US-20260129319-A1 - SYSTEM AND METHOD FOR ENHANCING PARASITIC LIGHT SENSITIVITY OF IMAGE SENSOR

US20260129319A1US 20260129319 A1US20260129319 A1US 20260129319A1US-20260129319-A1

Abstract

An image sensor is disclosed. The image sensor includes a plurality of image pixels. Each image pixel includes a semiconductor region having a photodiode and a light-sensitive electrical element. Each image pixel further includes a primary metalens. The primary metalens includes a dielectric layer and a plurality of nanostructures arranged within the dielectric layer. Each of the plurality of nanostructures has a first refractive index that is greater than a second refractive index of the dielectric layer. The plurality of nanostructures is patterned within the dielectric layer to direct light received by the image pixel away from the light-sensitive electrical element.

Inventors

Byounghee Lee
Andrew Eugene PERKINS

Assignees

SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC

Dates

Publication Date: 20260507
Application Date: 20241104

Claims (20)

1 . A image sensor comprising: a plurality of image pixels, each image pixel comprising: a semiconductor region including a photodiode and a light-sensitive electrical element; and a primary metalens comprising: a dielectric layer; and a plurality of nanostructures arranged within the dielectric layer, wherein: each of the plurality of nanostructures has a first refractive index that is greater than a second refractive index of the dielectric layer; and the plurality of nanostructures is patterned within the dielectric layer to direct light received by the image pixel away from the light-sensitive electrical element.
2 . The image sensor of claim 1 , wherein: each image pixel further includes a local readout circuit comprising at least the light-sensitive electrical element; and the light-sensitive electrical element is one of an NMOS transistor, a PMOS transistor, and a capacitor of the local readout circuit.
3 . The image sensor of claim 1 , wherein the plurality of nanostructures is patterned to asymmetrically direct light received by the image pixel.
4 . The image sensor of claim 1 , wherein the plurality of nanostructures is patterned to transmit light in a first band of wavelengths and to filter out light in a second band of wavelengths.
5 . The image sensor of claim 1 , wherein: the dielectric layer comprises silicon dioxide; and each of the plurality of nanostructures arranged within the dielectric layer comprises one of silicon nitride and titanium dioxide.
6 . The image sensor of claim 1 , wherein a diameter of a focal area of the primary metalens for a wavelength of light is less than the wavelength.
7 . The image sensor of claim 1 , wherein each image pixel further includes a diffusing layer located above the primary metalens and configured to normalize angled light received by the image pixel.
8 . The image sensor of claim 7 , wherein the diffusing layer includes a secondary metalens comprising: a second dielectric layer; and a second plurality of nanostructures arranged within the second dielectric layer, the second plurality of nanostructures patterned to normalize angled light received by the image pixel.
9 . The image sensor of claim 8 , wherein: the second dielectric layer of the secondary metalens comprises a same dielectric material as the dielectric layer of the primary metalens; and the second plurality of nanostructures of the secondary metalens comprises a same nanostructure material as the plurality of nanostructures of the primary metalens.
10 . An imaging system comprising: an imaging controller; and a camera module comprising: a lens system coupled to the imaging controller; an image sensor communicatively coupled to the imaging controller and comprising a plurality of image pixels, each image pixel the plurality of image pixels comprising: a semiconductor region including a photodiode and a light-sensitive electrical element; and a primary metalens comprising: a dielectric layer; and a plurality of nanostructures arranged within the dielectric layer, wherein: each of the plurality of nanostructures has a first refractive index that is greater than a second refractive index of the dielectric layer; and the plurality of nanostructures is patterned within the dielectric layer to direct light received by the image pixel away from the light-sensitive electrical element.
11 . The imaging system of claim 10 , wherein the plurality of nanostructures is patterned to asymmetrically direct light received by the image pixel.
12 . The imaging system of claim 10 , wherein: the dielectric layer comprises silicon dioxide; and each of the plurality of nanostructures arranged within the dielectric layer comprises one of silicon nitride and titanium dioxide.
13 . The imaging system of claim 10 , wherein a diameter of a focal area of the primary metalens for a wavelength of light is less than the wavelength.
14 . The imaging system of claim 10 , wherein each image pixel further includes a diffusing layer located above the primary metalens and configured to normalize angled light received by the image pixel.
15 . The imaging system of claim 14 , wherein the diffusing layer includes a secondary metalens comprising: a second dielectric layer; and a second plurality of nanostructures arranged within the second dielectric layer, the second plurality of nanostructures patterned to normalize angled light received by the image pixel.
16 . The imaging system of claim 15 , wherein: the second dielectric layer of the secondary metalens comprises a same dielectric material as the dielectric layer of the primary metalens; and the second plurality of nanostructures of the secondary metalens comprises a same nanostructure material as the plurality of nanostructures of the primary metalens.
17 . A method of operating an image sensor, the method comprising: receiving light from a scene at an image pixel of the image sensor; diffracting the light, with a primary metalens, into a semiconductor region that includes a photodiode and a light-sensitive electrical element; directing the light with the primary metalens into a focal area within the semiconductor region that is separate from the light-sensitive electrical element; and producing an electrical signal with the photodiode responsive to absorption of the light in the semiconductor region.
18 . The method of claim 17 , further comprising normalizing, with a diffusing layer, an angularity of the light received by the image pixel prior to passage through the primary metalens.
19 . The method of claim 17 , wherein the light is asymmetrically directed by the primary metalens.
20 . The method of claim 17 , wherein directing the light with the primary metalens comprises transmitting a first band of wavelengths of the light and filtering out a second band of wavelengths of the light.

Description

TECHNICAL FIELD The disclosure relates generally to image sensors, and particularly to techniques for improving parasitic light sensitivity of image sensors. BACKGROUND Image sensors are used in electronic devices such as cellular telephones, cameras, and computers to capture images. An electronic device may be provided with an image sensor including an array of image pixels arranged in a grid pattern. Each image pixel may receive photons, such as light, and may convert the photons into electrical signals. The inventors of embodiments of the present disclosure have recognized that image pixels may include structures that are sensitive to parasitic light. The inventors of embodiments of the present disclosure have further recognized that the sensitivity of image pixel structures to parasitic light may affect the parasitic light sensitivity of the image sensor as a whole. Embodiments of the present disclosure may address one or more of these challenges. BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present embodiments may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features. FIG. 1 illustrates a block diagram of an imaging system in accordance with embodiments of the present disclosure. FIG. 2 illustrates a block diagram of an example image sensor in accordance with embodiments of the present disclosure. FIG. 3 illustrates a block diagram of exemplary components of an image pixel in accordance with embodiments of the present disclosure. FIGS. 4A-4B illustrate side cross-sectional views of image pixels in accordance with embodiments of the present disclosure. FIG. 5 illustrates a side cross-sectional view of image pixels in accordance with embodiments of the present disclosure. FIG. 6A illustrates a top view of an example metalens in accordance with embodiments of the present disclosure. FIG. 6B illustrates a top view of a focal area of an example metalens in accordance with embodiments of the present disclosure. FIG. 7 illustrates a side cross-sectional view of image pixels in accordance with embodiments of the present disclosure. FIG. 8 illustrates a side cross-sectional view of an image pixel in accordance with embodiments of the present disclosure. FIG. 9 illustrates a method of operating an image sensor in accordance with embodiments of the present disclosure. DETAILED DESCRIPTION Details of one or more embodiments are set forth in the description below and the accompanying drawings. Other features will be apparent from the description, drawings, and from the claims. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art understands that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment. Various terms are used to refer to particular system components. Different companies may refer to a component by different names, and this disclosure does not intend to distinguish between components that differ in name but not form and function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” Also, the term “couple” or “coupled” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect connection via other devices and connections. Terms defining an elevation, such as “above,” “below,” “upper,” and “lower,” shall be locational terms in reference to a direction of light incident upon a pixel array and/or an image pixel. Unless otherwise specified, light entering shall be considered to interact with or pass objects and/or structures that are “above” and “upper” before interacting with or passing objects and/or structures that are “below” or “lower.” Thus, the locational terms may not have any relationship to the direction of the force of gravity. Various examples disclosed herein are directed to imaging systems, image sensors, image pixels, and related methods. More particularly, at least some of the examples disclosed herein are directed to image pixels of an image sensor that are designed and constructed to have a smaller parasitic light sensitivity by focusing the light received by the image pixel away from light-sensitive electrical elements that contribute to the parasitic light sensitivity of the image pixel. At least some examples are directed to the use of a metalens including a plurality of nanostructures configured and patterned within a dielec