MEMS Sensor Trapping Structures for Particle Contamination

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Solution Overview

Problem

MEMS sensors face contamination issues due to inlet holes allowing harmful particles to reach the sensing element, which can affect the sensor's functionality and reliability.

Innovation Solution

A microelectromechanical sensor design featuring a supporting body with semiconductor material, a cap with inlet holes, a sensing structure with a measuring chamber and sensitive element, fluidic paths for external coupling, and trapping structures that extend beyond the access sections of the fluidic paths to collect and retain contaminating particles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If inlet holes are provided for external fluidic coupling, then the sensor can receive external pressure variations, but harmful particles can reach the sensing element through these inlet holes

Engineering Contradiction:

Improveexternal fluidic couplingVSAvoidparticle contamination

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces trapping structures as intermediary elements between the inlet holes and the sensing element. These trapping structures capture harmful particles before they can reach the sensing element, while still allowing fluidic coupling to function. The trapping structures act as a mediator that separates the beneficial fluidic connection from the harmful particle ingress.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the fluidic path into distinct zones: the inlet holes, the trapping structures, and the sensing element. By dividing the continuous fluidic path into segmented sections with different functions, the design allows particles to be trapped in intermediate zones while maintaining fluid communication between the external environment and the sensing element.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If the number of inlet holes is reduced to minimize contamination paths, then particle contamination is reduced, but redundancy of the sensor is compromised

Engineering Contradiction:

Improveparticle contaminationVSAvoidsensor redundancy

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The trapping structures serve as intermediaries that enable multiple inlet holes to coexist without proportionally increasing contamination risk. Each trapping structure protects its associated inlet hole, allowing the sensor to maintain redundancy through multiple inlet holes while keeping contamination levels controlled.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If the dimensions of inlet holes are made small to reduce particle entry, then contamination is reduced, but obstruction of inlet holes becomes more likely due to manufacturing constraints and particle accumulation

Engineering Contradiction:

Improveparticle contaminationVSAvoidinlet hole patency

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The trapping structures act as intermediary zones that capture particles before they can accumulate in the inlet holes themselves. This allows the inlet holes to maintain larger, more reliable dimensions for fluidic coupling while the trapping structures bear the burden of particle accumulation, preventing obstruction of the critical inlet pathways.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Object-affected harmful factors

If inlet holes are positioned at a sufficient distance from the sensing element to reduce contamination, then particle contamination is reduced, but the effectiveness is limited by manufacturing constraints and particle accumulation in the fluidic paths

Engineering Contradiction:

Improveparticle contaminationVSAvoidfluidic path length

Core Design Contradiction:

Object-affected harmful factorsVSLength of stationary object

Solution Approach 1:

The patent addresses the fluidic path length issue by transitioning from a purely horizontal separation approach to a three-dimensional arrangement. The trapping structures are positioned at different vertical levels (depths) within the sensor body, creating a multi-layered protection scheme that reduces contamination risk without requiring excessively long horizontal fluidic paths.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS20250189392A1Microelectromechanical sensor with external fluidic coupling having contamination-reducing structure

Publication Date: 2025.06.12 STMICROELECTRONICS SRL

AI summary

A microelectromechanical sensor includes: a supporting body, containing semiconductor material; and a cap, of semiconductor material, coupled to the supporting body and having an internal surface arranged facing the supporting body and a plurality of inlet holes. The sensor further includes a sensing structure, comprising a measuring chamber and a sensitive element, the sensitive element being formed at least partially in the supporting body and facing the measuring chamber; fluidic paths configured to couple the sensing structure with the environment external to the sensor through the inlet holes, and having an access section to the measuring chamber; and trapping structures defined in the supporting body. The trapping structures are in communication with respective fluidic paths and extend in the supporting body at least partially at a greater distance, from the internal surface of the cap, with respect to the access section of each fluidic path.