TFT Array Substrate Copper Ion Diffusion Barrier
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Solution Overview
Problem
The introduction of copper ions into the channel area of the active layer during the manufacturing of thin film transistor (TFT) array substrates degrades the characteristics and reliability of TFTs due to the multilayer structure of data lines and source/drain electrodes made of copper.
Innovation Solution
A method is developed to form data lines with a multilayer structure including a copper layer, while preventing copper ions from entering the active layer by using different masks for patterning the data lines and source/drain electrodes, ensuring that only the first metal layer is exposed to the channel area, thus maintaining the integrity of the active layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data lines and source/drain electrodes are formed with a multilayer structure including copper to reduce resistance, then electrical conductivity is improved, but copper ions are introduced into the active layer during patterning, degrading TFT reliability
Solution Approach 1:
The data line is divided into two separate metal layers: a first metal layer (non-copper) and a second metal layer (copper). This segmentation allows the copper layer to provide low resistance while the non-copper first metal layer acts as a barrier to prevent copper ion diffusion into the active layer during patterning processes.
Solution Approach 2:
Different portions of the data line structure are assigned different material properties: the first metal layer has copper-ion-blocking properties to protect the active layer, while the second metal layer has high conductivity properties to reduce resistance. This local differentiation of material qualities resolves the contradiction between conductivity and reliability.
2Productivity
If a single copper layer is used for data lines and source/drain electrodes, then manufacturing process complexity is reduced, but resistance remains high; if a multilayer structure is used, then resistance is reduced, but process complexity increases
Solution Approach 1:
The first metal layer and second metal layer are combined to form an integrated multilayer data line structure. This merging provides both the electrical conductivity benefits of copper and the manufacturing advantages of a unified structure, while the layered configuration enables selective exposure during patterning to maintain process efficiency.
3Ease of manufacture
If copper layer is exposed during patterning to form source/drain electrodes, then electrode formation is simplified, but copper ions diffuse into the active layer, degrading semiconductor characteristics
Solution Approach 1:
The first metal layer is formed as a preliminary barrier structure before the copper second metal layer is deposited. This preliminary action establishes a protective interface that prevents copper ion diffusion into the active layer during subsequent patterning operations, while still allowing simplified electrode formation processes.
Data Source
AI summary
A method for manufacturing a thin film transistor (TFT) array substrate having enhanced reliability is disclosed. The method includes forming a multilayer structure including at least one first metal layer and a second metal layer made of copper, forming a first mask layer including a first mask area corresponding to a data line and a second mask area corresponding to an electrode pattern to overlap with an active layer, patterning the multilayer structure, thereby forming the data line constituted by the multilayer structure, patterning the second metal layer, thereby forming the electrode pattern constituted by the at least one first metal layer, forming a second mask layer to expose a portion of the electrode pattern corresponding to a channel area of the active layer, patterning the at least one first metal layer, thereby forming source and drain.