Low-Temperature ALE Deposition of Y2O3 Thin Films from β-Diketonate Precursors

Abstract

Yttrium oxide thin film deposition by atomic layer epitaxy (ALE) was studied at 200±425 C using Y(thd) 3 , Y(thd) 3 (bipyridyl), or Y(thd) 3 (1,10-phenanthroline) (thd = 2,2,6,6-tetramethyl-3,5-heptanedione) as an yttrium precursor, and ozone as an oxygen source. All yttrium precursors were analyzed by thermogravimetry/differential thermal analysis (TG-DTA) and mass spectrometry (MS). Soda lime glass and Si(100) were used as substrates. With all precursors, a constant deposition rate of 0.22±0.23 (cycle) ±1 was observed at 250±350 C on both substrates, indicating a surface-controlled growth and similar surface species at the deposition temperatures used. The effect of growth parameters, such as reactant pulsing times, was investigated in detail at 350 C using Y(thd) 3 . Deposited films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM) in order to determine crystallinity and surface morphology, while ion-beam analysis and X-ray photoelectron spectroscopy (XPS) were used to analyze stoichiometry and impurity levels. Infrared (IR) measurements were performed to determine the type of carbon impurity. Crystalline films with a (400) dominant orientation were obtained when depositions were carried out within the ALE window (temperature range of 250±375 C), but films deposited below 250 C were nearly amorphous. Preferential orientation changed from (400) to (222) when deposition temperatures were raised slightly above the ALE window to 375 C, where a partial decomposition of Y(thd) 3 probably takes place. Judging from the impurity levels of the films and growth rates, the adducting of Y(thd) 3 does not bring about any advantages in the ALE growth of Y 2 O 3 .

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

“…The mass spectra of Er(thd) 3 closely resemble the mass spectra of other trivalent rare earth thd chelates, e.g. Sc(thd) 3 , [28,37] Y(thd) 3 [30,38]. In these previous studies, the metal-containing fragments with strongest intensity have been the same as in the present case.…”

“…On Si(1 0 0) substrates, the widths of (4 0 0) peaks (FWHM) at 300 • C were in the order of 0.24-0.28 • . Results from the XRD measurements are in agreement with the reports for the other ALD-grown RE oxides [28,30,31]. Amorphous or slightly polycrystalline structures are typically obtained in ALD due to the low deposition temperatures.…”

Surface reaction mechanism of Y2O3 atomic layer deposition on the hydroxylated Si(100)-2×1: A density functional theory study

“…However, atomic layer deposition (ALD) has recently begun to receive attention in the deposition of a variety of rare earth oxides including Y 2 O 3 [7,8]. As a unique deposition technique, materials can be deposited layer by layer based on alternating self-limited saturated surface reactions.…”

“…For example, tris(2,2,6,6-tetramethyl-3,5-heptanedione)yttrium, Y(thd) 3 and ozone have once been employed as metal and oxygen precursors, respectively. However, the relatively low growth rate and the formation of a SiO x interfacial layer between Y 2 O 3 and Si-substrate have limited its applications [8,11,12]. Recently, the two problems related to the ALD of Y 2 O 3 thin films have been improved greatly by using Cp 3 Y (Cp = cyclopentadienyl) and H 2 O as metal and oxygen precursors, respectively [5].…”

Electrical and structural characteristics of yttrium oxide films deposited by rf-magnetron sputtering on n-Si

“…Yttrium oxide deposited on silicon by rf-magnetron sputtering, [5][6][7] electron-beam evaporation, [8][9][10] laser ablation and ion beam sputtering, 11,12 as well as by means of epitaxy 13,14 has been proposed as a candidate oxide to replace SiO 2 . The low lattice mismatch between the Si lattice parameter ͓a 0 (Si)ϫ2ϭ1.086 nm͔ and that of the Y 2 O 3 ͑1.064 nm͒, the high thermodynamic compatibility, 15 and the relatively high conduction band offset ͑ϳ2.3 eV͒ 16 with Si are among the interesting properties of this material.…”