Image device and methods of forming the same

A method of forming an image sensor device, the method comprising:

• providing a substrate having a front surface and a back surface, and a pixel region and a periphery region;
• forming a patterned hard mask layer over the front surface of the substrate, wherein the patterned hard mask layer has a first opening in the periphery region, and a second opening in the pixel region;
• etching a trench in the front surface of the substrate in the periphery region through the first opening;
• filling the trench, the first opening and the second opening with a material;
• removing the material in the second opening over the pixel region, while leaving the material intact in the trench;
• and
• implanting a dopant through the second opening to form a doped isolation feature in the pixel region.

A method of forming an image sensor device, the method comprising:

• providing a substrate having a front surface and a back surface, and a pixel region and a periphery region;
• forming a patterned hard mask layer over the front surface of the substrate, wherein the patterned hard mask layer has a first opening in the periphery region, and a second opening in the pixel region;
• forming a first patterned photoresist covering the patterned hard mask layer in the pixel region and exposing the patterned hard mask in the periphery region;
• etching a trench through the first opening;
• filling the trench, the first opening and the second opening with a material;
• forming a second patterned photoresist over the patterned hard mask layer covering the periphery region and exposing the pixel region;
• removing the material in the second opening;
• and
• implanting a dopant through the second opening into the substrate to form a doped isolation feature in the pixel region.