Tilted Light Guides for Off-Center Image Sensor Pixels
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Solution Overview
Problem
Conventional image sensors with light guide structures are prone to cross-talk and have low light conversion efficiencies due to inefficient light guiding, especially for pixels located off-center in the sensor array, leading to reduced image quality.
Innovation Solution
The implementation of optimized light guide structures within image sensor pixels, where the shape, size, and location of light guides are tailored based on the pixel's distance from the center of the sensor, and the photosensitive elements are offset to match the angle of incoming light, reducing light scattering and improving alignment with the light guide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional light guide structures are used in image sensors, then light guiding is provided for central pixels, but off-center pixels experience reduced light conversion efficiency and increased cross-talk due to oblique light angles
Solution Approach 1:
The patent applies local quality by customizing light guide structures for different pixel positions within the sensor array. Central pixels receive light at normal incidence and use standard light guide configurations, while off-center pixels receive light at oblique angles and are equipped with specially designed light guide structures that compensate for the angled incidence. This localized optimization ensures uniform light conversion efficiency across all pixel positions without requiring a complete redesign of the entire sensor system.
Solution Approach 2:
The patent implements dynamics by making light guide properties variable rather than uniform across the sensor array. The light guide structures are designed with position-dependent characteristics, where parameters such as geometry, material composition, or orientation are dynamically adjusted based on the pixel's distance from the sensor center. This dynamic adaptation allows the system to maintain optimal performance across varying light incidence angles while using a single integrated sensor design.
2Productivity
If light guide structures are added to improve light channeling, then light gathering efficiency improves, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent applies segmentation by dividing the light guide structure into multiple functional layers or components, each performing a specific function in the light channeling process. This segmentation allows for independent optimization of each layer's properties and simplifies the fabrication process, as each segment can be manufactured and characterized separately before integration. The modular approach reduces overall device complexity while maintaining high light gathering efficiency.
Solution Approach 2:
The patent introduces intermediary structures between the incoming light and the photosensitive elements, such as intermediate optical layers or transition regions that facilitate efficient light coupling. These intermediary components act as mediators that bridge the gap between the external light environment and the internal sensor structures, improving light gathering efficiency without requiring direct modification of the core photosensitive elements, thereby limiting the increase in overall device complexity.
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 enhances light gathering efficiency and reduces cross-talk, resulting in improved image quality by ensuring that light is effectively directed to the photosensitive elements, even for pixels receiving light at oblique angles, thereby increasing quantum efficiency and image sensor performance.
Implementation Method 1
These openings are then filled with material having an elevated index of refraction. Light guide structures that are formed in this way help to channel incoming light to the photosensitive elements of the pixels.
Implementation Method 2
A typical image sensor has an array of pixels each of which has a photosensitive element such as a photodiode.
Data Source
AI summary
An image sensor may be formed from a planar semiconductor substrate. The image sensor may have an array of pixels. Each pixel may have a photosensitive element that is formed in the substrate and may have a light guide in a dielectric stack that guides light from a microlens and color filter to the photosensitive element. The light guides in pixels that are offset from the center of the image sensor may be tilted so that their longitudinal axes each form a non-zero angle with a vertical axis that lies perpendicular to the planar semiconductor substrate. These light guides may have laterally elongated openings that help collect light. A light guide may have a lower opening that matches the size of an associated photosensitive element. Photosensitive elements that are laterally offset from the center of the image sensor may be tilted. Pixels of different colors may have off-center photosensitive elements.