Transparent Gate TFT Substrate for Threshold Voltage Stability
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Solution Overview
Problem
Thin film transistors in display apparatuses experience reliability issues due to high positive bias, leading to charge buildup and threshold voltage drift, especially in buffer units and light emission control transistors, which can be exacerbated by the need for additional insulation layers that affect on-current characteristics and S-factor adjustment.
Innovation Solution
Incorporating a conductive transparent oxide semiconductor material in the gate electrode of thin film transistors and using a light shielding layer in certain configurations to prevent light from reaching the active layer, thereby improving reliability and eliminating the need for additional insulation layers between upper and lower transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional insulation layers are provided between upper and lower thin film transistors, then insulation and protection between transistors is improved, but the thickness of the transistor increases and on-current characteristics deteriorate
Solution Approach 1:
The gate electrode of the lower thin film transistor is made of transparent conductive oxide semiconductor material that provides both electrical conduction and insulation functions. This merges the gate electrode and insulation layer into a single component, eliminating the need for separate insulation layers while maintaining both electrical performance and insulating properties.
Solution Approach 2:
The patent changes the material parameter of the gate electrode from conventional metal to transparent conductive oxide semiconductor. This material parameter change enables the gate electrode to serve dual purposes: electrical conduction for transistor operation and optical transparency for light transmission, while also providing insulation to upper transistor layers.
2Reliability
If transparent conductive oxide semiconductor material is used in the gate electrode, then reliability under positive bias is improved and additional insulation layers are eliminated, but manufacturing complexity may increase
Solution Approach 1:
The transparent conductive oxide semiconductor gate electrode performs multiple functions simultaneously: it serves as the gate electrode for electrical control, provides insulation to the upper transistor, and allows light transmission. This multi-functionality reduces the total number of layers needed while improving reliability under positive bias conditions.
3Adaptability or versatility
If different types of thin film transistors are implemented on different layers, then device characteristics are optimized, but additional gate insulating layers are required which increase thickness and reduce on-current
Solution Approach 1:
The transparent conductive oxide semiconductor gate electrode of the lower transistor serves as both the gate electrode and the gate insulating layer for the upper transistor. This merging eliminates the need for additional insulation layers when stacking different transistor types, maintaining thin profile and excellent on-current characteristics while enabling diverse device configurations.
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 solution enhances the reliability of thin film transistors under positive bias conditions by reducing charge buildup and maintaining on-current characteristics, while allowing for easier S-factor adjustment without the need for additional insulation layers.
Implementation Method 1
the gate electrode is disposed on the active layer and includes transparent conductive oxide semiconductor material
Implementation Method 2
a second thin film transistor TR2 with an additional light shielding layer LS
Data Source
AI summary
A thin film transistor substrate can include a first thin film transistor disposed on a substrate, the first thin film transistor including a first source electrode, a first drain electrode, a first active layer and a first gate electrode, in which the first gate electrode is disposed on the first active layer and includes a transparent conductive oxide semiconductor material. Also, the first gate electrode can be transparent and can allow light to be irradiated onto the first active layer to release a buildup of charges from accumulating within the first active layer while the first thin film transistor is in operation in order to maintain a more constant threshold voltage.