Array Substrate Laser Crystallization for TFT Mobility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing array substrates for display devices face challenges with amorphous silicon thin film transistors, which have low stability and mobility, and polycrystalline silicon transistors, which have non-uniform characteristics and increased production costs due to complex structures and the need for additional doping apparatuses.
Innovation Solution
A method of fabricating an array substrate using a diode pumped solid state laser to crystallize amorphous silicon into polycrystalline silicon for the channel region, while maintaining amorphous silicon for source and drain regions, simplifying the structure and reducing fabrication costs by eliminating the need for doping apparatuses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous silicon is used for the active layer, then the fabrication process is simple, but the stability and carrier mobility are low
Solution Approach 1:
The patent applies local quality by creating different crystalline structures in different regions of the semiconductor layer. The channel region is crystallized into polycrystalline silicon to improve carrier mobility and stability, while the source and drain regions remain as amorphous silicon to maintain ease of fabrication and provide ohmic contact properties. This spatial differentiation of material properties resolves the contradiction between manufacturing simplicity and device performance.
Solution Approach 2:
The patent utilizes parameter changes by controlling the laser irradiation conditions to achieve partial crystallization. By adjusting laser power, scanning speed, and number of passes, the channel region is transformed from amorphous to polycrystalline state, fundamentally changing the electrical properties (carrier mobility increases from ~0.5 cm²/Vs to >10 cm²/Vs) while keeping the source/drain regions in the original amorphous state.
2Reliability
If polycrystalline silicon is formed by excimer laser annealing, then carrier mobility is improved, but the structure becomes complex and production cost increases
Solution Approach 1:
The patent extracts the doping step from the fabrication process by using laser-induced crystallization to achieve the desired electrical properties. Instead of forming polycrystalline silicon through complex multi-step doping processes with excimer lasers, the invention uses a simpler laser annealing approach that crystallizes the silicon while maintaining the amorphous source/drain regions, thereby reducing structural complexity and production costs while still achieving high carrier mobility in the channel region.
Solution Approach 2:
The patent employs a cost-effective laser annealing process that avoids the need for expensive excimer laser equipment and complex doping apparatus. The method uses readily available laser systems and simple processing steps, making the production process more economical and accessible while achieving the desired polycrystalline channel region for high carrier mobility.
3Reliability
If polycrystalline silicon is formed by excimer laser annealing, then carrier mobility is improved, but non-uniform crystallinity causes display quality deterioration
Solution Approach 1:
The patent applies periodic action by using multiple passes of laser irradiation with controlled intervals. The laser scans the channel region multiple times with decreasing power or increasing speed between passes, allowing progressive crystallization that ensures uniform polycrystalline formation. This periodic treatment prevents non-uniform crystallinity and associated display defects like striped stains, while still achieving the desired carrier mobility enhancement.
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 approach improves the mobility and stability of thin film transistors, ensures uniformity in crystallinity, and enhances display quality by preventing non-uniformity issues like striped stains, while reducing production costs and simplifying the fabrication process.
Implementation Method 1
irradiating a laser beam onto the intrinsic amorphous silicon pattern to form an active layer including a first portion of polycrystalline silicon
Implementation Method 2
crystallize amorphous silicon into polycrystalline silicon for the channel region
Data Source
AI summary
A method of fabricating an array substrate includes: forming a gate line and a gate electrode connected to the gate line; forming a gate insulating layer on the gate line and the gate insulting layer; sequentially forming an intrinsic amorphous silicon pattern and an impurity-doped amorphous silicon pattern on the gate insulating layer over the gate electrode; forming a data line on the gate insulating layer and source and drain electrodes on the impurity-doped amorphous silicon pattern, the data line crossing the gate line to define a pixel region, and the source and drain electrodes spaced apart from each other; removing a portion of the impurity-doped amorphous silicon pattern exposed through the source and drain electrodes to define an ohmic contact layer; irradiating a first laser beam onto the intrinsic amorphous silicon pattern through the source and drain electrode to form an active layer including a first portion of polycrystalline silicon and a second portion of amorphous silicon at both sides of the first portion; forming a passivation layer on the data line, the source electrode and the drain electrode, the passivation layer having a drain contact hole exposing the drain electrode; and forming a pixel electrode on the passivation layer in the pixel region, the pixel electrode connected to the drain electrode through the drain contact hole.