Molybdenum Alloy Protective Layer for Oxide Semiconductor TFT Etching
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Solution Overview
Problem
The etching process for forming source and drain electrodes in thin film transistors can damage the oxide semiconductor layer, leading to shifts in threshold voltage and deterioration of TFT performance.
Innovation Solution
A manufacturing method involving a molybdenum or molybdenum alloy conductive layer is used between the source and drain electrodes, which acts as a protective layer during etching, preventing damage to the oxide semiconductor layer by maintaining a gap and using different etching rates for the conductive layers to prevent the etching gas from reaching the semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etching process is performed to form source and drain electrodes, then electrodes are formed, but oxide semiconductor layer is damaged causing threshold voltage shift and TFT performance deterioration
Solution Approach 1:
A protective layer is introduced as an intermediary between the etching process and the oxide semiconductor layer. This protective layer is formed on the oxide semiconductor layer before etching, and it prevents direct contact between the etching gas and the semiconductor layer, thereby preventing damage while allowing the etching process to proceed for electrode formation.
Solution Approach 2:
The protective layer is formed in advance before the etching process. This preliminary action ensures that the oxide semiconductor layer is already protected when the etching gas is introduced, preventing threshold voltage shifts and performance deterioration before they can occur.
2Reliability
If protective layer is added between source and drain electrodes, then oxide semiconductor layer is protected from etching damage, but device structure becomes more complex
Solution Approach 1:
The protective layer is designed to serve multiple functions: it protects the oxide semiconductor layer during etching, and it also serves as part of the overall conductive structure. By making the protective layer have different etching rates compared to other conductive layers, it can be selectively removed or retained based on process conditions, reducing the need for additional separate protective layers.
Solution Approach 2:
The protective layer is designed with specific etching rate parameters that differ from other conductive layers. This parameter change allows selective etching where the protective layer can be removed after serving its protective function, or retained if beneficial, thereby simplifying the overall structure depending on the specific application requirements.
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 method effectively suppresses damage to the oxide semiconductor layer during etching, reducing unevenness in film thickness and stabilizing the threshold voltage, thereby improving the electric characteristics of the thin film transistor.
Implementation Method 1
forming a first conductive layer formed of molybdenum or a molybdenum alloy on the oxide semiconductor layer... preventing damage to the oxide semiconductor layer by maintaining a gap and using different etching rates for the conductive layers to prevent the etching gas from reaching the semiconductor layer
Implementation Method 2
forming a first conductive portion and a second conductive portion by performing dry etching of the second conductive layer using the resist mask
Data Source
AI summary
According to one embodiment, a manufacturing method of thin film transistor includes forming an oxide semiconductor layer on a first insulating film, forming a first conductive layer formed of molybdenum or a molybdenum alloy on the oxide semiconductor layer, forming a second conductive layer on the first conductive layer, forming a resist mask on the second conductive layer, and forming a first conductive portion and a second conductive portion by performing dry etching of the second conductive layer using the resist mask.