Rear-face illuminated solid state image sensors

1. A microelectronic unit comprising:

a semiconductor element having a front surface and a rear surface remote from the front surface;

a packaging layer attached to the front surface of the semiconductor element;

a layer including adhesive material attaching the semiconductor element to the packaging layer,

wherein the semiconductor element includes a light detector disposed adjacent to the front surface and aligned with a portion of the rear surface to receive light through the rear surface, wherein the light detector includes a plurality of light detector elements arranged in an array, wherein a conductive contact of the semiconductor element has a first surface and a second surface remote from the first surface, wherein the conductive contact is disposed within the adhesive material and has an opening extending from the first surface through the conductive contact towards the second surface, the conductive contact being a single layer bond pad having a single thickness; and

a conductive interconnect extending through the packaging layer and the opening of the conductive contact from the first surface towards the second surface so as to contact a wall surface of the conductive contact, at least a portion of the conductive interconnect being exposed at a surface of the microelectronic unit.

2. The microelectronic unit of claim 1 , wherein a thickness of the conductive contact is between 3 and 30 microns.

3. The microelectronic unit of claim 1 , wherein the opening has a depth of less than one micron of the bond pad.

4. The microelectronic unit of claim 1 , wherein the opening has a depth that is less than or equal to ten percent of the thickness of the bond pad.

5. The microelectronic unit of claim 1 , wherein the opening has a depth that extends fifty percent or more of the thickness of the bond pad.

6. The microelectronic unit of claim 1 further comprising:

a packaging assembly attached at the rear surface of the semiconductor element and defining a cavity aligned with the light detector in a direction normal to the rear surface.

7. The microelectronic unit of claim 1 , wherein the packaging layer has a thickness of about thirty to one thousand microns.

8. The microelectronic unit of claim 1 , wherein the light detector includes a plurality of light elements defining one or more pixels, wherein each pixel has a lateral dimension extending in a lateral direction parallel to the front surface substantially equal to the thickness of the semiconductor element.

9. The microelectronic unit of claim 6 further comprising: a first dielectric layer disposed on the rear surface of the semiconductor element and to which the packaging assembly is attached through a second dielectric layer.

10. The microelectronic unit of claim 9 , wherein the first dielectric layer has a thickness of about one to five microns.

11. A microelectronic unit comprising:

a semiconductor element having a front surface and a rear surface remote from the front surface;

a packaging layer attached to the front surface of the semiconductor element; and

an adhesive layer bonding the packaging assembly to the semiconductor element,

wherein the semiconductor element includes a light detector disposed adjacent to the front surface and aligned with a portion of the rear surface to receive light through the rear surface portion, wherein the light detector includes a plurality of light detector elements arranged in an array,

wherein a conductive contact overlies the front surface of the semiconductor element and has a first surface and a second surface remote from the first surface, wherein the conductive contact has an opening extending from the first surface through the conductive contact towards the second surface, the conductive contact including a plurality of conductive layers adjacent the adhesive layer, the conductive layers electrically connected to each other by conductive structures disposed between the conductive layers; and

a conductive interconnect extending through the packaging layer, the adhesive layer, at least one conductive structure, and the opening of the conductive contact from the first surface towards the second surface so as to contact two or more conductive layers of the plurality of layers of the conductive contact, at least a portion of the conductive interconnect being exposed at a surface of the microelectronic unit.

12. The microelectronic unit of claim 11 further comprising:

a packaging assembly attached at the rear surface of the semiconductor element and defining a cavity aligned with the light detector in a direction normal to the rear surface.

13. The microelectronic unit of claim 11 , wherein the conductive structures are vertical conductive structures.

14. The microelectronic unit of claim 11 , wherein the conductive structures are vias.

15. The microelectronic unit of claim 11 , wherein the conductive layers are metal layers and vias are disposed between each of the metal layers.

16. The microelectronic unit of claim 12 , wherein the opening extends no further than the metal layer closest to the semiconductor element, the sensor being electrically isolated from the interconnection element.

17. The microelectronic unit of claim 12 , wherein the plurality of metal layers include first, second, third, and fourth metal layers, one or more of the first, second, third and fourth metal layers including aluminum and the second metal layer includes at least one of nickel, copper, silver or gold.

18. The microelectronic unit of claim 17 , wherein the at least one of the second, third and fourth metal layers is formed by electrode-less plating.