Thin Film Transistor Gate Insulator Stacked Structure
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Solution Overview
Problem
The fabrication process of thin film transistor substrates often introduces defects due to the deposition of silicon dioxide, leading to poor reliability and characteristics of the thin film transistor substrate, particularly due to bias voltage issues.
Innovation Solution
A thin film transistor substrate is fabricated with a gate insulating layer comprising a stacked structure of silicon oxide and silicon nitride layers, where the silicon nitride layer diffuses hydrogen ions to reduce electron trapping and improve field effect mobility, and the substrate includes a light shielding layer, active layer, conductor layers, interlayer insulating layer, and passivation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon dioxide is deposited as a gate insulating layer, then the fabrication process is simple, but defects are introduced leading to poor reliability
Solution Approach 1:
The patent applies composite materials by combining silicon oxide and silicon nitride in a stacked gate insulating layer structure. The silicon oxide layer provides good interface characteristics with the active layer, while the silicon nitride layer provides high dielectric constant and hydrogen ion diffusion capability to passivate defects. This composite structure resolves the contradiction by maintaining fabrication simplicity while significantly improving reliability through the synergistic effects of the two materials.
Solution Approach 2:
The patent changes the parameters of the gate insulating layer by transitioning from a single-layer silicon oxide structure to a stacked structure with specific thickness ratios (silicon oxide layer thickness ≥ silicon nitride layer thickness). This parameter change enables the system to achieve both ease of manufacture and improved reliability by optimizing the structural configuration rather than changing the fundamental fabrication approach.
2Device complexity
If a single-layer silicon oxide gate insulating layer is used, then the device structure is simple, but field effect mobility is poor due to electron trapping
Solution Approach 1:
The patent uses composite materials (silicon oxide + silicon nitride) in the gate insulating layer to simultaneously achieve simple device structure and high field effect mobility. The silicon nitride layer's high dielectric constant reduces the thickness needed for equivalent capacitance, while its hydrogen ion diffusion passivates interface traps, thereby improving electron mobility without significantly increasing structural complexity.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different layers: the silicon oxide layer provides excellent interface quality with the active layer, while the silicon nitride layer provides defect passivation through hydrogen ion diffusion. This localized functional differentiation resolves the contradiction between structural simplicity and performance by optimizing each layer's specific contribution.
3Productivity
If bias voltage is applied during silicon dioxide deposition, then the deposition process is completed, but defect states are introduced affecting substrate characteristics
Solution Approach 1:
The patent converts the harmful effect of bias voltage-induced defects into a benefit by using the silicon nitride layer's hydrogen ion diffusion capability to passivate these defect states. The hydrogen ions from the silicon nitride layer migrate to and neutralize the positive charge traps created during biased deposition, thereby transforming the harmful defect states into a controlled passivation mechanism that improves overall device reliability.
Solution Approach 2:
The silicon nitride layer acts as an intermediary between the silicon oxide deposition process and the final device characteristics. It mediates the harmful effects of bias voltage by providing hydrogen ions that passivate defect states, thereby protecting the overall device performance while allowing the deposition process to proceed efficiently.
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 two-layer gate insulating structure enhances the reliability and field effect mobility of the thin film transistor substrate by reducing the influence of bias stress and improving electron trapping, thereby addressing the reliability issues associated with defect states.
Implementation Method 1
the silicon nitride layer diffuses hydrogen ions to reduce electron trapping and improve field effect mobility
Data Source
AI summary
A thin film transistor substrate and a method of fabricating same are provided.The thin film transistor substrate includes a substrate, a light shielding layer disposed on the substrate, a buffer layer disposed on the light shielding layer, an active layer disposed on the buffer layer, and a gate insulating layer disposed on the active layer. The gate insulating layer includes a stacked structure including a first insulating layer and a second insulating layer.