Oxide Semiconductor FET Ga Gradient for Leakage and Stability
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Solution Overview
Problem
Field effect transistors with oxide semiconductors face challenges in reducing leakage current due to the short channel effect, particularly in maintaining electrical stability and reliability as the degree of integration increases.
Innovation Solution
A field effect transistor design incorporating an oxide semiconductor layer with a sub semiconductor layer having a higher Ga content directly on the dielectric layer, which decreases as distance from the interface increases, and a main semiconductor layer with lower Ga content, along with a dielectric layer structure to buffer oxygen atom movement and suppress oxygen vacancy formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxide semiconductor layers are used to reduce leakage current, then leakage current is reduced, but oxygen vacancy formation occurs leading to degraded electrical stability
Solution Approach 1:
The oxide semiconductor layer is divided into multiple layers with different metal element compositions. The first oxide semiconductor layer contains indium and zinc but no gallium, while the second oxide semiconductor layer contains gallium. This segmentation prevents oxygen vacancy formation at the interface while maintaining low leakage current characteristics throughout the structure.
Solution Approach 2:
Different regions of the oxide semiconductor layer are assigned different compositions tailored to local requirements. The first layer (closer to the interface) uses In-Zn oxide to prevent oxygen vacancy, while the second layer (away from interface) uses Ga-containing oxide to reduce leakage current. This local quality approach optimizes both interface stability and overall electrical performance.
2Productivity
If degree of integration increases, then device density improves, but short channel effect increases leading to higher leakage current
Solution Approach 1:
The invention changes the compositional parameters of the oxide semiconductor layer by introducing multiple layers with varying metal element ratios. The first layer has specific In:Zn ratios optimized for interface stability, while the second layer has Ga content optimized for leakage current suppression. This parameter optimization enables high-density integration while maintaining reliable leakage current control.
Data Source
AI summary
Provided is a field effect transistor including a gate electrode layer, an oxide semiconductor layer including gallium (Ga) and at least one metal element selected from indium (In) and zinc (Zn), and a dielectric layer between the gate electrode layer and the oxide semiconductor layer, wherein the oxide semiconductor layer includes a sub semiconductor layer in contact with the dielectric layer and a main semiconductor layer spaced apart from the dielectric layer with the sub semiconductor layer therebetween, the sub semiconductor layer has a first Ga content, and the first Ga content of the sub semiconductor layer is greater than contents of other metal elements included in the sub semiconductor layer and decreases as a distance from an interface of the sub semiconductor layer in contact with the dielectric layer increases.