CMOS image sensor having impurity diffusion region separated from isolation region
View Patent ↗A CMOS image sensor and a manufacturing method are disclosed. The gates of the transistors are formed in the active region of the unit pixel, and a diffusion region for the photo diode is defined by an ion implantation of impurities to the semiconductor substrate. The patterns of the photoresist that are the masking layer against ion implantation are formed on the semiconductor substrate in such a manner that they have the boundary portion of the isolation layer so as not to make the boundary of the defined photo diode contact with the boundary of the isolation layer. Damages by an ion implantation of impurities at the boundary portion between the diffusion region for the photo diode and the isolation layer are prevented, which reduces dark current of the COMS image sensor.
1. A CMOS image sensor comprising:
a semiconductor substrate including an epitaxial layer having a shallow trench-type isolation region and an active region for a unit pixel;
a transistor formed on said semiconductor substrate;
an impurity diffusion region for a photo diode formed in a portion of the active region and separated from the isolation region, the impurity diffusion region comprising:
a n − type diffusion region formed in the active region: and
a p 0 type diffusion region formed on the n − type diffusion region; and
a non-diffusion region, between the isolation region and both the n − type diffusion region and the p 0 type diffusion region of the impurity diffusion region, in which impurities are not diffused, wherein the non-diffusion region is formed on at least two sides of the impurity diffusion region.
2. The CMOS image sensor according to claim 1 , wherein said semiconductor substrate is a P ++ type silicon substrate having a p − type epitaxial layer.
3. The CMOS image sensor as claimed in claim 2 , wherein the p 0 type diffusion region is formed so as to reduce dark current generated on the surface of said semiconductor substrate.