Polycrystalline Silicon Layer Metal Gettering for Leakage Reduction
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Solution Overview
Problem
Existing methods for crystallizing amorphous silicon into polycrystalline silicon using metal-induced crystallization techniques face challenges such as high leakage current due to residual crystallization-inducing metals, which are difficult to effectively remove, especially in regions intended for channels in thin-film transistors (TFTs) used in OLED displays.
Innovation Solution
A method involving the formation of a metal layer or metal silicide layer pattern in a predetermined region outside the channel area, with a smaller diffusion coefficient than the crystallization-inducing metal, followed by annealing to getter the residual metal into this region, thereby reducing its presence in the channel area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal-induced crystallization (MIC) or metal-induced lateral crystallization (MILC) is used to crystallize amorphous silicon into polycrystalline silicon, then the crystallization time is reduced and processing temperature is lowered, but crystallization-inducing metals remain in the polycrystalline silicon layer and increase leakage current
Solution Approach 1:
The patent extracts and removes crystallization-inducing metals from the polycrystalline silicon layer through a gettering process. A metal layer or metal silicide layer is formed in contact with the polycrystalline silicon layer, and through annealing, the crystallization-inducing metals are extracted from the channel region and transferred to the gettering layer, thereby reducing leakage current while maintaining the benefits of fast crystallization
Solution Approach 2:
The patent introduces a metal layer or metal silicide layer as an intermediary substance to facilitate the removal of crystallization-inducing metals. This intermediary layer acts as a gettering medium that attracts and captures the harmful metals through diffusion during annealing, effectively separating the harmful metals from the active channel region
2Object-generated harmful factors
If a gettering process is performed using impurity doping or amorphous silicon layer formation to remove crystallization-inducing metals, then some metal removal is achieved, but the metals are not effectively removed and high leakage current remains
Solution Approach 1:
The patent changes the parameter of the gettering layer material from conventional impurities or amorphous silicon to metal layers or metal silicide layers with specific diffusion coefficients. By selecting metals or metal silicides with appropriate diffusion characteristics, the gettering process becomes significantly more effective at removing crystallization-inducing metals, achieving lower leakage current and higher reliability
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 significantly reduces the off-current in TFTs and improves electrical characteristics by effectively removing crystallization-inducing metals from the channel region, leading to a low leakage current and enhanced performance in OLED display devices.
Implementation Method 1
a method of removing a crystallization-inducing metal from a first predetermined region of a polycrystalline silicon layer formed by a crystallization method using a crystallization-inducing metal, the method including: providing a metal layer pattern or metal silicide layer pattern in contact with the polycrystalline silicon layer in a second predetermined region of the polycrystalline silicon layer; and annealing the substrate to getter the crystallization-inducing metal existing in the first predetermined region to a region of the polycrystalline silicon layer corresponding to the metal layer pattern or metal silicide layer pattern
Implementation Method 2
annealing the substrate to getter the crystallization-inducing metal existing in the first predetermined region to a region of the polycrystalline silicon layer corresponding to the metal layer pattern or metal silicide layer pattern
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2A~2B
AI summary
A method of fabricating a polycrystalline silicon layer comprises: providing a polycrystalline silicon layer (220) formed by a crystallization method using a crystallization-inducing metal, the polycrystalline silicon layer (220) having a first predetermined region corresponding to a channel region in a TFT and a second predetermined region (220a); providing a metal layer pattern or metal silicide layer pattern (230) in contact with the polycrystalline silicon layer (220) in the second predetermined region (220a) of the polycrystalline silicon layer (220); and performing annealing to getter the crystallization-inducing metal existing in the first predetermined region to the second predetermined region (220a). Accordingly, the crystallization-inducing metal existing in the channel region of the polycrystalline silicon layer can be effectively removed, and thus a thin film transistor having an improved leakage current characteristic and an OLED display device including the same can be fabricated.