Microstructure evolution of AlN films deposited under various pressures by RF reactive sputtering

Wurtzite AlN (2H-AlN) films were deposited on p-type Si(100) by RF planar magnetron reactive sputtering under various pressures at a relatively low temperature (350 °C). X-Ray diffraction (XRD) and selected area electron diffraction (SAD) were used to study the microstructural features of the deposited films. XRD results showed that with the decrease in sputtering gas pressure, the preferred orientation of AlN films changed from (100) to (002). SAD results confirmed that a strong (100) texture existed in the films with (100) preferred orientation. Polycrystalline diffraction rings were recorded for the film where preferred orientation was not obvious. The AlN film deposited at 2 mtorr exhibited improved grain orientation along the c-axis. A further decrease in sputtering pressure to 1.4 mtorr produced an AlN film with two-domain structure instead of a perfect single crystal.