Solid-State Imaging Device Charge Blocking Layer Dark Current
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Solution Overview
Problem
Solid-state imaging devices face challenges in reducing dark current and improving signal-to-noise (SN) ratio due to the limitations of existing photoelectric devices with organic semiconductors, where dark current is not adequately controlled by previous techniques.
Innovation Solution
A solid-state imaging device is designed with a photoelectric layer containing p-type and n-type organic semiconductors, a charge blocking layer with specific ionization potential and electron affinity differences, and a sealing layer formed by atomic layer deposition (ALD) and physical vapor deposition (PVD) to reduce dark current and enhance SN ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a photoelectric layer made of organic semiconductor is used, then optical cross-talk is minimized and charge diffusion is reduced, but dark current is not sufficiently prevented
Solution Approach 1:
An electron transporting layer is introduced as an intermediary between the pixel electrode and the photoelectric layer. This layer acts as a mediator that facilitates electron transport while preventing direct charge injection from the pixel electrode into the photoelectric layer, thereby reducing dark current without compromising the optical performance of the organic semiconductor photoelectric layer
Solution Approach 2:
The energy level parameters of the charge blocking layer are specifically designed with an ionization potential and electron affinity that differ by at least 1 eV from the photoelectric layer. This parameter change creates an energy barrier that blocks charge injection while maintaining optical transparency, thus reducing dark current while preserving the low optical cross-talk characteristics of the organic semiconductor
2Productivity
If pixel pitch is reduced to increase pixel density, then more pixels can be packed, but the area ratio of circuit region increases and effective photodiode area decreases
Solution Approach 1:
The patent transitions from a planar two-dimensional pixel arrangement to a three-dimensional stacked structure with multiple photoelectric layers positioned at different heights above the substrate. This dimensional change allows circuit regions to be placed in the horizontal plane while photoelectric conversion areas are stacked vertically, enabling higher pixel density without reducing the effective photodiode area in each pixel
3Object-generated harmful factors
If a charge blocking layer is added to prevent charge injection, then dark current is reduced, but device structure becomes more complex
Solution Approach 1:
The electron transporting layer is designed to perform multiple functions simultaneously: it blocks charge injection from the pixel electrode into the photoelectric layer (reducing dark current), facilitates electron transport from the photoelectric layer to the pixel electrode (maintaining signal efficiency), and provides structural support for the stacked configuration. This multi-functionality reduces device complexity despite the additional layer
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 configuration effectively reduces dark current and improves the SN ratio, ensuring improved reliability and preventing deterioration of the photoelectric layer due to stress, while maintaining efficient light collection and minimizing optical cross-talk between pixels.
Implementation Method 1
an organic layer provided on the pixel electrode and having a photoelectric layer generating charges in response to light received
Implementation Method 2
a sealing layer formed by atomic layer deposition (ALD)
Implementation Method 3
a second sealing sublayer formed by physical vapor deposition (PVD)
Data Source
AI summary
A solid-state imaging device includes an array of pixels, each pixel includes: a pixel electrode; an organic layer; a counter electrode; a sealing layer; a color filter; a readout circuit; and a light-collecting unit as defined herein, the photoelectric layer contains an organic p type semiconductor and an organic n type semiconductor, the organic layer further includes a charge blocking layer as defined herein, an ionization potential of the charge blocking layer and an electron affinity of the organic n type semiconductor in the photoelectric layer has a difference of at least 1 eV, and the sealing layer includes a first sealing sublayer formed by atomic layer deposition and a second sealing sublayer formed by physical vapor deposition and containing one of a metal oxide, a metal nitride, and a metal oxynitride.