Technical Study On Deposition Of B-C Films By MWECR CVD Method

The recent researches on B-C compounds were summarized with their properties as well as some traditional synthesis methods in the beginning. Then our synthesis method of B-C film was presented. In our experiment, B-C films were deposited using microwave electron cyclotron resonance CVD (MWECR CVD) method with B2H6 as the boron source and C2H4 as the carbon source. The effects of C2H4/B2H6 molar ratio, gas pressure, substrate temperature, and microwave power on the composition, bonding states, and deposition rate of the films were investigated.The chemical composition of the B-C film samples were characterized with Energy Dispersive Spectrum (EDS). The results suggest that C/B atomic ratio of our sample increases exponentially with C2H4/B2H6 molar ratio. An increasing gas pressure would result in an increasing deposition rate initially, and reach the maximum deposition rate of 0.293 nm/s at 0.6 Pa. Continuous increase of gas pressure would lower the deposition rate. A similar effect of the substrate temperature was observed with the maximum deposition rate of 0.227 nm/s at 100℃. On the other hand, the deposition rate increases monotonously with microwave power.Film composition and bonding states of the atoms were investigated with X-ray photoemission spectroscopy (XPS) for different sampls. The boron concentration in the samples increases as the substrate temperature increases, resulting in a decreased C/B ratio. The same effect was observed with microwave power: larger power gives sample with more boron. Also, B1s and C1s core level spectra suggest increasing B-C bonds in the film with increasing substrate temperature. So by increasing substrate temperature, boron and carbon atoms can form covalent bond easier. Similar effect of microwave power on B-C bond formation was also observed: larger power improves the B-C.