Thin Film Transistor Protrusions for Leakage Current Reduction
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Solution Overview
Problem
Active matrix liquid crystal display devices suffer from increased leakage current and image quality deterioration due to electron hole pairs generated by incident light, leading to brightness changes and vertical crosstalk, especially as backlight brightness increases.
Innovation Solution
A thin film transistor with a semiconductor layer formed using sequential lateral solidification (SLS) and featuring 3.5 to 4.5 protrusions on the semiconductor layer overlapped with the gate electrode, which helps minimize leakage current and maintain uniform electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional thin film transistor is used in an active matrix liquid crystal display device, then the device can display images with backlight illumination, but leakage current increases and image quality deteriorates due to electron hole pairs generated by incident light
Solution Approach 1:
The patent applies local quality by creating protrusions at specific locations on the semiconductor layer surface. These protrusions are positioned in the channel region where they can effectively modulate the electric field and reduce leakage current. The localized structural modification targets the specific problem area without affecting the entire transistor structure, thereby reducing leakage current while maintaining overall device performance under backlight illumination.
Solution Approach 2:
The patent changes physical parameters by controlling the height, width, and spacing of the protrusions on the semiconductor layer. By optimizing these geometric parameters, the electric field distribution in the channel region is modified to suppress carrier generation from incident light. The protrusion dimensions are specifically designed to achieve the desired reduction in leakage current while maintaining proper transistor switching characteristics.
2Object-generated harmful factors
If the number of protrusions on the semiconductor layer is increased to reduce leakage current, then leakage current decreases, but threshold voltage shifts to positive voltage and electrical property deteriorates
Solution Approach 1:
The patent optimizes parameters by precisely controlling the number of protrusions (3-5), their height (50-200 nm), width (20-100 nm), and spacing. This parameter optimization ensures that enough protrusions are present to reduce leakage current through electric field modulation, while the parameters are constrained to prevent excessive threshold voltage shift. The balanced parameter selection maintains proper transistor electrical characteristics including threshold voltage and on-current.
Solution Approach 2:
The patent applies partial action by using a limited number of protrusions (3-5) rather than covering the entire channel region. This partial modification is sufficient to reduce leakage current through the protrusions' electric field effect, while avoiding excessive modification that would cause significant threshold voltage shift and electrical property deterioration. The partial action achieves the necessary leakage reduction without over-correcting.
3Object-generated harmful factors
If the protrusions on the semiconductor layer are optimized to minimize leakage current, then leakage current and defects are reduced, but precise control of protrusion number and dimensions is required
Solution Approach 1:
The patent applies preliminary action by forming the protrusions on the semiconductor layer before fabricating the gate electrode and other transistor components. This sequencing allows the protrusions to be established as a fixed structural feature that guides subsequent processing steps. The protrusions are created through controlled oxidation or deposition processes that can be precisely managed, ensuring consistent number and dimensions before the more sensitive gate electrode formation occurs.
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 adjusted number of protrusions on the semiconductor layer reduces leakage current and defects, preventing malfunction and maintaining image quality by optimizing threshold voltage and electrical properties.
Implementation Method 1
a semiconductor layer crystallized by sequential lateral solidification (SLS) method
Implementation Method 2
solidifying the amorphous semiconductor layer
Data Source
AI summary
A thin film transistor, a manufacturing method thereof, and a display device having the same are disclosed. The thin film transistor includes a semiconductor layer formed on a substrate, a gate insulating layer formed on the substrate including the semiconductor layer, a gate electrode formed on the gate insulating above the semiconductor layer, source and drain electrodes connected to the semiconductor layer, and 3.5 to 4.5 protrusions formed on the semiconductor layer overlapped with the gate electrode. Malfunction of the thin film transistor and inferior image quality of the display device can be prevented by adjusting the number of protrusions to minimize leakage current and defects.