Three-Layer Passivation for Oxide TFTs
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Solution Overview
Problem
Conventional thin film transistor (TFT) devices with aluminum oxide passivation layers face challenges in processing difficulties and low yield due to the complexity of forming contact holes, which can damage the source and drain electrodes and lead to degradation of the oxide semiconductor channel layer.
Innovation Solution
A TFT device with a passivation layer composed of three layers: a first layer of silicon oxide, silicon nitride, or silicon oxynitride, a second layer of an aluminum compound, and a third layer of silicon oxide, silicon nitride, or silicon oxynitride, where the second layer acts as a barrier to prevent moisture and hydrogen ingress, and the layers are etched using dry and wet etching techniques to ensure high selectivity and prevent electrode damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer aluminum oxide passivation film is used, then the channel layer can be protected from moisture and hydrogen ingress, but the processing difficulty increases and the source/drain electrodes may be damaged during contact hole formation
Solution Approach 1:
The passivation film is divided into three distinct layers: a first inorganic insulating layer (silicon oxide or silicon nitride), a second aluminum oxide layer, and a third inorganic insulating layer (silicon oxide or silicon nitride). This segmentation allows each layer to perform its specific function - the aluminum oxide layer provides barrier protection while the silicon-based layers provide etch selectivity and protection during contact hole formation, thereby resolving the contradiction between protection and ease of manufacture.
Solution Approach 2:
The first and third inorganic insulating layers act as intermediary protective layers that facilitate the formation of contact holes through the aluminum oxide layer. These silicon-based layers have different etching characteristics compared to aluminum oxide, allowing selective etching processes that protect the underlying source/drain electrodes while still enabling effective barrier protection against moisture and hydrogen.
2Reliability
If a single-layer aluminum oxide passivation film is used, then barrier protection is provided, but the manufacturing yield decreases due to electrode damage
Solution Approach 1:
By segmenting the passivation film into three layers with different material compositions and etching characteristics, the manufacturing process becomes more controllable. The silicon-based outer layers can be selectively etched to form contact holes without damaging the aluminum oxide barrier layer and underlying electrodes, thereby maintaining high barrier protection while improving manufacturing yield.
Solution Approach 2:
The first and third inorganic insulating layers serve as cushioning protective layers that prevent direct contact between etching processes and the source/drain electrodes. These layers are formed beforehand to cushion and protect the electrodes during subsequent processing steps, preventing damage and improving manufacturing yield while maintaining the barrier function of the aluminum oxide layer.
3Reliability
If aluminum oxide layer characteristics and thickness are optimized for barrier protection, then channel layer protection improves, but contact hole formation becomes more difficult
Solution Approach 1:
The passivation film is segmented into layers with different etching characteristics. The aluminum oxide layer can be optimized for barrier protection with specific thickness and density, while the silicon-based outer layers provide contrasting etching properties that enable precise contact hole formation. This segmentation allows independent optimization of barrier protection and manufacturability without compromise.
Solution Approach 2:
By changing the material composition parameters of the passivation film layers, the etching selectivity is optimized. The silicon-based layers have different etching rates compared to aluminum oxide, allowing precise control of contact hole formation depth and shape. This parameter change enables the aluminum oxide layer to maintain optimal thickness for barrier protection while facilitating easy contact hole formation through selective etching processes.
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 enables high-yield manufacturing of TFT devices with improved electron mobility and reduced degradation of the oxide semiconductor channel layer, while maintaining excellent electrical characteristics and reliability.
Implementation Method 1
a second layer made of an aluminum compound... the second layer acts as a barrier to prevent moisture and hydrogen ingress
Implementation Method 2
the second layer acts as a barrier to prevent moisture and hydrogen ingress
Data Source
AI summary
A thin film transistor device including: a substrate; a gate electrode; an electrode pair composed of a source electrode and a drain electrode; a channel layer; and a passivation layer. The channel layer is made of an oxide semiconductor. The passivation layer includes a first layer, a second layer, and a third layer layered one on top of another in this order with the first layer closest to the substrate. The first layer is made of one of silicon oxide, silicon nitride, and silicon oxynitride, the second layer is made of an Al compound, and the third layer is made of one of silicon oxide, silicon nitride, and silicon oxynitride.