Polysilicon Crystallinity Control for Leakage Reduction
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Solution Overview
Problem
Existing low-temperature polysilicon TFTs have defects such as grain boundaries, resulting in carrier mobility that is far less than that of large single crystal silicon TFTs, necessitating improved performance to meet increasing demands.
Innovation Solution
A display substrate with a crystallization induction layer and polysilicon layer, where the polysilicon layer overlaps induction layer patterns and intervals, with higher crystallinity over patterns and lower crystallinity over intervals, enhancing carrier mobility and reducing leakage current through patterning and excimer laser annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the polysilicon layer is fully crystallized to improve TFT performance, then carrier mobility increases, but leakage current increases due to grain boundaries
Solution Approach 1:
The invention creates a non-uniform crystallinity distribution where the polysilicon layer has different crystallinity levels in different regions. The higher crystallinity regions provide good carrier mobility for TFT operation, while the lower crystallinity regions in the intervals help reduce leakage current by acting as potential barriers or reducing grain boundary density in critical leakage paths.
Solution Approach 2:
The intervals between induction layer patterns serve as intermediary regions with lower crystallinity that mediate between the high crystallinity regions. These intermediary zones help manage the trade-off between carrier mobility and leakage current by providing transition regions that can reduce grain boundary effects while maintaining overall device performance.
2Ease of manufacture
If a uniform crystallization induction layer is used, then the manufacturing process is simple, but the polysilicon grains are not uniform resulting in suboptimal TFT performance
Solution Approach 1:
The invention segments the crystallization induction layer into multiple patterns with different orientations rather than using a uniform layer. This segmentation is achieved through a patterning process that, while adding steps, uses standard photolithography and etching techniques. The result is improved polysilicon grain uniformity through controlled nucleation at multiple oriented interfaces, with the manufacturing complexity remaining manageable through conventional semiconductor fabrication processes.
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
The approach results in uniform polysilicon grains, improved TFT device performance, and reduced leakage current, effectively addressing the limitations of existing low-temperature polysilicon TFTs by controlling carrier mobility and simplifying the manufacturing process.
Implementation Method 1
the amorphous silicon film layer is irradiated with an excimer laser, after the surface of the amorphous silicon film is melted, heat will continue to be transferred downward, and the entire film layer is almost fully melted
Implementation Method 2
heat will continue to be transferred downward
Implementation Method 3
underlying amorphous silicon particles as seed crystals grow horizontally and vertically to obtain larger size grains
Data Source
AI summary
A display substrate, a display apparatus, and a manufacturing method of the display substrate are provided. The display substrate includes: a base substrate; and a crystallization induction layer and a polysilicon layer stacked on the base substrate. The crystallization induction layer includes induction layer patterns and intervals between the induction layer patterns. The polysilicon layer includes a portion overlapping the induction layer patterns and a portion overlapping the intervals, a crystallinity of the portion of the polysilicon layer overlapping the induction layer patterns is larger than a crystallinity of the portion of the polysilicon layer overlapping the intervals.