Elastic Wave Device Plasma-Resistant Electrode Structure
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Solution Overview
Problem
Elastic wave devices with interdigital transducer electrodes suffer from deteriorated electrical characteristics when exposed to a plasma atmosphere, particularly due to damage to the outermost electrode layers such as Al or Cu films.
Innovation Solution
Incorporating a protective electrode layer with higher electric resistivity, made of materials like Ti or Mo, to cover the outermost electrode layers, including Al or Cu, which reduces the risk of damage and maintains the electrical characteristics even when exposed to plasma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the interdigital transducer electrode uses an outermost electrode layer made of Al or Cu to reduce resistance and loss, then the electrical characteristics are improved, but the electrode layer is damaged when exposed to plasma atmosphere, causing deterioration of electrical characteristics
Solution Approach 1:
A protective electrode layer made of Ti or Mo is introduced as an intermediary between the plasma environment and the outermost Al or Cu electrode layer. This protective layer has higher electric resistivity but provides a barrier that prevents plasma from directly contacting and damaging the low-resistivity outermost layer, thus maintaining both low electrical loss and reliability.
Solution Approach 2:
The interdigital transducer electrode is constructed as a composite multilayer structure combining materials with different properties: the outermost layer (Al or Cu) provides low electrical resistivity, while the protective layer (Ti or Mo) provides plasma resistance. This composite structure allows the electrode to simultaneously achieve low energy loss and high reliability under plasma exposure.
2Reliability
If a protective electrode layer with higher electric resistivity is added to protect the outermost electrode layer, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The electrode structure is segmented into functionally distinct layers: the outermost electrode layer for electrical conduction and the protective electrode layer for plasma resistance. This segmentation allows each layer to be optimized for its specific function while maintaining a relatively simple overall structure that can be fabricated using standard multilayer deposition techniques.
3Reliability
If the multilayer metal film is fully coated with the coating metal film to protect the electrode, then the reliability is improved, but the characteristics of the electrode deteriorate
Solution Approach 1:
The protective electrode layer is applied selectively to specific regions rather than uniformly coating the entire electrode surface. The protective layer covers the outermost electrode layer in areas exposed to plasma, while maintaining the low-resistivity characteristics of the Al or Cu outermost layer in electrical conduction paths, thus providing protection without compromising electrical performance.
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 protective electrode layer effectively shields the outermost electrode layers from plasma damage, preventing deterioration of the device's characteristics and maintaining optimal performance.
Implementation Method 1
a protective electrode layer protecting the outermost electrode layer, the protective electrode layer has a higher electric resistivity than the outermost electrode layer
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate and an interdigital transducer electrode provided on the piezoelectric substrate. The interdigital transducer electrode includes at least one electrode layer including an outermost electrode layer, and a protective electrode layer protecting the outermost electrode layer, the protective electrode layer has a higher electric resistivity than the outermost electrode layer, the outermost electrode layer includes a first principal surface located at a side opposite to the piezoelectric substrate side, and a side surface connected to the first principal surface, the first principal surface of the outermost electrode layer and a region extending from the first principal surface to at least a portion of the side surface are covered with the protective electrode layer, and the protective electrode layer does not extend beyond a lower edge of the side surface of the outermost electrode layer.