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Study of Cr5Si3 electrodes on langasite surface acoustic wave resonators for high temperature sensing
J Streque, M.-A Soussou, F Bartoli, Sami Hage-Ali, A Taguett, Thierry Aubert, T Mazingue, M Lomello, O Elmazria
To cite this version:
J Streque, M.-A Soussou, F Bartoli, Sami Hage-Ali, A Taguett, et al.. Study of Cr5Si3 electrodes on
langasite surface acoustic wave resonators for high temperature sensing. IEEE International Ultra-
sonics Symposium 2018, Oct 2018, Kobe, Japan. �hal-03032746�
J. Streque 1 , M.-A. Soussou 1,2 , F. Bartoli 1,3 , S. Hage-Ali 1 , A. Taguett 3 , T. Aubert 3 , T. Mazingue 2 , M. Lomello 2 , O. Elmazria 1
1 Institut Jean Lamour - CNRS - Université de Lorraine (UMR 7198) - Nancy, France
2 Laboratoire SYMME, Polytech Annecy Chambéry - Université de Savoie, Annecy-Le-Vieux, France
3 LMOPS EA 4423, CentraleSupélec - Université de Lorraine - Metz, France
Study of Cr 5 Si 3 Electrodes on Langasite Surface Acoustic Wave Resonators for High Temperature Sensing
0.1 1 10 100
0.6 0.8 1.0 1.2 1.4
Floating power on target Substrate @ 200 V
Substrate @ 300 V
S i/ C r co n te n t
Pressure (mbar)
Many piezoelectric materials are viewed as potential candidates for high temperature SAW applications, including langasite (LGS) and AlN. Only a few metals or alloys can withstand such temperatures, among them platinum and iridium based alloys or nanocomposites. These materials cannot be considered when high quality factors are required, due to their higher resistivity and density. The (Cr, V)-Si system was previously studied, but has never been proposed as a solution for SAW electrodes, in spite of its high thermal stability, lower density (about 6 g/cm 3 ) and decent resistivity. This study focuses on the development of Cr 5 Si 3 alloy deposition for its use in LGS- based resonators, aiming at wireless applications.
Context for High Temperature Sensing Abstract
Batteryless Wireless
Easy
identification
Development of SAW resonators as compliant candidates
to fulfill these requirements
Cr 5 Si 3 thin film elaboration
Relying on High Temperature compatible piezoelectric substrates
- Langasite LGS (High stability perovskite, parabolic temperature behavior)
- Aluminum nitride (Large bandgap, high resistivity semiconductor, linear TCF) Looking for trade-off for the choice of IDT electrodes
- Low resistivity, decently stable with temperature - High thermal stability / Passivation
- Low density, low hardness - Inexpensive
Reaching trade-offs for IDT electrodes
Resonator design for first HT experiments - Synchronous design
- Wavelengths between 5 and 16 µm
- Aperture = 40·λ, 100 pairs, 2 x 200 reflectors - Electrodes choice: Cr 5 Si 3 , 200 nm
ArcelorMittal: consortium’s end-user
Sensor
Cr-Si Binary diagram
High Temperature SAW characterizations Conclusion and perspectives
CrSi behavior: SIMS experiments
SIMS experiments for 1 hour at 500°C and 700°C
Poster Presented at IUS 2018, Kobe, Japan
Frequency behavior of LGS-based resonators: Cr 5 Si 3 vs Al electrodes
Van der Pauw Resistivity on thin films of Cr 5 Si 3 Room Temperature and High Temperature behaviors
of LGS resonators with Cr 5 Si 3 electrodes
High temperature, harsh environments
Exploration of Cr 5 Si 3 for SAW resonator electrodes
- Approach: reaching a good trade-off between temperature range, low resistivity, low density, thermal stability…
- Cr 5 Si 3 shows good thermal stability up to 600°C
- Resistivity remains high, but rather steady with temperature Future strategies for the improvement of Cr 5 Si 3 electrodes
- Initial anneal of electrodes, for better thermal stability - Integration of a passivation layer
- Study of Cr 5 Si 3 with substrates less prone to interdiffusion (AlN / Sapphire…)
- Extension to Cr-V-Si ternary alloys
Future work on integration of Cr 5 Si 3 electrodes
- Optimization of LGS-based and AlN-based resonators equipped with Cr 5 Si 3 electrodes
- Further work on Cr 5 Si 3 aging behavior
Other study on AlN / Sapphire optimization for wireless HT SAW sensors (IUS 2018 Poster)
Optimization of Al/AlN/Sapphire Acoustic Wave Sensors for High Temperature Wireless Applications
Al
Usual candidates
Pt Cr
Perfect for low temperature Light, soft metal
Temperature limited (600°C)
Good thermal stability Heavy, very large density Expensive
Medium thermal stability Large density
0 100 200 300 400 500 600 140
160 180
R es is ti v it y ( µ Ω . cm )
Temperature (°C)
Before annealing After annealing
0 100 200 300 400 500 600 459
460 461 465 466 467
Al electrodes Cr 5 Si 3 electrodes
F re q u en cy ( M H z)
Temperature (°C)
0 500 1000 1500
10 0 10 1 10 2 10 3 10 4 10 5 10 6
C o u n ts
Time (s)
Cr Si O La Ga 1h @ 500°C
0 500 1000 1500
10 0 10 1 10 2 10 3 10 4 10 5 10 6
C o u n ts
Time (s)
Cr Si O La Ga 1h @ 700°C
0 200 400 600 800 1000
100 150 200 250
R T r es is ti v it y ( µ Ω .c m )
Anneal temperature (°C)
CrSi / LGS 1h anneal 6h anneal
Other candidates to explore:
Cr-Si alloys
Lower density than most metals / semi-metal alloys More resistive than Pt…
…But more steady with temperature than Al Might be prone to diffusion…
…But expected to have good thermal stability
Trade-off to be investigated
Cr 5 Si 3 alloy
First investigations on bulk alloys - Investigated system: Cr-Si
- Alloys prepared in electric arc furnace - Samples followed by Thermogravimetry
Investigation of Cr 5 Si 3 for thin films
- Prepared by DC sputtering from Cr-Si target - Optimization of parameters:
- Power on target
- Floating / Set potentials on substrate - Chamber pressure…
Cr 5 Si 3 selected as trade-off between low density and high temperature stability
Si target with Cr inserts
Stoichiometry adjustment
SIMS experiments after 1 hour
- Diffusion into LGS is very limited, up to 600°C - Slight surface oxidation
SIMS experiments after 6 hours - No further diffusion into LGS
- Oxidation layer is strongly slowed down
Good potential for light, stable electrodes up to 600°C
289 290 291
-30 -25 -20 -15 -10 -5 0
|S 1 1 | ( d B )
Frequency (MHz)
30°C 100°C 200°C 300°C 400°C 500°C
285 290 295 350 355 360
-35 -30 -25 -20 -15 -10 -5 0
|S 1 1 | ( d B )
Frequency (MHz)
Wavelengths:
6.5 µm 8 µm
Resistivity monitoring of Cr 5 Si 3 IDT electrodes
Measurements up to 550°C achieved with Cr 5 Si 3 electrodes
Higher resistivity than Pt, but reasonable steadyness with temperature
1-hour and 6-hour long anneals at 600°C exhibit comparatively lower resistivities:
importance of initial anneal of electrodes
RF characterizations
Cr 5 Si 3 composition
[email protected]
Aknowledgments: Project funded by Agence Nationale de la Recherche, ANR (SALSA Project) French PIA project "Lorraine Université d’Excellence" (ANR-15-IDEX-04-LUE)
20 40 60 80 100 120
0 1000 2000 3000 4000 5000
2 θ (°)
Cr
5 Si
3 Cr
5 Si
3 /LGS LGS
In te n si ty ( a. u .)
45 50
A
