Passive wireless SAW sensors using advanced piezoelectric materials and structures Sylvain Ballandras frec n sys

Passive wireless SAW sensors using advanced piezoelectric materials and structures Sylvain Ballandras frec n sys

Summary of the presentation frec n sys brief introduction Wireless sensor problematic SAW/BAW devices for sensing applications Device principles and related materials Wireless measurement using SAW-based monotoring systems Electronics, antenna, environment constraints Example of application for harsh environment measurements Demosntration of using analog-based measurement and distance connection Conclusion

An industrial technology platform for SAW/BAW devices Trikon Sigma cluster for AlN Standard wet process workshop Nikon body-9 stepper 2 CD-SEMs for 4 and 6 wafers Production capacity > 1 million pieces a year frec n sys is the unique operator of theis platform under contract with Franche-Comté University, owner of the equipments + easy access to FEMTO/MIMENTO resources

Wireless passive sensors for high-end markets Sensors for harsh environments Pipeline, Alaska, Temperature < -50 C, humidity, condensation, extreme geographical localization Turbines, Temperature > 500 C, Rotation speed (3000 rpm), magnetic fields and metallic environment

Basic SAW parameters Piezoelectric substrate (Quartz, LiNbO 3, LiTaO 3,...) Sampled impulse response SAW Overlap shape of the fingers = Fourier transform of the expected spectral function Interdigited transducers (IDT) 10 µm 2 µm 1 µm 0.5 µm 0.35 µm 0.25 µm Electrode width 100 MHz 500 MHz 1 GHz 2 GHz 3 GHz 4 GHz Operating frequency VHF UHF 2.45 GHz ISM band 5.8 GHz ISM band 434 MHz ISM band 915 MHz ISM band L-Band S-Band C-Band

Materials for SAW Current industrial standard: 100 and 150 mm diameter (4 and 6 inch wafers) LiNbO 3 LiTa0 3 : Czochralski growth Intermediate/Strong coupling Wide band filters, wireless SAWtags < Quartz: Hydrothermal growth Small coupling Sources, narrow band filters, sensors (Courtesy of Cristal Innov) LGS/LGT: Czochralski growth intermediate coupling Sources, narrow band filters, High T sensors (Courtesy of Cristal Innov)

Bulk Acoustic Wave principles Bragg mirror Solidly mounted resonator SMR AlN Electrodes Air gap Film bulk acoustic resonator FBAR Electrodes AlN Semi-infinite Silicon substrate Semi-infinite Silicon substrate 250 µm 50 µm No man s land 2 µm 1 µm 0.5 µm Film thickness 5-20 MHz Up to 120 MHz 2-3 GHz 3-4 GHz 4-5 GHz Operating frequency Single-crystal technology Quartz, LiTaO 3,... Film deposition technologies: AlN, AlScN, ZnO More recently single crystals: LiNbO 3, LiTaO 3

Materials for BAW Reactive sputtering: AlN, AlScN, ZnO, LiNbO 3, PZT moderate properties for other material than AlN and ZnO Epitaxy: AlN, GaN, LiNbO 3, etc pb: electrodes Transferred layers: LiTaO 3, LiNbO 3, Quartz pb: industrial control ZnO Films (ZnO/Si) AlN films @ frec n sys (Characterized by Prof P. Muralt, EPFL) LiNbO 3 Smart-cut TM (Courtesy of CEA-Leti) http://www.helmholtz-berlin.de/forschung/enma/si-pv

SAW sensors: Resonators Dipole resonators 434 MHz (frec n sys) Mechanical traction tests on a calibrated bench Characterization of the sensor sensitivity vs nature of the substrate : 16,2 khz/mpa Aluminum (max 29 MPa) 5,4 khz/mpa Steel (max 100 MPa) Maximum deformation of 0.45 limit of the bonding linearity (M-Bond 200)

SAW sensors: Delay-lines Quadrupole delay lines 125 MHz Application to liquid-phase and gas micro-balance (courtesy of FEMTO-ST) SAW Tags 2.45 GHz Reflective delay lines (frec n sys) Delay line transfer function -23.92 db 125 Mhz Reflection coefficient in time domain Differential measurement using at min 2 echoes

Wireless sensor interrogators Frequency synthesizer Splitter Antenna driver sensor interrogation Frequency modulated continuous wave As developed by RSSI 2.45 GHz ISM band Demodulation DDS-based Resonator-dedicated reader Amplification and digitalization V As developed by Senseor 434 MHz ISM band t Excitation Detection out Straighten Integration Thresholding Mixer Low pass filter I output (0 ) Synchronous detection using an IQ demodulator RSSI Hybrid reader general principle 2.45 GHz ISM band Signal from the antenna 0 /9 0 Mixer Low pass filter Reference Ref 1 Q output (90 )

Multiple temperature measurements Simultaneous interrogation of SAW Tags operating at 2.45 GHz (frec n sys) Thermocouples 2.45 GHz ISM band SAW-Tags

RF antenna SAW transponder: from connected switches to IoT Wireless interrogation of reactive charges sensitive to parametric changes using a SAW filter patent WO2011042557 Principle validation using a micro-switch (secured On/Off detection)

High temperature (HT) sensors Packaged sensors able to operate and measure temperature up to 700 C (and more) Designed and manufactured by frec n sys French patent application FR17/70318 SAW sensors based on two single-port resonators used for differential measurements Principal result of SAW-HOT EC project FP7/2007-2013 NMP4-SL-2009-247821

HT wireless measurement for industry This sensor was submitted to more than 100 rapid thermal cycling from 25 to 600 C, still operable Collab. with SENSeOR

Example of analog wireless sensing and IoT techniques Data transfer problem still remains Please select Wi-Fi - interrogateur-frecnsys Try then and connect to http://192.168.1.1

Conclusion Various technologies are available for RF wireless passive sensors Accessible parameters: temperature, stress and all their combination (pressure, torque, vibrations, accelerations, ), adsorption and physisorption phenomena, others... Accuracy and resolution elements SAW-tags: temperature accuracy better than 1 C over -40/+200 C, resolution better than 10 mk due to the extreme phase sensitivity Resonators: 1% of the parameter whole range when reading the sensor intermittently, better than 1 for permanent readout System band pass Max 5 khz (probably optimistic) with resonator-based interrogators Up to 100 khz using time domain interrogatosr, probably less than 1 khz with VNA-like interrogators Temperature in excess of 650 C can be measured using LGS resonators

frec n sys is waiting for your demands