The MEMS-pie project:
Piezoelectric microsystems from the laboratory to production

                                              

  Sixth Framework Programme

 

Performance

Performance and uniformity across the wafer
The transversal piezoelectric charge coefficient e31,f was measured at 10 V and frequencies between 0.1 and 10 Hz using the new method developed by the project:

Frequency [Hz]

e31,f  [C/m2]

0.1

15.1

1

14.4

10

14.1


Automated measurements of relative dielectric permittivity at 0 V and 1 kHz on more than 200 devices showed that 98% were within +/- 16% of the average (88% were within +/- 7%). Similar measurements of the dielectric dissipation factor showed that 99.5% were within +/- 34% of the average (86% were within +/- 17%). The average values and standard deviations are shown in the table below.

 

Average value

Standard deviation

Relative dielectric permittivity, er

1130

51 (4,5%)

Dielectric dissipation factor, tand

0.029

0.0032 (11%)

Fatigue tests
A 5 kHz fatigue signal at +/- 25 V was applied to a typical cantilever. After 2•107 bipolar fatigue cycles, less than 10% reduction of the remanent polarisation was observed, as shown in the hysteresis loops below.

  
Ferroelectric hysteresis loops recorded before fatigue test. The size of the cantilever was 300 x 60 µm. The curves were recorded using an aixACCT Systems TF 2000 ferroelectric analyser.
 
Ferroelectric hysteresis loops recorded after fatigue test. The size of the cantilever was 300 x 60 µm. The curves were recorded using an aixACCT Systems TF 2000 ferroelectric analyser.
 
Development of the polarisation with the number of cycles during fatigue test.
 Small deflections
Cantilever deflection has been studied by white light interferometry (WLI). The deflection of the longest cantilevers (800 µm long) was 8.8 µm out of the wafer plane, thus only 1.1 %. The measurements were made after poling of the devices.
  
SEM image of cantilevers with various lengths (FEI Company, The Netherlands).Topography map of the same structure as the SEM image, recorded by white light interferometry. Only 1.1 % deflection out of the wafer plane was observed.

Published October 27, 2006

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