Semiconductor devices for image sensing

A semiconductor device, comprising:

• a semiconductor substrate;
• a plurality of ring-shaped deep trench isolation (DTI) structures extending from a first side of the substrate to within the substrate;
• a plurality of image sensing elements disposed within the semiconductor substrate and disposed within the plurality of ring-shaped DTI structures, respectively, such that the ring-shaped DTI structures separate adjacent image sensing elements from one another;
• a plurality of protrusions arranged along the first side of the substrate, the plurality of protrusions being disposed over an image sensing element and being laterally surrounded by a ring-shaped DTI structure, the plurality of protrusions being periodically spaced and being substantially identical to one another and having a characteristic dimension;
• and
• wherein an innermost surface of the ring-shaped DTI structure is spaced apart from an outer border of the plurality of protrusions by a predetermined reflective length that is based on the characteristic dimension of the plurality of protrusions.

A method of forming an image sensor integrated chip, comprising:

• providing a substrate having image sensors formed therein, the image sensors being formed within separate pixel regions;
• performing a first etching process on a first side of a substrate to define a plurality of protrusions formed in a periodically repeating pattern within the pixel region, the plurality of protrusions having sides and peaks and being pyramidal or cone shaped, and having an outer border;
• performing a second etching process on the first side of the substrate to define a plurality of trenches extending within the substrate, wherein an inner surface of the plurality of trenches is laterally spaced apart from the outer border by a reflective length based on a distance between nearest repeating peaks of the plurality of protrusions;
• forming one or more absorption enhancement layers over and between the plurality of protrusions and extending into the plurality of trenches;
• performing a third etching process on the one or more absorption enhancement layers to form cavities extending to within the plurality of trenches;
• and
• forming reflective elements within the cavities, the forming comprising depositing a metal, wherein the metal is separated from the substrate by one or more dielectric materials.