US Patent 11333827 Protective ring structure to increase waveguide performance

Various embodiments of the present disclosure are directed towards an integrated chip including a protective ring structure overlying a grating coupler structure. A waveguide structure is disposed within a semiconductor substrate and comprises the grating coupler structure. An interconnect structure overlies the semiconductor substrate. The interconnect structure includes a contact etch stop layer (CESL) and a conductive contact over the semiconductor substrate. The conductive contact extends through the CESL. The protective ring structure extends through the CESL and has an upper surface aligned with an upper surface of the conductive contact.