ALD-Coated Vacuum Pressure Sensor for Drift Reduction

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Solution Overview

Problem

Silicon pressure sensors face errors due to hygroscopic support structures causing moisture absorption and stress changes, and outgassing in the reference vacuum leading to drift in measurements.

Innovation Solution

An integrated reference vacuum pressure sensor with atomic layer deposition coated surfaces to prevent moisture absorption and a vacuum reference cover to limit outgassing, using a stress isolation member and embedded traces for electrical connections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If hygroscopic materials are used for support structures, then manufacturing ease is improved, but sensing accuracy deteriorates due to moisture absorption causing stress changes

Engineering Contradiction:

Improveease of manufactureVSAvoidsensing accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

A non-hygroscopic stress isolation member is introduced as an intermediary between the hygroscopic support structure and the diaphragm. This mediator prevents moisture absorption from reaching the critical sensing components while allowing the hygroscopic material to remain in the support structure for ease of manufacture

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The support structure is segmented into two functional parts: a hygroscopic support portion that provides mechanical support and ease of manufacture, and a non-hygroscopic stress isolation portion that prevents stress transmission to the diaphragm. This segmentation allows each part to perform its specific function without compromising overall performance

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If materials are placed in the reference vacuum environment, then device functionality is improved, but measurement stability deteriorates due to outgassing causing pressure drift

Engineering Contradiction:

Improvedevice functionalityVSAvoidmeasurement stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The sensing circuitry is extracted from the vacuum environment and placed in a separate non-vacuum chamber. This allows the reference vacuum to remain clean and stable without materials outgassing, while the sensing function is maintained through electromagnetic coupling or sealed transmission across the interface

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A hermetic seal or interface structure acts as an intermediary between the vacuum reference chamber and the external environment. This mediator maintains the vacuum integrity while allowing electrical connections and signal transmission to the sensing circuitry

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If support structures are made larger to reduce stress, then stress isolation is improved, but device size increases

Engineering Contradiction:

Improvestress isolationVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The stress isolation member is made from a non-hygroscopic composite material that provides high mechanical strength and stress isolation properties in a compact form. This allows effective stress isolation without requiring large dimensions, maintaining small device size while improving reliability

Inventive Principle:

Principle #40Composite materials

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 effectively reduces sensing errors by isolating the sensor from stress and moisture, maintaining a stable reference vacuum, thereby enhancing the accuracy and reliability of pressure measurements.

Implementation Method 1

The surfaces of the stress isolation member and the substrate that face the channel and the input port are coated with an atomic layer deposition

Methodology Applied

Scientific EffectAtomic layer deposition: Deposition (physical)

Implementation Method 2

a vacuum reference cover hermetically bonded to the stress isolation member, the vacuum reference cover having a recess containing a vacuum formed therein

Methodology Applied

Scientific EffectHermetic sealing:

Data Source

PatentUS9116057B2Integrated reference vacuum pressure sensor with atomic layer deposition coated input port

Publication Date: 2015.08.25 HONEYWELL INTERNATIONAL INC

AI summary

An integrated reference vacuum pressure sensor with an atomic layer deposition (ALD) coated input port comprises a housing with an port for a media to enter the housing; a substrate and stress isolation member in the housing; wherein a channel extends through the substrate and the stress isolation member, wherein a trace is embedded within the stress isolation member, wherein stress isolation member and substrate surfaces exposed to the channel are coated with an ALD; a sensor die bonded to the stress isolation member, the sensor die comprising a diaphragm having circuitry, wherein a side of the diaphragm is exposed to the channel and the circuitry is mounted to another side of the diaphragm; a via extending through the sensing die electrically connecting the circuitry to the trace; and a cover bonded to the stress isolation member, the cover having a recess, the sensor die in the recess.