Method and apparatus for collecting photons in a solid state imaging sensor

Abstract

A photon collector has a reflecting metal layer to increase photon collection efficiency in a solid state imaging sensor. The reflecting metal layer reflects incident light internally to a photosensor. A plurality of photon collectors is formed in a wafer substrate over an array of photosensors. The photon collector is formed in an opening in an insulating layer provided over each photosensor.

1 . An imaging device, comprising: 
 a substrate;    a plurality of photosensors arranged within said substrate to receive light;    an insulating layer formed over said plurality of photosensors;    an opening provided in said insulating layer over each photosensor through which said light is received; and    a light reflecting layer formed on an internal sidewall of each opening.    
   
   
       2 . An imaging device according to  claim 1 , wherein said opening at least partially has a shape selected from the group consisting of substantially cylindrical, substantially conical, and curved conical.  
   
   
       3 . An imaging device according to  claim 1 , wherein the diameter of an upper portion of each opening is greater than the diameter at the base of each opening.  
   
   
       4 . An imaging device according to  claim 1 , wherein each light reflecting layer comprises a metal layer.  
   
   
       5 . An imaging device according to  claim 4 , wherein each light reflecting layer comprises an aluminum layer.  
   
   
       6 . An imaging device according to  claim 4 , wherein each light reflecting layer comprises a silver layer.  
   
   
       7 . An imaging device according to  claim 6 , said imaging device further comprising a barrier layer formed on each said sidewall beneath said silver layer to prevent migration of silver ions into said insulating layer.  
   
   
       8 . An imaging device according to  claim 1 , further comprising an etch stop layer formed over each photosensor below said insulating layer.  
   
   
       9 . An imaging device according to  claim 1 , further comprising an optically transparent material disposed in each opening.  
   
   
       10 . An imaging device according to  claim 9 , wherein the optically transparent material fills each opening.  
   
   
       11 . An imaging device according to  claim 10 , further comprising a color filter disposed over said filled openings.  
   
   
       12 . An imaging device according to  claim 11 , further comprising a lens structure over said filter.  
   
   
       13 . An imaging device according to  claim 1 , wherein said imaging device is a CCD imaging device.  
   
   
       14 . An imaging device according to  claim 1 , wherein said imaging device is a CMOS imaging device.  
   
   
       15 . An imaging device according to  claim 1 , wherein said photosensors are selected from the group consisting of photodiodes, photogates, and photoconductors.  
   
   
       16 . A CMOS imaging device, comprising: 
 an insulating layer;    a CMOS array of photodiodes arranged within said insulating layer;    a plurality of openings in said insulating layer formed over a respective photodiode, each opening having sidewalls and a light-reflecting metal layer formed on said sidewalls, the metal layer reflecting light received within its opening to its respective photodiode, each opening being filled with an optically transparent material;    a color filter layer disposed over said array of photodiodes; and    a lens layer disposed over said color filter layer.    
   
   
       17 . An image pixel array in an imaging device, comprising: 
 a plurality of photon collectors formed over a plurality of photosensors for receiving light energy, each photon collector having an interior space capable of receiving light and reflecting the light to at least one of said photosensors, said interior space being defined by reflecting inner surfaces of each photon collector; and    a color filter formed over each said photon collector.    
   
   
       18 . An image pixel array according to  claim 17 , wherein each photon collector receives and reflects light to a single corresponding photosensor.  
   
   
       19 . An image pixel array according to  claim 17 , wherein each reflecting inner surface comprises a layer of silver.  
   
   
       20 . An image pixel array according to  claim 17 , wherein each reflecting inner surface comprises an aluminum layer.  
   
   
       21 . An image pixel array according to  claim 17 , wherein each photon collector reflects substantially all incident light internally.  
   
   
       22 . An image pixel array according to  claim 17 , wherein each photon collector has a shape selected from the group consisting of substantially cylindrical, substantially conical, curved conical, and combinations thereof.  
   
   
       23 . An image pixel array according to  claim 17 , wherein a diameter of an upper portion of each photon collector is greater than a diameter at the base of each respective photon collector.  
   
   
       24 . A method of fabricating an imaging device, said method comprising: 
 forming a plurality of photosensors on a wafer;    forming a structure with sidewalls in an insulating layer on said wafer provided over said photosensors; and    depositing a reflecting material on said sidewalls of each structure.    
   
   
       25 . A method according to  claim 24 , wherein said reflecting material is a metal.  
   
   
       26 . A method according to  claim 25 , wherein said reflecting material is aluminum.  
   
   
       27 . A method according to  claim 25 , wherein said reflecting material is silver.  
   
   
       28 . A method according to  claim 27 , the method further including forming a barrier layer between said silver and said insulating layer.  
   
   
       29 . A method according to  claim 24 , wherein the diameter of an upper portion of each structure is greater than the diameter at the base of each said structure.  
   
   
       30 . A method according to  claim 24 , wherein said sidewalls of each structure are selected from the group consisting of substantially perpendicular, substantially diagonal, curved surfaces, and combinations thereof.  
   
   
       31 . A method according to  claim 24 , further comprising depositing said reflecting layer through a collimated structure.  
   
   
       32 . A method according to  claim 31 , wherein said wafer is held at an angle to the collimation angle of said structure.  
   
   
       33 . A method according to  claim 32 , wherein the angle is selected such that reflecting material is not deposited over said photosensors.  
   
   
       34 . A method according to  claim 24 , further comprising providing an optically transparent material contained within the sidewalls of each said structure.  
   
   
       35 . A method according to  claim 34 , wherein the optically transparent material is selected from the group consisting of spun-on glass and photoresist.  
   
   
       36 . A method of fabricating an imaging device, said method comprising: 
 forming a photodiode beneath an insulating layer;    providing an etch stop layer over said photodiode;    etching an opening in the semiconductor substrate above the photodiode to said etch stop layer;    depositing a light-reflecting metal on sidewalls of said opening with a collimated source of said light-reflecting metal; and    filling said opening with a optically transparent material.    
   
   
       37 . A method of obtaining an image using an imaging device, said method comprising: 
 targeting an object with an imaging device having a lens structure;    passing light reflected from said object as focused light through said lens structure and into a plurality of photon collectors formed in an insulating layer;    reflecting at least some of the focused light off of reflecting layers provided on sidewalls of said photon collectors; and    sensing said focused light passed into said plurality of photon collectors with an array of photodiodes arranged to respectively correspond with said photon collectors.    
   
   
       38 . An imager system, comprising: 
 (i) a processor; and    (ii) an imaging device coupled to said processor, said imaging device comprising: 
 an insulating layer;  
 a plurality of photodiodes beneath said insulating layer;  
 a plurality of photon collectors, each photon collector being formed in said insulating layer over a respective photodiode, each photon collector arranged to receive light and reflect the light within an interior space of the photon collector to said photodiode; and  
 a reflecting layer deposited on said inner surfaces of each photon collector.  
   
   
   
       39 . An imager system according to  claim 38 , further comprising a lens structure disposed over said photon collectors.  
   
   
       40 . An imager system according to  claim 39 , further comprising an etch stop layer provided over said photodiodes.  
   
   
       41 . An imager system according to  claim 38 , further comprising an optically transparent material in said interior spaces of said photon collectors.