Piezoelectric Bonded Substrate Structure for Spurious Wave Suppression
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Solution Overview
Problem
Existing technologies fail to effectively suppress spurious waves in bonded bodies of piezoelectric material substrates and supporting substrates, despite adjustments to the convex-concave morphology of the bonding surface.
Innovation Solution
The bonding surface is processed to create a mirror surface followed by mechanical roughening, and spectral ellipsometry is used to analyze the phase difference of p-polarized and s-polarized light, optimizing the surface characteristics to achieve effective suppression of spurious waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the bonding surface is made roughened to scatter bulk wave, then spurious wave suppression is improved, but manufacturing precision and surface quality deteriorate
Solution Approach 1:
The patent applies local quality by creating a roughened surface only at the bonding interface between the piezoelectric substrate and supporting substrate, while maintaining smooth surfaces in other regions. This localized roughening scatters bulk waves at the bonding interface to suppress spurious waves without affecting the overall surface quality and manufacturing precision of the device.
Solution Approach 2:
The patent implements partial action by applying roughening treatment only to the bonding surface rather than the entire substrate surface. The roughened surface parameters (RSm ratio between 0.2-7.0 and Ra between 100nm-10μm) are optimized to provide sufficient bulk wave scattering while minimizing the affected area, thus maintaining manufacturing precision in non-bonding regions.
2Object-affected harmful factors
If mechanical processing is applied to create roughened surface, then spurious wave suppression is improved, but surface defects and film denaturing occur
Solution Approach 1:
The patent controls the roughening process parameters (abrasive grain size, processing depth, RSm ratio, Ra value) to achieve effective bulk wave scattering while minimizing film denaturing. By optimizing these parameters, the roughened surface provides spurious wave suppression with controlled impact on film integrity, balancing effectiveness and reliability.
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
By controlling the difference in phase differences of reflected light within specific ranges, the method significantly improves the suppression of spurious waves, enhancing the performance of acoustic wave devices.
Implementation Method 1
bulk wave is generated at the bonding interface so that unnecessary response is generated in transmission band and high frequency band. For preventing this, it is proposed that roughened surface in introduced at the bonding interface to scatter the bulk wave
Implementation Method 2
spectral ellipsometry is an analyzing method of measuring change of the polarized state of an incident light onto and that of the reflected light from a surface of a sample
Data Source
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Figure 3(a)~3(b)
AI summary
(Object) It is to provide a structure for suppressing spurious wave which cannot be suppressed by adjusting the surface morphology of a bonding surface of a piezoelectric material substrate or supporting substrate of a bonded body. (Solution) A bonded body includes a supporting substrate; a piezoelectric material substrate composed of a material selected from the group consisting of lithium niobate, lithium tantalate and lithium niobate-lithium tantalate; and a bonding layer bonding the supporting substrate and piezoelectric material substrate and contacting a main surface of the piezoelectric material substrate. Provided that at least one of a bonding surface of the supporting substrate and a bonding surface of the piezoelectric material substrate is measured by spectral ellipsometry and that Δ is assigned to a difference of phases of p-polarized light and s-polarized light of a reflected light, a difference of the maximum and minimum values of the difference Δ of the phases in a wavelength range of 400nm to 760nm is 70° or lower.