COMPARISON OF (CH4-O-2)-H-2 AND CO-H-2 PLASMAS FOR LOW-TEMPERATURE DIAMOND FILM DEPOSITION BY ELECTRON-CYCLOTRON-RESONANCE PLASMA-ASSISTED CHEMICAL-VAPOR-DEPOSITION

Diamond films have been deposited onto silicon substrates using C-O-H-2, gas mixtures in an electron cyclotron resonance (ECR) microwave plasma-assisted chemical vapor deposition (PACVD) system. In order to demonstrate the high degree of dissociation encountered in ECR systems, two separate gas precursor systems were used to generate nearly identical growth environments. Plasmas generated from either CO-H-2 or (CH4-O-2)-H-2 mixtures were compared chemically (by optical emission spectroscopy) and kinetically (by Langmuir probe surveys) to evaluate their degree of similarity. From these studies, preliminary insights into the dissociation of CO, O-2 and CH4 were obtained, and empirical models were developed. Films were deposited at 500 degrees C and 1.33 Pa (10 mTorr) total pressure and were characterized by scanning electron microscopy, micro-Raman spectroscopy, X-ray diffraction, elastic recoil detection and tribological evaluation. Comparison of characterization results confirmed that extremely similar films were deposited from the ''equivalent'' plasmas. In addition, lower temperature deposition (300 and 400 degrees C) without the need for active heating or cooling was demonstrated with the CO-H-2 system. From these studies it was concluded that, because of the high dissociation efficiency of ECR plasmas (at 10 mTorr), feed gas composition is less important than critical C:O:H-2 ratios.