IMPROVEMENT OF THE ADHESION OF SPUTTERED CUBIC BORON-NITRIDE FILMS

Cubic boron nitride (cBN) films were prepared by reactive r.f. sputter ing in an Ar-N-2 discharge using an electrically conducting boron carb ide (B4C) target. The substrate table was either powered by an r.f. ge nerator or connected to a d.c. power supply. The films were deposited on polished Si(001) and high speed steel substrates. As a measure of t he cBN content the ratio of the IR absorption bands near 1100 cm(-1) ( cBN) and 1400 cm(-1) (hexagonal BN (hBN)) was used. The temperature du ring cBN growth did not exceed 400 degrees C. The thickness of the spu ttered films was in the range <0.4 mu m. A variation of the d.c. subst rate bias showed that in the range between -130 and -200 V a window wa s found where it was possible to move from the growth of hBN to that o f cBN. Improved adhesion even under humid conditions was found by sput tering an hBN buffer layer while adding 2% of hydrogen to the nitrogen sputter gas. The subsequent grown cBN film was sputter deposited in p ure nitrogen. Nevertheless we found 3 at.% of hydrogen diffused from t he hBN into the cBN film. The hydrogen could be removed after heating the films up to 600 degrees C. (C) 1997 Elsevier Science S.A.