Multi-Layer Acoustic Wave Substrate for Spurious Mode Suppression
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Solution Overview
Problem
Acoustic wave devices with high impedance support substrates, such as polycrystalline spinel, experience spurious responses due to back reflections, which degrade frequency response and performance, and also suffer from thermal conductivity issues that can lead to high temperatures.
Innovation Solution
The use of a multi-layer substrate structure comprising a support substrate with high thermal conductivity, a ceramic layer like polycrystalline spinel, and a piezoelectric layer like lithium niobate, with direct bonding and optional temperature compensation layers, to scatter back reflections and improve thermal dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polycrystalline spinel substrate is used, then acoustic wave devices can be manufactured with good flatness and direct bonding capability, but spurious responses occur due to back reflections and thermal conductivity is insufficient leading to high temperatures
Solution Approach 1:
The substrate is divided into two separate layers: a polycrystalline spinel layer for bonding and flatness, and a support substrate (silicon, sapphire, or aluminum nitride) for thermal conductivity and acoustic performance. This segmentation allows each layer to fulfill its specific function without compromise.
Solution Approach 2:
The invention uses a composite substrate structure combining polycrystalline spinel with a high thermal conductivity material. The composite structure integrates the bonding advantages of spinel with the thermal and acoustic properties of the support substrate, eliminating both spurious responses and thermal issues.
2Ease of manufacture
If a polycrystalline spinel substrate is used, then manufacturing is simplified with direct bonding, but thermal dissipation is poor causing high chip temperatures
Solution Approach 1:
The substrate is divided into two separate layers: a polycrystalline spinel layer for bonding and flatness, and a support substrate (silicon, sapphire, or aluminum nitride) for thermal conductivity and acoustic performance. This segmentation allows each layer to fulfill its specific function without compromise.
Solution Approach 2:
The invention uses a composite substrate structure combining polycrystalline spinel with a high thermal conductivity material. The composite structure integrates the bonding advantages of spinel with the thermal and acoustic properties of the support substrate, eliminating both spurious responses and thermal issues.
3Device complexity
If a single layer piezoelectric substrate is used, then the structure is simple, but thermal dissipation is insufficient and spurious responses occur
Solution Approach 1:
The substrate is divided into two separate layers: a polycrystalline spinel layer for bonding and flatness, and a support substrate (silicon, sapphire, or aluminum nitride) for thermal conductivity and acoustic performance. This segmentation allows each layer to fulfill its specific function without compromise.
Solution Approach 2:
The invention uses a composite substrate structure combining polycrystalline spinel with a high thermal conductivity material. The composite structure integrates the bonding advantages of spinel with the thermal and acoustic properties of the support substrate, eliminating both spurious responses and thermal issues.
4Volume of moving object
If the piezoelectric layer is made thinner to reduce device size, then the device becomes more compact, but spurious responses increase and performance degrades
Solution Approach 1:
The invention uses a composite substrate structure combining polycrystalline spinel with a high thermal conductivity material. The composite structure integrates the bonding advantages of spinel with the thermal and acoustic properties of the support substrate, eliminating both spurious responses and thermal issues.
Solution Approach 2:
The invention optimizes the thickness parameters of both the piezoelectric layer and the spinel layer to achieve the desired balance between device compactness and performance. By carefully controlling these parameters, the device maintains good frequency response while achieving size reduction.
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 configuration suppresses spurious modes and reduces chip temperature, enhancing the frequency response and durability of the acoustic wave devices while maintaining thermal stability.
Implementation Method 1
the ceramic layer is arranged to scatter back reflections of the acoustic wave
Implementation Method 2
The support substrate has a higher thermal conductivity than the ceramic layer
Implementation Method 3
A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer
Data Source
AI summary
An acoustic wave device is disclosed. The acoustic wave device includes a support layer, a ceramic layer positioned over the support layer, a piezoelectric layer positioned over the ceramic layer, and an interdigital transducer electrode positioned over the piezoelectric layer. The support layer has a higher thermal conductivity than the ceramic layer. The ceramic layer can be a polycrystalline spinel layer. The acoustic wave device can be a surface acoustic wave device configured to generate a surface acoustic wave.