Photoelectric conversion device, image pickup system and method of manufacturing photoelectric conversion device

1. A photoelectric conversion device, comprising:

a first semiconductor substrate which includes a photoelectric conversion unit for generating a signal charge in accordance with an incident light; and

a second semiconductor substrate which includes a signal processing unit for processing an electrical signal on basis of the signal charge, the signal processing unit being situated in an orthogonal projection area from the photoelectric conversion unit to the second semiconductor substrate, and a multilayer film including a plurality of insulator layers being provided between the first semiconductor substrate and the second semiconductor substrate,

wherein a thickness of the second semiconductor substrate is smaller than 500 micrometers, and the thickness of the second semiconductor substrate is greater than a distance between the second semiconductor substrate and a light-receiving surface of the first semiconductor substrate.

2. The photoelectric conversion device according to claim 1 , wherein the thickness of the second semiconductor substrate is equal to or greater than 10 times the thickness of the first semiconductor substrate and is equal to or smaller than 100 times the thickness of the first semiconductor substrate.

3. The photoelectric conversion device according to claim 1 , wherein the thickness of the second semiconductor substrate is equal to or greater than 20 micrometers and is equal to or smaller than 400 micrometers.

4. The photoelectric conversion device according to claim 1 , wherein the first semiconductor substrate and the second semiconductor substrate are silicon substrates, the thickness of the first semiconductor substrate is equal to or smaller than 10 micrometers, and the thickness of the second semiconductor substrate is equal to or greater than 50 micrometers.

5. The photoelectric conversion device according to claim 1 , further comprising a light control film which covers the light-receiving surface of the first semiconductor substrate, and the thickness of the second semiconductor substrate is greater than the distance between the second semiconductor substrate and the light input surface of the light control film.

6. The photoelectric conversion device according to claim 1 , further comprising a heat-conductive member which has thermal conductivity higher than thermal conductivity of the insulator layer, wherein the heat-conductive member being provided on the side opposite to the first semiconductor substrate via the second semiconductor substrate and being provided in contact with the orthogonal projection area from the photoelectric conversion unit in the second semiconductor substrate.

7. The photoelectric conversion device according to claim 6 , wherein the heat-conductive member includes a heat-conductive portion which has thermal conductivity which is higher than thermal conductivity of the second semiconductor substrate.

8. The photoelectric conversion device according to claim 6 , wherein a surface area of the orthogonal projection area from the photoelectric conversion unit in a surface of the heat-conductive member on the side opposite to the second semiconductor substrate is larger than a surface area of a surface of the second semiconductor substrate on the side of the heat-conductive member.

9. The photoelectric conversion device according to claim 1 , wherein a surface area of a surface of the second semiconductor substrate on the side opposite to the first semiconductor substrate is larger than a surface area of a surface of the second semiconductor substrate on the side of the first semiconductor substrate.

10. An image pickup system, comprising: the photoelectric conversion device according to claim 1 ; and a cooling unit which carries out forced cooling of the second semiconductor substrate by air cooling or water cooling.