Piezoelectric Bulk Wave Electrode Layout With Silicon Orientation Control
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Solution Overview
Problem
Piezoelectric bulk wave devices experience unwanted bulk wave excitation and reflection, leading to ripples in frequency characteristics due to the orientation of silicon substrates, which affects the performance of acoustic wave filters.
Innovation Solution
A piezoelectric bulk wave device with a silicon substrate oriented at specific Euler angles (φ, θ, ψ) within certain ranges, specifically (10°+120°×n≤ψ≤50°+120°×n or 70°+120°×n≤ψ≤110°+120°×n, where n is any integer, to reduce or prevent unwanted bulk wave reflections and ripples in frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If paired electrodes are provided on a piezoelectric layer to excite bulk waves in thickness shear mode, then acoustic wave filtering function is achieved, but unwanted bulk waves are excited and reflected causing ripples in frequency characteristics
Solution Approach 1:
The patent changes the crystal orientation parameters of the silicon substrate, specifically setting the Euler angle ψ within specific ranges (10°≤ψ≤50° or 70°≤ψ≤110°) to control the elastic constants and piezoelectric coefficients. This parameter change suppresses the excitation of unwanted bulk waves while maintaining the desired thickness shear mode bulk wave operation, thereby eliminating ripples in frequency characteristics without sacrificing filtering performance
2Ease of manufacture
If wires connected to different potentials face each other, then electrical connection is achieved, but unwanted bulk wave signals are extracted by the wires
Solution Approach 1:
By changing the crystal orientation parameters (Euler angle ψ) of the silicon substrate, the patent modifies the coupling between electrical fields and acoustic waves. This parameter change reduces the efficiency of unwanted bulk wave signal extraction by the wires while maintaining proper electrical connections, thus suppressing harmful effects without compromising electrical functionality
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 proposed configuration effectively reduces or eliminates ripples in frequency characteristics by minimizing standing wave generation in the silicon substrate, thereby improving the reflection characteristics and reducing unwanted bulk wave signals.
Implementation Method 1
a piezoelectric layer on the support... By applying an AC voltage between the paired electrodes, bulk waves in the thickness shear mode are excited
Implementation Method 2
The unwanted bulk waves propagate in a thickness direction of the piezoelectric layer. Therefore, the unwanted bulk waves may be reflected in the support
Data Source
AI summary
A piezoelectric bulk wave device includes a piezoelectric substrate including a support including a silicon substrate and a piezoelectric layer on the support, first and second wire electrodes on the piezoelectric substrate, and a functional electrode on the piezoelectric layer, connected to at least one of the first and second wire electrodes, and including multiple electrodes. At least two of the first and second wire electrodes, and the multiple electrodes include first and second electrode films connected to different potentials. A plane orientation of the silicon substrate is (111), and ψ in Euler angles (ϕ, θ, ψ) of the silicon substrate is an angle within a range of about 10°+120°×n≤ψ≤about 50°+120°×n or about 70°+120°×n≤ψ≤about 110°+120°×n, where n is any integer.