ELECTRON-CYCLOTRON-RESONANCE PLASMA DEPOSITION OF CUBIC BORON-NITRIDE USING N-TRIMETHYLBORAZINE

N-Trimethylborazine has been used as precursor in a downstream electron cyclotron resonance (ECR) plasma process to deposit cubic boron nitride (c-BN). N-Trimethylborazine ((CH3-N-B-H)3) is a non-corrosive and non-explosive liquid with a low toxicity. As plasma gas an argon-nitrogen mixture was used and N-trimethylborazine vapour was fed into the downstream region of the ECR plasma source. BN deposits on silicon (111) were characterized by IR spectroscopy, electron probe microanalysis and X-ray diffraction. The formation of nanocrystalline c-BN depends strongly on the process parameters and requires a substrate temperature of above 800-degrees-C. Furthermore, the application of a negative substrate bias-in our experiments achieved with a low frequency (100-450 kHz) generator-is essential to increase the c-BN fraction of the deposit. As shown by IR spectroscopy, a stepwise transition from hexagonal BN into wurtzite-type BN and finally into c-BN takes place by changing the deposition conditions. From these observations some conclusions concerning the growth mechanism of c-BN can be derived. Owing to the merits of N-trimethylborazine, its processing-compared with that of diborane or boron trihalides-is uncomplicated and promising for future applications of c-BN.