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 comprising 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 form a mirror surface followed by mechanical roughening, and the microstructure is analyzed using the X-ray reflectivity method to optimize the crystallographic and geometric characteristics, thereby controlling the suppression of spurious waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the bonding surface is made roughened to suppress spurious waves, then the spurious wave suppression is improved, but the manufacturing precision and surface quality deteriorate due to mechanical processing defects
Solution Approach 1:
The invention applies local quality by creating a roughened surface only in the specific region where spurious wave suppression is needed, while maintaining high surface quality in other regions. The roughened surface is formed through selective mechanical processing (grinding or lapping) applied to the bonding surface of the piezoelectric substrate or supporting substrate, creating localized convex-concave structures with controlled morphology (RSm between 0.2-7.0 times the acoustic wave wavelength, Ra between 100nm-10μm) that suppress bulk wave generation without compromising overall manufacturing precision
Solution Approach 2:
The invention utilizes parameter changes by precisely controlling the morphological parameters of the roughened surface to achieve optimal spurious wave suppression. By adjusting the average length RSm of convex-concave structures and the arithmetic average roughness Ra to specific ranges, and by controlling the depth of roughening (0.1-10μm), the invention transforms the surface morphology parameters to eliminate bulk waves while maintaining manufacturing quality
2Object-affected harmful factors
If the convex-concave morphology of the bonding surface is adjusted to suppress spurious waves, then the spurious wave suppression is improved, but the effectiveness is insufficient when RSm values are the same
Solution Approach 1:
The invention addresses the limitation of single-parameter optimization by introducing additional dimensional control. Beyond controlling RSm (lateral scale), the invention controls Ra (vertical roughness) and the depth of roughening (z-dimension), creating a three-dimensional surface morphology control system. This multi-dimensional approach ensures that even when RSm values are similar, variations in Ra and roughening depth provide additional degrees of freedom to optimize spurious wave suppression effectiveness
Solution Approach 2:
The invention creates a composite surface structure by combining the base smooth surface with an overlay of convex-concave roughened features. This composite morphology, consisting of a smooth substrate with superimposed controlled roughness patterns, allows the surface to maintain both optical quality (for bonding) and acoustic wave suppression capabilities, achieving superior reliability compared to purely rough or purely smooth surfaces
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 effectively suppresses spurious waves by optimizing the surface characteristics, as evidenced by the reduction in spurious wave magnitude and the achievement of a stable bonding interface.
Implementation Method 1
According to the X-ray reflectivity method, X-ray is made incident onto a surface of a sample at an extremely low angle, and it is measured the X-ray intensity profile of reflected light reflected in the mirror direction of the incident angle
Implementation Method 2
it is proposed that roughened surface in introduced at the bonding interface to scatter the bulk wave and to suppress the unnecessary response
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~3(b)
AI summary
(Object) It is to provide a novel 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 the piezoelectric material substrate and contacting a main surface of the piezoelectric material substrate. It is 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 X-ray reflectivity method and that 1 is assigned to a signal intensity in the case of total reflection. A relative intensity I of a reflected light from the bonding surface is approximated by the following formula (1) in a range of 1.0×10-4 or larger and 1.0×10-1 or smaller. I=a2θ−b (θ represents an incident angle of an X-ray with respect to the bonding surface, a is 1.0×10-5 or larger and 2.0×10-3 or smaller, and b is 5.0 or larger and 9.0 or smaller.)