MEMS Microphone Clamping Layer Design for Shock Robustness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS microphones are prone to fracture or failure due to shock or impact, primarily because the deflectable membrane is more susceptible to damage from such events, affecting their robustness and reliability.
Innovation Solution
A microfabricated structure is designed with a deflectable membrane supported by clamping layers, where the clamping layers have a smooth edge with minimal variation, and the membrane is arranged to deflect around the edge of the clamping layer, reducing peak tensile stress and enhancing robustness. The structure includes a cavity in the substrate and multiple clamping layers with specific perforation patterns to control the edge smoothness and stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a deflectable membrane is used in a capacitive MEMS microphone, then the microphone can transduce sound pressure waves effectively, but the membrane becomes more prone to fracture or failure from shock or impact
Solution Approach 1:
The patent introduces a compliant layer between the membrane and the rigid backplate electrode, positioned to compress during shocks or impacts. This compliant layer acts as a cushion that absorbs impact energy before it reaches the membrane, preventing fracture. The layer is strategically placed to provide protection in advance of potential damage, allowing the membrane to deflect safely during extreme events while maintaining normal acoustic function.
2Reliability
If the membrane is made more robust to withstand shocks, then reliability improves, but sensitivity to sound pressure waves may deteriorate
Solution Approach 1:
The patent applies local quality by making the compliant layer position-dependent rather than uniform throughout. The layer is strategically positioned in specific regions where it provides shock protection without interfering with the membrane's acoustic response. This localized approach allows the membrane to maintain high sensitivity to sound pressure waves in the acoustic operating range while gaining robustness against shocks and impacts in extreme conditions.
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 design significantly improves the robustness of MEMS microphones by reducing peak tensile stress during sound pressure waves, enhancing their ability to withstand shocks and loud sounds without damage, while maintaining sensitivity.
Implementation Method 1
Many MEMS devices use capacitive sensing techniques for transducing the physical phenomenon into electrical signals. The backplate electrode and the membrane form a parallel plate capacitor. The variation of the membrane in relation to the backplate electrode causes variation in the capacitance between the membrane and the backplate electrode. This variation in the capacitance is transformed into an output signal responsive to the movement of the membrane and forms a transduced signal.
Implementation Method 2
A position-dependent compliant layer is introduced between the membrane and the rigid backplate electrode, and positioned to compress during shocks or impacts, thereby reducing peak forces or stresses that would otherwise be transmitted to the membrane.
Data Source
AI summary
According to an embodiment, a microfabricated structure includes a cavity disposed in a substrate, a first clamping layer overlying the substrate, a deflectable membrane overlying the first clamping layer, and a second clamping layer overlying the deflectable membrane. A portion of the second clamping layer overlaps the cavity.