Silicon Nitride Dielectric Layer for Oxide TFT Reliability
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Solution Overview
Problem
Active matrix type liquid crystal display devices with oxide semiconductor TFTs face issues with air voids forming in the liquid crystal layer under high temperature and high humidity, leading to deteriorated display quality and reliability.
Innovation Solution
A semiconductor device structure featuring a substrate with an oxide semiconductor TFT, an organic insulating layer, a lower electrode, a silicon nitride dielectric layer with controlled hydrogen content (5.33×10^21 atoms/cm^3 or less) and relative dielectric constant (6.56 or less), and an upper electrode, formed using specific plasma CVD conditions to prevent air void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional dielectric layer is used in oxide semiconductor TFTs, then the device can be manufactured with standard processes, but air voids form in the liquid crystal layer under high temperature and high humidity conditions
Solution Approach 1:
The patent applies parameter changes by precisely controlling the hydrogen content in the silicon nitride dielectric layer to 5.33×10^21 atoms/cm³ or less and the relative dielectric constant to 6.56 or less. These specific parameter thresholds prevent air void formation while maintaining effective capacitance, directly resolving the reliability issue under high temperature and high humidity conditions.
Solution Approach 2:
The patent uses a silicon nitride-based dielectric layer with specifically controlled composition and properties. This composite material approach, combining silicon nitride with precise hydrogen content control, creates a dielectric layer that prevents air void formation while maintaining the necessary electrical characteristics for TFT operation.
2Reliability
If the dielectric layer hydrogen content is reduced to prevent air voids, then reliability improves, but the dielectric constant may decrease affecting capacitance
Solution Approach 1:
The patent simultaneously optimizes multiple parameters: hydrogen content (≤5.33×10^21 atoms/cm³) and relative dielectric constant (≤6.56). By controlling both parameters within specific ranges, the invention achieves the counterintuitive result of preventing air voids while maintaining sufficient capacitance for TFT operation.
Solution Approach 2:
The silicon nitride dielectric layer is engineered as a composite material with controlled composition. The specific hydrogen content and dielectric constant combination creates a material that balances air void prevention with adequate capacitance, resolving the trade-off between reliability and electrical performance.
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 suppresses air void formation and maintains the reliability of the semiconductor device under high temperature and high humidity conditions while preventing negative shifts in TFT characteristics.
Implementation Method 1
the dielectric layer is a silicon nitride film having a hydrogen content of 5.33×10^21 atoms/cm³ or less
Implementation Method 2
step (e) is a step of forming a silicon nitride film as the dielectric layer, and is performed under film formation conditions such that the silicon nitride film has a hydrogen content of 5.33×10^21 atoms/cm³ or less
Data Source
AI summary
A semiconductor device (100A) includes a substrate (11); a TFT (10A) supported on the substrate, the TFT including an oxide semiconductor layer (16); an organic insulating layer (24) covering the TFT; a lower layer electrode (32) on the organic insulating layer; a dielectric layer (34) on the lower layer electrode; an upper layer electrode on the dielectric layer; and an upper layer electrode (36) including a portion opposing the lower layer electrode via the dielectric layer. The dielectric layer is a silicon nitride film having a hydrogen content of 5.33×1021 atoms/cm3 or less.