HfInZnO Oxide Semiconductor Transistor with Zn Gradient
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Solution Overview
Problem
Current oxide semiconductor thin film transistors, particularly those using InGaZnO, suffer from characteristic deterioration when exposed to plasma or external agents, and the conditions for forming an etch stop layer can further degrade their performance, limiting their stability and mobility.
Innovation Solution
A thin film transistor with an HfInZnO-based oxide semiconductor layer featuring a Zn concentration gradient, where the Zn concentration decreases towards the channel region for enhanced mobility and increases towards the surface for stability, eliminating the need for an etch stop layer and simplifying manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an etch stop layer is disposed on the oxide semiconductor layer to protect it, then the oxide semiconductor layer is protected from plasma and external agents, but the electrical characteristics of the oxide semiconductor device severely deteriorate
Solution Approach 1:
The invention changes the compositional parameters of the oxide semiconductor layer itself, creating a gradient in Zn concentration from the lower portion (closer to gate insulating layer) to the upper portion. This parameter change allows the layer to inherently resist plasma and external agents without requiring an additional etch stop layer, thus avoiding electrical characteristic deterioration.
Solution Approach 2:
The invention creates a composite structure within the oxide semiconductor layer by combining different concentrations of Zn within the same HfInZnO-based material system. This internal composition gradient creates regions with different properties: lower Zn concentration near the gate for good electrical characteristics and higher Zn concentration toward the surface for plasma resistance, eliminating the need for separate protective layers.
2Productivity
If the oxide semiconductor layer uses commonly used InGaZnO composition, then it can be manufactured at low temperature with high mobility, but its characteristics deteriorate when exposed to plasma or external agents
Solution Approach 1:
The invention applies local quality by creating different Zn concentrations at different positions within the oxide semiconductor layer. The lower portion (near gate insulating layer) has lower Zn concentration to maintain good electrical characteristics and mobility, while the upper portion has higher Zn concentration to provide resistance against plasma and external agents. This spatial variation in composition resolves the contradiction between mobility and stability.
Solution Approach 2:
The invention modifies the compositional parameters of the oxide semiconductor layer by introducing a Zn concentration gradient. This parameter change allows the material to maintain low-temperature manufacturability and high mobility while simultaneously improving stability against plasma and external agents through the compositional variation.
3Reliability
If poly-Si TFTs are used to achieve high mobility and embed data driving circuits, then electron mobility reaches several tens to hundreds of cm2/Vs, but the crystallization process becomes complicated and manufacturing costs increase
Solution Approach 1:
The invention changes the material composition parameters of the semiconductor layer to HfInZnO-based oxide semiconductor with a Zn concentration gradient. This compositional change enables the material to achieve high electron mobility similar to poly-Si TFTs while maintaining amorphous structure that can be deposited at low temperatures without complex crystallization processes, thus reducing manufacturing complexity and costs.
Data Source
AI summary
A thin film transistor including: a substrate; a gate electrode formed on the substrate; a gate insulating layer formed on the gate electrode and exposed portions of the substrate; an oxide semiconductor layer formed on the gate insulating layer to correspond to the gate electrode, and comprising an HfInZnO-based oxide semiconductor, wherein the oxide semiconductor layer has a Zn concentration gradient; and source and drain regions respectively formed on both sides of the oxide semiconductor layer and the gate insulating layer.