Structure for a directional coupler and method for manufacturing a structure for a directional coupler

Abstract

Structure (10) for a directional coupler, wherein the structure (10) comprises: a first waveguide core (12) with a first section (20); a second waveguide core (14) with a second section (21) which is arranged laterally adjacent to the first section (20); a third waveguide core (42) comprising a first conical section (48), a second conical section (50) and a third section (46) arranged longitudinally between the first conical section (48) and the second conical section (50); and a fourth waveguide core (44) comprising a first conical section (49), a second conical section (51) and a fourth section (47) arranged longitudinally between the first conical section (49) and the second conical section (51), wherein the fourth section (47) is located laterally next to the third section (46), wherein the third section (46) is arranged above the first section (20) and the fourth section (47) is arranged above the second section (21), wherein the first waveguide core (12) has a first conical section (26) connected to a first end of the first section (20) and a second conical section (28) connected to a second end of the first section (20), and the second waveguide core (14) has a first conical section (27) connected to a first end of the second section (21) and a second conical section (29) connected to a second end of the second section (21), wherein the first conical section (48) of the third waveguide core (42) is arranged over the first conical section (26) of the first waveguide core (12), the second conical section (50) of the third waveguide core (42) is arranged over the second conical section (28) of the first waveguide core (12), the first conical section (49) of the fourth waveguide core (44) is arranged over the first conical section (27) of the second waveguide core (14), and the second conical section (51) of the fourth waveguide core (44) is arranged over the second conical section (29) of the second waveguide core (14).

Description

background

[0001] The present invention relates to photonic chips and in particular structures for a directional coupler and methods for manufacturing a structure for a directional coupler.

[0002] Photonic chips are used in many applications and systems, including but not limited to data communication and computing systems. A photonic chip integrates optical components, such as waveguides, optical switches, and directional couplers, and electronic components, such as field-effect transistors, into a single platform. Among other factors, integrating both types of components onto the same chip can reduce layout area, cost, and operating overhead.

[0003] Directional couplers are used on a photonic chip to split propagating optical signals between different waveguide cores. A directional coupler comprises sections of the waveguide cores guided with a reduced lateral spacing chosen to promote optical coupling over a specific coupling length. Conventional directional couplers have a large footprint because a long coupling length is required to compensate for the weak coupling between the waveguide cores. Furthermore, the splitting provided by a directional coupler can be polarization-sensitive. In particular, different types of directional couplers may be required to split optical signals polarized with the transverse electrode mode (TE) as opposed to those polarized with the transverse magnetic mode (TM).

[0004] Document US 2018 / 0314005A1 discloses a polarization divider consisting of a silicon nitride (SiN) waveguide core configured to receive an input light signal with a first polarization mode and a second polarization mode, and a silicon (Si) slot waveguide core located near the SiN waveguide core, having a tapered section at a first end and configured to couple the first polarization mode to the Si slot waveguide core.

[0005] According to US patent 2007 / 0122080A1, an optical directional coupler is known. This directional coupler consists of two straight optical waveguides, each with a core, which run longitudinally and are located close to one another, forming an optical coupler section. Each core of each straight waveguide has a center line. It also consists of a tapered optical waveguide with a core connected to the core of at least one of the straight waveguides. The width of the core of the tapered waveguide tapers towards the at least one straight waveguide, and the profile of the tapered waveguide is asymmetrical with respect to the center line of the core of the at least one straight waveguide.

[0006] Improved structures for a directional coupler and methods for manufacturing a structure for a directional coupler are required. Summary

[0007] In one embodiment of the invention, a structure for a directional coupler is provided according to independent claim 1. Advantageous embodiments thereof are defined in dependent claims 2 to 9.

[0008] In another embodiment of the invention, a method for forming a structure for a directional coupler according to independent claim 10 is provided. An advantageous embodiment thereof is defined in dependent claim 11. Brief description of the drawings

[0009] The accompanying drawings, which form part of this description, depict various embodiments of the invention and, together with the general description of the invention above and the detailed description of the embodiments below, serve to explain the embodiments of the invention. In the drawings, the same reference numerals refer to the same features in the different views. Fig. Figure 1 is a schematic top view of a structure in an initial manufacturing phase of a process according to the embodiments of the invention. Fig. 2 is a cross-sectional view of the structure, generally along line 2-2 in Fig. 1 is running. Fig. 2A is a cross-sectional view of the structure, generally along the line 2A-2A in Fig. 1 is running. Fig. 2B is a cross-sectional view of the structure, generally along the line 2B-2B in Fig. 1 is running. Fig. 3 is a top view of the structure in a Fig. 1 following manufacturing phase. Fig. 4 is a cross-sectional view of the structure, generally along line 4-4 in Fig. 3 proceeds. Fig. 4A is a cross-sectional view of the structure, generally along line 4A-4A in Fig. 3 proceeds. Fig. 4B is a cross-sectional view of the structure, generally along the line 4B-4B in Fig. 3 proceeds. Fig. 5 is a cross-sectional view of the structure in a Fig. 3 following manufacturing phase. Fig. Figure 6 is a cross-sectional view of the structure, generally along line 6-6 in Fig. 5 proceeds. Fig. 6A is a cross-sectional view of the structure, generally along line 6A-6A in Fig. 5 proceeds. Fig. 6B is a cross-sectional view of the structure, generally along line 6B-6B in Fig. 5 proceeds. Fig. 7 is a cross-sectional view of the structure in a Fig. 6 following manufacturing phase. Fig. 8, Fig. 8A, Fig. Figure 8B shows cross-sectional views of a structure according to alternative embodiments of the invention. Fig. 9, Fig. 9A, Fig. Figure 9B shows cross-sectional views of a structure according to alternative embodiments of the invention. Fig. 10, Fig. 10A, Fig. Figures 10B are cross-sectional views of a structure according to alternative embodiments of the invention. Fig. Figure 11 is a cross-sectional view of a structure according to alternative embodiments of the invention. Detailed description

[0010] With regard to the Fig. 1, Fig. 2, Fig. 2A, Fig. 2B and according to embodiments of the invention, a structure 10 for a directional coupler comprises a waveguide core 12 and a waveguide core 14, both arranged over different sections of a dielectric layer 16. The structure 10 has a coupling region 18 in which a section 20 of the waveguide core 12 extends longitudinally along a longitudinal axis 13 and a section 21 of the waveguide core 14 extends longitudinally along a longitudinal axis 15. The section 20 of the waveguide core 12 can be symmetrical with respect to the longitudinal axis 13 and the section 21 of the waveguide core 14 can be symmetrical with respect to the longitudinal axis 15. The section 20 of the waveguide core 12 and the section 21 of the waveguide core 14 are arranged side by side in the coupling region 18.The longitudinal axis 13 of section 20 of the waveguide core 14 in the coupling region 18 can be arranged parallel to the longitudinal axis 15 of section 21 of the waveguide core 12 in the coupling region 18. Section 20 of the waveguide core 12 and section 21 of the waveguide core 14 can be laterally spaced apart by an offset distance d1, which can be measured as the lateral offset between the longitudinal axes 13 and 15.

[0011] The waveguide core 12 further comprises a set of bends 22 in an input region 17 of the structure 10, a set of bends 24 in an output region 19 of the structure 10, a conical section 26 connecting the bends 22 to the section 20, and a conical section 28 connecting the section 20 to the bends 24. The section 20 is arranged longitudinally between the conical section 26 and the conical section 28. Similarly, the waveguide core 14 further comprises a set of bends 23 in the input region 17 of the structure 10, a set of bends 25 in the output region 19 of the structure 10, a conical section 27 connecting the bends 23 to the section 21, and a conical section 29 connecting the section 21 to the bends 25. Section 21 is arranged longitudinally between the conical section 27 and the conical section 29.

[0012] The waveguide core 12 has side walls in the form of opposing side surfaces 32, 33 projecting from the dielectric layer 16, and the waveguide core 14 has side walls in the form of opposing side surfaces 34, 35 projecting from the dielectric layer 16. In the coupling region 18, the side surface 32 of section 20 of the waveguide core 12 is arranged adjacent to the side surface 34 of section 21 of the waveguide core 14. In one embodiment, the widths w1 of sections 20, 21 can be constant over their respective lengths.

[0013] Section 20 of the waveguide core 12 is laterally spaced from section 21 of the waveguide core 14 within the coupling region 18 by a smaller distance than the distance separating the waveguide cores 12 and 14 outside the coupling region 18. The side surface 32 of section 20 of the waveguide core 12 can be positioned adjacent to and parallel with side surface 34 of section 20 of the waveguide core 14, and side surfaces 32 and 34 can be separated within the coupling region 18 by a gap that may be uniform within the coupling region 18. Outside the coupling region 18, side surface 32 of the waveguide core 12 and side surface 34 of the waveguide core 14 can be separated by a larger gap.The sets of bends 22, 24 in the input region 17 and the sets of bends 23, 25 in the output region 19 cause corresponding changes in the distance between the side face 32 of the waveguide core 12 and the side face 34 of the waveguide core 14. Due to the larger distance between the side faces 32, 34 in the input region 17 and in the output region 19, the optical coupling between the waveguide cores 12, 14 outside the coupling region 18 is negligible. The conical sections 26, 27, 28, 29 can have a geometric shape that varies along their respective lengths based on a linear function. In an alternative embodiment, the conical sections 26, 27, 28, 29 can have a geometric shape that varies along their respective lengths based on a nonlinear function, such as a quadratic, parabolic, or exponential function.

[0014] The waveguide cores 12, 14 can be formed from a single-crystal semiconductor material, e.g., single-crystal silicon. In one embodiment, the single-crystal semiconductor material can consist of a fixture layer of a silicon-on-insulator (SOI) substrate, which also comprises a buried oxide layer forming the dielectric layer 16 and a handle substrate 30 formed from a single-crystal semiconductor material, such as single-crystal silicon, below the buried oxide layer. The waveguide cores 12, 14 can be structured from the fixture layer by lithography and etching processes. The fixture layer can be completely etched to define the waveguide cores 12, 14, or alternatively, only partially etched to define a thin residual layer or plate on the dielectric layer 16, which is connected to lower sections of the waveguide cores 12, 14.The waveguide cores 12, 14 can have coplanar or substantially coplanar top and bottom surfaces, as well as a uniform or substantially uniform thickness and a rectangular or substantially rectangular cross-sectional shape.

[0015] With regard to the Fig. 3, Fig. 4, Fig. 4A, Fig. 4B, in which identical reference signs refer to identical features in the Fig. 1, Fig. 2, Fig. 2A, Fig. 2B, and in a subsequent manufacturing stage, several dielectric layers 36, 38, 40 are formed sequentially to create a layer stack over the waveguide cores 12, 14. In the layer stack, dielectric layer 36 is arranged over dielectric layer 16, dielectric layer 38 over dielectric layer 36, and dielectric layer 40 over dielectric layer 38. The waveguide cores 12, 14 are embedded or embedded in the dielectric material of dielectric layer 36, which acts as a lateral sheath. Dielectric layer 36 can consist of a dielectric material, e.g., silicon dioxide, applied by chemical vapor deposition and flattened, e.g., by chemical-mechanical polishing to remove the topography. Dielectric layer 38 can consist of a dielectric material, e.g.,Silicon dioxide is formed, which is deposited over the dielectric layer 36 by chemical vapor deposition or atomic layer deposition. The dielectric layer 40 can be formed from a dielectric material, such as silicon nitride, which is deposited over the dielectric layer 38 by chemical vapor deposition or atomic layer deposition.

[0016] The dielectric layer 40 can be structured by lithography and etching processes. In this context, the dielectric layer 40 can be completely removed from the coupling region 18, masked, and retained over the input region 17 and the output region 19, and can be shaped to have corresponding conical sections 43, each arranged over the conical sections 26, 27, 28, 29. The conical sections 43 taper in the same direction as the conical portion of the conical sections 26, 28 of the waveguide core 12 and the conical sections 27, 29 of the waveguide core 14. In one embodiment, the conical sections 43 can be wider along their respective lengths than the conical sections 26, 28 of the waveguide core 12 and the conical sections 27, 29 of the waveguide core 14.The dielectric layer 40, which may have a higher refractive index than the dielectric layers 36 and 38, is absent in the coupling region 18 above section 20 of the waveguide core 12 and section 21 of the waveguide core 14. The conical sections 43 may have a geometric shape that varies along their respective lengths based on a linear function. In an alternative embodiment, the conical sections 43 may have a geometric shape that varies along their respective lengths based on a nonlinear function, such as a quadratic, parabolic, or exponential function.

[0017] With regard to the Fig. 5, Fig. 6, Fig. 6A, Fig. 6B, in which the same reference signs refer to the same features in the Fig. 3, Fig. 4, Fig. 4A, Fig. In a subsequent manufacturing phase, a dielectric layer 41 is formed over the structured dielectric layer 40. The dielectric layer 41 can be made of a dielectric material, such as silicon dioxide, which is deposited over the dielectric layer 40 by chemical vapor deposition or atomic layer deposition and is, for example, flattened by chemical-mechanical polishing to remove the topography.

[0018] Waveguide cores 42, 44 are formed on the dielectric layer 41. The waveguide cores 42, 44 can be formed from a layer comprising a dielectric material deposited on the dielectric layer 41 by chemical vapor deposition or atomic layer deposition and then structured by lithography and etching processes. The etching process can be selected to terminate on the dielectric material of the dielectric layer 41. The structured layer can be completely etched to deposit the waveguide cores 42, 44, or alternatively, it can be only partially etched to deposit a thin residual layer or plate on the dielectric layer 41, which is connected to lower parts of the waveguide cores 42, 44. In one embodiment, the waveguide cores 42, 44 can be arranged in direct contact with the dielectric layer 41.The dielectric material from which the waveguide cores 42, 44 are formed can have a refractive index that differs from the refractive index of the semiconductor material from which the waveguide cores 12, 14 are formed. In one embodiment, the dielectric material from which the waveguide cores 42, 44 are formed can be silicon nitride. The waveguide cores 42, 44 can have coplanar or substantially coplanar top and bottom surfaces, a uniform or substantially uniform thickness, and a rectangular or substantially rectangular cross-sectional shape. The conical sections 48, 49, 50, 51 can have a cross-sectional shape that varies along their respective lengths based on a linear function.In an alternative embodiment, the conical sections 48, 49, 50, 51 can have a cross-sectional shape that varies over their respective lengths based on a non-linear function, such as a quadratic, parabolic or exponential function.

[0019] The waveguide cores 42, 44 are structured to have truncated geometric shapes with opposing end pieces, and their truncated geometric shapes can be either identical or substantially identical. The waveguide core 42 comprises a section 46 located in the coupling region 18 above and over the section 20 of the waveguide core 12, as well as conical sections 48, 50 terminating at opposite ends of the section 46. In one embodiment, the section 46 of the waveguide core 42 can be arranged directly above the section 20 of the waveguide core 12 with an overlap. The waveguide core 44 comprises a section 47 located in the coupling region 18 above and over the section 21 of the waveguide core 14, as well as conical sections 49, 51 terminating at opposite ends of the section 47.In one embodiment, the section 47 of the waveguide core 44 can be arranged directly above the section 21 of the waveguide core 14 with an overlap.

[0020] The conical section 48 at one end of the waveguide core 42 is arranged above and over a portion of the conical section 26 of the waveguide core 12, and one of the conical sections 43 may be arranged above a portion of the conical section 26 over which the conical section 48 is not present. The conical section 50 at the opposite end of the waveguide core 42 is arranged above and over a portion of the conical section 28 of the waveguide core 12, and one of the conical sections 43 may be arranged above a portion of the conical section 28 over which the conical section 50 is absent. In one embodiment, the conical sections 43 may not overlap with the conical sections 48 and 50. In another embodiment, the conical sections 43 may not overlap with the conical sections 48 and 50 and may be spaced apart from the conical sections 48 and 50 by a small gap.In one embodiment, the conical sections 43 do not overlap with the conical sections 48, 50 and do not coincide with the conical sections 48, 50 at their respective tips. In another embodiment, the conical section 48 is arranged directly above a portion of the conical section 26 of the waveguide core 12, and the conical section 50 is arranged directly above a portion of the conical section 28 of the waveguide core 12. As used herein, the terms "directly above" and "directly below" mean a lateral arrangement in different planes with complete or substantially complete overlap.

[0021] The conical section 49 at one end of the waveguide core 44 is arranged above and above the conical section 27 of the waveguide core 14, and one of the conical sections 43 may be arranged above a portion of the conical section 27 above which the conical section 49 is not present. The conical section 51 at the opposite end of the waveguide core 44 is arranged above and above the conical section 29 of the waveguide core 14, and one of the conical sections 43 may be arranged above a portion of the conical section 29 above which the conical section 51 is not present. In one embodiment, the conical sections 43 may not overlap with the conical sections 49 and 51. In another embodiment, the conical sections 43 may not overlap the conical sections 49 and 51 and may be spaced apart from them by a small gap.In one embodiment, the conical sections 43 cannot overlap with the conical sections 49, 51 and do not coincide with the conical sections 49, 51 at their respective tips. In one embodiment, the conical section 49 is arranged directly above a portion of the conical section 27 of the waveguide core 14, and the conical section 51 is arranged directly above a portion of the conical section 29 of the waveguide core 14.

[0022] The waveguide core 42 comprises side walls in the form of opposing side surfaces 52, 53, which project from the dielectric layer 41, and the waveguide core 44 comprises side walls in the form of opposing side surfaces 54, 55, which project from the dielectric layer 41. The side surface 52 of section 46 of the waveguide core 42 is arranged in the coupling region 18 adjacent to the side surface 54 of section 47 of the waveguide core 44. In one embodiment, the widths w2 of sections 46, 47 can be constant over their respective lengths and greater than the respective widths w1 of sections 20, 21 ( Fig. 2) In one embodiment, the waveguide cores 42, 44 and the waveguide cores 12, 14 can have the same thickness. In another embodiment, the waveguide cores 42, 44 and the waveguide cores 12, 14 can have different thicknesses.

[0023] Section 46 of the waveguide core 42 extends longitudinally along a longitudinal axis 56, and section 47 of the waveguide core 44 extends longitudinally along a longitudinal axis 58. Section 46 is arranged longitudinally between the conical section 48 and the conical section 50, and section 47 is arranged longitudinally between the conical section 49 and the conical section 51. The longitudinal axis 56 of the waveguide core 42 can be arranged parallel to the longitudinal axis 58 of the waveguide core 44. Section 46 of the waveguide core 42 is laterally spaced from section 47 of the waveguide core 44. The side surface 52 of section 46 of the waveguide core 42 can be arranged adjacent to and parallel with the side surface 54 of section 47 of the waveguide core 44.The side surfaces 52 and 54 can be separated in the coupling area 18 by a gap which can be uniform within the coupling area 18.

[0024] The waveguide cores 42, 44 can be laterally spaced by an offset distance d2, which can be measured as a lateral offset between the longitudinal axes 56, 58. The waveguide cores 42, 44, which terminate at their opposite ends, are not present in the input region 17 and in the output region 19. The offset distance d2 can be equal to or substantially equal to the offset distance d1 ( Fig. 1) In one embodiment, the waveguide core 42 can be centered or substantially centered over the waveguide core 12 and the waveguide core 44 can be centered or substantially centered over the waveguide core 14.

[0025] With reference to Fig. 7, in which identical reference signs refer to identical features in Fig. In a subsequent manufacturing phase, a dielectric layer 60 of a contact plane is formed over the waveguide cores 42, 44 by middle-of-line processing. The dielectric layer 60 can be formed from a dielectric material, such as silicon dioxide, which is deposited by chemical vapor deposition using ozone and tetraethyl orthosilicate (TEOS) as the reactant. In the representative embodiment, the waveguide cores 42, 44 are embedded in the dielectric material of the dielectric layer 60.

[0026] A back-end-of-line stack, generally designated by reference numeral 62, is formed by a back-end-of-line (BEOL) processing over the dielectric layer 60 and the structure 10. The back-end-of-line stack 62 may include one or more dielectric intermediate layers 64 formed from one or more dielectric materials, such as silicon dioxide.

[0027] With regard to the Fig. 8, Fig. 8A, Fig. 8B and according to alternative embodiments of the invention, the waveguide cores 42, 44 of the structure 10 can be formed from a material that is not a dielectric material. In one embodiment, the waveguide cores 42, 44 can be formed from a polycrystalline semiconductor material, such as polycrystalline silicon (i.e., polysilicon), which is deposited in a layer on the dielectric layer 38 and then shaped by lithography and etching processes. The etching process used to form the waveguide cores 42, 44 can be selected such that it terminates on the dielectric material of the dielectric layer 38. The dielectric layers 40 and 41 are formed in reverse order after the waveguide core 44 has been structured. For this reason, the dielectric layers 40 and 41 overlap with the waveguide cores 42, 44.The dielectric layer 38 is not structured and for this reason the dielectric layer 38 is present both in the coupling region 18 and in other regions of the structure 10.

[0028] With regard to the Fig. 9, Fig. 9A, Fig. 9B and according to alternative embodiments of the invention, the structure 10 can be modified such that the waveguide cores 42, 44 are arranged below and below the waveguide cores 12, 14, and the materials forming the waveguide cores 12, 14 and the waveguide cores 42, 44 can be interchanged. For example, the waveguide cores 12, 14 can be formed from a dielectric material, such as silicon nitride, which is deposited on the dielectric layer 38 and patterned by lithography and etching. The waveguide cores 42, 44 can be formed from a single-crystal semiconductor material, such as the single-crystal semiconductor material of the device layer of an SOI wafer, which is patterned by lithography and etching. In the representative embodiment, the dielectric layer 38 is not present in the structure 10.

[0029] With regard to the Fig. 10, Fig. 10A, Fig. According to Figure 10B and alternative embodiments of the invention, the structure 10 can be modified such that neither the waveguide cores 12, 14 nor the waveguide cores 42, 44 are formed from a single-crystal semiconductor material. For example, the waveguide cores 12, 14 can be formed from a dielectric material, such as silicon nitride, which is deposited on the dielectric layer 38 and structured by lithography and etching. The waveguide cores 42, 44 can also be formed from a dielectric material, such as silicon nitride, which is deposited on the dielectric layer 38 and structured by lithography and etching. A dielectric layer 66, which can be formed from silicon dioxide, can be formed over the waveguide cores 12, 14 before the waveguide cores 42, 44 are formed.In an alternative embodiment, the waveguide cores 12, 14 can be formed above and above the waveguide cores 42, 44 instead of below and below the waveguide cores 42, 44.

[0030] With reference to Fig. 11 and according to alternative embodiments of the invention, the structure 10 can be modified to include more than two sets of stacked waveguide cores within the coupling area 18. For example, the structure 10 can be Fig. 8, Fig. 8A, Fig.8B is modified such that a waveguide core 42a is added above the waveguide core 42 and a waveguide core 44a is added above the waveguide core 44. The waveguide cores 42a, 44a can be geometrically similar to or identical with the geometric shapes of the waveguide cores 42, 44. In this respect, the waveguide cores 42a, 44a can be truncated similarly to the waveguide cores 42, 44 and have corresponding sections 46a, 47a arranged above and above the sections 46, 47 of the waveguide cores 42, 44. In one embodiment, the section 46a can be arranged directly above and above the section 46 of the waveguide core 42 and the section 20 of the waveguide core 12. In one embodiment, section 47a can be arranged directly above and above section 47 of the waveguide core 44 and section 21 of the waveguide core 14, respectively.In one embodiment, the additional waveguide cores 42a, 44a can be made of silicon nitride. In alternative embodiments, the added waveguide cores 42a, 44a can be made of a different material. In alternative embodiments, two or more of the pairs of waveguide cores 12, 14, waveguide cores 42, 44, and waveguide cores 42a, 44a can be made of the same material.

[0031] Structure 10, in any of its embodiments described herein, can be integrated into a photonic chip comprising electronic components and additional optical components formed on the same chip. The electronic components can, for example, include field-effect transistors fabricated by CMOS front-end-of-line (FEOL) processing.

[0032] In each of the embodiments described here, structure 10 can function as a directional coupler without polarization sensitivity. In this respect, structure 10 can be used to split or combine optical signals propagating in either the transverse electrical (TE) or transverse magnetic (TM) mode by adjusting the coupling lengths and coupling efficiencies of both the TE and TM modes. Consequently, the polarization-insensitive structure 10 can be used on a photonic chip to split or combine optical signals propagating in the transverse electrical (TE) mode or optical signals propagating in the transverse magnetic (TM) mode.

[0033] The processes described above are used in the fabrication of integrated circuits. The resulting integrated circuit chips can be distributed by the manufacturer in the form of a raw wafer (e.g., a single wafer containing multiple unpackaged chips), as a bare chip, or in packaged form. The chip can be integrated with other chips, discrete circuit elements, and / or other signal processing devices as part of an intermediate or final product. The final product can be any product that incorporates integrated circuit chips, such as computer products with a central processing unit or smartphones.

[0034] References in this document to terms modified by imprecise language, such as "approximately," "about," and "essentially," are not limited to the exact value stated. The imprecise language may correspond to the accuracy of an instrument used to measure the value and, unless otherwise specified depending on the accuracy of the instrument, may indicate + / - 10% of the stated value(s).

[0035] References to terms such as "vertical," "horizontal," etc., serve only as examples and not as limitations to establish a frame of reference. The term "horizontal," as used here, is defined as a plane parallel to a conventional plane of a semiconductor substrate, regardless of its actual three-dimensional spatial orientation. The terms "vertical" and "normal" refer to a direction perpendicular to the horizontal direction, as defined above. The term "lateral" refers to a direction within the horizontal plane.

[0036] A feature that is "connected" or "coupled" to another feature can be directly connected or coupled to the other feature, or one or more intervening features can be present. A feature can be "directly connected" or "directly coupled" to another feature if no intervening features are present. A feature can be "indirectly connected" or "indirectly coupled" to another feature if at least one intervening feature is present. A feature that is "on" another feature or "in contact" with another feature can be located directly on the other feature or be in direct contact with the other feature. Alternatively, one or more intervening features can be present.A feature can be "directly on" another feature or "in direct contact with" another feature if no intervening features exist. A feature can be "indirectly on" another feature or "in indirect contact with" another feature if at least one intervening feature exists.

[0037] The description of the various embodiments of the present invention is provided for illustrative purposes only and is not intended to be exhaustive or to limit the described embodiments. Many modifications and variations are apparent to those skilled in the art without altering the scope and essence of the described embodiments. The terminology used herein has been chosen to best explain the principles of the embodiments, their practical application, or the technical improvements over technologies available on the market, or to enable those other than those skilled in the art to understand the embodiments described herein.

Claims

[1] Structure (10) for a directional coupler, wherein the structure (10) comprises: a first waveguide core (12) with a first section (20); a second waveguide core (14) with a second section (21) which is arranged laterally adjacent to the first section (20); a third waveguide core (42) comprising a first conical section (48), a second conical section (50) and a third section (46) arranged longitudinally between the first conical section (48) and the second conical section (50); and a fourth waveguide core (44) comprising a first conical section (49), a second conical section (51) and a fourth section (47) arranged longitudinally between the first conical section (49) and the second conical section (51), wherein the fourth section (47) is located laterally next to the third section (46), wherein the third section (46) is arranged above the first section (20) and the fourth section (47) is arranged above the second section (21), wherein the first waveguide core (12) has a first conical section (26) connected to a first end of the first section (20) and a second conical section (28) connected to a second end of the first section (20), and the second waveguide core (14) has a first conical section (27) connected to a first end of the second section (21) and a second conical section (29) connected to a second end of the second section (21), wherein the first conical section (48) of the third waveguide core (42) is arranged over the first conical section (26) of the first waveguide core (12), the second conical section (50) of the third waveguide core (42) is arranged over the second conical section (28) of the first waveguide core (12), the first conical section (49) of the fourth waveguide core (44) is arranged over the first conical section (27) of the second waveguide core (14), and the second conical section (51) of the fourth waveguide core (44) is arranged over the second conical section (29) of the second waveguide core (14). [2] Structure (10) according to claim 1, wherein the first waveguide core (12) and the second waveguide core (14) are formed from a first material and the third waveguide core (42) and the fourth waveguide core (44) are formed from a second material with a different composition than the first material. [3] Structure (10) according to claim 1, wherein the first waveguide core (12) and the second waveguide core (14) are formed from a first material and the third waveguide core (42) and the fourth waveguide core (44) are formed from the first material. [4] Structure (10) according to claim 1, wherein the first conical section (48) of the third waveguide core (42) terminates at a first end of the third section (46), the second conical section (50) of the third waveguide core (42) terminates at a second end of the third section (46), the first conical section (49) of the fourth waveguide core (44) terminates at a first end of the fourth section (47) and the second conical section (51) of the fourth waveguide core (44) terminates at a second end of the fourth section (47). [5] Structure (10) according to claim 1, wherein the first waveguide core (12) has a first plurality of bends (22) coupled to the first section (20) by the first conical section (26) of the first waveguide core (12), wherein the second waveguide core (14) has a second plurality of bends (23) coupled to the second section (21) by the first conical section (27) of the second waveguide core (14), and further comprising: a dielectric layer (40) over the first plurality of bends (22) and the second plurality of bends (23), wherein the dielectric layer comprises a first conical section (43) between the first conical section (26) of the first waveguide core (12) and the first conical section (48) of the third waveguide core (42), and the dielectric layer (40) comprises a second conical section (43) between the first conical section (27) of the second waveguide core (14) and the first conical section (49) of the fourth waveguide core (44). [6] Structure (10) according to claim 5, wherein the dielectric layer (40) is formed from a first material and the third waveguide core (42) and the fourth waveguide core (44) are formed from the first material. [7] Structure (10) according to claim 1, wherein the third section (46) and the fourth section (47) are laterally spaced apart from each other by a first center distance, the first section (20) and the second section (21) are laterally spaced apart from each other by a second center distance and the first center distance is substantially equal to the second center distance. [8] Structure (10) according to claim 1, wherein the first conical section (48) of the third waveguide core (42) is directly connected to a first end of the third section (46), the second conical section (50) of the third waveguide core (42) is directly connected to a second end of the third section (46), the first conical section (49) of the fourth waveguide core (44) is directly connected to a first end of the fourth section (47), and the second conical section (51) of the fourth waveguide core (44) is directly connected to a second end of the fourth section (47). [9] Structure (10) according to claim 1, wherein the third section (46) is arranged directly above the first section (20) and the fourth section (47) is arranged directly above the second section (21). [10] Method for manufacturing a structure (10) for a directional coupler, the method comprising: forming a first waveguide core (12) with a first section (20); a formation of a second waveguide core (14) with a second section (21) located laterally next to the first section (20) of the first waveguide core (12); a formation of a third waveguide core (42) with a first conical section (48), a second conical section (50) and a third section (46) arranged longitudinally between the first conical section (48) and the second conical section (50); and forming a fourth waveguide core (44) with a first conical section (49), a second conical section (51) and a fourth section (47) arranged longitudinally between the first conical section (49) and the second conical section (51), wherein the fourth section (47) is arranged laterally next to the third section (46), wherein the third section (46) is arranged above the first section (20) and the fourth section (47) is arranged above the second section (21), wherein the first waveguide core (12) has a first conical section (26) connected to a first end of the first section (20) and a second conical section (28) connected to a second end of the first section (20), and the second waveguide core (14) has a first conical section (27) connected to a first end of the second section (21), and has a second conical section (29) connected to a second end of the second section (21), wherein the first conical section (48) of the third waveguide core (42) is arranged over the first conical section (26) of the first waveguide core (12), the second conical section (50) of the third waveguide core (42) is arranged over the second conical section (28) of the first waveguide core (12), the first conical section (49) of the fourth waveguide core (44) is arranged over the first conical section (27) of the second waveguide core (14), and the second conical section (51) of the fourth waveguide core (44) is arranged over the second conical section (29) of the second waveguide core (14). [11] Method according to claim 10, wherein the first conical section (48) of the third waveguide core (42) terminates a first end of the third section (46), the second conical section (50) of the third waveguide core (42) terminates a second end of the third section (46), the first conical section (49) of the fourth waveguide core (44) terminates a first end of the fourth section (47) and the second conical section (51) of the fourth waveguide core (44) terminates a second end of the fourth section (47).

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