Solid-State Imaging Device Light Reflection Wiring
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Solution Overview
Problem
Conventional solid-state imaging devices using CCD sensors require multiple voltage sources and power circuits, limiting miniaturization and increasing power consumption, while MOS sensors with amplifier transistors face sensitivity variations across unit cells due to uneven light incidence, resulting in brightness inconsistencies in captured images.
Innovation Solution
A solid-state imaging device with a semiconductor substrate, a photodiode, and a diffusion layer, where a gate wiring layer and an adjacent wiring layer are strategically positioned to equalize light incidence, ensuring consistent sensitivity across unit cells by reflecting light from oblique directions onto the photodiode, and sharing transistors to maintain uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a CCD sensor is used, then the device can capture images, but multiple voltage sources and power circuits are required, limiting miniaturization and increasing power consumption
Solution Approach 1:
The invention extracts and eliminates the need for multiple voltage sources and power circuits by transitioning from CCD to MOS sensor technology. The MOS sensor structure removes the complex voltage generation requirements while maintaining image capture functionality, directly addressing the contradiction between reliability and device complexity.
Solution Approach 2:
The invention replaces the CCD sensor system with a MOS sensor system, substituting one technological approach with another that inherently requires fewer power circuits. This substitution resolves the technical contradiction by maintaining imaging capability while reducing structural complexity.
2Use of energy by stationary object
If a MOS sensor with amplifier transistors is used, then power consumption and voltage can be lowered, but sensitivity variations occur across unit cells due to uneven light incidence
Solution Approach 1:
The invention applies asymmetry by strategically positioning the gate wiring layer and diffusion layer at specific distances from the photodiode. This asymmetric arrangement creates uniform light path lengths and reflection characteristics across all unit cells, ensuring consistent sensitivity while maintaining the low power consumption benefits of MOS sensor technology.
Solution Approach 2:
The invention implements local quality by optimizing the specific distances between the photodiode, gate wiring layer, and diffusion layer in each unit cell. By carefully controlling these local geometric parameters, the invention ensures uniform light incidence characteristics across all pixels, resolving the sensitivity uniformity issue while preserving the energy efficiency of MOS sensors.
3Area of stationary object
If the gate wiring layer is positioned close to the photodiode, then device area is reduced, but light from oblique directions may not be properly reflected onto the photodiode
Solution Approach 1:
The invention resolves the contradiction by operating in multiple dimensions: it optimizes both the vertical distance between layers and the horizontal positioning of the gate wiring layer relative to the photodiode. This multi-dimensional optimization ensures proper light reflection from oblique directions while maintaining compact device area.
Solution Approach 2:
The invention applies parameter changes by precisely controlling the distance between the gate wiring layer and photodiode, and the distance between the diffusion layer and photodiode. By optimizing these geometric parameters, the invention achieves both compact area and efficient light reflection, resolving the technical contradiction.
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
The solution achieves consistent sensitivity across unit cells, reducing brightness variations in images and enabling effective shading compensation, while maintaining a single power source and reducing power consumption, thus enhancing image quality and device miniaturization.
Implementation Method 1
reflecting light from oblique directions onto the photodiode
Implementation Method 2
a photodiode provided in the semiconductor substrate
Data Source
AI summary
A solid-state imaging device has a photodiode provided in a semiconductor substrate of a first conductivity type. A diffusion layer of a second conductivity type is provided in the semiconductor substrate. A gate wiring layer is provided on the semiconductor substrate between the photodiode and the diffusion layer. A gate insulating film is interposed between the semiconductor substrate and the gate wiring layer. A wiring layer is provided on the semiconductor substrate at a position which faces the gate wiring layer across the photodiode. The wiring layer is adjacent to the photodiode.