High-k Dielectric Applications Research Articles

Interpretable machine learning boosting the discovery of targeted organometallic compounds with optimal bandgap

Organometallic compounds (OMCs) have attracted tremendous attention in various fields, such as photovoltaic cell and high-k dielectric application, due to their beneficial properties. Despite their potential, the progression of OMCs into industrial applications is hindered by the limited databases available for their properties and the absence of efficient surrogate models. To address this, in this study, optimally selected feature-based surrogate models for predicting the electronic properties of OMCs are constructed via various multiscale features and extensive database. To this end, high-throughput calculation was performed to obtain electronic properties of more than 18k materials generally known as organometallics, augmenting around 12k organic materials obtained from the public open data set, OMDB-GAP1. For generating features closely related to OMCs, descriptors encapsulating the information ranging local to global, also other widely-used composition-, structure-based features (more than 3.5k in total) were employed. Among these descriptors, we identified 48 critical features that elucidates the physicochemical underpinnings of OMCs’ properties, suggesting their impact on the properties of OMCs. The light gradient boosting machine model achieved high-accuracy predictions across the entire database with just 1 % of the total descriptors, sufficiently compared to the entire sets (decreased of around 0.01 by R2 score and 0.01 eV by MAE). Furthermore, the efficacy of active learning process was demonstrated to find OMCs with optimal properties rapidly. As a result, expected improvement outperforms other methods by identifying 69 % of the target materials only searching 46 % of the total search space. Our constructed platform with a high-throughput calculated database can pave the way for the rapid screening of OMCs for the targeted industrial application, and suggest a comprehensive grasp of the intrinsic properties of OMCs and related compounds.

Composition optimization of HfxZr1-xO2 thin films to achieve the morphotrophic phase boundary for high-k dielectrics

HfxZr1-xO2 thin films exhibit a high dielectric constant at the morphotropic phase boundary (MPB), which is beneficial for high-k dielectric applications. To minimize the equivalent oxide thickness, the effects of various HZO thicknesses and compositions on the MPB were investigated. In general, HZO films with a thickness of 10 nm exhibit a high dielectric constant owing to MPB at a composition of Hf:Zr = 3:7. However, it was confirmed that composition optimization is required for HZO films with thicknesses below 10 nm to achieve an MPB. As the HZO thickness decreases, a low Zr ratio is favorable for achieving a high dielectric constant (>45) by MPB, which is expected to be due to the large impact of the interface that consequently induces a change in phase formation. Results of electrical and x-ray diffraction analyses confirmed that a high dielectric constant was obtained when the ratio of the tetragonal phase increased and that the tetragonal phase was well formed at a low Zr ratio in the 6 nm-thick HZO film. Therefore, the optimal ratio between the tetragonal and orthorhombic phases should be determined to achieve MPB in HZO thin films, and this can be achieved by composition optimization.

Atomic layer deposited strontium niobate thin films as new high-k dielectrics

Strontium niobate thin films have potential for next-generation high-k dielectric applications. In this work, we investigated the fabrication of SrxNb1-xOy thin films by atomic layer deposition for the first time and examined their physical and electrical characteristics. The composition of the SrxNb1-xOy thin film could be effectively controlled by introducing a super-cycle, and it was confirmed that the crystallinity after annealing varied depending on the composition. The Sr-rich film was crystalline after annealing and showed a high dielectric constant of approximately 75. In addition, it was observed that the Nb-rich film had a relatively large dielectric constant of approximately 65 even though it was amorphous, confirming that it could be applied as a next-generation high-k material. This research is the first step toward a new high-k dielectric candidate, which we believe can be applied to next-generation semiconductor devices through further research to improve the characteristics.

Temperature dependent dielectric and electric properties of zinc silicate nanorods

In this article, single crystalline pristine zinc silicate (Zn2SiO4) nanorods were grown by low temperature hydrothermal technique. The morphological and crystal structural analysis reveals the formation of nanostructures with nanorods shape and willemite structure of the α-Zn2SiO4 nanorods phase. Field emission-scanning electron microscope (FE-SEM) studies shows that length and radius of grown nanorods were in range of 1.5–2μm and 25–30 nm, respectively. Presence of various characteristic peaks in Zn2SiO4 nanorods were confirmed by Fourier transform-infrared spectroscopy (FT-IR) analysis. A very high dielectric constant of 222 was observed at room temperature and a sharp increase in the dielectric constant with an ultra-high dielectric constant of ∼19185 was observed at 100 °C. The variation of dielectric constant, loss and ac conductivity as a function of frequency was also studied. Temperature dependent (RT to 300 °C) dielectric constant, dissipation factor and ac conductivity were also investigated in the frequency range of 20 Hz–2MHz for the first time. It was observed that ac conductivity increased with increase of temperature up to 100 °C and then decreased. Such high dielectric and electric properties of Zn2SiO4 shows its great potential towards various nano-scale high energy capacitor and high-k dielectric nano-transistor applications.

Nitrogen plasma-induced HfSiON film growth from Hf nanoscale islands on SiO2/Si

HfSiON films for high-k dielectric applications are synthesized from Hf nanoscale islands on SiO2/Si(100) substrates using the exposure of nitrogen inductively coupled plasma (ICP). The process consists of the novel interfacial reaction of nanoscale islands with the substrate induced by plasma-derived radicals and ions. The Hf metal islands nucleate on an SiO2/Si(100) surface by strain-induced engineering during electron beam evaporation. In vacuo AFM measurement shows that the N2 ICP exposure collapses the islands to form films. XPS analysis shows that the ICP exposure initially nitrides Hf islands in 1 min. Then, it induces the intermixing of the base SiO2 with HfN in the next stage. The rapid nitridation of Hf is the unique feature of the process initiated from nanoscale islands. The chemical composition ratio of Hf:Si:N in the film can be roughly controlled to be 1:1:1 with an ICP exposure time of 20 min. The uniformity of the grown films depends on the initial uniformity of the islands and the surface diffusion of materials. The study is a unique example of the film-growth method based on the nanoscale interaction of the surface of nucleated islands and the substrate material induced by plasmas.

Sol-gel derived low temperature HfO2-GPTMS hybrid gate dielectric for a-IGZO thin-film transistors (TFTs)

In this study, we prepared inorganic-organic HfO2-GPTMS hybrid films by a simple sol-gel method at low temperature for high-k dielectric gate applications. The hybrid films were deposited by spin coating process, followed by annealing at 150 °C. The hybrid dielectric material was characterized by Spectroscopic ellipsometry (SE), AFM, FESEM, FTIR, TGA, and XPS techniques. The resulting hybrid films exhibit homogeneous and smooth surface with high optical transparency. Their dielectric properties were analysed by measuring leakage current and capacitance versus voltage of metal-insulator-metal (MIM) capacitor structures. From this analysis, the leakage current density at − 5 V, capacitance and dielectric constant at 1 MHz measured on the hybrid films were 10−7 A/cm2, 51.3 nF/cm2 and of 11.4 respectively. Finally, to investigate the electrical performance of the hybrid thin films as a dielectric gate in thin film transistors (TFTs), bottom-gate TFTs were fabricated by depositing the HfO2-GPTMS dielectric gate layer on ITO-coated glass substrate and subsequently a sputtered a-IGZO thin film as the channel layer. The electrical response of the resulting TFTs demonstrated good saturation mobility of 4.74 cm2 V−1 s−1, very low threshold voltage of 0.3 V and Ion/Ioff current ratio of 104, with low operating voltage under 8 V.

(Invited) Beyond the Highs and Lows: A Selectively Colorful Yet Chilly Perspective on the Future of Dielectrics in Nanoelectronic Devices

High-dielectric constant (high-k) gate oxides and low-dielectric constant (low-k) interlayer dielectrics (ILD) have dominated the nanoelectronic materials research scene over the past decade, but have recently reached a state of maturity and perhaps the limits of their scaling. Based on this, one may ponder the direction of nanoelectronic dielectric research and the future of the field. However, as we will clarify, the well has fortunately not yet run dry! In this address, we seek to illustrate that high-k gate oxides and low-k ILDs represent just a small fraction of the numerous dielectric materials utilized in nanoelectronic products and that numerous new applications for dielectric materials are emerging as the industry transistions to novel patterning schemes and prepares for life post CMOS scaling. We will begin by briefly exploring the entirety of dielectric materials utilized in advanced nanoelectronic products with a particular focus on often ignored etch stopping, diffusion barrier, and passivation dielectrics and their more specialized requirements relative to high-k and low-k dielectrics. We will then transition to examining the various novel pitch division schemes being developed to cope with the delay of EUV lithography and the abundant new dielectric material applications these schemes create. We will specifically focus on the various new spacer and hard mask dielectrics that pitch division requires, their colorful selectivity requirements, and suggest future research needed to enable even more exotic patterning schemes. We will further examine how what was once old can become new again and specifically explore how both high-k and low-k dielectrics are being utilized to fill the needs of future beyond CMOS devices. In particular, the application of high-k and low-k dielectrics in novel resistive switching, magnetic, and nano-electro-mechanical device and sensor applications will be surveyed along with the research needed to extend these materials into even more diverse applications. We will conclude by reviewing the unique obstacles that dielectric materials present for the realization of advanced cryogenic quantum computing architectures and the necessary associated research vectors to prevent dielectrics from becoming quantum computing’s Achilles heel.

Research on c-HfO2 (0 0 1)/α-Al2O3 (1 -1 0 2) interface in CTM devices based on first principle theory

With the growing application of high-k dielectrics, the interface between HfO2 and Al2O3 play a crucial role in CTM devices. To clearly understand the interaction of the HfO-AlO interface at the atomic and electronic scale, the bonding feature, electronic properties and charge localized character of c- HfO2 (0 0 1)/α-Al2O3 (1 -1 0 2) interface has been investigated by first principle calculations. The c- HfO2 (0 0 1)/α-Al2O3 (1 -1 0 2) interface has adhesive energy about -1.754 J/m2, suggesting that this interface can exist stably. Through analysis of Bader charge and charge density difference, the intrinsic interfacial gap states are mainly originated from the OII and OIII types oxygen atoms at the interface, and only OIII type oxygen atoms can localized electrons effectively and are provided with good reliability during P/E cycles, which theoretically validate the experimental results that HfO2/Al2O3 multi-layered charge trapping layer can generate more effective traps in memory device. Furthermore, the influence of interfacial gap states during P/E cycles in the defective interface system have also been studied, and the results imply that defective system displays the degradation on the reliability during P/E cycles, while, the charge localized ability of interfacial states is stronger than intrinsic oxygen vacancy in the trapping layer. Besides, these charge localized characters are further explained by the analysis of the density of states correspondingly. In sum, our results compare well with similar experimental observations in other literatures, and the study of the interfacial gap states in this work would facilitate further development of interface passivation.

Impact of thin high-k dielectrics and gate metals on RF characteristics of 3D double gate junctionless transistor

RF performance of 3D double gate junctionless transistor (JLT) is investigated considering thin high-k dielectrics and gate metals. The 3D double gate junctionless transistor (JLT) with 20nm gate length is designed and simulated in order to study the RF parameters such as transconductance, transconductance generation factor, output conductance and resistance, intrinsic capacitance, cut-off frequency, early voltage, and intrinsic gain. High-k dielectric gate oxide and gate metals have effect on the DC characteristics of JLT. However, in order to evaluate the impact of high-k gate dielectrics on the RF performance of the device, SiO2, Si3N4, HfO2 dielectrics are considered and compared their performances. Furthermore, the effect of various gate metals on RF performances of the device is also discussed. Gate oxide with higher-k value improves the transconductance, output conductance, and intrinsic gain of the device. While, gate metal with lower work function exhibits better RF characteristics in JLT, application of different high-k dielectrics and gate metal have no improvement in cut-off frequency. The investigation gives an idea to optimize the RF performance of the device using suitable gate dielectric and gate metal. This investigation helps to create an opportunity for the junctionless transistor to realize high performances RF circuits.

Stress and Phase Engineered ZrO2/Ge for High-k Dielectric Applications

ABSTRACTZrO2/Ge is potential high-k dielectric candidate to replace silicon based devices. Controlling stress in zirconia film and stabilizing high dielectric constant phase is crucial for high-k application. A precise control of stress and phase selectivity in high-k thin films is demonstrated. Thin films of ZrO2 were grown by reactive sputter deposition. Wide range of growth stress in thin films from -0.3 to -2.8 GPa can be tuned by growth rate control. Adatom incorporation into grain boundary was the dominant source of observed stress. Phase selectivity in zirconia was achieved by tuning growth parameters.

Tb2O3 thin films: An alternative candidate for high-k dielectric applications

We are reporting the growth and structural, optical, and dielectric properties of Tb2O3, a relatively unexplored high-k dielectric material. A pulsed-laser deposition technique was used to grow Tb2O3 thin-films on four different substrates: Si(100), SrTiO3(100), LaAlO3(100), and MgO(100). High-resolution X-ray diffraction and transmission electron microscopy results confirmed that film growth in an oxygen-rich (10−1 Torr) environment yields nearly single-crystal C-phase films, while a low-oxygen (10−6 Torr) environment growth results in the formation of monoclinic polycrystalline B-phase films. Optical transmission measurements showed that the bandgap of Tb2O3 is direct in nature with a value of 2.8 eV and 3.4 eV for the cubic and monoclinic phases, respectively. By measuring the capacitance of test devices, quite high dielectric constants of 13.5 and 24.9 were obtained for the B- and C-phase Tb2O3 films, respectively.

Computational investigation of the phase stability and the electronic properties for Gd-doped HfO2

Rare earth doping is an important approach to improve the desired properties of high-k gate dielectric oxides. We have carried out a comprehensive theoretical investigation on the phase stability, band gap, formation of oxygen vacancies, and dielectric properties for the Gd-doped HfO2. Our calculated results indicate that the tetragonal phase is more stable than the monoclinic phase when the Gd doping concentration is greater than 15.5%, which is in a good agreement with the experimental observations. The dopant's geometric effect is mainly responsible for the phase stability. The Gd doping enlarges the band gap of the material. The dielectric constant for the Gd-doped HfO2 is in the range of 20–30 that is suitable for high-k dielectric applications. The neutral oxygen vacancy formation energy is 3.2 eV lower in the doped material than in pure HfO2. We explain the experimental observation on the decrease of photoluminescence intensities in the Gd-doped HfO2 according to forming the dopant-oxygen vacancy complexes.

Extraction and dielectric properties of curcuminoid films grown on Si substrate for high-k dielectric applications

Abstract Curcuminoids were extracted from turmeric powder and evaporated in vacuum to prepare thin films on p-Si and glass substrates for dielectric and optical investigations. The optical absorption spectrum of the prepared amorphous film was not identical to that of the molecular one, which was identified by a strong wide absorption band in between ∼220 and 540 nm. The onset energy of the optical absorption of the film was calculated by using Hamberg et al. method. The dielectric properties of this material were systematically studied for future eco friendly applications in metal–insulator–semiconductor MIS field of applications. The complex dielectric properties were studied in the frequency range of 1–1000 kHz and was analysed in-terms of dielectric impedance Z * ( ω ) and modulus M * ( ω ) . Generally, the curcuminoid complex can be considered as a high- k material and can be used in the environmental friendly production of microelectronic devices.

Application of high-k dielectrics in novel semiconductor devices

As the feature size of MOSFET scales beyond 45 nm, SiO2 as gate dielectric fails to meet the performance requirement because of the high gate oxide leakage current. It is necessary to replace SiO2 with high-k materials. However, high-k materials as gate dielectric have some limitations and are not expectedly compatible with the conventional structure, inducing new challenges such as bad interfacial quality, increased threshold voltage, mobility degradation, etc. In this paper we review the problems encountered in the introduction of high-k gate dielectric into planar devices and the solutions in terms of material, device structure and process integration. Some novel applications of high-k materials in new devices and the future trend are also reviewed.

High permittivity Bi24Fe2O39 thin films prepared by a low temperature process

High permittivity Bi24Fe2O39 (BFO) thin films have been deposited on platinized silicon substrates by a low temperature process combining rf magnetron sputtering at room temperature and postdeposition annealing at 450 °C. A nearly pure tetragonal crystal structure with highly (201)-preferred orientation, determined by x-ray diffraction, was formed in the BFO thin film. The BFO film not only exhibits high dielectric permittivity (εr=113) and relatively low loss tangent (tan δ=0.012), but also shows a fairly small quadratic voltage coefficient of capacitance (α∼800 ppm/V2) and a small temperature coefficient of capacitance (αT∼790 ppm/°C). Moreover, the leakage current density, obeying the Fowler–Nordheim tunneling mechanism, remains at a reasonably low level with the increase in applied electric field (J∼10−6–10−4 A/cm2 under E=400 kV/cm). These attractive dielectric and electrical properties make the low temperature processed Bi24Fe2O39 thin film a promising candidate for high-k dielectric applications in silicon-based integrated circuits.

Optical properties and thermal stability of LaYbO3 ternary oxide for high-k dielectric application

A new ternary rare oxide dielectric LaYbO3 film had been prepared on silicon wafers and quartz substrates by reactive sputtering method using a La–Yb metal target. A range of analysis techniques was performed to determine the optical band gap, thermal stability, and electrical property of the deposited samples. It was found the band gap of LaYbO3 film was about 5.8eV. And the crystallization temperature for rapid thermal annealing (20s) was between 900 and 950°C. X-ray photoelectron spectroscopy results indicate the formation of the SiO2 and silicate in the interface between silicon wafer and LaYbO3 film. The dielectric constant is about 23 from the calculation of capacitance–voltage curve, which is comparable higher than previously reported La2O3 or Yb2O3 film.

Progress of High-k Dielectrics Applicable to SONOS-Type Nonvolatile Semiconductor Memories

As a promising candidate to replace the conventional floating gate flash memories, polysilicon-oxide-nitride-oxidesilicon (SONOS)-type nonvolatile semiconductor memories have been investigated widely in the past several years. SONOS-type memories have some advantages over the conventional floating gate flash memories, such as lower operating voltage, excellent endurance and compatibility with standard complementary metal-oxide-semiconductor (CMOS) technology. However, their operating speed and date retention characteristics are still the bottlenecks to limit the applications of SONOS-type memories. Recently, various approaches have been used to make a trade-off between the operating speed and the date retention characteristics. Application of high-k dielectrics to SONOS-type memories is a predominant route. This article provides the state-of-the-art research progress of high-k dielectrics applicable to SONOS-type nonvolatile semiconductor memories. It begins with a short description of working mechanism of SONOS-type memories, and then deals with the materials' requirements of high-k dielectrics used for SONOS-type memories. In the following section, the microstructures of high-k dielectrics used as tunneling layers, charge trapping layers and blocking layers in SONOS-type memories, and their impacts on the memory behaviors are critically reviewed. The improvement of the memory characteristics by using multilayered structures, including multilayered tunneling layer or multilayered charge trapping layer are also discussed. Finally, this review is concluded with our perspectives towards the future researches on the high-k dielectrics applicable to SONOS-type nonvolatile semiconductor memories.

A Comparison of O3 and H2O as Oxygen Sources for Atomic Layer Deposition Processing of HfAlOx Thin Films for High-k Dielectric Nanocapacitor Applications

A comparative study of O3 and H2O as oxidizers for atomic layer deposition (ALD) HfOx and AlOx thin films was carried out employing a 300-mm wafer capable ALD cluster tool. TEMAHf (tetrakis-ethylmethylamino-hafnium) and TMA (trimethyl-aluminium) were used as metal precursors. Process conditions were varied to evaluate the effects on unary metal oxide growth as an approach towards developing a mixed-phase binary metal oxide growth process. Films were characterized using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and capacitance measurements of MOS capacitor structures. Initial testing results of the electrical properties of resulting binary metal oxides will be discussed.

A Comparison of O3 and H2O as Oxygen Sources for Atomic Layer Deposition Processing of HfAlOx Thin Films for High-k Dielectric Nanocapacitor Applications

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Dopant enhanced in nickel silicide formation for high-k dielectric applications

The thermal stability of fully silicided NiSi with arsenic doping on silicon was investigated. The combination of full nickel silicidation gate electrodes and hafnium based high-k gate dielectrics is one of the most promising gate stacks to replace poly-Si/SiO2/Si gate stacks in the future complementary metal–oxide–semiconductor (CMOS) sub-45 nm technology node. The aims of the work were to investigate the Ni silicide phase-related issues associated with arsenic dopant and thermal annealing on Ni–FUSI/HfO2/Si and Ni–FUSI/HfSiO/Si gate stacks. It was found that arsenic-incorporation demonstrated some improvement in both morphology and phase stability of nickel silicided films at high processing temperatures regardless underlying gate dielectrics. The correlations of Ni–Si phase transformation and arsenic doapnt with their electrical and physical changes were established by sheet resistance measurements, X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) analysis. Furthermore, the modulation of the work function (WF) of Ni fully silicided gates by arsenic impurity is presented, comparing the effects of dopant (As) on the WF and silicide phases (NiSi and NiSi2). It confirmed that the work function of NiSi can be tuned by implanting arsenic dopant, but it ineffective for NiSi2 phase.