Oxide Semiconductor Thin Film Transistor Threshold Voltage Stabilization
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Solution Overview
Problem
Thin film transistors using oxide semiconductor layers often experience shifts in threshold voltage during manufacturing, leading to increased power consumption and reduced reliability due to plasma damage and moisture exposure, which affects the stability and performance of semiconductor devices.
Innovation Solution
A semiconductor device structure is implemented with a dual gate electrode configuration and a buffer layer to control threshold voltage, combined with protective insulating films and a resin layer to reduce plasma damage and moisture exposure, ensuring stable electric characteristics and long-term reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxide semiconductor layers are used in thin film transistors, then the transistors can be manufactured with standard processes, but the threshold voltage shifts during manufacturing due to plasma damage and moisture exposure
Solution Approach 1:
A nitrogen-containing insulating layer is introduced as an intermediary between the oxide semiconductor layer and the gate electrode. This intermediary layer prevents plasma damage and moisture exposure to the oxide semiconductor layer while allowing the transistor to be manufactured using standard processes, thus resolving the contradiction between ease of manufacture and threshold voltage stability.
Solution Approach 2:
The nitrogen-containing insulating layer creates an inert environment that protects the oxide semiconductor layer from plasma damage and moisture exposure during manufacturing and operation. This inert atmosphere prevents threshold voltage shifts while maintaining compatibility with standard manufacturing processes.
2Reliability
If protective measures are taken to prevent plasma damage and moisture exposure, then threshold voltage stability improves, but device complexity increases
Solution Approach 1:
The nitrogen-containing insulating layer serves multiple functions simultaneously: it acts as a gate insulating layer, a protective barrier against plasma damage, and a moisture barrier. This multi-functionality provides comprehensive protection for threshold voltage stability without significantly increasing device complexity.
Solution Approach 2:
The gate insulating layer is formed as a composite structure combining a nitrogen-containing insulating layer with other insulating materials. This composite structure provides enhanced protection against plasma damage and moisture exposure while maintaining reasonable device complexity through integrated design.
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 solution effectively stabilizes the threshold voltage, reduces power consumption, and enhances the reliability of thin film transistors by minimizing plasma damage and moisture exposure, resulting in improved performance and longevity of semiconductor devices.
Implementation Method 1
plasma damage and moisture exposure, which affects the stability and performance of semiconductor devices
Implementation Method 2
plasma damage and moisture exposure, which affects the stability and performance of semiconductor devices
Implementation Method 3
A gate electrode under the oxide semiconductor layer (which can be referred to as a first gate electrode) has the same potential as a gate wiring, while a gate electrode over the oxide semiconductor layer (which can be referred to as a second gate electrode or a back gate electrode) has a potential equal to or lower than a source potential of the thin film transistor
Data Source
AI summary
The threshold voltage is shifted in a negative or positive direction in some cases by an unspecified factor in a manufacturing process of the thin film transistor. If the amount of shift from 0 V is large, driving voltage is increased, which results in an increase in power consumption of a semiconductor device. Thus, a resin layer having good flatness is formed as a first protective insulating film covering the oxide semiconductor layer, and then a second protective insulating film is formed by a sputtering method or a plasma CVD method under a low power condition over the resin layer. Further, in order to adjust the threshold voltage to a desired value, gate electrodes are provided over and below an oxide semiconductor layer.