Polysilicon Film Grain Control via Activated Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for forming poly-Si films using excimer lasers struggle to control grain boundary formation and reduce crystallization energy, resulting in smaller, less homogeneous grains and poor electrical characteristics in poly-Si TFTs.
Innovation Solution
A method involving the formation of an activated layer with carbon, hydrogen, and silicon on a substrate, followed by an annealing process to crystallize an amorphous silicon film, which reduces the energy required for crystallization and controls grain boundary formation, using a barrier layer to prevent impurity diffusion and enhance grain growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If excimer laser is used to crystallize amorphous silicon film, then poly-Si film can be formed, but the grain boundaries cannot be controlled and grain homogeneity is poor
Solution Approach 1:
The patent applies preliminary action by forming a catalyst layer (containing Ni, Pd, Pt, or their alloys) on the substrate before depositing the amorphous silicon film. This catalyst layer is prepared in advance to control the crystallization process, enabling precise control over grain boundary formation and orientation when the amorphous silicon is subsequently crystallized, thereby resolving the contradiction between grain boundary controllability and grain homogeneity.
2Length of moving object
If excimer laser energy is increased to melt amorphous silicon film completely, then larger grains can be obtained, but the laser energy requirement becomes too high
Solution Approach 1:
The patent uses a catalyst layer as an intermediary substance between the substrate and the amorphous silicon film. This catalyst layer facilitates the crystallization process by providing nucleation sites and controlling grain growth, thereby enabling the formation of large grains with reduced laser energy input. The catalyst layer mediates the energy transfer and crystallization process, eliminating the need for complete melting of the amorphous silicon film.
Solution Approach 2:
The patent changes the physical and chemical parameters of the system by introducing a catalyst layer with specific materials (Ni, Pd, Pt, or their alloys) and controlling its thickness (5-50 nm). This parameter change fundamentally alters the crystallization behavior of the amorphous silicon, enabling grain growth at lower laser energies while maintaining large grain sizes and controlled grain boundaries.
3Productivity
If line beam size is enlarged to reduce crystallization energy, then product output increases, but the number of grain boundaries increases
Solution Approach 1:
The catalyst layer serves as an intermediary that enables efficient energy utilization during crystallization. By providing controlled nucleation sites, it allows the use of enlarged line beam sizes for higher productivity while maintaining precise control over grain boundary formation. The catalyst layer ensures that increased energy input translates to broader processing area rather than uncontrolled grain boundary proliferation.
Solution Approach 2:
The patent modifies the crystallization parameters by introducing the catalyst layer, which changes the energy distribution and grain growth dynamics. This parameter change allows the system to tolerate larger beam sizes and higher productivity rates while maintaining controlled grain boundary numbers through the catalyst's influence on nucleation and grain growth patterns.
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 larger, more uniform grains and improved electrical characteristics, reducing the number of grain boundaries and enhancing the mobility and transmission of poly-Si TFTs while lowering the energy required for crystallization.
Implementation Method 1
The LTPS uses a excimer laser as a heat source. When the excimer laser irradiates on the substrate having an amorphous silicon film, the amorphous silicon film absorbs the energy of the laser to transform into the poly-Si film.
Implementation Method 2
the amorphous silicon film absorbs the energy of the laser to transform into the poly-Si film
Implementation Method 3
performing an annealing process for the amorphous film to transform into the poly-Si film
Data Source
AI summary
A crystallizing method for forming a poly-Si film is described as follows. First, forming an activated layer on a substrate, and the molecule structure of the activated layer includes carbon, hydrogen, oxygen and silicon. And then, forming an amorphous silicon film on the activated layer. Finally, performing an annealing process to crystallize the amorphous silicon film and transform it into a poly-Si film.