Oxide TFT Gate Insulator Segmentation for Breakdown Voltage
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Solution Overview
Problem
Thin film transistors (TFTs) face challenges with silicon oxide films used as gate insulating films, where a low proportion of silane gas can damage the channel region, reducing threshold voltage, while a high proportion decreases oxygen content, lowering insulation properties and breakdown voltage.
Innovation Solution
A thin film transistor design featuring an oxide semiconductor layer with a channel region, source, and drain regions of lower resistivity, a multi-layer gate insulating layer with a silicon oxide first layer and a silicon nitride second layer, and an aluminum oxide layer covering the gate insulating layer and source/drain regions, ensuring high breakdown voltage and preventing threshold voltage reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high proportion of silane gas is used during silicon oxide film formation, then the oxygen content in the gate insulating film increases, but the breakdown voltage decreases due to reduced insulation properties
Solution Approach 1:
The gate insulating film is segmented into multiple layers where the first silicon oxide layer (with higher oxygen content formed by low silane gas proportion) provides superior insulation properties and breakdown voltage, while the second silicon oxide layer (with lower oxygen content formed by high silane gas proportion) provides adequate insulation and compensates for any plasma damage to the channel region.
Solution Approach 2:
The gate insulating film is constructed as a composite structure combining two different silicon oxide layers with distinct properties. This composite material approach allows the system to simultaneously achieve high oxygen content and high breakdown voltage in the first layer while maintaining sufficient insulation in the second layer, resolving the contradiction between oxygen content and breakdown voltage.
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 provides a TFT with enhanced breakdown voltage and maintains threshold voltage stability by optimizing the gate insulating layer structure and using an aluminum oxide layer to manage resistivity and oxygen content.
Implementation Method 1
an aluminum oxide layer covering a lateral surface of the gate insulating layer, and the source region and the drain region
Implementation Method 2
The silicon oxide film is formed by plasma chemical vapor deposition (CVD) using silane gas (SiH4) and nitrous oxide gas (N2O) as introduced gases
Data Source
AI summary
A thin film transistor includes an oxide semiconductor layer including a channel region, and a source region and a drain region having a resistivity lower than that of the channel region; a gate insulating layer disposed on the channel region of the oxide semiconductor layer; a gate electrode disposed on the gate insulating layer; and an aluminum oxide layer covering the lateral surface of the gate insulating layer, and the source region and the drain region, wherein the gate insulating layer has a multi-layer structure including a first insulating layer and a second insulating layer, and the first insulating layer contains silicon oxide as a main component, and is disposed on and in contact with the channel region.