Solid-State Imaging Device kTC Noise Reduction via Feedback Reset
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Layered sensors for solid-state imaging devices face issues with kTC noise due to the conductive line or contact between the photoelectric conversion unit and the floating diffusion, leading to noise superimposed on image signals, which is not fully mitigated by existing solutions.
Innovation Solution
A solid-state imaging device configuration where pixels share common circuits, including pixel and column common circuits, with a feedback path for signal detection and reset, allowing for reduced kTC noise without increasing interference between pixels, and featuring independent detection and storage capacitance to enhance signal saturation and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photodiode depth is increased to improve sensitivity, then light absorption efficiency improves, but aspect ratio increases making manufacturing difficult
Solution Approach 1:
The patent transitions from planar photodiodes to vertically stacked three-dimensional photodiodes, enabling increased light absorption path length without increasing lateral pixel dimensions. This vertical stacking allows deeper penetration into the silicon substrate while maintaining manufacturable aspect ratios through advanced fabrication processes.
Solution Approach 2:
The patent employs composite material structures including stacked photodiode layers with different doping types (n-type and p-type) and varying depths, allowing each layer to optimize light absorption at different wavelengths while collectively achieving high overall sensitivity without requiring excessive individual layer depths.
2Measurement precision
If photodiode area is increased to improve light concentration, then quantum efficiency improves, but pixel area consumption increases reducing aperture ratio
Solution Approach 1:
The patent utilizes the vertical dimension by stacking multiple thin photodiode layers (e.g., 1-3 μm each) to achieve equivalent total absorption path length to much thicker single-layer photodiodes. This allows maintaining small lateral photodiode footprints while achieving high quantum efficiency through cumulative vertical absorption.
Solution Approach 2:
The patent divides a single thick photodiode into multiple thinner stacked photodiode layers, each optimized for specific wavelength ranges. This segmentation allows more efficient light absorption across the spectrum while reducing the lateral area required per photodiode, as each layer can be shallower and more tightly packed.
3Measurement precision
If microlens is added to concentrate light on photodiode, then light concentration efficiency improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent integrates the light-concentrating function directly into the stacked photodiode structure itself through optimized layer stacking and material composition, eliminating the need for separate microlens components. The vertical stack geometry naturally focuses incident light onto the active regions of each layer.
Solution Approach 2:
The stacked photodiode structure is designed to self-focus and absorb light efficiently through its inherent vertical geometry and material properties, without requiring additional external optical elements like microlenses. The structure serves its own light-concentration function through proper architectural design.
4Quantity of substance
If storage capacitance is increased to improve dynamic range, then saturation electron capacity improves, but pixel area consumption increases
Solution Approach 1:
The patent implements storage capacitance functions using vertical stacking of capacitive structures (such as stacked capacitors with upper and lower electrodes separated by dielectric layers) within the pixel column, enabling large capacitance values without increasing lateral pixel area. The vertical dimension provides additional space for capacitance accumulation.
Solution Approach 2:
The patent nests storage capacitance structures within the vertical pixel column, placing capacitive elements (such as diffusion regions and oxide layers) inside or adjacent to the stacked photodiode structure. This nested arrangement allows storage capacitance to share space with photoelectric conversion elements, avoiding additional area consumption.
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 saturation number of electrons and reduces kTC noise, improving image quality by minimizing interference and noise superimposition, while allowing for flexible design and increased signal detection.
Implementation Method 1
photoelectric conversion film, converting incident light into electric charges
Implementation Method 2
when 2 μm of green light having a wavelength of 550 nm is incident on silicon, only about 92% is absorbed
Data Source
AI summary
A solid-state imaging device includes: pixels arrayed two-dimensionally; pixel common circuits arrayed in a matrix, each shared by adjacent pixels of a certain number among the pixels; column common circuits, each provided for one of columns of the pixel common circuits, and shared by pixel common circuits belonging to a same column; column signal lines each provided for one of the columns of the pixel common circuits; and reset signal lines each provided for one of the columns of the pixel common circuits, in which an electric signal from each of the pixels is detected by a corresponding one of the pixel common circuits and read by a corresponding one of the column common circuits, and the electric signal detected by the corresponding one of the pixel common circuits is reset by a feedback path including one column signal line, one column common circuit, and one reset signal lines.