Gate Insulating Layer Fluorine Concentration for Oxide Semiconductor Reliability
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Solution Overview
Problem
Transistors using oxide semiconductors face a challenge with a shift in threshold voltage, leading to a normally-on state even when no voltage is applied to the gate electrode, due to hydrogen diffusion from the gate insulating layer into the oxide semiconductor layer.
Innovation Solution
A gate insulating layer with low hydrogen content and high fluorine concentration is used to reduce hydrogen diffusion into the oxide semiconductor layer, employing materials like silicon oxide, silicon oxynitride, or hafnium oxide, and a two-layer structure to minimize hydrogen release and enhance fluorine presence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gate insulating layer is used, then the transistor can be manufactured with standard processes, but hydrogen diffuses into the oxide semiconductor layer causing threshold voltage shift and normally-on state
Solution Approach 1:
The patent changes the compositional parameters of the gate insulating layer by incorporating fluorine atoms at a concentration of 1×10^20 to 1×10^21 atoms/cm³. This parameter change modifies the chemical properties of the gate insulating layer to reduce hydrogen diffusion into the oxide semiconductor layer, thereby preventing threshold voltage shift and eliminating the normally-on state while maintaining standard manufacturing processes.
Solution Approach 2:
The patent uses a composite gate insulating layer structure that combines oxide insulating materials (such as silicon oxide, hafnium oxide, or aluminum oxide) with fluorine-containing compounds. This composite material approach creates a gate insulating layer that simultaneously provides good interface characteristics and reduced hydrogen diffusion, solving the reliability issue without requiring entirely new materials or processes.
2Manufacturing precision
If the gate insulating layer contains fluorine, then hydrogen content in the oxide semiconductor layer is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by forming the fluorine-containing gate insulating layer before depositing the oxide semiconductor layer. This sequence ensures that the fluorine is already present in the gate insulating layer to prevent hydrogen diffusion during subsequent processing steps, achieving precise hydrogen content control without requiring additional complex steps after semiconductor layer formation.
Solution Approach 2:
The patent specifies precise parameter ranges for fluorine concentration (1×10^20 to 1×10^21 atoms/cm³) and hydrogen concentration (less than 6×10^20 atoms/cm³) in the gate insulating layer. By controlling these parameters within defined ranges, the patent achieves effective hydrogen content control in the oxide semiconductor layer while maintaining manageable manufacturing complexity through quantifiable specifications.
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
This approach effectively reduces hydrogen content in the oxide semiconductor layer, preventing threshold voltage shifts and improving electrical characteristics of the transistor without increasing fabrication steps.
Implementation Method 1
hydrogen diffusion from the gate insulating layer into the oxide semiconductor layer
Implementation Method 2
hydrogen present in the oxide semiconductor layer can be eliminated
Data Source
AI summary
An object is to provide a semiconductor device having good electrical characteristics. A gate insulating layer having a hydrogen concentration less than 6×1020 atoms/cm3 and a fluorine concentration greater than or equal to 1×1020 atoms/cm3 is used as a gate insulating layer in contact with an oxide semiconductor layer forming a channel region, so that the amount of hydrogen released from the gate insulating layer can be reduced and diffusion of hydrogen into the oxide semiconductor layer can be prevented. Further, hydrogen present in the oxide semiconductor layer can be eliminated with the use of fluorine; thus, the hydrogen content in the oxide semiconductor layer can be reduced. Consequently, the semiconductor device having good electrical characteristics can be provided.