CHARACTERIZATION OF NUCLEATION AND GROWTH OF MW-CVD DIAMOND FILMS BY SPECTROSCOPIC ELLIPSOMETRY AND ION-BEAM ANALYSIS-METHODS

The time evolution of diamond film nucleation and growth have been inv estigated by spectroscopic ellipsometry (SE), Rutherford backscatterin g spectrometry (RES) combined with elastic recoil detection (ERD) tech niques. Diamond films were prepared using the microwave plasma CVD (MW -CVD) method on Si. In the plasma chamber, bias voltage of -200 V DC w as applied to the Si substrate for 4-12 min in H-2-CH4 (10%) to nuclea te diamond. The substrate modification by H-2 plasma cleaning and the DC bias nucleation of carbon layer followed by diamond film growth in H-2-CH4 (0.5%) gas were studied. After H-2 plasma cleaning the native 2.7 nm thick SiO2 is partly removed and the bias nucleation resulted i n a mixture of SiO2 and SIG. With longer time, a very slow increase in film thickness up to 4.6 nm and a fast enrichment of the SiC contents have been observed. Thicker diamond films were found to consist of a 2-40 nm thick porous SiC-H layer, a bulk microcrystalline diamond laye r and an amorphous capping layer 2-6 nm thick. The refractive index an d the density of the bulk layers were identical to those of the single crystal diamond mixed with about 2% graphite and hydrogen. Porous lay ered structures were found in films reaching up to 2-40% porosities. ( C) 1997 Elsevier Science S.A.