US-12628463-B2 - Methods and system of enhanced near-infrared light absorption of imaging systems using metasurfaces and nanostructures

Abstract

A pixel for an imaging sensor is disclosed that includes a photodetector and a metasurface. The photodetector includes a first surface and sidewalls that extend into the photodetector in a first direction from the first surface. The metasurface is formed on the first surface and includes nanostructures that bend a predetermined range of wavelengths of light at least 70 degrees in opposing angles from a direction that is substantially perpendicular to the first surface, and a standing wave pattern forms in an active region of the pixel. The predetermined range of wavelengths of light includes 700 nm to 1100 nm inclusive. In one embodiment, the pixel is a silicon-based photodetector, a thickness of the pixel in the first direction is less than or equal to 5 μm, and the pixel absorbs at least 20% of a power of the predetermined range of wavelengths of light.

Inventors

• Radwanul Hasan SIDDIQUE
• Yibing Michelle Wang
• Mahdad MANSOUREE

Assignees

• SAMSUNG ELECTRONICS CO., LTD.

Dates

Publication Date

20260512

Application Date

20220324

Claims (20)

1. 1 . A pixel for an imaging sensor, comprising: a photodetector comprising a first surface and sidewalls that extend into the photodetector in a first direction from the first surface; and a metasurface on the first surface, the metasurface comprising nanostructures that bend Near Infrared (NIR) radiation in a predetermined range of wavelengths at an angle of at least 70 degrees from a direction that is substantially perpendicular to the first surface, wherein the metasurface is within the sidewalls and receives the NIR radiation through a microlens on the metasurface, and wherein the sidewalls are reflecting to create spatially localized resonances of a target wavelength that lengthens a path of the NIR radiation.
2. 2 . The pixel of claim 1 , wherein the metasurface bends the predetermined range of wavelengths of light at least 70 degrees in opposing angles from the direction that is substantially perpendicular to the first surface.
3. 3 . The pixel of claim 1 , wherein the predetermined range of wavelengths of light comprises 700 nm to 1100 nm inclusive.
4. 4 . The pixel of claim 1 , wherein the pixel comprises a thickness in the first direction of less than or equal to 5 μm.
5. 5 . The pixel of claim 1 , wherein a standing wave pattern forms in an active region of the pixel.
6. 6 . The pixel of claim 1 , wherein the photodetector comprises a silicon-based photodetector, and wherein the pixel absorbs at least 20% of a power of the predetermined range of wavelengths of light.
7. 7 . The pixel of claim 6 , wherein the photodetector comprises an avalanche photodiode, a single photon avalanche diode, a quanta image sensor or a PIN diode.
8. 8 . The pixel of claim 1 , wherein the sidewalls comprise deep trench isolation (DTI) structures.
9. 9 . The pixel of claim 8 , wherein the sidewalls comprises a metal or a doped semiconductor material.
10. 10 . The pixel of claim 1 , further comprising an anti-reflective coating formed on the metasurface opposite the first surface.
11. 11 . The pixel of claim 1 , wherein the pixel is part of an array of pixels.
12. 12 . A pixel for an imaging sensor, comprising: a photodetector comprising a first surface, a first sidewall and a second sidewall, the first sidewall and the second sidewall extending into the photodetector in a first direction from the first surface on opposite sides of the photodetector; and a metasurface on the first surface, the metasurface comprising nanostructures that bend Near Infrared (NIR) radiation in a predetermined range of wavelengths at an angle of at least 70 degrees from a direction that is substantially perpendicular to the first surface toward the first sidewall and at least 70 degrees from the direction that is substantially perpendicular to the first surface toward the second sidewall, wherein the metasurface is within the first and second sidewalls and receives the NIR radiation through a microlens on the metasurface, and wherein the first and second sidewalls are reflecting to create spatially localized resonances of a target wavelength that lengthens a path of the NIR radiation.
13. 13 . The pixel of claim 12 , wherein the predetermined range of wavelengths of light comprises 700 nm to 1100 nm inclusive.
14. 14 . The pixel of claim 12 , wherein the pixel comprises a thickness in the first direction of less than or equal to 5 μm.
15. 15 . The pixel of claim 12 , wherein a standing wave pattern forms in an active region of the pixel.
16. 16 . The pixel of claim 12 , wherein the photodetector comprises a silicon-based photodetector, and wherein the pixel absorbs at least 20% of a power of the predetermined range of wavelengths of light.
17. 17 . The pixel of claim 16 , wherein the photodetector comprises an avalanche photodiode, a single photon avalanche diode, a quanta image sensor or a PIN diode.
18. 18 . The pixel of claim 12 , wherein the first sidewall and the second sidewall comprise deep trench isolation (DTI) structures.
19. 19 . The pixel of claim 18 , wherein the first sidewall and the second sidewall comprise a metal or a doped semiconductor material.
20. 20 . The pixel of claim 12 wherein the pixel is part of an array of pixels.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the priority benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 63/186,775, filed on May 10, 2021, and U.S. Provisional Patent Application No. 63/299,912, filed on Jan. 14, 2022, the disclosures of which are incorporated herein by reference in their entirety. TECHNICAL FIELD The subject matter disclosed herein relates to metasurfaces and nanostructured surfaces. More particularly, the subject matter disclosed here relates to a metasurface that bends Near-infrared (NIR) radiation at a target wavelength in high-degree opposing angles to maximize absorption of the NIR radiation in a CMOS image sensor (CIS). BACKGROUND NIR sensing technology has been extensively applied in Time-of-Flight (ToF), surveillance, machine vision, augmented reality (AR), virtual reality (VR), biological inspection, and optical communications. Silicon-based CISs, however, have insufficient sensitivity and low QE because silicon has a low NIR wavelength absorption, especially for wavelengths greater than 900 nm. At NIR wavelengths, absorption by silicon is low and most of the incident power (˜80%) passes through the active region of a CIS. FIGS. 1A and 1B are graphs that respectively show absorption coefficient and absorption depth of silicon. In the graph of FIG. 1A, the absorption coefficient for a range of NIR wavelengths is about 1×10−3 per cm at 700 nm to about 1×10−2 per cm at 1200 nm. In the graph of FIG. 1B, the absorption depth for the same range of NIR wavelengths is about 1×10−3 cm at 700 nm to between about 1×10−2 cm and 1×10−1 cm at 1200 nm. Thus, the absorption depth for this range of NIR wavelengths is well beyond the depth of most CMOS image sensors, which is typically between 100 nm to 1000 nm. SUMMARY An example embodiment provides a pixel for an imaging sensor that may include a photodetector having a first surface and sidewalls that extend into the photodetector in a first direction from the first surface, and a metasurface on the first surface in which the metasurface may include nanostructures that bend a predetermined range of wavelengths of light at least 70 degrees from a direction that is substantially perpendicular to the first surface. In one embodiment, the metasurface bends the predetermined range of wavelengths of light at least 70 degrees in opposing angles from the direction that is substantially perpendicular to the first surface. In another embodiment, the predetermined range of wavelengths of light may include 700 nm to 1100 nm inclusive. In still another embodiment, the pixel may have a thickness in the first direction of less than or equal to 5 μm. In still another embodiment, a standing wave pattern forms in an active region of the pixel. In one embodiment, the photodetector comprises a silicon-based photodetector, and the pixel absorbs at least 20% of a power of the predetermined range of wavelengths of light. In another embodiment, the photodetector may be an avalanche photodiode, a single photon avalanche diode, a quanta image sensor or a PIN diode. In still another embodiment, the sidewalls may be deep trench isolation (DTI) structures, and may be formed from a metal or a doped semiconductor material. In yet another embodiment, the pixel may further include an anti-reflective coating formed on the metasurface opposite the first surface. In one embodiment, the pixel may be part of an array of pixels. An example embodiment provides a pixel for an imaging sensor that may include a photodetector having a first surface, a first sidewall and a second sidewall in which the first sidewall and the second sidewall extend into the photodetector in a first direction from the first surface on opposite sides of the photodetector, and a metasurface on the first surface in which the metasurface may include nanostructures that bend a predetermined range of wavelengths of light at least 70 degrees from a direction that is substantially perpendicular to the first surface toward the first sidewall and at least 70 degrees from the direction that is substantially perpendicular to the first surface toward the second sidewall. In one embodiment, the predetermined range of wavelengths of light may include 700 nm to 1100 nm inclusive. In another embodiment, the pixel may have a thickness in the first direction of less than or equal to 5 μm. In still another embodiment, a standing wave pattern forms in an active region of the pixel. In yet another embodiment, the photodetector may include a silicon-based photodetector, and the pixel absorbs at least 20% of a power of the predetermined range of wavelengths of light. In one embodiment, the photodetector may be an avalanche photodiode, a single photon avalanche diode, a quanta image sensor or a PIN diode. In another embodiment, the first sidewall and the second sidewall may be deep trench isolation (DTI) structures, and the first sidewall and the second sidewall may be a metal or a doped semico