FBAR Filter Trap-Rich Layer for Parasitic Conduction Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon-based FBAR filters suffer from parasitic surface conduction due to charge carrier displacement caused by signal voltage, leading to nonlinearity, insertion losses, and degraded signal purity and Q factor.
Innovation Solution
Incorporating a trap-rich layer, such as amorphous or polycrystalline silicon, between the silicon substrate and the buried oxide layer to trap charge carriers, thereby reducing their mobility and maintaining resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high resistivity silicon substrate is used for FBAR, then substrate isolation is improved, but parasitic surface conduction occurs due to charge carrier displacement
Solution Approach 1:
An intermediate layer (such as a trap-rich layer or dielectric layer with trapped charges) is introduced between the high resistivity silicon substrate and the FBAR structure. This intermediary layer prevents charge carrier displacement from reaching the substrate surface, thereby eliminating parasitic surface conduction while preserving the substrate isolation benefits of high resistivity silicon.
Solution Approach 2:
The invention utilizes the presence of charge carriers that would normally cause harm (parasitic conduction) and converts them into a beneficial trapped charge layer. By deliberately creating a layer with trapped charges that opposes the signal voltage-induced charge carrier displacement, the harmful effect is transformed into a protective mechanism that prevents parasitic conduction.
2Reliability
If charge carriers are allowed to move freely in the substrate, then electrical conductivity is maintained, but nonlinearity and insertion losses increase
Solution Approach 1:
An intermediate trap-rich layer is positioned between the substrate and the FBAR active structure to serve as a mediator. This layer captures and holds charge carriers that would otherwise move freely in response to signal voltage, preventing them from causing nonlinearity and insertion losses in the RF signal path.
Solution Approach 2:
The trap-rich layer is pre-formed in the substrate before FBAR fabrication or during the fabrication process. This preliminary action creates a reservoir of trapped charges that proactively counteracts charge carrier displacement before it can affect the FBAR performance, preventing nonlinearity and insertion losses.
3Ease of operation
If electric field is applied to the substrate interface, then charge carrier displacement occurs, but Q factor degradation results
Solution Approach 1:
The invention converts the harmful effect of electric field-induced charge carrier displacement into a beneficial trapped charge distribution. By creating a trap-rich layer that deliberately holds charges, the harmful displacement effect is transformed into a stable charge configuration that does not degrade the Q factor.
Solution Approach 2:
A trap-rich intermediate layer is introduced between the substrate and the FBAR structure to mediate the interaction between the applied electric field and charge carriers. This intermediary layer captures the charge carriers that would otherwise be displaced by the signal voltage, preventing Q factor degradation while allowing normal signal operation.
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 trap-rich layer effectively degrades carrier lifetimes, minimizing parasitic surface conduction and improving the Q factor and signal purity of the FBAR filter.
Implementation Method 1
This support layer has a trap region that degrades a carrier lifetime of a free charge carrier
Implementation Method 2
In piezoelectric-based resonators, acoustic resonant modes are generated in a piezoelectric material. The acoustic waves are converted into electrical signals for use in electrical applications.
Data Source
AI summary
An acoustic resonator forms a component of an FBAR filter that includes a trap-rich layer to avoid parasitic conduction by degrading carrier lifetimes of a free charge carriers. The acoustic resonator has a first electrode, a second electrode disposed parallel to the first planar portion and a piezoelectric layer disposed between and contacting both the first and second planar electrodes. A silicon-based a support layer is bonded to the second electrode and includes a trap region. The acoustic resonator may be manufactured by (a) depositing the trap region on the support layer; (b) oxidizing a surface of the trap region; (c) depositing a bonding layer on the oxidized surface of the trap region; (d) bonding a first electrode to the bonding layer; (e) contacting a first side of a piezoelectric layer to the electrode; and (f) contacting a second side of the piezoelectric layer a second electrode.