Cavity spanning bottom electrode of a substrate-mounted bulk wave acoustic resonator
US6384697B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | May 8, 2000 |
| Grant date | May 7, 2002 |
| Priority date | — |
| Expiry date | May 8, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H9/585
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A filter formed of acoustic resonators, where each resonator has its own cavity and a bottom electrode that spans the entirety of the cavity, so that the bottom electrode has an unsupported interior region surrounded by supported peripheral regions. In the preferred embodiment, the cavity is formed by etching a depression into the substrate, filling the depression with a sacrificial material, depositing the piezoelectric and electrode layers that define an FBAR or SBAR, and then removing the sacrificial material from the depression. Also in the preferred embodiment, the sacrificial material is removed via release holes that are limited to the periphery of the depression. Preferably, the bottom electrode is the only electrode that spans the cavity, thereby limiting the formation of parasitic FBARs or SBARs. In one embodiment, the bottom electrode includes a serpentine edge that leaves a portion of one side of the cavity free of overlap by the bottom electrode, so that a top electrode may overlap this portion. Thus, the top and bottom electrodes can overlap the same side without sandwiching the piezoelectric layer outside of the unsupported interior region.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.