Bulk Acoustic Wave Resonator Shape Control Layer
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Solution Overview
Problem
Bulk acoustic wave resonators experience deteriorated mechanical and electrical characteristics due to friction between the resonating part and the substrate, leading to compromised frequency characteristics and noise across the resonator's frequency domain.
Innovation Solution
A bulk acoustic wave resonator device is designed with a shape control layer applied over the edge of a cavity between the substrate and the lower electrode, featuring tensile stress to prevent contact between the resonating part and the substrate, using materials like copper, nickel, or chromium, and polymer resin composites, ensuring the shape control layer does not protrude outside the cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a membrane-type resonator with a cavity below the resonating part is used, then the resonator structure is improved for acoustic wave generation, but mechanical and electrical characteristics deteriorate due to friction between the resonating part and substrate
Solution Approach 1:
A shape control layer is introduced as an intermediary element between the resonating part and the substrate. This layer actively controls the shape of the resonating part to maintain a gap between it and the substrate, preventing direct contact and friction while preserving the membrane-type resonator's acoustic wave generation capabilities
Solution Approach 2:
The patent applies tensile stress to the shape control layer during formation, which changes the physical parameters of the layer. This stress state enables the shape control layer to effectively maintain the resonating part's shape and prevent contact with the substrate, thereby improving mechanical and electrical characteristics
2Ease of manufacture
If the resonating part and substrate are closely in contact during manufacturing, then manufacturing is simplified, but frequency characteristics are deteriorated and noise occurs across the resonator
Solution Approach 1:
The shape control layer is formed with predetermined tensile stress before the resonator is fully assembled and operated. This preliminary action of pre-stressing the shape control layer ensures that the resonating part maintains the correct shape and gap from the beginning, preventing contact-related frequency deterioration and noise
Solution Approach 2:
The shape control layer serves as a mediator that decouples the manufacturing simplicity of close contact from the performance requirements of gap maintenance. It allows the resonating part to be positioned close to the substrate during manufacturing while still preventing actual contact that would degrade frequency characteristics
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 solution effectively suppresses contact between the resonating part and the substrate, maintaining optimal frequency characteristics and reducing noise, while allowing for controlled deformation of the resonating part to prevent permanent contact and enhance performance.
Implementation Method 1
tensile stress is applied to the shape control layer during formation of the shape control layer
Implementation Method 2
residual stress remains in the shape control layer
Implementation Method 3
bulk acoustic wave resonators, which have electrodes with large acoustic impedance disposed on both sides thereof and a piezoelectric material disposed therebetween, in order to generate an acoustic wave in a thickness direction of the resonator
Data Source
AI summary
A bulk acoustic wave resonator device includes: a substrate; a lower electrode disposed on the substrate; a piezoelectric layer disposed over a portion of the lower electrode; an upper electrode disposed on the piezoelectric layer; and a shape control layer covering an edge of a cavity disposed between the substrate and the lower electrode, wherein tensile stress is applied to the shape control layer during formation of the shape control layer.