Capacitive Sensor Shielding for Temperature Stability

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Solution Overview

Problem

Capacitive MEMS sensors face accuracy and reliability issues due to electrical interference and temperature-induced plastic deformation, leading to temperature-dependent output drift and hysteresis.

Innovation Solution

Incorporating a patterned electrically conductive shield layer with reduced metal content and specific materials like titanium or titanium nitride, and optimizing the shield layer's design to minimize mechanical stress and thermal expansion, while using dielectric material in apertures to reduce electrical interference and temperature effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a large metal shield plate is used to reduce electrical interference, then electrical interference is reduced, but temperature-induced plastic deformation increases causing output drift and hysteresis

Engineering Contradiction:

Improveelectrical interferenceVSAvoidtemperature stability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The shield layer is divided into multiple segments separated by apertures rather than using a continuous large metal plate. This segmentation reduces the total amount of metal while maintaining shielding effectiveness through distributed shielding elements, thereby reducing temperature-induced plastic deformation and output drift.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The shield layer uses different materials with appropriate properties in different regions - electrically conductive materials for shielding effectiveness and materials with low thermal expansion coefficients in regions prone to thermal stress. This local differentiation optimizes both electrical interference reduction and temperature stability.

Inventive Principle:

Principle #3Local quality

2Reliability

If metal content in the shield layer is reduced to minimize plastic deformation, then temperature stability improves, but electrical interference shielding effectiveness decreases

Engineering Contradiction:

Improvetemperature stabilityVSAvoidelectrical interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The shield layer employs composite material structures combining electrically conductive materials with materials having low coefficients of thermal expansion. This composite approach maintains adequate electrical shielding while minimizing temperature-induced plastic deformation and improving overall temperature stability.

Inventive Principle:

Principle #40Composite materials

3Stress or pressure

If the shield layer is designed with apertures to reduce metal content, then temperature-induced stress is reduced, but electrical interference shielding may be compromised

Engineering Contradiction:

Improvemechanical stressVSAvoidelectrical interference

Core Design Contradiction:

Stress or pressureVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The design optimizes parameters such as aperture size, shape, distribution, and metal layer thickness to achieve the right balance between reducing mechanical stress and maintaining adequate electrical shielding effectiveness.

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 enhances the stability and reliability of MEMS sensor output by reducing electrical interference and temperature-dependent noise, maintaining accurate measurements across varying temperatures.

Implementation Method 1

the inclusion of a shield layer (e.g., an aluminum plate) between the sensor and sources of electrical interference (e.g., other components of the IC device)

Methodology Applied

Scientific EffectElectrical shielding: Faraday Cage

Implementation Method 2

Dielectric material disposed in the plurality of first apertures

Methodology Applied

Scientific EffectDielectric property: Dielectric

Implementation Method 3

measuring the capacitance between a measurement electrode embedded in the membrane and a base electrode positioned in proximity to the membrane

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentEP3784621B1Capacitive sensor having temperature stable output

Publication Date: 2024.10.09 SCIOSENSE BV

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Figure 1B
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AI summary

An example system includes a sensor. The sensor includes a base having a base electrode, and a first membrane suspended above the base. The first membrane includes a first membrane electrode. The first membrane is configured to deflect with respect to the base electrode in response to an environmental condition. The sensor is operable to measure a capacitance between the base electrode and the first membrane electrode. The system also includes a first electrically conductive shield layer positioned between the sensor and a device of the system operable to generate electrical interference signals. The first electrically conductive shield layer defines a plurality of first apertures extending through the first electrically conductive shield layer. The system also includes dielectric material disposed in the plurality of first apertures.