Piezoelectric Substrate Bonding Surface for Spurious Wave Suppression
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Solution Overview
Problem
Existing bonded bodies of piezoelectric material substrates and supporting substrates struggle to effectively suppress spurious waves, as adjusting the convex-concave morphology of the bonding surfaces is insufficient in all cases.
Innovation Solution
A bonded body comprising a supporting substrate and a piezoelectric material substrate with a bonding layer, where at least one bonding surface is measured using spectral ellipsometry to ensure a phase difference of 70° or smaller between p-polarized and s-polarized light within the 400 nm to 760 nm wavelength range, and the surfaces are processed to create a mirror finish with a roughened microstructure to control spurious wave suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the bonding surface is roughened to suppress spurious waves, then the spurious wave suppression is improved, but the manufacturing precision and surface quality deteriorate
Solution Approach 1:
The invention changes the measurement parameter from surface morphology (RSm, Ra) to optical phase difference (Δ) measured by spectral ellipsometry. This parameter transformation allows evaluation of the bonding surface's effective crystallographic and geometric characteristics without directly controlling surface roughness, thereby suppressing spurious waves while maintaining manufacturing precision.
Solution Approach 2:
The invention replaces mechanical surface measurement methods (profilometry for RSm and Ra) with optical measurement method (spectral ellipsometry). This substitution enables detection of effective crystallographic characteristics through optical phase difference, avoiding the need to rely on surface morphology control and thus resolving the contradiction between spurious wave suppression and manufacturing precision.
2Object-affected harmful factors
If spectral ellipsometry is used to measure the bonding surface, then the spurious wave suppression is improved, but the measurement complexity increases
Solution Approach 1:
The invention introduces spectral ellipsometry as an intermediary measurement tool that indirectly evaluates the bonding surface's effective characteristics through optical phase difference. This intermediary approach provides more accurate information about the surface's acoustic wave scattering properties compared to direct surface morphology measurement, justifying the increased measurement complexity.
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 significantly improves the suppression of spurious waves by focusing on the effective crystallographic and geometric characteristics of the bonding surfaces, rather than just surface morphology, leading to enhanced performance in acoustic wave devices.
Implementation Method 1
a bonding layer bonding said supporting substrate and said piezoelectric material substrate
Implementation Method 2
a roughened surface be introduced at the bonding interface to scatter the bulk wave and to suppress the unnecessary response
Implementation Method 3
at least one of a bonding surface of said supporting substrate and a bonding surface of said 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
Data Source
AI summary
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. At least one of a bonding surface of the supporting substrate and a bonding surface of the piezoelectric material substrate, as measured by spectral ellipsometry with Δ being assigned to a difference of phases of p-polarized light and s-polarized light of a reflected light, has a difference of the maximum and minimum values of the difference Δ of the phases in a wavelength range of 400 nm to 760 nm of 70° or lower.