Microsystems Technology

Piezo-electrical thin films


The use of several physical effects and phenomena allows the development of a large variety of microsystems (MEMS, Micro-Electro-Mechanical Systems) for use in sensors but also in actuators.

In particular, the direct integration of certain piezoelectric materials allows the production of miniaturized systems with both sensory as well as actuator properties.

ISIT is intensively engaged in the deposition and integration of thin films of the two piezoelectrics aluminum nitride and lead zirconate titanate (PZT). On a Clusterline CLS 200 from Oerlikon it is possible to deposit AlN with a thickness up to 2 microns by means of reactive magnetron sputtering. Another module of this tool is provided for the deposition of PZT thin films by sputtering of a ceramic target.

As a complement to the PZT sputtering, Fraunhofer ISIT and Fraunhofer IST are working on a high rate PZT deposition process based on the gas flow sputtering technique (GFS) invented by Fraunhofer IST, Braunschweig. In contrast to ceramic target sputtering, GFS is a reactive sputtering process with metallic targets. Its distinctive feature is the high deposition rate of 100-150nm/min.

Using a 4-point bending measuring system by aixacct GmbH, a characterization of the deposited thin films by measuring the piezoelectric module e31, f is directly possible at ISIT . (The determination of the piezoelectric coefficient d33, f is given at the Technical Faculty of the University of Kiel.)

AlN deposition:

● process: reactive magnetron sputtering
● typ. deposition rate: 65nm/min
● typ. thickness: 500nm .. 2000nm
● bottom electrode material: sputtered Mo, evapor. Pt
● e31,f: -1,3 C/m²

PZT deposition:

● Process: reactive Gasflusssputtern
● Stoichiometry: Pb (Zr0,52Ti0, 48) O3
● typ. deposition rate: 50 nm / min
● typ. thickness: 2000nm .. 4000nm
● bottom electrode material: evapor. Pt
● e31,f: -10,5 C/m²