Coriolis Flow Sensor Buried Channel Fabrication

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Solution Overview

Problem

Coriolis-based micro-flowmeters manufactured in MEMS technology face high costs, low yield, and low reliability issues.

Innovation Solution

A Coriolis-force-based flow sensing device is developed using a silicon substrate with an insulating layer and driving electrodes, featuring a buried channel formed through a sacrificial region removal process, which includes forming apertures and using a porous layer to selectively etch the sacrificial material, resulting in a suspended structural body for vibration and fluid flow measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If MEMS technology is used to manufacture Coriolis-based micro-flowmeters, then the device can measure very low flowrates, but the manufacturing cost increases and yield decreases

Engineering Contradiction:

Improveflowrate measurement capabilityVSAvoidmanufacturing cost and yield

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The device is segmented into distinct functional layers (suspension layer, structural layer, fluidic layer) that can be manufactured separately and then integrated. This segmentation allows each layer to be optimized independently and facilitates mass production through standardized assembly processes, reducing overall manufacturing complexity and cost while maintaining micro-flow measurement precision.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs a multi-layer nested structure where the fluidic layer is embedded within the structural layer, which is itself suspended within the suspension layer. This nesting approach allows compact integration of multiple functions within a small footprint, enabling precise flow measurement while simplifying the overall manufacturing process through layered fabrication.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Measurement precision

If complex MEMS manufacturing processes are used, then accurate fluid property measurement is achieved, but reliability decreases

Engineering Contradiction:

Improvefluid property measurement accuracyVSAvoiddevice reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent incorporates a suspension layer with sacrificial material that provides mechanical support and stress relief during manufacturing and operation. This pre-engineered support structure cushions the delicate measurement components from manufacturing stresses and operational shocks, enhancing device reliability without compromising measurement precision.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

Different layers are assigned specific material properties and structural characteristics optimized for their local function: the suspension layer provides mechanical support, the structural layer provides fluid containment, and the fluidic layer enables flow measurement. This local optimization of material and structural quality ensures each component performs its function reliably while contributing to overall measurement accuracy.

Inventive Principle:

Principle #3Local quality

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 method enhances reliability and reduces costs, making it suitable for mass production while maintaining accurate fluid property measurement capabilities.

Implementation Method 1

Forming a porous layer within the aperture. The porous layer having pores dimensioned to allow passage of an etchant configured to selectively remove the second sacrificial region

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

at least one driving electrode is on the insulating layer. A silicon structural body partially overlaps the driving electrode

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Data Source

PatentUS11971284B2Method for manufacturing a silicon-based coriolis-force-based flow sensing device, coriolis-force-based flow sensing device, and system for measuring a property of a fluid

Publication Date: 2024.04.30 STMICROELECTRONICS SRL

AI summary

Embodiments of a Coriolis-force-based flow sensing device and embodiments of methods for manufacturing embodiments of the Coriolis-force-based flow sensing device, comprising the steps of: forming a driving electrode; forming, on the driving electrode, a first sacrificial region; forming, on the first sacrificial region, a first structural portion with a second sacrificial region buried therein; forming openings for selectively etching the second sacrificial region; forming, within the openings, a porous layer having pores; removing the second sacrificial region through the pores of the porous layer, forming a buried channel; growing, on the porous layer and not within the buried channel, a second structural portion that forms, with the first structural region, a structural body; selectively removing the first sacrificial region thus suspending the structural body on the driving electrode.