Andrian P. Milanov

Synthesis, characterization, and thermal properties of homoleptic rare-earth guanidinates: promising precursors for MOCVD and ALD of rare-earth oxide thin films.

Eight novel homoleptic tris-guanidinato complexes M[(N(i)Pr)(2)CNR(2)](3) [M = Y (a), Gd (b), Dy (c) and R = Me (1), Et (2), (i)Pr (3)] have been synthesized and characterized by NMR, CHN-analysis, mass spectrometry and infrared spectroscopy. Single crystal structure analysis revealed that all the compounds are monomers with the rare-earth metal center coordinated to six nitrogen atoms of the three chelating guanidinato ligands in a distorted trigonal prism geometry. With the use of TGA/DTA and isothermal TGA analysis, the thermal characteristics of all the complexes were studied in detail to evaluate their suitability as precursors for thin film deposition by MOCVD and ALD. The (i)Pr-Me(2)N-guanidinates of Y, Gd and Dy (1a-c) showed excellent thermal characteristics in terms of thermal stability and volatility. Additionally, the thermal stability of the (i)Pr-Me(2)N-guanidinates of Y and Dy (1a, c) in solution was investigated by carrying out NMR decomposition experiments and both the compounds were found to be remarkably stable. All these studies indicate that (i)Pr-Me(2)N-guanidinates of Y, Gd and Dy (1a-c) have the prerequisites for MOCVD and ALD applications which were confirmed by the successful deposition of Gd(2)O(3) and Dy(2)O(3) thin films on Si(100) substrates. The MOCVD grown films of Gd(2)O(3) and Dy(2)O(3) were highly oriented in the cubic phase, while the ALD grown films were amorphous.

Homoleptic Gadolinium Guanidinate: A Single Source Precursor for Metal−Organic Chemical Vapor Deposition of Gadolinium Nitride Thin Films

Deposition of a rare earth nitride thin film using a chemical gas phase deposition technique is reported for the first time. The gadolinium tris-guanidinate complex [Gd{((i)PrN)(2)CNMe(2)}(3)] is found to be an effective single source precursor for the MOCVD growth of gadolinium nitride (GdN) thin films.

Growth of Crystalline Gd2O3 Thin Films with a High-Quality Interface on Si(100) by Low-Temperature H2O-Assisted Atomic Layer Deposition

This work documents the first example of deposition of high-quality Gd(2)O(3) thin films in a surface-controlled, self-limiting manner by a water-based atomic layer deposition (ALD) process using the engineered homoleptic gadolinium guanidinate precursor [Gd(DPDMG)(3)]. The potential of this class of compound is demonstrated in terms of a true ALD process, exhibiting pronounced growth rates, a high-quality interface between the film and the substrate without the need for any additional surface treatment prior to the film deposition, and most importantly, encouraging electrical properties.

Hafnium oxide thin film grown by ALD: An XPS study

Hafnium(IV) oxide thin films were synthesized by atomic layer deposition (ALD) on Si(100) substrates, using an innovative guanidinate-stabilized hafnium amide precursor, [Hf(NEtMe)2(EtMeNC(NiPr)2)2]. In the present work, our attention is focused on a detailed XPS characterization of a representative HfO2 coating grown at 350 °C. Beside the wide scan spectrum, detailed spectra for the O 1s, Hf 4f, Hf 4d and C 1s regions and related data are presented and discussed. The obtained results point out to the formation of HfO2 coatings characterized by the presence of -OH groups, whose main origin is attributed to the use of water as oxidizing agent during the preparation process.

Thin Films of HfO2 for High-k Gate Oxide Applications from Engineered Alkoxide- and Amide-Based MOCVD Precursors

HfO 2 thin films with thickness between 2 and 20 nm were grown by liquid injection metallorganic chemical vapor deposition, LI-MOCVD, on SiO x /Si(100) substrates. Different mononuclear precursors ([Hf(OPr i ) 2 (tbaoac) 2 ], [Hf(NEt 2 ) 2 (guanid) 2 ], and [Hf(OBu t ) 2 (dmae) 2 ] were tested in combination with different solvents. Growth rate, surface morphology, crystal structure, and crystal density of the as-deposited films were analyzed as a function of deposition temperature. The influence of postdeposition annealing on the densification and crystallization was studied. Correlation of the structural properties with the electrical properties of metal insulator semiconductor capacitors with Pt top electrodes is discussed. Fully silicided metal gate stacks are additionally discussed for selected samples.

Mixed amide–malonate compound of hafnium as a novel monomeric precursor for MOCVD of HfO2 thin films

The concept of introducing malonates as chelating ligands in combination with metal amides has yielded a new class of compounds which enable growth of HfO2 thin films at low deposition temperatures by liquid injection metalorganic chemical vapour deposition.

Nanostructured Dy2O3 films: An XPS Investigation

The present investigation is devoted to the X-ray photoelectron spectroscopy (XPS) analysis of the main core levels (C 1s, O 1s, Dy 4d, Dy 3d) of a representative dysprosium(III) oxide thin film. The specimen was grown on Si(100) at 500 °C by metal organic chemical vapor deposition (MOCVD) starting from Dy((iPrN)2CNMe2)3 in an N2/O2 atmosphere. The above route yielded uniform and homogeneous nanostructured Dy2O3 films characterized by a remarkable reactivity towards atmospheric CO2 and H2O, resulting in the surface co-presence of dysprosium carbonates/bicarbonates and hydroxides. The most relevant spectral features are presented and discussed.

Monomeric malonate precursors for the MOCVD of HfO2 and ZrO2 thin films

New Hf and Zr malonate complexes have been synthesized by the reaction of metal amides with different malonate ligands (L = dimethyl malonate (Hdmml), diethyl malonate (Hdeml), di-tert-butyl malonate (Hdbml) and bis(trimethylsilyl) malonate (Hbsml)). Homoleptic eight-coordinated monomeric compounds of the type ML4 were obtained for Hf with all the malonate ligands employed. In contrast, for Zr only Hdmml and Hdeml yielded the eight-coordinated monomeric compounds of the type ML4, while using the bulky Hdbml and Hbsml ligands resulted into mixed alkoxo-malonato six-coordinated compounds of the type [ML2(OR)2]. Single crystal X-ray diffraction studies of all the compounds are presented and discussed, and they are found to be monomeric. The complexes are solids and in solution, they retain their monomeric nature as evidenced by NMR measurements. Compared to the classical beta-diketonate complexes, [M(acac)4] and [M(thd)4] (M = Hf, Zr; acac: acetylacetonate; thd: tetramethylheptadione), the new malonate compounds are more volatile, decompose at lower temperatures and have lower melting points. In particular, the homoleptic diethyl malonate complexes of Hf and Zr melt at temperatures as low as 62 degrees C. In addition, the compounds are very stable in air and can be sublimed quantitatively. The promising thermal properties makes these compounds interesting for metal-organic chemical vapor deposition (MOCVD). This was demonstrated by depositing HfO2 and ZrO2 thin films successfully with two representative Hf and Zr complexes.

Tantalum complexes with all nitrogen coordination sphere: mixed amido-, imido-, guanidinato complexes of tantalum and their thermal behaviour

Novel mixed amido-/imido-/guanidinato-complexes of tantalum are reported. The complexes were synthesised by insertion reactions of carbodiimides of the type C(NR)2(R =iso-propyl (i-Pr)) into the M-N bonds of tantalum mixed amido/imido complexes. Three representative complexes were synthesised and fully characterised by 1H-NMR, 13C-NMR, CHN-analysis and mass spectroscopy. The crystal structure of the complex [Ta(NMe2){(i-Pr-N)2C(NMe2)}2(N-t-Bu)](1)(Me = methyl, t-Bu =tert-butyl) is presented and discussed. The complexes are solids that can be quantitatively sublimed at moderate temperatures (120-130 degrees C) without any sign of decomposition. The thermal properties of the new compounds were studied (TGA) and preliminary MOCVD-experiments were performed. TaN films were deposited and characterised by XRD and XPS.

Downscaling of defect-passivated Gd2O3 thin films on p-Si(0?0?1) wafers grown by H2O-assisted atomic layer deposition

Crystalline thin films of Gd2O3 of varying thicknesses were grown on 2 inch p-Si(1 0 0) wafers by H2O-assisted atomic layer deposition (ALD) using a homoleptic gadolinium tris-guanidinate precursor [Gd(iPr-Me2N-Guan)3]. The Gd2O3 layers grown at 225 °C were polycrystalline with columnar growth morphology. The as-grown films were electrically characterized as a metal oxide semiconductor (MOS) capacitor and exhibited instability in the flat-band voltage. Upon subjection to post-deposition defect-passivation treatment, they exhibited promising electrical characteristics. More importantly, the vertical downscaling of Gd2O3 thin films through the H2O-assisted ALD process could be realized through the capacitance equivalent thickness versus physical thickness studies.