BAW Substrate Laser Diffusing Regions for Stable Frequency Response
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Solution Overview
Problem
The manufacturing of bulk acoustic wave (BAW) devices faces environmental burdens due to the need for rough grinding and subsequent etching to prevent elastic wave reflection, which degrades frequency characteristics.
Innovation Solution
The BAW device incorporates elastic wave diffusing regions formed within the substrate using a laser beam to scatter elastic waves, eliminating the need for rough grinding and etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rough grinding is performed on the substrate to form an uneven microstructure for diffusing elastic waves, then elastic wave diffusion is improved, but mechanical distortions are generated requiring additional etching processes
Solution Approach 1:
The patent replaces the mechanical grinding process with a laser-based optical process. The laser beam modifies the substrate to create an uneven microstructure for elastic wave diffusion without the mechanical contact that causes distortions. This substitution eliminates the need for subsequent etching to remove mechanical distortions, simplifying the manufacturing process while maintaining effective elastic wave diffusion.
Solution Approach 2:
The patent introduces laser-modified regions as an intermediary mechanism between the substrate and elastic waves. These regions, created by laser heating and melting, serve as the mediating structure that diffuses elastic waves without requiring direct mechanical intervention. The laser-modified regions act as a bridge that achieves the desired wave diffusion while avoiding the harmful effects of mechanical grinding.
2Reliability
If rough grinding and etching are used to prevent elastic wave reflection, then frequency characteristics are maintained, but environmental burdens increase
Solution Approach 1:
The patent replaces the mechanical-chemical manufacturing sequence (grinding followed by etching) with a purely optical laser process. This substitution maintains the functional outcome of elastic wave diffusion and frequency characteristic stability while eliminating the environmental burdens associated with mechanical grinding debris and chemical etching waste.
Solution Approach 2:
The patent converts the potential harm of laser processing (localized heating and material modification) into a beneficial outcome. By carefully controlling the laser parameters, the localized modification becomes the desired uneven microstructure that diffuses elastic waves, turning what could be a harmful side effect into the core functional feature of the device.
3Productivity
If the substrate is ground to thin it for BAW device manufacturing, then device integration is improved, but elastic wave reflection from the reverse side deteriorates frequency characteristics
Solution Approach 1:
The patent applies local quality modification to specific regions of the substrate using laser processing. Instead of uniformly thinning or modifying the entire substrate, the laser creates localized uneven microstructures at specific positions. These localized modifications are sufficient to diffuse elastic waves and prevent reflection, maintaining frequency characteristics while preserving the thin substrate design for device integration.
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 reduces environmental burdens and enhances frequency characteristics by effectively diffusing elastic waves without mechanical distortions, offering improved performance compared to traditional methods.
Implementation Method 1
irradiating a substrate with a piezoelectric element formed on a face side thereof with a laser beam having a wavelength that is transmittable to the substrate, from a reverse side of the substrate while the laser beam is being focused at a point within the substrate, thereby modifying the inside of the substrate
Implementation Method 2
the substrate has a plurality of elastic wave diffusing regions disposed therein for diffusing an elastic wave
Data Source
AI summary
A BAW device includes a substrate and a piezoelectric element formed on a surface of the substrate. The substrate has a plurality of elastic wave diffusing regions disposed therein for diffusing an elastic wave, the elastic wave diffusing regions being formed by modifying the inside of the substrate with a laser beam.