Gradient SiOx Bonding Layer for Piezoelectric Joint Strength and Q Value
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Solution Overview
Problem
Existing bonded bodies of piezoelectric single crystal substrates and supporting substrates face challenges in achieving high bonding strength and Q value, leading to peeling issues and reduced performance in acoustic wave devices due to difficulties in bonding with high-resistance layers.
Innovation Solution
A bonded body comprising a supporting substrate of polycrystalline or monocrystalline material, a piezoelectric single crystal substrate, and a bonding layer with a Si(1-x)Ox composition, where the oxygen ratio varies from the piezoelectric substrate to the supporting substrate, with specific ranges for maximum and minimum oxygen ratios to enhance insulating properties and bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the insulating property of the bonding layer is improved by raising electric resistance, then noise and loss are reduced, but bonding strength decreases causing peeling between substrates
Solution Approach 1:
The bonding layer is designed with a non-uniform oxygen ratio distribution, where the oxygen ratio varies from the piezoelectric substrate interface to the supporting substrate interface. This creates local property variations: regions with different oxygen ratios provide different combinations of insulating properties and bonding strength, allowing the layer to simultaneously reduce noise/loss while maintaining strong adhesion to both substrates.
Solution Approach 2:
The oxygen ratio in the bonding layer is changed as a continuous parameter across the layer thickness. By controlling the oxygen ratio to vary from one interface to the other, the electrical resistance and bonding characteristics are tuned locally, achieving high insulating property where needed while maintaining bonding strength at the interfaces.
2Reliability
If a bonding layer with high electric resistance is used, then insulating property is improved, but peeling occurs during subsequent processing steps
Solution Approach 1:
Different regions of the bonding layer have different oxygen ratios tailored to their specific functions: regions closer to one substrate may have oxygen ratios optimized for bonding strength, while regions closer to the other substrate have oxygen ratios optimized for insulating properties. This local optimization prevents peeling while maintaining high insulation.
Solution Approach 2:
The bonding layer functions as a composite structure with varying composition (oxygen ratio) throughout its thickness. This compositional gradient creates a material that exhibits both high insulating properties and strong bonding stability, combining characteristics that would be mutually exclusive in a uniform material.
3Object-affected harmful factors
If the oxygen ratio in the bonding layer is increased, then insulating property is improved, but bonding strength to the piezoelectric substrate decreases
Solution Approach 1:
The oxygen ratio is not uniformly increased throughout the bonding layer but is instead distributed non-uniformly. The region adjacent to the piezoelectric substrate maintains a lower oxygen ratio for strong bonding, while regions farther from the substrate have higher oxygen ratios for improved insulation, thus resolving the trade-off between bonding strength and insulating property.
Solution Approach 2:
Instead of varying the oxygen ratio in a single uniform value, the solution introduces a spatial dimension to the oxygen ratio distribution. The oxygen ratio becomes a function of position within the bonding layer, allowing independent optimization of bonding strength at one interface and insulating property at another interface along the thickness direction.
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 solution significantly improves the bonding strength and Q value of the acoustic wave device by increasing the insulating property of the bonding layer, reducing noise and loss, and preventing peeling, thereby enhancing the device's performance.
Implementation Method 1
improve the insulating property by raising the electric resistance of the bonding layer
Implementation Method 2
bonding layer has a composition of Si(1-x)Ox wherein the oxygen ratio is increased or decreased from an end part of the bonding layer on a side of the piezoelectric single crystal substrate to an end part of the bonding layer on a side of the supporting substrate
Data Source
AI summary
A bonded body includes a supporting substrate composed of a polycrystalline ceramic material or monocrystalline material, a piezoelectric single crystal substrate and a bonding layer provided between the supporting substrate and piezoelectric single crystal substrate. The bonding layer has a composition of Si(1-x)Ox (x represents an oxygen ratio). The oxygen ratio is increased or decreased from an end part of the bonding layer on the side of the piezoelectric single crystal substrate to an end part of the bonding layer on the side of the supporting substrate. The maximum value of the oxygen ratio x in the bonding layer is 0.013 or higher and 0.666 or lower, and the minimum value of the oxygen ratio is 0.001 or higher and 0.408 or lower.