TFT Barrier Layer Prevents Copper Ion Diffusion
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Solution Overview
Problem
Copper ions from the light-shielding layer in thin film transistors easily diffuse into the buffer and active layers, leading to increased contact resistance and parasitic capacitance, and are oxidized by fluorine-based oxidizing gases, which further degrades the electrical characteristics of TFT devices.
Innovation Solution
A barrier layer comprising a diffusion barrier layer and an etch barrier layer is introduced on the metal layer, using materials like molybdenum, titanium, or tantalum for the diffusion barrier and indium gallium zinc oxide or indium tin oxide for the etch barrier to prevent copper ion diffusion and oxidation, with the etch barrier layer being conductively treated to reduce oxygen content and enhance conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If copper is used in the light-shielding layer to reduce trace areas, then device resolution and transmittance are improved, but copper ions easily diffuse into the buffer layer and active layer, causing contact resistance and parasitic capacitance to increase
Solution Approach 1:
A barrier layer comprising a diffusion barrier layer and an etch barrier layer is introduced as an intermediary between the copper-containing light-shielding layer and the buffer/active layers. The diffusion barrier layer (molybdenum, titanium, or tantalum) specifically prevents copper ion diffusion, while the etch barrier layer (indium gallium zinc oxide or indium tin oxide) protects during etching processes. This intermediary structure allows copper to be used for trace area reduction without causing contact resistance increases.
2Productivity
If fluorine-based oxidizing gas is used to dry etch the buffer layer for forming holes, then etching efficiency is improved, but copper ions of the light-shielding layer are oxidized, increasing contact resistance and decreasing electrical characteristics
Solution Approach 1:
The etch barrier layer serves as a protective intermediary between the fluorine-based oxidizing gas and the copper-containing light-shielding layer. This layer allows the use of aggressive fluorine-based etchants for efficient buffer layer etching while preventing oxidation of copper ions, thereby maintaining electrical characteristics during high-productivity etching processes.
Solution Approach 2:
The etch barrier layer is designed to be selectively removed after serving its protective function. The layer is configured to be removed by the fluorine-based oxidizing gas etching process itself, eliminating the need for separate removal steps while having already protected the copper layer from oxidation during the critical etching phase.
3Reliability
If a barrier layer is introduced to prevent copper ion diffusion, then contact resistance is reduced, but device structure complexity increases
Solution Approach 1:
The barrier function is segmented into two distinct layers with specialized functions: the diffusion barrier layer specifically addresses copper ion diffusion, while the etch barrier layer specifically addresses oxidation during etching. This segmentation allows each layer to be optimized for its specific function and enables selective removal of the etch barrier layer, reducing the impact on overall device complexity.
Solution Approach 2:
The barrier layer structure serves multiple functions simultaneously: it acts as a diffusion barrier, an etching protection layer, and a template for subsequent processing steps. The etch barrier layer in particular is designed to be selectively removed to create contact holes, making it multi-functional and reducing the need for additional processing layers.
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 barrier layer effectively prevents copper ion diffusion and oxidation, stabilizing the threshold voltage and improving the electrical characteristics and stability of TFT devices by reducing contact resistance and parasitic capacitance.
Implementation Method 1
the barrier layer is configured to prevent copper ions in the metal layer from diffusing into an active layer of the TFT device
Implementation Method 2
the etch barrier layer is subjected to a conductive treatment to reduce an oxygen element content in a metal oxide semiconductor material, such that a resistivity of the metal oxide semiconductor material is reduced to become a conductor
Data Source
AI summary
A thin film transistor (TFT) device, a manufacturing method thereof, and a TFT array substrate are provided. A light-shielding layer is provided with a barrier layer for preventing copper ions in a metal layer from diffusing into a buffer layer and an active layer. The barrier layer is also provided with an etch barrier layer for preventing the copper ions of the metal layer being oxidized by a fluorine-based oxidizing gas due to the fluorine-based oxidizing gas is used to dry etch the buffer layer for forming a signal via hole, so as to improve a performance stability of the TFT device. A source is electrically connected to the light-shielding layer through the signal via hole to eliminate a threshold voltage drift of the TFT.