MEMS Pressure Sensor Structure for Low Parasitic Capacitance

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Solution Overview

Problem

Existing MEMS pressure sensors face challenges in ensuring high sensitivity and durability while maintaining compact size, due to issues with parasitic capacitance and membrane deformation under lamination stress during manufacturing.

Innovation Solution

The pressure sensor design incorporates a substrate with grooves forming movable and fixed electrodes, a membrane extending in-plane, and a sealing layer to reduce parasitic capacitance and protect the membrane from lamination stress, using a laminated structure with a silicon oxide closing layer and a sealing layer to enhance sealability and insulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional MEMS pressure sensor structure is used, then the sensor can detect pressure changes, but parasitic capacitance reduces measurement precision and sensitivity

Engineering Contradiction:

Improvepressure detection sensitivityVSAvoidparasitic capacitance

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes the parasitic capacitance by introducing a groove that divides the substrate into first and second regions, separating the movable electrode from the fixed electrode. This physical separation eliminates the harmful capacitive coupling between electrodes, thereby improving measurement precision and pressure detection sensitivity.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The substrate is segmented into distinct first and second regions by a groove, creating separate zones for the movable and fixed electrodes. This segmentation prevents unwanted electrical interaction between the electrodes, reducing parasitic capacitance and enhancing the sensor's measurement precision.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If multiple layers are laminated during manufacturing, then the sensor structure is completed, but lamination stress causes membrane deformation and damage

Engineering Contradiction:

Improvelaminated structure assemblyVSAvoidmembrane integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies a protective film to the membrane surface before the lamination process. This preliminary protective measure prevents damage to the membrane during subsequent lamination steps, ensuring membrane integrity while still allowing complete assembly of the multi-layer structure.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protective film acts as a cushioning layer that absorbs and distributes lamination stress before it can reach and damage the membrane. This beforehand cushioning protects the membrane from mechanical damage during the manufacturing process while maintaining structural completeness.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Volume of moving object

If the sensor structure is made compact, then the device size is reduced, but sealability and insulation performance deteriorate

Engineering Contradiction:

Improvesensor sizeVSAvoidsealability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent uses a composite sealing structure combining a sealing layer made of elastic material with a protective film. This composite approach provides both effective sealing to maintain the vacuum environment and mechanical protection, achieving reliable sealability in a compact sensor design.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent employs thin film structures including a protective film and sealing layer that provide effective sealing and insulation in a compact configuration. These thin films maintain the vacuum environment and protect internal components while minimizing the overall sensor size.

Inventive Principle:

Principle #30Flexible shells and thin films

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 achieves high sensitivity and durability by reducing parasitic capacitance and minimizing membrane damage during manufacturing, allowing for compact and reliable pressure detection.

Implementation Method 1

configured to be capable of detecting an external air pressure by electrically detecting deformation of the membrane based on a difference between an air pressure inside the cavity and an external air pressure

Methodology Applied

Scientific EffectPressure difference: Pressure Gradient

Implementation Method 2

using a laminated structure with a silicon oxide closing layer and a sealing layer to enhance sealability and insulation

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentUS12578244B2Pressure sensor and method of manufacturing pressure sensor

Publication Date: 2026.03.17 ROHM CO LTD

AI summary

A pressure sensor includes: a substrate having first and second main surfaces and having a thickness in first direction; a first chamber recessed from the first main surface in the first direction with respect to the substrate; a second chamber recessed from the first main surface in the first direction with respect to the substrate and adjacent to the first chamber in second direction; a fluid passage recessed from the first main surface in the first direction with respect to the substrate and causing the first chamber to be in fluid communication with an outside; a closing layer laminated on the first main surface of the substrate and closing openings of the first chamber and the second chamber; and a membrane partitioned by the first and second chambers in the second direction and extending in a plane parallel to the first direction and a third direction.