Thin Film Transistor Laser Annealing Process
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Solution Overview
Problem
The manufacturing process of low temperature poly-silicon thin film transistors is complex and costly due to the need for dehydrogenation, excimer laser annealing, and ion doping, which results in large grain boundary protrusions and low process efficiency.
Innovation Solution
A method involving ion doping of the channel, source, and drain regions followed by laser annealing with an interlayer insulating layer to crystallize the active layer and activate ions simultaneously, reducing process complexity and cost while avoiding large grain boundary protrusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dehydrogenation and excimer laser annealing are performed after a-Si deposition, then the active layer crystallizes, but large grain boundary protrusions are produced which affect transistor performance
Solution Approach 1:
The patent changes the processing parameters by performing laser annealing at a lower energy level (350-450 mJ/cm²) compared to conventional excimer laser annealing. This parameter modification enables crystallization of the active layer while suppressing excessive grain growth that causes boundary protrusions, thus improving transistor performance without the harmful morphological effects
Solution Approach 2:
The patent employs a specific sequence of periodic actions: first performing ion doping to introduce impurities, then performing laser annealing to crystallize the layer and activate the doped ions simultaneously. This periodic sequence optimizes the crystallization process to avoid large grain boundary protrusions while maintaining high transistor performance
2Reliability
If ion doping is performed to activate channel, source, and drain regions separately, then the transistor regions are activated, but the process complexity and cost increase
Solution Approach 1:
The patent merges two separate processes into one: ion doping and laser annealing are combined into a single integrated process. The ion doping step introduces impurities into the channel, source, and drain regions, and the subsequent laser annealing simultaneously crystallizes the active layer and activates all doped regions. This eliminates the need for separate activation steps, reducing process complexity and cost while maintaining reliable ion activation
Solution Approach 2:
The laser annealing step serves multiple functions simultaneously: it crystallizes the amorphous silicon active layer, activates the doped ions in the channel region, and activates the doped ions in the source and drain contact regions. This multi-functionality reduces the total number of process steps required while ensuring proper transistor operation
3Reliability
If multiple separate processes are used for crystallization and ion activation, then thorough activation is achieved, but process efficiency decreases
Solution Approach 1:
The patent combines crystallization and ion activation into a single laser annealing process. The laser energy simultaneously performs both functions: crystallizing the amorphous silicon structure and activating the doped ions in all regions. This merging of functions maintains thorough activation while significantly improving process efficiency by reducing the total processing time and number of steps
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 simplifies the process, reduces costs, and improves the efficiency of thin film transistor manufacturing by crystallizing the active layer and activating ions in a single step, enhancing the transistor's performance by minimizing leakage current and improving contact interfaces.
Implementation Method 1
performing laser annealing to the active layer of the substrate with the interlayer insulating layer, so as to make the active layer crystallize
Implementation Method 2
make the active layer crystallize and the ions doped in the channel region, the source contact region and the drain contact region of the active layer activate simultaneously
Implementation Method 3
performing ion doping to a channel region of the active layer; performing ion doping to a source contact region and a drain contact region of the active layer
Data Source
AI summary
The present disclosure provides a method for manufacturing a thin film transistor comprising, forming a pattern of an active layer on a substrate through a patterning process; performing ion doping to a channel region of the active layer; forming a gate insulating layer; forming a pattern of a gate through the patterning process; performing ion doping to a source contact region and a drain contact region of the active layer; forming an interlayer insulating layer; and performing laser annealing to the active layer, so as to make the active layer crystallize and the ions doped in the channel region, the source contact region and the drain contact region of the active layer activate simultaneously. In this method, the crystallization of the active layer and the activation of the ions doped in the active layer are implemented in the same process, which reduces the process cost and improves the efficiency.