Fluorinated Oxide Semiconductor Channel for Stable Normally-Off Transistors
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Solution Overview
Problem
Transistors using oxide semiconductors face challenges in achieving stable electrical characteristics due to oxygen vacancies, which affect reliability and performance, particularly in high-frequency applications.
Innovation Solution
Incorporating fluorine into the channel formation region of oxide semiconductors to fill oxygen vacancies and form stable bonds, thereby enhancing electrical stability and reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxide semiconductors are used to form transistors, then high field-effect mobility and low power consumption are achieved, but oxygen vacancies cause unstable electrical characteristics and reduced reliability
Solution Approach 1:
The patent converts the harmful effect of oxygen vacancies into a beneficial process by intentionally creating oxygen-deficient regions that serve as oxygen sources. These regions subsequently release oxygen to fill vacancies in the channel formation region, transforming the harmful vacancy formation mechanism into a self-healing oxygen supply system that stabilizes electrical characteristics
Solution Approach 2:
The patent changes the oxygen concentration parameter within the oxide semiconductor structure by creating regions with different oxygen content. Specifically, it forms oxygen-excess regions adjacent to oxygen-deficient channel regions, thereby controlling the oxygen chemical potential gradient to drive oxygen diffusion and fill vacancies, improving electrical stability without compromising mobility
2Reliability
If high-temperature heat treatment or laser light treatment is applied to amorphous silicon to form polycrystalline silicon, then high field-effect mobility is achieved, but the manufacturing process becomes complex and capital investment increases
Solution Approach 1:
The patent changes the material composition parameter by incorporating fluorine into the oxide semiconductor structure. This compositional modification enables the material to achieve high field-effect mobility through chemical bonding mechanisms rather than requiring high-temperature crystallization processes, thereby simplifying manufacturing while maintaining performance
Solution Approach 2:
The patent creates a composite oxide semiconductor structure containing multiple elements (In, Ga, Zn, and F) with distinct functional regions. This composite structure achieves high mobility through the inherent properties of the fluorinated oxide material system, eliminating the need for complex phase transformation processes required by single-material approaches
3Reliability
If fluorine is incorporated into the channel formation region, then oxygen vacancies are filled and electrical stability is improved, but the manufacturing process requires additional steps
Solution Approach 1:
The patent performs preliminary action by forming fluorinated oxide semiconductor layers and oxygen reservoir regions during the initial material deposition phase. This advance preparation of oxygen supply structures eliminates the need for subsequent oxygen introduction steps, as the oxygen is already positioned within the structure to self-correct vacancies during device operation
Solution Approach 2:
The patent implements self-service by designing the oxide semiconductor structure to autonomously supply oxygen to fill vacancies. The oxygen-excess regions act as self-regulating reservoirs that release oxygen when vacancies are detected in the channel region, eliminating the need for external oxygen introduction equipment or additional processing steps
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 transistors with improved stability, reduced leakage current, and enhanced high-frequency characteristics, ensuring reliable and efficient operation.
Implementation Method 1
adding fluorine to the oxide semiconductor
Data Source
AI summary
A semiconductor device with stable electrical characteristics is provided. Alternatively, a semiconductor device having normally-off electrical characteristics is provided. A semiconductor device includes a gate electrode, a gate insulator, and an oxide semiconductor, the oxide semiconductor contains fluorine in a channel formation region, and a fluorine concentration in the channel formation region is higher than or equal to 1×1020 atoms/cm3 and lower than or equal to 1×1022 atoms/cm3. Note that fluorine is added by an ion implantation method.