Polysilicon TFT Heat Retaining Layer for Laser Crystallization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The crystallization of amorphous silicon layers on conductive substrates results in a shorter melt duration time due to increased heat loss, leading to deteriorated crystal properties and difficulty in achieving high mobility polysilicon thin film transistors (TFTs) when exposed to laser light during the crystallization process.
Innovation Solution
A heat retaining layer, such as SiOxNy, is formed on the amorphous silicon layer to absorb and block heat, increasing the melt duration time and preventing protrusions at grain boundaries, thereby facilitating the formation of a polysilicon layer with improved crystal properties on conductive substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser annealing method is used to crystallize amorphous silicon layer on conductive substrate, then polysilicon layer can be formed, but melt duration time is reduced due to increased heat loss
Solution Approach 1:
A heat retaining layer is introduced as an intermediary between the laser source and the amorphous silicon layer. This layer absorbs and retains laser energy, mediating the heat transfer process to extend the melt duration time while maintaining effective crystallization of the polysilicon layer.
2Duration of action of moving object
If heat retaining layer is formed on amorphous silicon layer, then melt duration time is increased, but device structure becomes more complex
Solution Approach 1:
The heat retaining layer modifies the thermal parameters of the system by introducing materials with specific heat retention properties. This changes the heat distribution and retention characteristics during laser annealing, extending the melt duration without fundamentally altering the basic device architecture.
3Reliability
If amorphous silicon layer is exposed to laser light for crystallization, then polysilicon layer is formed, but protrusions occur at grain boundaries
Solution Approach 1:
The heat retaining layer acts as a mediator that controls the spatial and temporal distribution of laser energy. By retaining heat uniformly across the amorphous silicon layer, it prevents localized overheating that causes protrusions at grain boundaries, thereby maintaining surface flatness while achieving effective crystallization.
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 heat retaining layer effectively prolongs the melt duration time of the amorphous silicon layer, enhances crystal properties, and reduces protrusions at grain boundaries, enabling the fabrication of high mobility polysilicon TFTs with a smooth surface, suitable for high-speed applications.
Implementation Method 1
The heat retaining layer may be formed on the amorphous silicon layer, and may be capable of absorbing heat and/or blocking heat so as to help maintain and/or increase a melt duration time of the amorphous silicon layer
Implementation Method 2
laser energy is supplied to a substrate on which an amorphous silicon layer is deposited to melt the amorphous silicon layer
Implementation Method 3
the amorphous silicon layer is cooled to form a polysilicon layer
Data Source
AI summary
A polysilicon thin film transistor (TFT) may include a substrate, at least one insulating layer, a semiconductor layer, a gate electrode, a source electrode, a drain electrode, and a heat retaining layer formed to contact the semiconductor layer. The heat retaining layer may reduce and/or prevent a reduction in a melt duration time of amorphous silicon during a crystallization process for forming a polysilicon layer of the TFT.