IPD-FBAR Hybrid Filter Layout for High Roll-Off and Low Loss
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Solution Overview
Problem
Existing RF filters face challenges in achieving large bandwidth, poor roll-off, and difficulty in reducing size due to multiple capacitors and inductors in high-order LC circuits, while FBAR filters with AlN thin films face issues with increased acoustic wave propagation loss and decreased quality factor due to lattice stresses from doping.
Innovation Solution
A hybrid filter on a chip integrating IPD and FBAR is developed, involving a leakage isolation layer, inductor and capacitor layers, and BAW resonator, with specific materials and connections to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doping is applied to enhance piezoelectric property of AlN thin film, then piezoelectric coefficient is improved, but acoustic wave propagation loss increases and quality factor decreases
Solution Approach 1:
The patent changes the material parameter from pure AlN to AlScN by controlling the Scandium doping concentration. By optimizing the doping level, the patent achieves enhanced piezoelectric coefficient while managing the trade-off with acoustic wave propagation loss and quality factor, resolving the contradiction through precise parameter control.
Solution Approach 2:
The patent creates a composite material system AlScN by combining Aluminum Nitride with Scandium doping. This composite approach allows simultaneous improvement of piezoelectric properties while managing the negative effects through controlled composition, thereby enhancing overall filter performance without excessive energy loss.
2Reliability
If the number of capacitance and inductance is increased to improve roll-off of LC filter, then signal screening capability is improved, but filter size increases exponentially
Solution Approach 1:
The patent replaces the traditional mechanical LC filter structure with an FBAR-based acoustic wave filter. This substitution eliminates the need for multiple discrete capacitors and inductors, achieving high roll-off and signal screening capability through the acoustic resonance mechanism while dramatically reducing filter size and enabling integration.
Solution Approach 2:
The patent changes the fundamental operating principle from electrical resonance in LC circuits to acoustic wave resonance in FBAR. This parameter change in the filtering mechanism allows achieving superior roll-off performance with significantly fewer components and reduced physical footprint.
3Ease of manufacture
If traditional dielectric filters are used, then manufacturing is simple, but device size is too large for integration
Solution Approach 1:
The patent merges the FBAR resonator with the filter structure and integrates passive devices directly onto the same chip substrate. This consolidation achieves compact device size suitable for integration while maintaining manufacturing compatibility with existing semiconductor processes, resolving the contradiction between simplicity and miniaturization.
Solution Approach 2:
The patent transitions from planar dielectric filter structures to vertically stacked FBAR resonator structures with integrated passive devices. This dimensional change enables three-dimensional integration, achieving compact footprint while maintaining manufacturing feasibility through vertical stacking rather than horizontal expansion.
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 hybrid filter achieves high roll-off coefficients, low insertion loss, and miniaturization, addressing the limitations of traditional filters and FBARs.
Implementation Method 1
a piezoelectric layer, wherein the piezoelectric layer is between the bottom electrode and the top electrode
Data Source
AI summary
A method for preparing a hybrid filter on a chip with IPD and FBAR, includes: preparing a leakage isolation layer on a supporting substrate by deposition; obtaining an inductor layer on the leakage isolation layer, leaving a window at a bottom of a groove surrounding a cross section of a TGV inductor stack on a mask, and patterning an inductor metal simultaneously; forming a first insulating layer on the inductor metal, and forming lead through holes by photolithography; repeating steps and alternately to obtain a three-layer stacked TGV inductor; depositing a second insulating layer on the TGV inductor; depositing two capacitor layers on the second insulating layer, and depositing a third insulating layer between the two capacitor layers to form an MIM capacitor; and preparing a BAW resonator on the MIM capacitor, and connecting the TGV inductor, the MIM capacitor and the BAW resonator through the lead through holes.