Surface-Controlled Deposition of Sc₂O₃ Thin Films by Atomic Layer Epitaxy Using β-Diketonate and Organometallic Precursors

Abstract

Scandium oxide thin film deposition by atomic layer epitaxy was studied at 175-500 °C using Sc(thd) 3 (thd ) 2,2,6,6-tetramethyl-3,5-heptanedione) and (C 5 H 5 ) 3 Sc as scandium precursors. A constant deposition rate of 0.125 Å (cycle) -1 was observed at 335-375 °C on Si(100) and soda lime glass substrates with Sc(thd) 3 and O 3 . The use of H 2 O 2 as an additional oxidizer slightly increased the deposition rate to 0.14 Å (cycle) -1 . When (C 5 H 5 ) 3 Sc and H 2 O were used as precursors, the growth rate of Sc 2 O 3 was significantly higher, viz., 0.75 Å (cycle) -1 at 250-350 °C. The effects of growth parameters such as reactant pulsing times were investigated in detail to confirm the surface-controlled growth mechanism. The crystallinity and surface morphology of the films were characterized by XRD and AFM, while ion-beam analysis (time-of-flight elastic recoil detection analysis) was used to determine the stoichiometry and impurity levels. Crystalline thin films with (111) as the dominant orientation were obtained on Si(100) when depositions were carried out at 300 °C or above from Sc(thd) 3 and O 3 precursors, while films deposited from (C 5 H 5 ) 3 Sc and H 2 O were polycrystalline regardless of the deposition temperature. When films were deposited at 300 °C onto Si(100), the preferred orientation changed from ( 111) to (100) when the film thickness exceeded 200 nm. Films were stoichiometric when deposited from Sc(thd) 3 /O 3 below 450 °C or from (C 5 H 5 ) 3 Sc/H 2 O at 250 °C or above. When the films were deposited from Sc(thd) 3 /O 3 , the carbon content was below 0.1 atom % regardless of the deposition temperature, whereas the hydrogen content decreased to below 0.1 atom % when the deposition temperature was increased to 375 °C. The C and H contents of the films, deposited from (C 5 H 5 ) 3 Sc/H 2 O at 300-400 °C, were around 0.1 and 0.5-0.3 atom %, respectively.

Scandium oxide deposited by high-pressure sputtering for memory devices: Physical and interfacial properties

“…Among them, we propose the use of silicon nitride ͑SiN x ͒ as interfacial layer between high-k and silicon to reduce the EOT of the structure. 13 Up to the moment, Sc 2 O 3 thin films with suitable properties are successfully deposited by atomic layer deposition ͑ALD͒, 14 but a wide variety of precursor gases are under study and no universal precursor gases are today used. It is important to note that the main drawback of this technique is the complexity in controlling the chemistry of the precursors in order to achieve the completeness of the reactions involved.…”

Tris(2,4‐pentanedionato)scandium(III) as a Precursor for Plasma‐Assisted Liquid Injection CVD to Deposit Nanocrystalline Scandia Thin Films

“…In addition, scandia films have been prepared by direct evaporation of metallic Sc followed by subsequent oxidation of the resulting scandium film. [20] Selflimiting deposition of Sc 2 O 3 thin film by atomic layer deposition (ALD) using Sc(tmhd) 3 has been established earlier, [21] however the poor thermal stability of some of compounds will limit their use in ALD. CVD of scandium oxide from the complexes of Sc(tmhd) 3 , Sc(tmod) 3 , Sc(mhd) 3 , Sc(EDMDD) 3 , Sc(mmp) 3 , and Sc(amd) 3 have been carried out at 723-873 K using O 2 as an oxidizer.…”

“…ozone, is needed to obtain good quality oxide thin films. [21] On the other hand, cyclopentadienyltype compounds yield considerably higher deposition rates and water can be used as the oxygen source. However, organometallic compounds are air-sensitive and therefore more difficult to synthesize and handle.…”

High Growth Rate of Erbium Oxide Thin Films in Atomic Layer Deposition from (CpMe)3Er and Water Precursors

“…[25,26] In addition, we have previously reported the ALD of erbium oxide using Er(thd) 3 (thd = 2,2,6,6-tetra-methyl-3,5-heptane-dione) and ozone as precursors. [27,28] b-Diketonate-type thd-complexes are volatile, and have frequently been utilized as precursors in ALD, [29] for example in the case of Sc 2 O 3 , [30] Y 2 O 3 , [31,32] La 2 O 3 , [33] CeO 2 , [34,35] as well as other Ln 2 O 3 films (Ln = Nd, Sm, Eu, Gd, Dy, Ho, Tm). [4,28,36] b-Diketonates do not readily react with water, but require the use of a stronger oxidizer, such as ozone, to produce oxide thin films with low carbon and hydrogen content.…”

“…Volatile and reactive cyclopentadienyl (Cp, -C 5 H 5 ) complexes are known to react with water, and furthermore the growth rates obtained in Cp-based processes have been markedly high. [38] Cyclopentadienyl complexes have previously been used by us in the ALD of some rare earth oxides, namely Sc 2 O 3 [30] and Y 2 O 3 . [39] Additionally, Lu 2 O 3 thin films have been grown by ALD using a dimeric Lu precursor containing silylated Cp groups.…”