Oxide Semiconductor Thin Film Transistor Channel Protective Layer Density Gradient
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Solution Overview
Problem
The formation of thick high-density silicon oxide films in oxide semiconductor thin film transistors leads to increased film stress, resulting in film peeling and reduced reliability, and the use of different materials for channel protective layers increases manufacturing time and costs.
Innovation Solution
The channel protective layers are formed with different film densities, where the portion in contact with the oxide semiconductor layer has a higher film density than the portion distant from it, using silicon oxide films with specific density ranges to alleviate stress and prevent peeling, while using the same material for both layers to reduce manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick high-density silicon oxide films are used for channel protective layers, then passivation performance is improved, but film stress increases causing film peeling and reduced reliability
Solution Approach 1:
The channel protective layer is divided into two separate layers: a first channel protective layer with high film density (2.5-2.7 g/cm³) for excellent passivation performance, and a second channel protective layer with low film density (2.0-2.3 g/cm³) for low stress. This segmentation allows each layer to fulfill its specific function without compromising the other, preventing film peeling while maintaining high passivation performance.
Solution Approach 2:
Different regions of the channel protective layer structure are assigned different film densities based on their functional requirements. The first channel protective layer in contact with the oxide semiconductor layer uses high density for superior passivation, while the second layer uses low density for stress relief. This local differentiation of material properties optimizes both reliability and stress resistance.
2Reliability
If different materials are used for first and second channel protective layers, then passivation performance is improved, but manufacturing time and costs increase
Solution Approach 1:
Instead of changing material composition, the invention changes the physical parameter of film density while keeping the material composition identical (both layers are silicon oxide). This is achieved by controlling deposition conditions such as oxygen flow rate, pressure, and power during sputtering, allowing the formation of layers with different densities from the same material, thus simplifying manufacturing while maintaining performance.
Solution Approach 2:
Both channel protective layers are formed from the same material (silicon oxide), ensuring material homogeneity throughout the structure. This eliminates the complexity of handling multiple materials while still achieving different film densities through controlled deposition parameters, thereby improving manufacturing efficiency without sacrificing passivation 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
This configuration effectively prevents film peeling and enhances the reliability of oxide semiconductor thin film transistors by managing film stress and simplifying the manufacturing process, while maintaining high passivation performance.
Implementation Method 1
for example, in a case where two channel protective layers are formed using a sputtering method
Implementation Method 2
in a case where channel protective layers are formed using a Chemical Vapor Deposition (CVD) method
Data Source
AI summary
A thin film transistor includes, an insulating substrate, a gate electrode provided on an upper surface of the insulating substrate, a gate insulating film formed so as to cover the gate electrode, an oxide semiconductor layer provided on the gate insulating film, a channel protective layer provided at least on an upper surface of the oxide semiconductor layer, and a source electrode and a drain electrode provided so as to come into contact with the oxide semiconductor layer, wherein the channel protective layer is formed such that the film density of a portion provided so as to come into contact with the oxide semiconductor layer is higher than the film density of a portion distant from the oxide semiconductor layer.