In-Zn-Sn Composite Oxide Sputtering Target for TFTs
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Solution Overview
Problem
The development of thin film transistors (TFTs) using silicon-based semiconductors faces challenges such as high temperature requirements for crystalline silicon formation, limited cost reduction due to complex device structures, and low switching speed with amorphous silicon, while oxide semiconductor films with zinc oxide exhibit poor mobility, high leakage current, and instability during sputtering.
Innovation Solution
A composite oxide sintered body comprising indium (In), zinc (Zn), and tin (Sn) with specific atomic ratios and properties is used to create a sputtering target, producing an amorphous oxide film with improved uniformity, reproducibility, and yield, which is then used in a thin film transistor as a channel layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a crystalline silicon thin film is formed to achieve high-speed operation, then switching speed is improved, but high temperature processing (800°C or more) is required which limits substrate choices and increases cost
Solution Approach 1:
The invention changes the material parameter from crystalline silicon to oxide semiconductor (In-Zn-Sn-O), which fundamentally alters the processing temperature requirement from 800°C or more to below 450°C, enabling formation on glass and organic substrates while maintaining transistor functionality
Solution Approach 2:
The invention uses a composite oxide material containing In, Zn, and Sn in specific ratios (0.1<In/(In+Zn+Sn)<0.6, 0.2<Zn/(In+Zn+Sn)<0.7, 0.05<Sn/(In+Zn+Sn)<0.3) to achieve both low-temperature processability and high mobility, combining advantages of different materials
2Ease of manufacture
If an amorphous silicon thin film is formed to enable low temperature processing, then substrate compatibility is improved, but switching speed deteriorates
Solution Approach 1:
The invention changes the material composition from amorphous silicon to oxide semiconductor with specific In-Zn-Sn ratios, achieving both low-temperature processability (<450°C) and high mobility (1-10 cm²/Vs or higher), simultaneously improving both substrate compatibility and switching speed
Solution Approach 2:
The invention introduces tin (Sn) as a dopant element in specific concentrations (0.05<Sn/(In+Zn+Sn)<0.3) to locally enhance carrier density and mobility in the oxide semiconductor, improving switching speed without compromising low-temperature processing capability
3Ease of manufacture
If a transparent oxide film containing zinc oxide is formed by sputtering to achieve low cost processing, then manufacturing simplicity is improved, but film uniformity and reproducibility deteriorate due to abnormal discharge
Solution Approach 1:
The invention changes the target material composition from simple ZnO to a composite In-Zn-Sn-O oxide with specific ratios, which modifies the sputtering discharge characteristics to eliminate abnormal discharge while maintaining process simplicity and improving film uniformity and reproducibility
Solution Approach 2:
The invention uses a composite oxide target containing In, Zn, and Sn in specific proportions to stabilize the sputtering process, preventing abnormal discharge and ensuring consistent film quality across large-area substrates while maintaining manufacturing simplicity
4Manufacturing precision
If the number of tin oxide aggregate particles is reduced to improve film quality, then manufacturing precision is improved, but the complexity of target fabrication increases
Solution Approach 1:
The invention optimizes the sintering parameters (temperature, time, atmosphere) and target composition to naturally suppress tin oxide aggregate formation during target fabrication, achieving high film quality through controlled material science rather than complex post-processing
Solution Approach 2:
The invention incorporates tin oxide aggregate suppression measures during the target fabrication stage itself (through composition design and sintering control), preventing aggregate formation before film deposition rather than requiring complex remediation steps afterward
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 approach enhances the uniformity and reproducibility of TFT characteristics and yield, reduces the number of tin oxide aggregate particles, and achieves stable discharge during sputtering, leading to improved TFT performance with increased mobility and reduced leakage current.
Implementation Method 1
a sputtering target that includes the composite oxide sintered body, an amorphous oxide film obtained using the sputtering target
Implementation Method 2
an oxide semiconductor film formed of a conductive transparent oxide that contains zinc oxide as the main component tends to produce a large number of carrier electrons due to oxygen defects
Implementation Method 3
A composite oxide sintered body comprising In, Zn, and Sn, and having a relative density of 90% or more, an average crystal grain size of 10 μm or less
Data Source
AI summary
A composite oxide sintered body includes In, Zn, and Sn, and has a relative density of 90% or more, an average crystal grain size of 10 μm or less, and a bulk resistance of 30 mΩcm or less, the number of tin oxide aggregate particles having a diameter of 10 μm or more being 2.5 or less per mm2 of the composite oxide sintered body.