Study of tungsten deposited on amorphous Si, Si (111) and SiO2 using direct-current magnetron sputtering

Tungsten (W) commonly serves as the electrode layer or acoustic reflector layer for the highly columnar growth of AlN piezoelectric thin films used to fabricate film bulk acoustic resonators in power applications. The structure of W film directly influences the texture of AlN thin films above. Moreover, the surface morphology and texture of W thin films are influenced by the substrate materials. In this study, the effects of different underlays on the characteristics of W films deposited using direct-current magnetron sputtering are compared. The results show that W thin film deposited on SiO2 has well-orientated crystallization, dense microstructure, the smallest RMS and the lowest electrical resistivity. W thin film deposited on Si (111) has the worst RMS and electrical resistivity but a common residual stress and crystallization. W deposited on amorphous Si (α-Si) presents column-like microstructure, the lowest residual stress but a common RMS and electrical resistivity. Since the substrate materials have direct impacts on the resonators it is necessary to take these impacts into account during the design stage of filters or sensors based on film bulk acoustic