Low-temperature ALE deposition of Y2O3 thin films from beta-diketonate precursors

Yttrium oxide thin film deposition by atomic layer epitaxy (ALE) was studie d at 200-425 degreesC using Y(thd)(3), Y(thd)3(bipyridyl), or Y(thd)(3)(1,1 0-phenanthroline) (thd = 2,2,6,6-tetramethyl-3,5-heptanedione) as an yttriu m precursor, and ozone as an oxygen source. All yttrium precursors were ana lyzed by thermogravimetry/differential thermal analysis (TG-DTA) and mass s pectrometry (MS). Soda lime glass and Si(100) were used as substrates. With all precursors, a constant deposition rate of 0.22-0.23 Angstrom (cycle)(- 1) was observed at 250-350 degreesC on both substrates, indicating a surfac e-controlled growth and similar surface species at the deposition temperatu res used. The effect of growth parameters, such as reactant pulsing times, was investigated in detail at 350 degreesC using Y(thd)3. Deposited films w ere characterized by X-ray diffraction (XRD) and atomic force microscopy (A FM) in order to determine crystallinity and surface morphology, while ion-b eam analysis and X-ray photoelectron spectroscopy (XPS) were used to analyz e stoichiometry and impurity levels. Infrared (IR) measurements were perfor med to determine the type of carbon impurity. Crystalline films with a (400 ) dominant orientation were obtained when depositions were carried out with in the ALE window (temperature range of 250-375 degreesC, but films deposit ed below 250 degreesC were nearly amorphous. Preferential orientation chang ed from (400) to (222) when deposition temperatures were raised slightly ab ove the ALE window to 375 degreesC, where a partial decomposition of Y(thd) 3 probably takes place. Judging from the impurity levels of the films and g rowth rates, the adducting of Y(thd)3 does not bring about any advantages i n the ALE growth of Y2O3.