In-Sn-Zn Oxide Semiconductor Layer for High-Mobility Transistors
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Solution Overview
Problem
Conventional field effect transistors face challenges with silicon-based semiconductors due to high production costs, low mobility, and instability under direct current stress, while oxide semiconductors suffer from poor characteristics and high-temperature requirements, making them unsuitable for large-area, high-frequency displays.
Innovation Solution
A field effect transistor with a semiconductor layer composed of indium oxide, zinc oxide, and tin oxide, where the atomic composition ratio of Zn/(In+Sn+Zn) is between 25 and 75 atom % and Sn/(In+Sn+Zn) is less than 50 atom %, along with a protective layer, to achieve improved mobility, stability, and reduced off current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If crystalline silicon is used for high-speed operation, then mobility is improved, but high-temperature heating (800°C or higher) is required which increases production cost and complexity
Solution Approach 1:
The patent changes the material composition parameters by incorporating Sn and Zn atoms into the oxide semiconductor lattice, which modifies the electronic structure and carrier transport properties. This allows achieving high mobility without requiring high-temperature crystallization processes, thus resolving the contradiction between speed and production complexity
Solution Approach 2:
The patent uses a composite oxide semiconductor material containing In, Sn, and Zn atoms with specific atomic ratios. This composite structure combines the advantages of different metal oxides to achieve high mobility at lower processing temperatures, avoiding the need for complex high-temperature crystalline silicon fabrication processes
2Area of stationary object
If amorphous silicon is used for large-area substrates, then area is increased, but mobility is limited to about 0.5 cm2/Vs resulting in low switching speed
Solution Approach 1:
The patent changes the compositional parameters by adding Sn and Zn atoms to the oxide semiconductor, which significantly improves carrier mobility from the typical 0.5 cm2/Vs of amorphous silicon to over 10 cm2/Vs. This allows large-area substrates to achieve both high area coverage and high switching speed
Solution Approach 2:
The patent introduces specific metal atoms (Sn and Zn) at controlled concentrations within the oxide semiconductor structure to locally enhance carrier transport properties. This localized compositional optimization enables high mobility throughout the large-area substrate without compromising the amorphous structure's ease of fabrication
3Area of stationary object
If amorphous silicon is used for large-area displays, then area is increased, but stability under direct current stress is reduced
Solution Approach 1:
The patent employs a composite oxide semiconductor material containing In, Sn, and Zn atoms with specific atomic ratios. This composite structure provides both the large-area fabricability of amorphous materials and the DC stress stability typically associated with crystalline structures, resolving the contradiction between area and reliability
Solution Approach 2:
The patent replaces expensive and unstable amorphous silicon with a cost-effective oxide semiconductor composition that provides superior stability. The specific In-Sn-Zn oxide formulation offers long-term reliability under DC stress while maintaining ease of large-area fabrication
4Temperature
If conventional oxide semiconductor is used, then formation temperature is reduced, but mobility is low and off current is high
Solution Approach 1:
The patent changes the compositional parameters by incorporating Sn and Zn atoms into the oxide semiconductor at specific atomic ratios. This compositional modification enhances carrier mobility and reduces off-state current while maintaining the low formation temperature advantage of oxide semiconductors
Solution Approach 2:
The patent introduces Sn and Zn atoms at specific concentrations (Sn: 1-30 at%, Zn: 30-70 at%) within the oxide semiconductor structure to locally optimize electronic properties. This localized compositional control achieves high mobility and low off current without requiring high-temperature processing
5Reliability
If Ga is added to oxide semiconductor to improve stability, then moisture resistance is improved, but TFT characteristics (mobility and S value) are deteriorated and cost increases
Solution Approach 1:
The patent replaces expensive Ga with a cost-effective combination of Sn and Zn atoms in the oxide semiconductor. This substitution maintains or improves moisture resistance while preserving high mobility and avoiding the performance degradation and cost increase associated with Ga addition
Solution Approach 2:
The patent uses a composite In-Sn-Zn oxide semiconductor material where Sn and Zn work synergistically to provide both stability and high mobility. This composite approach eliminates the need for Ga while achieving superior TFT characteristics through the coordinated effect of multiple metal atoms
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 provides a field effect transistor with enhanced transistor characteristics, including high mobility, low off current, and improved reliability, suitable for display panels without the need for gallium, a rare and costly metal.
Implementation Method 1
a sputtering target for forming a semiconductor film, wherein an atomic composition ratio of Zn atoms to total atoms of the In atoms, the Sn atoms, and the Zn atoms is 25 atom % or more and 75 atom % or less, and an atomic composition ratio of the Sn atoms to total atoms of the In atoms, the Sn atoms, and the Zn atoms is less than 50 atom %
Data Source
AI summary
A field effect transistor including: a substrate, and at least gate electrode, a gate insulating film, a semiconductor layer, a protective layer for the semiconductor layer, a source electrode and a drain electrode provided on the substrate, wherein the source electrode and the drain electrode are connected with the semiconductor layer therebetween, the gate insulating film is between the gate electrode and the semiconductor layer, the protective layer is on at least one surface of the semiconductor layer, the semiconductor layer includes an oxide containing In atoms, Sn atoms and Zn atoms, the atomic composition ratio of Zn/(In+Sn+Zn) is 25 atom % or more and 75 atom % or less, and the atomic composition ratio of Sn/(In+Sn+Zn) is less than 50 atom %.