BAW Resonator Structure With Integrated Capacitance Saving Chip Area
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Solution Overview
Problem
Existing BAW resonators face challenges in minimizing size and cost due to the requirement for additional space for 'on-chip' capacitances, which affects their overall performance and efficiency in micro-acoustic components like RF filters.
Innovation Solution
Incorporating a dielectric layer between the bottom electrode and an additional electrode, which provides additional capacitance without increasing the resonator's size, using a dielectric material with high relative dielectric permittivity, and configuring the electrodes to decouple the capacitance from the resonator functionality, allowing for efficient use of space and maintaining operational resonance frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If additional space is allocated for on-chip capacitances in BAW resonators, then the required capacitance values can be achieved, but the overall size of the resonator increases
Solution Approach 1:
The patent changes the dielectric permittivity parameter by introducing a dielectric layer with high relative dielectric permittivity (epsilon_r >= 10) between the bottom electrode and the substrate. This parameter change allows achieving the required capacitance values with a significantly reduced physical area, as capacitance is directly proportional to dielectric permittivity. The high permittivity material enables compact resonator design while meeting the capacitance requirements for pole generation and shifting in RF filters.
Solution Approach 2:
The patent employs a composite structure combining the piezoelectric layer, bottom electrode, and dielectric layer with high permittivity material. This composite arrangement integrates multiple functions: the piezoelectric layer provides resonator functionality, the bottom electrode serves as both an electrical contact and part of the capacitance structure, and the dielectric layer with high permittivity provides the additional capacitance in a compact form factor. This composite material approach resolves the contradiction by achieving high capacitance density without increasing overall resonator size.
2Quantity of substance
If a dielectric layer with high relative dielectric permittivity is introduced to provide additional capacitance, then the capacitance density increases and space is minimized, but the complexity of the resonator structure increases
Solution Approach 1:
The bottom electrode in the patent serves multiple functions: it acts as an electrical contact to the piezoelectric layer, forms part of the resonator structure, and together with the dielectric layer and substrate, creates the additional capacitance for pole generation. This multi-functionality reduces the need for separate dedicated capacitance structures, thereby minimizing the increase in device complexity while achieving high capacitance density through the high permittivity dielectric layer.
3Area of stationary object
If the dielectric layer thickness is reduced to minimize space, then the resonator size is minimized, but the capacitance value may be insufficient
Solution Approach 1:
The patent compensates for the reduced dielectric layer thickness by significantly increasing the dielectric permittivity parameter. Since capacitance is proportional to both the dielectric permittivity and the inverse of thickness, using materials with high permittivity (epsilon_r >= 10) allows achieving the required capacitance values even with thin dielectric layers. This parameter change enables simultaneous minimization of resonator size and maintenance of sufficient capacitance value.
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 solution enables the achievement of required capacitance values with minimal additional space, maintaining high resonance frequencies and operational efficiency, while allowing for flexible electrode configurations that optimize space usage and performance in RF filters.
Implementation Method 1
The dielectric layer, the bottom electrode and the additional electrode are configured to provide an additional capacitance in the resonator
Implementation Method 2
a piezoelectric layer located between a top electrode and a bottom electrode
Data Source
AI summary
A filter comprising first and second BAW resonators. The first BAW resonator having a piezoelectric layer, located between a top electrode and a bottom electrode, and a dielectric layer located between the bottom electrode and an additional electrode. Wherein the dielectric layer, the bottom electrode and the additional electrode are configured to provide an additional capacitance in the resonator. The second BAW resonator having at least one less electrode than the first BAW resonator.