Preparation of cubic boron nitride films by reactive sputtering from a boron carbide target

PVD sputter deposition of cubic boron nitride (cBN) on Si(001) was carried out using electrically conducting B4C as target material. While the target was powered by a r.f. generator, the substrate electrode was connected to a d.c. power supply or a d.c. pulse generator. The d.c. substrate bias was varied between -150 and -200 V. As reactive sputter gas we used an Ar-N-2 mixture with a N-2 content of 10%. The cBN content was determined using the intensity ratio of the infrared absorption bands of the cubic and hexagonal phases (near 1100 and 1400 cm(-1), respectively). The thickness of the deposited films was about 0.2 mu m. The delamination process of films thicker than this was studied using scanning electron microscopy (SEM). It turned out that the beginning of the growth of the cubic phase could be correlated with an increase of the measured current at the substrate electrode. Thus, the substrate current change could be used to monitor the cBN content in the films. Additionally, some results are presented from investigations where the substrate electrode was powered by a d.c. pulse generator.