Oxide Semiconductor Channel Crystallization for Stable TFT Operation
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Solution Overview
Problem
Existing oxide semiconductor materials, such as those based on InGaO3(ZnO)m, do not achieve adequate characteristics despite their potential for high-performance applications in field-effect transistors, particularly in terms of crystallinity and reliability.
Innovation Solution
A semiconductor device is developed using a purified oxide semiconductor layer with a crystalline region, where the second oxide semiconductor layer is grown from the crystalline region of the first oxide semiconductor layer, and both layers have c-axis alignment perpendicular to the surface, ensuring high crystallinity and low impurity entry, thereby enhancing electrical anisotropy and reducing threshold voltage shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If amorphous silicon is used for large-area display devices, then large area can be satisfied, but high-speed operation cannot be achieved
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to oxide semiconductor (In-Ga-Zn-O), which fundamentally alters the electrical characteristics and enables high-speed operation while maintaining large-area compatibility through low-temperature processing
Solution Approach 2:
The patent uses a composite structure combining oxide semiconductor layer with metal electrodes and insulating layers, creating a thin-film transistor that achieves both large-area fabrication and high-speed performance through material composition optimization
2Reliability
If oxide semiconductor materials are used to improve field-effect transistor characteristics, then high-performance applications can be achieved, but adequate crystallinity and reliability are not obtained
Solution Approach 1:
The patent utilizes phase transition from amorphous to crystalline state of oxide semiconductor through controlled heating, transforming the material structure to achieve both high crystallinity and reliable electrical characteristics in the channel formation region
Solution Approach 2:
The patent changes the thermal processing parameters and material composition to induce crystallization of the oxide semiconductor layer, transforming it from an amorphous state with poor reliability to a crystalline state with stable composition and high 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 approach results in a semiconductor device with improved reliability and stable electric characteristics, including reduced temperature dependence of on-state and off-state currents, and increased field-effect mobility, suitable for various applications including display panels and driver circuits.
Implementation Method 1
a first oxide semiconductor layer including a crystalline region formed by growth from a surface of the first oxide semiconductor layer toward an inside
Data Source
AI summary
An embodiment is a semiconductor device which includes a first oxide semiconductor layer over a substrate having an insulating surface and including a crystalline region formed by growth from a surface of the first oxide semiconductor layer toward an inside; a second oxide semiconductor layer over the first oxide semiconductor layer; a source electrode layer and a drain electrode layer which are in contact with the second oxide semiconductor layer; a gate insulating layer covering the second oxide semiconductor layer, the source electrode layer, and the drain electrode layer; and a gate electrode layer over the gate insulating layer and in a region overlapping with the second oxide semiconductor layer. The second oxide semiconductor layer is a layer including a crystal formed by growth from the crystalline region.