CMOS image sensor with buried superlattice layer to reduce crosstalk

A CMOS image sensor comprising:

• a semiconductor substrate having a first conductivity type;
• a superlattice on the semiconductor substrate comprising a plurality of stacked groups of layers, each group of layers comprising a plurality of stacked base semiconductor monolayers defining a base semiconductor portion, and at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions;
• a plurality of laterally adjacent photodiodes on the superlattice and each comprising
• a semiconductor layer on the superlattice and having a first conductivity type dopant and with a lower dopant concentration than the semiconductor substrate,
• a retrograde well extending downward into the semiconductor layer from a surface thereof and having a second conductivity type,
• a first well around a periphery of the retrograde well having the first conductivity type, and
• a second well above the retrograde well having the first conductivity type;
• a respective color filter overlying each of the photodiodes;
• and
• a respective microlens overlying each of the color filters.

A CMOS image sensor comprising:

• a semiconductor substrate having a first conductivity type;
• a superlattice on the semiconductor substrate comprising a plurality of stacked groups of layers, each group of layers comprising a plurality of stacked base silicon monolayers defining a base silicon portion, and at least one oxygen monolayer constrained within a crystal lattice of adjacent base oxygen portions;
• and
• a plurality of laterally adjacent photodiodes on the superlattice and each comprising
• a semiconductor layer on the superlattice and having a first conductivity type dopant and with a lower dopant concentration than the semiconductor substrate,
• a retrograde well extending downward into the semiconductor layer from a surface thereof and having a second conductivity type,
• a first well around a periphery of the retrograde well having the first conductivity type, and
• a second well above the retrograde well having the first conductivity type.