Dual-Gate Transistor Back-Channel Stabilization for Narrow Frame Width
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Solution Overview
Problem
Semiconductor display devices face challenges in reducing power consumption while maintaining image quality and achieving a narrower frame width, particularly due to issues with transistor threshold voltage stability and capacitance in driver circuits.
Innovation Solution
Incorporating a capacitor with a metal oxide film and a nitride insulating film in the pixel, along with a gate electrode on the back channel region to prevent charge generation and shift in threshold voltage, and using a pair of gate electrodes electrically connected to each other to enhance channel formation and reduce transistor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the aperture ratio is increased to reduce power consumption, then light transmission efficiency is improved, but the size of semiconductor elements must be reduced which complicates the design
Solution Approach 1:
The invention introduces a dual-gate transistor structure where a second gate electrode is added on the back channel region side, creating a three-dimensional gate control architecture. This dimensional expansion allows independent control of channel formation from both front and back, enabling reduced transistor footprint while maintaining electrical performance characteristics
Solution Approach 2:
The transistor channel control is segmented into two independent gate regions: a front gate for primary control and a back gate for threshold voltage stabilization. This segmentation allows each gate to be optimized for its specific function, enabling smaller overall device size while maintaining reliability
2Quantity of substance
If a resin film is removed to increase capacitance, then the required capacitance for high image quality can be secured, but positive fixed charge generation from moisture causes threshold voltage shift
Solution Approach 1:
The back gate electrode is positioned and configured to preemptively counteract the harmful effects of positive fixed charges generated by moisture penetration. By establishing a compensating electric field from the back gate, the threshold voltage shift caused by moisture-induced charges is prevented before it can degrade device performance
Solution Approach 2:
The invention changes the electrical parameters of the transistor by introducing dual gate control, allowing the threshold voltage to be dynamically adjusted and stabilized despite the presence of fixed charges. This parameter control enables high capacitance values without sacrificing reliability
3Ease of manufacture
If unipolar transistors are used in driver circuits to reduce manufacturing cost, then production expense is reduced, but threshold voltage deterioration occurs in sequential circuits
Solution Approach 1:
By adding the back gate dimension to the transistor structure, the invention enables unipolar transistors to achieve bipolar-like threshold voltage stability. The dual-gate configuration allows independent optimization of both manufacturing simplicity and electrical reliability
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 reduces power consumption, improves image quality, and achieves a smaller driver circuit area by stabilizing threshold voltage and increasing drain current, thereby enabling a narrower frame width and higher reliability.
Implementation Method 1
The capacitor includes at least a metal oxide film that has conductivity and transmits visible light
Implementation Method 2
a nitride insulating film between the metal oxide film and the pixel electrode
Implementation Method 3
A capacitor with small capacitance has disadvantages such as difficulty in controlling the alignment of liquid crystal molecules without decreasing driving frequency and a short period for holding a potential of an image signal
Data Source
AI summary
The following semiconductor device provides high reliability and a narrower frame width. The semiconductor device includes a driver circuit and a pixel portion. The driver circuit has a first transistor including a first gate and a second gate electrically connected to each other with a semiconductor film sandwiched therebetween, and a second transistor electrically connected to the first transistor. The pixel portion includes a third transistor, a liquid crystal element, and a capacitor. The liquid crystal element includes a first transparent conductive film electrically connected to the third transistor, a second conductive film, and a liquid crystal layer. The capacitor includes the first conductive film, a third transparent conductive film, and a nitride insulating film. The nitride insulating film is positioned between the first transparent conductive film and the third transparent conductive film, and positioned between the semiconductor film and the second gate of the first transistor.