Full backside deep trench isolation structure for a semiconductor pixel sensor array

A method, comprising:

• forming a plurality of polysilicon wells over a first side of a semiconductor layer of a pixel sensor array;
• forming an oxide layer on the first side of the semiconductor layer and on the polysilicon wells;
• forming sidewall spacers around sidewalls of the polysilicon wells;
• forming a contact etch stop layer (CESL) over the oxide layer and over the sidewall spacers;
• forming a plurality of trenches through the semiconductor layer and into the polysilicon wells,
• wherein the plurality of trenches are formed from a second side of the semiconductor layer to the first side of the semiconductor layer;
• and
• forming a backside deep trench isolation (BDTI) structure in the plurality of trenches.

A pixel sensor array, comprising:

• a plurality of pixel sensors;
• and
• a backside deep trench isolation (BDTI) structure that is included fully through a semiconductor layer of the pixel sensor array between a front side of the semiconductor layer and a backside of the semiconductor layer,
• wherein a bottom portion of the BDTI structure is surrounded by one or more dielectric layers under the semiconductor layer, and
• wherein a ring-shaped polysilicon well is included around the bottom portion of the BDTI structure in the one or more dielectric layers.