Oxide Semiconductor Device With Oxygen Reservoir Insulating Layer
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Solution Overview
Problem
Oxygen vacancies in oxide semiconductor layers lead to reduced electrical characteristics and increased interface states, causing scattering and capture of carriers, which results in decreased field-effect mobility and increased off-state current, affecting the reliability and stability of semiconductor devices.
Innovation Solution
A semiconductor device structure is implemented with an island-shaped oxide semiconductor layer, source and drain electrodes, and a gate electrode, where the oxide layers have a lower electron affinity than the semiconductor layer, and an insulating layer with excess oxygen is used to reduce oxygen vacancies and interface states, and the source and drain electrodes are formed using materials that are easily bonded to oxygen to create low-resistance regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxygen is released from oxide semiconductor during manufacturing, then oxide semiconductor layer is formed, but oxygen vacancies are generated which reduce electrical characteristics
Solution Approach 1:
An insulating layer containing excess oxygen is formed in advance beneath the oxide semiconductor layer. This oxygen reservoir prevents oxygen vacancies from forming during subsequent manufacturing processes by supplying oxygen when needed, thereby maintaining electrical characteristics without compromising manufacturing precision.
Solution Approach 2:
The insulating layer containing excess oxygen acts as an intermediary between the substrate and the oxide semiconductor layer. It mediates oxygen supply to the semiconductor layer, preventing direct oxygen deficiency while allowing the semiconductor layer to form properly during manufacturing.
2Reliability
If interface states are generated at oxide semiconductor-insulating layer interface, then carrier scattering and capture occur, but field-effect mobility decreases and off-state current increases
Solution Approach 1:
The insulating layer is designed with non-uniform oxygen concentration, having excess oxygen specifically at the interface region with the oxide semiconductor layer. This local oxygen enrichment prevents interface state formation at the critical interface, while the rest of the layer maintains its insulating properties.
Solution Approach 2:
The oxygen concentration in the insulating layer is changed from stoichiometric to excess oxygen content. This parameter change transforms the insulating layer from a potential source of oxygen vacancies to an oxygen supply source, preventing interface state generation and improving carrier mobility.
3Adaptability or versatility
If oxide semiconductor layer is used to form transistor channel, then device functionality is achieved, but localized levels reduce electrical characteristics
Solution Approach 1:
The insulating layer containing excess oxygen serves as a cushioning layer that anticipates and prevents oxygen deficiency in the oxide semiconductor layer. By having oxygen already available at the interface before any vacancies can form, it cushions against the development of localized levels that would otherwise degrade electrical characteristics.
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 solution effectively reduces the density of localized levels and interface states, improving the electrical characteristics, stability, and reliability of the semiconductor device by minimizing oxygen vacancies and enhancing field-effect mobility while reducing off-state current.
Implementation Method 1
an insulating layer with excess oxygen is used to reduce oxygen vacancies and interface states
Implementation Method 2
source and drain electrodes are formed using materials that are easily bonded to oxygen to create low-resistance regions
Data Source
AI summary
A semiconductor device includes an oxide semiconductor layer over a first oxide layer; first source and drain electrodes over the oxide semiconductor layer; second source and drain electrodes over the first source and drain electrodes respectively; a second oxide layer over the first source and drain electrodes; a gate insulating layer over the second source and drain electrodes and the second oxide layer; and a gate electrode overlapping the oxide semiconductor layer with the gate insulating layer provided therebetween. The structure in which the oxide semiconductor layer is sandwiched by the oxide layers can suppress the entry of impurities into the oxide semiconductor layer. The structure in which the oxide semiconductor layer is contacting with the source and drain electrodes can prevent increasing resistance between the source and the drain comparing one in which an oxide semiconductor layer is electrically connected to source and drain electrodes through an oxide layer.