MEMS Cavity Sealing via Segmented Lid and Conductive Mediator
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Solution Overview
Problem
Existing MEMS devices face challenges in achieving high-vacuum cavity sealing and insulating wiring portions from lid portions, with materials like silicon nitride and polysilicon not effectively supporting high-performance requirements.
Innovation Solution
A MEMS device structure featuring a substrate with a functional element, a structural member forming a cavity, and a lid portion with a conductive member and sealing portion, where the conductive member is electrically connected to the connection electrode and the sealing portion is isolated by insulating films, allowing for high-vacuum sealing and material sharing between connecting members for both the functional element and semiconductor circuit elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon nitride or silicon dioxide is used as lid portion material, then manufacturing is simplified, but high-vacuum cavity sealing cannot be realized
Solution Approach 1:
The lid portion is divided into two separate components: a first lid portion made of insulating material (silicon nitride or silicon dioxide) that covers most of the cavity, and a second lid portion made of metal material that seals the remaining opening. This segmentation allows each component to be optimized for its specific function while maintaining manufacturing simplicity.
Solution Approach 2:
The lid portion uses a composite structure combining insulating material (silicon nitride/silicon dioxide) and metal material. The insulating material provides ease of manufacture and electrical isolation, while the metal material provides the necessary sealing performance for high-vacuum environments.
2Reliability
If polysilicon is used as lid portion material, then electrical conductivity is achieved, but positional alignment and joining in vacuum chamber becomes necessary
Solution Approach 1:
The electrical conductivity function is separated from the lid portion structure. A dedicated second conductive member (made of metal) is introduced to provide electrical connection, while the lid portion itself remains structurally simple and can be formed using standard semiconductor fabrication processes without requiring vacuum chamber alignment.
Solution Approach 2:
The patent introduces an intermediate conductive member as a mediator between the functional element and the external world. This separate conductive component simplifies the overall structure by eliminating the need for the lid portion itself to provide electrical connection, thereby avoiding complex alignment and joining processes.
3Ease of manufacture
If aluminum is used for both wiring and connecting member, then material usage is simplified, but high-performance MOS transistor requirements cannot be met
Solution Approach 1:
Different regions of the device use different materials optimized for their specific functions. The wiring layer uses aluminum for general connectivity, while the connecting member that interfaces with the high-performance MOS transistor uses tungsten to meet the stringent performance requirements of modern transistors.
Solution Approach 2:
The material selection is changed based on performance parameters. For standard wiring, aluminum suffices, but for the connecting member interfacing with high-performance transistors, tungsten is used due to its superior electrical and mechanical properties that meet the higher performance parameters required.
4Ease of manufacture
If wiring portion and lid portion are made of same material, then manufacturing is simplified, but electrical insulation cannot be ensured
Solution Approach 1:
The device structure is segmented into electrically isolated components. The lid portion is made of insulating material (silicon nitride or silicon dioxide) while the wiring and connecting members are made of conductive materials (aluminum and tungsten). This material segmentation ensures electrical insulation between different functional elements.
Solution Approach 2:
The device uses a composite material structure where insulating materials (silicon nitride/silicon dioxide) and conductive materials (aluminum/tungsten) are combined in specific configurations. The insulating lid portion is positioned to electrically isolate the functional element, while conductive wiring and connecting members provide necessary electrical connections.
Data Source
AI summary
A present MEMS device includes: a functional element with a connection electrode; a structural member that forms a cavity surrounding the functional element; a second insulating film provided so as to surround a predetermined region on a first surface of the connection electrode; a first lid portion that has a third insulating film, is provided with an opening, and covers a part of the cavity; a second lid portion that has a first conductive member and a sealing portion, the first conductive member being electrically connected to the predetermined region of the connection electrode, and the sealing portion sealing the opening of the first lid portion; a fourth insulating film that insulates the first conductive member from the sealing portion; and a second conductive member that penetrates the fourth insulating film and is electrically connected to the first conductive member.