Multilayer Microfabricated Pressure Transducer with Etched Wells
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Solution Overview
Problem
The existing microfabricated pressure transducers are complex and expensive to manufacture, posing a challenge for the development of low-cost alternatives.
Innovation Solution
A microfabricated pressure transducer is formed using a multilayer substrate with embedded etch stop layers, featuring shallow and deep wells that create a perforated and unperforated membrane structure, allowing for a force-to-pressure transducer design, which is compact and inexpensive to produce.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional microfabricated pressure transducers are manufactured using complex multi-step processes, then measurement precision and reliability are improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The device is divided into distinct functional layers: a first substrate containing a first membrane, a second substrate containing a second membrane, and intermediate structures. This segmentation allows each layer to be fabricated independently using standard CMOS processes, reducing overall manufacturing complexity while maintaining measurement precision through specialized functionality in each segment.
Solution Approach 2:
The patent employs composite structures combining different materials and fabrication techniques - silicon membranes for pressure sensing, silicon dioxide for isolation, and metal layers for electrical connections. This composite approach enables each material to contribute its optimal properties (piezoresistive sensitivity, electrical insulation, conductive connectivity) while being integrated through compatible manufacturing processes.
2Volume of moving object
If sensitive pressure sensing elements are made smaller for integration, then device size is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The first and second membranes serve multiple functions: they act as pressure sensing elements, structural support for the respective substrates, and isolation barriers. This multi-functionality allows the membranes to be fabricated using standard thin-film deposition techniques rather than requiring specialized high-precision processes, reducing manufacturing precision requirements while maintaining small device size.
Solution Approach 2:
The patent utilizes the piezoresistive effect parameter - changing the electrical resistance of the membrane material in response to applied stress. By measuring resistance changes rather than requiring direct mechanical displacement measurements, the device achieves sensitive pressure detection with relaxed manufacturing precision requirements for the membrane thickness and uniformity.
3Temperature
If piezoresistive elements are used for pressure sensing, then temperature stability is improved, but manufacturing cost increases
Solution Approach 1:
The piezoresistive elements are fabricated using the same doped silicon regions that form the pressure-sensitive membranes themselves. The membranes serve their own sensing function without requiring separate, expensive sensing elements. The doped regions inherently provide both structural integrity and piezoresistive sensing capability, enabling temperature-stable operation with standard semiconductor manufacturing processes.
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 enables the creation of a compact and cost-effective microfabricated pressure transducer capable of accurately measuring pressure changes, suitable for various applications, including integrated circuits and devices requiring sensitive pressure sensing.
Implementation Method 1
a membrane that deflects under a force
Implementation Method 2
the resistance of the piezoresistive element changes as a function of strain
Implementation Method 3
there also exist high-precision sensors based on capacitive effect. A membrane is also used, with one plate of a capacitor mounted on the membrane and the other plate suspended above it
Data Source
AI summary
A microfabricated pressure transducer is formed in a multilayer substrate by etching a plurality of shallow and deep wells into the layers, and then joining these wells with voids formed by anisotropic etching. The voids define a flexible membrane over the substrate which deforms when a force is applied.