Flexible-CMOS and biocompatible piezoelectric AlN material for MEMS applications

Abstract

The development of a CMOS compatible flexible piezoelectric material is desired for numerous applications and in particular for biomedical MEMS devices. Aluminum nitride (AlN) is the most commonly used CMOS compatible piezoelectric material, which is typically deposited on Si in order to enhance the c-axis (002) crystal orientation which gives AlN its high piezoelectric properties. This paper reports on the successful deposition of AlN on polyimide (PI-2611) material. The AlN deposited has a FWHM (002) value of 5.1 • and a piezoelectric d 33 value of 1.12 pm V −1 , and SEM images show high quality columnar grains. The highly crystalline AlN material is due to the semi-crystalline properties of the polyimide film used. Cytotoxicity testing showed the AlN/polyimide material to be non-toxic to 3T3 cells and primary neurons. Surface properties of the AlN/polyimide film were evaluated as they have a significant effect on the adhesion of cells to the film. The results show neurons adhering to the AlN surface. The results of this paper show the characterization of a new flexible-CMOS and biocompatible AlN/polyimide material for MEMS devices with improved crystallinity and piezoelectric properties.

Flexible and Transparent Aluminum‐Nitride‐Based Surface‐Acoustic‐Wave Device on Polymeric Polyethylene Naphthalate

“…The crystal quality of a thin film directly deposited on a flexible substrate is strictly related to the temperature that the polymeric material can bear. In fact, a large mismatch due to the different thermal expansion coefficient between ceramic material and polymeric substrate usually causes cracks in the grown piezoelectric film . This constraint forces the deposition to be performed at low temperature, while the crystal quality of the piezoelectric layer is improved by depositions at high temperature .…”

Preparation of (001) preferentially oriented titanium thin films by ion-beam sputtering deposition on thermal silicon dioxide

“…However, we expected such behavior since the substrate was rotating during the Ti deposition and therefore no unique azimuthal axis is present. Consequent deposition of some layers such as AlN or ZnO over a titanium film often requires process temperatures up to 300°C [8]. Considering this fact, we exposed several samples (sample 2-7) with the optimized (001) preferential crystallites orientation to an annealing process in vacuum of 5 9 10 -7 mbar.…”

“…Crystallographic orientation of titanium thin films has to be controlled during the deposition process to obtain specific properties (e.g., mechanical, chemical) suitable for an eventually required application [6,7]. Some of recent MEMS devices use the piezoelectric effect for energy harvesting or sensing purposes [8]. Titanium has been often utilized in MEMS technology as a compatible material for fabrication of thin conductive underlying electrodes on which the piezoelectric layers are deposited [6].…”

Investigation of Implantable Antennas for Exploratory Neuroscience Studies

“…The patterned substrate was micro-roughened using reactive ion etching (100 W, 30 s, 25 sccm O 2 ) to improve the adhesion between the PI and the subsequent coating of metal (Ti:Au, 10:200 nm), which was deposited using electron beam evaporation [19]. A clean lift-off in acetone followed by an isopropanol (C 3 H 8 O) rinse results in the final antenna geometry.…”