Piezoelectric Substrate Bonding Surfaces for Spurious Wave Suppression
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Solution Overview
Problem
Existing bonded bodies of piezoelectric material substrates and supporting substrates fail to effectively suppress spurious waves, despite adjustments to the convex-concave morphology of the bonding surfaces, as the suppression of these waves cannot be solely achieved by modifying the surface morphology.
Innovation Solution
A bonded body comprising a supporting substrate, a piezoelectric material substrate (such as lithium niobate, lithium tantalate, or their solid solution), and a bonding layer, where the bonding surfaces are characterized by specific X-ray reflectivity measurements, with a relative intensity of the reflected light approximated by the formula I = a(2θ) - b, within a range of 1.0×10−4 to 1.0×10−1, and coefficients a and b optimized to control the crystallographic and geometric characteristics for effective spurious wave suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the bonding surface is made a roughened surface by adjusting convex-concave morphology (RSm and Ra), then spurious wave suppression is improved, but manufacturing precision and surface quality deteriorate
Solution Approach 1:
The invention changes the measurement parameter from optical surface roughness (Ra, RSm) to X-ray reflectivity intensity, which can detect minute surface variations and crystallographic characteristics that optical methods cannot. This parameter change enables precise control of spurious wave suppression while maintaining manufacturing precision.
Solution Approach 2:
The invention replaces mechanical/optical surface measurement methods with X-ray reflectivity measurement. This substitution allows detection of surface characteristics at the atomic level, providing a new dimension for controlling spurious wave generation without compromising surface quality.
2Manufacturing precision
If the bonding surface is made a mirror surface, then manufacturing precision is improved, but spurious wave suppression deteriorates
Solution Approach 1:
The invention introduces a new measurement parameter (X-ray reflectivity intensity I) that can simultaneously characterize both surface flatness and spurious wave suppression capability. By controlling the intensity I to be 1.0×10^-4 or larger and 1.0×10^1 or smaller, the invention achieves both mirror surface quality and spurious wave suppression.
Solution Approach 2:
The invention adds a new dimension to surface characterization by using X-ray reflectivity instead of traditional optical methods. This new dimension reveals subtle surface characteristics and crystallographic features that are invisible to optical measurement, enabling simultaneous optimization of surface quality and spurious wave suppression.
3Object-affected harmful factors
If mechanical processing is applied to create a roughened surface, then spurious wave suppression is improved, but bonding strength and crystallinity deteriorate
Solution Approach 1:
The invention replaces mechanical surface processing with X-ray reflectivity-based surface characterization and control. This substitution eliminates the need for mechanical roughening that damages the surface, while still achieving spurious wave suppression through precise control of surface characteristics measured by X-ray reflectivity.
Solution Approach 2:
The invention introduces X-ray reflectivity measurement as an intermediary to characterize and control surface properties. This intermediary enables non-contact, non-destructive measurement and control of surface characteristics that affect spurious wave generation, without the need for mechanical processing that would compromise bonding strength.
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 described approach effectively suppresses spurious waves by controlling the surface characteristics through X-ray reflectivity measurements, ensuring the bonding surfaces are optimized for reduced spurious wave generation, with the coefficients a and b within specific ranges to enhance the bonding process and device performance.
Implementation Method 1
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
Implementation Method 2
a roughened surface introduced at the bonding interface is proposed to scatter the bulk wave and to suppress the unnecessary response
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 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=a(2θ)−b (1)(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.)