Advanced MEMS

 

This research axis is the think tank for the development of MEMS-based multi-functional systems. The technological challenge consists in rationally implementing 3D integration processes with hybrid materials (silicon, polymers, glass). The originality of our approach lies in the fact that we design innovative MEMS for application-oriented systems.

Three main fields of research have been explored during this period :

PyroMEMS and Nanoenergetics

Nanostructured Energetic Materials (EM) are characterized by improved rate of energy release, stability, security (sensitivity to unwanted initiation). EMs therefore offer a very attractive source of onboard energy and power. In that context, LAAS explored the integration of nanoscale EMs into MEMS to provide high-energy-density source for heat and/or mechanical power. We have validated the off-chip energy requirements for both civil and military applications.

During the 2005-2009 period, we focused our activity on 2 technological axis:

  • Development of new technological routes to integrate nEMs directly on electronic chips LAAS has already developed and published innovative technological process to integrate directly on a MEMS chip Al/CuO nanowired energetic layer. It is achieved by thermal oxidation of a thin evaporated copper layer at 450°C for 5 hours and by aluminium thermal evaporation inside the CuO nanowires (Fig. 2). A similar process has been proposed for Al/NiO and Al/MgO. We demonstrate an enhanced interfacial contact area between Al and oxide with no organic impurities, and our approach enables an easier integration into functional micro-systems.

 Nano energetic materials CuO/Al et NiO/Al.
  • Development of micro-energetic devices and explore their fields of applications

We have chosen to illustrate our contribution through 2 micro devices:

  • Integration of a microfluidic actuator (0.25mm²×100µm, overpressures>10kPa) into lab-on-chip/biochip for fluid ejection, which is based on the decomposition of a thin layer of energetic material deposited on a silicon microstructured platform.
  • Integration of a MEMS Safe Arm and Fire device for safe miniature fuzing device. It integrates sensors, igniters, 2 nEMs for gas and heat generation, mechanical actuators, circuitry, power supply…) within 3cm3. For the first time, it combines a mechanical arming unit with electrical safety functionalities on the same silicon initiator’s chip and uses an energetic layer to generate 5 bar in a few mm3 to dislock and move a screen that interrupts the explosive train. It requires only 635mW for ignition and actuation triggering.


Micro pyrotechnical actuator for lab-on-a-chip and MEMS based arm and fire systems

Development of a new sensor/actuator thermal device

 Our technology is based on conduction tunnel in a PN junction biased in reverse. The technological process has been simplified (5 levels of photolithography) to obtain robust matrix sensors and actuators implementation.

I (V) and Z (F) measurement temperature and mechanical deformation applied to the sensor

MEMS metrology

MEMS technology allows to have secondary voltage references with a wide range of voltage values (from a volts to a few hundreds of volts), which are very promising because of their expected performance (some parts in 107 of stability over a year). In a DC voltage reference, a feedback electronics to stabilize the mobile electrode at the pull-in point is necessary. For AC voltage reference, the actuation is ensured by an AC current which does not limit any more the mobile electrode displacement. MEMS based DC voltage references will be a response to a gap between the very expensive quantized Josephson voltage standards (10V upper limit value) and the affordable but noisy Zener diodes (10 V upper limit value). MEMS based AC voltage reference will constitute a real  breakthrough for the AC voltage as no reference exists except that based on the Josephson effect, which is under development and will have the same limitation as in DC in terms of available values (max 10 V), practical implementation and cost, in addition to a very short bandwidth frequency (up to 10 kHz). Since 2007, we have started collaboration with LNE (Laboratoire National de métrologie et d'Essai) to promote the concept of MEMS for metrology.

The Advanced MEMS research axis lead us to build partnerships:

  • Inside the LAAS:
    • polysilicon sensors for temperature and pressure intrahead. (M2D partnership),
    • embedded SiP application for power switches (ISGE partnership).
    • Feedback MEMS control (MRS partnership)
  • National level:
    • ANR PYRACT, RTRA NACOMAT, DGA REI MICROAMORCE, PEPS avec Université de Nantes
    • International level:
    • Switzerland: Université de Neuchatel
    • Taïwan University
    • Netherlands : European Space agency
  • Industry:
    • LACROIX (INIMAT), SNECMA SPS, AIRBUS, ROXEL, NEXTER MUNITIONS, ESSILOR laboratoire commun Pix-cell