Photoelectric conversion device and imaging system

1. A photoelectric conversion device comprising:

a photoelectric conversion portion in a silicon layer having a light-receiving surface, the photoelectric conversion portion being capable of producing electrons as signal charge carriers from light that has entered through the light-receiving surface,

wherein the silicon layer includes an N-type first impurity region, a P-type second impurity region disposed opposite the light-receiving surface in a direction perpendicular to the light-receiving surface with respect to the first impurity region and containing boron and oxygen, and an N-type impurity region opposite the first impurity region in the direction perpendicular to the light-receiving surface with respect to the second impurity region, and the photoelectric conversion portion includes at least a part of the first impurity region and at least a part of the second impurity region, and

wherein the second impurity region includes a first portion having an atomic boron concentration Ba that is the highest of the portions opposite the light-receiving surface with respect to the first impurity region and an atomic oxygen concentration Oa, and a second portion located opposite the first impurity region in the direction perpendicular to the light-receiving surface with respect to the first portion and having an atomic boron concentration Bb and an atomic oxygen concentration Ob, the second impurity region satisfying the relationship

Ba×Oa 2 <Bb×Ob 2 .

2. The photoelectric conversion device according the claim 1 , wherein the second impurity region satisfies the relationship Ba<Oa.

3. The photoelectric conversion device according to claim 1 , wherein the second impurity region satisfies the relationship Bb<Ob.

4. The photoelectric conversion device according to claim 1 , wherein the second impurity region satisfies the relationship 1×10 16 ≤Oa≤1×10 18 .

5. The photoelectric conversion device according to claim 1 , wherein the second impurity region satisfies the relationship 1×10 46 ≤Ba×Oa 2 ≤1×10 52 .

6. The photoelectric conversion device according to claim 1 , wherein the second impurity region further includes a third portion located on the same side as the first impurity region in the direction perpendicular to the light-receiving surface with respect to the first portion and having an atomic boron concentration Bc and an atomic oxygen concentration Oc, the second impurity region satisfying the relationship Bc×Oc 2 <Ba×Oa 2 .

7. The photoelectric conversion device according to claim 1 , wherein the second impurity region further includes a third portion located on the same side as the first impurity region in the direction perpendicular to the light-receiving surface with respect to the first portion and having an atomic boron concentration Bc and an atomic oxygen concentration Oc, the second impurity region satisfying the relationship 1×10 46 ≤Bc×Oc 2 ≤1×10 50 .

8. The photoelectric conversion device according to claim 1 , wherein the width of a region, in the direction perpendicular to the light-receiving surface, where a P-type semiconductor region is present on the same side as the first impurity region with respect to the first portion is narrower than the width of a region, in the direction perpendicular to the light-receiving surface, where a P-type semiconductor region is present opposite the first impurity region with respect to the first portion.

9. An imaging system comprising:

the photoelectric conversion device as set forth in claim 1 ; and

at least one unit selected from the group consisting of an optical unit capable of forming an image on the photoelectric conversion device, a control unit capable of controlling the photoelectric conversion device, a processing unit capable of processing signals output from the photoelectric conversion device, a display unit on which an image formed by the photoelectric conversion device is displayed, and a memory unit in which an image formed by the photoelectric conversion device is stored.

10. A photoelectric conversion device comprising:

a photoelectric conversion portion in a silicon layer having a light-receiving surface, the photoelectric conversion portion capable of producing electrons as signal charge carriers from light that has entered through the light-receiving surface,

wherein the silicon layer includes an N-type first impurity region, a P-type second impurity region disposed opposite the light-receiving surface in a direction perpendicular to the light-receiving surface with respect to the first impurity region and containing boron and oxygen, and an N-type impurity region opposite the first impurity region in the direction perpendicular to the light-receiving surface with respect to the second impurity region, and the photoelectric conversion portion includes at least a part of the first impurity region and at least part of the second impurity region, and

wherein the second impurity region includes a first portion having an atomic boron concentration that is the highest of the portions opposite the light-receiving surface with respect to the first impurity region, a second portion opposite the first impurity region in the direction perpendicular to the light-receiving surface with respect to the first portion, and a third portion located on the same side as the first impurity region in the direction perpendicular to the light-receiving surface with respect to the first portion and having an atomic boron concentration Bc and an atomic oxygen concentration Oc, the third portion satisfying the relationship 1×10 46 ≤Bc×Oc 2 ≤1×10 50 .

11. The photoelectric conversion device according to claim 10 , wherein the second portion has an atomic boron concentration Bb and an atomic oxygen concentration Ob, and satisfies the relationship 1×10 50 <Bb×Ob 2 ≤1×10 52 .

12. The photoelectric conversion device according to claim 10 , wherein the silicon layer further includes a P-type third impurity region disposed between the light-receiving surface and the first impurity region and containing boron with an atomic concentration Bd and oxygen with an atomic concentration of Od, the silicon layer satisfying the relationship Bc×Oc 2 <Bd×Od 2 .

13. The photoelectric conversion device according to claim 10 , wherein the silicon layer further includes a P-type third impurity region disposed between the light-receiving surface and the first impurity region and containing boron with an atomic concentration Bd and oxygen with an atomic concentration Od, and the second portion has an atomic boron concentration Bb and an atomic oxygen concentration Ob, and wherein the silicon layer satisfies the relationship Bb×Ob 2 <Bd×Od 2 .

14. The photoelectric conversion device according to claim 10 , wherein the second portion has an atomic boron concentration Bb and an atomic oxygen concentration Ob, and the second impurity region satisfies the relationship Bc×Oc 2 <Bb×Ob 2 .

15. The photoelectric conversion device according to claim 10 , wherein the silicon layer further includes a P-type third impurity region disposed between the light-receiving surface and the first impurity region and containing boron with an atomic concentration Bd and oxygen with an atomic concentration Od, and the third impurity region satisfies the relationship 1×10 50 <Bd×Od 2 ≤1×10 52 .

16. The photoelectric conversion device according to claim 10 , wherein the silicon layer further includes a P-type third impurity region disposed between the light-receiving surface and the first impurity region and containing boron with an atomic concentration Bd and oxygen with an atomic concentration Od, wherein the third impurity region satisfies the relationship Od≥6×10 16 .

17. The photoelectric conversion device according to claim 10 , wherein the width of a region, in the direction perpendicular to the light-receiving surface, where a P-type semiconductor region is present on the same side as the first impurity region with respect to the first portion is narrower than the width of a region, in the direction perpendicular to the light-receiving surface, where a P-type semiconductor region is present opposite the first impurity region with respect to the first portion.

18. An imaging system comprising:

the photoelectric conversion device as set forth in claim 10 ; and

at least one unit selected from the group consisting of an optical unit capable of forming an image on the photoelectric conversion device, a control unit capable of controlling the photoelectric conversion device, a processing unit capable of processing signals output from the photoelectric conversion device, a display unit on which an image formed by the photoelectric conversion device is displayed, and a memory unit in which an image formed by the photoelectric conversion device is stored.