Image sensor device and methods of forming the same

A method for fabricating semiconductor devices, comprising:

• forming, over a first surface of a semiconductor layer, a plurality of pixels;
• forming a plurality of transistors over the first surface of the semiconductor layer;
• forming a metallization layer over the plurality of transistors;
• forming, through a second surface of the semiconductor layer opposite to the first surface, a recess laterally separated from the plurality of pixels;
• forming a spacer layer covering corners the recess and exposing a bottom surface forming an oxide layer over the spacer layer;
• forming, in the recess, a pad structure electrically coupled to the metallization layer;
• filling a remaining portion of the recess with a dielectric material;
• and
• forming a bump structure extending through the dielectric material to be in contact with the pad structure.

A method for fabricating semiconductor devices, comprising:

• forming, over a first surface of a semiconductor layer, a plurality of pixels within a first region of the semiconductor layer;
• forming a device layer over the first surface of the semiconductor layer;
• forming a plurality of metallization layers over the device layer;
• forming, through a second surface of the semiconductor layer opposite to the first surface, a plurality of recesses within a second region of the semiconductor layer;
• forming a plurality of tapered spacer layers, each of the tapered spacer layers covering only corners of a corresponding one of the plurality of recesses;
• forming a plurality of pad structures in the plurality of recesses, respectively,
• wherein each of the pad structures is electrically coupled to a corresponding one of the metallization layers;
• filling a remaining portion of each of the plurality of recesses with a dielectric material;
• and
• forming a bump structure extending through the dielectric material to be in contact with a corresponding pad structure of the pad structures.