Thickness-dependent stress in sputtered carbon films

Abstract

The intrinsic compressive stress in thin carbon films up to 350 nm in thickness, deposited on Si(100) substrates via dc magnetron sputtering, has been measured using ex situ optical interferometry. A plateau value in compressive stress (∼1.5×109 Pa) is observed for carbon films thicker than 85 nm, but an anomalously large stress (up to 50% increase) occurs for film thicknesses between 18 and 85 nm. The carbon film stress data are interpreted in terms of a simple structural model in which the average film density influences the macroscopic stress. Ultrathin carbon films (<10 nm) in the initial stages of growth were further investigated by atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). AFM images of ∼1-nm-thick carbon films and uncoated substrates reveal topographic features with average heights of 4 and 1.5 Å, respectively, but no obvious island film growth structures. XPS measurements, in which the native SiO2 peak is used as a marker of exposed substrate area, suggest that films of ≤2 nm thickness are not continuous. The reported enhanced film stresses are therefore associated with a continuous film structure.

Review of advances in cubic boron nitride film synthesis

“…They suggested that the stress builds up until it drives the transformation to cBN. A similar stress evolution was observed in carbon films, and Puchert et al [232] attributed the quick initial rise to a transition from discontinuous nuclei to a continuous film. Puchert et al [232] suggested that this might also explain the dramatic changes in film stress observed in the initial stages of cBN film growth.…”

Smart tribological coatings with wear sensing capability

“…Non-uniformity of the strain in the crystal lattice throughout the coating thickness may also have contributed to the position and shape of the measured luminescence peaks. Other work has shown that PVD coating materials generally exhibit higher strain at the interface, with strain relaxing as the coating grows [20]. These factors may account for the slight shift and broad shape of the observed luminescence spectra in Fig.…”

A study on Si/Al2O3 paramagnetic point defects

“…Indeed, a correlation between layer thickness and internal layer stress was observed in SiO 2 layers on Si by Au et al 64 Here, the layer stress increases with decreasing layer thickness. 64 Further, a correlation between void density and layer stress release in carbon films on Si was shown by Puchert et al 65 In this context, it might be interesting to connect these observations to other thickness dependent phenomena known from Al 2 O 3 layers like blistering. 16,66,67 Here, the density of temperature-induced bubbles within Al 2 O 3 layers was observed to increase dramatically with increasing Al 2 O 3 layer thickness.…”