Image sensor and method for fabricating the same

Abstract

An image sensor includes a semiconductor substrate, a plurality of photoelectric transducer devices and a dielectric isolating structure. The semiconductor substrate has a backside surface and a front side surface opposite to the backside surface. The photoelectric transducer devices are disposed on the front side surface. The dielectric isolating structure extends downwards into the semiconductor substrate from the front side surface and penetrates through the backside surface, so as to from a grid structure and isolate the photoelectric transducer devices from each other.

1 . An image sensor, comprising:
 a semiconductor substrate having a backside surface and a front side surface opposite to the backside surface;   a plurality of photoelectric transducer devices disposed on the front side surface;   a dielectric isolating structure extending downwards into the semiconductor substrate from the front side surface and penetrating through the backside surface, so as to from a grid structure and isolate the photoelectric transducer devices from each other; and   a color filter (CF) formed on the grid structure and directly in contact with the semiconductor substrate.   
     
     
         2 . The image sensor according to  claim 1 , wherein the grid structure and the semiconductor substrate defines a plurality of recesses and each of the recesses is corresponding to a sub-pixel region. 
     
     
         3 . The image sensor according to  claim 2 , further comprising
 a plurality of micro lenses disposed on the CF at least partially extending into the recesses.   
     
     
         4 . The image sensor according to  claim 1 , further comprising an embedded light shielding layer embedded in the dielectric isolating structure. 
     
     
         5 . The image sensor according to  claim 4 , wherein the dielectric isolating structure further comprises a first dielectric layer and a second dielectric layer; and the embedded light shielding layer is disposed between the first dielectric layer and the second dielectric layer. 
     
     
         6 . The image sensor according to  claim 4 , wherein the dielectric isolating structure comprises silicon oxide, and the embedded light shielding layer comprises a material selected from a group consisting of silicon nitride (SiN), silicon oxynitride (SiON), poly-silicon and arbitrary combinations thereof. 
     
     
         7 . The image sensor according to  claim 1 , further comprising a light shielding liner blanket over a plurality of sidewalls of the dielectric isolating structure. 
     
     
         8 . The image sensor according to  claim 7 , wherein the dielectric isolating structure comprises silicon oxide and the light shielding liner comprises SiN. 
     
     
         9 . The image sensor according to  claim 1 , further comprising a plurality of spacers disposed on a plurality of sidewalls of the grid structure. 
     
     
         10 . The image sensor according to  claim 9 , wherein the spacers comprises a light shielding material selected from a group consisting of metal, metal oxide, metal nitride, alloys and arbitrary combinations thereof. 
     
     
         11 . The image sensor according to  claim 9 , wherein the spacers comprises a metal material selected from a group consisting of copper (Cu), silver (Ag), aluminum (Al), titanium (Ti), tungsten (W), tantalum (Ta) and arbitrary combinations thereof. 
     
     
         12 . The image sensor according to  claim 1 , wherein each of the photoelectric transducer devices comprises:
 a photo diode (PD) disposed in the semiconductor substrate;   a floating drain region disposed in the semiconductor substrate and separated from the PD; and   a gate structure disposed on the front side surface of the semiconductor substrate and adjacent to the PD and the floating drain region.   
     
     
         13 . The image sensor according to  claim 1 , further comprising a metal interconnection structure disposed on the front side surface and electrically connected to the photoelectric transducer devices. 
     
     
         14 . A method for fabricating an image sensor, comprising:
 providing a semiconductor substrate having a plurality of photoelectric transducer devices and a dielectric isolating structure, wherein the semiconductor substrate has a backside surface and a front side surface opposite to the backside surface; the photoelectric transducer devices are disposed on the front side surface; and the dielectric isolating structure extends downwards into the semiconductor substrate from the front side surface and penetrates through the backside surface, so as to isolate the photoelectric transducer devices from each other; and   removing a portion of the semiconductor substrate from the backside surface to expose a portion of the dielectric isolating structure, so as to form a grid structure protruding from the backside surface.   
     
     
         15 . The method according to  claim 14 , wherein the process for removing the portion of the semiconductor substrate comprises a wet etching process. 
     
     
         16 . The method according to  claim 14 , wherein the process for forming the dielectric isolating structure comprises:
 forming a plurality of extending downwards into the semiconductor substrate from the front side surface of the semiconductor substrate;   forming a first dielectric layer to blanket over a plurality of sidewalls of the trenches;   forming an embedded light shielding layer on the first dielectric layer; and   forming a second dielectric layer on the embedded light shielding layer to make the embedded light shielding layer disposed between the first dielectric layer and the second dielectric layer.   
     
     
         17 . The method according to  claim 14 , wherein the process for forming the dielectric isolating structure comprises:
 forming a plurality of trenches extending downwards into the semiconductor substrate from the front side surface of the semiconductor substrate;   forming a light shielding liner to blanket over a plurality of sidewalls of the trenches; and   filling the trenches with a dielectric material.   
     
     
         18 . The method according to  claim 14 , further comprising:
 forming a capping layer to blanket over the grid structure and the backside surface of the semiconductor substrate; and   removing a portion of the capping layer to form a plurality of spacers on a plurality of sidewalls of the dielectric isolating structure.   
     
     
         19 . The method according to  claim 14 , further comprising:
 forming a CF on the grid structure and the backside surface of the semiconductor substrate; and   forming a plurality of micro lenses on the CF.   
     
     
         20 . The method according to  claim 14 , wherein the process for forming the photoelectric transducer devices comprises:
 forming a photo diode PD and a floating drain region separated from the PD in the semiconductor substrate; and   forming a gate structure on the front side surface of the semiconductor substrate and adjacent to the PD and the floating drain region.