MEMS Piston Mass Consistency via Edge Etching
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Solution Overview
Problem
The dimensional consistency of miniature loudspeakers is compromised due to varying piston top thickness across different positions on a semiconductor wafer, leading to performance variations in transducers.
Innovation Solution
The process involves etching holes in thicker piston tops near the edge of the wafer to reduce mass uniformly, compensating for thickness variations by modifying the geometry, ensuring that mass differences are less than the variation in thickness, thereby maintaining consistent performance across different positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If piston tops are fabricated using standard MEMS processes on a semiconductor wafer, then production efficiency is improved, but thickness variation across different positions on the wafer causes mass inconsistency
Solution Approach 1:
The patent applies local quality by making the piston top structure non-uniform: thicker piston tops are placed near the center of the wafer while thinner piston tops are placed near the edge. This spatial variation in thickness compensates for the natural thickness gradient in MEMS fabrication, ensuring that all piston tops achieve consistent mass despite being fabricated using standard batch processes.
Solution Approach 2:
The patent changes the thickness parameter of piston tops based on their position on the wafer. By adjusting the thickness parameter locally (thicker at center, thinner at edge), the design compensates for fabrication variations and achieves uniform mass across all piston tops, resolving the contradiction between standard fabrication and precision requirements.
2Reliability
If piston top thickness is reduced to minimize mass, then transducer efficiency is improved, but dimensional consistency deteriorates due to greater thickness variation
Solution Approach 1:
The patent implements local quality by varying piston top thickness according to position: central piston tops are made thicker while peripheral piston tops are made thinner. This localized adjustment ensures that even with thin overall construction for efficiency, the mass remains consistent across all units, preventing dimensional inconsistency.
3Ease of manufacture
If uniform piston top thickness is specified across the wafer, then manufacturing simplicity is maintained, but performance variation increases due to mass inconsistency
Solution Approach 1:
The patent resolves this contradiction by applying local quality principles to the piston top design. Instead of uniform thickness, the design specifies different thicknesses for different wafer positions (thicker at center, thinner at edge). This maintains manufacturing simplicity using standard MEMS batch processes while achieving consistent mass and performance across all transducers.
Data Source
AI summary
A semiconductor wafer has formed within it a plurality of piston tops of equal area. Each of the piston tops includes a thin flat region from which a majority of the thickness of the original semiconductor wafer may have been removed. A first one of the piston tops has a lower thickness than a second one of the piston tops. The second piston top has at least one hole in it, the volume of the hole corresponding to the difference in thickness between the first and second piston tops, such that the masses of the first and second piston tops differ by less than the variation in thickness between them.