MEMS Switch Contact Stack for Uniform Beam Engagement
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Solution Overview
Problem
The production of microelectromechanical (MEMS) switches is challenging due to their small size, leading to high defect rates and cost issues, making it difficult to manufacture them in a cost-effective manner for various applications, including consumer electronics.
Innovation Solution
A method for forming a microelectromechanical device with a beam that deviates from a resting to an engaged or disengaged position through electrical biasing, comprising a backplane with RF electrodes, electrical contacts made of ruthenium and titanium nitride layers, and a seal layer to enclose the beam in a cavity, allowing for precise control and high yield production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If MEMS switches are made small to reduce footprint, then device size is reduced, but manufacturing yield and quality deteriorate
Solution Approach 1:
The patent divides the electrical contact structure into multiple segments: a first electrical contact layer (aluminum), a second electrical contact layer (copper), and an intermediate oxide layer. This segmentation allows each layer to be optimized independently for its specific function, enabling reliable electrical connections in small-footprint MEMS devices while maintaining manufacturing yield through standardized, modular fabrication processes
Solution Approach 2:
The patent employs composite material structures combining different metals (aluminum and copper) with an oxide intermediate layer. This composite approach leverages the advantages of each material: aluminum provides good adhesion to the beam, copper provides excellent electrical conductivity, and the oxide layer provides controlled electrical isolation. This composite structure enables reliable operation at small scales while maintaining manufacturing quality
2Ease of manufacture
If conventional electrical arrangements are used, then ease of manufacture is maintained, but device footprint increases
Solution Approach 1:
The patent transitions from planar electrical contacts to vertically stacked electrical contact layers. By adding the vertical dimension with multiple contact layers (aluminum, oxide, copper) stacked above each other, the design achieves three-dimensional integration that reduces the horizontal footprint while maintaining manufacturing simplicity through extended deposition and etching processes
Solution Approach 2:
The patent implements a nested structure where the first electrical contact layer, oxide layer, and second electrical contact layer are arranged concentrically above the beam. This nesting allows multiple electrical functions to be integrated in a compact vertical space, reducing the overall device footprint while maintaining ease of manufacture through sequential fabrication steps
3Device complexity
If electrical contacts are placed close to the beam, then device integration is improved, but unwanted beam contact occurs
Solution Approach 1:
The patent introduces an oxide layer as an intermediary between the first electrical contact layer (aluminum) and the second electrical contact layer (copper). This intermediate oxide layer acts as a controlled barrier that prevents unwanted direct contact between the beam and electrical contacts while allowing the contacts to be positioned close to the beam for high integration density. The oxide layer can be selectively removed or breached during operation to establish controlled electrical connections
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
The method enables the production of MEMS devices with high yield and low defect rates, suitable for diverse applications, offering cost-effective solutions and power-saving advantages while preventing unwanted beam contact and ensuring reliable operation.
Implementation Method 1
depositing a first ruthenium layer over the first layer, depositing a titanium nitride layer over the first ruthenium layer, depositing a second ruthenium layer over the titanium nitride layer
Implementation Method 2
a beam of the microelectromechanical device may deviate from a resting to an engaged or disengaged position through electrical biasing
Data Source
AI summary
Methods of forming a microelectromechanical device are disclosed. In some embodiments, a first layer is deposited on a backplane having at least two electrodes. One or more electrical contacts over the first layer are formed. Forming the one or more electrical contacts includes: depositing a first ruthenium layer over the first layer, depositing a titanium nitride layer over the first ruthenium layer, depositing a second ruthenium layer over the titanium nitride layer, etching the second ruthenium layer with a first etchant, etching the titanium nitride layer with a second etchant different than the first etchant; and etching the first ruthenium layer with the first etchant. Additionally, a beam is formed above one or more electrical contacts, the beam being spaced from the one or more electrical contacts and a top electrode is formed above the beam. A seal layer above the beam to enclose the beam in a cavity.