Image Sensor Device Isolation Pattern Air Gap Crosstalk
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Solution Overview
Problem
Highly integrated image sensors experience crosstalk between pixels due to reduced pixel sizes, which affects their performance in converting light into electrical signals effectively.
Innovation Solution
The implementation of a device isolation pattern with an air gap, where the upper portion of the pattern is narrower than the intermediate portion, and an insulating layer is used to cover the substrate and trench surfaces, reducing crosstalk by creating a refractive index difference that prevents light from being incident on neighboring pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel sizes are reduced to increase integration density, then the number of pixels per unit area increases, but crosstalk between adjacent pixels occurs due to reduced isolation distance
Solution Approach 1:
The device isolation pattern divides the substrate into distinct pixel regions using trenches filled with insulating material. This segmentation physically separates adjacent photodiodes, preventing optical crosstalk while maintaining high integration density by allowing pixels to be closely spaced without direct optical interference.
Solution Approach 2:
The device isolation pattern acts as an intermediary structure between adjacent pixels. The trench filled with insulating material serves as a mediating element that blocks light propagation between pixels, eliminating crosstalk while preserving the compact pixel arrangement needed for high integration density.
2Object-affected harmful factors
If device isolation patterns are added to reduce crosstalk, then crosstalk between pixels is minimized, but the device structure and manufacturing process become more complex
Solution Approach 1:
The device isolation pattern combines multiple functions into a single structure: the trench provides physical separation, the insulating material provides optical isolation, and the overall structure serves as both isolation and structural support. This merging reduces the need for additional separate isolation components, thereby limiting the increase in device complexity.
Solution Approach 2:
The device isolation pattern performs multiple functions simultaneously: it isolates pixels optically, provides mechanical support, defines pixel boundaries, and facilitates stress management in the substrate. This multi-functionality reduces the need for additional specialized structures, balancing crosstalk reduction with acceptable device complexity.
3Object-affected harmful factors
If device isolation patterns are added to reduce crosstalk, then crosstalk between pixels is minimized, but the manufacturing process steps and complexity increase
Solution Approach 1:
The trench for the device isolation pattern is formed early in the manufacturing process, before photodiode fabrication. The insulating material is then deposited to fill the trench. This preliminary formation of isolation structures allows subsequent pixel fabrication to proceed without interference, integrating isolation into the overall manufacturing flow rather than adding separate post-processing steps.
Solution Approach 2:
The device isolation structure is formed using self-aligned processes where the trench positioning is automatically aligned with pixel regions, and the insulating material fills the trench conformally. This self-service approach reduces the need for additional alignment and adjustment steps, minimizing the increase in manufacturing complexity while achieving effective crosstalk reduction.
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 solution effectively minimizes crosstalk between pixels, enhancing the image sensor's ability to convert light into electrical signals without interference, thereby improving the integration density and performance of the image sensor.
Implementation Method 1
reducing crosstalk by creating a refractive index difference that prevents light from being incident on neighboring pixels
Implementation Method 2
The photodiode may convert incident light into an electrical signal
Data Source
AI summary
An image sensor includes a substrate including a plurality of pixel regions and having a trench between the pixel regions, a photoelectric conversion part in the substrate of each of the pixel regions, and a device isolation pattern in the trench. The device isolation pattern defines an air gap. The device isolation pattern has an intermediate portion and an upper portion narrower than the intermediate portion.