Low Temperature Polysilicon Film Grain Uniformity via Laser Annealing
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Solution Overview
Problem
Current methods for manufacturing low temperature polysilicon films, such as excimer laser annealing, face challenges in achieving uniform grain size and distribution, which affects the electrical performance of transistors, particularly in AMOLED panels, due to non-uniform thickness distribution of amorphous silicon films.
Innovation Solution
A method involving the formation of a buffer layer on a substrate, followed by depositing an amorphous silicon layer and subjecting it to heat treatment, then dividing the layer into areas for laser annealing based on thickness distribution, with varying laser energy densities applied to each area to achieve uniform polycrystalline silicon grain growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional laser annealing is applied uniformly across the amorphous silicon layer, then the process is simple and fast, but the grain size and distribution become non-uniform due to thickness variations
Solution Approach 1:
The patent applies different laser energy densities to different regions of the amorphous silicon layer based on its thickness distribution. Specifically, the laser annealing process is divided into multiple zones (first, second, and third areas) with progressively increasing energy densities, allowing each region to receive optimized treatment that compensates for local thickness variations and achieves uniform grain growth across the entire layer
Solution Approach 2:
The amorphous silicon layer is segmented into multiple annealing zones based on thickness distribution, with each zone receiving tailored laser energy treatment. This segmentation allows the complex non-uniform thickness profile to be handled through multiple simpler, localized annealing operations rather than attempting a single uniform treatment
2Productivity
If the amorphous silicon layer thickness is non-uniform, then deposition is easier and faster, but the resulting polysilicon grains are non-uniform in size and distribution
Solution Approach 1:
The patent changes the laser annealing parameter (energy density) according to the spatial position and thickness of the amorphous silicon layer. By adjusting the energy density parameter across different zones, the process compensates for thickness variations and achieves uniform grain growth without requiring uniform deposition
Solution Approach 2:
The patent implements a feedback mechanism where the thickness distribution of the amorphous silicon layer is measured and used to determine the laser annealing parameters for different regions. This feedback loop allows the annealing process to automatically adapt to thickness variations and produce uniform grain structure
3Manufacturing precision
If higher laser energy density is applied to achieve larger grain size, then grain growth is improved, but non-uniform regions may be damaged or melted
Solution Approach 1:
The patent applies locally optimized laser energy densities to different regions of the amorphous silicon layer, matching the energy input to the local thickness requirements. This prevents over-heating and damage to thinner regions while providing sufficient energy for grain growth in thicker regions, maintaining film integrity throughout
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 results in polysilicon films with large, uniformly distributed grains across the substrate, enhancing the electrical performance of low temperature polysilicon transistors by addressing the non-uniformity issues inherent in conventional methods.
Implementation Method 1
performing heat treatment after forming the amorphous silicon layer
Implementation Method 2
dividing the amorphous silicon layer into a plurality of areas for laser annealing
Implementation Method 3
controlling grain size and grain uniformity... making a polysilicon film have large size and uniformly distributed grains
Data Source
AI summary
A method of manufacturing low temperature polysilicon is provided, comprising: depositing a buffer layer (20) on a base substrate (10); depositing an amorphous silicon layer (30) on the buffer layer; performing a heat treatment after forming the amorphous silicon layer; and dividing the amorphous silicon layer into a plurality of areas for laser annealing according to a thickness distribution of the amorphous silicon layer to form a polycrystalline silicon layer. A low temperature polysilicon film manufactured by the low temperature polysilicon manufacturing method and a thin film transistor having the film are also provided. The method realizes large grain size for polysilicons in each area of the amorphous silicon layer and a uniform distribution of polysilicon grain size across the entire substrate.