Multilayer IDT Electrode Buffer Layer for Thermal Stress Relief
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Solution Overview
Problem
Existing acoustic wave devices face reliability issues due to stress and electromigration caused by thermal expansion differences between layers in the interdigital transducer electrode, leading to potential damage and degradation.
Innovation Solution
Incorporating a buffer layer with a lower modulus of elasticity between the lower and upper layers of the interdigital transducer electrode to mitigate stress and prevent electromigration, using materials like titanium for the buffer layer to provide a transition and improve adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multilayer interdigital transducer electrode is used to improve electrical performance and adhesion, then electrical conductivity and mass loading are improved, but stress and electromigration occur due to thermal expansion differences between layers
Solution Approach 1:
A buffer layer is introduced between the lower layer and upper layer of the interdigital transducer electrode. This buffer layer acts as an intermediary that mitigates stress caused by thermal expansion differences between the lower layer (with lower temperature coefficient of expansion) and upper layer (with higher temperature coefficient of expansion), thereby preventing electromigration and improving device reliability
2Stress or pressure
If the buffer layer has a lower modulus of elasticity than the upper layer, then stress is effectively released, but the structural rigidity of the electrode is reduced
Solution Approach 1:
The buffer layer's modulus of elasticity is specifically controlled to be less than that of the upper layer (and optionally less than that of the lower layer) to optimize stress release. This parameter adjustment allows the buffer layer to deform more easily under thermal stress, protecting the interface between layers while maintaining sufficient overall structural integrity for device operation
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 buffer layer effectively reduces stress and enhances the reliability of the acoustic wave device by preventing cracks and improving electrical performance, thereby increasing the device's durability and efficiency.
Implementation Method 1
stress between the lower layer and the upper layer caused due to a difference between a coefficient of thermal expansion of the lower layer and a coefficient of thermal expansion of the upper layer
Data Source
AI summary
A temperature compensated surface acoustic wave device is disclosed. The temperature compensated surface acoustic wave device can include a piezoelectric layer, an interdigital transducer electrode over the piezoelectric layer, and a temperature compensation layer over the interdigital transducer electrode. The interdigital transducer electrode includes a first layer, a second layer over the first layer, and a buffer layer between the first layer and the second layer. A thermal conductivity of the second layer is greater than a thermal conductivity of the buffer layer. The buffer layer can be a titanium layer. A thickness of the buffer layer can be in a range of 20 nm to 200 nm, or in a range of 5% to 30% of a thickness of the interdigital transducer electrode.