MEMS Electrode Stiffness via Segmented Protection Rings
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Solution Overview
Problem
Microelectromechanical systems (MEMS) devices, particularly microphones, face challenges in achieving high stiffness and integration with CMOS processes, which affects their sensitivity and performance.
Innovation Solution
A MEMS device with a first electrode and a second electrode, where the first electrode includes multiple metal layers and protection rings that connect adjacent metal layers to define enclosed spaces, and a dielectric layer is used to connect these layers, enhancing stiffness, and the fabrication method integrates with CMOS processes to simplify manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple metal layers are stacked to form the electrode, then the electrode stiffness is improved, but the structural complexity and fabrication difficulty increase
Solution Approach 1:
The electrode is divided into multiple metal layers (first metal layer, second metal layer, third metal layer) stacked in sequence, with each layer contributing to the overall stiffness. The protection rings are also segmented and positioned between these layers to provide localized reinforcement without requiring a completely complex redesign of the entire structure.
Solution Approach 2:
The electrode structure combines multiple metal layers with different properties, interspersed with dielectric layers and protection rings made of materials such as silicon nitride or silicon oxide. This composite approach allows each material to contribute its strengths, achieving high overall stiffness while managing stress and fabrication complexity.
2Strength
If protection rings are added to connect metal layers, then the electrode strength is improved, but the manufacturing process complexity increases
Solution Approach 1:
The protection rings are formed between the metal layers during the stacking process, rather than being added afterward. This preliminary formation allows the rings to be integrated into the structure as it is being built, reducing the need for additional complex manufacturing steps and making the overall process more manageable.
Solution Approach 2:
The protection rings act as intermediary elements between the metal layers, providing both mechanical reinforcement and stress management. These rings are positioned at strategic locations where they can connect adjacent metal layers and provide localized support without requiring complex integration throughout the entire structure.
3Stability of the object's composition
If dielectric layers are used to connect metal layers within enclosed spaces, then stress distribution is improved, but the device complexity increases
Solution Approach 1:
Dielectric layers are placed specifically within enclosed spaces formed by the protection rings and metal layers, rather than uniformly throughout the entire electrode structure. This localized placement allows stress distribution to be improved in critical areas without adding unnecessary complexity to regions where it is not needed.
4Reliability
If the electrode structure is designed for high stiffness, then the MEMS sensitivity is improved, but the integration with CMOS process becomes more difficult
Solution Approach 1:
The electrode structure with multiple metal layers, protection rings, and dielectric layers is designed to be compatible with standard CMOS fabrication processes. The materials and structural approaches used (such as silicon nitride and silicon oxide for protection rings) are consistent with those already employed in CMOS manufacturing, allowing the high-stiffness electrode to be integrated without requiring entirely separate or specialized process lines.
Data Source
AI summary
A method for fabricating a microelectromechanical system (MEMS) device of the present invention includes the following steps: providing a substrate, comprising a circuit region and a MEMS region separated from each other; forming an interconnection structure on the substrate in the circuit region, and simultaneously forming a plurality of dielectric layers and a first electrode on the substrate in the MEMS region, wherein the first electrode comprises at least two metal layers formed in the dielectric layers and a protection ring formed in the dielectric layers and connecting two adjacent metal layers, so as to define an enclosed space between the two adjacent metal layers; forming a second electrode on the first electrode; and removing the dielectric layers outside the enclosed space in the MEMS region to form a cavity between the electrodes.