Depth resolved comparative investigation of phase formation and stress build-up in cubic boron nitride films

• Published in: Thin solid films 2001-11, Vol.398, p.279-284
• Main Authors: Klett, A, Freudenstein, R, Kulisch, W, Ye, M, Delplancke-Ogletree, M.P
• Format: Article
• Language: English
• Subjects: Cubic boron nitride; ECR-CVD; Ion beam assisted deposition; Stress
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/S0040-6090(01)01396-7

Cubic boron nitride films have been deposited by means of ion beam assisted deposition (IBAD) and electron cyclotron resonance plasma CVD. Specially designed silicon cantilever substrates were used which allow precise stress measurements. After deposition, the films were etched back in steps of approximately 5–20 nm by Ar ions. After each step, the stress, the thickness and also FTIR spectra were measured. By this means, the stress distribution, the development of the c-BN content and also the thicknesses of the h-BN nucleation layer and the transition layer h-BN → c-BN could be determined. Major differences were found between the two types of layers: IBAD films possess a nucleation layer with a thickness of 15–20 nm and a stress of approximately 3 GPa. After c-BN nucleation, a transition region of approximately 20 nm is observed in which the c-BN content rapidly increases to the final value, which can exceed 90%. However, the c-BN top layer possesses a high compressive stress with values up to 20 GPa. In contrast, for ECR films the transition from the h-BN nucleation layer to the c-BN top layer is much more gradual (nucleation layer thickness approx. 50 nm). Simultaneously, the c-BN content of the top layer is limited to approximately 70% while its stress is much lower (2–3 GPa). The reasons for these differences in phase formation and stress build-up are discussed in terms of the differences between the two techniques.