3.4. AlN stress analysis
While fabricating thin film AlN force sensors, cracks appear on the AlN thin film when deposited at the Au-SiO2 step edge possibly due to a large stress differences in AlN on different materials. Stressan alysis was conducted on the AlN thin films using the Tencor FLX-2320 stress analyzer.AlN (∼500 nm) was deposited on Si, SiO2(300 nm), Al2O3(300 nm) and Ti/Au (50 nm) at the same time using same param-eters described earlier. The stress is calculated from the curvature before and after the deposition of AlN using the Stoney formula: