MEMS Sensor Fabrication via Grounded Via Structures
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Solution Overview
Problem
Conventional MEMS devices face challenges in improving performance, reducing size, and decreasing cost, while also requiring more complex microsystems with greater computational power, and suffer from etching defects and reliability issues due to lack of grounding in the etching process.
Innovation Solution
The method involves forming a via structure with a ground post within the MEMS layer to connect conductive moving structures to the substrate, improving the etching process and adding a capping layer with stoppers to prevent excessive deflection under external pressure, resulting in well-defined edges and enhanced reliability of MEMS structural components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used to pattern MEMS structures, then manufacturing simplicity is maintained, but etching defects and poor edge definition occur
Solution Approach 1:
The patent applies preliminary action by forming via structures with ground posts before the plasma etching process. These pre-formed conductive structures provide grounding during etching, which prevents charging effects and improves edge definition. The via structures are created in advance to establish electrical pathways that will control the etching process behavior.
Solution Approach 2:
The via structures with ground posts serve as intermediaries between the plasma etching process and the substrate. These structures mediate the charging effects during etching by providing localized grounding, thereby improving the etching profile without requiring fundamental changes to the plasma process itself.
2Length of moving object
If MEMS devices are made smaller to reduce size, then device miniaturization is achieved, but reliability and performance improvement becomes more challenging
Solution Approach 1:
The patent applies parameter changes by modifying the electrical parameters during fabrication - specifically by introducing grounded via structures that change the electrical field distribution during plasma etching. This controls the etching rate and profile parameters, enabling better definition in smaller structures while maintaining reliability.
3Reliability
If conventional fabrication processes are used, then manufacturing simplicity is maintained, but long-term reliability is compromised due to lack of grounding
Solution Approach 1:
The patent implements preliminary action by pre-forming grounded via structures before the critical plasma etching step. This preliminary grounding structure formation ensures proper electrical pathways are established in advance, preventing reliability issues that would otherwise require complex post-processing or result in defective devices.
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 enhances the reliability and performance of MEMS devices by ensuring a controlled etching profile and reducing deflection, leading to improved long-term reliability and performance of MEMS components.
Implementation Method 1
etching the MEMS layer to form a pair of sense electrodes and a proof mass from the designated sense electrode portions and proof mass portions, respectively
Data Source
AI summary
A method for fabricating a MEMS sensor device. The method can include providing a substrate, forming an IC layer overlying the substrate, forming an oxide layer overlying the IC layer, forming a metal layer coupled to the IC layer through the oxide layer, forming a MEMS layer having a pair of designated sense electrode portions and a designated proof mass portion overlying the oxide layer, forming a via structure within each of the designated sense electrode portions, and etching the MEMS layer to form a pair of sense electrodes and a proof mass from the designated sense electrode portions and proof mass portions, respectively. The via structure can include a ground post and the proof mass can include a sense comb. The MEMS sensor device formed using this method can result is more well-defined edges of the proof mass structure.