Solid-State Imaging Device Hybrid Photoelectric Conversion Architecture
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Solution Overview
Problem
Existing solid-state imaging devices with mosaic color filters have low light utilization efficiency, sensitivity, and resolution, and suffer from visible false colors due to the complexity and high manufacturing costs of stacking multiple photoelectric conversion layers, as well as inadequate spectral sensitivity separation and color reproducibility.
Innovation Solution
A hybrid-type solid-state imaging device with intra-substrate and on-substrate photoelectric conversion portions, using n-channel MOS transistors for signal read circuits, where positive holes are stored and read for green light, and electrons for blue and red light, with a protection circuit to manage voltage and prevent transistor breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three layers of photoelectric conversion film are stacked on a semiconductor substrate to improve light utilization efficiency and sensitivity, then light utilization efficiency and sensitivity are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent transitions from planar mosaic color filter arrangement to a three-dimensional stacked photoelectric conversion structure. Multiple photoelectric conversion layers (first, second, and third layers with different spectral sensitivities) are stacked vertically on the semiconductor substrate, enabling simultaneous detection of multiple color signals at each pixel location. This dimensional change from 2D to 3D architecture resolves the contradiction by improving sensitivity through increased light absorption while maintaining manageable device complexity through systematic layer design.
Solution Approach 2:
The photoelectric conversion function is segmented into multiple independent layers, each with distinct spectral sensitivity characteristics. The first photoelectric conversion layer detects blue light, the second layer detects green light, and the third layer detects red light. Each layer can be independently optimized and connected to dedicated signal read circuits, allowing parallel processing of color signals. This segmentation resolves the contradiction by improving overall sensitivity through cumulative light absorption while maintaining device complexity at acceptable levels through modular architecture.
2Measurement precision
If three layers of photoelectric conversion film are stacked to improve color signal detection, then color signal detection capability is improved, but manufacturing yield decreases and manufacturing cost increases
Solution Approach 1:
The patent employs a unified semiconductor substrate that serves multiple functions: it supports the stacked photoelectric conversion layers, provides signal read circuits for each layer, and enables simultaneous detection of blue, green, and red light signals. The substrate and associated circuitry are designed to handle all three color channels, eliminating the need for separate processing lines for each layer. This multi-functionality resolves the contradiction by improving color signal detection precision while maintaining manufacturing yield through integrated processing.
Solution Approach 2:
The patent merges the fabrication processes for multiple photoelectric conversion layers into a single integrated manufacturing flow. All three photoelectric conversion layers are formed on the same substrate using compatible materials and processes, allowing simultaneous or sequential fabrication without requiring separate manufacturing lines. The signal read circuits for all layers are also integrated onto the same substrate. This merging of processes resolves the contradiction by improving color detection capability while maintaining high manufacturing yield through unified production.
3Measurement precision
If photodiodes are positioned at different depths in silicon substrate to detect different wavelengths, then spectral sensitivity is improved, but separation of spectral sensitivity characteristics becomes insufficient
Solution Approach 1:
The patent applies local quality by assigning different spectral sensitivity characteristics to different photoelectric conversion layers. The first layer is optimized for blue light detection, the second layer for green light, and the third layer for red light detection. Each layer has tailored spectral response characteristics that are locally optimized for its specific wavelength range. This local quality approach resolves the contradiction by improving overall spectral sensitivity while achieving adequate separation of spectral characteristics through specialized layer design rather than relying solely on depth-based differentiation.
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 sensitivity and color reproducibility by optimizing the transfer and storage of electric charges, reducing the probability of charge annihilation and trapping, and improving spectral sensitivity characteristics, especially for green light, while maintaining high sensitivity for blue and red light.
Implementation Method 1
photoelectric conversion film layers respectively adapted to generate signal charges (electrons or positive holes) in response to blue (B) light, green (G) light, and red (R) light
Data Source
AI summary
A solid-state imaging device comprises pixels including: a light receiving portion comprising intra-substrate photoelectric conversion portions, formed in a silicon substrate, that detect light rays of different color, an on-substrate photoelectric conversion portion, stacked above the intra-substrate photoelectric conversion portions, that detects light rays of a color differing from the colors detected by the intra-substrate photoelectric conversion portions; first and second signal read circuits that read signals corresponding to electric charges in the intra-substrate photoelectric conversion portions and signals corresponding to electric charges in the on-substrate photoelectric conversion portion, respectively. The electric charges in the intra-substrate photoelectric conversion portions are electrons, and the electric charges in the on-substrate photoelectric conversion portions are positive holes. Each of the first and second signal read circuits comprises an output transistor, a reset transistor and a selection transistor which are n-channel MOS transistors. The drain voltage of the reset transistor of the second signal read circuit is set to be lower than that of the reset transistor of the first signal read circuit.