FBAR Top Electrode Separation to Suppress Secondary Resonances
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Solution Overview
Problem
Film bulk acoustic resonators (FBARs) suffer from energy loss due to lateral parasitic modes and secondary resonances, which degrade the Q and Rp values, and existing structural modifications to suppress these issues are challenging to implement without causing alignment offsets.
Innovation Solution
A bulk acoustic wave resonator design with a separated additional structure and a non-conductive material layer covering the top electrode and additional structure, forming a gap that electrically isolates the protrusion structure, thereby eliminating secondary resonances and improving Q and Rp values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a frame structure is connected to the top electrode to suppress lateral parasitic modes, then the leakage of acoustic waves is reduced, but secondary resonance is generated that affects filter performance
Solution Approach 1:
The frame structure is divided into two independent parts: the protrusion structure remaining connected to the top electrode for suppressing lateral parasitic modes, and the recess structure separated from the top electrode by a gap to eliminate secondary resonance. This segmentation allows each part to perform its specific function without interfering with the other.
2Object-generated harmful factors
If the frame structure is separated from the top electrode by a void structure to eliminate secondary resonance, then secondary resonance is suppressed, but the Rp value decreases and manufacturing becomes difficult due to alignment offsets
Solution Approach 1:
A dielectric layer is introduced as an intermediary material to fill the gap between the protrusion structure and the recess structure. This dielectric layer serves multiple functions: it maintains the separation needed to eliminate secondary resonance, provides mechanical support, and eliminates the alignment precision requirements that would be needed for a void structure.
3Object-generated harmful factors
If the frame structure is separated from the top electrode to eliminate secondary resonance, then filter performance is improved, but the Rp value of the resonator decreases
Solution Approach 1:
The frame structure is segmented into connected and separated portions, allowing the protrusion structure to remain connected for maintaining Rp value while the recess structure is separated to eliminate secondary resonance, achieving both goals simultaneously.
4Reliability
If a frame structure with protrusion and recess is provided to limit acoustic waves, then lateral parasitic mode leakage is suppressed, but the device complexity increases
Solution Approach 1:
The frame structure is segmented into functional portions (protrusion and recess structures) with different connectivity to the top electrode, allowing each segment to perform its specific function independently while simplifying the overall design compared to a fully connected complex frame.
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 design effectively suppresses secondary resonances and parasitic modes, enhancing the resonator's performance by maintaining high Q and Rp values while preventing alignment offsets during processing.
Implementation Method 1
the FBAR converts the input electrical signal into mechanical resonance by using an inverse piezoelectric effect
Implementation Method 2
converts the mechanical resonance into an electrical signal for output by using a piezoelectric effect
Implementation Method 3
a non-conductive material layer covering the top electrode and the additional structure, forming a gap that electrically isolates the protrusion structure
Data Source
Figure 1(A)~1(B)
Figure 2(A)~2(B)
Figure 2(C)~3
AI summary
The present disclosure relates to a bulk acoustic resonator, comprising a substrate, an acoustic mirror, a bottom electrode provided above the substrate, a top electrode having an electrode connection portion, and a piezoelectric layer provided above the bottom electrode and between the bottom electrode and the top electrode. The resonator further comprises an additional structure provided at an edge of the top electrode, and there is a gap between the top electrode and the additional structure. The resonator further comprises a non-conductive material layer which fills the gap and covers at least part of the additional structure and/or at least part of the top electrode. The present disclosure also relates to an electronic device having a semiconductor device.