MEMS Pressure Sensor Cross-Shaped Sensing Layer

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Solution Overview

Problem

The manufacturing process of piezo-resistive MEMS pressure sensors faces challenges in controlling the thickness of the sensing film, leading to difficulties in achieving consistent sensitivity and burst pressure.

Innovation Solution

A pressure sensing module with a substrate featuring a stepped cavity and a sensing layer with a cross-shaped structure, including hollow portions, which improves structural symmetry and reduces rigidity, enhancing sensitivity and burst pressure by allowing the sensing layer to deform within the stepped cavity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If backside wet etching is used to adjust the thickness of the sensing film, then the thickness can be modified, but the manufacturing process becomes difficult and thickness control is poor

Engineering Contradiction:

Improvethickness control of sensing filmVSAvoidmanufacturing process difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

Instead of using backside wet etching to control thickness, the patent inverts the approach by using frontside dry etching with a precisely controlled sacrificial layer. The sacrificial layer thickness is controlled during deposition, and dry etching removes material in a controlled manner to achieve the desired sensing film thickness, thereby improving both thickness control and manufacturing ease.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent applies preliminary action by forming a sacrificial layer with a precisely controlled thickness before forming the sensing film. This sacrificial layer serves as a thickness template, allowing the sensing film to be deposited to a predetermined thickness, thus eliminating the need for complex backside etching processes to control thickness.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the sensing layer rigidity is increased, then structural stability is improved, but sensitivity for sensing is reduced

Engineering Contradiction:

Improvestructural stabilityVSAvoidsensitivity

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent applies local quality by creating a cross-shaped structure with hollow portions only in specific locations rather than making the entire sensing layer uniform. The hollow portions are strategically positioned to reduce rigidity where it would otherwise be excessive, while maintaining structural stability in critical areas. This localized modification allows the sensing layer to deform more easily under pressure, improving sensitivity without compromising overall structural integrity.

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 design improves sensitivity and burst pressure while simplifying the manufacturing process and increasing yield by controlling the thickness of the sensing layer through grinding and dry etching, rather than backside wet etching.

Implementation Method 1

A piezo-resistive microelectromechanical system (MEMs) pressure sensor is configured to convert pressure into a corresponding electronic signal. The sensing film may be provided to measure the applied pressure by measuring the change in resistance caused by the pressure applied to the sensing film.

Methodology Applied

Scientific EffectPiezo-resistive effect: Piezoresistive Effect

Implementation Method 2

The central portion and the extending portions respectively include at least one hollow portion. The cross-shaped structure includes a central portion and a plurality of extending portions connecting the central portion. The hollow portions reduce the rigidity of the sensing layer, allowing it to deform within the stepped cavity.

Methodology Applied

Scientific EffectStructural rigidity reduction through hollow geometry:

Implementation Method 3

The substrate includes a stepped cavity and an opening. The stepped cavity extends from the first surface to the second surface. When the sensing layer is deformed by a pressure exceeding the operating range, the sensing layer will abut against the stepped cavity thereunder. If the pressure continues to increase, the deformation area of the sensing layer will be reduced and the burst pressure will increase.

Methodology Applied

Scientific EffectGeometric constraint:

Data Source

PatentUS20240327205A1Pressure sensing module and manufacturing method thereof

Publication Date: 2024.10.03 CORETRONIC MEMS CORP

AI summary

A pressure sensing module includes a substrate and a sensing layer. The substrate has a first surface and a second surface opposite to each other. The substrate includes a stepped cavity and an opening. The stepped cavity extends from the first surface to the second surface, the opening extends from the second surface to the first surface, and the stepped cavity communicates with the opening. The sensing layer is disposed on the first surface of the substrate and covers the first surface of the substrate. The sensing layer includes at least one sensing element and a cross-shaped structure. The cross-shaped structure includes a central portion and a plurality of extending portions connecting the central portion. The central portion and the extending portions respectively include at least one hollow portion. An orthographic projection of the central portion of the cross-shaped structure on the substrate overlaps with the opening of the substrate.