Solid-state image capturing element and electronic information device
A solid-state image capturing element according to the present invention includes a one conductivity type semiconductor substrate; an opposite conductivity type well region formed on the one conductivity type semiconductor substrate; a photodiode section formed on the opposite conductivity type well region, constituted of a plurality of one conductivity type regions with successively different impurity concentrations for complete electric charge transferring; a one conductive drain region capable of reading out signal charges from the photodiode section; and a transfer gate formed above a substrate between the one conductivity drain region and the photodiode section.
1. A solid-state image capturing element, comprising:
a one conductivity type semiconductor substrate;
an opposite conductivity type well region formed on the one conductivity type semiconductor substrate;
a photodiode section formed on the opposite conductivity type well region, constituted of a plurality of one conductivity type regions with successively different impurity concentrations for complete electric charge transferring;
a one conductive drain region capable of reading out signal charges from the photodiode section;
a transfer gate formed above a substrate between the one conductivity drain region and the photodiode section; and
wherein the plurality of one conductivity type regions constituting the photodiode section are constituted of n stages (n being a natural number of 2 or above) of impurity concentration regions, including a first one conductivity type region proximal to the transfer gate; a second one conductivity type region covering the outside of the first one conductivity type region excluding the transfer gate side thereof, . . . and an n th one conductivity type region covering the outside of an (n−1) th one conductivity type region excluding the transfer gate side thereof.
2. A solid-state image capturing element according to claim 1 , wherein each of the plurality of one conductivity type regions has an incrementally and successively lower one conductivity impurity concentration according to the distance from the transfer gate.
3. A solid-state image capturing element according to claim 1 , wherein each of the plurality of one conductivity type regions has an incrementally and successively higher one conductivity impurity concentration according to the distance towards the transfer gate.
4. A solid-state image capturing element according to claim 1 , wherein, in the plurality of one conductivity type regions constituting the photodiode section, a potential inclination is provided incrementally or successively towards the side of an electric charge transferring path below the transfer gate.
5. A solid-state image capturing element according to claim 1 , wherein the n th one conductivity type region covers an (n−1) th one conductivity type region on the outside in a substrate surface direction.
6. A solid-state image capturing element according to claim 1 , wherein the n th one conductivity type region covers an (n−1) th one conductivity type region on the outside in a substrate depth direction.
7. A solid-state image capturing element according to claim 1 , wherein the n th one conductivity type region covers an (n−1) th one conductivity type region on the outside in both substrate surface direction and a substrate depth direction.
8. A solid-state image capturing element according to claim 1 , wherein, when the photodiode section is constituted of a first one conductivity type region and a second one conductivity type region, an impurity concentration N of the first one conductivity type region is set as N=5×10 16 to 1×10 17 cm −3 , and an impurity concentration N−− of the second one conductivity type region is set as N−−=1×10 14 cm −3 .
9. A solid-state image capturing element according to claim 1 , wherein, when the photodiode section is constituted of a first one conductivity type region and a second one conductivity type region, an impurity concentration N of the first one conductivity type region is set as N=5×10 16 to 1×10 17 cm −3 , and an impurity concentration N− of the second one conductivity type region is set as N−=1×10 15 to 1×10 16 cm −3 .
10. A solid-state image capturing element according to claim 1 , wherein, when the photodiode section is constituted of a first one conductivity type region, a second one conductivity type region and a third one conductivity type region, an impurity concentration N of the first one conductivity type region is set as N=5×10 16 to 1×10 17 cm −3 , an impurity concentration N− of the second one conductivity type region is set as N−=1×10 15 to 1×10 16 cm −3 , and an impurity concentration N−− of the third one conductivity type region is set as N−−=1×10 14 cm −3 .
11. A solid-state image capturing element according to claim 1 , wherein when the photodiode section is constituted of a first one conductivity type region, a second one conductivity type region, a third one conductivity type region and a fourth one conductivity type region, an impurity concentration N of the first one conductivity type region is set as N=5×10 16 to 1×10 17 cm −3 , an impurity concentration N1− of the second one conductivity type region is set as N1−=5×10 15 to 1×10 16 cm −3 , an impurity concentration N2−of the third one conductivity type region is set as N2−=5×10 14 to 1×10 15 cm −3 , and an impurity concentration N−− of the fourth one conductivity type region is set as N−−=1×10 14 cm −3 .
12. A solid-state image capturing element according to claim 1 , wherein the size of the photodiode section is between 3×3 μm to 10×10 μm.
13. A solid-state image capturing element according to claim 1 , wherein the impurity concentration of the one conductivity type region of the photodiode section farthest from the transfer gate is equal to the impurity concentration of the one conductivity type semiconductor substrate.
14. A solid-state image capturing element according to claim 1 , wherein two or more kinds of impurity ions are used to form the plurality of one conductivity type regions constituting the photodiode section.
15. A solid-state image capturing element according to claim 14 , wherein, of the plurality of one conductivity type regions constituting the photodiode section, arsenic and phosphorus are implanted as the impurity ions into one of the regions closer to the transfer gate and phosphorus only is implanted as the impurity ion into one of the regions farther away from the transfer gate.
16. A solid-state image capturing element according to claim 1 , further including an opposite conductivity type high concentration surface layer formed above the photodiode section in such a manner to bury the photodiode section.
17. A solid-state image capturing element according to claim 1 , wherein an opposite conductivity type barrier layer is formed between the one conductivity type drain region and the photodiode section, and the transfer gate is formed above the opposite conductivity type barrier layer.
18. An electronic information device including the solid-state image capturing element according to claim 1 used as an image input device in an image capturing section.