Hard amorphous CSixNy thin films deposited by RF nitrogen plasma assisted pulsed laser ablation of mixed graphite/Si3N4-targets

Carbon-silicon-nitride thin films were grown on (100) oriented silicon subs trates by pulsed laser deposition (PLD) assisted by a RF nitrogen plasma so urce. Up to about 30 at% nitrogen and up to 20 at% silicon were found in th e hard amorphous thin films by RES, XPS, and SNMS in dependence on the comp osition of the mixed graphite/Si3N4-PLD target. Due to incorporation of 10% Si3N4 to the PLD graphite target the CSixNy films show slightly increased universal hardness value of 23 GPa (at 0.1 mN load force, reference value f or silicon substrate 14 Gpa), increased plastic hardness (67 instead of 61 GPa), but strongly decreased elastic modulus (from 464 to 229 GPa) compared to the corresponding carbon nitride him without silicon. The internal comp ressive stress of the CSixNy films showed a maximum of 5.5 GPa at a film th ickness below 50 nm and decreased down to about 1.5 GPa for film thickness exceeding 100 nm. X-ray photoelectron spectroscopy (XPS) of CSixNy film sur faces shows clear correlation of binding energy and intensity of fitted fea tures of N 1s, C 1s, and Si 2p peaks to composition of the graphite/Si3N4 t arget and to nitrogen flow through the plasma sourer, indicating soft chang es of binding structure of the thin films due to variation of PLD parameter s. Increasing carbon double and triple bonding of the CSixNy films in depen dence on the deposition process as identified by FTIR and Raman spectroscop y correlates with decreasing nanohardness. The results demonstrate the capa bility of the plasma assisted PLD process to deposit hard amorphous CSixNy films with variable chemical binding structure and corresponding mechanical properties. (C) 1999 Elsevier Science S.A. All rights reserved.