[IT]

Melt Pressure
Transducer and transmitters

Gefran patented:

IMPACT sensor technology

IMPACT is the acronym for Innovative Melt Pressure ACcurate Transducer, an innovative technology for measuring the pressure of high-temperature fluids.

SOI die overview


At the core of the IMPACT there’s a MEMS realized in Silicon on Insulator technology (SOI).

By the SOI technology it’s possible to create mesa piezoresistor electrically insulated by a thin layer of silicon dioxide from the mechanical silicon membrane, thus avoiding any leakage current that is the first limitation in the use of silicon at temperatures above 120 °C

The mechanical structure is a bossed circular membrane with a mechanical stop to avoid breaking during overloads of the die.
The position of the piezoresistors was chosen to increase sensitivity without affecting non linerity errors of the complete sensor.
The complete die is realized by a stack of 2 wafers: the bottom one that gives mechanical strength to the MEMS and the top one where the membrane itself is realized.




The bossed membrane is micromachined by DRIE process that can grant a edge steepness between 1 – 3 ° and an etch ground uniformity of ± 3 μm.




The piezoresistor are ion implanted and released by a RIE process.

The 2 wafers are then put together by anodic bonding process to obtain the final stack.

After that the metal system based on silicides and tungsten nitrides is sputtered. This process owned by Gefran creates both metallization without any problem of electromigration, thermal migration or evaporation and perfectly ohmic contacts till 350 °C continuous.

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FAQ
What is the operative principle of Impact sensors?

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