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The atomic layer deposition (ALD) of scandium oxide (Sc2O3) thin films is investigated using Sc(MeCp)2(Me2pz) (1, MeCp = methylcyclopentadienyl, Me2pz = 3,5-dimethylpyrazolate) and ozone on hydroxyl-terminated oxidized Si(111) substrates at 225 and 275 °C. In situ Fourier transform infrared spectroscopy reveals that 1 not only reacts with surface hydroxyl groups at 275 °C, as expected but also with the SiO2 layer, as evidenced by losses in the SiO2 longitudinal optical and transverse optical phonon modes, resulting in the partial transformation of near-surface SiO2 to an ScSixOy interface layer. Ozone then combusts the MeCp groups of the O–Sc(MeCp)2 chemisorbed species, yielding surface carbonates, and oxidizes some of the underlying silicon, evidenced by gains in the SiO2 phonon modes. The Me2pz group from the next pulse of 1 reacts with these surface carbonates, leading to Sc–O–Sc bond formation (Sc2O3 deposition) and the restoration of an O–Sc(MeCp)2 surface. The reaction of the SiO2 substrate with 1 and the oxidation of silicon by ozone are temperature-dependent processes that occur during the initial cycles of film growth and directly impact the changes in the intensities of the SiO2 phonon modes. For instance, the intensity of the net gains in the phonon modes following ozone exposure is greater at 275 °C than at 225 °C. As the ALD cycle is repeated, the formation of an ScSixOy interface layer and deposition of an Sc2O3 film result in the gradual attenuation of the reaction of the SiO2 substrate with 1 and the oxidation of the underlying silicon by ozone. In addition to the ALD process, characterized by ligand exchange and self-limiting reactions, there are gas-phase reactions between 1 and residual water vapor near the substrate surface that lead to deposition of additional Sc2O3 and surface carbonates, the extent of which are also dependent on the temperature of the substrate. After 20 cycles of 1/ozone, the film thicknesses derived from ex situ X-ray photoelectron spectroscopy measurements are 2.18 nm (225 °C) and 3.88 nm (275 °C). This work constitutes the first mechanistic study of an Sc2O3 ALD process using ozone as the oxidant and emphasizes the significance of atypical reactions between the substrate and the reactants that influence the growth rate and near-surface stoichiometry during the initial cycles of film deposition.The atomic layer deposition (ALD) of scandium oxide (Sc2O3) thin films is investigated using Sc(MeCp)2(Me2pz) (1, MeCp = methylcyclopentadienyl, Me2pz = 3,5-dimethylpyrazolate) and ozone on hydroxyl-terminated oxidized Si(111) substrates at 225 and 275 °C. In situ Fourier transform infrared spectroscopy reveals that 1 not only reacts with surface hydroxyl groups at 275 °C, as expected but also with the SiO2 layer, as evidenced by losses in the SiO2 longitudinal optical and transverse optical phonon modes, resulting in the partial transformation of near-surface SiO2 to an ScSixOy interface layer. Ozone then combusts the MeCp groups of the O–Sc(MeCp)2 chemisorbed species, yielding surface carbonates, and oxidizes some of the underlying silicon, evidenced by gains in the SiO2 phonon modes. The Me2pz group from the next pulse of 1 reacts with these surface carbonates, leading to Sc–O–Sc bond formation (Sc2O3 deposition) and the restoration of an O–Sc(MeCp)2 surface. The reaction of the SiO2 substrate with 1 a...

Alternatives to tetrakis(dialkylamido)zirconium and hafnium for use as precursors to zirconium and hafnium oxide films are examined. Tetrakis(trimethylhydrazido)zirconium and hafnium, Zr(NMeNMe 2 ) 4 and Hf(NMeNMe 2 ) 4 , and Hf[ t BUNCH 2 CH 2 N- t Bu] 2 are used with oxygen as precursors to zirconium and hafnium oxide films in a low-pressure CVD process at substrate temperatures

The mixed ligand complexes [{Gd(OCMe2-i-Pr)2Cp}2], [{Sm(OCMe2-i-Pr)2Cp}2], and [Sm2(OCMe2-i-Pr)3Cp3] were synthesized by reacting [LnCp3] with HOCMe2-i-Pr. X-ray crystallographic studies show that the three complexes each have two bridging alkoxide ligands linking two metal atoms. The coordination geometries at the metals are distorted tetrahedral.

Reaction of CeCl3 with an excess of LiTMP (TMP-H = 2,2,6,6-tetramethylpiperidine) gave [Ce(μ-OCH CH2)(TMP)2]2. The alkoxide ligand originated from THF, which was used as the solvent in the reaction. CeCl3 reacted with 3 equiv. of LiTMP in THF to produce, after crystallization, a 3:2 crystalline mixture of Ce(TMP)3 and [Ce(μ-OCH CH2)(TMP)2]2. Ce(TMP)3 could not be isolated cleanly or separated from the mixture except by handpicking the crystals under a microscope. The homoleptic amide complex Ce[N-t-Bu(SiMe3)]3 was obtained by reacting CeCl3(THF)2 with 3 equivalents of LiN-t-Bu(SiMe3). In the solid state, [Ce(μ-OCH CH2)(TMP)2]2 is a dimer with a Ce(μ-OR)2Ce four-member ring, while Ce(TMP)3 and Ce[N-t-Bu(SiMe3)]3 are trigonal planar monomers. There is structural evidence to suggest the presence of a Ce–vinyl group interaction in [Ce(μ-OCH CH2)(TMP)2]2.

The cerium(IV) alkoxide complex Ce(OCMe2-i-Pr)4, a volatile, nonfluorinated source of cerium, was used as a chemical vapor deposition precursor to cerium oxide films. A conventional thermal chemical vapor deposition process deposited cerium(IV) oxide films from Ce(OCMe2-i-Pr)4 on silicon, glass, quartz, lanthanum aluminum oxide (001), and roll-textured nickel (001) substrates at low substrate temperatures (

Chlorotris(trimethylhydrazido)titanium, TiCl(NMeNMe2)3, was synthesized by reacting TiCl2(NMeNMe2)2 with 1 equiv. of LiNMeNMe2. Tetrakis(trimethylhydrazido)zirconium and hafnium, M(NMeNMe2)4, were prepared from MCl4 and 4 equiv. of LiNMeNMe2 but Ti(NMeNMe2)4 could not be prepared cleanly from TiCl4. Instead, it was synthesized from TiCl(NMeNMe2)3 and LiNMeNMe2. X-ray crystallographic studies show that TiCl(NMeNMe2)3 and Ti(NMeNMe2)4 have three bidendate hydrazide ligands and Zr(NMeNMe2)4 has four bidendate ligands.

The bulky hydrazine t-BuN(H)NMe 2 was synthesized via hydrazone and t-BuN(H)N(H)Me intermediates as the major component in a 90:5:5 mixture consisting of t-BuN(H)NMe 2 , t-BuN(Me)N(H)Me, and t-BuN(Me)NMe 2 . Reacting the mixture with n-BuLi followed by distillation and fractional crystallization led to the isolation of the ligand precursor LiN(t-Bu)NMe 2 . Lithium hydrazides, LiN(R)NMe 2 , were reacted with metal chlorides to afford the hydrazide complexes M(N(Et)Nme 2 ) 4 (M = Zr or Hf), MCI(N(R)NMe 2 ) 3 (M = Zr, R = i-Pr or t-Bu; M = Hf, R = t-Bu), and TaCl 3 (N(i-Pr)NMe 2 ) 2 . The X-ray crystal structures of [LiN(i-Pr)NMe 2 ] 4 , [LiN(t-Bu)NMe 2 -THF]2, ZrCl(N(R)NMe 2 ) 3 (R = i-Pr or f-Bu), and TaCl 3 (N(i-Pr)NMe 2 ) 2 were determined. The structural analyses revealed that the hydrazide ligands in ZrCl(N(R)NMe 2 ) 3 (R = i-Pr or t-Bu) and TaCl 3 (N(I-Pr)Nme 2 ) 2 are η 2 coordinated.

Zirconium amide-iodide complexes were synthesized for possible use as chemical vapor deposition precursors to zirconium nitride films. The series of six complexes Zr(NR(2))(4-n)I(n)(R = Me or Et; n = 1-3) was prepared by reacting ZrI(4) and Zr(NR(2))(4) in hot toluene. X-ray crystallographic analyses were performed for Zr(NMe(2))(3)I, Zr(NEt(2))(2)I(2), and Zr(NEt(2))I(3). In the solid state, Zr(NMe(2))(3)I and Zr(NEt(2))(2)I(2) are the discrete dimers [Zr(NMe(2))(2)I(mu-NMe(2))](2) and [Zr(NEt(2))(2)I(mu-I)](2), and Zr(NEt(2))I(3) is the polymer of dimers ([Zr(NEt(2))I(2)(mu-I)](2))(n). In solution, Zr(NEt(2))(3)I is proposed to be monomeric on the basis of NMR data and a molecular weight determination. The complex Zr(NEt(2))(3)I is the most promising precursor candidate because of its physical properties.

A new precursor system for the deposition of tantalum nitride films has been developed. The tantalum(IV) complexes Ta(NEt2)2Cl2(p-Me2Npy)2 and Ta(NEt2)2(NCy2)2 were synthesized and their structures were determined by X-ray crystallography. Ta(NEt2)2Cl2(p-Me2Npy)2 has an octahedral structure with trans chloride and cis amido ligands, and Ta(NEt2)2(NCy2)2 has a distorted tetrahedral geometry. Tantalum nitride films were prepared from Ta(NEt2)2(NCy2)2 and ammonia at 340 °C using aerosol-assisted chemical vapor deposition. The films on glass had resistivities of 2.5 ± 0.1 × 105 μΩ cm. Rutherford backscattering spectrometry, forward recoil spectrometry, and X-ray photoelectron spectroscopy data suggest the films have a composition of approximately TaN1.5H0.3–0.5. The X-ray photoelectron spectroscopy data also indicate that the average tantalum oxidation state is +4 and that each hydrogen atom in the film is associated with two nitrogen atoms on average. The films were a barrier to diffusion between copper and silicon at 500 °C for one hour. The results of this study suggest that the oxidation state of the metal in the precursor controls the oxidation state of the metal in the film, and thereby the film stoichiometry and properties.