Image sensor structure with recessed separator layer

1. An image sensor structure comprising a plurality of pixels formed on a substrate, each pixel comprising:

an image sensor interconnect structure, an etching stop layer, a separator layer and an electrode layer formed on the substrate in sequence, wherein the separator layer has a first thickness, a side wall of the separator layer is recessed from a side wall of the electrode layer by a first distance; and

a first doped amorphous silicon layer formed on the electrode layer, wherein a first portion of the separator layer and a first portion of the first doped amorphous silicon layer of the pixel are disconnected from a second portion of the separator layer and a second portion of the first doped amorphous silicon layer of an adjacent pixel, and the a third portion of first and second portions of the first doped amorphous silicon layer is also formed directly on the etching stop layer between the first and second portions of the separator layer of two adjacent pixels without electrically connecting to the electrode layer.

2. The image sensor structure as claimed in claim 1 , wherein an etch selectivity of the separator layer to the etching stop layer is between about 1:1 and about 1000:1.

3. The image sensor structure as claimed in claim 1 , wherein the etching a stop layer is nitride while the separator layer is an oxide, or the etching stop layer is an oxide while the separator layer a is nitride.

4. The image sensor structure as claimed in claim 1 , wherein the electrode layer comprises TiN, aluminum, an alloy of aluminum, copper, an alloy of copper or copper-based conductive materials.

5. The image sensor structure as claimed in claim 1 , wherein a ratio of the first distance to the first thickness is between 1:1and 50:1.

6. The image sensor structure as claimed in claim 1 , further comprising:

an undoped amorphous silicon layer formed on the first doped amorphous silicon layer; and

a second doped amorphous silicon layer formed on the undoped amorphous silicon layer to form a photodiode layer comprising the first doped amorphous silicon layer, the undoped amorphous silicon layer and the second doped amorphous silicon layer.

7. The image sensor structure as claimed in claim 6 , wherein the first doped silicon amorphous layer is n-type while the second doped silicon amorphous layer is p-type, or the first undoped silicon amorphous layer is p-type while the second doped amorphous silicon layer is n-type.

8. The image sensor structure as claimed in claim 6 , further comprising:

a transparent conductive layer formed on the photodiode layer.

9. The image sensor structure as claimed in claim 8 , wherein the transparent conductive layer comprises indium-tin-oxide, tin dioxide, titanium nitride or a thin salicide.