Structural and optical properties of nitrogen-incorporated HfO2 gate dielectrics deposited by reactive sputtering

High-k HfO_xN_y thin films with different nitrogen-incorporation content have been fabricated on Si (1 0 0) substrate by means of radio-frequency reactive sputtering method. Analyses from X-ray diffraction (XRD) and atomic force microscopic have indicated that the increase of the crystallization temperature of HfO₂ thin films and the decrease of the roughness root-mean-square value of HfO₂ thin films due to the incorporation of nitrogen. Based on a parameterized Tauc-Lorentz (TL) dispersion model, the optical properties of the HfO_xN_y thin films related to different nitrogen-incorporation content are systematically investigated by spectroscopic ellipsometer. Increase in the refractive index and the extinction coefficient and reduction in band gap with increase of nitrogen-incorporation content are discussed in detail.     

Fabrication and characterization of La-doped HfO2 gate dielectrics by metal-organic chemical vapor deposition

La-doped HfO₂ gate dielectric thin films have been deposited on Si substrates using La(acac)₃ and Hf(acac)₄ (acac = 2,4-pentanedionate) mixing sources by low-pressure metal-organic chemical vapor deposition (MOCVD). The structure, thermal stability, and electrical properties of La-doped HfO₂ films have been investigated. Inductive coupled plasma analyses confirm that the La content ranging from 1 to 5 mol% is involved in the films. The films show smaller roughness of ∼0.5 nm and improved thermal stability up to 750 °C. The La-doped HfO₂ films on Pt-coated Si and fused quartz substrates have an intrinsic dielectric constant of ∼28 at 1 MHz and a band gap of 5.6 eV, respectively. X-ray photoelectron spectroscopy analyses reveal that the interfacial layer is Hf-based silicate. The reliable value of equivalent oxide thickness (EOT) around 1.2 nm has been obtained, but with a large leakage current density of 3 A/cm² at V_g = 1V + V_fb. MOCVD-derived La-doped HfO₂ is demonstrated to be a potential high-k gate dielectric film for next generation metal oxide semiconductor field effect transistor applications.     

Structural and dielectric properties of Ru-based gate/Hf-doped Ta2O5 stacks

Hf-doped Ta₂O₅ thin films are studied with respect to their composition, dielectric and electrical properties. The incorporation of Hf is performed by sputtering of a 0.7 nm thick Hf layer on top of Ta₂O₅ and subsequent annealing to stimulate diffusion of Hf into Ta₂O₅ and their intermixing. The elemental in-depth distribution of the films is investigated by the time of flight secondary ion mass spectroscopy (ToF-SIMS), which has revealed that Hf and Ta₂O₅ are intermixed throughout the whole thickness. Two sub-layers exist in all the samples - an upper homogeneous Hf-doped Ta₂O₅ sub-layer and a near interfacial region which is a mixture of Ta- and Si-oxides. The X-ray reflectivity (XRR) analysis shows existence of interfacial layer with a thickness of about 1.9-2 nm, irrespectively of the total thickness of the stacks. Metal-oxide-Si structures with Ru and RuO₂ metal electrodes have been prepared and investigated in terms of dielectric constant, effective work function (EWF) and interfacial layer parameters. The influence of post-metallization annealing steps on these parameters was also studied.     

Effects of N2 and NH3 remote plasma nitridation on the structural and electrical characteristics of the HfO2 gate dielectrics

The remote plasma nitridation (RPN) of an HfO₂ film using N₂ and NH₃ has been investigated comparatively. X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses after post-deposition annealing (PDA) at 700 °C show that a large amount of nitrogen is present in the bulk film as well as in the interfacial layer for the HfO₂ film nitrided with NH₃-RPN. It is also shown that the interfacial layer formed during RPN and PDA is a nitrogen-rich Hf-silicate. The C-V characteristics of an HfO_xN_y gate dielectric nitrided with NH₃-RPN have a smaller equivalent oxide thickness than that nitrided with N₂-RPN in spite of its thicker interfacial layer.     

Low-temperature deposition of stoichiometric HfO2 on silicon: Analysis and quantification of the HfO2/Si interface from electrical and XPS measurements

An understanding of the exact structural makeup of dielectric interface is crucial for development of novel gate materials. In this paper a study of the HfO₂/Si interface created by the low-temperature deposition ultrathin stoichiometric HfO₂ on Si substrates by reactive sputtering is presented. Analysis, quantification and calculation of layer thickness of an HfO₂/Hf-Si-O_x/SiO₂ gate stack dielectrics have been performed, using X-ray photoelectron spectroscopy (XPS) depth profile method, angle resolved XPS and interface modeling by XPS data processing software. The results obtained were found to be in good agreement with the high frequency capacitance-voltage (C-V) measurements. The results suggest a development of a complex three layer dielectric stack, including hafnium dioxide layer, a narrow interface of hafnium silicate and broad region of oxygen diffusion into silicon wafer. The diffusion of oxygen was found particularly detrimental to the electrical properties of the stack, as this oxygen concentration gradient leads to the formation of suboxides of silicon with a lower permittivity, κ.     

Physical and electrical characteristics of a high-k Yb2O3 gate dielectric

High-k ytterbium oxide (Yb₂O₃) gate dielectrics were deposited on Si substrate by reactive sputtering. The structural features of these films after postdeposition annealing treatment were studied by X-ray diffraction and X-ray photoelectron spectroscopy. It is found that the Yb₂O₃ gate dielectrics annealed at 700 °C exhibit a larger capacitance value, a lower frequency dispersion and a smaller hysteresis voltage in C-V curves compared with other annealing temperatures. They also show negligible charge trapping under high constant voltage stress. This phenomenon is mainly attributed to the decrease in the amorphous silica thickness.     

Effect of post-deposition annealing on structural and electrical properties of high-k HoTiO3 gate dielectrics

In this article, the authors developed a high-k HoTiO₃ gate dielectric deposited on Si (1 0 0) through reactive cosputtering. They found that the HoTiO₃ dielectrics annealed at 800 °C exhibited excellent electrical properties such as high capacitance value, small density of interface state, almost no hysteresis voltage, and low leakage current. This phenomenon is attributed to the decrease in intrinsic defect (related to oxygen vacancy) due to a rather well-crystallized HoTiO₃ structure and composition observed by X-ray diffraction, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy, respectively.     

Fabrication and characteristics of high-K HfO2 gate dielectrics on n-germanium

This paper reports that the high-K HfO2 gate dielectrics are fabricated on n-germanium substrates by sputtering Hf on Ge and following by a furnace annealing. The impacts of sputtering ambient, annealing ambient and annealing temperature on the electrical properties of high-K HfO2 gate dielectrics on germanium substrates are investigated. Experimental results indicate that high-K HfO2 gate dielectrics on germanium substrates with good electrical characteristics are obtained, the electrical properties of high-K HfO2 gate dielectrics is strongly correlated with sputtering ambient, annealing ambient and annealing temperature.     

The effect of Si surface nitridation on the interfacial structure and electrical properties of (La2O3)0.5(SiO2)0.5 high-k gate dielectric films

Thermal stability, interfacial structures and electrical properties of amorphous (La₂O₃)_0.5(SiO₂)_0.5 (LSO) films deposited by using pulsed laser deposition (PLD) on Si (1 0 0) and NH₃ nitrided Si (1 0 0) substrates were comparatively investigated. The LSO films keep the amorphous state up to a high annealing temperature of 900 °C. HRTEM observations and XPS analyses showed that the surface nitridation of silicon wafer using NH₃ can result in the formation of the passivation layer, which effectively suppresses the excessive growth of the interfacial layer between LSO film and silicon wafer after high-temperature annealing process. The Pt/LSO/nitrided Si capacitors annealed at high temperature exhibit smaller CET and EOT, a less flatband voltage shift, a negligible hysteresis loop, a smaller equivalent dielectric charge density, and a much lower gate leakage current density as compared with that of the Pt/LSO/Si capacitors without Si surface nitridation.     

Structural, electrical and optical properties of TiO2 doped WO3 thin films

TiO₂ doped WO₃ thin films were deposited onto glass substrates and fluorine doped tin oxide (FTO) coated conducting glass substrates, maintained at 500 °C by pyrolytic decomposition of adequate precursor solution. Equimolar ammonium tungstate ((NH₄)₂WO₄) and titanyl acetyl acetonate (TiAcAc) solutions were mixed together at pH 9 in volume proportions and used as a precursor solution for the deposition of TiO₂ doped WO₃ thin films. Doping concentrations were varied between 4 and 38%. The effect of TiO₂ doping concentration on structural, electrical and optical properties of TiO₂ doped WO₃ thin films were studied. Values of room temperature electrical resistivity, thermoelectric power and band gap energy (E_g) were estimated. The films with 38% TiO₂ doping in WO₃ exhibited lowest resistivity, n-type electrical conductivity and improved electrochromic performance among all the samples. The values of thermoelectric power (TEP) were in the range of 23-56 μV/K and the direct band gap energy varied between 2.72 and 2.86 eV.     

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 5.8 eV. And the crystallization temperature for rapid thermal annealing (20 s) 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.     

Charge trapping at Pt/high-k dielectric (Ta2O5) interface

A detailed analysis of the effects of constant low current injection was done, both in accumulation (J=0.001-0.2 mA cm⁻²) and in inversion (J=0.001-0.04 mA/cm²). The samples under investigation were metal-insulator-silicon structures containing high-k dielectric Ta₂O₅ radio frequency sputtered on p-type Si wafers, with Pt metal gate electrodes. The obtained results were compared with the ones obtained for Al gate samples. This experiment confirms the occurrence of charge trapping in the case of high-work-function Pt as metal. The effect has been attributed to emitting of electrons into the Pt conduction band during which creation of empty traps in the dielectric occurs, which then attract electrons injected in the dielectric. In order to examine the reversibility of the process, successive short runs as well as long runs (up to 10000 s) were performed.     

Y掺杂Al2O3高k栅介质薄膜的制备及性能研究

利用射频反应共溅射方法制备了Y掺杂Al₂O₃电介质薄膜，用掠入射x射线衍射检测了薄膜的结构，用高分辨率扫描电子显微镜(HRSEM)、原子力显微镜(AFM)观察了薄膜断面和表面形貌，用高频C-V和变频C-V及J-V测量了样品的电学特性. 结果表明，Y的掺入使电介质薄膜的介电常数k有了很大提高(8.14—11.8)，并体现出了较好的介电特性. 分析认为：与氧具有较大电负性差的Y离子的加入，增大了薄膜中的金属—氧键(M—O)的强度；同时，Y的加入使Al₂O₃的结构和原子配位发生了改变，从而提高了离子极化对薄膜介电常数的贡献. 退火前后的XRD谱均显示薄膜为非晶态；HRSEM断面和AFM形貌像显示所制备的薄膜非常平整，能够满足器件要求. 关键词： 高k栅介质 掺杂氧化铝 射频反应溅射     

Structural properties and electrical characteristics of high-k Tm2Ti2O7 gate dielectrics

In this article, the structural and electrical characteristics of high-k Tm₂Ti₂O₇ gate dielectrics deposited on Si (1 0 0) by means of reactive cosputtering were reported. The Tm₂Ti₂O₇ dielectrics annealed at 800 °C exhibited excellent electrical properties such as high capacitance value, small density of interface state, almost no hysteresis voltage, and low leakage current. This phenomenon is attributed to a rather well-crystallized Tm₂Ti₂O₇ structure and composition and a smooth surface observed by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy, respectively. This film also shows almost negligible charge trapping under high constant voltage stress.     

Thermal stability of HfO2 nanotube arrays

Thermal stability of highly ordered hafnium oxide (HfO₂) nanotube arrays prepared through an electrochemical anodization method in the presence of ammonium fluoride is investigated in a temperature range of room temperature to 900 °C in flowing argon atmosphere. The formation of the HfO₂ nanotube arrays was monitored by current density transient characteristics during anodization of hafnium metal foil. Morphologies of the as-grown and post-annealed HfO₂ nanotube arrays were analyzed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Although monoclinic HfO₂ is thermally stable up to 2000 K in bulk, the morphology of HfO₂ nanotube arrays degraded at 900 °C. A detailed X-ray photoelectron spectroscopy (XPS) study revealed that the thermal treatment significantly impacted the composition and the chemical environment of the core elements (Hf and O), as well as F content coming from the electrolyte. Possible reasons for the degradation of the nanotube at high temperature were discussed based on XPS study and possible future improvements have also been suggested. Moreover, dielectric measurements were carried out on both the as-grown amorphous film and 500 °C post-annealed crystalline film. This study will help us to understand the temperature impact on the morphology of nanotube arrays, which is important to its further applications at elevated temperatures.     

Annealing Characteristics of ultra—thin high—K HfO2 gate dielectrics

Ultra-thin HfO2 gate-dielectric films were fabricated by ion-beam sputtering a sintered HfO2 target and subsequently annealed at different temperatures and atmospheres.We have studied the capacitance-voltage,current-voltage,and breakdon characteristics of the gate dielectrics.The results show that electrical characteristics of HfO2 gate dielectric are related to the annealing temperature.With increase annealing temperature,the largest value of capacitance decreases,the equivalent oxide thickness increases,the leakage current reduces,and the breakdown voltage decreases.     

Ta和TaN底电极对原子层淀积HfO2介质MIM电性能的影响

以Ta,TaN为衬底,采用原子层淀积方法制备高介电常数HfO₂介质,比较研究了不同衬底电极对金属-绝缘体-金属（MIM）电容的性能影响.结果表明,采用TaN底电极能够获得较高的电容密度和较小的电容电压系数（VCC）,在1MHz下的其电容密度为7.47fF/μm²,VCC为356ppm/V²和493ppm/V,这归因于TaN底电极与HfO₂介质之间良好的界面特性.两种电容在3?V时漏电流为5×10^-8关键词： 高介电常数 MIM电容 2薄膜')" href="#">HfO₂薄膜 电极     

Optical and electrical properties of Y2O3 thin films prepared by ion beam assisted deposition

Y₂O₃ thin films were deposited by ion beam assisted deposition (IBAD) and the effects of fabrication parameters such as substrate temperature and ion energy on the structure, optical and electrical properties of the films were investigated. The results show that the deposited Y₂O₃ films had less optical absorption, larger refractive index, and better film crystallinity with the increase of substrate temperature or ion energy. The as-deposited Y₂O₃ films without ion-beam bombardment had larger relative dielectric constant (?_r) and the ?_r decreased with time even over by 40%, while the ?_r of films prepared with high ion energy had less changes, only less than 3%. Also, with the increase of ion energy, the electrical breakdown strength and the figure of merit increased.     

Morphology and natural wettability properties of sol-gel derived TiO2-SiO2 composite thin films

Previous studies suggest that granular interfaces induce a natural and persistent super-hydrophilicity in TiO₂-SiO₂ composite thin films deposited by sol-gel route. This effect enables to consider self-cleaning applications that do not require a permanent UV exposure, whereas such a permanent exposure is necessary for pure TiO₂ films. In this study, TiO₂-SiO₂ composite thin films have been deposited from a TiO₂ anatase crystalline suspension and different SiO₂ polymeric sols. Wettability studies show that a suitable control of the TiO₂-SiO₂ mixed sol formulations noticeably enhances persistence of the natural super-hydrophilicity in composite films. It is shown that, beside granular interface effects, modifications in the composite film morphologies can noticeably influence wettability properties.     

Electrical properties of La2O3 thin films grown on TiN/Si substrates via atomic layer deposition

The electrical as well as the structural properties of La₂O₃ thin films on TiN substrates were investigated. Amorphous stoichiometric La₂O₃ thin films were grown at 300 °C via atomic layer deposition technique by using lanthanum 2,2,6,6-tetramethyl-3,5-heptanedione [La(TMHD)₃] and H₂O as precursors. Post-annealing of the grown film induced dramatic changes in structural and the electrical properties. Crystalline phases of the La₂O₃ film emerged with the increase of the post-annealing temperature. Metal-insulator-metal (MIM) capacitor was fabricated to measure the electrical properties of the grown film. The dielectric constant of the La₂O₃ thin films increased with annealing temperature to reach the value of 17.3 at 500 °C. The leakage current density of the film post-annealed at 400 °C was estimated to be 2.78 × 10⁻¹⁰ and 2.1 × 10⁻⁸ A/cm² at ±1 V, respectively.