MEMS Microphone Cavity Etching Angle Control
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Solution Overview
Problem
The Bosch process for silicon etching in manufacturing silicon microphones results in a slow etching rate and fan-shaped structures that compromise mechanical stability, as it prioritizes speed over fan shape and size, particularly affecting the contact between etched silicon walls and structure layers.
Innovation Solution
A manufacturing method involving a substrate with a structural layer and a silicon-based layer, where a cavity hole is etched using the Bosch process, with a controlled included angle between the side wall and the structural layer of greater than 10° but less than 90°, enhancing the etching process through both main and over-etching cycles to achieve high verticality and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the Bosch process is used for silicon etching to increase etching speed, then productivity is improved, but the fan-shaped structure compromises mechanical stability
Solution Approach 1:
The patent applies parameter changes by modifying the etching process parameters, specifically controlling the included angle between the cavity hole side wall and structural layer to be between 10° and 90°. This angular parameter control transforms the fan-shaped structure into a more stable configuration while maintaining the Bosch process etching speed, thus resolving the contradiction between productivity and mechanical stability
Solution Approach 2:
The patent employs partial action by performing an over-etching process after the main etching. This additional etching step specifically targets the formation of the cavity hole with controlled side wall angle, allowing the main etching to proceed at high speed while the over-etching corrects the fan shape to ensure mechanical stability
2Productivity
If the Bosch process prioritizes etching speed over fan shape control, then productivity is improved, but manufacturing precision deteriorates
Solution Approach 1:
The patent segments the etching process into two distinct stages: main etching and over-etching. The main etching stage focuses on rapid material removal to achieve deep cavity holes efficiently, while the over-etching stage specifically addresses the fan shape control and side wall angle precision. This segmentation allows each stage to optimize for its specific function, resolving the contradiction between productivity and manufacturing precision
3Length of moving object
If deeper cavity holes are etched to improve microphone performance, then functionality is improved, but mechanical stability deteriorates due to fan shape
Solution Approach 1:
The patent applies preliminary action by performing the over-etching process after the main etching to specifically form the cavity hole with controlled side wall angle. This preliminary structural preparation ensures that even as the cavity hole depth increases, the side wall angle remains within the optimal 10° to 90° range, maintaining structural integrity throughout the deep etching process
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 method improves the mechanical stability and reliability of MEMS structures and silicon microphones by optimizing the etching process, allowing for deeper cavity holes and maintaining structural integrity.
Implementation Method 1
SF6 plasma etching silicon
Implementation Method 2
a C4F8 plasma deposition protection layer
Data Source
AI summary
The present invention provides a manufacturing method for MEMS structure. The method includes steps of: S1: providing a substrate, including a structural layer and a silicon-based layer overlapped with the structural layer; S2: carrying out a main etching process for etching out a cavity hole from an end of the silicon-based layer, which is far away from the structural layer, in a direction toward the structural layer until the cavity hole contacts the structural layer; and S3: carrying out an over-etching process for deepening the cavity hole and control an included angle α between a side wall of the cavity hole and the structural layer to be larger than 10° but smaller than 90°. The invention also provides a MEMS structural and a MEMS microphone manufactured by the method.