Poly-last Flat Panel Display Process for Cost-Efficient Poly-Si Manufacturing
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Solution Overview
Problem
The existing fabrication processes for flat panel displays face challenges in achieving the higher performance of polycrystalline silicon (poly-Si) technology while maintaining the lower costs associated with amorphous silicon (a-Si) processes, as poly-Si processes require expensive equipment and more steps, limiting their widespread adoption.
Innovation Solution
A poly-last process architecture is introduced, where the critical silicon crystallization phase is separated and performed last, allowing for the use of existing a-Si manufacturing facilities to convert a-Si TFTs to poly-Si TFTs using laser and hydrogenation tools, eliminating the need for expensive poly-Si facilities and enabling the production of both a-Si and poly-Si displays with minimal additional investment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If poly-Si process is used to achieve higher display performance, then electron mobility and pixel density are improved, but manufacturing cost and process complexity increase significantly
Solution Approach 1:
The manufacturing process is segmented into two distinct phases: first, a-Si TFT fabrication using low-cost existing equipment, and second, selective poly-Si conversion only where high performance is needed. This segmentation allows the system to achieve poly-Si performance benefits without requiring complete poly-Si fabrication infrastructure, thereby reducing manufacturing costs while maintaining high display performance.
Solution Approach 2:
The a-Si TFT structure is fabricated in advance using established low-cost processes, creating a baseline structure that can later be selectively upgraded to poly-Si through laser annealing. This preliminary action allows manufacturers to defer the expensive poly-Si conversion step until after initial structure formation, reducing upfront equipment investment while ensuring high performance where required.
2Speed
If poly-Si process is used to achieve higher electron mobility, then aperture ratio and pixel density improve, but process steps and equipment requirements increase
Solution Approach 1:
The expensive and complex poly-Si laser annealing step is extracted from the standard fabrication flow and applied only selectively to specific regions where high electron mobility is critical. This extraction allows the majority of the display to be manufactured using simpler a-Si processes, reducing overall process complexity and equipment requirements while maintaining high performance in key areas.
Solution Approach 2:
The process design allows dynamic selection of TFT type (a-Si or poly-Si) based on performance requirements for different display regions. This dynamic approach enables optimization of electron mobility where needed while minimizing process complexity in less demanding areas, adapting the manufacturing strategy to the specific performance needs of each pixel or circuit region.
3Ease of manufacture
If a-Si process is used to reduce manufacturing cost, then equipment investment is lower, but electron mobility and display performance are limited
Solution Approach 1:
The material state parameter of the TFT channel is changed from amorphous to polycrystalline through selective laser annealing. This parameter change dramatically improves electron mobility and display performance in specific regions while maintaining the cost advantages of a-Si manufacturing for the overall display structure. The selective application of this parameter change allows performance optimization without proportionally increasing manufacturing costs.
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 enables the efficient manufacture of high-performance poly-Si driven OLED displays at a lower cost, allowing existing a-Si manufacturing facilities to produce both a-Si and poly-Si displays without the need for significant investment in new equipment, thereby capitalizing on existing infrastructure.
Implementation Method 1
The channel silicon precursor is irradiated by a laser using a polycrystalline silicon or polycrystalline silicon compatible process
Implementation Method 2
A poly-last process architecture is introduced, where the critical silicon crystallization phase is separated and performed last
Implementation Method 3
allowing for the use of existing a-Si manufacturing facilities to convert a-Si TFTs to poly-Si TFTs using laser and hydrogenation tools
Data Source
AI summary
An embodiment is a method and apparatus to fabricate a flat panel display. A poly-last structure is formed for a display panel using an amorphous silicon or amorphous silicon compatible process. The poly-last structure has a channel silicon precursor. The display panel is formed from the poly-last structure using a polysilicon specific or polysilicon compatible process.