Oxide Cluster Thin Film Transistor for Mobility and Off Current
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Solution Overview
Problem
The field effect mobility of thin film transistors using oxide semiconductors is lower than those using polycrystalline silicon, which is a concern for large-screen or high-definition liquid crystal display devices requiring higher drive currents, and there is a need to suppress off current while enhancing mobility.
Innovation Solution
Incorporating oxide clusters with higher electrical conductance than the oxide semiconductor layer between the oxide semiconductor layer and the gate insulating layer, and using a buffer layer with higher carrier concentration to improve electrical connectivity and reduce off current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If oxide semiconductor layer is used for thin film transistor channel, then manufacturing temperature can be reduced to 300°C or lower, but field effect mobility becomes lower than polycrystalline silicon
Solution Approach 1:
The patent applies local quality by creating oxide clusters with different properties (higher carrier concentration and electrical conductance) at specific locations within the oxide semiconductor layer, particularly at the interface with the gate insulating layer. This localized modification improves field effect mobility without changing the overall low-temperature manufacturing process, allowing the bulk material to remain suitable for low-temperature fabrication while the localized oxide clusters provide enhanced electrical performance.
Solution Approach 2:
The patent employs composite materials by combining the oxide semiconductor layer with embedded oxide clusters having different compositional characteristics. The oxide clusters contain higher proportions of metal elements (In, Ga, Zn) compared to the surrounding oxide semiconductor matrix, creating a composite structure that exhibits superior electrical conductance and carrier concentration, thereby resolving the mobility limitation while preserving low-temperature manufacturability.
2Reliability
If oxide clusters with higher electrical conductance are formed, then field effect mobility increases, but off current may increase
Solution Approach 1:
The oxide clusters are strategically positioned at the interface between the oxide semiconductor layer and the gate insulating layer, creating localized high-conductance regions only where needed for improving channel conductivity. This localized approach enhances field effect mobility while limiting the spatial extent of high conductance, thereby preventing excessive off current in regions outside the cluster locations.
Solution Approach 2:
The patent controls the carrier concentration and electrical conductance parameters of the oxide clusters to fall within specific ranges that optimize field effect mobility while maintaining acceptable off current levels. By adjusting the metal element ratios and cluster size, the electrical parameters are tuned to achieve the desired balance between on-state conductivity and off-state leakage suppression.
Data Source
AI summary
In a thin film transistor including an oxide semiconductor, an oxide cluster having higher electrical conductance than the oxide semiconductor layer is formed between the oxide semiconductor layer and a gate insulating layer, whereby field effect mobility of the thin film transistor can be increased and increase of off current can be suppressed.