Piezoelectric Motor Silicon Substrate Cleavage Prevention
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Solution Overview
Problem
Piezoelectric driving devices with silicon substrates face mechanical strength issues due to the coincidence of shear force direction and cleavage direction, leading to substrate breakage and reduced device reliability in applications like motors, robots, and projectors.
Innovation Solution
Designing piezoelectric driving devices with silicon substrates where the cleavage direction and shear force direction do not coincide, and forming the substrates with angles greater than 20° to enhance mechanical strength, and applying oxide films to further increase substrate hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the cleavage direction of the silicon substrate coincides with the shear force direction, then the substrate is easier to manufacture and align with standard crystal orientations, but the mechanical strength decreases and substrate breakage occurs more frequently
Solution Approach 1:
The patent applies asymmetry by intentionally misaligning the substrate cleavage direction relative to the shear force direction. Specifically, the substrate is oriented such that the shear force acts at an angle (e.g., 45 degrees) to the cleavage direction rather than parallel to it, creating an asymmetric stress distribution that prevents cleavage plane formation while maintaining manufacturability through controlled crystal orientation selection.
2Device complexity
If the angle between cleavage direction and shear force direction is small, then the substrate structure is simpler, but the likelihood of substrate cleavage increases
Solution Approach 1:
The patent changes the critical parameter of angular orientation between the substrate cleavage direction and shear force direction. By setting this angle to specific values (e.g., 45 degrees or other optimized angles), the patent transforms the substrate's response to shear stress, preventing cleavage initiation while maintaining structural simplicity and avoiding complex multi-axis orientations.
3Device complexity
If oxide film is not formed on the substrate surface, then the manufacturing process is simpler, but the substrate is more prone to cleavage
Solution Approach 1:
The patent applies preliminary action by forming an oxide film on the substrate surface before the substrate is subjected to shear forces during operation. This pre-treatment modifies the surface properties, creating a compressive stress layer and altering the surface energy that inhibits cleavage initiation. The oxide film is formed in advance through standard semiconductor processing techniques, preventing future cleavage without adding operational complexity.
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 results in piezoelectric driving devices with higher mechanical strength, reduced likelihood of substrate breakage, and improved reliability in applications such as motors, robots, and projectors by preventing substrate cleavage during operation.
Implementation Method 1
a plurality of piezoelectric elements for driving are placed in the vibrating part. The plurality of piezoelectric elements are expanded and contracted at predetermined times, and thereby, the vibrating part is flexurally vibrated.
Implementation Method 2
an oxide film is formed on at least a part of a surface of the first substrate. With this configuration, regularity of the crystal in the surface of the first substrate is broken and the first substrate is even harder to be cleaved.
Data Source
AI summary
A piezoelectric driving device includes a first substrate having cleavability, and a piezoelectric element placed above the first substrate, wherein a cleavage direction of the first substrate and a direction in which a shear force is applied do not coincide in a plan view of the first substrate. Further, an angle formed by the cleavage direction of the first substrate and the direction in which the shear force is applied is equal to or larger than 20° in the plan view of the first substrate. Furthermore, the first substrate contains silicon single crystal.