Stacked BAW Resonators With Shared Reflector and Acoustic Isolation
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Solution Overview
Problem
Conventional Bulk Acoustic Wave (BAW) resonators typically accommodate only one piezoelectric coefficient, consuming significant device area and lacking cost-effective designs for implementing both series and shunt resonators.
Innovation Solution
A resonator structure featuring stacked resonators that share a common reflector, allowing for multiple piezoelectric coefficients without increasing bulk volume, with conductive or non-conductive reflectors connecting the resonators electrically or via external wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional solid mount BAW resonators are used with one piezoelectric layer, then the device structure is simple, but only one piezoelectric coefficient can be achieved and significant device area is consumed to implement both series and shunt resonators
Solution Approach 1:
The patent transitions from a planar arrangement of resonators to a vertical stacked configuration. Multiple resonators are arranged in the vertical dimension (z-axis) rather than spreading them horizontally, allowing multiple piezoelectric coefficients to be achieved within the same device footprint area.
Solution Approach 2:
The patent combines multiple resonators into a single integrated stack structure that shares common components (substrate, reflectors, electrodes). This merging approach allows multiple resonators with different piezoelectric coefficients to coexist in a compact configuration, reducing the total device area compared to separate resonator implementations.
2Adaptability or versatility
If multiple separate resonators are placed on one device die, then different piezoelectric coefficients can be achieved, but the device area consumption increases significantly
Solution Approach 1:
The patent merges multiple resonators into a shared stack structure where common components (substrate, bottom reflector, top reflector, electrodes) are shared among all resonators. This reduces device structure complexity compared to implementing multiple separate resonator structures, while still achieving different piezoelectric coefficients through different piezoelectric layer configurations within the stack.
Solution Approach 2:
The common reflectors and electrodes serve multiple functions simultaneously - they act as boundaries for acoustic waves for all resonators in the stack and provide electrical connections for multiple resonators. This multi-functionality reduces the overall device complexity while enabling multiple piezoelectric coefficients.
3Area of stationary object
If stacked resonators share a common reflector, then device area is reduced, but acoustic isolation between resonators must be maintained
Solution Approach 1:
The patent applies different acoustic impedance characteristics to different regions within the shared reflector structure. By creating localized acoustic boundary conditions through alternating high and low acoustic impedance layers, the design maintains effective acoustic isolation between resonators while allowing them to share the common reflector structure, thus reducing device area.
Solution Approach 2:
The common reflector is constructed as a composite structure with alternating layers of high acoustic impedance material and low acoustic impedance material. This composite configuration provides the necessary acoustic isolation between stacked resonators while maintaining a compact shared structure, enabling area reduction without compromising reliability.
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 significantly reduces device area requirements while enabling multiple piezoelectric properties, maintaining ease of implementation and cost-effectiveness.
Implementation Method 1
a first piezoelectric layer underneath the first top electrode
Implementation Method 2
alternating high acoustic impedance layers and low acoustic impedance layers residing vertically between the top common dielectric layer and the bottom common dielectric layer
Implementation Method 3
The first resonator and the second resonator are acoustically isolated from each other
Data Source
AI summary
The present disclosure relates to a resonator structure including stacked resonators, which share a same reflector. The disclosed resonator structure includes a first resonator and a second resonator, which is vertically stacked with the first resonator and shares a common reflector with the first resonator. Herein, the first resonator is at least composed of a first top electrode, a first piezoelectric layer underneath the first top electrode, and the common reflector underneath the first piezoelectric layer. The second resonator is at least composed of the common reflector, a second piezoelectric layer underneath the common reflector, and a second bottom electrode underneath the second piezoelectric layer. The first resonator and the second resonator are acoustically isolated from each other.