Light Shielding Metal Layer in Thin Film Transistors
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Solution Overview
Problem
In AMOLED display pixel driving circuits, the lack of a light-shielding metal layer in thin film transistors T1 and T2 leads to threshold voltage drift under negative bias voltage, causing failure to turn off the transistors and resulting in flicker on the display panel due to ambient light illumination.
Innovation Solution
A display panel with a thin film transistor layer that includes a light shielding metal layer integrated in the buffer layer, electrically connected to the gate metal layer through via holes, which prevents external light from affecting carrier mobility and enhances gate control by increasing the gate metal area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a light shielding metal layer is not used in data writing thin film transistors, then the fabricating process is simpler, but the threshold voltage drifts under negative bias voltage due to ambient light illumination
Solution Approach 1:
The light shielding function is segmented from the gate structure and implemented as a separate light shielding metal layer positioned beneath the buffer layer, allowing the gate to focus on electrical control while the dedicated shielding layer handles optical protection
Solution Approach 2:
The buffer layer serves as an intermediary element that electrically connects the gate metal layer to the light shielding metal layer through via holes, enabling both electrical functionality and optical shielding without direct contact between gate and shielding layers
2Reliability
If the gate metal layer area is increased to improve gate control, then the gate control capability is enhanced, but the device area increases
Solution Approach 1:
The light shielding metal layer is positioned in a different spatial dimension (beneath the buffer layer) rather than expanding the gate metal area in the planar dimension, providing enhanced gate control through electrical connection without increasing the device footprint
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 stabilizes the data writing thin film transistors by shielding external light and improving gate control, preventing threshold voltage drift and ensuring proper data writing and display functionality.
Implementation Method 1
a light shielding metal layer, the light shielding metal layer is located on the substrate
Implementation Method 2
the gate metal layer is electrically connected to the light shielding metal layer through the first via hole
Data Source
AI summary
A display panel and a method of fabricating a thin film transistor. The display panel includes a plurality of data writing thin film transistors. Each of the data writing thin film transistors includes a substrate, a light shielding metal layer, a buffer layer, an active region, a gate dielectric layer, and a gate metal layer. The active region includes a channel region and a source region and a drain region on both sides of the channel region. The data writing thin film transistor further includes a first via hole penetrating the gate dielectric layer and the buffer layer, and the gate metal layer is electrically connected to the light shielding metal layer through the first via hole.