Back-Illuminated Image Sensor Opaque Isolation Structure
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Solution Overview
Problem
Image sensors, particularly back-side illuminated CMOS and CCD sensors, suffer from optical cross-talk and performance degradation due to light exposure in peripheral regions, leading to noise generation and reduced performance.
Innovation Solution
A method of fabricating image sensors involving a device substrate with radiation-sensing regions separated by an isolation structure, a transparent layer formed over the back side, and opaque features aligned with the radiation-sensing regions to reduce optical cross-talk, where the opaque features are co-planar with the transparent features and adjacent to them, effectively blocking unwanted light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a back side illuminated image sensor is used to improve light sensitivity, then radiation sensing capability is improved, but optical cross-talk between pixels increases and peripheral regions cannot be kept optically dark
Solution Approach 1:
The patent divides the image sensor into distinct regions: a pixel region with radiation-sensing regions and a periphery region with non-radiation-sensing devices. Isolation structures are formed between adjacent radiation-sensing regions to segment light paths, preventing optical cross-talk while maintaining the back-illuminated architecture's light sensitivity advantages.
Solution Approach 2:
The patent introduces an opaque layer as an intermediary element between the pixel region and periphery region. This opaque layer blocks stray light from reaching peripheral devices, acting as a mediator that prevents harmful optical interactions while allowing the back-illuminated structure to maintain its radiation sensing capability.
2Adaptability or versatility
If peripheral devices are placed in the image sensor to increase functionality, then device versatility is improved, but these devices generate noise when exposed to light
Solution Approach 1:
The patent spatially segments the image sensor into a pixel region and a periphery region, with the opaque layer creating an optical boundary. This segmentation allows peripheral devices to be included for enhanced functionality while preventing them from being exposed to incident light, thereby eliminating noise generation.
Solution Approach 2:
The patent converts the potential harm of light exposure to peripheral devices into a benefit by strategically placing an opaque layer that blocks light from reaching these devices. This allows the peripheral devices to be present for functional purposes without suffering from light-induced noise, effectively turning the design challenge into an opportunity for optimized layout.
3Object-generated harmful factors
If isolation structures are added between radiation-sensing regions to reduce optical cross-talk, then optical performance is improved, but device complexity increases
Solution Approach 1:
The patent merges the isolation structures with the opaque layer, combining multiple functions into a single integrated element. The opaque layer simultaneously serves as a light-blocking barrier for peripheral devices and as an isolation structure between radiation-sensing regions, reducing overall device complexity while maintaining optical performance.
Solution Approach 2:
The opaque layer is designed to perform multiple functions: it blocks stray light from peripheral devices, isolates adjacent radiation-sensing regions to prevent optical cross-talk, and maintains structural integrity of the back-illuminated sensor. This multi-functionality reduces the need for separate components, simplifying the overall device architecture.
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
The solution significantly reduces optical cross-talk and enhances the performance of image sensors by ensuring that peripheral regions remain optically dark, thereby minimizing noise and improving overall image quality.
Implementation Method 1
filling the opening with an opaque material
Implementation Method 2
forming a transparent layer over the back side of the device substrate
Data Source
AI summary
Provided is a method of fabricating an image sensor device. The method includes providing a device substrate having a front side and a back side. The method includes forming first and second radiation-sensing regions in the device substrate, the first and second radiation-sensing regions being separated by an isolation structure. The method also includes forming a transparent layer over the back side of the device substrate. The method further includes forming an opening in the transparent layer, the opening being aligned with the isolation structure. The method also includes filling the opening with an opaque material.