Deep Trench Isolation Layout for NIR CMOS Image Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS image sensors face challenges in providing high-quality images in visible light and improved sensitivity in infrared and near-infrared spectra, particularly due to issues with deep trench isolation structures that can lead to substrate cracking and void formation, affecting quantum efficiency and light sensitivity.
Innovation Solution
The implementation of deep trench isolation structures with a wide and narrow portion configuration and cell deep trench isolation structures within pixel cells, which reduces void formation and substrate cracking, enhancing near-infrared light sensitivity and quantum efficiency while minimizing optical and electrical cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trench isolation structures are used to reduce optical and electrical cross-talk between pixels, then isolation performance is improved, but substrate cracking and void formation occur reducing reliability
Solution Approach 1:
The patent applies local quality by creating different trench widths at different depths within the isolation structure. The trench has a first width at the top portion and a second width at the bottom portion, allowing the structure to provide effective isolation at the critical interfaces while maintaining substrate integrity at deeper levels where cracking is less likely to occur.
Solution Approach 2:
The isolation trench is segmented into multiple depth zones with different width characteristics. This segmentation allows the trench to fulfill multiple functions: providing strong isolation at critical interfaces where narrower widths are effective, while maintaining wider openings at other depths to prevent void formation and substrate stress concentration.
2Object-affected harmful factors
If deep trench isolation structures with high aspect ratios are formed to improve isolation, then cross-talk reduction is enhanced, but void formation increases reducing manufacturing precision
Solution Approach 1:
The patent implements local quality by varying the trench width along its depth. The trench maintains a narrower width at specific critical depths to provide effective optical isolation, while having wider openings at other depths to facilitate complete material filling and prevent void formation during the isolation layer deposition process.
3Device complexity
If conventional deep trench isolation structures are used, then device complexity is reduced, but near-infrared light sensitivity and quantum efficiency deteriorate
Solution Approach 1:
The patent applies local quality by creating depth-dependent width variations in the isolation trench. This allows the trench to provide effective optical isolation at critical depths where narrower widths block cross-talk, while maintaining wider sections that permit near-infrared light transmission to the photodetector, thereby improving NIR sensitivity without significantly increasing 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
This configuration improves the sensitivity and reliability of image sensors in near-infrared and infrared light regimes, reducing substrate cracking and enhancing quantum efficiency, thereby providing better image quality in low-light conditions.
Implementation Method 1
The image sensor includes an array of pixels having photosensitive elements (e.g., photodiodes) that absorb a portion of the incident image light and generate image charge upon absorption of the image light
Data Source
AI summary
A pixel includes a semiconductor substrate having a first side and a second side. Extending from the first side is a first deep trench isolation (DTI) structure and a second DTI structure. The first DTI structure includes a wide portion and a narrow portion extending from the wide portion. A first width of the wide portion is greater than a second width of the narrow portion, and the wide portion extends to a first depth. The pixel further includes a photodiode region disposed in the semiconductor substrate between the first DTI structure and the second DTI structure. A cell deep trench isolation (CDTI) structure is disposed between the wide portion of the first DTI structure and the second DTI structure. The CDTI structure extends to a second depth. The first depth and the second depth extend a substantially equal distance from the first side of the semiconductor substrate.