Image sensor having a highly doped and shallow pinning layer
View Patent ↗An image sensor includes a first conductivity type substrate with a trench formed in a predetermined portion thereof, a second conductivity type impurity region formed in the first conductivity type substrate below the trench and being a part of a photodiode, a second conductivity type first epitaxial layer filling the trench and being a part of the photodiode, and a first conductivity type second epitaxial layer formed over the second conductivity type first epitaxial layer.
1. An image sensor, comprising:
a first conductivity type substrate with a trench formed in a predetermined portion thereof;
a second conductivity type impurity region formed in the first conductivity type substrate below the trench and being a part of a photodiode;
a second conductivity type first epitaxial layer filling the trench and being a part of the photodiode; and
a first conductivity type second epitaxial layer formed over the second conductivity type first epitaxial layer.
2. The image sensor of claim 1 , further comprising a gate structure formed over the first conductivity type substrate next to the photodiode.
3. The image sensor of claim 1 , wherein the first conductivity type second epitaxial layer is a pinning layer.
4. The image sensor of claim 1 , wherein the second conductivity type first epitaxial layer includes one of silicon (Si) and silicon germanium (SiGe).
5. The image sensor of claim 1 , wherein the first conductivity type second epitaxial layer includes one of silicon (Si) and silicon germanium (SiGe).
6. The image sensor of claim 1 , wherein the second conductivity type first epitaxial layer overlaps with a bottom portion of the gate structure.
7. The image sensor of claim 1 , wherein the first conductivity type second epitaxial layer contacts the first conductivity type substrate.
8. The image sensor of claim 1 , wherein the trench has a depth ranging from approximately 1,800 .ANG. to approximately 2,200 .ANG.
9. The image sensor of claim 1 , wherein the second conductivity type first epitaxial layer is doped with second conductivity type impurities in-situ while growing.
10. The image sensor of claim 1 , wherein the first conductivity type second epitaxial layer is doped with first conductivity type impurities in-situ while growing.
11. The image sensor of claim 1 , wherein the first conductivity type second epitaxial layer has a thickness ranging from approximately 20 .ANG. to approximately 1,000 .ANG.
12. The image sensor of claim 1 , wherein the first conductivity type substrate includes Si.