Pixel Sensor Lens Structure for Near-Infrared Quantum Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CMOS image sensors exhibit low quantum efficiency for near infrared light, leading to inadequate sensitivity in low-light conditions, despite modifications like germanium single-photon avalanche photodiodes and isolation grids, which fail to meet performance thresholds.
Innovation Solution
Incorporating a lens structure with a convex surface, an optical spacer, and anti-reflective coatings to redirect and enhance the absorption of near infrared light by the photodiode, increasing quantum efficiency and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If germanium single-photon avalanche photodiodes and isolation grids are used, then sensitivity to near infrared light is improved, but quantum efficiency remains below performance thresholds
Solution Approach 1:
The pixel sensor structure is segmented into distinct functional regions: a photodiode sensor structure for light detection, an isolation grid structure for electrical isolation, and a lens structure for optical focusing. This segmentation allows each component to be optimized independently, with the lens structure specifically designed to redirect near-infrared light onto the photodiode surface, thereby improving quantum efficiency while maintaining the sensitivity enhancements from the germanium photodiode and isolation grid
Solution Approach 2:
A lens structure acts as an intermediary component between the incident near-infrared light and the photodiode sensor structure. This lens redirects and focuses the near-infrared light onto the photodiode surface, serving as a mediating element that enhances light coupling and improves quantum efficiency without interfering with the sensitivity-enhancing features of the germanium photodiode and isolation grid
2Manufacturing precision
If lens structure and optical spacer are added, then quantum efficiency and sensitivity are improved, but device complexity increases
Solution Approach 1:
The lens structure, optical spacer, and photodiode are combined into an integrated pixel sensor structure where the lens is positioned directly over the photodiode with the optical spacer maintaining a specific separation distance. This merging of components into a unified structure achieves improved quantum efficiency through enhanced near-infrared light coupling while minimizing the complexity increase by integrating rather than adding separate subsystems
Solution Approach 2:
The optical spacer introduces a controlled vertical dimension between the lens structure and photodiode surface, creating a specific separation distance that optimizes light focusing. This dimensional approach allows the lens to focus near-infrared light onto the photodiode surface from an optimized focal distance, improving quantum efficiency while maintaining a compact overall structure that doesn't excessively increase device complexity
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 significantly improves quantum efficiency and sensitivity of CMOS image sensors in low-light environments, reducing resource consumption and meeting performance thresholds.
Implementation Method 1
The lens structure redirects near infrared light through the optical spacer structure and to the photodiode sensor structure
Implementation Method 2
As the photodiode is exposed to light, an electrical charge is induced in the photodiode (referred to as a photocurrent)
Data Source
AI summary
Some implementations herein include a pixel sensor structure and methods of forming. The pixel sensor structure includes a lens structure, a photodiode sensor structure, and an optical spacer structure between the lens structure and the photodiode sensor structure. The lens structure redirects near infrared light through the optical spacer structure and to the photodiode sensor structure to improve the quantum efficiency performance of the photodiode sensor structure relative to another photodiode sensor structure include in a pixel sensor structure without the lens structure and the optical spacer structure. Additionally, different configurations of an anti-reflection coating layer may be included throughout the pixel sensor structure to improve the quantum efficiency performance of the photodiode sensor structure further.