Capacitive MEMS Device Vertical Electrode Stacking

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Solution Overview

Problem

Conventional capacitive MEMS sensors have a substantial footprint in the plane due to the arrangement of electrodes, which limits their compactness and electrical sensitivity, especially when trying to reduce size while maintaining sensitivity and precision.

Innovation Solution

The capacitive device features a mobile portion with electrodes made in separate layers, allowing for a thick mobile element and thin electrode layers, enabling a narrow air gap and increased sensitivity, with the electrodes being made in the same layer for precise dimensional control and reduced encumbrance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the thickness of the inertial mass is increased to reduce its footprint in the plane, then the footprint is reduced, but the air gap of the interdigitated fingers must be increased which results in loss of electrical sensitivity

Engineering Contradiction:

Improvefootprint in the planeVSAvoidelectrical sensitivity

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent transitions from a planar arrangement of interdigitated fingers to a three-dimensional configuration where mobile electrodes are positioned on the top surface of the inertial mass and fixed electrodes are positioned on the bottom surface. This vertical stacking in the thickness dimension allows the inertial mass to maintain substantial thickness for reduced footprint while keeping the air gap between electrode faces small for high electrical sensitivity.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

Instead of arranging electrodes laterally around the inertial mass in the plane, the patent inverts the arrangement by placing mobile electrodes on the top surface and fixed electrodes on the bottom surface, effectively using the vertical dimension for electrode placement rather than the horizontal plane.

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of manufacture

If conventional interdigitated finger arrangement is used, then the device can be manufactured, but the footprint in the plane is substantial which limits compactness

Engineering Contradiction:

ImprovemanufacturabilityVSAvoidfootprint in the plane

Core Design Contradiction:

Ease of manufactureVSArea of stationary object

Solution Approach 1:

The patent reduces planar footprint by moving electrode arrangements from the horizontal plane to the vertical dimension, with mobile electrodes on the top surface and fixed electrodes on the bottom surface, allowing compact in-plane dimensions while maintaining manufacturability through standard MEMS processes.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 configuration reduces the device's footprint while enhancing electrical sensitivity and allowing for higher electrode density, achieving increased compactness without compromising precision or sensitivity.

Implementation Method 1

capacitive means of which the capacitance varies with the relative movement of the mobile and fixed portions

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

The relative movement of the seismic mass with respect to the substrate causes a relative movement between the interdigitated fingers, which results in an air gap change and a capacitance change

Methodology Applied

Scientific EffectElectrostatics: Electrostatics

Data Source

PatentUS9631952B2Capacitive microelectronic and/or nanoelectronic device with increased compactness

Publication Date: 2017.04.25 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

A device with a mobile element extending along a given plane comprising at least one first, one second and one third layers extending in planes parallel to the given plane, with the first layer forming a support, the second layer comprising all or a portion of the mobile element and means for suspending the mobile element with respect to the support and the third layer comprising all or a portion of the capacitive means of which the capacitance varies according to the relative position of the mobile element with respect to the support, said capacitive means comprising at least one mobile electrode integral with one of the faces of the mobile element parallel to the given plane, and at least one fixed electrode with respect to the support, with the fixed and mobile electrodes being arranged at least partially in the same plane parallel to the given plane and at least partially above and/or below the mobile element.