Results:

IMT Bucuresti

Etapa IV Optimizarea aplicatiei propuse si validarea modelelor pentru diferite materiale si procese tehnologice

• Vibration cantilevers with 2 μm thickness

SEM pictures of polysilicon released vibration cantilevers with 2 μm thickness /Structuri de microcantilever eliberate cu grosimea de 2 μm si electrozi din polisiliciu

First bending mode of the clamped beam visualized using Laser-Doppler Vibrometry technique (V2i Measurement)

Manufacturing of the vibrational cantilever micro-structures with electrode and 1 μm thickness

Technological processes:

•    Silicon nitride deposition – Si3N4 (300 nm) – insulator layer
•    Polysilicon deposition (T = 5800C, 150 nm) – electrode
•    Polysilicon n-type doping
•    Reactive-ion etching (RIE) of doped polysilicon (M1)
•    PECVD of silicon oxide (M2) – sacrificial layer
•    Silicon oxide etching – for pads access
•    Polysilicon deposition (T = 5800C, 1 µm) – cantilever
•    Polysilicon n-type doping
•    Reactive-ion etching (RIE) of doped polysilicon (M3)
•    Silicon oxide etching in order to release the structure

SEM pictures of polysilicon released vibration cantilevers with 1 μm thickness /Structuri de microcantilever eliberate cu grosimea de 1 μm si electrozi din polisliciu

Dissemination; Papers:

• T.V. Hoang, L. Wu, S. Paquay, A. C. Obreja, R. Voicu, R. Muller, J.-C. Golinval, L. Noels, A probabilistic model for predicting the uncertainties of the humid stiction phenomenon on hard materials, Journal of Computational and Applied Mathematics 289 · FEBRUARY 2015, DOI: 10.1016/j.cam.2015.02.022

• V. Lucas, J.-C. Golinval, S. Paquay, V.-D. Nguyen, L. Noels, L. Wu,  A stochastic computational multiscale approach; Application to MEMS resonators, Computer Methods in Applied Mechanics and Engineering  (2015), pp. 141-167 DOI information: 10.1016/j.cma.2015.05.019

• M. Michałowski, Z.Rymuza ,R.Voicu, A.Obreja, A.Baracu, R.Muller, Nanotribological Behaviour of Polysilicon Films Applied in MEMS Devices, Proceedings of the SAIT Tribology Conference  Tribology 2015-11th International Tribology Conference, 10 - 12 March 2015,University of Pretoria Conference Centre, Pretoria, South Africa  ISBN 978-0-60543-4 Tribology 2015  Proceedings (Printed) , 978-0-620-60542-7 Tribology 2015 Proceedings (on CD) , Editors: PL de Vaal, G. Fuller, SAIT (South African Institute of Tribology) , Kelvin, South Africa

• Accepted abstract: R. Voicu, C. Obreja, A. Baracu, A. Avram, R. Muller, J. Rochet , M. Pustan, MEMS Polysilicon Cantilevers for Vibrational Applications, Conf. 26th Micromechanics and Microsystems Europe Workshop-MME2015, September 20-23, 2015, Toledo, Spain

• Accepted abstract and Poster presentation: R. Voicu, A. Baracu, R. Gavrila, C. Obreja,  M. Danila, B. Bita, R. Müller, Material layers investigations for MEMS vibration sensors and biostructures applications, Conf. CSSD-UDJG 2015,  Galaţi, 4-5  June 2015

• Accepted abstract: A. Baracu, R. Voicu, C. Obreja, Design and Fabrication of Polysilicon Bridges Used for MEMS Applications, Conf. Micro and Nano Engineering-MNE 2015, 21-24 September 2015, The Hague, The Netherlands

Etapa III Optimizare sensor de vibratie de tip MEMS

• S-au proiectat si optimizat structuri MEMS de microcantilever pentru senzori de vibratie. S-au variat o serie de parametrii: lungimea cantileverului (L), latimea acestuia (w), latimea electrodului de jos (le) si pozitia electrodului de jos fata de paduri (Le). In functie de rugozitatea obtinuta pentru stratul de polisiliciu, s-au proiectat structuri cu urmatoarele configuratii (Fig. 3.1):

  w =10, 20, 40, 50 μm
  L=340,290 and 180,160 ,140,120 μm
  l_e = 20, 40, 60, 80 μm latime electrod
  L_e=40-210 μm
  t=2 μm.

Fig. 3.1 Reprezentarea schematica  a structurii de microcantilever cu electrozi

• Proiectarea dispozitivului MEMS de microcantilever pentru senzori de vibratie s-a realizat  utilizand 3 masti distincte:

  M1-pentru configurarea electrodului de jos,
  M2- deschide ferestre in oxid pentru a accesa electrozii,
  M3- cantileverul propriu-zis, Fig.3.2.

   

Figura 3.3 Imagine la microscopul optic pentru structura fabricata cu L=230 μm

• S-au realizat caracterizari mecanice ale stratului de polisiliciu (modulul lui Young)

• S-au relizat simulari cuplate electromecanice utilizand programul Coventorware pentru a determina prin analize numerice tensiunea de pull-in si deplasarile pe verticala ale structurilor proiectate.

• Realizarea unei baze de date pentru incertitudinile geometrice ale structurilor MEMS vibrationale si pentru materialele utilizate in fabricatie

Tabelul 3.1 Dimensiunile geometrice ale senzorului vibrational

Tabel 3.2 Date pentru incertitudinile structurilor MEMS vibrationale si pentru materialele utilizate in fabricatie

Tabel 3.3 Masuratori XRD. Dimensiuni cristalit si grad de cristalinitate

• Optimizarea procesului tehnologic pentru fabricare. Structurile au fost caracterizate utilizand SEM

Fig. 3.7 Structuri de microcantilever eliberate si electrozi -imagini SEM

• Diseminare rezultate:

- R. Voicu, M. Michalowski, Z. Rymuza , R. Gavrila , C. Obreja, R. Müller, A. Baracu “Design and Analysis of Polysilicon Thin Layers and MEMS Vibrating Structures”, Proc. DTIP 2014 - SYMPOSIUM on Design, Test, Integration & Packaging of MEMS/MOEMS, Cannes Côte d'Azur, France, 1-4 April 2014, p. 129-133, 2014

- V. Hoang Truong, L.Wu, M. Arnst, J-C. Golinval, R. Muller, R. Voicu, S. Paquay, L. Noels, “A probabilistic model of the adhesive contact forces between rough surfaces in the MEMS stiction context”, Book of abstracts of the 6th International Conference on Advanced Computational  Methods in Engineering, ACOMEN 2014, 23–28 June 2014

Etapa II: Realizarea experimentala de structuri MEMS  pentru senzori de vibratie

 

SEM pictures (scale 4 μm) of polysilicon samples (polysilicon with a thickness of 2μm deposited at different temperatures: 580^oC, 610^oC, 630 ^oC, 650^oC)
(IMT Bucharest)

AFM pictures -2D images  for Polysilicon samples (580^oC, 610^oC, 630^oC, 650^oC)
(IMT Bucharest)

SEM pictures of  the undoped Polysilicon microcantilever array, obtained by surface micromachining, using SiO2 as sacrificial layer (IMT Bucharest)

The first resonance frequency is a key performance characteristic of MEMS vibrometers. The resonance frequency can be predicted by using a 3-scale stochastic model:

The 3-scale procedure (University of Liege)

The different SVEs (Statistical Volume Elements) (University of Liege)

 

Papers:

Vincent Lucas, Ling Wu, Maarten Arnst, Jean-Claude Golinval, Stéphane Paquay, Van-Dung Nguyen, Ludovic Noels, „Prediction of macroscopic mechanical properties of a polycrystalline microbeam subjected to material uncertainties”, Proc. EURODYN 2014

„Investigations of  surface properties of   SiO2 and Si3N4 thin layers,  used for MEMS   vibrating structures  applications”, Rodica Voicu, Zygmund Rymuza,  Marcin Michalowski, Cosmin Obreja,  Raluca Gavrila,  Raluca Müller, Proc. Cas 2013, Vol. 1, pp.  111-114, 2013.

Etapa I: Studiu privind  tipuri de senzori de vibratie de tip MEMS
Activitate I.1  Studiul senzorilor de vibratie bazati pe tehnici MEMS

Tipuri de senzori de vibratie:

1. Senzori rezonatori
2. Senzori piezoelectrici
3. Senzori cu variatia deplasarii
4. Senzori piezorezistivi        
5. Senzori optici
6. Senzorii capacitivi

                        a                                                        b                                                         c

Fig. Exemple de senzori cu variatia deplasarii, capacitivi
a) Elementul sensibil pentru un giroscop
(U. Krishnamoorthy, R. H. Olsson III, G. R. Bogart, M. S. Baker, D. W. Carr, T. P. Swiler and P. J. Clews, "In-plane MEMS-based nano-g accelerometer with sub-wavelength optical resonant sensor," Sensors and Actuators A: Physical, vol. 145-146, pp. 283-290, 2008.)
b) Senzor de acceleratie cu deplasarea in lateral; c) Accelerometru cu deplasare longitudinala
( Clark, W.A., Howe, R.T. and Horowitz, R. Surface micromachined Z-axis vibratory rate gyroscope. Solid State Sensors and Actuator Workshop, pp. 283-287, 1996.);

Activitate I.2 Studiul materialelor  utilizate si a tehnicilor de obtinere a senzorilor  de vibratie  de tip MEMS

Senzorii de vibratie se pot clasifica in functie de modalitatea de generare a semnalului electric din miscarea vibrationala:

• generarea piezoelectrica (materiale piezoelectrice, ceramicele piezoelectrice, materiale piezoceramice, materiale piezoelectrice compozite)
• generarea electromagnetica (diverse materiale, magneti cu performante ridicate (magneti cu Neodym), sau bobinele la scara macro)
• generarea  electrostatica (polisiliciu)

Aplicatii ale senzorilor de vibratie de tip MEMS:

• monitorizarea conditiilor de functionare a oricarui sistem cu componente in miscare, care suporta vibratii (industria auto, aeronautica, centrale electrice, masini unelte, etc.)
• monitorizarea comportamentului la solicitari vibrationale ale oricarei structuri statice (cladiri, poduri, cai ferate, etc.)
• caracterizarea starii de uzura a mecanismelor in miscare
• aplicatii in geofizica
• dispozitive pentru auto-generare de energie ( energy harvesting)

Etapa II: Realizarea experimnetala  structuri MEMS  pentru senzor de vibratie
Activitatea II.1
Selectarea unei aplicatii privind  realizarea unui senzor vibrational; alegere material, proces de fabricatie

Poze SEM, structuri din SiO2