Oxide Semiconductor Transistor Ring Gate Parasitic Channel Suppression
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Solution Overview
Problem
Oxygen vacancies in oxide semiconductor layers lead to the formation of parasitic channels, causing leakage currents, increased power consumption, and degradation in electric characteristics of transistors, making it difficult to control switching and maintain reliable semiconductor devices.
Innovation Solution
A transistor design where the outer edge of the oxide semiconductor layer is covered by one of the source or drain electrodes, and a ring-shaped gate electrode is formed over the oxide semiconductor layer with a gate insulating layer in between, preventing oxygen release and parasitic channel formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the oxide semiconductor layer is processed into an island shape for forming a transistor, then the transistor structure is formed, but oxygen is easily released from the end portion, creating oxygen vacancies that form parasitic channels
Solution Approach 1:
The patent applies local quality by covering only the end portions of the oxide semiconductor layer with insulating films, while the central channel-forming region remains exposed. This selective coverage prevents oxygen release at vulnerable end portions without affecting the electrical characteristics of the main channel region, thus suppressing parasitic channels while maintaining transistor functionality.
Solution Approach 2:
The patent applies preliminary action by forming insulating films over the end portions of the oxide semiconductor layer before completing the transistor fabrication process. This preemptive protection prevents oxygen release and parasitic channel formation during subsequent processing steps, addressing the problem before it occurs.
2Ease of manufacture
If etching gas is used in the step of forming the island-shaped oxide semiconductor layer, then the layer is shaped correctly, but etching gas components enter the end portion and become donors, forming low-resistance regions
Solution Approach 1:
The patent applies local quality by selectively covering only the end portions of the oxide semiconductor layer with insulating films, while the central channel-forming region remains exposed. This selective coverage prevents oxygen release at vulnerable end portions without affecting the electrical characteristics of the main channel region, thus suppressing parasitic channels while maintaining transistor functionality.
Solution Approach 2:
The patent introduces insulating films as intermediary layers between the oxide semiconductor layer and the external environment. These insulating films act as barriers that prevent etching gas components from entering and contaminating the end portions of the oxide semiconductor layer, thus preventing unwanted doping and resistance changes.
3Ease of operation
If the outer edge of the oxide semiconductor layer is exposed, then the transistor channel region is accessible, but oxygen release creates oxygen vacancies that increase off-state current
Solution Approach 1:
The patent applies local quality by selectively covering only the end portions of the oxide semiconductor layer with insulating films, while the central channel-forming region remains exposed. This selective coverage prevents oxygen release at vulnerable end portions without affecting the electrical characteristics of the main channel region, thus suppressing parasitic channels while maintaining transistor functionality.
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 design effectively suppresses parasitic channel generation, improves switching control, and enhances the electric characteristics of the transistor, leading to a more reliable semiconductor device with reduced power consumption.
Implementation Method 1
a channel (also referred to as a first channel) formed in a region of an oxide semiconductor layer, which overlaps with a gate
Implementation Method 2
an oxygen vacancy in an oxide semiconductor becomes a donor
Data Source
AI summary
A transistor including an oxide semiconductor and having favorable operation characteristics is provided. Further, by using the transistor, a semiconductor having improved operation characteristics can be provided. In planar view, one of a source electrode and a drain electrode of the transistor is surrounded by a ring-shaped gate electrode. Further, in planar view, one of the source electrode and the drain electrode of the transistor is surrounded by a channel formation region. Accordingly, the source electrode is not electrically connected to the drain electrode through a parasitic channel generated in an end portion of an island-shaped oxide semiconductor layer.