A novel method of fabricating ZnO/diamond/Si multilayers for surface acoustic wave (SAW) device applications

Abstract A novel process for fabricating ZnO/diamond/Si for a surface acoustic wave device is as follows: to form a trench of 10 μm in depth, the Si wafer is chemically etched by employing the SiO 2 layer as a mask. Selective growth of polycrystalline diamond film is carried out by a microwave plasma CVD using nominal conditions of 700 W microwave power, 40 torr pressure, 0.5% CH 4 /H 2 ratio, 630 °C temperature, and −200 V bias enhancement for initial nucleation. After removing the SiO 2 layer, indirect bonding of a Si handle wafer is performed at low temperatures of approximately 90 °C. Finally, the bottom Si wafer is mechano-chemically polished until the surface (backside) of the diamond is exposed. Raman and field emission SEM observations show that a high quality diamond film is selectively grown only on the trenched Si region. It has also been found from the AFM results that the backside surface roughness of the exposed diamond film is measured to be lower than 10 nm.