PMUT Residual Stress and Patterning for Static Deflection Control
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Solution Overview
Problem
Existing PMUT designs face challenges in optimizing static deflection and vibration modeshape to enhance electromechanical transduction efficiency, signal-to-noise ratio, and linearity, due to complex interactions between residual stress and patterning.
Innovation Solution
The PMUT design involves a membrane with multiple layers, including electrode and piezoelectric layers, where a target residual stress is applied to one layer and patterning is used to remove portions of the layers, allowing for controlled static deflection and vibration modeshape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If residual stress and patterning are adjusted to optimize static deflection and vibration modeshape, then electromechanical transduction efficiency and signal-to-noise ratio are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies parameter changes by systematically varying residual stress levels and patterning geometries to optimize the static deflection and vibration modeshape of the PMUT membrane. By adjusting these parameters, the electromechanical transduction efficiency and signal-to-noise ratio are improved while maintaining control over the complex interactions between stress and patterning effects.
2Reliability
If residual stress and patterning are adjusted to optimize static deflection and vibration modeshape, then signal-to-noise ratio is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs preliminary action by pre-calculating and pre-designing the optimal combination of residual stress and patterning parameters before fabrication. This allows the static deflection and vibration modeshape to be predetermined, reducing the need for post-manufacturing adjustments and lowering the actual manufacturing precision requirements during production.
3Reliability
If complex patterning is applied to control vibration modeshape, then mechanical linearity is enhanced, but device complexity increases
Solution Approach 1:
The patent applies local quality by implementing specific patterning configurations in particular regions of the PMUT membrane to control the vibration modeshape and enhance mechanical linearity. Rather than uniformly complicating the entire device, localized patterning strategies are used to achieve the desired mechanical properties with minimal overall 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
This approach enables effective tuning of the vibration modeshape for improved performance characteristics such as increased electromechanical transduction efficiency, higher signal-to-noise ratio, and enhanced mechanical linearity.
Implementation Method 1
A PMUT device includes a membrane that generates an acoustic output signal based on an electrical signal applied across a piezoelectric material layer
Implementation Method 2
a first layer of the plurality of layers has a target residual stress... a predetermined shape of a static deflection of the membrane is determined by the target residual stress of the first layer
Data Source
AI summary
A piezoelectric micromachined ultrasonic transducer (“PMUT”) sensor has a target residual stress at one or more layers of the PMUT and also has patterning where some of the layers of the PMUT are removed. The residual stress and the patterning result in a static deflection of the PMUT. The application of the residual stress and the patterning define a vibration modeshape with desired acoustic characteristics such as improved signal-to-noise ratio (“SNR”).