US Patent 11961866 Method of making an image sensor with sidewall protection

A method of forming an image sensor includes forming a photodiode within a semiconductor substrate. The method further includes disposing an interconnect structure over the semiconductor substrate. The interconnect structure includes a contact etch stop layer (CESL) over the photodiode; and a plurality of dielectric layers over the CESL, wherein at least one dielectric layer of the plurality of dielectric layers comprises a low dielectric constant (low-k) material. The method further includes patterning at least the plurality of dielectric layers, wherein patterning at least the plurality of dielectric layers comprises defining an opening above an active region of the photodiode. The method further includes depositing a cap layer on sidewalls of the opening, wherein the cap layer includes a dielectric material having a higher moisture resistance than the low-k dielectric material.