Deep Isolation Dielectric Structure for Dense CMOS Image Sensors
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Solution Overview
Problem
Current CMOS image sensors face challenges in reducing defects and achieving high integration due to issues with deep isolation patterns and dielectric materials, leading to inefficiencies in pixel isolation and increased dark current.
Innovation Solution
The proposed solution involves a CMOS image sensor with a deep isolation pattern that includes a semiconductor pattern penetrating the substrate and a dielectric pattern with distinct material parts, where the first part is nitrided to prevent impurity diffusion and reduce the occurrence of white spots, enhancing pixel integration and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a deep isolation pattern with uniform dielectric material is used, then the structure is simple to manufacture, but impurity diffusion occurs and white spots appear
Solution Approach 1:
The dielectric pattern is divided into two distinct parts with different materials: a first part adjacent to the semiconductor pattern and a second part between the first part and the substrate. The first part has a thickness less than the second part. This local differentiation prevents impurity diffusion at the semiconductor-dielectric interface while maintaining overall structural integrity and reducing white spot defects.
2Productivity
If the dielectric pattern thickness is reduced to improve integration, then pixel density increases, but dark current performance deteriorates
Solution Approach 1:
By creating a non-uniform dielectric pattern where the first part has reduced thickness and the second part maintains greater thickness, the invention achieves high integration density near the semiconductor pattern while preserving dark current performance in regions closer to the substrate through the thicker second part.
3Reliability
If a single-material dielectric layer is used, then the manufacturing process is simplified, but impurity diffusion cannot be prevented
Solution Approach 1:
The dielectric pattern comprises composite materials with different properties in different regions. The first part uses a material optimized for preventing impurity diffusion at the semiconductor interface, while the second part uses a different material optimized for mechanical support and electrical isolation from the substrate, achieving both protection functions through material composition rather than uniform structure.
Solution Approach 2:
The originally uniform dielectric layer is segmented into two distinct parts with different materials and thicknesses. This segmentation allows each part to perform its specific function: the first part prevents impurity diffusion, while the second part provides structural support and electrical isolation, thereby improving reliability without significantly complicating the manufacturing process.
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 approach results in a highly integrated image sensor with reduced defects and improved dark current performance by preventing impurity diffusion and maintaining dielectric pattern thickness, thereby enhancing image quality.
Implementation Method 1
nitriding a surface of the dielectric layer by performing a nitridation process
Data Source
AI summary
An image sensor includes a substrate including a plurality of pixel regions, and a deep isolation pattern in the substrate between the pixel regions. The deep isolation pattern includes a semiconductor pattern penetrating at least a portion of the substrate, and a dielectric pattern disposed between the substrate and the semiconductor pattern. The dielectric pattern includes a first part disposed adjacent to the semiconductor pattern, and a second part disposed between the substrate and the first part. The semiconductor pattern includes a first semiconductor pattern and a second semiconductor pattern. The first semiconductor pattern is disposed between the dielectric pattern and the second semiconductor pattern. The first part of the dielectric pattern includes a material different from a material of the second part of the dielectric pattern. A thickness of the first part of the dielectric pattern is less than a thickness of the second part of the dielectric pattern.