On the nature of the defect passivation in polycrystalline silicon by hydrogen and oxygen plasma treatments

The effect of hydrogen and oxygen plasmas on the properties of polycrystalline silicon films and thin-film transistors are investigated. The results clearly demonstrate that an oxygen plasma does not passivate grain boundary defects. However, an oxygen plasma treatment at 300 K still improves the electrical properties of thin-film transistors.<>     

Thermoelectric Properties of Polycrystalline Thin Films Under an External Magnetic Field

A theoretical model is proposed to predict the Seebeck coefficient and the electrical conductivity for a polycrystalline thermoelectric (TE) thin film under an external magnetic field. The model considers the distribution of electrons in the microstructure of TE thin-film materials, taking the scattering effect of electrons at the grain boundary as the boundary condition for electron transport in the grain. The transmission coefficient is introduced to describe the probability of electrons passing through the grain boundary potential barrier, while the relationships between the Seebeck coefficient, the electrical conductivity, and the transmission coefficient are studied. Furthermore, the results from the calculations of the Seebeck coefficient, the electric conductivity, and the power factor of TE materials under various applied magnetic fields, transmission coefficients, and grain sizes indicate that the applied external magnetic field has a very significant influence on the TE properties of polycrystalline thin films.     

用MOCVD和快速热处理工艺制备钛酸铋铁电薄膜

采用MOCVD工艺，制备非晶态Bi4Ti3O12薄膜，然后经过快速退火处理，制备高度择优取向的Bi4Ti3O12铁电薄膜，运用X射线衍射术分析薄膜材料的结构，X射线显微分析仪测量薄膜材料的组份，并通过电滞回线的测量，研究快速退火对Bi4Ti3O12薄膜结构和电性能的影响。     

Effects of Ir electrodes on barium strontium titanate thin-filmcapacitors for high-density memory application

Excellent electrical characteristics of RF-sputtered Barium Strontium Titanate (BST) thin-film capacitors with iridium (Ir) electrodes were obtained and the influence of Ir on device properties was investigated. In contrast to conventional Pt-electroded system, BST capacitors with Ir electrodes exhibit higher polarization and slightly higher leakage current. The stronger crystallinity of a thin BST layer (~70 Å) initially grown on Ir substrate is believed to be the cause for higher charge storage density of the Ir-electroded capacitors. However, this higher polarization is accompanied by higher dielectric dispersion (3.12% per decade for Ir versus 1.98% for Pt electrodes). On the other hand, leakage current appears to be dominated by the Schottky barrier formed by Ir-BST and Pt-BST contacts, respectively, at high field. The analysis from temperature-dependent J-V data indicates a lower barrier height for the Ir-BST contact than Pt-BST contact. The slightly higher leakage current density of the BST capacitors with Ir electrodes can thus be attributed to the lower barrier height     

溅射沉积功率对PZT薄膜的组分、结构和性能的影响

用射频(RF)溅射法在镀LaNiO3(LNO)底电极的Si片上沉积PbZr0.52 Ti0.48 O3(PZT)铁电薄膜，沉积过程中基底温度为370℃，然后在大气环境中对沉积的PZT薄膜样品进行快速热退火处理(650℃，5min)．用电感耦合等离子体发射光谱(ICP-AES)测量其组分，X射线衍射(XRD)分析PZT薄膜的结晶结构和取向，扫描电子显微镜(SEM)分析薄膜的表面形貌和微结果，RT66A标准铁电综合测试系统分析Pt／PZT／LNO电容器的铁电与介电特性，结果表明，PZT薄膜的组分、结构和性能都与溅射沉积功率有关．     

Ferroelectrics for nonvolatile RAMs

The structure and operation of ferroelectric thin-film memory capacitors for use in nonvolatile random-access memory applications are described. The search for the ideal ferroelectric material for ferro-electronic memory applications is examined. Possible military and nonmilitary applications of these memories are noted     

应用于FRAM的集成铁电电容的研究

集成铁电电容的制备是铁电存储器的关键工艺之一。该文采用射频(RF)磁控溅射法在Pt/Ti/SiO2/Si制备Pb(Zr,Ti)O3(PZT)薄膜,上下电极Pt采用剥离技术工艺制备,刻蚀PZT薄膜,形成Pt/PZT/Pt/Ti/SiO2/Si集成电容结构,最后高温快速退火。结果表明,这种工艺条件可制备性能良好的铁电电容,符合铁电存储器对铁电电容的要求。     

Analysis of Negative Bias Temperature Instability in Body-Tied Low-Temperature Polycrystalline Silicon Thin-Film Transistors

Negative bias temperature instability (NBTI) degradation mechanism in body-tied low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs) is analyzed by the charge-pumping (CP) technique. The properties of bulk trap states (including interface and grain boundary trap states) are directly characterized from the CP current. The increase of the fixed oxide charges is also extracted, which has not been quantified in previous studies of NBTI degradation in LTPS TFTs. The experimental results confirm that the NBTI degradation in LTPS TFTs is caused by the generation of bulk trap states and oxide trap states.     

Degradation of RuO2 thin films in hydrogen atmosphere at temperatures between 150 and 250 °C

Ruthenium dioxide films were sputtered on silicon dioxide/silicon in thin-film resistors and MOS capacitors structures. Such structures with RuO₂ were exposed to H₂/N₂ ambient with 1% hydrogen content in the temperature range from 150 to 250 °C. Severe morphological degradation of RuO₂ films was observed by scanning electron microscope. By X-ray diffraction analysis it was proved that RuO₂ tends to reduce to Ru in the presence of hydrogen. The pattern of degradation is strongly influenced by the preparation condition: films deposited at room temperature show irregular degradation shape, and films deposited at 300 °C exhibit star-like shape. The shift in capacitance–voltage curves of MOS capacitors with RuO₂ gate electrode after degradation also proves the presence of Ru in the electrode. The failure of the above structures when exposed to hydrogen ambient suggests the need of introduction of hydrogen barrier layers to exploit the good properties of RuO₂.     

Miniature hybrid microwave ICs using a novel thin-film technology

A novel thin-film technology for miniature hybrid microwave ICs is presented. All passive components, such as resistors and capacitors, are fully integrated on ordinary alumina ceramic substrates using the thin-film technology with very high yield. The numbers of parts and wiring processes were significantly reduced. This technology was applied to the fabrication of Ku-band solid-state power amplifiers. This thin-film technology offers the following advantages: (1) a very high yield fabrication process for thin-film capacitors having excellent electrical characteristics in the gigahertz range (ε=3.6, Q=230 at 12 GHz) and reliability; (2) two kinds of thin-film resistors having different temperature coefficients of resistivity (TCRs) and a lift-off process to integrate them with thin-film capacitors; and (3) a matching method using the thin-film capacitor     

Template approaches to growth of oriented oxide heterostructures on SiO2/Si

A template approach to growing highly oriented ferroelectric oxide heterostructures on SiO₂/Si substrates is presented. In this method, a thin “template” of a layered perovskite is used to induce the growth of the subsequent layers in the desired orientation. The efficacy of this “template” approach is illustrated through the example of growth of ferroelectric La-Sr-Co-0/Pb-Zr-Ti-O/La-Sr-Co-O heterostructures on SiO₂Si. Discrete test capacitors fabricated from these heterostructures grown using the template approach exhibit remnant polarization values in the range of 10–15 μ C/cm² and show very little degradation after 10¹¹ bipolar fatigue cycles. In contrast, test capacitors fabricated without the template layer showed very little crystallographic texture and poor ferroelectric properties.     

Quality of ferroelectric capacitors used in tunable microwave filters

The problem of determining the quality of ferroelectric capacitors from measured characteristics of tunable microwave bandpass filters has been solved. The quality of ferroelectric capacitors based on barium-strontium-titanate (BST) thin films, used in four filters tunable over a frequency range of 1.8 to 4.3 GHz, have been determined.     

Thermal-sensitive BST thin film capacitors for dielectric bolometer prepared by RF magnetron sputtering

We have been developing a monolithic microbolometer technology for uncooled infrared focal plane arrays (Uncooled IRFPAs) along the route from fabricating pixels of thin-film dielectric bolometers on micromachined silicon substrates. In the paper, the thermal-sensitive barium strontium titanate (BST) thin film capacitors for that objective prepared by Radio-Frequency Magnetron sputtering have been investigated focusing on the condition of fabrication of BST thin films. Capacitor-Temperature properties of the thermal-sensitive BST thin film capacitors have been measured with impedance analyzer. According to the Capacitor-temperature curves, these indicated that the temperature coefficient of dielectric constant (TCD) within the ambient temperature region highly depended on the Radio-Frequency Magnetron sputtering condition of fabrication of BST thin films. BST thin film capacitors with TCD-value more than 21%/K have been prepared on the optimized condition. That is a good base for preparation of dielectric bolometer mode of uncooled IRFPAs.     

Sol-Gel processing of Nb-doped Pb(Zr,Ti)O3 thin films for ferroelectric memory applications

The ferroelectric properties of Nb-doped PZT thin films prepared by a sol-gel method were evaluated relative to memory device application requirements. Within the range of 0 to 4 mol %, Nb-doping of PZT compositions near the morphotropic phase boundary region (i.e. PZT 53/47) enhanced overall ferroelectric properties by reducing the te-tragonal distortion of the unit cell. A 4 mol % Nb-doped PZT 53/47 thin film (0.26 μm) had a coercivity of 8 V/ μm, a remanence ratio of 0.54, a switchable polarization of 45 μC/cm², and a specific resistivity of 3 x 10⁹ Ω-cm. Nb-doping levels in excess of 5 mol had a detrimental effect on the resulting thin film ferroelectric properties. X-ray diffraction (XRD) analysis of highly doped films showed development of a significant PbO phase accompanied by diffraction line broadening of the perovskite phase. As such, it was postulated that the creation of excessive lead vacancies in the PNZT lattice resulted in PbO accumulation at the grain boundaries which impeded grain growth, and hence, adversely affected ferroelectric switching performance. The fatigue performance of the sol-gel derived thin film capacitor system was a function of switching voltage. At switching fields sufficient to saturate the polarization, the endurance of the thin film capacitor was greater than 10⁹ cycles. Cycling with lower fields reduced endurance values, but in all cases, the switchable polarization decreased linearly with the logarithm of cycles. Nb-doping did not have a significant effect on the fatigue performance.     

CIS gather momentum

The recently developed method of crystal ion slicing (CIS) is rapidly gathering interest and attention as a novel way of successfully obtaining single-crystal thin films. The excellent opto-electrical properties of barium titanate, BaTiO₃, make this ferroelectric crystal eminently suitable for applications such as capacitors, pyroelectric detectors, and nonlinear optics. These films possess high dielectric constants and large pyroelectric and nonlinear coefficients. However, many potential applications for barium titanate require a thin-film form rather than a bulk crystal. Despite substantial advances in deposition technologies for barium titanate thin films, researchers have faced continued difficulty in obtaining high-quality, single-crystal thin films, since they require lattice matching to the growth substrate. CIS looks set to offer researchers a solution.This is a short news story only. Visit www.three-fives.com for the latest advanced semiconductor industry news.     

铁电薄膜SrBi2Ta0．6Nb1．4O9的光疲劳特性研究

用PLD方法在铂金硅衬底制作了高质量的SrB i2Ta0.6Nb1.4O9(SBTN)铁电薄膜样品.研究了SBTN薄膜的电学和光学疲劳特性,分析了其机制.结果显示SBTN铁电薄膜,在电场疲劳下,具有无疲劳特性的优良电学性质;然而,在0.9 V电场下,用200W汞灯疲劳样品,发现光诱导极化疲劳明显,与疲劳前相比,剩余极化下降了51%.这种光诱导剩余极化减小的疲劳,主要机理是光生载流子电畴钉扎.     

Incipient Ferroelectricity in Al‐Doped HfO2 Thin Films

Incipient ferroelectricity is known to occur in perovskites such as SrTiO₃, KTaO₃, and CaTiO₃. For the first time it is shown that the intensively researched HfO₂ thin films (16 nm) also possess ferroelectric properties when aluminium is incorporated into the host lattice. Polarization measurements on Al:HfO₂ based metal–insulator–metal capacitors show an antiferroelectric‐to‐ferroelectric phase transition depending on annealing conditions and aluminium content. Structural investigation of the electrically characterized capacitors by grazing incidence X‐ray diffraction is presented in order to gain further insight on the potential origin of ferroelectricity. The non‐centrosymmetry of the elementary cell, which is essential for ferroelectricity, is assumed to originate from an orthorhombic phase of space group Pbc2₁ stabilized for low Al doping in HfO₂. The ferroelectric properties of the modified HfO₂ thin films yield high potential for various ferroelectric, piezoelectric, and pyroelectric applications. Furthermore, due to the extensive knowledge accumulated by various research groups regarding the HfO₂ dielectric, an immediate relevance of ferroelectric hafnium oxide thin films is anticipated by the authors.     

Electrical,optical, and photoluminescence properties of ZnO films subjected to thermal annealing and treatment in hydrogen plasma

The photoluminescence and optical absorption spectra and electrical properties of ZnO films grown by the metal–organic chemical vapor deposition and hydrothermal techniques, subjected to heat treatments and plasma treatment in a hydrogen atmosphere, are studied. It is shown that the adsorption of oxygen at grain boundaries upon annealing in an oxidizing atmosphere determines the electrical properties of the films. Vacuum annealing improves the electrical properties of the samples after degradation induced by annealing in air. Treatment in hydrogen plasma passivates surface states at the grain boundaries. The intrinsic photoluminescence intensity after plasma treatment is higher in the case of increased amounts of oxygen adsorbed at grain surfaces upon annealing in air. Surface states involving oxygen and hydrogen atoms are responsible for the high-intensity intrinsic photoluminescence band.     

铁电存储器中Pb(Zr,Ti)O_3集成铁电电容的制备

在铁电不挥发存储器 (FERAM)技术中 ,集成铁电电容的制备是关键工艺之一。文中提出一种制备集成铁电电容的改进工艺 :采用 lift-off技术在衬底样品表面淀积铁电电容 Pt/Ti下电极 ,然后用 Sol-Gel方法制备 PZT薄膜。在 PZT薄膜未析晶前 ,先将它加工成电容图形 ,再高温退火成为 PZT铁电薄膜。最后完成铁电电容 Pt上电极。与传统工艺相比 ,改进后的工艺能保持 PZT铁电薄膜与金属上电极之间良好的接触界面。测试结果表明 ,工艺条件的变动不会影响 PZT铁电薄膜的成膜和结构 ,从而可得到性能优良的铁电电容。     

Embedded ferroelectric memory technology with completely encapsulated hydrogen barrier structure

A 0.18-/spl mu/m system LSI embedded ferroelectric memory (FeRAM) operating at a very low voltage has been developed for the first time. The low-voltage operation has been attained by newly developed stacked ferroelectric capacitors completely encapsulated by hydrogen barriers, which enable us to eliminate hydrogen reduction of the ferroelectric thin film during the back end of the line process including FSG, tungsten CVD (W-CVD), and plasma CVD SiN (p-SiN) passivation. A fabricated 1-Mbit one-transistor one-capacitor SrBi/sub 2/(Ta/sub x/Nb/sub 1-x/)/sub 2/O/sub 9/ (SBTN)-based embedded FeRAM operates at a low voltage of 1.1 V and ensures the endurance cycles up to 10/sup 12/ at 85/spl deg/C and the data retention time up to 1000 h at 125/spl deg/C, which is the most promising for mass production of 0.18-/spl mu/m low-power system LSI-embedded FeRAM and beyond.