Light Detection Pixel With 3D MIM Capacitor for Wider Dynamic Range
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Solution Overview
Problem
The saturation signal amount of pixels in imaging devices with ADCs provided for each pixel is reduced, limiting the high dynamic range of the imaging device.
Innovation Solution
Incorporating a metal insulator metal (MIM) capacitor or a metal oxide semiconductor (MOS) capacitor with a three-dimensional structure in the second accumulation section to increase capacitance, allowing for higher charge accumulation and improved conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an ADC is provided for each pixel to improve signal conversion precision, then measurement precision is improved, but the saturation signal amount of the pixel is reduced
Solution Approach 1:
The accumulation section is divided into two separate sections: a first accumulation section connected to the photoelectric conversion section and a second accumulation section connected to the ADC. This segmentation allows the first accumulation section to handle signal accumulation for precision conversion while the second accumulation section handles saturation charge, thereby resolving the contradiction between maintaining measurement precision and preserving saturation signal amount.
2Adaptability or versatility
If the saturation signal amount is increased to expand dynamic range, then the dynamic range is improved, but the conversion efficiency at high illuminance deteriorates
Solution Approach 1:
A conversion efficiency switching transistor is introduced to dynamically switch between different accumulation modes. When saturation charge needs to be handled, the transistor transfers charge to the second accumulation section, adjusting the conversion efficiency adaptively. This dynamic switching mechanism allows the system to maintain high conversion efficiency under normal conditions while expanding dynamic range when needed.
Solution Approach 2:
The system changes the accumulation capacity parameter by switching between two accumulation sections with different capacitances. The first accumulation section has lower capacitance for high conversion efficiency, while the second accumulation section has higher capacitance for expanded dynamic range. This parameter change is controlled by the conversion efficiency switching transistor based on illumination conditions.
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
Enhances the saturation signal amount of the pixel, reducing conversion efficiency at high illuminance and expanding the dynamic range of the imaging device.
Implementation Method 1
a photoelectric conversion section that is provided in a semiconductor substrate and generates a charge corresponding to incident light
Implementation Method 2
the second accumulation section includes a metal insulator metal (MIM) capacitor having a three-dimensional structure or a metal oxide semiconductor (MOS) capacitor
Data Source
AI summary
A light detection element including: a photoelectric conversion section that is in a semiconductor substrate and generates a charge corresponding to incident light; a first accumulation section that accumulates the generate charge; an amplification transistor that generates an input signal corresponding to an amount of the accumulated charge; a second accumulation section to which a saturated charge is transferred from the photoelectric conversion section via the first accumulation section; a conversion efficiency switching transistor that transfers the saturated charge to the second accumulation section to switch a conversion efficiency; a reset transistor that resets the charge accumulated in the first accumulation section and the saturated charge accumulated in the second accumulation section; and a differential input circuit that compares the input signal generated by the amplification transistor with a reference signal and outputs a comparison result, in which the second accumulation section includes a MIM capacitor having a three-dimensional structure.