Study of hafnium oxide thin films deposited by RF magnetron sputtering under glancing angle deposition at varying target to substrate distance

Glancing angle deposition of HfO2 thin films by RF magnetron sputtering technique has been explored with respect to two vital deposition parameters visualizing angle of deposition (at 82 degrees and 86 degrees glancing angles) and target to substrate distance, D-TS in the range 70-125 mm. AFM and spectroscopic ellipsometry measurements show that at optimum D-TS of 110 mm and glancing angle 82 degrees, the films exhibit nanostructures with an estimated lowest refractive index similar to 1.63 at 550 nm. For both the deposition angles, with decrease in D-TS the round shaped grains of the film surface as obtained from AFM images are found to coalesce and produce films with elliptical shaped grains at shorter target to substrate distance. With increase in D-TS the deposition rate first decreases up to D-TS = 110 mm and subsequently increases. The phenomenon has been ascribed to the competition between reduced deposition flux density and increased sticking coefficient due to decrease in adatom kinetic energy with the increase in D-TS GIXRD measurement reveals that all the films exhibit monoclinic crystal structure. At lower D-TS, the crystallinity has improved with increase in deposition angle whereas at higher D-TS (>90 mm) the crystallinity becomes poorer with increase in deposition angle. The fact has been explained in light of variation of shadowing effect and deposition rate. (C) 2015 Elsevier B.V. All rights reserved.