Acoustic behavior and elastic properties of amorphous SiN_x film studied by surface brillouin scattering

摘要

Amorphous silicon nitride (SiN_x) has been studied in recent years with a view to various applications in the microelectronics industry as well as in surface acoustic wave (SAW) devices, such as resonators, filters, and delay lines with electronic circuity on semiconductor substrates. The properties of these SiN_x films remain uninvestigated, owing to the small value of the film thicknesses. Hickernell et al. used interidigital transducer (IDT) structure to study the SiN_x film on GaAs substrate, where only Rayleigh surface acoustic wave (SAW) was detected. In this report, we investigate the acoustic wave behavior and elastic properties of two SiN_x films of 600 nm with different densities (Sample A, 2.84 g/cm~3, and B, 2.53 g/cm~3) on silicon substrate by the surface Brillouin scattering (SBS) technique. We report the behavior not only for the Rayleigh SAW but for the Sezawa, pseudo-Sezawa and longitudinal guided waves as well. Observations of these modes allow extraction of all elastic constants of the film and, hence, discussion the effects of the film density on the various acoustic modes and elastic properties of the films.