Growth of SiO₂ and TiO₂ thin films deposited by reactive magnetron sputtering and PECVD by the incorporation of non‐directional deposition fluxes

Abstract

We have deposited TiO2 and SiO2 thin films by techniques as different as plasma‐enhanced chemical vapor deposition (PECVD) and reactive magnetron sputtering under experimental conditions where highly directional deposition fluxes are avoided. The results indicate that whatever the deposition technique employed or even the precursor gas in the PECVD technique, films share common microstructural features: a mounded surface topography and a columnar arrangement in the bulk, with the column width growing linearly with film thickness. With the help of a Monte Carlo model of the deposition, we conclude that these common aspects are explained by solely taking into consideration the incorporation of a low‐energy, isotropically directed, deposition flux onto a substrate at low temperature and under a weak plasma/surface interaction environment.

Micron‐scale wedge thin films prepared by plasma enhanced chemical vapor deposition

“…[18] The Monte Carlo simulations in panels e and in Figure 4 also show that in zone B the arrival at the substrate of particles from all directions leads to the formation of perpendicular nanocolumns, as it happens in conventional PECVD processes. [20,22] The larger width and more densely packed structure of the simulated nanocolumns in this region is another noteworthy feature agreeing with experiments (c.f. Figure 2b).…”

“…Similarly, the reproduction of the right tilting orientation of nanocolumns in zone A (c.f., Figure c‐e), must be attributed to local shadowing effects, similar to those invoked to account for the tilting orientation of nanocolumns in physical vapor oblique angle deposited thin films . The Monte Carlo simulations in panels e and in Figure also show that in zone B the arrival at the substrate of particles from all directions leads to the formation of perpendicular nanocolumns, as it happens in conventional PECVD processes . The larger width and more densely packed structure of the simulated nanocolumns in this region is another noteworthy feature agreeing with experiments (c.f.…”

“…Some principles of the method are inspired by the physical vapor deposition of thin films at oblique angles (OAD), where the oblique incidence of ballistic deposition species promotes the appearance of shadowed regions and the film nanostructuration . Yet, in conventional PECVD or magnetron sputtering depositions, precursor species usually experience multiple scattering events with the background gas molecules, loss their preferential directionality and eventually become thermalize before deposition . Despite the adverse prospects of these phenomena for controlling micro and/or nanostructuration, the herein developed PECVD method permits the tailored fabrication of wedge‐shaped thin films by the adjustment of the local density and arriving direction of precursor molecules at the deposition zone.…”

“…[19] Yet, in conventional PECVD or magnetron sputtering depositions, precursor species usually experience multiple scattering events with the background gas molecules, [20] loss their preferential directionality and eventually become thermalize before deposition. [21,22] Despite the adverse prospects of these phenomena for controlling micro and/or nanostructuration, the herein developed PECVD method permits the tailored fabrication of wedge-shaped thin films by the adjustment of the local density and arriving direction of precursor molecules at the deposition zone.…”

Perspectives on oblique angle deposition of thin films: From fundamentals to devices

“…It is formed at high thermalization degrees and a wide range of deposition angles (typically when N > 2), similar to those reported in Ref. [312] when low-energy deposition particles arrive at the film surface following an isotropic angular distribution function. Fig.…”