Integrated SAW-BAW Filter Structure for Q Factor and Temperature Stability
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Solution Overview
Problem
Current band filters, particularly those using SAW and BAW technologies, face challenges in achieving narrow transition bands with low losses and reduced bulk, while meeting stringent specifications for out-of-band rejection and temperature stability, especially as frequency bands become congested and standards require higher quality coefficients and larger bandwidths.
Innovation Solution
The co-integration of a BAW filter produced from monocrystalline piezoelectric material with a SAW filter on the same substrate, utilizing specific production processes and techniques like ion implantation and molecular bonding to achieve improved quality coefficients and independent optimization of each filter type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If monocrystalline piezoelectric material is used for BAW filter, then quality coefficient is improved, but manufacturing complexity increases
Solution Approach 1:
The device is divided into two distinct zones: a first zone containing the BAW filter with monocrystalline piezoelectric material for high quality coefficient applications, and a second zone containing the SAW filter with piezoelectric substrate for bandwidth-critical applications. This segmentation allows each filter type to be optimized independently while sharing a common substrate platform.
Solution Approach 2:
Both BAW and SAW filters are integrated on the same substrate, combining the advantages of monocrystalline material (high quality coefficient) with piezoelectric substrate technology (large bandwidth capability). This merging enables a single device to meet multiple telecommunications specifications that would be difficult to achieve with a single filter type.
2Ease of manufacture
If piezoelectric layers are deposited by sputtering, then manufacturing ease is improved, but bandwidth limitation occurs
Solution Approach 1:
Different regions of the device utilize different piezoelectric materials with locally optimized properties: the first zone uses monocrystalline piezoelectric material deposited by sputtering for high quality coefficient, while the second zone uses piezoelectric substrate providing large bandwidth. This local quality differentiation resolves the contradiction between manufacturing ease and bandwidth adaptability.
3Reliability
If surface metallizations are used for SAW filter, then coupling coefficient is improved, but thermal drift increases
Solution Approach 1:
The device segments the filtering function into two zones: the first zone uses BAW filter structure with monocrystalline material that provides both high coupling coefficient and better temperature stability, while the second zone uses SAW filter for bandwidth-critical functions. This segmentation allows thermal drift issues in SAW to be compensated by the temperature-stable BAW portion.
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 approach allows for enhanced performance and competitiveness by leveraging the advantages of both SAW and BAW filters, achieving better temperature compensation and higher quality coefficients, which is crucial for meeting the demanding specifications of modern telecommunications standards.
Implementation Method 1
utilizing specific production processes and techniques like ion implantation and molecular bonding
Implementation Method 2
utilizing specific production processes and techniques like ion implantation and molecular bonding
Implementation Method 3
using the piezoelectric properties of the materials
Implementation Method 4
acoustic wave filters
Data Source
Figure 1a~2
Figure 3
Figure 4a~4c
AI summary
An acoustic wave device comprising at least one surface acoustic wave filter and one bulk acoustic wave filter, the device including, on a substrate comprising a second piezoelectric material: a stack of layers including a first metal layer and a layer of a first monocrystalline piezoelectric material, wherein the stack of layers is partially etched so as to define a first area in which the first and second piezoelectric materials are present and a second area in which the first piezoelectric material is absent; a second metallization at the first area for defining the bulk acoustic wave filter integrating the first piezoelectric material, and a third metallization at the second area for defining the surface acoustic wave filter integrating the second piezoelectric material.