BAW Temperature Compensation Layer for Smaller Stable Filters
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Solution Overview
Problem
Existing surface acoustic wave devices suffer from performance degradation due to large temperature coefficient of frequency (TCF), which affects their temperature stability and efficiency, and the use of silicon dioxide as a temperature compensation layer increases device size and cost.
Innovation Solution
Incorporating a temperature compensation structure with materials like germanium oxide, which has lower acoustic velocity and higher permittivity than silicon oxide, reduces acoustic velocity and enhances temperature stability while allowing for a smaller device footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If silicon dioxide is used as a temperature compensation layer, then temperature stability is improved, but device size and cost increase
Solution Approach 1:
The patent changes the material parameter from silicon dioxide to germanium oxide, which has different physical properties (lower acoustic velocity, higher permittivity). This parameter change allows achieving the same temperature compensation function with a thinner layer, thus reducing device size while maintaining temperature stability.
Solution Approach 2:
The patent uses germanium oxide as a composite material alternative to silicon dioxide. The germanium oxide layer is configured with specific thickness parameters to provide temperature compensation while occupying less space, effectively resolving the contradiction between temperature stability and device size.
2Area of stationary object
If germanium oxide is used as a temperature compensation layer, then device size is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent specifies precise thickness parameters for the germanium oxide layer (300 nm to 800 nm, or 0.1L to 0.2L where L is wavelength) to optimize both device size and manufacturability. These parameter ranges balance the need for compactness with the feasibility of standard fabrication processes.
3Stability of the object's composition
If germanium oxide layer thickness is increased, then temperature stability is improved, but acoustic velocity increases
Solution Approach 1:
The patent carefully controls the germanium oxide layer thickness within specific ranges (300 nm to 800 nm, or 0.1L to 0.2L) to achieve optimal temperature stability while limiting the increase in acoustic velocity. This parameter optimization resolves the contradiction by finding the sweet spot where temperature compensation is effective but acoustic velocity remains controlled.
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 use of germanium oxide as a temperature compensation layer improves temperature stability and reduces device size, maintaining high coupling coefficients and static capacitance, thus enhancing the performance and cost-effectiveness of surface acoustic wave devices.
Implementation Method 1
a temperature compensation structure between the support substrate and the piezoelectric layer, the temperature compensation structure including a germanium oxide layer
Implementation Method 2
a piezoelectric layer over the support substrate; an interdigital transducer electrode in electrical communication with the piezoelectric layer
Data Source
AI summary
A bulk acoustic wave device is disclosed. The bulk acoustic wave device can include a first electrode, a second electrode, a piezoelectric layer positioned between the first electrode and the second electrode, and a temperature compensation structure in thermal communication with the piezoelectric layer. The temperature compensation structure includes a material that has a lower acoustic velocity and higher permittivity than silicon oxide.