Method of forming a pixel sensor cell for collecting electrons and holes
View Patent ↗The present invention is a pixel sensor cell and method of making the same. The pixel sensor cell approximately doubles the available signal for a given quanta of light. The device of the present invention utilizes the holes produced by impinging photons in a pixel sensor cell circuit. A pixel sensor cell having reduced complexity includes an n-type collection well region formed beneath a surface of a substrate for collecting electrons generated by electromagnetic radiation impinging on the pixel sensor cell and a p-type collection well region formed beneath the surface of the substrate for collecting holes generated by the impinging photons. A circuit structure having a first input is coupled to the n-type collection well region and a second input is coupled to the p-type collection well region, wherein an output signal of the pixel sensor cell is the magnitude of the difference of a signal of the first input and a signal of the second input.
1. A method of forming a pixel sensor cell comprising:
providing a substrate;
forming an n-type collection well region in said substrate for collecting electrons generated by electromagnetic radiation impinging on said pixel sensor cell;
forming an n-type diffusion region in direct physical contact with said n-type collection well region;
forming a p-type collection well region in said substrate for collecting holes generated by said impinging electromagnetic radiation;
forming a p-type diffusion region in direct physical contact with said p-type collection well region; and
forming a circuit structure having a first input coupled to said n-type collection well region and a second input coupled to said p-type collection well region, wherein an output signal of said pixel sensor cell being the magnitude of the difference of a signal of said first input and a signal of said second input.
2. The method of claim 1 , wherein said steps of forming said n-type and p-type collection well regions comprise:
forming a mask structure on said substrate having an opening;
ion implanting an n-type dopant in said substrate exposed by said opening to form said n-type collection well region; and
ion implanting a p-type dopant in said substrate exposed by said opening to form said p-type collection well region.
3. The method of claim 2 , wherein said step of ion implanting said n-type dopant comprises ion implanting phosphorous ions at a substantially vertical angle in relation to the surface of said substrate at a dose from about 2×10 12 atoms per cm 2 to about 2×10 13 atoms per cm 2 and an ion implant energy from about 100 keV to about 1000 keV.
4. The method of claim 2 , wherein said step of ion implanting said p-type dopant comprises ion implanting boron ions at a substantially vertical angle in relation to the surface of said substrate at a dose from about 2×10 12 atoms per cm 2 to about 2×10 13 atoms per cm 2 and an ion implant energy from about 50 keV to about 150 keV.
5. The method of claim 1 , wherein said steps of forming said n-type and p-type diffusion regions comprise:
forming a mask structure having an opening on said substrate;
ion implanting an n-type dopant in said substrate exposed by said opening to form said n-type diffusion region; and
ion implanting a p-type dopant in said substrate exposed by said opening to form said p-type diffusion region.
6. The method of claim 5 , wherein said step of ion implanting said n-type dopant comprises ion implanting phosphorous ions at a substantially vertical angle in relation to the surface of said substrate at a dose from about 2×10 12 atoms per cm 2 to about 2×10 13 atoms per cm 2 and an ion implant energy from about 100 keV to about 1000 keV.
7. The method of claim 5 , wherein said step of ion implanting said p-type dopant comprises ion implanting boron ions at a substantially vertical angle in relation to the surface of said substrate at a dose from about 2×10 12 atoms per cm 2 to about 2×10 13 atoms per cm 2 and an ion implant energy from about 50 keV to about 150 keV.
8. The method of claim 1 further comprising:
forming a first interconnect for coupling said n-type diffusion region to said first input of said circuit structure; and
forming a second interconnect for coupling said p-type diffusion region to said second input of said circuit structure.
9. The method of claim 1 , wherein said step of forming said circuit structure comprises forming a differential amplifier circuit having a negative input terminal coupled to said first input of said circuit structure and a positive input terminal coupled to said second input of said circuit structure.
10. The method of claim 1 further comprising forming a pinning layer in an upper surface of said substrate.
11. The method of claim 1 , wherein said substrate comprises a buried dielectric layer, said n-type and p-type collection well regions formed in a portion of said substrate over said buried dielectric layer.
12. The method of claim 1 further comprising a step of forming a pinning layer substantially surrounding said n-type and p-type collection well regions.
13. The method of claim 1 , wherein one of said n-type and p-type collection well regions is formed substantially suffounding the other n-type or p-type collection well regions.