FBAR Piezoelectric Boundary Depolarization for Transverse Wave Suppression
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Solution Overview
Problem
Conventional thin film bulk acoustic resonators face energy dissipation issues due to transverse waves, leading to reduced Q factor and degraded device performance, as existing methods to suppress these waves are complex, costly, or affect the resonating region.
Innovation Solution
A thin film bulk acoustic resonator with a depolarized portion of the piezoelectric layer at the boundary of the acoustic reflection structure, achieved through ion implantation and annealing, effectively suppresses parasitic oscillations and energy dissipation via transverse waves, improving the Q factor and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If air gap is configured at boundary of cavity to reflect transverse waves, then energy dissipation is restrained, but manufacturing process becomes complicated and mechanical stability requirements increase
Solution Approach 1:
The patent extracts the piezoelectric layer material itself at the boundary region to form an acoustic reflection structure, eliminating the need for separate air gap structures. By removing piezoelectric material at the boundary, the structure inherently reflects transverse waves without requiring additional manufacturing steps for air gaps, thus reducing process complexity while maintaining energy reflection effectiveness
Solution Approach 2:
The patent introduces a mass loading layer as an intermediary structure at the boundary region. This layer serves as a mediator that provides acoustic impedance discontinuity to reflect transverse waves, replacing the need for complex air gap structures while simplifying the manufacturing process and reducing mechanical stability requirements
2Reliability
If grooves are formed on piezoelectric layer through etching to restrain transverse waves, then Q factor is improved, but lattice defects and micro-pores are induced affecting resonator performance
Solution Approach 1:
Instead of etching grooves into the piezoelectric layer, the patent extracts (removes) piezoelectric material at the boundary region to form the acoustic reflection structure. This approach avoids the harmful effects of etching such as lattice defects and micro-pores, while still achieving the goal of restraining transverse waves and improving Q factor
Solution Approach 2:
Rather than modifying the piezoelectric layer through etching (creating grooves), the patent inverts the approach by removing piezoelectric material at the boundary to create the reflection structure. This inverse approach eliminates the damaging etching process while achieving the desired acoustic reflection effect
3Loss of energy
If discontinuity of acoustic impedance is provided through mass loading layer, then transverse wave energy dissipation is restrained, but device complexity increases
Solution Approach 1:
The patent merges the mass loading layer with the boundary structure of the resonator, integrating the acoustic reflection function into the existing device architecture. This combination approach provides the necessary acoustic impedance discontinuity to restrain transverse waves while avoiding the need for separate, complex structures
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 depolarized portion enhances mechanical vibration intensity within the resonating region, suppressing parasitic oscillations and improving the Q factor, while simplifying manufacturing and reducing mechanical stability requirements compared to conventional methods.
Implementation Method 1
A main function of the piezoelectric layer is achieving conversion between electrical energy and mechanical energy. When an electrical field is applied between the upper electrode and the lower electrode of the FBAR, the piezoelectric layer converts electrical energy into mechanical energy, which exists in a form of acoustic waves.
Implementation Method 2
A portion which is of the piezoelectric layer and corresponds to a boundary of the acoustic reflection structure is depolarized to form a depolarized portion
Implementation Method 3
achieved through ion implantation and annealing
Data Source
AI summary
A thin film bulk acoustic resonator and a method for manufacturing the same. The thin film bulk acoustic resonator comprises a bottom electrode layer, a piezoelectric layer, and a top electrode layer, which are disposed on a substrate in which an acoustic reflection structure is located, where a portion which is of the piezoelectric layer and corresponds to a boundary of the acoustic reflection structure is depolarized to form a depolarized portion. The method comprises providing a bottom electrode layer on a substrate to cover an acoustic reflection structure which is formed or to be formed on the substrate; providing a piezoelectric layer on the bottom electrode layer; depolarizing a portion, which is of the piezoelectric layer and corresponds to a boundary of the acoustic reflection structure, to form a depolarized portion; and providing a top electrode layer on the piezoelectric layer.