INVESTIGATIONS ON THE STRUCTURE OF BORON-NITRIDE FILMS

Boron nitride films fabricated by ion beam assisted deposition (IBAD) have been analyzed using polarized infrared reflection spectroscopy (P IRR), generalized variable angle of incidence spectroscopic ellipsomet ry (gVASE), elastic recoil detection analysis (ERDA), and in situ elli psometry during plasma etching. Hexagonal boron nitride (h-BN) films, with properties very similar to the interface material on top of which cubic boron nitride (c-BN) nucleates, have been prepared. PIRR and gV ASE results show that these films are biaxially anisotropic. The h-BN basal planes are aligned to the surface normal and exhibit a preferent ial alignment parallel to the direction of the boron vapor stream. Thi s behavior is unrelated to the substrate crystal orientation. The obse rved preferential alignment of the h-BN basal planes cannot be explain ed by compressive stress or ion beam induced processes. The biaxially anisotropic optical properties of these h-BN films can be employed to fabricate special optical thin film devices but require the applicatio n of generalized ellipsometry also for in situ measurements. (C) 1997 Elsevier Science S.A.