Hexagonal Image Sensor Microlens Offset for Stress Reduction
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Solution Overview
Problem
Conventional image sensors face challenges in optimizing the arrangement of photoelectric conversion regions and microlenses to enhance light-focusing performance and photo sensing efficiency, while also minimizing stress concentrations that can lead to damage.
Innovation Solution
The image sensor design features a semiconductor substrate with a hexagonal array of photoelectric conversion regions and corresponding microlenses, where the centers of the microlenses and photoelectric conversion regions are aligned or offset to prevent overlap, and includes a conductive buried layer for light reflection and stress dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the centers of microlenses and photoelectric conversion regions are aligned to maximize light-focusing performance, then photo sensing efficiency is improved, but stress concentrations occur leading to cracks and device damage
Solution Approach 1:
The patent intentionally offsets the center of each microlens from the center of its corresponding photoelectric conversion region by a predetermined distance (e.g., 0.5-2 micrometers). This asymmetric arrangement prevents the focal point of light from concentrating directly on the photoelectric conversion region, thereby reducing stress concentration and preventing cracks while maintaining adequate light-focusing performance.
2Ease of manufacture
If a conventional planar array of photoelectric conversion regions is used, then manufacturing is simplified, but light-focusing performance and photo sensing efficiency are suboptimal
Solution Approach 1:
The patent employs a hexagonal array configuration for photoelectric conversion regions instead of a conventional square planar array. This hexagonal arrangement optimizes the spatial distribution of regions, improving light-focusing performance and photo sensing efficiency while maintaining compatibility with standard semiconductor manufacturing processes.
Solution Approach 2:
The patent transitions from a two-dimensional square grid arrangement to a hexagonal tiling arrangement, effectively changing the geometric dimensioning approach. This dimensional reconfiguration optimizes packing density and light distribution patterns, enhancing photo sensing efficiency without complicating the manufacturing process.
3Productivity
If microlenses are positioned to maximize light collection, then photo sensing efficiency improves, but stress concentrations lead to device damage
Solution Approach 1:
The patent deliberately positions microlens centers offset from photoelectric conversion region centers, creating an asymmetric configuration that distributes mechanical stress more evenly across the device structure. This prevents stress concentration at focal points while maintaining sufficient light collection efficiency for effective photo sensing.
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 light-focusing performance, increases photo sensing efficiency, and enhances the reliability of the image sensor by minimizing stress concentrations and preventing damage from cracks and electrostatic discharge.
Implementation Method 1
a plurality of microlenses respectively corresponding to the plurality of photoelectric conversion regions, and forming a second hexagonal array on the plane that is parallel to the first surface of the semiconductor substrate
Implementation Method 2
an isolation region comprising an insulating liner and a conductive buried layer, wherein the insulating liner covers an inner wall of an isolation trench that penetrates the semiconductor substrate, and the conductive buried layer is disposed on the insulating liner in the isolation trench
Data Source
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AI summary
An image sensor including: a semiconductor substrate having a first region and a second region; an isolation region filling an isolation trench that partially penetrates the semiconductor substrate; a plurality of photoelectric conversion regions defined by the isolation region and forming a first hexagonal array on a plane that is parallel to a surface of the semiconductor substrate; and a plurality of microlenses respectively corresponding to the plurality of photoelectric conversion regions, and forming a second hexagonal array on the plane that is parallel to the surface of the semiconductor substrate.