# US 2025/0085476 A1 · Photonic device and method of making > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0085476 A1 - Document ID: US20250085476A1 - Status: Published application - Kind: A1 - Application number: 18/954,697 - Filed: 2024-11-21 - Published: 2025-03-13 - Earliest claimed: 2021-08-26 - Assignees: Taiwan Semiconductor Manufacturing Company, Ltd. - Applicants: Taiwan Semiconductor Manufacturing Company, Ltd. - Inventors: Chien-Ying WU; Yuehying LEE; Sui-Ying HSU; Chen-Hao HUANG; Chien-Chang LEE; Chia-Ping LAI - Web page: https://patentgrep.com/patent/US20250085476A1 ## CPC - G02B 6/13: Integrated optical circuits characterised by the manufacturing method - G02B 6/12: of the integrated circuit kind (electric integrated circuits H10B, H10D84/00 - H10D89/00, H10F19/00, H10F39/00, H10H29/00, H10K19/00, H10K39/00, H10K59/00, H10N19/00, H10N39/00, H10N59/00, H10N69/00, H10N79/00, H10N89/00) - G02B 6/136: by etching - G02B 6/30: for use between fibre and thin-film device - G02B 6/34: utilising prism or grating {(G02B6/293 takes precedence)} - G02B 6/1347: {using ion implantation (ion implantation in glass C03C23/0055; ion implantation in general C23C)} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A photonic device includes a silicon layer, wherein the silicon layer includes a waveguide portion. The photonic device further includes a cladding layer over the waveguide portion, wherein the cladding layer partially exposes a surface of the waveguide portion. The photonic device further includes a low refractive index layer in direct contact with the cladding layer, wherein the low refractive index layer comprises silicon oxide, silicon carbide, silicon oxynitride, silicon carbon oxynitride, aluminum oxide or hafnium oxide. The photonic device further includes an interconnect structure over the low refractive index layer. ## Claims ### Claim 1 A photonic device comprising: a silicon layer, wherein the silicon layer includes a waveguide portion; a cladding layer over the waveguide portion, wherein the cladding layer partially exposes a surface of the waveguide portion; a low refractive index layer in direct contact with the cladding layer, wherein the low refractive index layer comprises silicon oxide, silicon carbide, silicon oxynitride, silicon carbon oxynitride, aluminum oxide or hafnium oxide; and an interconnect structure over the low refractive index layer. ### Claim 2 (depends on 1) The photonic device of claim 1, wherein the waveguide portion comprises a grating. ### Claim 3 (depends on 2) The photonic device of claim 2, further comprising a cavity in the interconnect structure, wherein the cavity overlaps with the grating. ### Claim 4 (depends on 3) The photonic device of claim 3, wherein the cavity extends through less than an entirety of the interconnect structure. ### Claim 5 (depends on 1) The photonic device of claim 1, further comprising an interlayer dielectric (ILD) between the interconnect structure and the low refractive index layer. ### Claim 6 (depends on 1) The photonic device of claim 1, wherein the waveguide portion includes a multimode waveguide. ### Claim 7 (depends on 1) The photonic device of claim 1, wherein the cladding layer is between a portion of the waveguide portion and the low refractive index layer. ### Claim 8 (depends on 1) The photonic device of claim 1, wherein the low refractive index layer has a refractive index less than 2.0. ### Claim 9 (depends on 1) The photonic device of claim 1, wherein the low refractive index layer directly contacts a topmost surface of the cladding layer. ### Claim 10 A photonic device comprising: a silicon layer, wherein the silicon layer includes a waveguide portion; a cladding layer over the waveguide portion, wherein the cladding layer partially exposes a surface of the waveguide portion; a low refractive index layer in direct contact with the cladding layer, wherein the low refractive index layer comprises silicon oxide, silicon carbide, silicon oxynitride, silicon carbon oxynitride, aluminum oxide or hafnium oxide; and a contact etch stop layer (CESL) directly contacting the cladding layer. ### Claim 11 (depends on 10) The photonic device of claim 10, further comprising an interconnect structure over the low refractive index layer. ### Claim 12 (depends on 10) The photonic device of claim 10, wherein the low refractive index layer is over a portion of the CESL. ### Claim 13 (depends on 10) The photonic device of claim 10, wherein the CESL extends over a topmost surface of the low refractive index layer. ### Claim 14 (depends on 10) The photonic device of claim 10, wherein the silicon layer includes an implant region separated from the waveguide portion. ### Claim 15 (depends on 14) The photonic device of claim 14, wherein the CESL extends over the implant region. ### Claim 16 (depends on 15) The photonic device of claim 15, further comprising a silicide layer between the CESL and the implant region. ### Claim 17 (depends on 15) The photonic device of claim 15, further comprising a conductive element electrically connected to the implant region, wherein the conductive element extends through the CESL. ### Claim 18 (depends on 14) The photonic device of claim 14, wherein the low refractive index layer extends over the implant region. ### Claim 19 (depends on 10) The photonic device of claim 10, wherein the CESL contacts a topmost surface of the cladding layer. ### Claim 20 A method of making a photonic device, the method comprising: depositing a cladding layer over a silicon layer; patterning the cladding layer to expose a first portion of the silicon layer, wherein a second portion of the silicon layer is covered by the patterned cladding layer, and a waveguide portion is in the second portion of the silicon layer; depositing a low refractive index layer over the patterned cladding layer, wherein a refractive index of the low refractive index layer is less than 2.0; and depositing a contact etch stop layer (CESL) over the cladding layer, wherein the CESL directly contacts the cladding layer.