Solid-State Imaging Device Pixel Sensitivity Uniformity
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Solution Overview
Problem
Solid-state imaging devices face challenges due to varying optical absorption coefficients for different wavelengths of light, leading to unequal sensitivities among pixels, which affects image quality and signal-to-noise ratio (S/N ratio).
Innovation Solution
The device incorporates a semiconductor structure with p-type semiconductor regions and detectors of varying thicknesses and impurity concentrations, optimized for each color channel, along with a potential distribution that adjusts based on incident light wavelength to enhance absorption and reduce sensitivity differences between pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pixels are arranged in a semiconductor to detect different light colors, then the device can capture multiple color channels, but the different optical absorption coefficients for different wavelengths cause unequal sensitivities among pixels
Solution Approach 1:
The patent applies local quality by creating different impurity concentration profiles in different regions of the semiconductor layer. Specifically, the first impurity concentration in the first region is set differently from the second impurity concentration in the second region, allowing each region to be optimized for detecting specific wavelengths of light. This resolves the contradiction by making each pixel's sensitivity profile locally adapted to its intended detection function while maintaining overall uniformity across the array.
Solution Approach 2:
The patent changes physical parameters (impurity concentrations, layer thicknesses) to optimize light absorption characteristics. By adjusting the impurity concentrations in different semiconductor regions and varying the thickness of the semiconductor layer, the patent tailors the optical absorption properties for different wavelength ranges, thereby achieving uniform photosensitivity across pixels detecting different colors.
2Measurement precision
If the semiconductor layer thickness is increased to improve light absorption, then sensitivity improves, but dark current increases
Solution Approach 1:
The patent optimizes the thickness parameter of the semiconductor layer to achieve the desired balance. By carefully controlling the thickness to be between 5 μm and 15 μm, the patent ensures sufficient light absorption while limiting the generation and propagation of dark current. This parameter optimization resolves the contradiction between sensitivity and dark current.
Solution Approach 2:
The patent introduces an intermediary mechanism through the specific impurity concentration profile and potential distribution control. The controlled impurity concentrations act as intermediaries that facilitate charge carrier separation and collection, improving light sensitivity without proportionally increasing dark current. This intermediary mechanism decouples the direct relationship between thickness and dark current.
3Productivity
If impurity concentrations are increased to improve charge carrier generation, then detection efficiency improves, but noise increases
Solution Approach 1:
The patent applies local quality by setting different impurity concentrations in different regions. The first impurity concentration in the first region and the second impurity concentration in the second region are optimized independently based on the specific detection requirements of each region. This localized optimization allows high charge carrier generation efficiency where needed while controlling noise in other regions.
Solution Approach 2:
The patent changes the impurity concentration parameter within specific ranges (first concentration: 1×10^16 to 1×10^18 atoms/cm³, second concentration: 1×10^16 to 1×10^18 atoms/cm³) to optimize the balance between charge carrier generation and noise. By controlling impurity concentrations rather than simply increasing them, the patent achieves high detection efficiency while minimizing noise generation.
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 suppresses differences in photosensitivity among pixels, improving overall sensitivity and signal-to-noise ratio by optimizing light absorption and reducing dark current.
Implementation Method 1
the semiconductor has different optical absorption coefficients for the lights of different wavelengths, respectively
Implementation Method 2
each pixel is configured to detect, for example, one of red, green, and blue lights
Data Source
AI summary
A solid-state imaging device includes a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type on the first semiconductor layer; and first and second detectors positioned inside the second semiconductor layer. The first and second detectors are arranged in a first direction along a boundary between the first semiconductor layer and the second semiconductor layer. The device further includes first and second semiconductor regions provided between the first semiconductor layer and the first and second detectors, respectively. The first and second semiconductor regions include second conductivity type impurities with a higher concentration than that in the second semiconductor layer. The first detector has a first thickness along a second direction from the first semiconductor layer toward the second semiconductor layer, and the second detector has a second thickness along the second direction, the second thickness being thicker than the first thickness.