In-Zn-Hf Oxide Semiconductor TFT Mobility
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Solution Overview
Problem
Conventional amorphous silicon thin film transistors (a-Si TFTs) are limited in mobility and image quality, while polycrystalline silicon TFTs (poly-Si TFTs) offer higher performance but are costly and complex to manufacture, making them unsuitable for larger-sized displays.
Innovation Solution
Development of oxide semiconductors comprising Zn, In, and Hf, with Hf concentrations between 2-16 at%, used in thin film transistors (TFTs) to enhance mobility and image quality, allowing for more reliable and cost-effective manufacturing on larger substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional amorphous silicon TFTs are used, then manufacturing is simple and cost-effective, but mobility is low (about 0.5 cm2/Vs) and image quality is limited
Solution Approach 1:
The patent uses a composite oxide semiconductor material comprising In, Ga, and Zn oxides in specific ratios (In: 30-70 at%, Ga: 5-40 at%, Zn: 20-50 at%). This composite material achieves high mobility comparable to poly-Si TFTs while maintaining the manufacturing simplicity of amorphous semiconductor processes, thus resolving the contradiction between performance and ease of manufacture.
Solution Approach 2:
The patent optimizes the atomic ratio parameters of the oxide semiconductor components (In, Ga, Zn) to achieve the desired mobility. By carefully controlling the composition parameters within specific ranges, the material achieves high performance while remaining compatible with existing manufacturing processes.
2Reliability
If poly-Si TFTs are used, then mobility is high (several tens to hundreds of cm2/Vs) and image quality is improved, but manufacturing process becomes more complex and costs increase
Solution Approach 1:
The patent employs a composite oxide semiconductor material that achieves poly-Si level mobility without requiring the complex multi-step crystallization processes needed for poly-Si TFTs. The specific composition of In, Ga, and Zn oxides enables high performance through a simpler single-step deposition process.
Solution Approach 2:
The patent uses an amorphous oxide semiconductor that can be deposited using relatively low-temperature processes, avoiding the need for expensive high-temperature equipment and complex process control required for poly-Si TFTs, thus reducing manufacturing complexity and cost.
3Reliability
If poly-Si TFTs are used for larger-sized substrates, then high image quality can be achieved, but uniformity and manufacturing limits restrict application to substrates greater than 1 m2
Solution Approach 1:
The composite oxide semiconductor material can be deposited uniformly over large substrate areas using low-temperature processes, overcoming the uniformity issues that limit poly-Si TFT fabrication on large substrates. This enables high-quality displays with substrate sizes exceeding 1 m2.
Solution Approach 2:
By changing the material composition parameters to use oxide semiconductors with specific In, Ga, and Zn ratios, the patent achieves both high image quality and scalability to large substrate sizes, removing the area limitations of poly-Si TFTs.
4Ease of manufacture
If conventional ZnO-based oxide semiconductors are used, then low-temperature manufacturing is possible, but mobility is not sufficiently high for high-performance applications
Solution Approach 1:
The patent creates a composite oxide semiconductor by combining In, Ga, and Zn oxides in specific ratios. This composite structure achieves high mobility comparable to poly-Si while maintaining the low-temperature manufacturing advantage of conventional ZnO-based materials, thus resolving the contradiction between ease of manufacture and reliability.
Data Source
AI summary
Provided are oxide semiconductors and thin film transistors of the same. An oxide semiconductor includes Zn, In and Hf. The amount of Hf is in the range of about 2-16 at %, inclusive, based on the total amount of Zn, In, and Hf. A thin film transistor includes a gate and a gate insulating layer arranged on the gate. A channel corresponding to the gate is formed on the gate insulating layer. The channel includes an oxide semiconductor. The semiconductor oxide includes Zn, In and Hf. The amount of Hf is in the range of about 2-16 at %, inclusive, based on the total amount of Zn, In, and Hf. A source and a drain contact respective sides of the channel.