Sandwich Gate Electrode for Copper TFT Adhesion
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Solution Overview
Problem
Thin film transistor array substrates with copper gate electrodes face issues of poor adhesion to the substrate and copper ion migration, leading to defects such as peeling and contamination, and varying etching speeds during manufacturing result in trapezium structures that can cause short or open circuits.
Innovation Solution
A gate electrode structure with a sandwich configuration, comprising an adhesive layer and a barrier layer both having a central core made of the same material, with specific layer thicknesses and materials like titanium, molybdenum, and titanium nitride, to enhance adhesion and prevent copper ion migration, and uniform etching speeds are maintained by using a copper conductive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper gate electrode is used to decrease RC delay time, then electrical conductivity is improved, but adhesion to the substrate deteriorates and copper ion migration occurs
Solution Approach 1:
The gate electrode is constructed as a multi-layer composite structure comprising a copper layer for conductivity, a barrier layer (e.g., TiN, TaN) to prevent copper ion migration, and an adhesive layer (e.g., Ti, Mo, Cr, W) to enhance substrate adhesion. This composite structure resolves the contradiction by combining materials with different properties to simultaneously achieve low resistance, strong adhesion, and ion barrier functionality.
Solution Approach 2:
The barrier layer and adhesive layer serve as intermediary layers between the copper gate electrode and the substrate. These intermediary layers prevent direct contact between copper and the substrate, thereby blocking copper ion migration while maintaining electrical conductivity through the copper layer and providing mechanical adhesion through the adhesive layer.
2Object-affected harmful factors
If different materials are used for adhesive layer, barrier layer, and gate electrode layer to overcome copper defects, then adhesion and ion barrier are improved, but etching speed uniformity deteriorates
Solution Approach 1:
The patent applies local quality by making the adhesive layer and barrier layer have sandwich structures with central cores of the same material. This local uniformity in material composition ensures that etching proceeds at consistent speeds through the central regions of both layers, maintaining uniform gate electrode width while still providing different functional properties (adhesion and ion barrier) through the overall layered structure.
Solution Approach 2:
By using the same material for the central cores of both the adhesive layer and barrier layer, the patent introduces homogeneity into the etching process. This homogeneous material composition ensures uniform etching rates across the gate electrode structure, preventing the formation of trapezium shapes and maintaining precise gate electrode dimensions.
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 configuration improves adhesion, prevents copper ion contamination, and ensures uniform gate electrode width, reducing the risk of short or open circuits and maintaining the performance of the TFT array substrate.
Implementation Method 1
The adhesive layer 118 can enhance the adhesion between the gate electrode layer 116 and the substrate
Implementation Method 2
The barrier layer 114 can prevent copper ions from penetrating into an adjacent semiconductor layer
Data Source
AI summary
An exemplary thin film transistor array substrate (200) includes a substrate (210) and a gate electrode (220) formed on the substrate. The gate electrode includes an adhesive layer (226) formed on the substrate, a conductive layer (224) formed on the adhesive layer and a barrier layer (222) formed on the conductive layer, the adhesive layer and the barrier layer both have sandwich structures. A central core of the adhesive layer, the conductive layer, and a central core of the barrier layer are made of a same material.