Quartz Crystal Resonator Wet Etching Orientation
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Solution Overview
Problem
The challenge lies in producing miniaturized inverted mesa-type quartz crystal resonator elements with high mass productivity while maintaining a large space for the resonating section and ensuring mechanical strength, as smaller elements face issues with etching residues and stress sensitivity, affecting frequency characteristics.
Innovation Solution
The solution involves using an AT-cut quartz crystal substrate with specific in-plane rotation angles to optimize the formation of thin and thick sections through wet etching, allowing for increased space and productivity, and incorporating electrode patterns to mitigate stress sensitivity and maintain mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet etching is used to produce smaller inverted mesa-type quartz crystal resonator elements, then mass productivity is improved, but etching residues form inclined faces that reduce the effective area of the thin resonating section
Solution Approach 1:
The patent applies parameter changes by rotating the quartz crystal substrate in-plane by specific angles (30°±5° or 45°±5°) relative to the standard AT-cut orientation. This rotation changes the crystallographic orientation parameters, which in turn changes the etching behavior and residue formation characteristics. By optimizing the rotation angle, the patent achieves a balance between maintaining large resonating section area and ensuring complete etching without excessive residues, thereby resolving the contradiction between mass productivity and manufacturing precision.
2Volume of moving object
If the quartz crystal resonator element is miniaturized, then device size is reduced, but the space for the thin resonating section is reduced and stress sensitivity increases
Solution Approach 1:
The patent uses parameter changes by rotating the substrate in-plane to optimize the distribution of etching residues. This rotation allows the thin resonating section to maintain a larger effective area even in miniaturized devices, as the residues are redistributed to less critical areas. The optimized orientation ensures that the resonating section retains sufficient space and mechanical strength despite the overall device miniaturization.
3Volume of moving object
If the excitation electrode size is reduced due to smaller resonating section, then device miniaturization is achieved, but stable signal extraction and sufficient energy trap cannot be expected
Solution Approach 1:
The patent applies parameter changes by rotating the substrate to optimize the resonating section geometry. This optimization ensures that even with reduced device size, the resonating section maintains sufficient area to support adequately sized excitation electrodes. The rotated orientation creates a configuration where the resonating section area is maximized relative to the device footprint, allowing excitation electrodes of sufficient size to be formed while maintaining overall device miniaturization and ensuring stable signal extraction.
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 results in a quartz crystal resonator element with enhanced mass productivity, increased resonating section space, and improved mechanical strength, while minimizing the impact of stress on frequency characteristics.
Implementation Method 1
wet etching of quartz crystal is influenced by crystallographic orientation of quartz crystal. When producing the inverted mesa-type quartz crystal resonator element, the etching rate varies depending on each crystal face appearing on an etched surface.
Data Source
AI summary
A quartz crystal resonator element includes an AT-cut quartz crystal substrate, the substrate having edges parallel to each of a Z″ axis obtained by rotating a Z′ axis in a range of −120° to +60° about a Y′ axis and an X′ axis perpendicular to the Z″ axis when an angle formed by rotating a +Z′ axis in a direction of a +X axis about the Y′ axis is a positive rotation angle; a thin section that forms a resonating section; and a thick section adjacent to the resonating section, the thin section and the thick section being formed on the quartz crystal substrate by wet etching. The thin section is formed either on a main surface of the substrate corresponding to a +Y′-axis side or on a main surface of the substrate corresponding to a −Y′-axis side. When the thin section is formed by the etching on the main surface of the +Y′-axis side, the thick section is provided at least a +Z″-axis-side end of the thin section, whereas when the thin section is formed by the etching on the main surface of the −Y′-axis side, the thick section is provided at least a −Z″-axis-side end of the thin section.