Solid-State Image Sensor Dark Current Suppression via Impurity Regions
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Solution Overview
Problem
The existing stack type solid-state image sensing devices suffer from poor light utilization efficiency and false color issues due to the configuration of color filters, and they also experience image quality deterioration due to dark current generated from lattice defects in the semiconductor substrate.
Innovation Solution
The device incorporates first and second impurity regions of the same conduction type for signal charge accumulation and reading, with third impurity regions of a different conduction type acting as a potential barrier between them, reducing signal charge flow through the substrate and minimizing dark current influence. Additionally, fourth impurity regions are used to ensure complete depletion of the second impurity regions for efficient signal transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal charge is accumulated in the n+ region and read through the surface of the n-type semiconductor substrate, then the signal charge reading function is achieved, but dark current generated from lattice defects in the substrate surface is included in the signal charge, causing image quality deterioration
Solution Approach 1:
The patent introduces a p-type region as an intermediary between the n+ region and the n-type semiconductor substrate surface. This p-type region acts as a mediator that blocks the direct path of dark current from the substrate surface to the signal charge accumulation region, while still allowing the signal charge reading function to operate through the designed electrode structure.
Solution Approach 2:
The patent extracts the harmful dark current path from the signal charge reading path by introducing the p-type region. The dark current generation path through the substrate surface is separated and blocked, while the signal charge reading function is maintained through the external electrode connection that bypasses the substrate surface.
2Measurement precision
If color filters are used in the solid-state image sensing device, then color detection is achieved, but light utilization efficiency is poor and false color occurs
Solution Approach 1:
The patent replaces the optical filtering mechanism (color filters) with an electrical detection mechanism. Instead of using physical color filters to separate wavelengths, the invention uses multiple photoelectric conversion films with different band structures to directly convert different wavelength lights into electrical signals, eliminating the energy loss associated with optical filtering.
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 dark current, leading to improved image quality by reducing signal charge flow through the substrate and enhancing the transfer efficiency, resulting in high-quality image sensing.
Implementation Method 1
three photoelectric conversion films for detecting red (R), green (G) and blue (B) light are stacked above a semiconductor substrate in such a manner that signal charges generated in the respective films are accumulated
Implementation Method 2
third impurity regions of a second conduction type provided in the surface of the semiconductor substrate and between the first impurity regions and the signal charge reading regions and reverse to the first conduction type
Data Source
AI summary
A solid-state image sensing device provided with photoelectric conversion films stacked above a semiconductor substrate, comprising: first impurity regions as defined herein; second impurity regions as defined herein; signal charge reading regions as defined herein; and third impurity regions as defined herein.