TFT Array Panel with Nitrogen Diffusion Barrier for Copper Data Lines
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Solution Overview
Problem
Conductive materials with low resistivity, such as aluminum and copper alloys, used in thin film transistors (TFTs) for LCDs have weak chemical and physical properties, leading to decreased 'on' current and degraded image quality.
Innovation Solution
A TFT array panel design featuring a semiconductor layer with a Cu-Mn alloy data line, a diffusion barrier layer containing nitrogen, and a passivation layer, which includes a manganese oxide surface to enhance adhesion and prevent copper diffusion, along with a manufacturing method that forms these layers through a single photo exposure process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If low resistivity materials such as aluminum or copper alloys are used for gate lines and data lines, then signal delay is reduced, but the transistor may be ruined or on current decreases due to weak chemical or physical properties
Solution Approach 1:
A diffusion barrier layer is introduced as an intermediary between the copper-based data line and the semiconductor layer. This barrier layer prevents copper atoms from diffusing into the semiconductor layer while maintaining electrical conductivity, thus protecting the transistor from damage and maintaining reliable operation.
Solution Approach 2:
The data line is constructed as a composite structure with multiple layers: a copper-based alloy layer providing low resistivity for fast signal transmission, and a diffusion barrier layer preventing metal diffusion. This composite structure combines the advantages of both materials while mitigating their individual drawbacks.
2Reliability
If copper or copper alloys are used in transistors, then conductivity is improved, but chemical stability deteriorates leading to degraded image quality
Solution Approach 1:
The diffusion barrier layer acts as a protective intermediary that chemically isolates the copper-based data line from the semiconductor layer. This prevents unwanted chemical reactions and diffusion while allowing electrical current to pass through, thus maintaining both conductivity and chemical stability.
Solution Approach 2:
The harmful diffusion barrier function is extracted from the data line material itself and placed in a separate dedicated layer. This allows the data line to focus on providing low-resistivity electrical conduction while the separate barrier layer handles the chemical protection function.
3Reliability
If metal diffusion into semiconductor layer occurs, then current leakage increases, but using diffusion barrier adds manufacturing complexity
Solution Approach 1:
The diffusion barrier layer is formed using the same plasma treatment process as the ohmic contact layers, merging multiple functions into a single manufacturing step. This reduces process complexity while still providing the necessary diffusion barrier function to prevent current leakage.
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
The solution improves the image quality of LCDs by maintaining the conductivity of the data line while preventing metal diffusion into the semiconductor layer, thus minimizing current leakage and enhancing the stability of the TFTs.
Implementation Method 1
a diffusion barrier layer containing nitrogen formed on the first ohmic contact layer
Implementation Method 2
The diffusion barrier layer may be formed through the plasma treatment
Implementation Method 3
a manganese oxide surface to enhance adhesion and prevent copper diffusion
Data Source
AI summary
A thin film transistor array panel includes an insulating substrate. A gate line is formed on the insulating substrate and has a gate electrode. A gate insulating layer is formed on the gate line. A semiconductor layer is formed on the gate insulating layer and overlaps the gate electrode. Diffusion barriers are formed on the semiconductor layer and contain nitrogen. A data line crosses the gate line and has a source electrode partially contacting the diffusion barriers and a drain electrode partially contacting the diffusion barriers and facing the source electrode. The drain electrode is on the gate electrode. A pixel electrode is electrically connected to the drain electrode.