MEMS Backplate Elongated Protrusions Stiffness
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Solution Overview
Problem
Conventional MEMS microphones face challenges in increasing the rigidity of the backplate without compromising noise resistance and membrane spring constant, as thicker backplates increase perforation hole resistance and concentrated stress at anchor regions can lead to fractures under extreme pressure.
Innovation Solution
Incorporating elongated protrusions on the backplate, particularly at anchor regions, to enhance bending stiffness while maintaining a thin profile, which are fabricated in the same process as anti-sticking bumps, allowing for strategic thickness increases that triple the bending stiffness without affecting the entire backplate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the backplate thickness is increased to enhance rigidity, then the bending stiffness improves, but the noise resistance deteriorates due to increased perforation hole resistance
Solution Approach 1:
The patent applies local quality by adding elongated protrusions only at specific anchor regions of the backplate rather than uniformly increasing the entire backplate thickness. This localized thickening provides enhanced bending stiffness precisely where structural support is needed most, while maintaining thinner regions elsewhere to preserve low perforation hole resistance and good noise resistance.
2Strength
If the backplate thickness is increased to enhance rigidity, then the bending stiffness improves, but the manufacturing complexity increases
Solution Approach 1:
The patent merges the stiffening function with the existing anti-sticking bump fabrication process. The elongated protrusions are formed using the same sacrificial layer and recess formation steps already required for anti-sticking bumps, thereby integrating two functions into a single manufacturing flow without adding significant process complexity.
3Strength
If the backplate thickness is increased to enhance rigidity, then the bending stiffness improves, but the stress concentration at anchor regions worsens leading to potential fractures
Solution Approach 1:
The elongated protrusions are strategically positioned at anchor regions where stress concentration occurs. This localized thickening provides structural reinforcement precisely at the points of highest stress, distributing and reducing stress concentration while enhancing overall bending stiffness and preventing fracture propagation.
4Strength
If the entire backplate surface is thickened to enhance rigidity, then the bending stiffness improves, but the device size increases
Solution Approach 1:
Instead of uniformly thickening the entire backplate, the invention uses localized elongated protrusions only at critical anchor regions. This approach achieves the required bending stiffness enhancement while maintaining a compact overall device size, as the majority of the backplate surface remains thin.
Data Source
AI summary
MEMS devices with a rigid backplate and a method of making a MEMS device with a rigid backplate are disclosed. In one embodiment, a device includes a substrate and a backplate supported by the substrate. The backplate includes elongated protrusions.