Stacked Oxide Semiconductor Transistor for High Mobility and Low Leakage
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Solution Overview
Problem
Transistors using oxide semiconductors face challenges in improving field-effect mobility and on-state current while maintaining stable electrical characteristics and reducing leakage current in the off-state.
Innovation Solution
A semiconductor device structure is developed with specific layers including a conductor, insulators, and metal oxides, where the oxide semiconductor has a higher indium content than other metals, and the energy levels of the metal oxides are aligned to facilitate better electron flow and reduce defects, enhancing field-effect mobility and on-state current while minimizing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the field-effect mobility of a transistor including an oxide semiconductor is improved and the on-state current is increased, then the transistor performance is enhanced, but leakage current in off state increases and electrical characteristics become unstable
Solution Approach 1:
The gate insulating film is divided into multiple layers with different functions: a first gate insulating film layer in contact with the oxide semiconductor layer provides interface quality and low leakage current, while a second gate insulating film layer provides high dielectric constant for strong electric field control. This segmentation allows each layer to optimize for its specific function, achieving both low leakage and high mobility.
Solution Approach 2:
The gate insulating film uses a composite structure combining materials with different properties: the first layer uses materials like In-Ga-Zn-O or In-Al-Zn-O with low leakage current characteristics, while the second layer uses high-k materials like hafnium oxide or silicon oxide for strong electric field control. This composite approach resolves the contradiction between low leakage and high mobility.
2Reliability
If the field-effect mobility of a transistor including an oxide semiconductor is improved and the on-state current is increased, then the transistor performance is enhanced, but electrical characteristics become unstable
Solution Approach 1:
The gate insulating film is segmented into functional layers: the first layer ensures stable electrical characteristics through low leakage current and good interface properties, while the second layer provides stable electric field control through high dielectric constant. This functional segmentation stabilizes overall transistor characteristics.
Solution Approach 2:
The invention changes the dielectric constant parameter of the gate insulating film by using a composite structure with high-k materials, which stabilizes the electric field distribution and improves the stability of electrical characteristics while maintaining high mobility.
Data Source
AI summary
The field-effect mobility of a semiconductor device is improved, and the on-state current thereof is increased, so that stable electrical characteristics are obtained. The semiconductor device includes a first oxide insulator, an oxide semiconductor, and a second oxide insulator which are stacked. The first oxide insulator includes In, Zn, and M (M represents Ti, Ga, Y, Zr, La, Ce, Nd, Sn, or Hf), and the content of In is lower than the content of M, and the content of In is lower than the content of Zn. The oxide semiconductor includes In and M (M represents Ti, Ga, Y, Zr, La, Ce, Nd, Sn, or Hf), and the content of In is higher than the content of M. The second oxide insulator includes In, Zn, and M (M represents Ti, Ga, Y, Zr, La, Ce, Nd, Sn, or Hf).