Deep Pixel Isolation Layout for Dense Image Sensors
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Solution Overview
Problem
Current CMOS image sensors face challenges in minimizing cross-talk between pixels and maintaining gate electrode size as integration density increases, leading to potential deterioration in image sensor performance.
Innovation Solution
The implementation of a deep device isolation pattern with specific portions spaced apart in different directions between pixel regions, along with extended active patterns, helps minimize cross-talk and allows for increased gate electrode size, thereby enhancing integration density without reducing gate electrode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If integration density is increased, then the number of pixels per unit area increases, but gate electrode size decreases leading to performance deterioration
Solution Approach 1:
The pixel array is segmented into multiple blocks, with deep device isolation patterns strategically positioned between blocks. This segmentation allows gate electrodes in different blocks to be independently optimized for size without affecting adjacent pixels, resolving the contradiction between high integration density and sufficient gate electrode dimensions.
Solution Approach 2:
The deep device isolation pattern extends in the vertical dimension (depth) rather than only in the horizontal plane. By utilizing the third dimension for isolation, the horizontal space for gate electrodes is preserved even as pixel density increases in the planar direction.
2Productivity
If pixel size is reduced to increase integration density, then more pixels fit in the sensor area, but cross-talk between adjacent pixels increases
Solution Approach 1:
The sensor is divided into multiple pixel blocks separated by deep device isolation patterns. This segmentation creates electrical and physical barriers between adjacent pixel regions, effectively blocking cross-talk while allowing high pixel density within each block.
Solution Approach 2:
The deep device isolation pattern acts as an intermediary structure between adjacent pixel regions. This isolation pattern includes intermediate regions that specifically block the transmission of electrical signals and optical interference between pixels, preventing cross-talk without requiring larger pixel spacing.
3Object-affected harmful factors
If deep device isolation pattern is implemented, then cross-talk is minimized, but manufacturing complexity increases
Solution Approach 1:
The complex deep device isolation pattern is broken down into multiple manageable layers: a first deep device isolation pattern, intermediate regions, and a second deep device isolation pattern. This segmentation of the isolation structure itself makes the manufacturing process more controllable and less complex.
Solution Approach 2:
By implementing isolation in the vertical dimension through multiple stacked isolation layers rather than relying solely on horizontal spacing, the patent achieves effective cross-talk blocking with a more manageable manufacturing approach. Each layer can be formed using standard semiconductor 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
This approach effectively reduces cross-talk between pixels and allows for larger gate electrodes, improving the integration density and overall performance of the image sensor.
Implementation Method 1
Each of the pixels may include a photodiode (PD) that converts incident light into an electrical signal
Data Source
AI summary
An image sensor includes a substrate having a plurality of pixel regions and a deep device isolation pattern disposed in the substrate between the pixel regions. The pixel regions include first, second, third, and fourth pixel regions, which are adjacent to each other in first and second directions. The deep device isolation pattern includes first portions interposed between the first and second pixel regions and between the third and fourth pixel regions and spaced apart from each other in the second direction, and second portions interposed between the first and third pixel regions and between the second and fourth pixel regions and spaced apart from each other in the first direction. The first pixel region includes a first extended active pattern, which is extended to the second pixel region in the first direction and is disposed between the first portions of the deep device isolation pattern.