Global Shutter Pixel Wiring Capacitance for Lower kTC Noise
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Solution Overview
Problem
Existing solid-state imaging elements face challenges in increasing the capacitance of the charge holding unit, which is necessary to reduce kTC noise, but existing configurations do not provide specific methods for achieving this.
Innovation Solution
The proposed solution involves a solid-state imaging element with a charge holding unit connected in parallel to the floating diffusion, where the charge holding unit is formed by the wiring capacitance created by running first and second wirings connected to different potentials in parallel, increasing the capacitance and reducing kTC noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the capacitance of the charge holding unit is increased to reduce kTC noise, then the noise reduction effect is improved, but the device structure becomes more complex and occupies more area
Solution Approach 1:
The patent introduces a wiring capacitance as an intermediary element to increase the charge holding unit capacitance. By forming wiring capacitance through parallel running wirings (first wiring connected to first potential and second wiring connected to second potential), the effective capacitance is increased without requiring additional dedicated capacitor structures, thus reducing the area occupation while achieving noise reduction
Solution Approach 2:
The patent makes the wiring structure serve multiple functions: it acts as both the electrical connection pathway and the charge storage element. The parallel running wirings that are necessary for the circuit operation simultaneously create wiring capacitance that functions as the charge holding unit, eliminating the need for separate capacitor structures and reducing overall device area
2Object-affected harmful factors
If the capacitance of the charge holding unit is increased to reduce kTC noise, then the noise reduction effect is improved, but the device structure becomes more complex
Solution Approach 1:
The patent uses wiring capacitance as an intermediary solution that leverages existing circuit elements (parallel running wirings) to provide the needed capacitance. This approach avoids introducing complex additional structures while achieving the desired noise reduction through the natural capacitance formed by the wiring arrangement
Solution Approach 2:
The patent enables the wiring structure to serve itself by making the parallel running wirings (which are already necessary for circuit operation) simultaneously provide the charge holding function. The wiring capacitance is generated automatically by the wiring arrangement itself, eliminating the need for separate capacitor components and simplifying the overall device 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 effectively increases the capacitance of the charge holding unit, thereby reducing kTC noise and improving the image quality by enhancing the capacitance distribution between the charge holding unit and the floating diffusion.
Implementation Method 1
the charge holding unit includes a wiring capacitance formed by parallel running of a first wiring connected to a first potential and a second wiring connected to a second potential different from the first potential
Data Source
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AI summary
The present disclosure relates to a solid-state imaging element and an electronic device capable of increasing the capacitance of a charge holding unit. The solid-state imaging element includes a pixel including a photodiode, an FD that accumulates charges generated in the photodiode, and a charge holding unit that is connected in parallel with the FD. The charge holding unit includes a wiring capacitance formed by parallel running of a first wiring connected to a first potential and a second wiring connected to a second potential different from the first potential. The present disclosure can be applied to a solid-state imaging element that performs global shutter type imaging.