Deposition of AlN films for acoustic biosensors by deep oscillation magnetron sputtering: effect of bias voltage

The present study showed that Deep Oscillation Magnetron Sputtering (DOMS) has an excellent potential to produce AlN films for biosensing applications. However, careful control of the process parameters is required to attain the desired features. Al/AlN/Al films deposited via DOMS on Si wafers were extensively characterized to assess this potential. The resulting microstructures were examined by glancing angle x-ray diffraction, scanning electron microscopy coupled with energy dispersive microanalysis, atomic force microscopy, and x-ray photoelectron spectroscopy. The results indicated that there is a strong effect of the bias voltage (Vb) applied to the substrate on the structure of the Al/AlN/Al films and that it can be divided in two regimes. The low Vb regime produced the best features of the AlN films for the present application. These included a strong (002) orientation, low residual stress, and uniform surface roughness. In the high Vb regime, these features degraded. The effects were associated to the nature and energy of the impinging species as a function of Vb.