invention are shown. In this fifth embodiment, the waveguide structure is similar to that of the second embodiment; to a certain extent, the fifth embodiment can be considered as integrating the waveguide structure of the second embodiment onto an SOI (Silicon-On-Insulator) wafer. Therefore, the manufacturing method steps of the waveguide structure in this fifth embodiment will not be described in detail, but only through the cross-sectional views of each manufacturing step.

[0079] like Figure 13a As shown, the SOI wafer includes a substrate 310, a base layer 320, and a device layer 330. The substrate 310 is, for example, an insulating substrate, the base layer 320 is, for example, a silicon dioxide layer, and the device layer 330 is, for example, a silicon layer, which can be used to form various devices and core layers.

[0080] like Figure 13b and Figure 13c As shown, the SOI wafer undergoes multi-step photolithography etching, and doped layers are implanted into different regions stepwise as needed to form different functional areas and device structures. For example, it includes a first core layer 331 and a second core layer 332. Both core layers are made of silicon, for example. A base layer 320 serves as the lower cladding layer for both core layers. The cross-section of the first core layer 331 is, for example, convex, forming a ridge waveguide structure. The aspect ratio of the first core layer 331 is approximately 1:2, and the height of its shoulder (second high plane) is approximately two-thirds of the overall height. By adjusting the height of the shoulder, the conductivity of the first core layer 331 can be partially altered. If the shoulder height increases, the transmission loss will further decrease; if the shoulder height decreases, although the propagation loss will increase, the waveguide can obtain more propagation modes. Of course, the first core layer 331 can also be made of silicon nitride, with an aspect ratio of, for example, 1:1, and the shoulder height requirement is similar to that of silicon.

[0081] The cross-section of the second core layer 332 is, for example, rectangular, forming a strip waveguide structure with an aspect ratio of, for example, not less than 1:1. Other regions of the device layer 330 include various doping types such as P, N, P+, N+, P++, and N++ to form the required PN junction structure, thereby forming the modulator 333, grating, photodetector, etc. Since this application mainly relates to the waveguide structure, the description and introduction of the remaining parts of the SOI wafer are omitted.

[0082] like Figure 13d and Figure 13e As shown, a sacrificial layer 350 is formed on the device layer 330, and the sacrificial layer 350 is etched so that the remaining sacrificial layer 350 covers the upper and side surfaces of the first core layer 331 and the second core layer 332. Then, a support layer 340 is formed on this basis, and the upper surface of the support layer 340 is planarized. The support layer 340 is, for example, made of silicon dioxide.

[0083] like Figure 13f As shown, a through hole communicating with the device layer 330 is provided on the support layer 340, and conductive material is injected into the through hole to form a conductive channel 341 to lead out the components in the device layer 330. An interconnect layer 342 and a protective layer 343 are provided on the support layer 340. Metal wiring is provided in the interconnect layer 342, and the conductive channel 341 is connected to the metal wiring in the interconnect layer 342. A connection terminal 344 may also be provided on the protective layer 343 for electrically connecting the devices in the device layer 330 to the outside.

[0084] like Figure 13g and Figure 13hAs shown, a release hole 352 is formed, allowing the sacrificial layer 350 to be exposed through the release hole 352, and the sacrificial layer 350 is released using the release hole 352, thereby forming a cavity 351 at the original location of the sacrificial layer 350. That is, the upper cladding of the first core layer 331 and the second core layer 332 are both air cladding, increasing the refractive index difference between the core layer and the cladding, thereby improving their performance.

[0085] Of course, the placement of the release hole 352 needs to avoid the metal areas on the interconnect layer 342 and the protective layer 343, such as Figure 13i As shown in the top view, if no metal wiring 3421 passes above the area of ​​the sacrificial layer 350, release holes 352 can be uniformly opened in the support layer corresponding to the area of ​​the sacrificial layer 350; if metal wiring 3421 passes above the area of ​​the sacrificial layer 350, the metal wiring 3421 can be adjusted or the position of the release holes 352 can be adjusted to avoid the metal wiring.

[0086] Furthermore, the waveguide structure in this fifth embodiment is based on the SOI platform, and can be integrated with modules such as gratings, photodetectors, and modulators to form silicon-based optoelectronic devices, such as... Figure 13h The diagram shows chip-level integration, meaning that multiple devices can be fabricated on the same semiconductor substrate; of course, multiple devices can also be fabricated as individual dies and then integrated during packaging.

[0087] The waveguide structure provided by this invention uses a sacrificial layer to form a cavity. While ensuring the original function, the dielectric of the upper cladding or the upper and lower cladding layers of the core layer is replaced with air, thereby increasing the refractive index difference between the core layer and the cladding layer. This makes it easier to achieve total internal reflection of propagating light, thereby reducing leakage loss and bending loss. The bending radius of the waveguide can be further reduced, thereby reducing the chip size and improving the process integration, providing a foundation for larger-scale silicon photonic chip process integration.

[0088] Furthermore, the waveguide structure of this invention not only provides an air cladding for the core layer, but also includes a second support layer outside the air cladding as a protective structure. This prevents direct exposure of the core layer, avoiding damage during subsequent processing and use, and improving device reliability and lifespan. While protecting the core layer, the second support layer can also serve as a substrate for the metal interconnect layer, facilitating the integration of the waveguide with other electronic components or enabling functions such as phase modulation of propagating light. The manufacturing method of the waveguide structure provided by this invention involves mature, simple, reliable, and easy-to-implement processes, making it highly practical.

[0089] It should be noted that in the description of this invention, terms such as "first" and "second" are used only to facilitate the description of different orientations, parts, and components, and should not be construed as indicating or implying sequential relationships, relative importance, or implicitly indicating the number of technical features indicated.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A waveguide structure, characterized in that, include: Substrate; A first support layer is located on the substrate; A core layer, located above the first support layer, in which light propagates; The second support layer is located on the first support layer, and the side of the second support layer adjacent to the first support layer has a cavity; The core layer is located in the cavity, a portion of the surface of the core layer is wrapped by the cavity, and the end of the core layer is located on the first support layer, thereby being suspended in the cavity, such that the upper and lower cladding layers of the core layer are both air, and the upper and lower cladding layers are connected to form a single cavity.

2. The waveguide structure according to claim 1, characterized in that, The first support layer includes at least one support portion, and a portion of the lower surface of the core layer is connected to the support portion to suspend the core layer.

3. The waveguide structure according to any one of claims 1-2, characterized in that, The first support layer and the second support layer are made of silicon dioxide, and the core layer is made of at least one of silicon, silicon nitride, and lithium niobate.

4. The waveguide structure according to any one of claims 1-2, characterized in that, The core layer comprises one or more layers, and the cross-section of each core layer is independently selected from convex or rectangular shapes.

5. The waveguide structure according to any one of claims 1-2, characterized in that, It also includes a release hole that penetrates the second support layer and is connected to the cavity.

6. The waveguide structure according to any one of claims 1-2, characterized in that, The distance between the surface of the core layer and the inner wall of the cavity is not less than 2 μm.

7. The waveguide structure according to any one of claims 1-2, characterized in that, Also includes: At least one of a grating, a photodetector, and a modulator, wherein at least a portion of the grating, the photodetector, and the modulator are located on the same substrate as the core layer.

8. The waveguide structure according to any one of claims 1-2, characterized in that, It also includes a first metal layer and a second metal layer that are electrically connected. Both the first metal layer and the second metal layer are located on the second support layer. The first metal layer is a wiring layer and the second metal layer is an electrode lead-out terminal.

9. A method for manufacturing a waveguide structure, characterized in that, include: A first sacrificial layer is formed on the substrate; The first sacrificial layer is etched to preserve the area where the lower cladding layer will be formed; A first support layer is formed on the substrate; A core layer is formed on the first sacrificial layer, and the end of the core layer is located on the first support layer; A second sacrificial layer is formed on the first sacrificial layer, the core layer, and the first support layer, and the second sacrificial layer is etched to preserve the area to be formed of the upper cladding layer; A second support layer is formed on the second sacrificial layer and the first support layer; The second support layer is etched to form a release hole, and the second sacrificial layer and the first sacrificial layer are removed through the release hole, thereby forming the upper cladding layer and the lower cladding layer. The upper cladding layer and the lower cladding layer are connected to form a single cavity. The end of the core layer is located on the first support layer, thereby being suspended in the cavity, so that the upper and lower cladding layers of the core layer are both air.

10. The manufacturing method according to claim 9, characterized in that, The first support layer and the second support layer are made of silicon dioxide, and the core layer is made of at least one of silicon, silicon nitride, and lithium niobate.

11. The manufacturing method according to claim 9, characterized in that, The materials of the first sacrificial layer and the second sacrificial layer include polyimide; the thickness of both the first sacrificial layer and the second sacrificial layer is not less than 2 μm.

12. The manufacturing method according to claim 9, characterized in that, The core layer comprises one or more layers, and the cross-section of each core layer is independently selected from convex or rectangular shapes.

13. The manufacturing method according to claim 9, characterized in that, Before etching the second support layer to form a release hole, the method further includes forming a first metal layer and a second metal layer with electrical connections on the second support layer, wherein the first metal layer is a wiring layer, the second metal layer is an electrode lead-out terminal, and the release hole avoids the first metal layer and the second metal layer.

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