Deep Trench Isolation Spacer for CMOS Image Sensor Cross-Talk
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CMOS image sensors face issues with cross-talk due to poor isolation between pixels, which affects the performance of devices like digital cameras and mobile phone cameras.
Innovation Solution
A semiconductor device with deep trench isolation (DTI) is developed, featuring a spacer and a doped region on the sidewalls of deep trenches in a silicon substrate, protecting the top surface regions from implantation processes and allowing for independent adjustment of doping concentrations without affecting pixel characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If deep trench isolation is formed without a spacer, then the manufacturing process is simpler, but the top surface regions are affected by the implantation process for forming the doped region
Solution Approach 1:
A spacer layer is introduced as an intermediary protective element between the implantation source and the top surface regions that need protection. The spacer is formed on the sidewall of the deep trench at a first position, extending from the surface toward the bottom, and acts as a physical barrier during ion implantation to prevent dopants from reaching and altering the characteristics of regions near the top surface.
2Object-affected harmful factors
If doping concentration is increased to improve isolation, then cross-talk reduction is enhanced, but pixel characteristics are negatively affected
Solution Approach 1:
The deep trench structure is segmented into distinct regions along its length. The spacer divides the trench into an upper region (protected from implantation) and a lower region (subject to implantation). This segmentation allows independent control of doping in different zones, enabling high doping concentrations in the lower region for cross-talk suppression while keeping the upper region undoped to maintain pixel characteristics.
Solution Approach 2:
Different regions of the deep trench are given different doping characteristics. The lower portion receives heavy implantation for strong isolation, while the upper portion remains protected and maintains its original properties. This local differentiation of doping quality enables simultaneous achievement of cross-talk reduction and pixel performance preservation.
3Reliability
If implantation is performed to form doped region, then isolation between pixels is improved, but the characteristics of semiconductor device are influenced
Solution Approach 1:
The spacer is formed in advance before the implantation process. This preliminary action establishes the protective barrier that will control the subsequent implantation, ensuring that only specific regions receive dopants while other regions are protected. The spacer's position and dimensions are predetermined to achieve the desired doping pattern and isolation characteristics.
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 reduces cross-talk by providing robust isolation between pixels, protecting sensitive regions and allowing for precise control of doping concentrations, thereby enhancing the performance and reducing dark current in CMOS image sensors.
Implementation Method 1
the regions near the top surface of a silicon substrate are protected by the spacer from the implantation process for forming the doped region
Implementation Method 2
deep trench isolation (DTI) for providing good isolation between pixels
Data Source
AI summary
A semiconductor device and a manufacturing method thereof are disclosed. The semiconductor device includes a silicon substrate, a spacer, a doped region, and a deep trench isolation (DTI). The silicon substrate has a deep trench. The spacer is formed on an upper portion of the sidewall of the deep trench. The doped region is formed on a lower portion of the sidewall of the deep trench. The deep trench isolation is formed in the deep trench.