TFT Copper Wire Adhesion via Barrier and Capping Layers
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Solution Overview
Problem
Copper wires used in TFT substrates for displays face issues with adhesion, oxidation, corrosion, and signal delay due to their poor interaction with insulating substrates and semiconductor layers, leading to reduced reliability and performance.
Innovation Solution
A wire structure comprising a barrier layer, a copper conductive layer, an intermediate copper nitride layer, and a capping layer is implemented, which enhances adhesion, prevents copper ion diffusion, and reduces corrosion, thereby improving the reliability and performance of copper wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper film is used as wiring material, then resistivity is reduced and signal delay is improved, but adhesion to insulating substrate and semiconductor layer deteriorates
Solution Approach 1:
A barrier layer is introduced as an intermediary between the copper wiring layer and the underlying insulating substrate or semiconductor layer. This barrier layer serves as a mediator that prevents direct contact between copper and the substrate, thereby maintaining electrical conductivity while preventing adhesion failures and metal diffusion.
Solution Approach 2:
The wiring structure is transformed from pure copper to a composite multi-layer structure consisting of copper wiring layer, barrier layer, and capping layer. This composite structure combines the low resistivity of copper with the adhesion and protective properties of the barrier and capping layers.
2Ease of manufacture
If copper film is exposed to chemicals in subsequent processes, then etching and patterning can be performed, but copper is oxidized and corroded
Solution Approach 1:
A capping layer is formed over the copper wiring layer before subsequent chemical processing steps. This preliminary protective action prevents copper from being exposed to oxidizing chemicals during etching and patterning processes, thereby preventing corrosion while allowing necessary manufacturing steps to proceed.
Solution Approach 2:
The capping layer acts as an intermediary protective barrier between the copper wiring layer and the chemical environment during manufacturing processes. It mediates the interaction by allowing the copper to remain protected while still enabling the overall manufacturing process to continue.
3Reliability
If multi-layered structure with barrier film and capping film is used, then adhesion and corrosion resistance are improved, but copper ions penetrate into semiconductor layer during etching
Solution Approach 1:
The barrier layer serves as a specialized intermediary layer positioned between the copper wiring layer and the semiconductor layer. It specifically mediates against copper ion diffusion into the semiconductor layer during etching processes, while still allowing the copper to maintain its electrical function.
Solution Approach 2:
The barrier layer provides localized protection specifically at the interface between copper and semiconductor/insulating substrate. This local quality enhancement targets the specific region where copper ion diffusion is most problematic, without requiring modification of the entire copper wiring structure.
4Length of stationary object
If copper wire is used for long gate lines and data lines, then resistivity increases causing signal delay, but switching element performance must be maintained
Solution Approach 1:
The electrical parameters of the wiring system are optimized by using copper material with inherently lower resistivity. This parameter change in material properties allows long wire lengths to be used without excessive resistance, maintaining signal transmission quality over extended distances while preserving switching element performance.
Data Source
AI summary
Provided are a wire structure, a method of forming a wire, a thin film transistor (TFT) substrate, and a method of manufacturing the TFT substrate. The wire structure includes a barrier layer disposed on a lower structure, a copper conductive layer comprising copper or copper alloy disposed on the barrier layer, an intermediate layer comprising copper nitride disposed on the copper conductive layer, and a capping layer disposed on the intermediate layer.