MEMS Switch Double Cantilever Electrode Structure

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Solution Overview

Problem

MEMS switches require high switching voltages, leading to unwanted charging and eventual failure due to electrostatic forces, and existing solutions either increase fabrication costs or lack hermetic sealing.

Innovation Solution

The development of MEMS switches with a double cantilever arrangement hermetically sealed within a nitride liner, reducing the gap between electrodes to lower the minimum switching voltage and enhance reliability by eliminating arcing and dielectric breakdown.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high switching voltage is applied to pull the suspended electrode down to the fixed electrode, then the switch can be actuated, but unwanted charging on insulator occurs and eventual failure happens

Engineering Contradiction:

Improveswitch reliabilityVSAvoidunwanted charging on insulator

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The single electrode structure is segmented into two parallel-plate electrostatic actuators that work together. By dividing the actuation function into two separate electrode pairs, the patent reduces the voltage required for each individual actuator while maintaining reliable switch operation, thereby reducing unwanted charging on the insulator.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the electrical parameters by using two electrostatic actuators with reduced individual voltages instead of one high-voltage actuator. This parameter change reduces the electric field stress on the insulator material, preventing unwanted charging and improving reliability.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If additional electrostatic actuators are used to lower pull-in voltage, then switching voltage is reduced, but fabrication costs increase

Engineering Contradiction:

Improveswitching voltageVSAvoidfabrication cost

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The additional electrostatic actuators serve multiple functions: they reduce the pull-in voltage for switch actuation and provide a restoring force to return the suspended electrode to its initial position. This multi-functionality reduces the need for separate components, thereby controlling fabrication costs despite the added complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the actuation function and the restoring force function into a single integrated structure with two electrostatic actuators. By combining these functions, the design eliminates the need for separate restoring spring mechanisms, reducing overall fabrication complexity and cost.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of operation

If the gap between suspended and fixed electrodes is reduced to lower pull-in voltage, then switching voltage decreases, but the risk of arcing and dielectric breakdown increases

Engineering Contradiction:

Improvepull-in voltageVSAvoidarcing and dielectric breakdown

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The total voltage requirement is segmented across two separate electrostatic actuators. Each actuator operates at a lower voltage with a reduced gap, which distributes the electric field stress and reduces the risk of arcing and dielectric breakdown compared to a single high-voltage actuator with larger gap.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the operational parameters by using two low-voltage, small-gap actuators instead of one high-voltage, large-gap actuator. This parameter change reduces the peak electric field strength at any single location, thereby minimizing the risk of arcing and dielectric breakdown while achieving the desired low pull-in voltage.

Inventive Principle:

Principle #35Parameter changes

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 solution reduces the pull-in voltage required to operate the switches, minimizing unwanted charging and failure while maintaining hermetic sealing, thus improving the reliability and reducing fabrication costs.

Implementation Method 1

a single cantilever arm (suspended electrode) is pulled toward a fixed electrode by application of a voltage by a fixed electrode. In operation, the gap between the electrodes is reduced... This arrangement will reduce the minimum switching voltage required to pull the electrodes together

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Implementation Method 2

the electrodes 16a, 16b and 18a, 18b are hermetically sealed within the nitride layer 22

Methodology Applied

Scientific EffectHermetic sealing: Physical Containment

Data Source

PatentUS10017383B2Method of manufacturing MEMS switches with reduced switching voltage

Publication Date: 2018.07.10 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

An approach includes a method of fabricating a switch. The approach includes forming a fixed electrode, forming a first cantilevered electrode, forming a second cantilevered electrode aligned vertically over the first fixed electrode, and which has an end that overlaps and is operable to directly contact an end of the first cantilevered electrode upon an application of a voltage to the fixed electrode, and forming a hermetically sealed volume encapsulating the first fixed electrode, the second fixed electrode, the first cantilevered electrode, and the second cantilevered electrode.