MEMS Switch Venting via Lateral Sacrificial Tabs
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Solution Overview
Problem
Current MEMS switch manufacturing methods face challenges such as dimensional variability, unwanted stresses, and high contact resistance due to the deposition of sealing materials through vent holes, as well as sticktion issues during processing, particularly in cantilever and bridge beam type switches.
Innovation Solution
The method involves forming tabs of sacrificial material on the side of the switching device, creating openings in the capping layer remote from the MEMS structure, stripping the sacrificial material through these openings using dry or wet etchants, and sealing the openings with a capping material to avoid deposition on the MEMS structures, thereby reducing stress and contact resistance and preventing sticktion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vent holes are formed directly over the MEMS structure to remove sacrificial material, then the sacrificial material can be effectively removed from the cavity, but the sealing material deposits on the MEMS structure causing dimensional variability, unwanted stresses, and high contact resistance
Solution Approach 1:
The patent moves the vent holes from a vertical position directly over the MEMS structure to a lateral position at the periphery of the dome. This dimensional relocation allows sacrificial material removal while preventing sealing material deposition on the MEMS structure, thereby eliminating dimensional variability and stress issues.
Solution Approach 2:
The patent introduces tabs as intermediary structures that extend from the sacrificial material to the periphery of the dome. These tabs serve as access points for removing sacrificial material while being positioned away from the MEMS structure, acting as a mediator that enables material removal without causing harmful deposition on the switch components.
2Reliability
If vent holes are formed directly over the MEMS structure, then sacrificial material removal is achieved, but contact resistance increases due to material deposition on fixed electrodes
Solution Approach 1:
The vent holes are relocated from a position directly over the MEMS structure to a lateral position at the periphery. This spatial repositioning prevents sealing material from depositing on the fixed electrodes, thereby maintaining low contact resistance and reliable switch isolation performance.
3Productivity
If sacrificial material is stripped using wet etching processes, then removal efficiency is high, but sticktion occurs causing the switch to freeze closed
Solution Approach 1:
The tabs serve as intermediary structures that enable sacrificial material removal while preventing direct contact between wet etchants and the MEMS structure. This mediation allows efficient material removal through the tabs while preventing sticktion on the switch components, maintaining reliable opening capability.
Solution Approach 2:
The patent segments the sacrificial material removal process by creating separate access points (vent holes at the periphery) that are spatially separated from the MEMS structure. This segmentation allows the etching process to act on the sacrificial material through the tabs without causing sticktion on the switch components.
4Ease of manufacture
If photoresist is applied on the curvature of the dome to print vent holes, then vent holes can be formed, but the process becomes difficult due to variability requiring printing in more than one focal plane
Solution Approach 1:
The vent holes are positioned at the periphery of the dome where the surface curvature is reduced compared to the top center. This positional change in another dimension (lateral vs. vertical) creates a more favorable surface for photolithography, reducing the need for multiple focal planes and simplifying the manufacturing 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 approach reduces material variability, contact resistance, and eliminates sticktion by avoiding the deposition of capping materials on the MEMS structures, leading to more reliable and functional MEMS switches with improved performance.
Implementation Method 1
stripping the sacrificial material through at least one opening formed on the at least one tab which is on the side of the switching device
Implementation Method 2
sealing the at least one opening with a capping material
Data Source
AI summary
Integrated MEMS switches, design structures and methods of fabricating such switches are provided. The method includes forming at least one tab of sacrificial material on a side of a switching device which is embedded in the sacrificial material. The method further includes stripping the sacrificial material through at least one opening formed on the at least one tab which is on the side of the switching device, and sealing the at least one opening with a capping material.