Growth of c -axis AlN sputtered films on silicon-based substrates using 2D-TMD as nucleation layer

Abstract In RF filters based on bulk acoustic wave (BAW) resonators, AlN is a well-known piezo-active layer stacked between two molybdenum electrodes. The crystalline quality, e.g., the film texture along the c -axis of the AlN hexagonal lattice, has a direct effect on RF performances. However, the current crystal quality of AlN films has attained a level that further limits the performance of BAW devices. In these devices, AlN is grown on molybdenum, which serves as a bottom electrode, thereby inducing an improvement in AlN crystallinity through a heteroepitaxial growth effect. In this paper, we study AlN sputtered films on 2D-MoS 2 , after an NH 3 heat treatment process developed in our previous work. We compare the c -axis orientation, equi-biaxial stress and in-plane/out-of-plane strain of AlN films with thicknesses ranging between 100 nm and 1 µ m. We report (002) rocking curve (RC) measurements with values ranging from 0.8° to 1.0°. To our knowledge, such low RCs angles have never been reported in the literature for AlN sputtered 1 µ m-thick layers on silicon-based substrates. The use of 2D materials to improve the AlN nucleation not only eases the integration of high-quality and thick AlN or co-doped AlN films but also paves the way toward the growth of III-N materials via an alternative approach.