Atomic Layer Deposition Of Thin Films Research Articles

Room temperature plasma enhanced atomic layer deposition for TiO2 and WO3 films

This paper presents a study on plasma enhanced atomic layer deposition (ALD) of TiO2 and WO3 films on silicon substrates. At low temperatures, ALD processes, which are not feasible at high temperatures, could be possible. For example, temperatures at 180 °C and above allow no WO3 ALD process with WF6 as a precursor because etching processes hinder film growth. Further low temperature deposition techniques are needed to coat temperature sensitive materials. For the deposition, WF6 and TiCl4 are used as metal precursors and O2 and H2O as oxygen sources. The depositions were accomplished in the temperature range of 30 °C up to 180 °C for both metal oxides. Spectroscopic ellipsometry, x-ray reflection, and grazing incidence diffraction were used to investigate the deposited ALD thin films. Film growth, density, crystallinity, and roughness are discussed as functions of temperature after ensuring the ALD requirement of self-saturating adsorption. Growth rates and measured material properties are in good agreement with literature data.

(Invited) Atomic Layer Etching Using Thermal Reactions: Atomic Layer Deposition in Reverse

Atomic layer etching (ALE) is a thin film removal technique based on sequential, self-limiting surface reactions. ALE is the reverse of atomic layer deposition (ALD). ALD has developed rapidly over the last 10-15 years to meet many technological needs such as the miniaturization of semiconductor devices. In contrast, ALE is relatively new and is only starting to receive serious attention. Initial work in ALE has focused on plasma ALE using halide adsorption and energetic ion bombardment to obtain anisotropic etching. There is a need for thermal approaches to ALE based on spontaneous reactions that would produce isotropic etching. This talk will present a new thermal approach to ALE based on sequential, self-limiting thermal surface reactions. Examples will be presented for Al2O3 [1, 2], HfO2 [3] and AlF3 ALE. The ALE is achieved using sequential, self-limiting thermal reactions. For the metal oxides, the ALE process is based on fluorination and ligand-exchange reactions. Using HF and Sn(acac)2 as the reactants, Al2O3 and HfO2 ALE are examined using quartz crystal microbalance, x-ray reflectivity and Fourier transform infrared spectroscopy measurements. These studies show that controlled, atomic level removal of Al2O3 and HfO2 is possible at temperatures from 150-250°C [1-3]. The surface reaction mechanism involves the formation of a metal fluoride reaction intermediate from fluorination of the metal oxide by HF. The HF reactant also allows H2O to leave as a reaction product. The Sn(acac)2 reactant then accepts fluorine from the metal fluoride and donates acac to the substrate. The donated acac ligand can produce Al(acac)3 or Hf(acac)4 as volatile reaction products. AlF(acac)2 and HfF(acac)3 may also be volatile reactions products. Sequential exposures of HF and Sn(acac)2 produce Al2O3 ALE etching rates of 0.14 Å/cycle- 0.61 Å/cycle per cycle at temperatures from 150- 250°C [1, 2]. Sequential exposures of HF and Sn(acac)2 produce HfO2 ALE etching rates of 0.070 Å/cycle - 0.117 Å/cycle per cycle at temperatures from 150- 250°C [3]. This ALE reaction mechanism based on fluorination and ligand-exchange should be applicable to other materials such as metal nitrides, metal phosphides, metal arsenides and elemental metals. This ALE reaction mechanism is also general and works with other fluorine metal acceptors such as Al(CH3)3 and fluorination precursors such as XeF2. In addition, metal fluorides are candidates for ALE. Fourier transform infrared spectroscopy reveals that Al2O3 is converted to AlF3 during the HF exposure. Sn(acac)2 can then remove the AlF3 by the ligand-exchange process. If AlF3 is a reaction intermediate during Al2O3 ALE, then AlF3 ALE should also be possible using AlF3 substrates. We have demonstrated AlF3 ALE using AlF3 ALD thin films grown using Al(CH3)3 and HF. The AlF3 ALE was performed using Sn(acac)2 and HF as the ALE reactants. 1. Younghee Lee and Steven M. George, “Atomic Layer Etching of Al2O3 Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)2 and HF”, ACS Nano 9,2061 (2015). 2. Younghee Lee, Jaime W. DuMont and Steven M. George, “Mechanism of Thermal Al2O3 Atomic Layer Etching Using Sequential Reactions with Sn(acac)2 and HF” Chem. Mater. (In Press). 3. Younghee Lee, Jaime W. DuMont and Steven M. George, “Atomic Layer Etching of HfO2 Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)2 and HF”, ECS J. Solid State Sci. Technol. 4, N5013 (2015).

(Invited) Chemical Stability and Electronic Behavior of Atomic Layer Deposited Metal Oxide Thin Films

Modification of semiconductor surfaces via the growth of metal oxide overlayers, particularly by atomic layer deposition (ALD), has become a topic of recent interest for surface passivation and chemical protection in semiconductor/liquid junctions. For example, in photoelectrochemical water splitting, semiconductor surfaces typically must be protected with insulating or conducting layers that are stable in the electrochemical environment. Further, ALD thin films have been used as overlayers in a variety of other environments including those relevant to batteries, corrosion protection of metals, and for water diffusion barriers. Although thermodynamic stability of a solid phase in various environments can be readily assessed, more complex phenomena such as film hydration and dynamic dissolution/precipitation can occur, dramatically impacting the efficacy of thin protective ALD films. Motivated by this widespread interest in ALD protective layers, we have examined the chemical stability of the two of the most common ALD materials, alumina and titania, in a variety of environments. Films were deposited using thermal ALD using trimethylaluminum and tetrakis dimethylamido titanium for alumina and titania, respectively. Film thickness was then monitored after immersion in various liquid media, which included acidic, neutral and basic aqueous solutions and mercury. Surface morphology was investigated using atomic force microscopy. Our results indicate a drastic increase in stability of the ALD films after post-deposition thermal treatment. Further, for alumina films in pure water, a dramatic restructuring occurs changing film density, thickness, and morphology. Mercury contacts induce a slow increase in film thickness that is attributed to mercury oxide deposition. Finally, we report how the effective surface recombination velocities at these interfaces evolve over the course of thermal annealing and various solution treatments. These results provide important guidelines for the applicability of ALD oxides as protective/passivating films on semiconductor electrodes for applications in sensing and photoelectrochemical water splitting.

Method for Aluminum Oxide Thin Films Prepared through Low Temperature Atomic Layer Deposition for Encapsulating Organic Electroluminescent Devices.

Preparation of dense alumina (Al2O3) thin film through atomic layer deposition (ALD) provides a pathway to achieve the encapsulation of organic light emitting devices (OLED). Unlike traditional ALD which is usually executed at higher reaction n temperatures that may affect the performance of OLED, this application discusses the development on preparation of ALD thin film at a low temperature. One concern of ALD is the suppressing effect of ambient temperature on uniformity of thin film. To mitigate this issue, the pumping time in each reaction cycle was increased during the preparation process, which removed reaction byproducts and inhibited the formation of vacancies. As a result, the obtained thin film had both high uniformity and density properties, which provided an excellent encapsulation performance. The results from microstructure morphology analysis, water vapor transmission rate, and lifetime test showed that the difference in uniformity between thin films prepared at low temperatures, with increased pumping time, and high temperatures was small and there was no obvious influence of increased pumping time on light emitting performance. Meanwhile, the permeability for water vapor of the thin film prepared at a low temperature was found to reach as low as 1.5 × 10−4 g/(m2·day) under ambient conditions of 25 °C and 60% relative humidity, indicating a potential extension in the lifetime for the OLED.

Magnetic characterization and electrical field-induced switching of magnetite thin films synthesized by atomic layer deposition and subsequent thermal reduction

Magnetite (Fe3O4) of high quality was prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. The reduction process in hydrogen atmosphere was investigated by in situ x-ray diffraction studies as a function of temperature. A complete reduction to Fe3O4 was confirmed within a narrow temperature window during the thermal treatment. Magnetic characterization of magnetite thin films as a function of temperature, applied magnetic field and magnetic field orientation were performed. The highly stoichiometry- and impurity-sensitive Verwey transition was observed in magnetic and electrical measurements. Moreover, the isotropic point at which the magnetocrystalline anisotropy of magnetite vanishes was unveiled. Both findings prove, first, the formation of the magnetite phase against the undesired maghemite and, second, the quality of the ALD thin films to be comparable with samples grown by molecular beam epitaxy. The magnetic easy and hard axis could be found to be in-plane and out-of-plane, respectively. Consistent with angular-dependent studies of the coercive field, additionally performed first-order reversal curve measurements revealed a complex micromagnetic structure with different magnetization reversal paths for both configurations. Finally, electric field-induced resistive switching was studied in detail being in perfect agreement with results of single-crystalline samples. The presented data and its analysis support the assumption of previous works of the magnetization reversal in magnetite nanotubes, suggest improvement for future magnetization studies of nanostructures by exploiting the isotropic point and might open new paths for low-cost resistive switching devices.

Atomic layer deposition coating of carbon nanotubes with aluminum oxide alters pro-fibrogenic cytokine expression by human mononuclear phagocytes in vitro and reduces lung fibrosis in mice in vivo.

BackgroundMulti-walled carbon nanotubes (MWCNTs) pose a possible human health risk for lung disease as a result of inhalation exposure. Mice exposed to MWCNTs develop pulmonary fibrosis. Lung macrophages engulf MWCNTs and produce pro-fibrogenic cytokines including interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and osteopontin (OPN). Atomic layer deposition (ALD) is a novel process used to enhance functional properties of MWCNTs, yet the consequence of ALD-modified MWCNTs on macrophage biology and fibrosis is unknown.MethodsThe purpose of this study was to determine whether ALD coating with aluminum oxide (Al2O3) would alter the fibrogenic response to MWCNTs and whether cytokine expression in human macrophage/monocytes exposed to MWCNTs in vitro would predict the severity of lung fibrosis in mice. Uncoated (U)-MWCNTs or ALD-coated (A)-MWCNTs were incubated with THP-1 macrophages or human peripheral blood mononuclear cells (PBMC) and cell supernatants assayed for cytokines by ELISA. C57BL6 mice were exposed to a single dose of A- or U-MWCNTs by oropharyngeal aspiration (4 mg/kg) followed by evaluation of histopathology, lung inflammatory cell counts, and cytokine levels at day 1 and 28 post-exposure.ResultsALD coating of MWCNTs with Al2O3 enhanced IL-1β secretion by THP-1 and PBMC in vitro, yet reduced protein levels of IL-6, TNF-α, and OPN production by THP-1 cells. Moreover, Al2O3 nanoparticles, but not carbon black NPs, increased IL-1β but decreased OPN and IL-6 in THP-1 and PBMC. Mice exposed to U-MWCNT had increased levels of all four cytokines assayed and developed pulmonary fibrosis by 28 days, whereas ALD-coating significantly reduced fibrosis and cytokine levels at the mRNA or protein level.ConclusionThese findings indicate that ALD thin film coating of MWCNTs with Al2O3 reduces fibrosis in mice and that in vitro phagocyte expression of IL-6, TNF-α, and OPN, but not IL-1β, predict MWCNT-induced fibrosis in the lungs of mice in vivo.

A non-destructive method for measuring the mechanical properties of ultrathin films prepared by atomic layer deposition

The mechanical properties of ultrathin films synthesized by atomic layer deposition (ALD) are critical for the liability of their coated devices. However, it has been a challenge to reliably measure critical properties of ALD films due to the influence from the substrate. In this work, we use the laser acoustic wave (LAW) technique, a non-destructive method, to measure the elastic properties of ultrathin Al2O3 films by ALD. The measured properties are consistent with previous work using other approaches. The LAW method can be easily applied to measure the mechanical properties of various ALD thin films for multiple applications.

Precursor Development and Application for Atomic Layer Deposition

As a promising technique for thin film growth, atomic layer deposition (ALD) has been widely applied in various fields of microelectronics such as semiconductor, dielectric materials, metal electrode, and transparent conductive oxide as well as energy, display, and biotechnology. In the areas of electronics, the ALD technique needs appropriate precursors which have high vapor pressure, comparatively low deposition temperature, high deposition rate, and chemically and thermally stable during transportation from canister to deposition chamber. In many cases, the conventional metal complexes have been applied as precursors in ALD process without tuning the improvement of the characteristics to be required in device manufacture.We have focused on the development of the target-oriented suitable metal precursors on the molecular level design for thin film growth by ALD. During the new precursor development, we have succeeded in preparing the optimum compounds for ALD thin film technology. The metal precursors newly synthesized at KRICT have been successfully adapted to deposit metal and metal oxide thin films using ALD in our laboratory and other academic research groups. In this presentation we will talk about our research results of design and synthesis of new metal precursors and their application to electronic devices with ALD, specially focusing on the highly concentrated precursors in electronic device manufacture.

Highly conductive SnO2 thin films deposited by atomic layer deposition using tetrakis-dimethyl-amine-tin precursor and ozone reactant

Highly conductive SnO2 thin films were grown by atomic layer deposition (ALD) in a wide growth temperature range (50°C–250°C), using a tetrakis-dimethyl-amine tin (TDMASn) precursor and an ozone reactant. The ozone SnO2 ALD thin films showed excellent electrical properties (5.63×10−4Ωcm) over 200°C, but the electrical properties of the films were not measured at low growth temperature (under 125°C). In order to verify the origin of the electrical properties as a function of growth temperature, the growth behavior and chemical bonding states, film crystallinity, surface roughness, and optical properties were examined. The ALD ozone SnO2 thin films deposited above the 200°C growth temperature had high carrier concentration (3.2×1020–1.2×1021) and Hall mobility (~32cm2V/s). Also, films deposited at 250°C exhibited a polycrystalline structure and high transmittance (over 80% at 550nm wavelength). As a transparent conductive oxide material, the film properties of ALD ozone SnO2 thin films are very suitable due to their excellent high conductivity and reasonable transmittance.

Sealing of Hard CrN and DLC Coatings with Atomic Layer Deposition

Atomic layer deposition (ALD) is a thin film deposition technique that is based on alternating and saturating surface reactions of two or more gaseous precursors. The excellent conformality of ALD thin films can be exploited for sealing defects in coatings made by other techniques. Here the corrosion protection properties of hard CrN and diamond-like carbon (DLC) coatings on low alloy steel were improved by ALD sealing with 50 nm thick layers consisting of Al2O3 and Ta2O5 nanolaminates or mixtures. In cross sectional images the ALD layers were found to follow the surface morphology of the CrN coatings uniformly. Furthermore, ALD growth into the pinholes of the CrN coating was verified. In electrochemical measurements the ALD sealing was found to decrease the current density of the CrN coated steel by over 2 orders of magnitude. The neutral salt spray (NSS) durability was also improved: on the best samples the appearance of corrosion spots was delayed from 2 to 168 h. On DLC coatings the adhesion of the ALD sealing layers was weaker, but still clear improvement in NSS durability was achieved indicating sealing of the pinholes.

Recent Advances Using Guanidinate Ligands for Chemical Vapour Deposition (CVD) and Atomic Layer Deposition (ALD) Applications

Volatile metal complexes are important for chemical vapour deposition (CVD) and atomic layer deposition (ALD) to deliver metal components to growing thin films. Compounds that are thermally stable enough to volatilize but that can also react with a specific substrate are uncommon and remain unknown for many metal centres. Guanidinate ligands, as discussed in this review, have proven their utility for CVD and ALD precursors for a broad range of metal centres. Guanidinate complexes have been used to deposit metal oxides, metal nitrides and pure metal films by tuning process parameters. Our review highlights use of guanidinate ligands for CVD and ALD of thin films over the past five years, design trends for precursors, promising precursor candidates and discusses the future outlook of these ligands.

Efficiency Enhancement and Anti-Corrosion Protection on Silicon Solar Cells by Atomic-Layer-Deposited Al2O3 Conformal Shell Layer on Antireflective ZnO Nanorod Array

Efficient silicon solar cells with ZnO/Al2O3 core-shell nanorod array (NRA) as the antireflective and anti-corrosion protective structures are reported. Vertically aligned ZnO NRA was synthesized by a low-temperature aqueous chemical process, and a ZnO seed layer for NRA and a highly conformal Al2O3 shell layer were deposited by the atomic layer deposition (ALD) technique at low deposition temperatures. As compared with the silicon solar cells without any antireflective structures, ∼30% increment of short-circuit current density and ∼50% enhancement of efficiency were achieved due to the graded refractive index structure and omnidirectional light scattering of the ZnO/Al2O3 core-shell NRA. In addition, because of the dense and pinhole-free structure of the ALD thin films, the highly conformal Al2O3 shell layer provides effective protection of the chemically fragile ZnO NRA from harmful environments. A high efficiency of 16.4% could be achieved by the ZnO/Al2O3 core-shell NRA upon the silicon solar cells.

UV-curable top coat protection against mechanical abrasion for atomic layer deposition (ALD) thin film barrier coatings

It has been demonstrated that atomic layer deposition (ALD) is able to produce high quality, single layer, moisture barrier films on polymer substrates. ALD coatings are extremely conformal, which is ideally suited for creating excellent barriers even on highly imperfect surfaces. ALD by substrate translation enables the production of ultra-barrier films at industrial scales by increasing throughput and lowering cost compared to traditional ALD processing techniques. However, because ALD barrier coatings are thin and deposited on relatively soft polymer substrates, they are particularly susceptible to mechanical abrasion during downstream operations, including rewinding. This study demonstrates that an ultra-violet (UV)-curable, acrylic top coat can be used to preserve the ALD thin film's barrier properties against typical downstream mechanical abrasion. Specifically, 1μm top coat thickness protected 8nm ALD barrier film against typical mechanical abrasion to maintain water vapor transmission rate below an analyzer sensitivity limit, 3×10−3g/(m2·d). In addition, several commercially-viable options exist for scaling-up and integrating overcoat application into roll-to-roll systems.

Low temperature Ga2O3 atomic layer deposition using gallium tri-isopropoxide and water

Ga2O3 atomic layer deposition (ALD) was carried out using gallium tri-isopropoxide (GTIP) as a gallium source and H2O as an oxygen source at a low temperature (150°C). The Ga2O3 ALD films show amorphous, smooth, and transparent behavior. The growth behavior and a variety of optical, structural, and electrical properties were investigated by various measurements. The growth behavior of Ga2O3 ALD using GTIP reveals a typical ALD process, and Ga2O3 films on glass substrates show outstanding transmittance (over 90%). The Ga:O ratio was measured as 1:1.7 by the Rutherford backscattering spectrometry, and auger electron spectroscopy confirmed that there was no carbon impurity (under the detection limit). The surface morphology was investigated through an atomic force microscope analysis, and all of the films deposited at 150, 200, and 250°C showed smooth and featureless characteristics. Ga2O3 ALD thin film shows excellent leakage current (1×10−11 A at 1MV/cm) and a very suitable breakdown field (6.5–7.6MV/cm) as compared to previously reported Ga2O3 films. Also, the dielectric constant of the films is similar to that of conventional Ga2O3 films (about 9.23).

Synthesis of VO2 Thin Films by Atomic Layer Deposition with TEMAV as Precursor

Synthesis and growth of Vanadium dioxide on Silicon substrates has been investigated by Atomic Layer Deposition (ALD). ALD Vanadium oxide films were synthesized by using the novel Tetrakis[ethylmethylamino] vanadium {V(NEtMe)4} [TEMAV], as the vanadium precursor source and H2O vapor as the oxidizing source. The as-prepared ALD thin films were amorphous due to low temperature growth at 150 oC and exhibit a mixture of V2O5 and VO2 phases, which originiate from the V4+ and V5+ valence states of Vanadium found in the initially amorphous ALD thin film. We found that VO2 formation is strongly dependent on the amount of pressure and oxygen. The VO2 films were formed at 450 -500 oC and with an oxygen flow rate of less than 1 sccm in a vacuum of 2.7 E-2 Torr. ALD VO2 films, after furnace annealing, demonstrate well-formed roundish grains. The ALD VO2 thin films yielded an rms roughness of 3 nm by AFM analysis and are random polycrystalline after annealing.

Fabrication of Sb2Te3 and Bi2Te3 Multilayer Composite Films by Atomic Layer Deposition

Atomic Layer Deposition (ALD) growth of antimony telluride Sb2Te3 and bismuth telluride Bi2Te3 multilayer composite films has been investigated. We have fabricated Sb2Te3 and Bi2Te3 thin films using (trimethylsilyl) telluride ((Me3Si)2Te), bismuth trichloride (BiCl3) and antimony trichloride (SbCl3) as precursors for telluride, bismuth and antimony respectively. Both metal tellurides exhibit Volmer Weber Island growth mode and have characteristic hexagonal crystallites, which are telluride terminated at the surface making chemisorption rather challenging. We found that the presence of OH- bonds at the surface promotes ALD thin film growth by providing suitable nucleation sites and prevents delamination of the hexagonal platelet shaped crystallites. The use of longer exposure times of precursors during the ALD process increases chemisorptions and interface oxidation aids in the creation of nucleation sites. We present surface morphology studies using FE-SEM analysis.

Role of surface intermediates in enhanced, uniform growth rates of TiO2 atomic layer deposition thin films using titanium tetraisopropoxide and ozone

Atomic layer deposition (ALD) growth of TiO2 thin films from titanium tetraisopropoxide (TTIP) and ozone has been studied as a function of dose and purge recipes. A novel dosing scheme was designed to introduce the TTIP precursor into the reaction chamber in multiple “μpulses” with orwithout delay times for desorption of surface product species, analogous to conventional ALDpurge cycles. Larger doses led to significantly higher growth rates while maintaining excellent uniformity across 100 mm wafers, effects which underscore the importance of surface residence times in rather complex surface reaction pathways. The production of H2O/OH surface species during the TTIP half-cycle is intrinsic to the reaction, leading to secondary reaction mechanisms and believed responsible for the enhanced growth rates and accompanying high uniformity.

Nucleation delay in atomic layer deposition on a thin organic layer and the role of reaction thermochemistry

The atomic layer deposition (ALD) of a series of inorganic thin films on an interfacial organic layer has been examined, focusing on the existence of a delay in thin film nucleation and its dependence on the chemistry of each ALD reaction. The inorganic thin films examined were Al2O3, HfO2, Ta2O5, and TaNx, while the organic layer was a thin (∼5 Å thick) film of poly(ethylene imine), or PEI, on SiO2. The early stages (<50 ALD cycles) of inorganic thin film growth in each case have been characterized using a combination of surface-sensitive techniques including ellipsometry, x-ray photoelectron spectroscopy, and atomic force microscopy. PEI has the effect of attenuating growth to different degrees depending on the subsequently grown ALD thin film, leading to no attenuation of growth for Al2O3, but significant incubation periods, in increasing order, for Ta2O5, HfO2 and TaNx. Angle-resolved x-ray photoelectron spectroscopy of an Al2O3 thin film deposited on PEI|SiO2 demonstrates that, in this case, the PEI thin film is buried between the Al2O3 thin film and the SiO2 substrate, with no significant decrease in the density of nitrogen from the as deposited PEI film. Results from the HfO2 and the Ta-containing thin films indicate that the processes that lead to the attenuation of growth are associated mostly with the second half-cycle of ALD (H2O or NH3 exposure). The length of the incubation time is found to correlate with both the total enthalpy change of the overall ALD reaction, as well as the net internal energy change of a single ligand exchange reaction representative of the second half of the ALD reaction. These results suggest that the reaction thermochemistry, and activation barriers for the reactions involved the ALD process play a key role in determining the length of the incubation period caused by PEI.

Surface Polarity Shielding and Hierarchical ZnO Nano-Architectures Produced Using Sequential Hydrothermal Crystal Synthesis and Thin Film Atomic Layer Deposition

Three-dimensional nanoscale constructs are finding applications in many emerging fields, including energy generation and storage, advanced water and air purification, and filtration strategies, as well as photocatalytic and biochemical separation systems. Progress in these important technologies will benefit from improved understanding of fundamental principles underlying nanostructure integration and bottom-up growth processes. While previous work has identified hydrothermal synthesis conditions to produce nanoscale ZnO rods, sheets, and plates, strategies to systematically integrate these elements into more complex nano-architectures are not previously described. This article illustrates that amorphous nanoscale coatings formed by atomic layer deposition (ALD) are a viable means to modulate and screen the surface polarity of ZnO crystal faces and thereby regulate the growth morphology during successive hydrothermal nanocrystal synthesis. Using this new strategy, this work demonstrates direct integration and sequential assembly of nanocrystalline rods and sheets to produce complex three-dimensional geometric forms, where structure evolution is achieved by modifying the surface growth condition, keeping the hydrothermal growth chemistry unchanged. Therefore, rational planning of seed layer and feature spacing geometries may allow researchers to engineer, at the nanoscale, complex three-dimensional crystalline and semicrystalline constructs for a wide range of future applications.

Nanoindentation Investigation of HfO2 and Al2O3 Films Grown by Atomic Layer Deposition

The challenges of reducing gate leakage current and dielectric breakdown beyond the 45 nm technology node have shifted engineers’ attention from the traditional and proven dielectric to materials of higher dielectric constant also known as high- materials such as hafnium oxide and aluminum oxide . These high- materials are projected to replace silicon oxide . In order to address the complex process integration and reliability issues, it is important to investigate the mechanical properties of these dielectric materials in addition to their electrical properties. In this study, and have been fabricated using atomic layer deposition (ALD) on (100) p-type Si wafers. Using nanoindentation and the continuous stiffness method, we report the elastomechanical properties of and on Si. ALD thin films were measured to have a hardness of and a modulus of , whereas the ALD thin films have a hardness of and a modulus of . The two materials are also distinguished by very different interface properties. forms a hafnium silicate interlayer, which influences its nanoindentation properties close to the interface with the Si substrate, while does not exhibit any interlayer.