Sercel and TRONIC'S Microsystems, have collaborated for the production of a new generation of seismic sensors, or geophones, based on MEMS. Designed by CEA Leti, the 0.1µg resolution accelerometer packaged under vacuum has been optimised and industrialized by TRONIC'S Microsystems.

Geophones comprise one of the key products of Sercel (F), the world leader in seismic equipments for oil and gas exploration. Extremely sensitive sensors, the geophones measure the reflection of acoustic waves, sent on the surface of the field, in the different geologic layers (see figure 1). The data are then used to draw geological survey maps indicating the location and size of oil and gas reserves.

Geophones, though being inexpensive electromagnetic components (see figure 2), have rather been heavy and cumbersome as they need to be linked by cables to a central processing unit. Modern oil exploration now demands ever lighter, more mobile solutions capable of very high precision.

MEMS based geophone
Sercel spent several years working with the CEA Leti (F), to show the feasibility and design a MEMS based geophone. The collaboration resulted in a prototype of a far smaller and lighter accelerometer based geophone (see figure 2 and table 1).

The prototype reached the required extreme performances: a resolution down to 0.1µg, less than a millionth of the Earth gravity, over a range of +/- 100mg.

However, one of the biggest challenges laid in moving the MEMS-based solution from the laboratory to the production line. MEMS actually present no standard fabrication processes and have extremely demanding packaging requirements and complex specific testing procedures. Sercel therefore needed a custom MEMS manufacturer that could transform its MEMS concept into a reliable industrial product.

Geophone industrialization
Experienced in industrializing and manufacturing custom MEMS accelerometers, TRONIC'S Microsystems (F) also mastered the building blocks of Sercel's geophone technology.

The company's high-end custom MEMS manufacturing business model was also particularly appropriate to Sercel's manufacturing needs. Therefore the two companies entered into a business partnership

Starting from the prototypes, Tronic's optimised the device and qualified its specific process and vacuum packaging technique. The French manufacturer then ensured the first series deliveries early 2003 and today delivers packaged and tested geophone components (see figure 3) that Sercel integrates into new digital systems.

Vacuum package for MEMS
In order to reduce the molecular noise on the structure and to reach the requisite performance levels, TRONIC'S encapsulates the silicon microstructure under a very high vacuum environment in a LCC packaging. This packaging allows the MEMS geophone to exceed a Q factor of over 10.000 (estimated vacuum in the range of 1mTorr).

Smaller and lighter, the vacuum packaged MEMS geophone even outperform some other key specifications of the traditional geophones (see table 1).

In addition, 3 MEMS geophones can also be integrated together in a very small space with its digital electronic eliminating some of the cables previously required. The new MEMS based geophone therefore facilitates the logistic for Sercel customers while allowing 3 components measurement with a higher dynamic.

Through this collaboration, TRONIC'S Microsystems has further proven its ability to transform custom MEMS concepts into reliable high performance products for demading applications.

AngelTech Live III: Join us on 12 April 2021!

AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST) and will feature online versions of the market-leading physical events: CS International and PIC International PLUS a brand new Silicon Semiconductor International Track!

Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.

2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.

We shall also look at microLEDs, a display with many wonderful attributes, identifying processes for handling the mass transfer of tiny emitters that hold the key to commercialisation of this technology.

We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.

Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.

Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.

So make sure you sign up today and discover the latest cutting edge developments across the compound semiconductor and integrated photonics value chain.

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