Deep Trench Isolation Structures Resistant to Cracking

A method comprising:

• forming Shallow Trench Isolation (STI) regions extending from a first surface of a semiconductor substrate into the semiconductor substrate;
• forming pixel units between the STI regions;
• forming Deep Trench Isolation (DTI) regions extending from a second surface of a semiconductor substrate toward the STI regions, wherein the forming the DTI regions comprises:
• etching the semiconductor substrate to form trenches extending from the second surface of the semiconductor substrate into the semiconductor substrate;
• forming a dielectric layer extending into the trenches;
• filling a high-reflectivity metal layer extending into the trenches and over the dielectric layer, wherein the high-reflectivity metal layer encloses a void therein;
• and
• planarizing the high-reflectivity metal layer and the dielectric layer to form the DTI regions;
• and
• forming micro lenses aligned to the pixel units.

A structure comprising:

• a Deep Trench Isolation (DTI) region extending from a top surface of a semiconductor substrate into the semiconductor substrate, wherein the DTI region comprises:
• a dielectric layer extending into the semiconductor substrate;
• and
• a high-reflectivity metal layer between opposite portions of the dielectric layer, wherein the high-reflectivity metal layer encloses a void therein;
• a diffusion barrier layer over the DTI regions and the semiconductor substrate;
• pixel units with portions in the semiconductor substrate;
• color filters overlapping the pixel units;
• and
• micro lenses overlapping the color filters.