FBAR Stacked Mass-Load Structure for Higher Q Wave Reflection
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Solution Overview
Problem
Conventional film bulk acoustic resonators (FBARs) have a low quality factor due to poor reflection of mode wave energy other than the transverse Rayleigh Lamb (RL) wave, resulting in energy leakage.
Innovation Solution
The FBAR design includes a substrate, acoustic reflector, electrodes, and stacked components with misaligned edges and varying widths to effectively reflect S0, S1, A0, and A1 mode waves, increasing the quality factor by enhancing wave energy reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional FBAR design with a single mass load layer is used, then the structure is simple, but the reflection effect on mode wave energy other than transverse RL wave is poor, resulting in low quality factor
Solution Approach 1:
The patent divides the mass load layer into multiple stacked components (first mass load layer, second mass load layer, etc.) with different widths. Each layer is designed to reflect specific mode waves (S0, S1, A0, A1), thereby segmenting the reflection function across multiple layers to achieve comprehensive mode wave reflection and improve quality factor
Solution Approach 2:
Each mass load layer is assigned different local properties through varying widths and positions. The first mass load layer has a wider width for reflecting certain modes, while the second mass load layer has a narrower width for reflecting other modes. This local differentiation enables each layer to optimize reflection for specific wave modes, collectively improving overall reflection efficiency
2Loss of energy
If the mass load layer has a fixed width, then the manufacturing is simple, but it can only reflect specific mode wave energy, resulting in energy leakage
Solution Approach 1:
The energy reflection function is segmented across multiple stacked components with different widths. The first mass load layer reflects specific mode waves while the second mass load layer reflects other mode waves, collectively covering a broader spectrum of mode wave energy and minimizing energy leakage through comprehensive reflection
Solution Approach 2:
The patent changes the width parameter of successive mass load layers to optimize reflection for different mode waves. By varying the width parameter across layers (first layer wider, second layer narrower), the structure achieves broadband reflection coverage, reducing energy leakage across multiple wave modes
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 enhanced design achieves higher reflection efficiency of transverse wave energy, leading to a higher quality factor and reduced energy leakage, thereby improving the performance of FBARs.
Implementation Method 1
A FBAR, which has developed in recent years, is an advanced resonant technology that converts electrical energy into sound waves through the inverse piezoelectric effect of piezoelectric thin films to form resonance
Implementation Method 2
the mass load layer of at least two stacked components is enabled to reflect at least two of a S0 mode wave, a S1 mode wave, an A0 mode wave, and an A1 mode wave in the transverse RL wave
Data Source
AI summary
The present invention provides a FBAR, which includes a substrate, an acoustic reflector, a first electrode, a piezoelectric layer, a second electrode, and an etch-stop layer. The acoustic reflector is arranged on the substrate, the first electrode is arranged on a side of the substrate and covers the acoustic reflector, and at least a part of the piezoelectric layer is arranged on a side of the first electrode away from the substrate. The second electrode is arranged on a side of the piezoelectric layer away from the first electrode, and the etch-stop layer is arranged on a side of the second electrode away from the piezoelectric layer. The FBAR further includes at least two stacked components. At least an edge of each of the at least two stacked components is misaligned. The quality factor of the FBAR in the present invention is relatively high.