Stacked Oxide Semiconductor Imaging Element for Interface Stability
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Solution Overview
Problem
The existing solid-state imaging elements, particularly those with a stacked layer structure of IGZO and a photoelectric conversion layer, face challenges in enhancing reliability due to issues like hydrogen diffusion, oxygen deficiency, and carrier concentration fluctuations at the interface between the oxide semiconductor and photoelectric conversion layers.
Innovation Solution
A solid-state imaging element design is introduced, where a first oxide semiconductor layer with higher film density and lower hydrogen concentration is used in conjunction with a second oxide semiconductor layer, both containing IGZO, to suppress hydrogen elimination and oxygen deficiency, thereby stabilizing the interface and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single oxide semiconductor layer is used in the photoelectric conversion element, then the structure is simple, but hydrogen elimination and oxygen deficiency occur at the interface, reducing reliability
Solution Approach 1:
The oxide semiconductor layer is divided into two distinct layers: a first oxide semiconductor layer in contact with the photoelectric conversion layer and a second oxide semiconductor layer beneath it. This segmentation allows each layer to perform specific functions - the first layer suppresses hydrogen elimination at the interface, while the second layer provides bulk semiconductor properties, thereby resolving the contradiction between structural simplicity and interface stability.
Solution Approach 2:
The patent applies different characteristics to different parts of the oxide semiconductor structure. The first oxide semiconductor layer is specifically designed to suppress hydrogen elimination and maintain low hydrogen concentration at the critical interface with the photoelectric conversion layer, while the second layer provides overall semiconductor functionality. This local differentiation of properties enhances interface stability without excessive complexity.
2Reliability
If hydrogen concentration is reduced in the oxide semiconductor layer, then carrier concentration fluctuations are suppressed, but film density may be compromised
Solution Approach 1:
By dividing the oxide semiconductor into two layers, the patent can independently control the hydrogen concentration and film density of each layer. The first layer is optimized for low hydrogen concentration to suppress carrier fluctuations at the interface, while the second layer can be optimized for appropriate film density and overall electrical properties, resolving the contradiction between these two requirements.
Solution Approach 2:
The patent changes multiple parameters simultaneously - specifically, it controls both hydrogen concentration and film density independently in different layers. The first oxide semiconductor layer maintains low hydrogen concentration (≤1×10^20 atoms/cm³) while the second layer provides complementary properties, allowing optimization of both carrier stability and film quality without trade-offs.
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 significantly enhances the reliability of the solid-state imaging element by reducing trap density and carrier concentration fluctuations, leading to improved performance and stability.
Implementation Method 1
a hydrogen concentration of the first oxide semiconductor layer is lower than a hydrogen concentration of the second oxide semiconductor layer
Implementation Method 2
an imaging element having a stacked layer structure of a lower-layer semiconductor layer containing IGZO and an upper-layer photoelectric conversion layer
Data Source
AI summary
To provide a solid-state imaging element capable of further improving reliability. Provided is a solid-state imaging element including at least a first photoelectric conversion section, and a semiconductor substrate in which a second photoelectric conversion section is formed, in this order from a light incidence side, in which the first photoelectric conversion section includes at least a first electrode, a photoelectric conversion layer, a first oxide semiconductor layer, a second oxide semiconductor layer, and a second electrode in this order, and a film density of the first oxide semiconductor layer is higher than a film density of the second oxide semiconductor layer.