Photoelectric Pixel Layer Structure for Dark Current Suppression
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Solution Overview
Problem
In back-illuminated solid-state image capturing elements, the dark current levels in light-shielded pixel regions remain higher than in light-receiving pixel regions, leading to deteriorated pixel performance, and the use of hydrogen-containing insulating layers to mitigate dark current is undesirable due to charge cancellation effects with metal oxide layers.
Innovation Solution
A photoelectric conversion device with a semiconductor layer having distinct layered structures in light-receiving and light-shielded pixel regions, where a metal oxide layer and insulating layers are stacked, including a hydrogen-containing insulating layer in the light-shielded region, separated by an additional insulating layer to alleviate charge accumulation effects and reduce dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a metal oxide layer is formed over the entire pixel region to reduce dark current, then dark current is reduced, but the OB step occurs causing pixel performance deterioration
Solution Approach 1:
The patent applies different layered structures to different regions: the light-receiving pixel region has a simple structure with metal oxide layer and insulating layer, while the light-shielded pixel region has an additional hydrogen-containing insulating layer. This local differentiation allows dark current suppression in OB pixels without affecting light-receiving pixel performance.
Solution Approach 2:
The hydrogen-containing insulating layer acts as an intermediary between the metal oxide layer and the light-shielded pixel region. It provides positive fixed charges that compensate for negative charges in the metal oxide layer, reducing the OB step while maintaining dark current suppression benefits.
2Object-affected harmful factors
If a hydrogen-containing insulating layer with positive fixed charge is arranged in the OB pixel region to inactivate dark current source, then dark current is reduced, but the metal oxide layer cancels the charge accumulation effect increasing OB step
Solution Approach 1:
The hydrogen-containing insulating layer is placed only in the light-shielded pixel region, creating local charge compensation. This allows the positive fixed charges to interact with and reduce the negative charge accumulation from the metal oxide layer specifically where needed, minimizing the OB step while maintaining dark current suppression.
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 the OB step and improves pixel performance by managing dark current levels and charge accumulation, allowing for high-precision image capturing without degrading the transistor functionality in peripheral circuits.
Implementation Method 1
the dark current source is inactivated by a charge accumulation effect of the metal oxide layer
Implementation Method 2
arranging an insulating layer including hydrogen (hydrogen-containing insulating layer) in the OB pixel region to inactivate the dark current source itself by hydrogen of the hydrogen-containing insulating layer
Implementation Method 3
the metal oxide layer having high-density fixed charges is formed on the light incident surface, and the dark current source is inactivated by a charge accumulation effect of the metal oxide layer
Data Source
AI summary
A photoelectric conversion device having a light-receiving pixel region and a light-shielded pixel region, the photoelectric conversion device comprising: a semiconductor layer; a first layered structure which is arranged on a first surface of the semiconductor layer in the light-receiving pixel region and in which at least an insulating layer and a metal oxide layer arranged between the semiconductor layer and the insulating layer are stacked; and a second layered structure which is arranged on the first surface of the semiconductor layer in the light-shielded pixel region and in which at least a light-shielding layer, a metal oxide layer arranged between the semiconductor layer and the light-shielding layer, a first insulating layer arranged between the metal oxide layer and the light-shielding layer, and a second insulating layer arranged between the first insulating layer and the light-shielding layer and including hydrogen are stacked.