Reflective Pixel Isolation Structure for High-Quantum-Efficiency Image Sensors
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Solution Overview
Problem
The challenge in the semiconductor industry is to form reliable image sensor devices with smaller feature sizes, as the decreasing geometric sizes complicate fabrication processes and lead to difficulties in achieving high quantum efficiency and reducing crosstalk between pixels.
Innovation Solution
The implementation of a deep trench reflective isolation structure that increases the optical path of incident light by reflecting it within the pixels and blocking light from neighboring pixels, using a reflective element and a filling dielectric to enhance quantum efficiency and prevent crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes are reduced to increase functional density, then more pixels can be packed into the same chip area, but fabrication processes become more difficult and reliability decreases
Solution Approach 1:
The pixel structure is segmented into distinct functional regions including photoactive regions, isolation regions with reflective elements, and interconnection regions. This segmentation allows each region to be optimized independently for its specific function while maintaining overall device reliability despite reduced feature sizes
Solution Approach 2:
Different regions of the pixel structure are assigned different material compositions and structural properties tailored to their specific functions. For example, the isolation regions contain reflective elements with specific optical properties, while photoactive regions are optimized for light absorption and charge generation
2Productivity
If feature sizes are reduced to increase functional density, then more pixels can be packed into the same chip area, but manufacturing complexity increases
Solution Approach 1:
The isolation structure serves multiple functions simultaneously: it provides electrical isolation between pixels, reflects light back to the photoactive region to increase quantum efficiency, and defines pixel boundaries. This multi-functionality reduces the need for separate structures for each function, thereby simplifying the overall manufacturing process
Solution Approach 2:
The reflective element is integrated within the isolation region structure, combining the isolation function and light reflection function into a single structural unit. This merging eliminates the need for separate reflection layers or structures, reducing processing steps and manufacturing complexity
3Ease of manufacture
If standard isolation structures are used without reflective elements, then fabrication is simpler, but quantum efficiency is reduced due to light loss
Solution Approach 1:
The isolation region, which would normally be a source of light loss and crosstalk, is converted into a beneficial light-reflecting structure. By incorporating reflective elements into the isolation regions, light that would have been lost is instead reflected back to the photoactive region, increasing quantum efficiency while maintaining the isolation function
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 design improves quantum efficiency by increasing light intensity received by pixels and reduces crosstalk between pixels, enabling more effective light detection and image sensing.
Implementation Method 1
a reflective element in the semiconductor substrate between the image sensing elements. The high-k dielectric structure is between the reflective element and the image sensing elements
Implementation Method 2
An image sensor device includes a pixel array (or grid) for detecting light and recording intensity (brightness) of the detected light. The pixel array responds to the light by accumulating a charge.
Data Source
AI summary
An image sensor structure includes a semiconductor substrate, a plurality of image sensing elements, a reflective element, and a high-k dielectric structure. The image sensing elements are in the semiconductor substrate. The reflective element is in the semiconductor substrate and between the image sensing elements. The high-k dielectric structure is between the reflective element and the image sensing elements.