Deep Pixel Isolation Structure for Low-Noise Image Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing CMOS image sensors face challenges in preventing cross-talk and minimizing noise, which affect their performance and signal-to-noise ratio.
Innovation Solution
The image sensor design incorporates a substrate with a deep device isolation pattern that includes a semiconductor pattern penetrating the substrate and an isolation pattern between the substrate and the semiconductor pattern. This design uses different materials for the isolation patterns adjacent to the first and second surfaces of the substrate, effectively preventing cross-talk and minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional device isolation pattern is used in CMOS image sensors, then the manufacturing process is simple, but cross-talk between pixel regions occurs and noise increases
Solution Approach 1:
The device isolation pattern is segmented into multiple distinct layers: a shallow device isolation pattern (first isolation layer) and a deep device isolation pattern (second isolation layer). This segmentation allows each layer to perform specific functions - the shallow layer provides basic isolation while the deep layer prevents cross-talk and reduces noise, thereby resolving the contradiction between simple structure and effective cross-talk prevention.
Solution Approach 2:
Different regions of the isolation structure are assigned different materials and depths. The first isolation layer uses a first material for basic isolation, while the second isolation layer uses a second material for enhanced cross-talk prevention. This local differentiation of properties allows the structure to simultaneously maintain manufacturing feasibility and achieve superior noise reduction performance.
2Reliability
If a deep device isolation pattern with multiple materials is implemented, then cross-talk is prevented and noise is minimized, but the manufacturing complexity increases
Solution Approach 1:
The shallow device isolation pattern is formed first as a preliminary structure, establishing the basic isolation framework before the deep device isolation pattern is added. This preliminary action allows subsequent processing steps to build upon an already-established foundation, simplifying the overall manufacturing sequence despite the multi-layer complexity.
Solution Approach 2:
The deep device isolation pattern is nested within and complementary to the shallow device isolation pattern structure. The two isolation layers are integrated in a nested configuration where the first isolation layer provides the upper portion and the second isolation layer provides the deeper portion, allowing both structures to coexist and function together without requiring completely separate fabrication processes.
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 proposed design effectively prevents cross-talk between pixel regions and minimizes noise, thereby improving the signal-to-noise ratio and overall performance of the CMOS image sensor.
Implementation Method 1
Each of the pixels may include a photodiode (PD). The photodiode may convert incident light into an electrical signal.
Data Source
AI summary
An image sensor includes a substrate including pixel regions and having a first surface, a second surface opposite the first surface, and a first trench recessed from the first surface, a shallow device isolation pattern provided in the first trench, and a deep device isolation pattern between the pixel regions and provided in the substrate. The deep device isolation pattern includes a semiconductor pattern penetrating at least a portion of the substrate, and an isolation pattern provided between the substrate and the semiconductor pattern. The isolation pattern includes a first isolation pattern adjacent to the second surface, and a second isolation pattern adjacent to the first surface. A first interface at which the first isolation pattern contacts the second isolation pattern is spaced apart from the shallow device isolation pattern. The first isolation pattern includes a different material from that of the second isolation pattern.