Back Side Illuminated Semiconductor Capacitor Floating Diffusion Node
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Solution Overview
Problem
In back side illuminated semiconductor structures, the floating diffusion node is affected by incident light, leading to degraded signal-to-noise ratio due to photoelectric effects, and reducing its size to minimize this effect also decreases equivalent capacitance, compromising performance.
Innovation Solution
A semiconductor capacitor is connected to and formed above the floating diffusion node, with a metal-insulator-metal (MIM) capacitor configuration, reducing the node's size while maintaining capacitance and incorporating a light reflection layer to enhance light absorption efficiency by reflecting unabsorbed light back to the sensing region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the dimension of the floating diffusion node is reduced to minimize incident light reception, then the photoelectric effect in the floating diffusion node is reduced, but the equivalent capacitance of the floating diffusion node is decreased
Solution Approach 1:
The patent divides the capacitance function into two parts: the floating diffusion node maintains a small size to minimize light reception, while a separate semiconductor capacitor is introduced to provide the required equivalent capacitance. This segmentation allows each component to be optimized independently - the floating diffusion node for minimal light exposure and the semiconductor capacitor for sufficient charge storage capacity.
Solution Approach 2:
The semiconductor capacitor acts as an intermediary element that couples to the floating diffusion node via a contact structure. This intermediary provides the necessary capacitance without requiring the floating diffusion node itself to be large, thereby resolving the contradiction between minimizing light exposure and maintaining sufficient capacitance.
2Object-affected harmful factors
If the dimension of the floating diffusion node is reduced to avoid too much incident light, then the influence of incident light on the floating diffusion node is reduced, but the signal-to-noise ratio is degraded
Solution Approach 1:
By segmenting the capacitance function between the floating diffusion node and the semiconductor capacitor, the floating diffusion node can be kept small to minimize light-induced noise, while the semiconductor capacitor maintains the equivalent capacitance needed for proper signal-to-noise ratio performance.
Solution Approach 2:
The capacitance function is extracted from the floating diffusion node and placed into a separate semiconductor capacitor. This extraction allows the floating diffusion node to be minimized for reduced light exposure while the capacitance is provided by the separate capacitor structure.
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 minimizes the impact of incident light on the floating diffusion node, maintains required capacitance, and improves signal-to-noise ratio and light absorption efficiency, suitable for various electronic shutters.
Implementation Method 1
The light sensing region is inside the substrate and configured to receive light penetrating the substrate from the light receiving surface to generate photo-generated charges by a photoelectric effect
Implementation Method 2
The metal electrode is used to reflect light not being absorbed by a light sensing device in the first penetration back to the light sensing device so as to improve the light absorption efficiency
Data Source
AI summary
There is provided a back side illuminated semiconductor structure with a semiconductor capacitor connected to a floating diffusion node in which the semiconductor capacitor for reducing a dimension of the floating diffusion node is provided above the floating diffusion node so as to eliminate the influence thereto by incident light and enhance the light absorption efficiency.