Yttrium Oxide Films Research Articles

Oxygen plasma-assisted magnetron sputtering deposition of non-stoichiometric Y2O3 films: Influence of oxygen vacancies on etching resistance

Yttrium oxide (Y2O3) films are widely used to protect equipment in plasma etching, a crucial technique in semiconductor processing, due to their exceptional resistance to plasma etching. Since oxygen vacancy affects the performance of Y2O3 and may impact physical etching resistance, the internal relationship necessitates further investigation. In this article, Y2O3 films with varying oxygen vacancy concentrations are prepared by reactive magnetron sputtering with the assistance of oxygen plasma. The formation and development of oxygen vacancies in cubic Y2O3 films and their impact on the physical etching resistance were investigated. The experiment results indicate that the accumulation of oxygen vacancies causes non-stoichiometry and the etching rate is significantly reduced. Combined with density-functional theory, it is revealed that oxygen vacancy distorts the lattice, which increases covalent Y–O bonding and the formation energy of atoms. Moreover, the vacancy line defects resulting from diffusion and aggregation of oxygen vacancies exert a similar influence on the adjacent yttrium and oxygen layers. The enhancement of physical etching resistance is attributed to the strengthened internal Y–O bonds led by increasing oxygen vacancy concentration in the cubic Y2O3 films without inducing phase transition. The discovery enriches the understanding of how plasma interacts with Y2O3, and the etching mechanism.

Formation of yttrium oxalate phase filled by carbon clusters on the surface of yttrium oxide films

In the current paper, we report the results of surface modification of cubic Y2O3 films employing carbon-ion implantation. The characterization results demonstrate the formation of a stable yttrium oxalate-based structure with cavities filled with carbon clusters. Theoretical simulations demonstrate that the incorporation of eighteen-atom carbon clusters into the cavities of Y2(C2O4)3 does not lead to valuable changes in the crystal structure of yttrium oxalate. X-ray diffraction and optical measurements demonstrate that the subsurface bulk area of cubic yttrium oxide remains unperturbed. The oxalate “skin” thickness with embedded carbon clusters is estimated to be approximately 10 nm. The prospective employing the method to manage optical properties and increase the biocompatibility of yttria and lanthanide oxides are discussed.

Anisotropic Surface Formation Based on Brush-Coated Nickel-Doped Yttrium Oxide Film for Enhanced Electro-Optical Characteristics in Liquid Crystal Systems

This paper introduces anisotropic nickel yttrium oxide (NYO) film formed by the brush coating technique. X-ray photoelectron spectroscopy confirmed well-formed NYO film after the curing process, and the morphology of the surface was investigated using atomic force microscopy. The shear stress driven from brush hair movements caused the nano/micro-grooved anisotropic surface structure of NYO. This anisotropic surface induced uniform liquid crystal (LC) alignment on the surface, which was confirmed by pre-tilt angle analysis and polarized optical microscopy. The contact angle measurements revealed an increase in hydrophilicity at higher temperature curing, which contributed to homogenous LC alignment. The NYO film achieved good optical transmittance and thermal stability as an LC alignment layer. In addition, the film demonstrated good electro-optical properties, stable switching, and significantly enhanced operating voltage performance in a twisted-nematic LC system. Therefore, we expect that this brush coating method can be applied to various inorganic materials to achieve an advanced LC alignment layer.

Resistive switching characteristics and mechanism of lanthanum yttrium oxide (LaYO3) films deposited by RF sputtering for RRAM applications

LaYO3 thin films are deposited by using RF sputtering and resistive switching properties of LaYO3-based RRAM devices are investigated. Specifically, the effects of sputtering time, top electrode materials, deposition conditions, annealing temperature, and annealing processes on resistive switching characteristics of the devices are studied. The results indicate that conductive filaments are mainly dominated by oxygen vacancies whose concentration can be manipulated by the deposition atmosphere and annealing process. The formation of conductive filaments can be enhanced by the diffusion of In ions from an indium tin oxide substrate into LaYO3 layer during the annealing process. The Schottky barrier height under different top electrodes and deposition atmospheres also have an impact on the formation of filaments. In addition, post-metal anneal can help to form an AlOx interface layer, which plays significant roles in improving resistive switching performance of the LaYO3-based RRAMs. The devices annealed at 400 ºC possess resistive switching characteristics for over 1200 cycles and a Ron/Roff ratio of 103, showing promise for non-volatile memory applications.

Exciton Luminescence and Optical Properties of Nanocrystalline Cubic Y2O3 Films Prepared by Reactive Magnetron Sputtering.

This paper presents a comprehensive study of the energy structure, optical characteristics, and spectral-kinetic parameters of elementary excitations in a high-purity nanocrystalline cubic Y2O3 film synthesized by reactive magnetron sputtering. The optical transparency gaps for direct and indirect interband transitions were determined and discussed. The dispersion of the refractive index was established based on the analysis of interference effects. It was found that the refractive index of the Y2O3 film synthesized in this study is higher in order of magnitude than that of the films obtained with the help of other technologies. The intrinsic emission of Y2O3 film has been discussed and associated with the triplet–singlet radiative relaxation of self-trapped and bound excitons. We also studied the temperature behavior of the exciton luminescence of Y2O3 for the first time and determined thermal activation barriers. The optical energy and kinetic parameters of cubic Y2O3 films were analyzed in comparison with those of the monoclinic films of yttrium oxide. The main difference between the optical properties of cubic and monoclinic Y2O3 films was established, which allowed for a supposition of their application prospects.

The Influence of CeO2 Concentration on Some Physical Properties of Y2O3 Thin Films

Thin films of pure yttrium oxide (Y2O3) and doped with cerium oxide (CeO2) were prepared by the chemical spray pyrolysis(CSP)method. The structural, optical and electrical properties of the prepared films were investigated. The analysis of X-ray diffraction (XRD) thin films revealed that the undoped and doped Y2O3 were amorphous with a broad hump around 27o and narrow humps around 48o and 62o for all samples. Except for the Y2O3:6wt.%CeO2 thin film, all had signal preferential orientation along the (100) plane at 2θ=12.71o which belongs to CeO2, Field emission scanning electron microscopic (FE-SEM) images confirmed the formation of the nanosized particles which resembles circles and others revealed rods and balls shape. UV-Vis spectra study showed peak absorption at a wavelength of 305 nm, with blue shift due to quantum confinement, and this also happened for the doped films, with direct energy band gaps. The photoluminescence spectra (PL) of undoped Y2O3 and doped thin films showed an emission peak at 365 nm at the same wavelength of all the prepared samples with a slight difference. All prepared films show three activation energies except Y2O3:6wt.%CeO2 film has two activation energies. From I-V characteristic curves, the prepared films have Schottky behavior except Y2O3:6wt.%CeO2 film, which displayed ohmic behavior. Y2O3:6wt.%CeO2 fabricated device revealed good photosensitivity for VIS and IR wavelength.

Passivation effect on the surface characteristics and corrosion properties of yttrium oxide films undergoing SF6 plasma treatment

This study investigates the structures, compositions and fluorocarbon-plasma etching behaviors of yttrium oxyfluoride (YOF) passivation films fabricated on sputter-deposited yttrium oxide (Y2O3) by high-density SF6 plasma irradiation. High-resolution transmission electron microscopy and nano-beam electron diffraction confirmed a YOF passivation film containing multiple phases of (104) and (006) crystal planes was formed on the fluorinated Y2O3 surface. X-ray photoelectron spectroscopy revealed few changes in the chemical compositions and surface roughness of the YOF passivation film after fluorocarbon plasma etching, confirming the chemical stability of the SF6 plasma-treated Y2O3 sample. The etching depth was ∼20% lower on the SF6 plasma-treated Y2O3 film than on the commercial Y2O3 coating. These results showed that the SF6 plasma-treated Y2O3 films have an excellent erosion resistance properties compared to the commercial Y2O3 coatings.

A remarkable effect of substrate temperature on novel Al/Y2O3/n-Si heterojunction diodes performance fabricated by facile jet nebulizer spray pyrolysis for optoelectronic applications

Herein, we present the development and characterization of Yttrium oxide (Y2O3) films and Al/Y2O3/n-Si heterojunction diodes at various substrate temperatures using a low-cost facile jet nebulizer spray pyrolysis (JNSP) technique. The X-ray powder diffraction (XRD) pattern proved polycrystalline films of Y2O3 with a cubic structure. Field emission scanning electron microscope (FESEM) images reveal very fine nanograins formation in Y2O3 films at all temperatures. Scanning probe microscopy (SPM) analysis shows very low roughness of all films. The detailed compositional/homogeneity analysis was done via energy dispersive X-ray (EDX)/e-mapping analysis. All the films exhibited a sharp absorption edge at ∼ 280 nm, and the estimated energy gap values were noticed between 4.5 to 4.9 eV. Moreover, the observed photoluminescence (PL) spectrum indicated number of emission peaks in the grown films. From the current – voltage (I-V) characteristic, the calculated ideality factor (n) value was noticed to be drastically reduced from 7.66 to 2.87 on increasing the substrate temperature. Further, the diode ideality factor, series resistance (Rs) and barrier height (ФB) were obtained from Cheung's method. The results revealed that the developed Al/Y2O3/n-Si heterojunction diode is a promising contender for optoelectronic devices.

Thermal Atomic Layer Deposition of Yttrium Oxide Films and Their Properties in Anticorrosion and Water Repellent Coating Applications

The thermal atomic layer deposition (ThALD) of yttrium oxide (Y2O3) was developed using the newly designed, liquid precursor, Y(EtCp)2(iPr2-amd), as the yttrium source in combination with different oxygen sources, such as ozone, water and even molecular oxygen. Saturation was observed for the growth of the Y2O3 films within an ALD window of 300 to 450 °C and a growth per cycle (GPC) up to 1.1 Å. The resulting Y2O3 films possess a smooth and crystalline structure, while avoiding any carbon and nitrogen contamination, as observed by X-ray photoelectron spectroscopy (XPS). The films showed strong resistance to fluorine-containing plasma, outperforming other resistant materials, such as silicon oxide, silicon nitride and alumina. Interestingly, the hydrophilic character exhibited by the film could be switched to hydrophobic after exposure to air, with water contact angles exceeding 90°. After annealing under N2 flow at 600 °C for 4 min, the hydrophobicity was lost, but proved recoverable after prolonged air exposure or intentional hydrocarbon exposure. The origin of these changes in hydrophobicity was examined.

The tunable dielectric properties of sputtered yttrium oxide films

Yttrium oxide film is an important dielectric material, which has been widely used in the scientific and engineering fields. The microstructures of yttrium oxide films can be modified effectively by adjusting the substrate temperature and bias voltage, which also have effects on dielectric properties of yttrium oxide films. In this work, the dielectric properties of yttrium oxide films grown on Pt film, which exhibit the distinct microstructures with cubic-phase and monoclinic-phase domination manipulated by different substrate temperatures and bias voltages, have been investigated systematically. High substrate temperature as well as large bias voltage can decrease the loss tangent and enhance the dielectric constants up to 56 and 40, respectively. Furthermore, the driven force of temperature is more favorable than that of bias voltage for enhanced dielectric constant due to fewer defects.

Plasma Etching Behavior of SF6 Plasma Pre-Treatment Sputter-Deposited Yttrium Oxide Films

Yttrium oxyfluoride (YOF) protective materials were fabricated on sputter-deposited yttrium oxide (Y2O3) by high-density (sulfur fluoride) SF6 plasma irradiation. The structures, compositions, and fluorocarbon-plasma etching behaviors of these films were systematically characterized by various techniques. After exposure to SF6 plasma, the Y2O3 film surface was fluorinated significantly to form a YOF film with an approximate average thickness of 30 nm. X-ray photoelectron spectroscopy revealed few changes in the elemental and chemical compositions of the surface layer after fluorination, confirming the chemical stability of the YOF/Y2O3 sample. Transmission electron microscopy confirmed a complete lattice pattern on the YOF/Y2O3 structure after fluorocarbon plasma exposure. These results indicate that the SF6 plasma-treated Y2O3 film is more erosion resistant than the commercial Y2O3 coating, and thus accumulates fewer contamination particles.

Thermal and Plasma-Enhanced Atomic Layer Deposition of Yttrium Oxide Films and the Properties of Water Wettability.

The atomic layer deposition (ALD) of yttrium oxide (Y2O3) is investigated using the liquid precursor Y(EtCp)2(iPr-amd) as the yttrium source with thermal (H2O) and plasma-enhanced (H2O plasma and O2 plasma) processes, respectively. Saturation is confirmed for the growth of the Y2O3 films with each investigated reactant with a similar ALD window from 150 to 300 °C, albeit with a different growth rate. All of the as-deposited Y2O3 films are pure and smooth and have a polycrystalline cubic structure. The as-deposited Y2O3 films are hydrophobic with water contact angles >90°. The water contact angle gradually increased and the surface free energy gradually decreased as the film thickness increased, reaching a saturated value at a Y2O3 film thickness of ∼20 nm. The hydrophobicity was retained during post-ALD annealed at 500 °C in static air for 2 h. Exposure to polar and nonpolar solvents influences the Y2O3 water contact angle. The reported ALD process for Y2O3 films may find potential applications in the field of hydrophobic coatings.

Thermal expansion studies of electron beam evaporated yttria films on Inconel-718 substrates

In this paper, phase pure cubic yttrium oxide (Y2O3) films deposited by electron beam physical vapor deposition technique on Inconel-718 substrate at different substrate temperatures (773–973 K) are investigated. The structure and phase evolution in the films of Y2O3 as a function of substrate temperature have been evaluated by X-ray diffraction. Atomic force microscopy and scanning electron microscopy were used to examine the surface roughness and morphology of the as-deposited Y2O3 films. The adhesion behavior of the Y2O3 film with Inconel-718 substrate was investigated using scratch indentation testing. The thermal expansion coefficient (TEC) of Inconel-718 substrate and Y2O3 film coated on Inconel-718 substrate were determined by high temperature X-ray diffraction (HTXRD) measurement in the temperature range of 298–1273 K with temperature interval of 100 K. The linear TECs of Inconel-718 and Y2O3 film at 1273 K were found to be 1.22 × 10−5 K−1 and 7.02 × 10−6 K−1, respectively. Thermal stability of the Y2O3 coated Inconel-718 substrate tested at 1273 K in air over a period of 100 h is also discussed.

Yttrium oxide film for protecting quartz glass surface from etching by long-term exposure to chlorine trifluoride gas at room temperature

The anticorrosive property of yttrium oxide was evaluated using chlorine trifluoride gas. After the exposure to chlorine trifluoride gas at room temperature for the total time longer than 1000 min, the yttrium oxide film, formed on a quartz glass surface, did not show any etching behavior and surface morphology change, while the non-coated quartz glass showed a rough surface with the etching depth of nearly 0.1 mm. Because yttrium oxide had no chemical reaction with chlorine trifluoride gas at temperatures less than 300 °C, yttrium oxide film is expected to protect the quartz glass from etching by chlorine trifluoride gas at room temperature for a significantly long time.

Solution-processed ternary alloy aluminum yttrium oxide dielectric for high performance indium zinc oxide thin-film transistors

In this study, we evaluated the structural, chemical, and electrical properties of ternary alloy aluminum yttrium oxide (Al2-xYxO3) films prepared by employing a low-cost spin-cast technique. Al2-xYxO3 films annealed at 400 °C were found to possess smooth and excellent insulating characteristics compared to their binary Al2O3 or Y2O3 film counterparts. This superior performance of the Al2-xYxO3 films as a gate insulator can be explained based on structure stabilization from the cation alloying mixing effect. The amorphous indium zinc oxide (a-IZO) thin-film transistor (TFT) with the ternary alloy Al0.45Y1.55O3 film exhibited a high mobility of 52.9 cm2/V, a low subthreshold gate swing of 0.19 V/decade, a threshold voltage of −0.51 V, a high ION/OFF ratio of 4 × 106, and good hysteresis-free stability, suggesting that the solution-based Al0.45Y1.55O3 dielectric film is an attractive candidate as a gate dielectric for high-performance and low-cost a-IZO TFTs.

Plasma Exposure Behavior of Yttrium Oxide Film Formed by Aerosol Deposition Method

Aerosol deposition (AD) method is technique for forming high density ceramic films on substrate material surface at room temperature. The yttrium oxide films formed by the AD method (AD-Y2O3 films) have been developed as plasma resistance coating used for the plasma etching equipment. In recent years, plasma eroded particles from chamber components of the etching devices are regarded as a serious issue that they reduce the semiconductor device yield rate. AD-Y2O3 films which have excellent plasma resistance can reduce the eroded particles in the plasma etching equipment and greatly have contributed to manufacturing high integrated semiconductor devices. In this paper, the plasma erosion behavior of AD-Y2O3 films were investigated compared with sintered Al2O3, sintered Y2O3 and thermal splayed Y2O3 in order to clarify the reason why AD Y2O3 films were superior as plasma resistance material. The plasma etching rates of AD-Y2O3 films were not significantly different from other samples. It was assumed that the etching rates were dependent on the chemical stability to fluorine plasma of material. On the other hand, the surface roughness difference before and after plasma exposure of AD-Y2O3 films were much smaller than other samples. It was assumed that the surface roughness difference is dependent on the crystalline size of material. The structure of AD-Y2O3 films, which had high density and nano-crystalline structure, were eroded homogeneously and smoothly. It suggests AD-Y2O3 films do not generate large eroded particles and are superior to reduce the eroded particles in the etching devices.

Effects of erbium content on the morphological and photoluminescent properties of sol-gel prepared yttrium oxide film

This work presents the effects of erbium content on the morphological, structural, and photoluminescent properties of erbium-doped yttrium oxide film prepared by water-added-free gelation and spin coating. Crack-free annealed films with uniform thickness and good adhesion are obtained by spin-coating the precursor solutions synthesized by the water-added-free reaction at a low gelation rate. The proposed process has the features of no crack formation after high-temperature annealing, high film thickness homogeneity, and compatibility with standard semiconductor processes. The morphological and structural properties of the prepared films are investigated systematically by optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). The OM and SEM measurements show that the variation in film color and film morphology is related to the erbium content. A decrease in the surface roughness with increasing erbium content is exhibited by the AFM measurement. The XRD results indicate that the preferential crystalline plane gradually varies from (400) to (222) as the erbium content increases. The peak PL wavelengths in the visible (VIS) and near-infrared (NIR) ranges appear at the wavelengths of 561.2nm and 1536.6nm when the films are excited by pump lasers at the wavelengths of 532nm and 970nm. Yttrium oxide film with an erbium content of 5mol% has the maximal PL intensity for both VIS and NIR ranges. This optimal erbium content results from a compromise between the increase in the number of active erbium ions and the non-radiative recombination due to the erbium ion-ion interaction.

Y(dbm)3(H2O)]: Synthesis, thermal behavior and spin-coating precursor for Y2O3 layer formation

The synthesis, structure and thermal behavior of [Y(dbm)3(H2O)] (3) (dbm = 1,3-diphenyl-1,3-propandionate) and its use as a spin-coating precursor for Y2O3 deposition is reported. Complex 3 was prepared by the reaction of [Y(NO3)3·6H2O] (1) with 3 equiv of Hdbm (2) in presence of NaOH. The molecular structure of 3 in the solid-state was determined by single X-ray crystal diffraction. Both C1 symmetric crystallographically independent species of 3 possess a YO7 coordination setup with minor deviation from an ideal capped octahedron coordination geometry (Λ enantiomer). Complex 3 forms a 1D chain, due to intermolecular hydrogen bonds between the coordinated H2O molecule and the O atom of the dbm ligand, respectively. The thermal decomposition behavior of 3 was investigated by thermogravimetric studies in the temperature range of 40–800 °C and 40–1300 °C under an oxygen and argon atmosphere, respectively. Powder X-ray diffraction (PXRD) measurements of the residues confirmed the formation of Y2O3. Complex 3 was applied as a spin-coating precursor for yttrium oxide film formation on either Si wafers with a continuous 100 nm thick SiO2 film, or with a native oxide layer. The as-deposited Y2O3 layers are smooth, conformal, dense and transparent and are of a thickness of 27 and 30 nm, respectively.

Densification of metal oxide films synthesized from metal complexes by flame spraying

In this study, we synthesized dense metal oxide films from a metal-ethylenediaminetetraacetic acid complex using a flame sprayer. Erbium oxide (Er2O3), Yttrium oxide (Y2O3) films were synthesized on stainless steel substrates using N2, air (O2+N2), or O2 as the carrier gas and a H2-O2 mixture as the combustion gas. When O2 was used as the carrier gas, 9.9–20.5μm-thick oxide layers were deposited on the SUS substrate. The cross-sectional porosities of the films were 3–5%. In contrast, oxide layers with 8.1–15.8μm thickness were synthesized on stainless steel substrates when N2 and air were used as the carrier gases. The cross-sectional porosities of these films were 16.1–23.4%. These results indicated that the carrier gas plays an important role in determining the thickness and porosity of the resulting film.

Heat-shock properties in yttrium-oxide films synthesized from metal–ethylenediamine tetraacetic acid complex through flame-spray apparatus

Recently, a new deposition technique using a metal–ethylenediamine tetraacetic acid (EDTA) complex has been developed. In this study, the heat-shock properties of metal-oxide films synthesized from a metal–EDTA complex were investigated. Y2O3 films were synthesized on stainless-steel (SUS) substrate from EDTA∙Y∙H through the combustion of H2–O2 gas. A cyclic heat-shock test was conducted on the fabricated Y2O3 films through exposure to the H2-O2 flame. The existence of Y2O3 crystals was confirmed. Surface cracks or damages were not observed in the samples after the cyclic thermal test. Although the number of cross-sectional cracks, crack lengths, and cracks per unit area was increased by the heat shock, delaminations were not observed in the Y2O3 films. The results show that the prepared Y2O3 films have high thermal-shock resistance and are suitable for use as thermal barrier coatings.