Method of forming a photodiode for an image sensor
AssigneeHynix Semiconductor Inc.
InventorSang Hoon Park
Life of this patent
Estimating the term…
Abstract
The present invention relates to a pinned photodiode used in a CMOS image sensor. The pinned photodiode according to the present invention has an uneven surface for increasing an area of a PN junction of the photodiode. So, the increased PN junction area improves a light sensitivity of the photodiode. That is, the epitaxial layer, in which the photodiode is formed, has a trench or a protrusion. Also, in the pinned photodiode, since the P0 diffusion layer is directly in contact with the P-epi layer, the two P-type layers have the same potential and then it may operate in a low voltage.
Claims5
A method of making a photodiode for use in a CMOS image sensor, the method comprising:
- providing a silicon substrate having a first conductivity type;
- forming a first silicon layer over the substrate, the first silicon layer having the first conductivity type;
- forming at least one feature on the first silicon layer, wherein said forming at least one feature comprises forming a trench or a protrusion;
- wherein the at least one trench having sidewalls and a substantially flat bottom;
- forming a first impurity region of a second conductivity type within the first silicon layer and underneath the feature;
- and
- wherein the first impurity region is at least underneath the substantially flat bottom;
- forming a second impurity region of the first conductivity type beneath the at least one feature and above the top surface of the first impurity region,
- wherein the second impurity region is in contact with both the first silicon layer and the first impurity region.
Dependencies are inferred from the claim text.