Dielectric properties of SrZrO3 thin films prepared by pulsed laser deposition

SrZrO₃ (SZO) thin films have been prepared on Pt-coated silicon substrates and directly on Si substrates by pulsed laser deposition (PLD) using a ZrSrO target at a substrate temperature of 400 °C in 20 Pa oxygen ambient. X-ray –2 scans showed that the as-deposited films remain amorphous at a substrate temperature of 400 °C. The dielectric constant of SZO has been determined to be in the range 24–27 for the Pt/SZO/Pt structure. Capacitance–voltage (C–V) characteristics of a metal-oxide-semiconductor (MOS) structure for SZO films deposited in 20 Pa oxygen ambient and 20 Pa nitrogen ambient (SZON) indicated that incorporation of nitrogen during the substrate heating and film deposition can suppress the formation of an interfacial SiO₂ layer, and the SZON films have a lower equivalent oxide thickness (EOT) than that of the SZO films. However, the leakage current of the SZON films is larger than that of the SZO films. The EOT is about 1.2 nm for a 5-nm SZON film deposited at 400 °C. The leakage-current characteristics of as-deposited SZON films and SZON films post-annealed in oxygen ambient by rapid thermal annealing (RTA) have been studied comparatively. The films post-annealed with RTA have a lower leakage current than the as-deposited SZON films. Optical transmittance measurements showed that the band gap of the films is about 5.7 eV. It is proposed that SrZrO₃ films prepared at 400 °C are potential materials for alternative high-k gate-dielectric applications. PACS 77.84.Bw; 77.84.-s; 77.55.+f     

Comparative study of pulsed laser deposited HfO2 and Hf–aluminate films for high-k gate dielectric applications

The thermal stability and the electrical properties of HfO₂ and Hf–aluminate films prepared by the pulsed laser deposition technique have been investigated by X-ray diffraction, differential thermal analysis, capacitance–voltage correlation, leakage-current measurements and high-resolution transmission electron microscopy observation, respectively. A crystallization transformation from HfO₂ amorphous phase to polycrystalline monoclinic structure occurs at about 500 °C. In contrast, the amorphous structure of Hf–aluminate films remains stable at higher temperatures up to 900 °C. Rapid thermal annealing at 1000 °C for 3 min leads to a phase separation in Hf–aluminate films. Tetragonal HfO₂(111) is predominant, and Al₂O₃ separates from Hf–aluminate and is still in the amorphous state. The dielectric constant of amorphous HfO₂ and Hf–aluminate films was determined to be about 26 and 16.6, respectively, by measuring a Pt/dielectric film/Pt capacitor structure. A very small equivalent oxide thickness (EOT) value of 0.74 nm for a 3-nm physical thickness Hf–aluminate film on a n-Si substrate with a leakage current of 0.17 A/cm² at 1-V gate voltage was obtained. The interface at Hf–aluminate/Si is atomically sharp, while a thick interface layer exists between the HfO₂ film and the Si substrate, which makes it difficult to obtain an EOT of less than 1 nm. PACS 77.55.+f; 81.15.Fg; 73.40.Qv     

A novel Sr_{3}Pb_{6}Ce_{2}Ti_{12}O_{36} ferroelectric thin film grown by pulsed laser ablation

Complex perovskite oxide ferroelectric thin films are of great technological interest because of their high dielectric constant and large tunability. In this paper, we report the structural and electrical properties of Sr \(_{3}\) Pb \(_{6}\) Ce \(_{2}\) Ti \(_{12}\) O \(_{36}\) (SPCTO) thin films grown by pulsed laser deposition. The role of oxygen pressure and substrate temperature on the microstructure, dielectric properties and leakage current mechanism of SPCTO thin films was investigated. Strong oxygen partial pressure dependence on the microcrystalline properties and leakage current conduction mechanism was observed. Both Raman spectra and C-V characteristics show a ferroelectric phase rather than paraelectric phase for the deposited thin films. Investigations on the leakage current showed that SPCTO thin films deposited at different oxygen pressure have different dominant conduction mechanism at various electric fields. The low field conduction mechanism is governed by Ohmic and space charge limited conduction mechanisms, whereas at high fields, the conduction process is dominated by Schottky emission mechanism. The dielectric constant as well as the tunability is found to increase with increase in the crystallite size.     

Dielectric response of K(Ta,Nb)O3 thin films

The dielectric response of K(Nb,Ta)O₃ films grown on (001) MgAl₂O₄ (100) by pulsed laser deposition from a mosaic target of KTa_0.63Nb_0.37O₃ and KNO₃ has been examined. In particular, the effects of growth temperature (650–800 °C), growth pressure (1–100 mTorr O₂), and annealing conditions on the tunability, dielectric constant, and dielectric losses in interdigitated capacitor device structures fabricated with these films are described. Annealing treatments lead to a reduction in the loss tangents for most of the films considered. Figure of merit calculations indicate that the best dielectric response (tunability=37%, tan =0.022) is achieved for films grown at 750 °C in an oxygen pressure of 100 mTorr and then annealing at 1000 °C for 2 h in air.     

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.     

Pulsed laser deposition of zirconium silicate thin films as candidate gate dielectrics

Thin films of zirconium silicate Zr_xSi_1-xO₂ (with x=0.69), a material that has been suggested as a possible high-k dielectric, are deposited on silicon wafers by pulsed laser deposition (PLD) under different deposition and post-annealing conditions. The morphology and electrical properties of these films are characterized. It is shown that the films remain amorphous after an ex situ rapid thermal annealing (RTA) at temperatures as high as 800 °C. For the 6 nm thick film deposited at 300 °C in an O₂ ambient with a N₂ ambient post-RTA at 500 °C for 5 min, the equivalent oxide thickness (EOT) is 1.9 nm, as evaluated from capacitance-voltage (C–V) measurements. The samples prepared with the N₂ ambient post-RTA show a slightly higher leakage current than that for samples annealed in the O₂ ambient. For the films deposited in N₂, the smallest EOT of 1.1 nm is obtained, and the films have fair electrical properties in spite of the high interface state density and relatively higher leakage. PACS 77.55.+f; 81.15.Fg; 81.40.Ef     

Thermal stability and electrical properties of Zr silicate films for high-k gate-dielectric applications, as prepared by pulsed laser deposition

Zirconium silicate films with high thermal stability and good electrical properties have been prepared on n-Si(100) substrates and commercially available Pt-coated Si substrates to fabricate metal–insulator–metal (MIM) structures by the pulsed laser deposition (PLD) technique using a Zr_0.69Si_0.31O_2- ceramic target. Rapid thermal annealing (RTA) in N₂ was performed. X-ray diffraction indicated that the films annealed at 800 °C remained amorphous. Differential thermal analysis revealed that amorphous Zr silicate crystallized at 830 °C. X-ray photoelectron spectroscopy showed that RTA annealing of Zr silicate films at 900 °C led to phase separation. The dielectric constant has been determined to be about 18.6 at 1 MHz by measuring the Pt/Zr silicate/Pt MIM structure. The equivalent oxide thicknesses (EOTs) and the leakage-current densities of films with 6-nm physical thickness deposited in O₂ and N₂ ambient were investigated. An EOT of 1.65 nm and a leakage current of 31.4 mA/cm² at 1-V gate voltage for the films prepared in N₂ and RTA annealed in N₂ at 800 °C were obtained. An amorphous Zr-rich Zr silicate film fabricated by PLD looks to be a promising candidate for future high-k gate-dielectric applications. PACS 77.55.+f; 81.15.Fg; 73.40.Qv     

Hafnium oxide thin films deposited from a filtered cathodic vacuum arc

The electrical and structural characteristics of hafnium oxide thin films reactively deposited from a filtered cathodic vacuum arc have been investigated. X-ray photoelectron spectroscopy was used to determine the deposition conditions (Ar/O₂ ratio) which produced stoichiometric HfO₂ films. Cross-sectional transmission electron microscopy showed that the micro-structure of the films was highly disordered with electron-diffraction analysis providing evidence for the presence of sub-nano-metre crystallites of the monoclinic HfO₂ (P2₁/c) phase. Further evidence for the presence of this phase was provided by measuring the O k-edge using electron energy loss spectroscopy and comparing it with calculations performed using FEFF8.2, a multiple scattering code. Surface imaging revealed that local film damage occurred in films deposited with substrate bias voltages exceeding −200 V. The current-leakage characteristics of the HfO₂ films deposited with a bias of approximately −100 V suggest that device grade HfO₂ films can be produced from a filtered cathodic vacuum arc.     

Effect of annealing temperature on microstructure, optical and electrical properties of sputtered Ba0.9Sr0.1TiO3 thin films

Ba_0.9Sr_0.1TiO₃ (BST) thin films were deposited on fused quartz and Pt/TiN/Si₃N₄/Si substrates by radio frequency magnetron sputtering technique. Microstructure and chemical bonding states of the BST films annealed at 700 °C were characterized by field emission scanning electron microscopy, X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and Raman spectrum. Optical constants including refractive indices, extinction coefficients and bandgap energies of the as-deposited BST film and the BST films annealed at 650, 700 and 750 °C, respectively, were determined from transmittance spectra by envelope method and Tauc relation. Dielectric constant and remnant polarization for the BST films increase with increasing annealing temperature. Leakage current density-applied voltage (J–V) data indicate that the dominant conduction mechanism for all the BST capacitors is the interface-controlled Schottky emission under the conditions of 14 V < V < 30 V and −30 V < V < −14 V. Furthermore, the inequipotential J–V characteristics for the BST films annealed at various temperatures are mainly attributed to the combined effects of the different thermal histories, relaxed stresses and strains, and varied Schottky barrier heights in the BST/Pt and Pt/BST interfaces.     

Effect of gamma irradiation on the optical properties of nano-crystalline InP thin films

Thin films of InP were prepared onto glass and quartz substrates using laser ablation technique. Some of the prepared films were irradiated using a ⁶⁰Co γ -ray source irradiation with a total dose of 100 kGy at room temperature. The as deposited and irradiated films were identified by scanning electron microscopy, SEM and X-ray diffraction, XRD. The SEM images have shown a nano-flower like structure for the as deposited films and influenced by the irradiation dose. The Optical characterizations of the as deposited and irradiated InP films were studied using spectrophotometric measurements of transmittance T(λ) and reflectance, R(λ) at normal incidence of light in the spectral range from 200 nm to 2500 nm. The refractive index, n, and the absorption index, k values were calculated using a modified computer program based on minimizing (ΔT)² and (ΔR)² simultaneously, within the desired accuracy. Analysis of the dispersion of the refractive index in the range 900 ≤ λ ≤ 2500 was discussed in terms of the single oscillator model. The optical parameters, such as the dispersion energy, E_d, the oscillator energy, E_o, the high frequency dielectric constant, _∞ and the lattice dielectric constant, _L were evaluated for the as deposited and irradiated films. The allowed optical transitions were found to be direct for the as deposited and irradiated films with energy gaps of 1.35 eV and 1.54 eV, respectively.     

O2掺杂对SiCOH低k薄膜结构与电学性能的影响

以十甲基环五硅氧烷(D5)和氧气(O₂)作为反应气体，采用电子回旋共振等离子体化学气相沉积(ECR-CVD)方法制备了k＝2.62的SiCOH薄膜.研究了O₂掺杂对薄膜结构与电学性能的影响.结果表明，采用O₂掺杂可以在保持较低介电常数的前提下极大地降低薄膜的漏电流，提高薄膜的绝缘性能，这与薄膜中Si-O立体鼠笼、Si-OH结构含量的提高有关. 关键词： SiCOH薄膜 2掺杂')" href="#">O₂掺杂 介电性能 键结构     

Pulsed laser deposition of aluminate YAlO3 and LaAlO3 thin films for alternative gate dielectric applications

Amorphous aluminate YAlO₃ (YAO) thin films on n-type silicon wafers as gate dielectric layers of metal–oxide–semiconductor devices are prepared by pulsed laser deposition. As a comparison, amorphous aluminate LaAlO₃ (LAO) thin films are also prepared. The structural and electrical characterization shows that the as-prepared YAO films remain amorphous until 900 °C and the dielectric constant is ∼14. The measured leakage current of less than 10^-3 A/cm² at a bias of V_G=1.0 V for ∼40-nm-thick YAO and LAO films obeys the Fowler–Nordheim tunneling mechanism. It is revealed that the electrical property can be significantly affected by the oxygen pressure during deposition and post rapid thermal annealing, which may change the fixed negative charge density at the gate interface. PACS 77.55.+f; 81.15.Fg; 81.40.Ef     

Nitridation of organo-silicate glass: A self-limiting process for PVD Ta1+xN/Ta barrier formation

Interfacial reactions of sputter-deposited Ta with a low dielectric constant Si–O–C–H material (SiCOH), and with surface-nitrided SiCOH (N-SiCOH) were investigated using X-ray photoelectron spectroscopy (XPS). The studies were carried out in a system containing a processing chamber attached to an XPS analysis chamber so that sample transport between deposition and analysis environments occurred under ultrahigh vacuum (UHV) conditions. Ta sputter deposition on unmodified SiCOH yielded an interfacial phase 3 nm thick composed of Ta oxide/carbide (Ta–O–C), which is known to interact only weakly with Cu. Bombardment of the vicinal SiCOH surface by 500 eV Ar⁺ in the presence of NH₃ resulted in carbon depletion and the self-limiting nitridation of the surface, with N attachment primarily at Si sites. Subsequent Ta sputter deposition yielded reduced Ta oxide and carbide formation, and formation of a Ta-rich nitride layer of 10 Å average thickness. Subsequent deposition resulted in metallic Ta formation.     

Electrical property of HfOxNy-HfO2-HfOxNy sandwich-stack films

The effects of HfO_xN_y on the electrical property of HfO_xN_y-HfO₂-HfO_xN_y sandwich-stack (signed as SS) films were investigated. Excellent electrical performances were achieved in SS films, with a high dielectric constant of 16 and a low leakage current of ∼2 × 10⁻⁸ A/cm² at 1 MV/cm. Schottky (SK) emission and Frenkel-Poole (PF) emission are found to be the dominant mechanisms for the current conduction behavior. After a long time stress, the flat-band voltage shift in the SS film is much smaller than that in a pure HfO_xN_y film indicating fewer charge traps existed in the SS film. Based on the experiments, the new SS structure is more favorable for the improvement of electrical performances than a pure HfO_xN_y or HfO₂ structure.     

Femtosecond dynamics of dielectric films in the pre-ablation regime

The ultra-fast dynamics of dielectric oxide materials excited close to the laser-damage threshold is studied by performing transient reflection and transmission pump–probe measurements on TiO₂, Ta₂O₅, and HfO₂ films. The time-dependent dielectric constant is retrieved taking into account standing-wave effects of both pump and probe. A sub-100-fs transient is followed by a 1-ps transient, during which a sign reversal from negative to positive is observed in the real part of the induced change in the dielectric function, indicating the formation of deep defect states, possibly self-trapped excitons. PACS  78.47.+p; 61.80.-x; 72.20.Jv     

Synthesis,characterization and radiation damage studies of high-k dielectric (HfO2) films for MOS device applications

The current trend in miniaturization of metal oxide semiconductor devices needs high-k dielectric materials as gate dielectrics. Among all the high-k dielectric materials, HfO₂ enticed the most attention, and it has already been introduced as a new gate dielectric by the semiconductor industry. High dielectric constant (HfO₂) films (10?nm) were deposited on Si substrates using the e-beam evaporation technique. These samples were characterized by various structural and electrical characterization techniques. Rutherford backscattering spectrometry, X-ray reflectivity, and energy-dispersive X-ray analysis measurements were performed to determine the thickness and stoichiometry of these films. The results obtained from various measurements are found to be consistent with each other. These samples were further characterized by I–V (leakage current) and C–V measurements after depositing suitable metal contacts. A significant decrease in the leakage current and the corresponding increase in device capacitance are observed when these samples were annealed in oxygen atmosphere. Furthermore, we have studied the influence of gamma irradiation on the electrical properties of these films as a function of the irradiation dose. The observed increase in the leakage current accompanied by changes in various other parameters, such as accumulation capacitance, inversion capacitance, flat band voltage, mid-gap voltage, etc., indicates the presence of various types of defects in irradiated samples.     

Pulsed laser deposited ZrAlON films for high-k gate dielectric applications

ZrAlON films were fabricated using the reactive ablation of a ceramic ZrAlO target in N₂ ambient by pulsed laser deposition (PLD) technique. ZrAlON films were deposited directly on n-Si(100) substrates and Pt coated silicon substrates, respectively, at 500 °C in a 20 Pa N₂ ambient, and rapid thermal annealed (RTA) in N₂ ambient at 1000 °C for 1 min. Cross sectional high-resolution transmission electron microscopy (HRTEM) images clearly show that the ZrAlON/Si interface is atomically sharp without an interfacial layer, and the films are completely amorphous. The electron diffraction pattern of TEM also indicates the amorphous structure of the RTA ZrAlON film. X-ray photoelectron spectroscopy (XPS) measurement was performed to confirm the effective incorporation of nitrogen with a content of about 6 at. %, and to reveal the N–O bonding in ZrAlON films. The dielectric constant of amorphous ZrAlON was determined to be about 18.2 which is more than 16.8 for ZrAlO by measuring the Pt/films/Pt capacitors. Capacitance–voltage (C–V) measurements show that a small equivalent oxide thickness (EOT) of 1.03 nm for 4 nm ZrAlON film on the n-Si substrate with a leakage current of 28.7 mA/cm² at 1 V gate voltage was obtained. PACS 77.55.+f; 81.15.Fg; 73.40.Qv     

Preparation of fluorocarbon thin film deposited by soft X-ray ablation and its electrical characteristics and thermal stability

Fluorocarbon films were deposited by soft X-ray ablation of polytetrafluoroethylene (PTFE) and characterized as low-dielectric-constant interlayer dielectrics. Very rapid deposition of such films at approximately 1500 nm/min could be achieved at room temperature. Fourier-transform infrared spectroscopy (FT-IR) measurement results suggest that the films deposited are primarily formed as one-dimensional chains of (-CF₂-)_n which are partially cross-linked. The cross-link density increases with increasing deposition temperature, which improves the thermal stability. However, the dielectric constant of the films increased abruptly above 300 °C. The dielectric constant and leakage current at 1.0 MV/cm of the film deposited at room temperature were approximately 2.1 and 2.0×10⁻⁹ A/cm², respectively.     

Pulsed laser deposition of Er:BaTiO3 for planar waveguides

Laser radiation is used for the deposition of dielectric erbium doped BaTiO₃ thin films for photonic applications. Pulsed laser deposition with KrF excimer laser radiation (wavelength 248 nm, pulse duration 20 ns) is used to grow dense, transparent, amorphous, poly-crystalline and single crystalline erbium doped BaTiO₃ thin films. Visible emission due to up-conversion luminescence (wavelength 528 nm and 548 nm) under excitation with diode laser radiation at a wavelength of 970–985 nm is investigated as a function of the erbium concentration of 1–20 mol% and structural film properties. PACS 81.15.Fg; 42.55.Wd; 68.55; 78.55.Hx