Backside Illuminated Image Sensor Crosstalk Reduction
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Solution Overview
Problem
MOS image sensors face sensitivity degradation due to light reflection and absorption by metallic wire layers, leading to crosstalk between pixels, which is not effectively addressed by existing technologies.
Innovation Solution
The design and fabrication of an image sensor with a substrate having a pixel region and a non-pixel region, featuring a base well with higher doping concentration than the first wells, allowing for stable well-bias sharing among first wells through the base well, thereby maintaining electric potential and reducing crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If metallic wire layers are used for interconnects, then device complexity is reduced and manufacturing is simplified, but light reflection and absorption occur causing sensitivity degradation and crosstalk
Solution Approach 1:
The patent removes metallic wire layers from the front side of the substrate where light is incident. Instead, interconnect structures are formed only on the back side of the substrate, extracting the harmful metallic layers from the light path while maintaining electrical connectivity functions through alternative routing
Solution Approach 2:
The patent inverts the conventional interconnect structure arrangement by placing all metallic interconnect layers on the back side of the substrate rather than the front side. This inversion allows light to incident on the front side without encountering metallic reflections or absorptions, while electrical connections are established through the inverted interconnect architecture
2Manufacturing precision
If back side illuminated structure is used to eliminate metallic wire layer interference, then sensitivity is improved, but electric potential of wells becomes unstable causing crosstalk
Solution Approach 1:
The patent introduces a base well as an intermediary structure between the first wells and the back side of the substrate. This base well acts as a mediator that provides a stable reference potential, enabling the first wells to share a common well-bias through the base well, thereby stabilizing electric potentials while maintaining the back side illuminated structure
Solution Approach 2:
The patent modifies the doping concentration parameter by creating a base well with higher doping concentration than the first wells. This parameter change in doping concentration enables the base well to function as an effective potential reference, stabilizing the electric potentials of the first wells through the doping concentration difference
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 stabilizes the electric potential of the wells, enhancing sensitivity and reducing crosstalk between pixels, improving the overall performance of the image sensor.
Implementation Method 1
a base well in the non-pixel region and between the at least one first well and a second side of the substrate
Implementation Method 2
a base well in the non-pixel region and having a higher doping concentration than a doping concentration of the plurality of first wells
Data Source
AI summary
An image sensor and a method of fabricating the same are provided. The image sensor includes a substrate having a pixel region including a plurality of unit pixels and a non-pixel region, at least one first well in the non-pixel region, an interconnect structure on a first side of the substrate, and a base well in the non-pixel region and between the first well and a second side of the substrate.