Semiconductor Device with Degenerate Oxide Buffer Layer
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Solution Overview
Problem
Existing semiconductor devices with thin film transistors face challenges in achieving high electric characteristics and long-term reliability due to issues like contact resistance, plasma damage, and sensitivity to moisture and hydrogen ions, particularly when using oxide semiconductor layers.
Innovation Solution
A semiconductor device is developed with a thin film transistor that includes an oxide semiconductor layer formed using silicon oxide, featuring a Zn—O-based or In—Ga—Zn—O-based oxide semiconductor, and utilizing a degenerate oxide semiconductor for source and drain regions to reduce contact resistance and enhance ohmic contact, along with protective insulating films to prevent plasma damage and moisture exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If oxide semiconductor layer is used in thin film transistor, then transparency and semiconductor characteristics are improved, but contact resistance increases and electric characteristics deteriorate
Solution Approach 1:
A buffer layer made of degenerate oxide semiconductor is introduced between the oxide semiconductor layer and the source/drain electrodes. This buffer layer serves as an intermediary that provides ohmic contact to the oxide semiconductor layer, reducing contact resistance while maintaining the transparency and semiconductor characteristics of the oxide semiconductor layer itself.
Solution Approach 2:
The carrier concentration of the oxide semiconductor is controlled to be in the range of 1×10^16 to 1×10^18 cm^-3, and the buffer layer is designed with higher carrier concentration (degenerate oxide semiconductor). By changing these electrical parameters, the contact resistance is reduced while maintaining the desired transparency and semiconductor characteristics.
2Manufacturing precision
If plasma processing is used in manufacturing, then manufacturing precision is improved, but plasma damage to oxide semiconductor layer increases
Solution Approach 1:
Protective insulating films are formed over the oxide semiconductor layer before plasma processing steps. These protective films act as a cushion or barrier that prevents plasma damage to the oxide semiconductor layer during manufacturing processes, while still allowing plasma processing to be performed for pattern formation in other layers.
3Ease of manufacture
If oxide semiconductor layer is exposed to environment, then manufacturing simplicity is improved, but sensitivity to moisture and hydrogen ions increases
Solution Approach 1:
Protective insulating films are formed over the oxide semiconductor layer to create a protective shell that isolates the oxide semiconductor from environmental factors such as moisture and hydrogen ions. This allows the device to be manufactured with relatively simple processes while ensuring long-term stability against environmental degradation.
4Device complexity
If conventional source and drain electrodes are used directly on oxide semiconductor layer, then device complexity is reduced, but contact resistance increases
Solution Approach 1:
A buffer layer of degenerate oxide semiconductor is inserted between the source/drain electrodes and the oxide semiconductor layer. This intermediary layer provides ohmic contact, reducing contact resistance without significantly increasing device complexity, as the buffer layer can be formed using the same sputtering process with adjusted parameters.
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 results in a semiconductor device with improved electric characteristics and long-term reliability, achieving high field effect mobility and stability against environmental factors.
Implementation Method 1
an oxide semiconductor layer including silicon oxide is formed by a sputtering method using a first oxide semiconductor target including silicon oxide
Data Source
AI summary
An object of an embodiment of the present invention is to provide a semiconductor device provided with a thin film transistor which includes an oxide semiconductor layer and has high electric characteristics. The semiconductor device includes a gate electrode over an insulating surface, an oxide semiconductor layer including silicon oxide, an insulating layer between the gate electrode and the oxide semiconductor layer, and source and drain regions between the oxide semiconductor layer including silicon oxide and source and drain electrode layers. The source and drain regions are formed using a degenerate oxide semiconductor material or a degenerate oxynitride material.