Continuous Wave Laser Crystallization for Thin Film Transistor Grain Control
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Solution Overview
Problem
Current methods for forming semiconductor thin films with different characteristics in a single process are challenging due to increased input energy requirements and difficulties in achieving desired ON-state and OFF-state current characteristics for TFTs in display devices.
Innovation Solution
A method involving the relative scan of a thin film with a continuous wave light beam to crystallize specific areas, creating strip-shaped regions with varying grain sizes, allowing for the formation of TFTs with distinct characteristics without increasing input energy, using a substrate irradiated with a laser beam where the light beam's projection has a major axis crossing the scan direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an amorphous silicon film is polycrystallized by irradiating with a pulsed laser, then crystalline silicon thin film can be formed, but the running cost increases due to frequent laser system overhaul
Solution Approach 1:
The patent changes the laser operating parameters from pulsed mode to continuous wave mode. This parameter change eliminates the frequent overhaul issues associated with pulsed laser systems while maintaining the ability to form crystalline silicon thin films through controlled irradiation of amorphous silicon films.
Solution Approach 2:
The patent replaces the complex pulsed laser system with a simpler continuous wave laser system. This substitution reduces maintenance requirements and running costs while achieving the same crystallization function through continuous rather than intermittent energy delivery.
2Manufacturing precision
If different crystallization conditions are applied to form TFTs with different characteristics, then ON-state and OFF-state current characteristics can be optimized, but the number of processes increases
Solution Approach 1:
The patent applies local quality by irradiating different regions of the amorphous silicon film with different laser power densities. This allows crystalline regions with different grain sizes to form in different areas, enabling optimization of both ON-state and OFF-state current characteristics within a single process step without requiring multiple separate crystallization processes.
Solution Approach 2:
The patent makes the single continuous wave laser process universal by showing it can produce multiple crystalline structures with different properties from one irradiation step. The same process setup can generate both large-grain and small-grain crystalline regions, eliminating the need for separate processing steps for different TFT types.
3Manufacturing precision
If higher laser power density is used to form large-grain crystalline areas, then ON-state current characteristics improve, but the energy consumption increases
Solution Approach 1:
The patent applies local quality by using higher laser power density only in specific regions where large-grain crystalline structures are needed for optimal ON-state current characteristics. Other regions receive lower power density, maintaining energy efficiency while still achieving the required performance in critical areas.
Solution Approach 2:
The patent optimizes energy consumption by carefully controlling the laser power density parameter. By adjusting this parameter to the minimum level required to achieve the desired crystalline structure, the patent improves ON-state current characteristics without excessive energy consumption.
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 method enables the efficient formation of TFTs with enhanced ON-state current characteristics and uniformity, facilitating the production of display devices with improved performance and reduced energy consumption.
Implementation Method 1
crystallizing at least a predetermined area of the thin film into a crystallized area through relative scan of the thin film with the substrate irradiated with a continuous wave light beam
Implementation Method 2
crystallizing at least a predetermined area of the thin film into a crystallized area
Data Source
AI summary
A method of manufacturing a substrate having a thin film thereabove includes: forming a thin film above the substrate; and crystallizing at least a predetermined area of the silicon thin film into a crystallized area through relative scan of the silicon thin film which is performed while the thin film is being irradiated with a continuous wave light beam, wherein in the crystallizing, a projection of the light beam on the thin film has a major axis in a direction crossing a direction of the relative scan, and the formed crystallized area includes a strip-shaped first area extending in the direction crossing the direction of the relative scan and a second area adjacent to the strip-shaped first area, the strip-shaped first area including crystal grains having an average grain size larger than that of crystal grains in the second area.