Backside Imaging Pixel Reflector Layout for Crosstalk Reduction
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Solution Overview
Problem
Backside illumination type solid-state imaging devices suffer from crosstalk due to light being transmitted through the photoelectric conversion layer and reflected by the metal wiring layer, leading to reduced image quality, color reproducibility, and brightness differences, particularly with near-infrared light. Existing solutions either fail to efficiently utilize transmitted light or complicate the manufacturing process with concave reflectors.
Innovation Solution
A solid-state imaging device with a reflective structure having predetermined electromagnetic characteristics, specifically a metamaterial structure with a gap surface plasmon (GSP) configuration, is placed between the metal wiring pattern and the photoelectric conversion layer to reflect and condense light back onto the photoelectric conversion element, preventing crosstalk and enhancing light utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal wiring layer is disposed on the backside of the photoelectric conversion layer, then electrical connections and signal transmission are achieved, but light is reflected by the metal wiring layer causing crosstalk between adjacent pixels
Solution Approach 1:
A reflective structure with predetermined electromagnetic characteristics is introduced as an intermediary between the metal wiring layer and the photoelectric conversion layer. This intermediary selectively reflects near-infrared light back toward the incident surface while allowing other wavelengths to pass through, thereby preventing crosstalk caused by direct metal layer reflection while maintaining electrical connectivity.
2Object-affected harmful factors
If polarization units with different polarization characteristics are disposed corresponding to adjacent pixels, then crosstalk is reduced, but light utilization efficiency decreases because transmitted light is not reflected back to the original pixel
Solution Approach 1:
The reflective structure converts the harmful effect of light transmission through the photoelectric conversion layer into a beneficial effect by reflecting this transmitted light back toward the incident surface and the original photoelectric conversion element. This transforms what would be lost light into useful signal, improving overall light utilization efficiency while preventing crosstalk.
3Reliability
If a concave reflector is provided on the opposite side of the substrate, then light reflection is improved, but the device thickness increases and manufacturing complexity increases
Solution Approach 1:
The reflective structure utilizes predetermined electromagnetic characteristics (such as resonant frequency, impedance matching, or metamaterial properties) to achieve effective light reflection without requiring the geometric complexity of a concave shape. By changing from geometric reflection to electromagnetic parameter-based reflection, the device achieves thin-profile construction with simplified manufacturing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents crosstalk, improves image quality by reusing transmitted light, and simplifies the manufacturing process by eliminating the need for thick concave reflectors, resulting in a thinner and more precise imaging device.
Implementation Method 1
a reflective structure disposed corresponding to each of the plurality of photoelectric conversion elements between the predetermined metal wiring pattern and the photoelectric conversion layer, the reflective structure having predetermined electromagnetic characteristics
Implementation Method 2
the reflective structure condenses and reflects light transmitted through each photoelectric conversion element of the photoelectric conversion layer at and to the photoelectric conversion element
Implementation Method 3
a photoelectric conversion layer provided on the wiring layer and including a plurality of photoelectric conversion elements that are formed in an array to generate charges by photoelectric conversion based on light incident on an incident surface
Data Source
AI summary
The present invention is a solid-state imaging device including: a semiconductor support substrate; a wiring layer formed on the semiconductor support substrate and including a predetermined metal wiring pattern; a photoelectric conversion layer provided on the wiring layer and including a plurality of photoelectric conversion elements that are formed in an array to generate charges by photoelectric conversion based on light incident on an incident surface; and a reflective structure disposed corresponding to each of the plurality of photoelectric conversion elements between the predetermined metal wiring pattern and the photoelectric conversion layer, the reflective structure having predetermined electromagnetic characteristics. Among the light incident on the photoelectric conversion layer, the reflective structure condenses and reflects light transmitted through each photoelectric conversion element of the photoelectric conversion layer at and to the photoelectric conversion element.