Atomic layer deposition of rare earth oxides: erbium oxide thin films from β-diketonate and ozone precursors

Er2O3 thin films were grown onto Si(100) and soda lime glass substrates by atomic layer deposition (ALD) from Er(thd)3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedione) and ozone precursors. Temperature range studied was 200–450°C where a region of constant growth rate for Er2O3 (ALD window) was observed at 250–375 and 275–350°C on Si(100) and soda lime glass, respectively. Within the ALD window, the growth rates of Er2O3 films deposited onto Si(100) and soda lime glass were 0.25 and 0.20Å (cycle)−1, respectively. Films were polycrystalline, cubic Er2O3, and their preferred orientation changed from (400) to (222) as the deposition temperature was raised above 325°C. Below 250°C, the films were amorphous. The surface morphology studies by AFM revealed that the films were very smooth (rms=0.3–1.4nm), when deposited within the ALD window. Time-of-flight elastic recoil detection (TOF-ERD) analyses were carried out to determine stoichiometry and impurity levels and they proved the films to be nearly stoichiometric Er2O3 with some hydrogen, carbon and fluorine as impurities. Within the ALD window, the hydrogen, carbon and fluorine contents were in the order of 1.7–4.0, 0.5–1.8 and 0.7–1.7at.%, respectively.