Image sensor and fabrication method thereof
An image sensor has a substrate, a dielectric layer positioned on the substrate, a pixel array including a plurality of pixels defined on the substrate, a shield electrode positioned between any two adjacent pixel electrodes of the pixels, a photo conductive layer positioned on the shield electrode and the pixel electrodes, and a transparent conductive layer covering the photo conductive layer.
1. A method of fabricating an image sensor, the method comprising:
providing a substrate comprising a plurality of pixel circuits thereon, each of the pixel circuits corresponding to a pixel defined on the substrate;
forming a conductive layer on the substrate;
performing a first photolithography-etching process (PEP) to remove portions of the conductive layer to form a plurality of pixel electrodes and to form a shield electrode between any two adjacent pixel electrodes, each of the pixel electrodes being positioned in one pixel and electrically connected to the corresponding pixel circuit;
forming an insulating layer covering the pixel electrodes and the shield electrode;
performing a second PEP to remove portions of the insulating layer to expose central portions of the pixel electrodes, while edge portions of the pixel electrodes and the shield electrode are still covered by the insulating layer;
forming a photo conductive layer on the pixel electrodes and the shield electrode; and
forming a transparent conductive layer covering the photo conductive layer.
2. The method of claim 1 , wherein the insulating layer has a thickness about 200 angstroms.
3. The method of claim 1 , wherein the insulating layer comprises silicon oxide.
4. The method of claim 1 , wherein the shield electrode and the pixel electrodes comprise titanium nitride.
5. The method of claim 1 , wherein the shield electrode has the same distances to the two adjacent pixel electrodes.
6. The method of claim 1 , wherein the photo conductive layer comprises:
an n-type layer positioned on the pixel electrodes and the shield electrode;
an intrinsic layer (i-layer) positioned on the n-type layer; and
a p-type layer positioned on the i-layer.
7. The method of claim 6 , wherein the p-type layer and the n-type layer comprise α-SiC:H material.
8. The method of claim 6 , wherein the i-layer comprise α-Si:H materials.
9. The method of claim 6 , wherein the i-layer at least has a thickness about 5000 angstroms.
10. The method of claim 9 , wherein the i-layer has a thickness about 5000˜10000 angstroms.