Miniature image sensor

1. An image sensor comprising at least one photodiode and at least one transistor formed in and on a silicon substrate, the assembly of the photodiode and of the transistor being surrounded with a heavily-doped, ion implanted insulating wall, the insulating wall formed by dopant ion implantation into the substrate, wherein the silicon substrate has a crystal orientation (110), wherein the insulating wall has a depth of 2 to 3 micrometers and a width between 0.2 and 0.5 micrometer.

2. The image sensor of claim 1 , wherein the insulating wall is formed by a dopant implantation along a direction perpendicular to the silicon substrate surface.

3. The image sensor of claim 2 , wherein the implantation is performed with an implantation power smaller than 300 keV.

4. The image sensor of claim 1 , wherein the substrate of orientation (110) and the insulating wall are N-type doped and wherein the transistor is a PMOS transistor.

5. The image sensor of claim 4 , wherein the insulating wall is doped with phosphorus, arsenic, or antimony.

6. The image sensor of claim 4 , wherein the insulating wall is doped with phosphorus.

7. The image sensor of claim 1 , further comprising a substrate of crystal orientation (100) which extends above the substrate of crystal orientation (110) and wherein transistors with a high switching speed are formed.

8. The image sensor of claim 7 , wherein the photodiode is illuminated from the rear surface of the substrate of crystal orientation (110).

9. An image sensor comprising:

a substrate;

a photodiode and a transistor formed in the substrate; and

an ion implanted insulating wall formed by dopant ion implantation into the substrate and surrounding the photodiode and the transistor, the substrate being silicon having a crystal orientation (110), wherein the insulating wall has a depth of 2 to 3 micrometers and a width between 0.2 and 0.5 micrometer.

10. An image sensor as defined in claim 9 , wherein the insulating wall is formed by dopant implantation along a direction perpendicular to a surface of the substrate.

11. An image sensor as defined in claim 9 , wherein the substrate and the insulating wall are N-type doped and wherein the transistor is a PMOS transistor.

12. A method for fabrication of an image sensor, comprising:

providing a silicon substrate having a crystal orientation (110);

forming a photodiode and a transistor in the silicon substrate; and

implanting a heavily-doped insulating wall in the silicon substrate and surrounding the photodiode and the transistor, wherein the insulating wall has a depth of 2 to 3 micrometers and a width between 0.2 and 0.5 micrometer.

13. A method as defined in claim 12 , wherein implanting the insulating wall is performed by dopant implantation along a direction perpendicular to a surface of the silicon substrate.