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Growth and characterization of c-axis and a-axis oriented Aluminium Nitride thin films for RF-MEMS applications

August 22 @ 3:30 pm - 4:30 pm

Speaker            : Amal Das (EE15D305)

Date                 : 2019 (22nd August)

Time                : 3.30 PM

Venue              : ESB 244

Guide               : Dr. Amitava DasGupta & Dr. M S Ramachandra Rao

 

ABSTRACT

In recent years, AlN thin films are intensively studied for the fabrication of MEMS devices because of their unique properties such as wide band gap (6.2 eV), high thermal conductivity (2.85 Wcm−1K−l ), high resistivity (1011–1013 Ω-cm), low thermal expansion coefficient (4.2×10−6  K−1 ), high breakdown field (5 MV/cm) and high acoustic velocity (11,354 m/s and 5,500 m/s) in both longitudinal and transversal mode. AlN is preferred for the fabrication of MEMS devices (e.g. FBAR, energy harvester, SAW, BAW, resonator etc.) over lead zirconate titanate (PZT) and ZnO because it is compatible with standard CMOS silicon technology. In order to get the desired properties of AlN film, it is necessary to grow AlN film in the preferred orientation (e.g. c-axis, a-axis or in m-plane). In this work, we have optimised the growth process and studied the electrical and piezoelectric properties of c-axis and a-axis oriented AlN thin films on Mo coated Si substrate as well as on Nano-crystalline diamond (NCD) films. To get c-axis oriented and a-axis oriented AlN deposition, we varied the sputtering parameters like target to substrate distance, Ar/N2 ratio, substrate temperature, sputtering pressure and RF power.The crystallinity and preferred orientation of the film was confirmed from grazing incidence x-ray diffraction (GIXRD) study. The interface between the as-grown AlN thin films and the Mo coated Si substrate was observed from cross-sectional SEM imaging, which was found well defined, flat and sharp. The electrical characterization of the c-axis and a-axis oriented AlN thin film was carried out by fabricating the metal-insulator-metal (MIM) capacitor. The piezoelectric coefficient (d33(eff)) of a-axis and c-axis oriented AlN samples were measured by double beam laser interferometry (DBLI) method. The properties of the layer structure suggest that it is suitable for fabricating high frequency MEMS resonators.

All are cordially invited.

Details

Date:
August 22
Time:
3:30 pm - 4:30 pm
Event Category:

Venue

ESB – 244
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