TFT Active Layer Segmentation for Channel Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing thin film transistors using hydrogenated amorphous silicon have low carrier mobility due to defects, resulting in small channel current, while alternative materials like low-temperature polycrystalline silicon and amorphous IGZO are complex, costly, and unstable in manufacturing.
Innovation Solution
A thin film transistor with an active layer comprising alternately stacked active semiconductor sub-layers and insulation sub-layers, where the source and drain are electrically connected to the active semiconductor sub-layers, increasing channel current through multiple channel formation and improved compactness from top to bottom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hydrogenated amorphous silicon is used as the active layer material, then the manufacturing process is simple and cost is low, but the carrier mobility is low and channel current is small
Solution Approach 1:
The active layer is segmented into multiple active semiconductor sub-layers (first, second, third sub-layers) stacked in the thickness direction. Each sub-layer contributes to charge conduction, creating multiple conduction paths. This segmentation increases the total channel current while maintaining the simplicity of using amorphous silicon material throughout, thus resolving the contradiction between manufacturing simplicity and carrier mobility.
2Reliability
If low-temperature polycrystalline silicon is used to increase carrier mobility, then the channel current increases, but the manufacturing process becomes complicated and cost increases
Solution Approach 1:
Instead of using complex low-temperature polycrystalline silicon, the patent segments the simple amorphous silicon active layer into multiple sub-layers with different thicknesses. The first active semiconductor sub-layer has greater thickness than the second, which has greater thickness than the third. This segmentation creates enhanced charge conduction capabilities without introducing complex manufacturing processes, thus resolving the contradiction between carrier mobility and manufacturing complexity.
Solution Approach 2:
Different regions of the active layer are given different local properties through varying sub-layer thicknesses. The first active semiconductor sub-layer (closer to gate electrode) has greater thickness to handle higher charge densities, while upper sub-layers have progressively smaller thicknesses. This local quality variation optimizes charge conduction throughout the active layer without requiring complex polycrystalline silicon processing.
3Reliability
If amorphous IGZO is used as active layer material, then carrier mobility is higher, but manufacturing cost is high and yield is low
Solution Approach 1:
The patent uses multiple stacked active semiconductor sub-layers made of amorphous silicon instead of amorphous IGZO. The segmentation into multiple sub-layers with progressively decreasing thicknesses from bottom to top creates enhanced charge conduction paths, achieving higher effective carrier mobility while maintaining the manufacturing advantages of amorphous silicon (lower cost, higher yield).
Solution Approach 2:
The patent changes the thickness parameter of successive active semiconductor sub-layers to optimize performance. Each subsequent sub-layer has smaller thickness than the previous one, creating a gradient structure that enhances charge conduction. This parameter variation achieves improved carrier mobility without changing the material system from amorphous silicon, thus maintaining high manufacturing yield and low cost.
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 solution effectively increases channel current and reduces manufacturing complexity and cost by forming multiple channels in the thin film transistor, addressing the limitations of low carrier mobility and high costs associated with existing materials.
Implementation Method 1
an active layer of a thin film transistor is usually made of hydrogenated amorphous silicon (a-Si:H)... most charges attracted by a gate in a TFT array substrate are captured in the defects and cannot conduct electricity... the carrier mobility of the active layer is less than 1 cm2/(V*s), thus the channel current is relatively small
Implementation Method 2
alternately depositing a plurality of active semiconductor film layers and a plurality of insulation film layers... the thickness of each of the active semiconductor sub-layers is 200 Å-600 Å, and the thickness of each of the insulation sub-layers is 200 Å-600 Å... the compactness of the plurality of active semiconductor sub-layers and the plurality of insulation sub-layers gradually increases from top to bottom
Implementation Method 3
forming a pattern including the active layer by a patterning process... the etching rate of the material of the active semiconductor sub-layers is less than that of the material of the insulation sub-layers
Data Source
AI summary
The present invention provides a thin film transistor. An active layer of the thin film transistor comprises a plurality of active semiconductor sub-layers and a plurality of insulation sub-layers, which are stacked alternately. A source and a drain of the thin film transistor are electrically connected to the plurality of active semiconductor sub-layers. Correspondingly, the present invention further provides a method for manufacturing a thin film transistor, and an array substrate. The present invention can effectively increase channel current of the active layer in a thin film transistor, and solves the problem of small channel current resulted from low carrier mobility of the active layer.