Deep trench isolation structure and methods for fabrication thereof

A method, comprising:

• doping a semiconductor substrate to form a doped region with a first dopant;
• doping a gap region around the doped region with a second dopant;
• forming a pixel element over the doped region and the gap region from a front surface of the semiconductor substrate;
• forming an interconnect structure over the pixel element;
• etching a deep isolation trench in the gap region from a back surface of the semiconductor substrate;
• depositing a nitrogen containing layer on sidewalls of the deep isolation trench;
• depositing a high-k dielectric layer on the nitrogen containing layer;
• treating the high-k dielectric layer with an oxygen source to increase interstitial oxygen in the high-k dielectric layer;
• depositing a filling material on the high-k dielectric layer to fill the deep isolation trench;
• forming a color filter on the back surface of the semiconductor substrate;
• and
• forming a micro lens on the color filter.

A structure, comprising:

• a plurality of pixel elements formed in and on a semiconductor substrate;
• a deep trench isolation (DTI) structure formed in the semiconductor substrate, wherein the DTI structure separates individual pixel elements, and the DTI structure comprises:
• a defect repairing layer in contact with the semiconductor substrate, wherein the defect repairing layer contains nitrogen or hydrogen;
• a hole accumulation layer in contact with the defect repairing layer, wherein the hole accumulation layer comprises a high-k dielectric material having an areal oxygen density greater than an areal oxygen density of silicon oxide, and
• a filling material in contact with the hole accumulation layer.