MEMS RF-Contact Design for High Current Reliability
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Solution Overview
Problem
MEMS resistive switches face destructive failures due to high current flows through thin sidewalls in the via connection between the RF-contact and the underlying RF-electrode, leading to reliability issues.
Innovation Solution
A modified RF-contact design is implemented, where the RF contact and anchor contact are thicker than the insulating layer, allowing direct connection to the RF and anchor electrodes without traversing a thin sidewall, thereby reducing current flow through the sidewall and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thin contact layer is used to achieve low contact resistance at reasonable operating voltages, then contact resistance is reduced, but the thin sidewall in the via connection becomes susceptible to destructive failures under high current flows
Solution Approach 1:
The patent transitions from a conventional via connection where the contact layer forms a thin sidewall to a design where the contact layer is exposed on the surface. This dimensional change allows the contact layer to connect directly to the RF-electrode without traversing a thin sidewall, eliminating the reliability issue while maintaining low contact resistance through direct surface contact.
Solution Approach 2:
The patent extracts the contact layer from the insulating layer by creating openings that expose the contact layer on the surface. This separation allows the contact layer to be directly connected to the RF-electrode without being constrained by the insulating layer's thickness, thereby eliminating the thin sidewall problem while maintaining electrical connectivity.
2Force
If the gap between the plate and the pull-down electrode is reduced to achieve high contact force, then contact force is improved, but the contact layer becomes thinner and more vulnerable to high current damage
Solution Approach 1:
The patent changes the geometric configuration from a thin sidewall via connection to a surface-exposed contact layer design. This allows the contact layer to maintain sufficient thickness for current carrying capacity while still achieving the necessary contact force through direct contact between the movable plate and the exposed contact layer surface.
3Device complexity
If a conventional via connection is used to connect the contact layer to the RF-electrode, then device structure is simplified, but high current flows cause destructive failures in the thin sidewall
Solution Approach 1:
The patent extracts the contact layer from within the insulating layer by forming openings that expose the contact layer on the surface. This allows direct connection to the RF-electrode without requiring the contact layer to form a thin sidewall through the insulating layer, thereby eliminating the reliability issue while maintaining structural simplicity.
Solution Approach 2:
The patent transitions from a vertical via connection topology to a surface-exposed contact topology. This dimensional change eliminates the need for the contact layer to traverse the insulating layer thickness, removing the thin sidewall vulnerability while maintaining direct electrical connection to the RF-electrode.
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 design enables MEMS switches to handle higher currents without failing, improving the reliability and robustness of the RF-contact by eliminating the risk of destructive failures associated with high current flows through thin sidewalls.
Implementation Method 1
Once the electrode voltage reaches a certain voltage oftentimes referred to as a snap-in voltage, the plate moves towards the electrode. The release voltage is typically lower than the snap-in voltage due to the higher electrostatic forces when the plate is close to the actuation electrode
Implementation Method 2
The contact layer is typically connected to an underlying RF-electrode through a step-down via. High electrical powers applied across the switch causes large current flows through the electrical contact. The high currents running through the contact-layer on the thin sidewall can lead to destructive failures in the contact
Data Source
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Figure 3A
AI summary
The present invention generally relates to a mechanism for making a MEMS switch that has a robust RF-contact by avoiding currents to run through a thin sidewall in a via from the RF-contact to the underlying RF-electrode.