Amorphous Multicomponent Dielectric for Low-Temperature TFTs
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Solution Overview
Problem
Conventional transparent thin-film transistors (TFTs) face challenges in achieving high performance at low processing temperatures, particularly around 150°C, due to issues with dielectric crystallinity, leakage current, and interface defects, which limit their integration in flexible and low-cost substrates and compatibility with advanced display technologies.
Innovation Solution
The use of multicomponent amorphous binary oxide dielectrics, such as Ta2O5 combined with SiO2 or Al2O3, produced by sputtering, which offer improved short-range ordering and disorder, reducing crystallization and enhancing semiconductor/dielectric interfaces, resulting in devices with high κ values and low leakage currents, comparable to those processed at higher temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional dielectrics (SiO2, Al2O3) are used at low processing temperatures (150°C), then manufacturing cost and substrate compatibility are improved, but device performance (leakage current, mobility) deteriorates
Solution Approach 1:
The patent uses composite dielectric materials combining high-κ materials (Ta2O5, HfO2) with wide band gap materials (SiO2, Al2O3) to achieve both low processing temperature compatibility and high device performance. The composite structure allows low-temperature deposition while providing high dielectric constant for good electrical characteristics and wide band gap for low leakage current.
Solution Approach 2:
The patent changes the dielectric constant (κ) parameter by selecting high-κ materials (Ta2O5: κ≈25, HfO2: κ≈20) to improve device performance at low temperatures, and adjusts the band gap parameter by combining with wide band gap materials (SiO2: Eg≈9 eV, Al2O3: Eg≈8.7 eV) to reduce leakage current, thereby resolving the performance limitation at low processing temperatures.
2Reliability
If high-κ materials (Ta2O5) are used to improve device performance, then dielectric constant and mobility are improved, but leakage current increases due to low band offset
Solution Approach 1:
The patent creates composite dielectric layers combining high-κ materials (Ta2O5, HfO2) with wide band gap materials (SiO2, Al2O3). This composite structure maintains the high dielectric constant for good mobility while the wide band gap component provides high band offset to suppress leakage current, thus resolving the contradiction between mobility enhancement and leakage reduction.
Solution Approach 2:
The patent applies different material properties to different parts of the dielectric structure: the high-κ material component provides high dielectric constant for charge storage and mobility enhancement, while the wide band gap material component provides high band offset for leakage suppression. Each component performs its specific function locally within the composite structure.
3Object-generated harmful factors
If multicomponent dielectrics are used to reduce leakage current, then band offset is improved, but manufacturing complexity increases
Solution Approach 1:
The patent uses composite materials combining wide band gap materials (SiO2, Al2O3) with high-κ materials to achieve high band offset and low leakage current. While the material composition becomes more complex, the deposition process remains relatively simple using conventional sputtering techniques, and the composite structure provides superior electrical characteristics that justify the increased material complexity.
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
These multicomponent dielectrics enable TFTs with enhanced performance, including high field-effect mobility, low subthreshold slope, and high on/off ratios, suitable for integration in active matrix liquid crystal displays and other demanding applications, while maintaining stability under stress conditions.
Implementation Method 1
The use of multicomponent amorphous binary oxide dielectrics, such as Ta2O5 combined with SiO2 or Al2O3, produced by sputtering
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 2c~2d
AI summary
High performance thin-film, transistors entirely processed at temperatures not exceeding 150°C, using amorphous multi component dielectrics based on t.he mixture of high band gap and high dielectric constant ( K) materials are presented in this invention. The invention relates to the use of sputtered or ink jet printed mixed dielectric materials such as Ta2O5 with SiO2 or Al2O3 or HfO2 with SiO2 or Al2O3. These multicomponent dielectrics allow producing amorphous dielectrics to be introduced in high stable electronic devices with low leakage currents, while preserving a high dielectric constant. This results in producing thin film transistors with remarkable electrical properties, such as the ones produced based on Ga-In-Zn oxide as channel layers and where the dielectric was the combination of the mixture Ta2O5:SiO2, exhibiting field- effect mobility exceeding 35 cm2 V-1 s-1, close to 0 V turn- on voltage, on/off ratio higher than 106 and subthreshold slope below 0.24 V dec-1.