Solid-state imaging device and electronic device
View Patent ↗A solid-state imaging device including an imaging region having a plurality of pixels arranged in a two-dimensional matrix and a peripheral circuit detecting output signals from the pixels. An impurity concentration in a transistor of each pixel is lower than an impurity concentration in a transistor of the peripheral circuit. Further, the impurity concentration of a semiconductor well region under a floating diffusion portion in the pixel is set to be lower than the impurity concentration of a semiconductor well region under a transistor portion at the subsequent stage of the floating diffusion portion.
1. A method of producing a solid-state imaging device, comprising the steps of:
forming in a cell region in which a unit pixel cell or pixel-sharing cell of a first-conductivity-type semiconductor substrate is to be formed, a first second-conductivity-type semiconductor well region of a photoelectric conversion portion formation region, a second second-conductivity-type semiconductor well region of a floating diffusion portion formation region, and a third second-conductivity-type semiconductor well region of a pixel transistor portion formation region, wherein an impurity concentration of the second second-conductivity-type semiconductor well region is made lower than an impurity concentration of the third second-conductivity-type semiconductor well region;
forming a photoelectric conversion portion in the first second-conductivity-type semiconductor well region;
forming a floating diffusion portion in the second second-conductivity-type semiconductor well region, and a first-conductivity-type diffusion region of a pixel transistor portion at the subsequent stage of the floating diffusion portion in the third second-conductivity-type semiconductor well region;
ion implanting a first second-conductivity-type impurity having a concentration peak in a deep part to a whole surface of the cell region;
ion implanting a second second-conductivity-type impurity having a concentration peak in an intermediate part between the deep part and the surface side to a floating diffusion portion formation region and a pixel transistor formation region at the subsequent stage of the floating diffusion portion except the photoelectric conversion portion formation region of the cell region; and
ion implanting a third second-conductivity-type impurity having a concentration peak at the surface side only to the pixel transistor portion formation region of the cell region, wherein
the first second-conductivity-type semiconductor well region is formed in the photoelectric conversion portion formation region, the third second-conductivity-type semiconductor well region is formed in the pixel transistor portion formation region, and the second second-conductivity-type semiconductor well region in the impurity concentration lower than the impurity concentration of the third second-conductivity-type semiconductor well region is formed in the floating diffusion portion formation region.
2. A method of producing a solid-state imaging device according to claim 1 , wherein
the first-conductivity-type diffusion region of the floating diffusion portion and the first-conductivity-type diffusion region of the pixel transistor portion are formed at a same time in a same impurity concentration.
3. A method of producing a solid-state imaging device according to claim 1 , wherein
the first-conductivity-type diffusion region of the floating diffusion portion is formed in an impurity concentration lower than an impurity concentration of the first-conductivity-type diffusion region of the pixel transistor portion.