Electrical characteristics of metal-oxide-semiconductor capacitors on p-GaAs using atomic layer deposition of ultrathin HfAlO gate dielectric
TL;DR: In this paper, the individual layer thickness of atomic-layer deposited Al2O3 and HfO2 and the postdeposition anneal (PDA) conditions were optimized to obtain a low equivalent oxide thickness of 1.6 nm, low gate leakage of 2.6×10−3
Abstract: Properties of ultrathin HfAlO gate dielectrics on sulfur-passivated p-GaAs were investigated using capacitance-voltage and current-voltage measurement techniques and angle-resolved x-ray photoelectron spectroscopy. By optimizing the individual layer thickness of atomic-layer deposited Al2O3 and HfO2 and the postdeposition anneal (PDA) conditions, a low equivalent oxide thickness of 1.6 nm, low gate leakage of 2.6×10−3 A/cm2 at Vg=Vfb−1 V, and excellent frequency dispersion characteristics were obtained. No interfacial As–O bonding and only a small amount of Ga–O bonding were detected after PDA at 500 °C. These results reveal a good quality dielectric interface on GaAs without an additional interface passivation layer.
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TL;DR: Puurunen et al. as discussed by the authors summarized the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD.
Abstract: Atomic layer deposition (ALD) is gaining attention as a thin film deposition method, uniquely suitable for depositing uniform and conformal films on complex three-dimensional topographies. The deposition of a film of a given material by ALD relies on the successive, separated, and self-terminating gas–solid reactions of typically two gaseous reactants. Hundreds of ALD chemistries have been found for depositing a variety of materials during the past decades, mostly for inorganic materials but lately also for organic and inorganic–organic hybrid compounds. One factor that often dictates the properties of ALD films in actual applications is the crystallinity of the grown film: Is the material amorphous or, if it is crystalline, which phase(s) is (are) present. In this thematic review, we first describe the basics of ALD, summarize the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD [R. L. Puurunen, J. Appl. Phys. 97, 121301 (2005)], and give an overview of the status of processing ternary compounds by ALD. We then proceed to analyze the published experimental data for information on the crystallinity and phase of inorganic materials deposited by ALD from different reactants at different temperatures. The data are collected for films in their as-deposited state and tabulated for easy reference. Case studies are presented to illustrate the effect of different process parameters on crystallinity for representative materials: aluminium oxide, zirconium oxide, zinc oxide, titanium nitride, zinc zulfide, and ruthenium. Finally, we discuss the general trends in the development of film crystallinity as function of ALD process parameters. The authors hope that this review will help newcomers to ALD to familiarize themselves with the complex world of crystalline ALD films and, at the same time, serve for the expert as a handbook-type reference source on ALD processes and film crystallinity.
1,160 citations
TL;DR: In this article, the interfacial state density (Dit) was derived by applying the conductance method at 25 and 150°C on both p-type and n-type GaAs metal-oxide-semiconductor capacitors to establish the Dit spectra in proximity of the critical midgap region.
Abstract: To effectively passivate the technologically important GaAs (001) surfaces, in situ deposition of Al2O3 was carried out with molecular beam epitaxy. The impacts of initial GaAs surface reconstruction and post-deposition annealing have been systematically investigated. The corresponding interfacial state density (Dit) were derived by applying the conductance method at 25 and 150 °C on both p-type and n-type GaAs metal-oxide-semiconductor capacitors to establish the Dit spectra in proximity of the critical midgap region. We show that significant reduction of Dit near the midgap is achieved by applying an optimized thermal annealing on samples grown on a Ga-rich (4×6) reconstructed surface.
69 citations
TL;DR: In this paper, the energy band alignment and band gap of Al2O3 and HfAlO films grown by atomic layer deposition on 4H-SiC were determined using x-ray photoelectron spectroscopy.
Abstract: Energy band alignment and band gap of Al2O3 and HfAlO films grown by atomic layer deposition on 4H–SiC were determined using x-ray photoelectron spectroscopy. Al2O3 exhibited a symmetric band profile with a conduction band offset (ΔEC) of 1.88 eV and a valence band offset (ΔEV) of 1.87 eV. HfAlO yielded a smaller ΔEC of 1.16 eV and ΔEV of 1.59 eV. The higher dielectric constant and higher effective breakdown field of HfAlO compared to Al2O3, coupled with sufficient electron and hole barrier heights, makes it a potential dielectric for use on 4H–SiC, and provokes interest in further investigation of HfAlO/4H–SiC properties.
63 citations
TL;DR: In this article, a unique tilt target sputtering configuration was employed to produce highly homogenous nanoparticle arrays, with sizes ranging from ∼07 to 134 nm and particle densities of ∼33 −59 cm−2.
Abstract: Charge storage characteristics of ultra-small Pt nanoparticle embedded devices were characterized by capacitance-voltage measurements A unique tilt target sputtering configuration was employed to produce highly homogenous nanoparticle arrays Pt nanoparticle devices with sizes ranging from ∼07 to 134 nm and particle densities of ∼33–59 × 1012 cm−2 were embedded between atomic layer deposited and e-beam evaporated tunneling and blocking Al2O3 layers These GaAs-based non-volatile memory devices demonstrate maximum memory windows equivalent to 65 V Retention characteristics show that over 80% charged electrons were retained after 105 s, which is promising for device applications
61 citations
TL;DR: In this article, a bilayer dielectric consisting of thin nitrided SiO2 covered by 25 nm of Al2O3 deposited using atomic layer deposition was used to obtain high-mobility gate-controlled power devices.
Abstract: Lateral metal-oxide-semiconductor field-effect transistors (MOSFETs) have been fabricated on 4H-SiC utilizing deposited dielectrics and gate-last processing. The bilayer dielectric consists of thin nitrided SiO2 covered by 25 nm of Al2O3 deposited using atomic layer deposition. Field-effect mobility and threshold voltage (VT) vary with SiC nitric oxide (NO) anneal temperature. Peak mobility of 106 cm2/V⋅s was obtained with corresponding VT of 0.8 V. The peak mobility decreases to 61 cm2/V⋅s with a lower temperature NO anneal, while the VT increased to 1.4 V. Thus with proper gate engineering, high-mobility normally off MOSFET devices can be obtained, leading to higher-performance gate-controlled power devices.
45 citations
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TL;DR: In this paper, the authors have studied hafnium oxide and aluminum oxide grown on gallium arsenide by atomic layer deposition and showed that as-deposited films are continuous and predominantly amorphous.
Abstract: High-performance metal-oxide-semiconductor field effect transistors (MOSFETs) on III–V semiconductors have long proven elusive. High-permittivity (high-κ) gate dielectrics may enable their fabrication. We have studied hafnium oxide and aluminum oxide grown on gallium arsenide by atomic layer deposition. As-deposited films are continuous and predominantly amorphous. A native oxide remains intact underneath HfO2 during growth, while thinning occurs during Al2O3 deposition. Hydrofluoric acid etching prior to growth minimizes the final interlayer thickness. Thermal treatments at ∼600°C decompose arsenic oxides and remove interfacial oxygen. These observations explain the improved electrical quality and increased gate stack capacitance after thermal treatments.
317 citations
TL;DR: In this article, the electrical properties of metal-oxide-semiconductor capacitors on molecular beam epitaxial GaAs in situ passivated with ultrathin amorphous Si (a-Si) layer and with ex situ deposited HfO2 gate oxide and TaN metal gate were demonstrated.
Abstract: We demonstrate the electrical properties of metal-oxide-semiconductor capacitors on molecular beam epitaxial GaAs in situ passivated with ultrathin amorphous Si (a-Si) layer and with ex situ deposited HfO2 gate oxide and TaN metal gate. Minimum thickness of the Si interface passivation layer of 1.5 nm is needed to prevent the Fermi level pinning and provide good capacitance-voltage characteristics with equivalent oxide thickness of 2.1 nm and leakage current of ⩽1.0mA∕cm2. Transmission electron microscopy analysis showed that the Si layer was oxidized up to 1.4 nm during ex situ processing while the interface between the GaAs and a-Si remained atomically sharp without any sign of interfacial reaction.
187 citations
TL;DR: In this article, the electrical and interfacial properties of MOS capacitors with atomic layer deposited (ALD) Al2O3, HfO2, and HfAlO gate dielectrics on sulfur-passivated (Spassivated) GaAs substrates were investigated.
Abstract: In this paper, electrical and interfacial properties of MOS capacitors with atomic layer deposited (ALD) Al2O3, HfO2, and HfAlO gate dielectrics on sulfur-passivated (S-passivated) GaAs substrates were investigated. HfAlO on p-type GaAs has shown superior electrical properties over Al2O3 or HfO2 on GaAs, and it is attributed to the reduction of the Ga-O formation at the interfacial layer. HfAlO on p-type GaAs exhibits the best electrical properties after postdeposition annealing (PDA) at 500degC. It is found that PDA, at above 500degC, causes a significant amount of Ga and As out-diffusion into the high-k dielectric, which degrades the interface, as well as bulk high-k properties.
138 citations
TL;DR: In this article, the kinetics of the interfacial layer (IL) growth between Hf aluminates and the Si substrate during high-temperature rapid thermal annealing (RTA) in either N2 (∼10 Torr) or high vacuum ( ∼2×10−5) was studied by highresolution x-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy.
Abstract: The kinetics of the interfacial layer (IL) growth between Hf aluminates and the Si substrate during high-temperature rapid thermal annealing (RTA) in either N2 (∼10 Torr) or high vacuum (∼2×10−5 Torr) is studied by high-resolution x-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy. The significant difference of the IL growth observed between high vacuum and relatively oxygen-rich N2 annealing (both at 1000 °C) is shown to be caused by the oxygen species from the annealing ambient. Our results also show that Hf aluminates exhibit much stronger resistance to oxygen diffusion than pure HfO2 during RTA in N2 ambient, and the resistance becomes stronger with more Al incorporated into HfO2. This observation is explained by the combined effects of (i) smaller oxygen diffusion coefficient of Al2O3 than HfO2, and (ii) higher crystallization temperature of the Hf aluminates.
96 citations
TL;DR: In this article, the capacitance-voltage characteristics of TaN∕HfO2∕n-GaAs metaloxide-semiconductor capacitors, with an equivalent oxide thickness (EOT) of 10.9A, low frequency dispersion, and a low leakage current density (Jg) of ∼10−6A∕cm2 at ∣VG−VFB∣=1V, were presented.
Abstract: We present the capacitance-voltage characteristics of TaN∕HfO2∕n-GaAs metaloxide-semiconductor capacitors, with an equivalent oxide thickness (EOT) of 10.9A, low frequency dispersion, and a low leakage current density (Jg) of ∼10−6A∕cm2 at ∣VG−VFB∣=1V. Physical vapor deposited high-k dielectric film (HfO2) and a thin germanium (Ge) interfacial control layer (ICL) were used to achieve the low EOTs. As postdeposition annealing (PDA) time increases beyond a critical point, EOT and Jg also abnormally increase due to the degradation of the interface between Ge and GaAs surface, which was well indicated in electron energy loss spectroscopy, energy dispersive x-ray spectroscopy, and transmission electron microscopy analyses. Results indicate that a thin Ge ICL, optimized conditions for PDA, as well as high-k material (HfO2) play important roles in allowing further EOT scale down and in providing a high-quality interface.
65 citations