Oxide Semiconductor Transistor Hydrogen Barrier
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Solution Overview
Problem
Conventional oxide semiconductors used in display apparatuses face degradation due to hydrogen diffusion in insulating layers, leading to unstable long-term operation and image defects, especially when used in active matrix driving systems.
Innovation Solution
A field effect transistor with an active layer made of amorphous In-Ga-Zn-O and insulating layers with controlled hydrogen content less than 3 × 10^21 atoms/cm^3, formed using sputtering or low-temperature plasma CVD, to maintain high mobility and stability, and a display apparatus configuration that includes these transistors to prevent hydrogen diffusion and maintain image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous silicon or polysilicon is used as the active layer of a driving transistor, then the device can be manufactured with conventional processes, but hydrogen diffusion in insulating layers causes degradation of transistor characteristics during long-term operation
Solution Approach 1:
The patent changes the material parameter of the active layer from conventional amorphous silicon or polysilicon to oxide semiconductor (such as IGZO - indium gallium zinc oxide). This material substitution fundamentally alters the interaction between the active layer and hydrogen in insulating layers, as oxide semiconductors are less susceptible to hydrogen-induced degradation, thereby resolving the reliability issue during long-term operation
Solution Approach 2:
The patent employs a composite structure combining oxide semiconductor active layer with specifically designed insulating layers (such as silicon nitride or silicon oxynitride). This composite material approach creates a system where the insulating layers are engineered to minimize hydrogen outgassing and diffusion, while the oxide semiconductor layer provides inherent resistance to hydrogen damage, achieving stable long-term operation
2Speed
If oxide semiconductor is used as the active layer, then high electron mobility and excellent transistor characteristics are achieved, but degradation occurs during long-term active matrix driving due to unknown mechanisms related to insulating layer formation
Solution Approach 1:
The patent optimizes the composition parameters of the oxide semiconductor (such as In:Ga:Zn ratios in IGZO) and the insulating layer materials to achieve a balance between high electron mobility and long-term stability. By carefully controlling the stoichiometry and purity of the oxide semiconductor, high mobility is maintained while reducing susceptibility to degradation mechanisms
Solution Approach 2:
The patent introduces specifically engineered insulating layers (such as silicon nitride or silicon oxynitride) as intermediary layers between the oxide semiconductor active layer and other device components. These intermediary layers act as hydrogen barriers and protective interfaces, preventing harmful interactions while allowing the oxide semiconductor to maintain its high mobility characteristics during long-term operation
3Ease of manufacture
If conventional insulating layers with high hydrogen content are used, then easy manufacturing is achieved, but hydrogen diffusion into the active layer causes image defects and reduces display quality
Solution Approach 1:
The patent changes the material composition of insulating layers from conventional high-hydrogen materials to low-hydrogen-content materials (such as silicon nitride or silicon oxynitride). This parameter change in material composition significantly reduces the hydrogen reservoir available for diffusion into the active layer, thereby preventing image defects while maintaining manufacturability through established deposition techniques
Solution Approach 2:
The patent employs a multi-layer insulating structure comprising different materials (such as combinations of silicon oxide, silicon nitride, and silicon oxynitride) with complementary properties. This composite insulating system provides both ease of manufacture through standard processes and precise control over hydrogen content, as each layer can be optimized for specific functions including hydrogen barrier properties
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 enables a display apparatus that maintains high definition and stability over long periods without image defects, ensuring the oxide semiconductor's high mobility and characteristics are preserved, even under repetitive long-term light emission tests.
Implementation Method 1
formed using sputtering or low-temperature plasma CVD
Implementation Method 2
formed using sputtering or low-temperature plasma CVD
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A field effect transistor comprises a gate electrode (406), an oxide semiconductor layer (409), a source electrode (410), a drain electrode (410), and an insulating layer (408 and/or 412) being in contact with the oxide semiconductor layer, wherein the insulating layer has a hydrogen content of less than 3 × 1021 atoms/cm3. Such transistor may be used in a circuit board comprising a substrate (400), a wiring (401, 402, 403) and transistors electrically connected to the wirings. Such transistor may also be used in a display apparatus with a plurality of pixels, comprising a transistor (55 and/or 56) provided for each of the plurality of pixels, and wirings electrically connected to each of the plurality of transistors. A method of producing a field effect transistor comprising the steps of: forming a layer including a metal on a substrate (400); pattering the layer including the metal; forming a first insulating layer (408) on the patterned layer (406) including the metal; forming an oxide semiconductor layer (409) in contact with the first insulating layer; patterning the oxide semiconductor layer; forming an electrode layer (i.e., layer which becomes 410) on the patterned oxide semiconductor layer including the metal; and pattering the electrode layer; wherein the first insulating layer is formed so as to have a hydrogen content of less than 3 × 1021 atoms/cm3.