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

Cubic baron nitride (cBN) thin films were grown on Si(100) and high-speed s teel substrates by reactive r.f, sputtering in an Ar/N-2 discharge using an electrically conducting boron carbide (B4C) target. The substrate electrod e 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 t hin, textured, hexagonal baron nitride (hBN) film, (2) the nucleation of cB N 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 fi lm and (2) the reactivity under humid conditions. We investigated the influ ence of the thickness, structure and surface roughness of hBN on the adhesi on of cBN films. To modify the hBN films, the pressure, substrate bias and Ar/N-2 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. (C) 1999 Elsevier Science S.A. All rights reserved.