Integration of a novel electrochemical
tuning scheme (<5V) with MEMS
surface micromachined resonators
S. Enderling1, C.L. Brown III2, M. Balakrishnan2, J. Hedley3, J.T.M. Stevenson1, S. Bond1,
1
3
3
2
2
1
C.C, Dunare , A.J. Harris , J.S. Burdess , M. Mitkova , M.N. Kozicki and A.J. Walton
1
Scottish Microelectronics Centre, University of Edinburgh, Edinburgh, UK, E-mail: stefan.enderling@ee.ed.ac.uk
Center for Solid State Electronics Research, Arizona State University, Tempe, USA
3
School of Mechanical and Systems Engineering, University of Newcastle, Newcastle upon Tyne, UK
2
1. Introduction
3. Experiments
A novel electrochemical silver (Ag) deposition mechanism
has been integrated into MEMS microbeam resonators
for the purpose of frequency tuning. This tuning mechanism
is electrically controllable, low voltage (<5V) and real time.
Microresonators
were wire bonded
for deposition and
tuning experiments.
2. Concept and Integration
Fig.3. Optical workstation
for characterisation of
Ag deposited frequency
tuning of MEMS
microresonators.
Ag deposition is induced by a DC voltage between a silver
(Ag) anode and aluminium (Al) cathodes (Fig.1). Ag
deposition alters mass and stiffness of resonators and
therefore their frequency.
I. Ag deposition tests:
Fig.4 shows Ag mass
deposition as a result of
3V DC bias between
anode and cathode.
(a)
Fig.4. Ag deposition of microbeams
caused frequency changes of
(a) -1%, (b) +6% in 16 min.
(b)
II. Frequency tuning:
Ag mass tuning with 1.5V between anode and cathode (Fig.5).
(b)
Fig.5. Ag deposited frequency change
of -3.27% with 1.5V in 13 min.
(a) Frequency spectra and (b) Ag
deposited on microbeam.
Fig.1. Polysilicon microbeam with solid electrolyte, Ag anode
and Al contacts.
Integration of Ag deposition mechanism was performed
after fabrication of polysilicon MEMS resonators (Fig. 2).
(a)
Ag deposition with 2V caused mass and stiffness changes
along the microresonator (Fig.6).
(a)
(b)
Fig.6. Frequency change
of +10.7% and -6.3% with 2V.
(a) Frequency vs. time, (b) Frequency
spectra and (c) Ag deposited on
microbeam.
(c)
4. Conclusions
The reported Ag mass-transfer by electrodeposition
mechanism has been demonstrated as a technique for
dynamic in-situ, low voltage frequency tuning of MEMS
resonators.
Fig.2. Integration process.