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Improvement of the adhesion of sputter-deposited cubic boron nitride films

: Walter, H.; Bewilogua, K.; Schütze, A.; Maassen, T.


Diamond and Related Materials 8 (1999), Nr.1, S.110-113
ISSN: 0925-9635
Fraunhofer IST ()
adhesion; cubic boron nitride; sputter deposition

Cubic boron nitride (cBN) thin films were grown on Si(100) and high-speed steel substrates by reactive r.f. sputtering in an Ar/N2 discharge using an electrically conducting boron carbide (B4C) target. The substrate electrode was grounded or operated either with a d.c. or an r.f. power supply. The deposition of cBN can be subdivided into three steps: (1) the growth of a thin, textured, hexagonal boron nitride (hBN) film, (2) the nucleation of cBN and (3) the growth of the cBN phase. As a measure of the cBN content, the ratio of the infrared absorption bands near 1100 cm−1 (cBN) and 1400 cm−1 (hBN) was used. The adhesion of cBN films is still an unsolved problem. Two aspects have to be considered: (1) the high intrinsic stress of the film and (2) the reactivity under humid conditions. We investigated the influence of the thickness, structure and surface roughness of hBN on the adhesion of cBN films. To modify the hBN films, the pressure, substrate bias and Ar/N2 mixture was varied. Another way of improving the adhesion is plasma treatment of the cBN film directly after deposition. The process variations mentioned above increase the thickness of the adhering cBN films.