Method for passivating full front-side deep trench isolation structure

A method for forming a deep trench isolation structure for a CMOS image sensor, comprising:

• forming a trench in a semiconductor substrate, wherein the trench extends from a first side of the semiconductor substrate toward a second side of the semiconductor substrate, wherein the trench has an opening on the first side and a bottom and sides of the trench are formed of the semiconductor substrate;
• depositing a conformal layer of boron (B)-doped dielectric at least on the bottom and sides of the trench, wherein the conformal layer of B-doped dielectric is less than half a width of the trench to leave a depthwise recess in the trench;
• depositing a second material at least on the conformal layer of B-doped dielectric in the trench, wherein the second material fills the recess in the trench to at least the first side;
• and
• annealing the conformal layer of B-doped dielectric to drive boron from the conformal layer of B-doped dielectric to the semiconductor substrate and forms a B-doped region of the semiconductor substrate corresponding to a passivation layer disposed next to the conformal layer of B-doped dielectric, and the conformal layer of B-doped dielectric having negative fixed charges, wherein the second material comprises doped polysilicon and the annealing of the conformal layer of B-doped dielectric further electrically activates the doped polysilicon.