Fluorine passivation in a pixel sensor

A method, comprising:

• forming a drain region and a drain extension region in a substrate of a pixel sensor, wherein the drain extension region is adjacent to the drain region;
• forming a photodiode region in the substrate;
• forming a floating diffusion region in the substrate;
• forming a transfer gate contact in the substrate between the photodiode region and the floating diffusion region,
• wherein, in a cross-section view of the pixel sensor:
• the drain extension region of the pixel sensor extends beyond the transfer gate contact in the substrate, and
• the drain extension region and the transfer gate contact extend to a same depth in the substrate;
• and
• forming a first plurality of silicon-fluorine bonds at an interface between the transfer gate contact and the substrate.

A method of forming a pixel sensor, comprising:

• forming an oxide layer that lines a trench of a substrate and that contacts a floating diffusion region, wherein a bottom surface of the trench and sidewalls of the trench include a plurality of silicon-fluorine bonds, wherein:
• the floating diffusion region includes a drain region and a drain extension region, wherein the drain extension region is adjacent to the drain extension region, and
• in a cross-section view of the pixel sensor:
• the drain extension region of the pixel sensor extends beyond the trench in the substrate, and
• the drain extension region and the trench extend to a same depth in the substrate;
• and
• forming a polysilicon layer in the trench.