Multilayer Source Metal Pattern for Display Substrate RC Delay
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Solution Overview
Problem
Large-sized and high-resolution liquid crystal display apparatuses face issues with resistance-capacitance (RC) delay in metal lines, leading to defects such as high contact resistance and aluminum ion diffusion, which cause faulty channels and staining in display panels.
Innovation Solution
A display substrate with a source metal pattern having a multilayer structure, including a first lower pattern, a second lower pattern, and a low-resistance metal pattern, where the lower patterns are made of molybdenum or its alloys, and the low-resistance metal pattern is made of aluminum or its alloys, with an optional third lower pattern of nitrogen or molybdenum nitride, minimizing residual aluminum and enhancing the dense structure to prevent faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum material is used in metal lines to reduce RC delay, then resistance is reduced, but contact resistance increases and aluminum ions diffuse into silicon layer
Solution Approach 1:
The source metal pattern is divided into multiple layers: a lower pattern (molybdenum or molybdenum alloy) and an upper pattern (aluminum or aluminum alloy). This segmentation allows the lower layer to prevent aluminum ion diffusion while the upper layer provides low resistance, resolving the contradiction between reducing RC delay and preventing harmful aluminum ion effects.
Solution Approach 2:
The invention uses a composite metal structure combining molybdenum (or molybdenum alloy) and aluminum (or aluminum alloy) in a multilayer configuration. This composite approach leverages the low resistance of aluminum while using molybdenum as a barrier layer to prevent aluminum ion diffusion into the silicon layer, thus achieving both low RC delay and high reliability.
2Reliability
If aluminum material is used in metal lines, then resistance is reduced, but etchant damage occurs to the metal line
Solution Approach 1:
By segmenting the metal line into lower and upper patterns with different materials, the aluminum layer is protected from direct exposure to etchants during processing. The molybdenum lower layer serves as a protective barrier, allowing the aluminum upper layer to maintain low resistance without suffering etchant damage.
3Reliability
If multilayer structure is implemented for source metal pattern, then residual aluminum is minimized and faults are prevented, but device complexity increases
Solution Approach 1:
The source metal pattern is segmented into a lower pattern and an upper pattern with distinct materials and functions. This segmentation minimizes residual aluminum in the channel region, preventing faulty channels and staining, while the structured approach keeps the added complexity manageable and justified by the significant reliability improvement.
Data Source
AI summary
According to an exemplary embodiment, a display substrate includes a gate metal pattern comprising a gate electrode, an active pattern disposed on the gate pattern and a source metal pattern disposed on the active pattern. The source metal pattern includes a first lower pattern disposed on the active pattern, a second lower pattern disposed on the first lower pattern, a low-resistance metal pattern disposed on the second lower pattern, and an upper pattern disposed on the low-resistance metal pattern. The first lower pattern, the second lower pattern, and the upper pattern each include a material that is the same.