Oxide Semiconductor Stability via Silicon Oxide Barrier
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Solution Overview
Problem
The stability of electric characteristics in thin film transistors using oxide semiconductors is compromised by hydrogen and moisture, leading to variations in device performance due to the formation of oxygen-hydrogen bonds, which affect the conductivity and reliability of the devices.
Innovation Solution
A silicon oxide layer with defects is formed in contact with the oxide semiconductor layer to diffuse and stabilize hydrogen and moisture, reducing impurity concentrations by using a treatment chamber with a reduced pressure and a cryopump to remove residual moisture, and heating the substrate to diffuse impurities into the silicon oxide layer, thereby stabilizing the oxide semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin film transistor is manufactured using an oxide semiconductor layer, then the device can be formed with semiconductor characteristics, but hydrogen and moisture enter the oxide semiconductor during thin film formation and form oxygen-hydrogen bonds that cause variation in electric characteristics
Solution Approach 1:
A silicon oxide layer is formed in advance over the oxide semiconductor layer before subsequent processing steps. This preliminary layer acts as a barrier to prevent hydrogen and moisture from entering the oxide semiconductor during later manufacturing processes, thereby maintaining stable electric characteristics.
Solution Approach 2:
The silicon oxide layer serves as an intermediary barrier between the external environment (source of hydrogen and moisture) and the oxide semiconductor layer. This intermediate layer absorbs or blocks harmful contaminants, protecting the underlying semiconductor material from contamination.
2Productivity
If the oxide semiconductor layer is formed by conventional thin film formation methods, then the device can be manufactured, but the concentration of hydrogen in the oxide semiconductor layer becomes uncontrolled leading to variation in conductivity
Solution Approach 1:
The silicon oxide layer is deposited beforehand to establish a protective barrier before the oxide semiconductor layer is formed or processed. This preliminary structure prevents hydrogen ingress during subsequent manufacturing steps, enabling precise control of hydrogen concentration while maintaining production capability.
Solution Approach 2:
The silicon oxide layer creates an inert protective environment over the oxide semiconductor, isolating it from sources of hydrogen and moisture. This inert barrier allows the semiconductor to be manufactured using conventional techniques while maintaining precise control over impurity concentrations.
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 a semiconductor device with stable electric characteristics by reducing hydrogen and moisture concentrations in the oxide semiconductor layer, enhancing the reliability and consistency of thin film transistors.
Implementation Method 1
impurities such as hydrogen or moisture (a hydrogen atom or a compound including a hydrogen atom such as H2O) included in the oxide semiconductor layer are diffused into the silicon oxide layer
Implementation Method 2
the impurity concentration in the oxide semiconductor layer may be reduced in the following manner: a silicon oxide layer (SiOx, x is preferably 2 or larger) including many defects which are typified by dangling bonds is formed in contact with the oxide semiconductor layer
Data Source
AI summary
An object is to provide a semiconductor device with stable electric characteristics in which an oxide semiconductor is used. The impurity concentration in the oxide semiconductor layer is reduced in the following manner: a silicon oxide layer including many defects typified by dangling bonds is formed in contact with the oxide semiconductor layer, and an impurity such as hydrogen or moisture (a hydrogen atom or a compound including a hydrogen atom such as H2O) included in the oxide semiconductor layer is diffused into the silicon oxide layer. Further, a mixed region is provided between the oxide semiconductor layer and the silicon oxide layer. The mixed region includes oxygen, silicon, and at least one kind of metal element that is included in the oxide semiconductor.