Dual Gate Insulator Transistor for Threshold Voltage Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Thin film transistors used in display devices experience threshold voltage instability due to leakage currents and charge trapping, leading to image quality degradation and reduced device lifetime.
Innovation Solution
A transistor structure comprising two field effect transistors connected in series, with different gate insulating films to manage leakage currents and electric field characteristics, where one FET generates a larger leakage current to stabilize the threshold voltage and the other compensates for off-current increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single gate insulating film is used in a thin film transistor, then the device structure is simple and easy to manufacture, but the threshold voltage becomes unstable due to charge trapping and leakage currents
Solution Approach 1:
The gate insulating film is divided into two separate layers: a first gate insulating film deposited at a lower temperature (e.g., 200-400°C) and a second gate insulating film deposited at a higher temperature (e.g., 400-600°C). This segmentation allows each layer to perform different functions - the first layer provides good interface characteristics with the semiconductor layer, while the second layer provides superior insulation properties, thereby resolving the threshold voltage instability issue without requiring a completely new transistor structure.
Solution Approach 2:
The gate insulating film is formed as a composite structure combining two different insulating materials or the same material deposited under different conditions. This composite approach leverages the advantages of both deposition temperatures - the lower temperature deposit provides good adhesion and interface quality, while the higher temperature deposit provides lower leakage current and better insulation, achieving stable threshold voltage through material composition rather than structural complexity.
2Strength
If the gate insulating film is deposited at a lower temperature to preserve the semiconductor layer, then the semiconductor layer integrity is maintained, but the gate insulating film has higher leakage current
Solution Approach 1:
The gate insulating film formation process is segmented into two stages with different deposition temperatures. The first stage uses lower temperature deposition to maintain semiconductor layer integrity and avoid damage, while the second stage uses higher temperature deposition to create a layer with superior insulation properties and lower leakage current. This temporal and functional segmentation resolves the contradiction between preserving the semiconductor layer and reducing leakage current.
Solution Approach 2:
A composite gate insulating film structure is created where the first layer (deposited at lower temperature) protects the semiconductor layer from thermal damage, while the second layer (deposited at higher temperature) provides the low-leakage insulation function. The composite material approach allows each layer to optimize for its specific function, with the lower temperature layer preserving semiconductor integrity and the higher temperature layer minimizing leakage current.
3Object-generated harmful factors
If a thicker gate insulating film is used to reduce leakage current, then the insulation property improves, but the gate electric field strength decreases and threshold voltage control becomes difficult
Solution Approach 1:
The gate insulating film is formed as a composite structure with two layers having different thicknesses and deposition conditions. The first layer (thinner, lower temperature) maintains good interface characteristics and allows sufficient gate electric field penetration for effective threshold voltage control, while the second layer (thicker, higher temperature) provides the primary insulation barrier to reduce leakage current. This composite approach distributes the functional requirements across two layers, resolving the contradiction between leakage reduction and field strength maintenance.
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 reduces threshold voltage instability and off-current levels, enhancing the image quality and lifespan of display devices by using a combination of gate insulating films with varying properties to control charge trapping.
Implementation Method 1
The first and second gate insulating films have one of different leakage current characteristics and gate electric field characteristics
Implementation Method 2
a dielectric constant of the first gate insulating film may be lower than a dielectric constant of the second gate insulating film
Implementation Method 3
under a negative gate voltage, holes having positive charges may move toward a gate insulating film due to an electric field of a gate electrode and may be trapped near an insulating film interface
Implementation Method 4
a porosity of the first gate insulating film may be higher porosity than a porosity of the second gate insulating film
Data Source
AI summary
Example embodiments relate to a transistor, a method of manufacturing a transistor, and/or an electronic device including the transistor. In example embodiments, the transistor includes a first field effect transistor (FET) and a second FET connected in series to each other, wherein a first gate insulating film of the first FET and a second gate insulating film of the second FET have different leakage current characteristics or gate electric field characteristics.