Optical Device Isolating Layer Segmentation for Color Mixing Reduction
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Solution Overview
Problem
In solid state image devices, the configuration of photodiodes leads to difficulty in reducing color mixing and enhancing sensitivity due to the inability to effectively isolate electrons, especially with the requirement for miniaturization and increased output electrons per unit area.
Innovation Solution
The optical device includes a semiconductor substrate with specific regions of different impurity types and concentrations, forming a photoelectric converter and isolating layers to inhibit electron flow between adjacent converters, with a grid pattern configuration to surround and isolate the photoelectric converters effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the isolating layer is made sufficiently wide to prevent electron flow, then color mixing is reduced, but cell size cannot be miniaturized
Solution Approach 1:
The isolating layer is divided into multiple p-type diffusion layers (907-1, 907-2, 907-3, 907-4) arranged in a stepped configuration at different depths. This segmentation allows the isolating function to be distributed across multiple smaller units rather than requiring a single wide layer, enabling cell miniaturization while maintaining electron isolation effectiveness.
Solution Approach 2:
The isolating structure transitions from a two-dimensional wide layer to a three-dimensional stepped configuration extending in the depth direction. By utilizing the vertical dimension, the patent achieves effective electron isolation without increasing the horizontal footprint, thereby enabling smaller cell sizes while maintaining color mixing reduction.
2Reliability
If impurity concentration increases in the isolating layer to block electrons, then electron isolation improves, but sensitivity decreases
Solution Approach 1:
Different regions of the isolating layer have different impurity concentrations optimized for their specific functions. The upper p-type diffusion layers have higher impurity concentrations for effective electron blocking, while the lower n-type diffusion layer has lower impurity concentration to maintain photoelectric conversion sensitivity. This local optimization resolves the contradiction between isolation effectiveness and sensitivity.
Solution Approach 2:
The patent changes the impurity concentration parameter across different layers and depths. The p-type diffusion layers have impurity concentrations satisfying the relationship: 907-1 < 907-2 < 907-3 < 907-4, creating an electric potential gradient that blocks electrons while the n-type layer maintains appropriate sensitivity characteristics through different doping levels.
3Ease of manufacture
If the isolating layer uses uniform impurity concentration, then manufacturing is simplified, but electron blocking effectiveness decreases
Solution Approach 1:
The isolating layer is segmented into multiple discrete p-type diffusion layers that can be formed through separate doping processes. Each layer can be independently controlled and optimized, providing electron blocking effectiveness that uniform layers cannot achieve, while the modular structure maintains reasonable manufacturing complexity.
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 reduces color mixing and enhances sensitivity by effectively inhibiting electron flow into adjacent converters, allowing for improved light collection and increased output electrons per unit area.
Implementation Method 1
electrons 911 generated through photoelectric conversion of incident light 910 are inhibited from passing through the isolating layer 907
Data Source
AI summary
An optical device includes a first region and an isolating layer which are each provided in a semiconductor substrate. The first region configures a photoelectric converter and includes at least an impurity of a first conductivity type. The isolating layer is configured to inhibit passage of electrons. The isolating layer includes a second region which is below the first region and which includes an impurity of a second conductivity type, a third region which surrounds the first region in plan-view thereof and which includes an impurity of the second conductivity type, and a fourth region which surrounds the second region in plan-view thereof and which is connected to the third region. The fourth region is greater in width than a connecting part of the third region which connects the third region to the fourth region.