Image sensor and method of forming the same

Abstract

This disclosure relates to various embodiments of an image sensor. The image sensor includes a substrate comprising a first material. A semiconductor layer is located on the substrate and comprises a second material different from the first material. A doped capping layer is located on the top surface of the semiconductor layer and comprises a first doping type. A doped peripheral region is located in the substrate and on the opposite side of the semiconductor layer. The doped peripheral region comprises the first doping type.

Claims

1. An image sensor, comprising: A substrate comprising a first material; a semiconductor layer situated on the substrate and comprising a second material different from the first material; A doped capping layer, located on the top surface of the semiconductor layer and including a first doping type; and a doped peripheral region, located in the substrate and on the opposite side of the semiconductor layer, wherein the doped peripheral region includes the first doping type, wherein the substrate includes opposite sidewalls defining a recess, wherein the semiconductor layer is disposed in the recess and the top surface of the semiconductor layer is lower than the top surface of the substrate, wherein the doped capping layer extends along the top surface of the semiconductor layer between the opposite sidewalls of the substrate, and wherein the doped peripheral region extends laterally continuously from the outer sidewall of the doped capping layer in a direction away from the semiconductor layer.

2. The image sensor as claimed in claim 1, wherein the doped peripheral region continuously and laterally surrounds the outer periphery of the semiconductor layer and is laterally offset from the middle region of the semiconductor layer.

3. The image sensor as described in claim 1, further comprising: A doped region is located in the semiconductor layer and below the doped capping layer, wherein the doped region includes the first doping type, and wherein the doping concentration of the doped region is less than the doping concentration of the doped capping layer and the doping concentration of the doped peripheral region.

4. The image sensor as claimed in claim 1, further comprising: An interlayer is disposed between the semiconductor layer and the substrate, wherein the interlayer comprises the first material, and wherein the doped peripheral region extends through the thickness of the interlayer.

5. The image sensor of claim 1, wherein the doped peripheral region extends laterally from the outer wall of the doped capping layer to a first point in a direction away from the semiconductor layer, wherein the peak doping concentration of the doped peripheral region is closer to the outer wall of the doped capping layer than the first point.

6. The image sensor of claim 1, wherein the bottom surface of the semiconductor layer is perpendicularly offset from the top surface of the substrate by a non-zero distance, wherein the doped capping layer extends along the opposite sidewalls of the semiconductor layer, and wherein the doped peripheral region is located below the doped capping layer.

7. A method for forming an image sensor, comprising: A sandwich layer is formed on a substrate, wherein the substrate comprises a first material having a first bandgap; A semiconductor layer is formed on the interlayer, wherein the semiconductor layer includes a second material having a second bandgap smaller than the first bandgap; a doped capping layer is formed on the top surface of the semiconductor layer, wherein the doped capping layer includes one or more first dopants and extends continuously between opposite sidewalls of the semiconductor layer; and a doped peripheral region is formed in the interlayer and the substrate, wherein the doped peripheral region is adjacent to opposite edges of the doped capping layer and includes the one or more first dopants, wherein in a top view, the doped peripheral region is substantially annular; wherein the substrate includes opposite sidewalls defining a recess, wherein the semiconductor layer is formed in the recess and the top surface of the semiconductor layer is lower than the top surface of the substrate; wherein the doped capping layer extends along the top surface of the semiconductor layer between the opposite sidewalls of the substrate; wherein the doped peripheral region extends continuously laterally from the outer sidewall of the doped capping layer in a direction away from the semiconductor layer.

8. The method as described in claim 7, wherein the doping concentration of the doped peripheral region is less than the doping concentration of the doped capping layer.

9. A method for forming an image sensor, comprising: A semiconductor layer is formed on a substrate, wherein the substrate comprises a first material and the semiconductor layer comprises a second material different from the first material; A doped capping layer is formed on the top surface of the semiconductor layer, wherein the doped capping layer is formed by epitaxial layer and in-situ doping with one or more first dopants having a first doping type; and an annealing process is performed to form a doped peripheral region in the substrate and on the opposite side of the doped capping layer, wherein the doped peripheral region includes the first doping type, and wherein the annealing process drives the one or more first dopants from the doped capping layer into the substrate, wherein the substrate includes opposite sidewalls defining a groove, wherein the semiconductor layer is formed in the groove and the top surface of the semiconductor layer is lower than the top surface of the substrate, wherein the doped capping layer extends along the top surface of the semiconductor layer between the opposite sidewalls of the substrate, and wherein the doped peripheral region extends continuously laterally from the outer sidewall of the doped capping layer in a direction away from the semiconductor layer.

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