Image sensor

Abstract

An image sensor is includes a plurality of pixels. Each of the pixels includes a silicon photoconversion region and a material that at least partially surrounds the photoconversion region. The material has a refraction index smaller than the refraction index of silicon, and the interface between the photoconversion region of the pixel and the material is configured so that at least one ray reaching the photoconversion region of the pixel undergoes a total reflection or a plurality of successive total reflections at the interface.

1 . A device, comprising:
 a substrate;   a pixel on the substrate, the pixel having:
 a silicon photoconversion region extending upwardly from a rear surface to a front surface opposite to the rear surface and extends laterally between four lateral surfaces, the rear surface configured to receive at least one ray; 
 a material at least partially surrounding the photoconversion region, the material having a refraction index smaller than a refraction index of silicon; and 
 an antireflection layer in contact with only a portion of the rear surface of the photoconversion region, the antireflection layer being arranged to be crossed by the at least one ray. 
   
     
     
         2 . The device of  claim 1 , comprising a lens arranged on the rear surface of the photoconversion region, the lens overlapping the antireflection layer. 
     
     
         3 . The device of  claim 1 , comprising a trench in the silicon photoconversion region. 
     
     
         4 . The device of  claim 3  wherein the trench has a first angled portion separated from a second angled portion by a central region. 
     
     
         5 . The device of  claim 4  wherein the first angled portion is closer to the antireflection layer than the second angled portion. 
     
     
         6 . A device, comprising:
 a substrate;   a pixel on the substrate, the pixel having:
 a silicon photoconversion region; and 
 a trench in the silicon photoconversion region, the trench having a first angled portion separated from a second angled portion by a central region; and 
 an antireflection layer in the substrate, the first angled portion being closer to the antireflection layer than the second angled portion. 
   
     
     
         7 . The device of  claim 6 , comprising a lens on the substrate, the lens overlapping the antireflection layer and at least a portion of the first angled portion. 
     
     
         8 . The device of  claim 7  wherein the silicon photoconversion region extends upwardly from a rear surface to a front surface opposite to the rear surface and extends laterally between four lateral surfaces, the rear surface configured to receive at least one ray. 
     
     
         9 . The device of  claim 8  comprising a material at least partially surrounding the photoconversion region, the material having a refraction index smaller than a refraction index of silicon. 
     
     
         10 . The device of  claim 9  wherein the antireflection layer is in contact with only a portion of the rear surface of the photoconversion region, the antireflection layer being arranged to be crossed by the at least one ray. 
     
     
         11 . The device of  claim 10 , comprising a lens arranged on the rear surface of the photoconversion region, the lens overlapping the antireflection layer. 
     
     
         12 . A method, comprising:
 manufacturing an image sensor by forming first trenches extending into a silicon substrate from a first surface of the silicon substrate, the first trenches having opposite oblique walls meeting at a bottom of the first trenches;   forming second trenches laterally delimiting photoconversion regions of the sensor pixels, each of the second trenches extending into the silicon substrate from the bottom of a respective first trench;   filling the first and second trenches with at least one material having a refraction index smaller than a refraction index of silicon; and   forming third trenches extending into the silicon substrate from a second surface of the silicon substrate opposite to the first surface.   
     
     
         13 . The method of  claim 12  wherein the third trenches having opposite oblique walls meeting at a bottom of the third trenches. 
     
     
         14 . The method of  claim 13  wherein each third trench is arranged opposite a corresponding first trench and the bottom of each third trench being arranged in the at least one material filling a corresponding second trench. 
     
     
         15 . The method of  claim 14 , comprising filling the third trenches with the at least one material. 
     
     
         16 . The method of  claim 15 , further comprising:
 forming antireflection layer portions on rear surfaces of each of the photoconversion regions.