Mechanical and Chemical Properties of CB x N y and CSi x N y Thin Films Grown by N*-Plasma Assisted Pulsed Laser Deposit
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Mat. Res. Soc. Symp. Proc. Vol. 593 ©2000 Materials Research Society
the deposited CBxNy thin films in dependence on PLD parameters employing X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, nanoindentation measurements, X-Ray diffraction (XRD) and surface profilometry. Our detailed studies on CSixNy thin films [7, 9] are used as references for discussion of the CBXNy system. Here we compare CSixNy and CBxNy thin films which were deposited with similar PLD and nitrogen plasma conditions. EXPERIMENTAL CSiXNy, and CBxNy thin films with typical thickness of about 0.2 to 0.5 jim were grown on single crystalline silicon (100) substrates by PLD [8, 9, 14, 15] in high vacuum environment. We use a KrF excimer for ablation of mixed carbon/Si 3N4 and carbon/BN targets. The PLD process is assisted by a RF nitrogen plasma source. A detailed description of the used PLD process is given elsewhere [7]. For deposition of the CBXNy and CSixNy films we used carbon targets with 0%, 5%, 10%, 25%, and 50% BN or Si 3N 4 content, respectively. All analytical characterisations of the deposited films were carried out ex situ. We measured the radius of the curvature of the substrate before and after the film deposition using a VEECO "DEKTAK 3030" surface profiler. Macroscopic bending changes of the substrates by internal stress of the films allows the calculation of stress values in the deposited films using Stoney formula [see 7]. The depth-sensing hardness testing system NANO1NDENTERO II (with a Berkovich indenter) was used to measure mechanical parameters of the thin solid films. I XPS measurements were performed using a ESCALAB220-iXL (Fisons) with monochromatized Al K0 radiation [see 8]. Further information about chemical bonding was obtained from FTIR spectrometry employing a Bruker IFS 113v spectrometer and by Raman spectroscopy using a 'DILOR XY 800' spectrometer at 514.53 nm excitation wavelength. RESULTS AND DISCUSSION Chemical composition and bonding analysis by XPS For determination of the chemical film composition we used XPS spectra. More detailed results of the effect of the target composition on the elemental composition for CSixNy films using XPS, SNMS and RBS we have given in [7]. Figure 1 compares the film composition of CBxNy and CSixNy in dependence on target composition. In general, an increasing content of N and Si or B in the deposited films correlates to an increasing admixture of Si3N 4 or BN in the graphite PLD target, respectively. This underlines the general advantage of the PLD process, namely the good transfer of stoichiometry from target to substrate even for complicated multielement compounds [14]. However, a remarkable decrease of nitrogen content at 5% Si 3N4 admixture in comparison to the pure graphite target is caused by the appearing Si-C bonds, which reduce the C-N bonds [7]. CBxNy and CSixNy films show similar nitrogen and carbon compositions at higher admixture. Compared to silicon there is a boron deficiency in the films. Obviously, the in
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