Dual-Pixel Image Sensor Layout for Quantum Efficiency and Dynamic Range
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Solution Overview
Problem
BSI image sensor devices face challenges in detecting low irradiance targets under strong background irradiance due to insufficient quantum efficiency and dynamic range, leading to saturation issues.
Innovation Solution
The image sensor is configured with two groups of pixels: one group has high quantum efficiency to improve signal-to-noise ratio, and the other group has a blocking metal layer to reduce incident light intensity, thereby extending exposure time and enhancing saturation levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the image sensor uses a standard pixel configuration, then the device complexity is low, but the quantum efficiency and dynamic range are insufficient for detecting low irradiance targets under strong background irradiance
Solution Approach 1:
The pixel array is segmented into two distinct groups: first pixels with high quantum efficiency for detecting low irradiance targets, and second pixels with extended dynamic range for handling strong background irradiance. This segmentation allows each group to be optimized for specific detection conditions, resolving the contradiction between detection capability and device complexity.
Solution Approach 2:
Different pixel structures are assigned to different regions of the pixel array based on local detection requirements. First pixels use a structure optimized for high quantum efficiency (with microlens and charge storage region) while second pixels use a structure optimized for extended dynamic range (with additional light-blocking structure). This local differentiation enables each region to perform its specific function effectively.
2Measurement precision
If the image sensor increases quantum efficiency to improve signal-to-noise ratio, then low irradiance detection is enhanced, but saturation occurs under strong background irradiance
Solution Approach 1:
The pixel array is divided into two groups with different structural characteristics. First pixels are designed with high quantum efficiency to maximize signal-to-noise ratio for low irradiance detection, while second pixels incorporate additional light-blocking structures to prevent saturation under strong background irradiance. This segmentation allows each group to handle different irradiance conditions optimally.
Solution Approach 2:
Different structural qualities are applied to different pixel groups based on their functional requirements. First pixels have a structure that maximizes light capture and charge collection for high signal-to-noise ratio, while second pixels have a modified structure with light-blocking elements that reduce saturation effects under strong illumination. This local quality differentiation resolves the contradiction between sensitivity and saturation resistance.
3Adaptability or versatility
If the image sensor extends dynamic range to handle strong background irradiance, then saturation is reduced, but quantum efficiency for low irradiance detection decreases
Solution Approach 1:
The pixel array is segmented into two groups: first pixels optimized for high quantum efficiency to maintain reliable detection of low irradiance targets, and second pixels optimized for extended dynamic range to handle strong background irradiance without saturation. This segmentation allows the system to achieve both high quantum efficiency and extended dynamic range simultaneously by assigning different optimization goals to different regions.
Solution Approach 2:
The image sensor achieves multi-functionality by incorporating two types of pixels that can operate simultaneously or selectively depending on imaging conditions. The first pixels provide high quantum efficiency for low-light conditions, while second pixels provide extended dynamic range for high-light conditions. This universal design allows the sensor to adapt to various irradiance conditions without compromising either quantum efficiency or dynamic range.
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 configuration improves the image sensor's quantum efficiency and dynamic range, enabling effective detection of low irradiance targets even under high background irradiance conditions.
Implementation Method 1
These image sensors utilize an array of pixels that absorb (e.g., sense) the incoming radiation and convert it into electrical signals
Implementation Method 2
depositing a metal layer with a groove structure over the radiation sensing region
Data Source
AI summary
The present disclosure describes an image sensor device and a method for forming the same. The image sensor device can include a semiconductor layer. The semiconductor layer can include a first surface and a second surface. The image sensor device can further include an interconnect structure formed over the first surface of the semiconductor layer, first and second radiation sensing regions formed in the second surface of the semiconductor layer, a metal stack formed over the second radiation sensing region, and a passivation layer formed through the metal stack and over a top surface of the first radiation sensing region. The metal stack can be between the passivation layer and an other top surface of the second radiation sensing region.