FBAR Resonator With Overlapping Polygonal Cavities
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Solution Overview
Problem
Conventional thin-film bulk acoustic resonators (FBARs) require a through-hole for sacrificial material removal, which weakens the electrode layers and affects device performance.
Innovation Solution
A FBAR design with overlapping polygonal cavities and a continuous acoustic resonance film that eliminates the need for a through-hole, using a semiconductor apparatus with dielectric layers, electrode layers, and a piezoelectric film, and a manufacturing method that integrates existing CMOS processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a through-hole is made to remove sacrificial material, then the sacrificial material can be removed by wet etching, but the integrity of the electrode layers and acoustic resonance film is weakened
Solution Approach 1:
The patent extracts the sacrificial material removal process from the main device structure by using a separate access hole in the substrate rather than penetrating the electrode layers and acoustic resonance film. This allows the sacrificial material to be removed while preserving the integrity of the critical device layers.
Solution Approach 2:
The patent introduces an intermediary substrate access hole as a mediator between the external environment and the buried sacrificial material. This intermediary pathway enables material removal without directly compromising the structural integrity of the electrode layers and acoustic resonance film.
2Ease of manufacture
If a through-hole is made to penetrate the upper electrode layer, acoustic resonance film, and lower electrode layer, then the sacrificial material can be accessed, but the device performance is adversely affected
Solution Approach 1:
The patent segments the access pathway from the device structure by creating a separate hole in the substrate that does not intersect with the electrode layers or acoustic resonance film. This segmentation isolates the manufacturing access requirement from the device performance-critical structures.
Solution Approach 2:
The patent extracts the access hole from the device stack, placing it laterally offset in the substrate rather than vertically through the device layers. This extraction eliminates the harmful intersection with performance-critical structures while maintaining manufacturing accessibility.
3Reliability
If the acoustic resonance film is made continuous without through-holes, then the resonance performance is enhanced, but the sacrificial material removal becomes more difficult
Solution Approach 1:
The patent resolves the contradiction by moving the access hole to a different spatial dimension - laterally in the substrate plane rather than vertically through the device stack. This dimensional repositioning allows the acoustic resonance film to remain continuous while still providing access to the sacrificial material through the substrate.
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
This design enhances resonance performance by maintaining the integrity of the acoustic resonance film and allowing better integration with CMOS fabrication processes.
Implementation Method 1
an acoustic resonance film that is positioned between and separating the first and the second cavities, wherein the acoustic resonance film includes a lower electrode layer, an upper electrode layer, and a piezoelectric film that is sandwiched between the lower and upper electrode layers
Data Source
AI summary
A thin-film bulk acoustic resonator (FBAR) apparatus includes a lower dielectric layer including a first cavity; an upper dielectric layer including a second cavity, wherein the upper dielectric layer is on the lower dielectric layer; and an acoustic resonance film that is positioned between and separating the first and the second cavities. The acoustic resonance film includes a lower electrode layer, an upper electrode layer, and a piezoelectric film that is sandwiched between the lower and upper electrode layers. A plan view of the first and the second cavities overlap to form an overlapped region having a polygonal shape without parallel sides.