IGZO TFT Substrate Copper Diffusion Barrier
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Solution Overview
Problem
Conventional thin film transistor substrate manufacturing techniques face issues such as semiconductor defects, current leakage, and increased production costs due to etching processes that damage indium gallium zinc oxide (IGZO) and require additional barrier materials to prevent copper diffusion.
Innovation Solution
A thin film transistor substrate with a stacked source/drain electrode structure comprising copper and indium tin oxide, where copper is positioned on top of indium tin oxide, eliminating the need for additional barrier materials and using a stripping process instead of etching to form the electrodes, thereby preventing semiconductor defects and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etching process is used to form source/drain electrode, then electrode pattern can be defined, but IGZO layer is damaged causing semiconductor defects and current leakage
Solution Approach 1:
A stacked structure comprising a first metal layer (Cu) and a second metal layer (ITO or other transparent conductive oxide) is used as an intermediary solution. The second metal layer serves as a barrier between the etching process and the IGZO semiconductor layer, allowing electrode formation while protecting the IGZO from damage.
Solution Approach 2:
The source/drain electrode is segmented into multiple layers (first metal layer and second metal layer) with different functions. The first metal layer provides electrical conductivity, while the second metal layer provides protection and barrier functions, separating the harmful etching effects from the IGZO layer.
2Reliability
If copper is used as source/drain electrode material, then electrical conductivity is improved, but copper diffuses to channels causing short-circuiting
Solution Approach 1:
The second metal layer (transparent conductive oxide such as ITO) acts as an intermediary barrier layer between the copper first metal layer and the IGZO channel. This barrier prevents copper diffusion while maintaining electrical conductivity through the stacked structure.
Solution Approach 2:
The source/drain electrode is formed as a composite stacked structure combining copper (for high conductivity) and transparent conductive oxide (for barrier and conductivity). This composite structure achieves both high electrical conductivity and prevention of copper diffusion.
3Object-generated harmful factors
If additional barrier material is added to prevent copper diffusion, then copper diffusion is prevented, but manufacturing complexity and cost increase
Solution Approach 1:
The second metal layer (transparent conductive oxide) serves multiple functions simultaneously: it acts as a barrier to prevent copper diffusion, provides electrical conductivity for the electrode function, and can serve as part of the electrode structure itself. This multi-functionality eliminates the need for separate barrier layers.
Solution Approach 2:
The barrier function and the electrode function are merged into a single stacked structure. The second metal layer combines the barrier properties with the conductive properties needed for the electrode, eliminating the need for additional separate barrier material layers.
Data Source
AI summary
A thin film transistor substrate and its manufacturing method are provided. The thin film transistor substrate avoids semiconductor defects caused by acid corrosion of a metal oxide channel during an etching process of forming a source/drain electrode, and effectively prevents copper from diffusing downward into the metal oxide channel under high temperature conditions. Such configuration eliminates a need to additionally use a barrier material, reduces production costs, and prevents short-circuiting resulting from a residual barrier material.