End face coupler and method of forming
By designing a ring-shaped silicon oxynitride waveguide and a tapered silicon oxynitride waveguide in the end-face coupler, the optical mode field matching problem was solved, and efficient optical signal coupling and low-loss transmission were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI INTEGRATED CIRCUIT RESEARCH & DEVELOPMENT CENTER CO LTD
- Filing Date
- 2024-12-25
- Publication Date
- 2026-06-26
AI Technical Summary
In existing technologies, the optical mode field size of ordinary single-mode optical fiber is difficult to match with the waveguide, resulting in low coupling efficiency and high optical signal loss, which limits the performance of optical chips.
Design an end-face coupler comprising a ring-shaped silicon oxynitride waveguide and a tapered silicon nitride waveguide. By setting a tapered silicon nitride waveguide inside the ring-shaped silicon oxynitride waveguide, the width is gradually increased to expand the optical mode field. The silicon nitride waveguide is wrapped with a second dielectric layer to restrict the propagation of optical signals in the ring-shaped silicon oxynitride waveguide and avoid leakage.
This improved coupling efficiency, reduced optical signal loss, and enabled low-loss and high-coupling-efficiency optical signal transmission.
Smart Images
Figure CN122284016A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to an end-face coupler and a method for forming it. Background Technology
[0002] Integrated optoelectronic chips use light waves as information carriers, and their high performance and low cost make them promising for applications in optical communication and optical computing. In practical applications, the waveguides in optoelectronic chips need to be coupled to single-mode optical fibers for optical signal transmission. Generally, based on the coupling method, they are divided into two main categories: end-face couplers (based on end-face coupling) and grating couplers (based on vertical coupling). Grating couplers have complex manufacturing processes, their operating bandwidth is limited by the grating bandwidth, and they are polarization-dependent; while end-face couplers have a larger bandwidth and are polarization-independent, making them more versatile.
[0003] However, the optical mode field size of ordinary single-mode fiber is very large, requiring a reduction in the waveguide size at the end face to increase the waveguide's mode field. However, due to manufacturing limitations, the reduction in waveguide size is limited. Therefore, it is difficult to match the optical mode fields of the waveguide and the fiber, resulting in low coupling efficiency, high optical signal loss, and limiting the performance of optical chips. Summary of the Invention
[0004] The purpose of this invention is to provide an end-face coupler and a method for forming it, which can improve coupling efficiency and reduce light loss.
[0005] To achieve the above objectives, the present invention provides an end-face coupler, comprising:
[0006] Substrate;
[0007] An isolation layer located on the surface of the substrate;
[0008] A silicon oxynitride waveguide is located on the surface of the isolation layer, and the longitudinal section of the silicon oxynitride waveguide is annular.
[0009] A silicon nitride waveguide located within the annular silicon oxynitride waveguide, the silicon nitride waveguide being separated from the silicon oxynitride waveguide by a first dielectric layer, the cross-section of the silicon nitride waveguide within the annular silicon oxynitride waveguide being tapered, and the width of the silicon nitride waveguide gradually increasing along the incident direction of light; and
[0010] A second dielectric layer covering the annular silicon oxynitride waveguide.
[0011] Optionally, in the end-face coupler, the silicon oxynitride waveguide is in the form of a rectangular ring.
[0012] Optionally, in the end-face coupler, the length of the tapered portion of the silicon nitride waveguide is the same as the length of the silicon oxynitride waveguide in cross-section.
[0013] Optionally, in the end-face coupler, the length of the silicon nitride waveguide located within the annular silicon oxynitride waveguide is 100μm to 300μm, and the width of the silicon nitride waveguide located outside the annular silicon oxynitride waveguide is 800nm to 1200nm.
[0014] Optionally, in the end-face coupler, the width of the silicon oxynitride waveguide is 2μm to 4μm, and the height of the silicon oxynitride waveguide is 1μm to 3μm.
[0015] Optionally, in the end-face coupler, the substrate comprises SOI.
[0016] Optionally, in the end-face coupler, the material of the isolation layer includes silicon dioxide.
[0017] Optionally, in the end-face coupler, both the first dielectric layer and the second dielectric layer comprise silicon dioxide.
[0018] The present invention also provides a method for forming an end-face coupler, comprising:
[0019] Provide substrate;
[0020] An isolation layer is formed on the surface of the substrate;
[0021] A first silicon oxynitride material layer and a first dielectric material layer are formed on the surface of the isolation layer;
[0022] A silicon nitride waveguide is formed on the surface of the first dielectric material layer, the silicon nitride waveguide covering a portion of the first dielectric material layer, and the cross-section of the portion of the silicon nitride waveguide is tapered, with its width gradually increasing along the incident direction of light.
[0023] A second dielectric material layer is formed on the surface of the first dielectric material layer, and the second dielectric material layer simultaneously covers the surface of the silicon nitride waveguide. The first dielectric layer and the second dielectric layer form a first dielectric layer, which encapsulates the silicon nitride waveguide.
[0024] A second silicon oxynitride material layer is formed on the surface of the first dielectric layer. The second silicon oxynitride material layer and the first silicon oxynitride material layer form an annular silicon oxynitride waveguide. The portion of the silicon oxynitride waveguide with a tapered cross-section is located within the annular silicon oxynitride waveguide.
[0025] In the end-face coupler and its forming method provided by this invention, the end-face coupler includes: a substrate; an isolation layer located on the surface of the substrate; a silicon oxynitride waveguide located on the surface of the isolation layer, the longitudinal section of the silicon oxynitride waveguide being annular; and a silicon nitride waveguide partially located within the annular silicon oxynitride waveguide, the silicon nitride waveguide being separated from the silicon oxynitride waveguide by a first dielectric layer. The cross-section of the silicon nitride waveguide located within the annular silicon oxynitride waveguide is conical, and the width of the silicon nitride waveguide gradually increases along the incident direction of light. This invention forms an annular silicon oxynitride waveguide, with a portion of the silicon nitride waveguide located inside the annular silicon oxynitride waveguide, confining light within the annular silicon oxynitride waveguide, thus expanding the optical mode field of the end-face coupler and improving coupling efficiency. Furthermore, the conical shape of the portion of the silicon nitride waveguide inside the annular silicon oxynitride waveguide allows the optical signal in the annular silicon oxynitride waveguide to gradually couple into the silicon nitride waveguide, preventing the optical signal from leaking into the first dielectric layer, thus reducing light loss. Attached Figure Description
[0026] Figure 1 This is a flowchart of a method for forming an end-face coupler according to an embodiment of the present invention;
[0027] Figure 2 This is a schematic diagram of the end-face coupler structure after forming a silicon nitride waveguide according to an embodiment of the present invention;
[0028] Figure 3 This is a schematic diagram of the end-face coupler after the formation of the first dielectric layer according to an embodiment of the present invention;
[0029] Figure 4 This is a schematic diagram of the end-face coupler structure after the formation of the second silicon oxynitride material layer according to an embodiment of the present invention;
[0030] Figure 5 This is a schematic diagram of the end-face coupler after forming a silicon oxynitride waveguide according to an embodiment of the present invention;
[0031] Figure 6 This is a schematic diagram of the end-face coupler after the formation of the second dielectric layer according to an embodiment of the present invention;
[0032] Figure 7 This is a cross-sectional view of the end-face coupler according to an embodiment of the present invention;
[0033] In the figure: 110 - substrate, 120 - isolation layer, 130 - silicon oxynitride waveguide, 131 - first silicon oxynitride material layer, 132 - second silicon oxynitride material layer, 140 - first dielectric layer, 141 - first dielectric material layer, 150 - silicon nitride waveguide, 160 - second dielectric layer. Detailed Implementation
[0034] The specific embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.
[0035] In the following text, the terms “first,” “second,” etc., are used to distinguish between similar elements and are not necessarily used to describe a specific order or chronological sequence. It should be understood that these terms, as used herein, may be replaced where appropriate. Similarly, if the methods described herein comprise a series of steps, and the order of these steps presented herein is not necessarily the only possible order in which they can be performed, and some described steps may be omitted and / or other steps not described herein may be added to the method.
[0036] Furthermore, it should be understood that when a layer (or film), region, pattern, or structure is referred to as being "on" a substrate, layer (or film), region, and / or pattern, it can be located directly on another layer or substrate, and / or intercalation layers may also be present. Additionally, it should be understood that when a layer is referred to as being "under" another layer, it can be located directly under that layer, and / or one or more intercalation layers may also be present. Furthermore, references to "on" and "under" the layers may be made based on the accompanying drawings.
[0037] Please refer to Figure 5 The present invention provides an end-face coupler, comprising: a substrate 110; an isolation layer 120 located on the surface of the substrate 110; a silicon oxynitride waveguide 130 located on the surface of the isolation layer 120, the silicon oxynitride waveguide 130 having an annular longitudinal section; a silicon nitride waveguide 150 partially located within the annular silicon oxynitride waveguide 130, the silicon nitride waveguide 150 being separated from the silicon oxynitride waveguide 130 by a first dielectric layer 140, the silicon nitride waveguide 150 located within the annular silicon oxynitride waveguide 130 having a conical cross section, and the width of the silicon nitride waveguide 150 gradually increasing along the incident direction of light, the silicon nitride waveguide located outside the annular silicon oxynitride waveguide having a rectangular cross section; and a second dielectric layer 160 covering the annular silicon oxynitride waveguide 130.
[0038] Accordingly, please refer to Figure 1 The present invention provides a method for forming an end-face coupler, comprising:
[0039] S11: Provides a substrate;
[0040] S12: Form an isolation layer on the surface of the substrate;
[0041] S13: A first silicon oxynitride material layer and a first dielectric material layer are formed on the surface of the isolation layer;
[0042] S14: A silicon nitride waveguide is formed on the surface of the first dielectric material layer. The silicon nitride waveguide covers part of the first dielectric material layer. The cross-section of the part of the silicon nitride waveguide is conical, and the width gradually increases along the incident direction of light.
[0043] S15: A second dielectric material layer is formed on the surface of the first dielectric material layer, the second dielectric material layer simultaneously covering the surface of the silicon nitride waveguide; the first dielectric material layer and the second dielectric material layer form a first dielectric layer, the first dielectric layer encapsulating the silicon nitride waveguide; and
[0044] S16: A second silicon oxynitride material layer is formed on the surface of the first dielectric layer. The second silicon oxynitride material layer and the first silicon oxynitride material layer form a ring-shaped silicon oxynitride waveguide. A portion of the silicon oxynitride waveguide with a tapered cross-section is located within the ring-shaped silicon oxynitride waveguide.
[0045] First, please refer to Figure 2 A substrate 110 is provided, which may be SOI. A silicon dioxide layer is deposited on the surface of the substrate 110 to form an isolation layer 120. Next, silicon oxynitride is deposited on the surface of the isolation layer 120 to form a first silicon oxynitride material layer 131. Then, silicon dioxide is deposited on the surface of the first silicon oxynitride material layer 131 to form a first dielectric material layer 141. Next, a silicon nitride material layer is formed on the surface of the first dielectric material layer 141, and the silicon nitride material layer is etched to form a silicon nitride waveguide 150, which covers a portion of the first dielectric material layer 141. Please refer to... Figure 6 The silicon nitride waveguide includes a first part, silicon nitride waveguide 150A, and a second part, silicon nitride waveguide 150B. The first part, silicon nitride waveguide 150A, has a tapered cross-section, with its width gradually increasing from the light-incident end face to the direction of light. The narrowest face of the tapered section is the light-incident end face.
[0046] Next, please refer to Figure 2 and Figure 3 Silicon dioxide is deposited on the surface of the first dielectric material layer 141 to form a second dielectric material layer. The surface of the second dielectric material layer is smoothed using a CMP process. The second dielectric material layer simultaneously covers the surface of the silicon nitride waveguide 150. The first dielectric material layer 141 and the second dielectric material layer form a first dielectric layer 140, which encapsulates the silicon nitride waveguide 150. The width of the silicon nitride waveguide is 2μm to 4μm, and the height of the silicon nitride waveguide is 1μm to 3μm.
[0047] Next, please refer to Figures 3 to 5The first dielectric layer 140 and the first silicon oxynitride (Si) material layer 131 are etched to expose a portion of the surface of the isolation layer 120. Silicon oxynitride is deposited on the surface of the first dielectric layer 140 using a chemical vapor deposition process to form a second Si oxynitride material layer 132, which simultaneously covers the surface of the isolation layer 120. Next, a portion of the second Si oxynitride material 132 is etched, leaving the remaining second Si oxynitride material 132 on the sidewalls and top of the first dielectric layer 140. The remaining second Si oxynitride material layer and the first Si oxynitride material layer 131 form a ring-shaped silicon oxynitride waveguide 130, which can be rectangular. A portion of the surface of the isolation layer 120 remains exposed outside the ring-shaped silicon oxynitride waveguide 130. Please refer to [reference needed]. Figure 7 The first silicon nitride waveguide 150A is located within the annular silicon oxynitride waveguide 130, and the second silicon nitride waveguide 150B is located outside the annular silicon oxynitride waveguide 130. In this embodiment, the width of the silicon nitride waveguide 150 at its end face is less than 150 nm. In cross-section, the length of the first silicon nitride waveguide 150A is the same as the length of the silicon oxynitride waveguide 130. The length of the first silicon nitride waveguide 150A is 100 μm to 300 μm, and the width of the second silicon nitride waveguide 150B is 800 nm to 1200 nm.
[0048] Next, please refer to Figure 6 and Figure 7 Silicon dioxide is deposited on the surface of the silicon oxynitride waveguide 130 and the surface of the exposed insulating layer 120 of the annular waveguide 130, and the surface of the silicon dioxide is polished to make the surface smooth, thereby forming a second dielectric layer 160. The second dielectric layer 160 surrounds the silicon oxynitride waveguide 130. The second dielectric layer 160 acts as a protective layer for the silicon oxynitride waveguide 130. Since the refractive index of silicon oxynitride (SiON), the material of the silicon oxynitride waveguide 130, is greater than that of the material SiO2 of the outer second dielectric layer 160, most of the light is confined within the annular silicon oxynitride waveguide 130 structure.
[0049] In this embodiment of the invention, a ring-shaped silicon oxynitride waveguide 130 is formed at the end face, and a silicon nitride waveguide 150 is located inside the ring. The relative positions of the silicon oxynitride waveguide 130 and the silicon nitride waveguide 150 expand the optical mode field of the end face coupler, matching it with existing optical fibers and improving coupling efficiency. Furthermore, the portion of the silicon nitride waveguide 150 inside the ring-shaped silicon oxynitride waveguide 130 is tapered, allowing the optical signal in the ring-shaped silicon oxynitride waveguide 130 to gradually couple into the silicon nitride waveguide 150, preventing the optical signal from leaking into the first dielectric layer 140, reducing optical loss, and thus forming a low-loss and high-coupling-efficiency end face coupler.
[0050] In summary, the end-face coupler and its formation method provided in this embodiment of the invention include: a substrate; an isolation layer located on the surface of the substrate; a silicon oxynitride waveguide located on the surface of the isolation layer, the longitudinal section of which is annular; and a silicon nitride waveguide partially located within the annular silicon oxynitride waveguide, the silicon nitride waveguide being separated from the silicon oxynitride waveguide by a first dielectric layer. The cross-section of the silicon nitride waveguide located within the annular silicon oxynitride waveguide is conical, and the width of the silicon nitride waveguide gradually increases along the incident direction of light. This invention forms an annular silicon oxynitride waveguide, with a portion of the silicon nitride waveguide located inside the annular silicon oxynitride waveguide, confining light within the annular silicon oxynitride waveguide, thus expanding the optical mode field of the end-face coupler and improving coupling efficiency. Furthermore, the conical shape of the portion of the silicon nitride waveguide inside the annular silicon oxynitride waveguide allows the optical signal in the annular silicon oxynitride waveguide to gradually couple into the silicon nitride waveguide, preventing the optical signal from leaking into the first dielectric layer, thereby reducing light loss.
[0051] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.
Claims
1. An end-face coupler, characterized in that, include: Substrate; An isolation layer located on the surface of the substrate; A silicon oxynitride waveguide located on the surface of the isolation layer, the silicon oxynitride waveguide having a ring-shaped longitudinal section; and A silicon nitride waveguide is partially located within the annular silicon oxynitride waveguide. The silicon nitride waveguide is separated from the silicon oxynitride waveguide by a first dielectric layer. The cross-section of the silicon nitride waveguide located within the annular silicon oxynitride waveguide is conical, and the width of the silicon nitride waveguide gradually increases along the incident direction of light.
2. The end-face coupler as described in claim 1, characterized in that, Also includes: A second dielectric layer covering the annular silicon oxynitride waveguide.
3. The end-face coupler as described in claim 1, characterized in that, The silicon oxynitride waveguide is in the shape of a rectangular ring.
4. The end-face coupler as described in claim 1, characterized in that, In cross-section, the length of the tapered portion of the silicon nitride waveguide is the same as the length of the silicon oxynitride waveguide.
5. The end-face coupler as described in claim 1, characterized in that, The length of the silicon nitride waveguide located within the annular silicon oxynitride waveguide is 100μm to 300μm, and the width of the silicon nitride waveguide located outside the annular silicon oxynitride waveguide is 800nm to 1200nm.
6. The end-face coupler as described in claim 1, characterized in that, The width of the silicon oxynitride waveguide is 2μm to 4μm, and the height of the silicon oxynitride waveguide is 1μm to 3μm.
7. The end-face coupler as described in claim 1, characterized in that, The material of the isolation layer includes silicon dioxide.
8. The end-face coupler as described in claim 1, characterized in that, Both the first dielectric layer and the second dielectric layer comprise silicon dioxide.
9. A method for forming an end-face coupler as described in any one of claims 1 to 8, characterized in that, include: Provide substrate; An isolation layer is formed on the surface of the substrate; A first silicon oxynitride material layer and a first dielectric material layer are formed on the surface of the isolation layer; A silicon nitride waveguide is formed on the surface of the first dielectric material layer, the silicon nitride waveguide covering a portion of the first dielectric material layer, and the cross-section of the portion of the silicon nitride waveguide is tapered, with its width gradually increasing along the incident direction of light. A second dielectric material layer is formed on the surface of the first dielectric material layer, and the second dielectric material layer simultaneously covers the surface of the silicon nitride waveguide. The first dielectric material layer and the second dielectric material layer form a first dielectric layer, and the first dielectric layer encapsulates the silicon nitride waveguide. as well as A second silicon oxynitride material layer is formed on the surface of the first dielectric layer. The second silicon oxynitride material layer and the first silicon oxynitride material layer form an annular silicon oxynitride waveguide. The portion of the silicon oxynitride waveguide with a tapered cross-section is located within the annular silicon oxynitride waveguide.
10. The method for forming an end-face coupler as described in claim 9, characterized in that, After forming a second silicon oxynitride material layer on the surface of the first dielectric layer, and after the second silicon oxynitride material layer and the first silicon oxynitride material layer form a ring-shaped silicon oxynitride waveguide, the method further includes forming a second dielectric layer on the surface of the silicon oxynitride waveguide.