Multi-photodiode pixel cell

Abstract

Methods and systems for image sensing are provided. In one example, an apparatus comprises a semiconductor substrate comprising a light incident surface to receive light, a first pinned photodiode, and a second pinned photodiode, the first pinned photodiode and the second pinned photodiode forming a stack structure in the semiconductor substrate along an axis perpendicular to the light incident surface, the stack structure enabling the first pinned photodiode and the second pinned photodiode to, respectively, convert a first component of the light and a second component of the light to first charge and second charge. The apparatus further comprises one or more capacitors formed in the semiconductor substrate and configured to generate a first voltage and a second voltage based on, respectively, the first charge and the second charge.

1 . An apparatus comprising:
 a semiconductor substrate comprising a light incident surface to receive light;   a first pinned photodiode and a second pinned photodiode, the first pinned photodiode being formed adjacent to the second pinned photodiode in the semiconductor substrate;   an optical structure configured to transmit a first component of the light to the first pinned photodiode and a second component of the light to the second pinned photodiode, to enable the first pinned photodiode and the second pinned photodiode to, respectively, convert the first component of the light and the second component of the light to first charge and the second charge; and   first and second capacitors formed in the semiconductor substrate and configured to generate a first voltage and a second voltage based on, respectively, the first charge and the second charge.   
     
     
         2 . The apparatus of  claim 1 , wherein the first component of the light comprises visible light and the second component of the light comprises infrared light. 
     
     
         3 . The apparatus of  claim 1 , wherein the optical structure is further configured to separate a first component of the light from a second component of the light based on at least one of (i) different refractive indices of the first component and the second component of the light, or (ii) different diffraction angles of the first component and the second component of the light. 
     
     
         4 . The apparatus of  claim 1 , wherein the optical structure comprises a diffraction grating structure configured to split the first component of the light from the second component of the light and to direct the first component of the light and the second component of the light to, respectively, the first pinned photodiode and the second pinned photodiode. 
     
     
         5 . The apparatus of  claim 4 , wherein the diffraction grating comprises a blazed transmission grating comprising blazed surfaces configured to diffract the first component of the light towards the first pinned diode and allow the second component of the light to pass through the diffraction grating structure to the second pinned diode. 
     
     
         6 . The apparatus of  claim 1 , wherein the optical structure comprises a light guide configured to split the first and second components of the light and project the first component of the light onto the first pinned photodiode and the second component of the light onto the second pinned photodiode. 
     
     
         7 . The apparatus of  claim 6 , wherein the light guide comprises a wedged surface configured to increase an incident angle of incoming light. 
     
     
         8 . The apparatus of  claim 1 , further comprising a microlens on the light incident surface; and
 wherein the optical structure comprises a mirror configured to transmit the first component of the light to the first pinned photodiode and to reflect the second component of the light towards the microlens to cause the microlens to reflect the second component of the light towards the second pinned photodiode.   
     
     
         9 . The apparatus of  claim 1 , further comprising a barrier layer configured to provide isolation between the first and second pinned photodiodes. 
     
     
         10 . The apparatus of  claim 1 , wherein each of the first pinned photodiode and the second pinned photodiode comprises:
 a P-type semiconductor layer; and   an N-type region completely embedded within the P-type semiconductor layer and isolated from other components of the apparatus.   
     
     
         11 . The apparatus of  claim 1 , wherein each of the first pinned photodiode and the second pinned photodiode comprises:
 an N-type semiconductor layer; and   a P-type region completely embedded within the N-type semiconductor layer and isolated from other components of the apparatus.   
     
     
         12 . An image sensor comprising:
 a semiconductor substrate comprising a light incident surface to receive light;   an array of pixels, each pixel comprising:
 a first pinned photodiode and a second pinned photodiode, the first pinned photodiode being formed adjacent to the second pinned photodiode in the semiconductor substrate; 
 an optical structure configured to transmit a first component of the light to the first pinned photodiode and a second component of the light to the second pinned photodiode, to enable the first pinned photodiode and the second pinned photodiode to, respectively, convert the first component of the light and the second component of the light to first charge and the second charge; and 
 first and second capacitors formed in the semiconductor substrate and configured to generate a first voltage and a second voltage based on, respectively, the first charge and the second charge. 
   
     
     
         13 . The image sensor of  claim 12 , wherein the first component of the light comprises visible light and the second component of the light comprises infrared light. 
     
     
         14 . The image sensor of  claim 12 , wherein the optical structure is further configured to separate a first component of the light from a second component of the light based on at least one of (i) different refractive indices of the first component and the second component of the light, or (ii) different diffraction angles of the first component and the second component of the light. 
     
     
         15 . The image sensor of  claim 12 , wherein the optical structure comprises a diffraction grating structure configured to split the first component of the light from the second component of the light and to direct the first component of the light and the second component of the light to, respectively, the first pinned photodiode and the second pinned photodiode. 
     
     
         16 . The image sensor of  claim 15 , wherein the diffraction grating comprises a blazed transmission grating comprising blazed surfaces configured to diffract the first component of the light towards the first pinned diode and allow the second component of the light to pass through the diffraction grating structure to the second pinned diode. 
     
     
         17 . The image sensor of  claim 12 , wherein the optical structure comprises a light guide configured to split the first and second components of the light and project the first component of the light onto the first pinned photodiode and the second component of the light onto the second pinned photodiode. 
     
     
         18 . The image sensor of  claim 17 , wherein the light guide comprises a wedged surface configured to increase an incident angle of incoming light. 
     
     
         19 . A method comprising:
 receiving light through a light incident surface of a semiconductor substrate;   transmitting by an optical structure a first component of the light to a first pinned photodiode and a second component of the light to a second pinned photodiode, the first pinned photodiode being formed adjacent the second pinned photodiode in a semiconductor substrate along an axis parallel with the light incident surface;   converting, by the first pinned photodiode, the first component of the light to first charge;   converting, by the second pinned photodiode, the second component of the light to second charge;   generating, by a first capacitor formed in the semiconductor substrate, a first voltage based on the first charge; and   generating, by a second capacitor formed in the semiconductor substrate, a second voltage based on the second charge.   
     
     
         20 . The method of  claim 19 , wherein the first component of the light comprises visible light and the second component of the light comprises infrared light.