Oxide TFT Active Layer Structure for Mobility and Reliability
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Solution Overview
Problem
Oxide semiconductor thin film transistors (TFTs) suffer from low mobility and reliability issues due to physical and chemical damage, which are exacerbated by their amorphous structure, particularly in gate-in-panel (GIP) structures where numerous TFTs are integrated in display panels.
Innovation Solution
A multilayer structure is applied to the active layer of TFTs, comprising an amorphous and crystalline oxide semiconductor layers, with specific doping and heat treatment processes to enhance mobility and reliability, including a crystalline structure in the second oxide semiconductor layer and amorphous structures in other layers to improve channel layer performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxide semiconductor thin film transistors are manufactured with amorphous structure, then manufacturing cost is reduced and manufacturing process is simplified, but mobility and reliability deteriorate due to physical and chemical damage
Solution Approach 1:
The active layer is segmented into multiple oxide semiconductor layers with different crystalline structures. The first and third layers have amorphous structure while the second layer has crystalline structure, allowing each layer to fulfill different functional requirements - the amorphous layers provide ease of manufacture while the crystalline layer provides high mobility and reliability
Solution Approach 2:
Different regions of the active layer are given different local qualities in terms of crystalline structure. Specifically, the second oxide semiconductor layer is formed with a crystalline structure to locally enhance mobility and reliability where the channel formation is critical, while other layers maintain amorphous structure for manufacturing simplicity
2Temperature
If oxide semiconductor thin film transistors are manufactured with amorphous structure, then manufacturing temperature is reduced, but mobility deteriorates
Solution Approach 1:
The active layer is divided into multiple oxide semiconductor layers with different crystalline structures. The first and third layers are formed at lower temperatures with amorphous structure, while the second layer is formed at higher temperature with crystalline structure to achieve high mobility without requiring the entire manufacturing process to be at high temperature
Solution Approach 2:
The crystalline structure parameter is changed selectively in the second oxide semiconductor layer to enhance mobility. By controlling the crystallization process specifically for the second layer through temperature and time parameters, high mobility is achieved while maintaining lower overall manufacturing temperature
3Productivity
If gate driver is embedded in display panel with numerous TFTs, then display apparatus performance is improved, but physical and chemical damage increases causing deterioration
Solution Approach 1:
The active layer uses a composite structure of multiple oxide semiconductor layers with different crystalline structures. This composite material approach allows the transistor to achieve the high performance needed for gate-in-panel applications while the crystalline second layer provides enhanced resistance to physical and chemical damage, improving overall reliability
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 proposed structure enhances TFT mobility and reliability, allowing for improved performance in display apparatuses by reducing electron traps and maintaining stable electrical properties, particularly suitable for gate drivers and pixel driving circuits.
Implementation Method 1
the second oxide semiconductor layer has a crystalline structure
Implementation Method 2
A multilayer structure is applied to the active layer of TFTs, comprising an amorphous and crystalline oxide semiconductor layers, with specific doping and heat treatment processes to enhance mobility and reliability
Data Source
AI summary
The present disclosure relates to thin film transistor substrate, manufacturing method thereof and display apparatus comprising the same. The thin film transistor substrate includes a first thin film transistor and a second thin film transistor on a base substrate, the first thin film transistor includes a first active layer on the base substrate, and a first gate electrode spaced apart from the first active layer and overlapping at least part of the first active layer, and the second thin film transistor includes a second active layer on the base substrate and a second gate electrode spaced apart from the second active layer and overlapping at least part of the second active layer, the first active layer includes a first oxide semiconductor layer and a second oxide semiconductor layer on the first oxide semiconductor layer, the second active layer includes a first oxide semiconductor layer and a second oxide semiconductor layer on the first oxide semiconductor layer, a third oxide semiconductor layer on the second oxide semiconductor layer.