Polysilicon TFT Active Layer Thickness Layout for Contact Reliability
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Solution Overview
Problem
Existing methods for manufacturing thin film transistors in display devices, particularly those using polysilicon, face challenges in achieving optimal electron mobility and structural integrity, which can lead to performance issues and damage during processing.
Innovation Solution
A method involving the formation of a polysilicon layer on a substrate, followed by patterning to create regions of varying thickness, ion implantation to form an active layer, and the subsequent formation of electrodes and a light emitting element, while ensuring the active layer is not damaged during contact hole formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If polysilicon is used to replace amorphous silicon in TFTs, then electron mobility is improved, but structural integrity and performance reliability deteriorate during processing
Solution Approach 1:
The patent applies local quality by creating different thickness regions within the polysilicon active layer. The first region has a first thickness and the second region has a second thickness greater than the first thickness, allowing each region to serve different functional purposes. This local differentiation enables the thin first region to provide high electron mobility while the thicker second region provides structural support and prevents damage during contact hole formation, thus resolving the contradiction between mobility improvement and reliability maintenance.
2Ease of manufacture
If contact holes are formed through the active layer, then source and drain electrodes can be connected, but the active layer may be damaged
Solution Approach 1:
The patent applies preliminary action by forming the second region with greater thickness in advance, before contact hole formation. This pre-prepared thicker region serves as a structural reinforcement that prevents active layer damage during subsequent contact hole etching processes. The preliminary structural preparation ensures that when contact holes are later formed to connect source and drain electrodes, the active layer maintains its integrity and does not suffer from etching-induced damage.
3Ease of manufacture
If uniform thickness polysilicon layer is used, then manufacturing is simplified, but electron mobility and performance characteristics are insufficient
Solution Approach 1:
The patent resolves this contradiction by implementing local quality variations in the polysilicon active layer thickness. Instead of using a uniform thickness throughout, the first region is formed with a first thickness optimized for high electron mobility, while the second region is formed with a second thickness greater than the first to provide structural stability. This localized thickness differentiation allows each region to be optimized for its specific function, achieving both high performance characteristics and manufacturing feasibility through selective thickness control.
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 improves the characteristics of thin film transistors by maintaining the structural integrity of the active layer, enhancing electron mobility, and ensuring reliable performance in display devices.
Implementation Method 1
irradiating the amorphous silicon layer with a laser beam
Implementation Method 2
partially implanting ions into the polysilicon pattern to form an active layer
Data Source
AI summary
A method of manufacturing a display device including forming a polysilicon layer on a substrate, patterning the polysilicon layer to form a polysilicon pattern including a first region and a second region each having a first thickness, and a third region having a second thickness less than the first thickness, forming a gate insulation layer on the polysilicon pattern, forming a gate electrode on the gate insulation layer, partially implanting ions into the polysilicon pattern to form an active layer, forming an insulation interlayer on the gate electrode, forming source and drain contact holes each passing through the insulation interlayer and the gate insulation layer and respectively overlapping the first region and the second region, forming source and drain electrodes respectively filling the source and drain contact holes, and forming a light emitting element electrically connected to the source electrode or the drain electrode.