Some properties of chemically vapor deposited films of AlxOyNz on silicon

Transmission electron microscopy (TEM) studies of films prepared in the AlN-Al₂O₃ pseudobinary system by chemical vapor deposition (as described in a companion paper entitled, “Chemical Vapor Deposition of Al_xO_yN_z Films”) indicates that four different phases can be obtained by altering the NH₃/CO₂ gas ratio and preparation temperature. Films prepared at 900°C yield three polycrystalline phases and an amorphous composition. From zero to 25 at. percent O an AlN phase is observed. Amorphous material is observed from 25 to 47 at. percent O. From 47 to 59 at. percent O an Al_xO_yN_z spinel is observed. At 60 at. percent O (pure Al₂O₃) an alumina phase is observed (KI phase). For 770°C films the AlN phase is observed from zero to 8 at. percent 0; from 8 to 23 at. percent O the zeta-alumina phase is seen; and at 60 at. percent O the KI alumina phase is again observed. For both the 770 and 900°C films, the grain size of the AlN phase was found to decrease with increasing oxygen content. Direct current-voltage, dielectric breakdown and capacitance-voltage measurements were performed on the 900 and 770°C films with a variety of film compositions. For pure AlN and Al₂O₃, current-voltage and dielectric breakdown measurements correlate with the grain size observed by TEM. A maximum in breakdown field was observed for 900°C films at the composition which yielded minimum grain size of the AlN phase. A similar maximum is observed for the zeta-Al₂O₃ phase of the 770°C films. Positive flatband voltages and hysteresis of the capacitance-voltage trace was observed for most samples. Dielectric constants greater than 8 have been observed for some compositions. Several compositions appear to be attractive candidates for charge storage layers in MIOS devices.     

固体电介质微波介电参数的耦合器测量技术

论述了微带分支线耦合器非破坏性测量固体电介质复介电常数的方法,阐明了3dB分支线耦合器用于介电常数测量的原理,提出的分支线耦合器的输出与耦合端口各连接一段终端开路的微带线,待测物放在其中的一条线上。待测物的介电常数可通过测量两端口的散射参数的幅度进行计算。运用提出的方法,在2.45GHz下测量了特氟龙、聚丙烯等固体电介质的复介电常数,其结果与文献相吻合。     

分层媒质复介电常数测量的一种方法

本文给出一种测量分层媒质复介电常数的方法,经过多次测量复反射系数并建立恰当的目标函数,采用遗传算法求解这一优化问题可得到分层媒质的参数。测量结果表明,对于层数校少的媒质,在各分层厚度未知的民政部下仍可测得各分层的复介电常数,同时测得分层厚度。     

ULSI用氟化类金刚石薄膜的研究

以CF4和CH4为源气体,用射频等离子体增强化学气相沉积法,制备了氟化类金刚石(F-DLC)薄膜。采用FTIR仪、XPS对样品进行了测试、分析。结果表明,在薄膜内主要含有C—Fx(x=1,2,3)、C—C、C—H2、C—H3等以及不饱和C==C化学键;薄膜的εr为2.07~2.65。εr与膜内F的相对浓度有关,随着沉积功率的增大,膜内F、H的含量均降低,εr升高。     

Degenerate cadmium oxide films for electronic devices

Highly conducting and transparent cadmium oxide films have been deposited on Corning 7059 glass substrates by ion-beam sputtering and by spray pyrolysis. The electrical and optical properties of CdO films prepared by the two techniques are similar. Typical films of 0.5 μm thickness have electrical resistivities of (2–5) × 10^-3 ohm-cm, carrier concentrations of approximately 10²⁰ cm^-3, and an optical transmission of higher than 70% in the wavelength range of 600–900 nm. An optical bandgap of 2.4–2.42 eV was deduced from the optical transmission data.     

Porous network of samarium sulfide thin films for supercapacitive application

In the present letter, a novel aqueous chemical method is employed to prepare thin film of Sm₂S₃ material containing porous network of interconnected nanoparticles for supercapacitive application. The orthorhombic phase formation of Sm₂S₃ film is concluded from X–ray diffraction study. The chemical states of samarium and sulfur are determined using X–ray photoelectron spectroscopy study. The pseudocapacitive behavior of Sm₂S₃ showed a maximum specific capacitance of 248 F g⁻¹ in 1.5 M LiClO₄ electrolyte prepared in propylene carbonate electrolyte. The nature of charge and discharge curves confirmed pseudocapacitive behavior of film electrode. The highest power and energy densities of 15.6 kWh kg⁻¹ and 54.6 Wh kg⁻¹, respectively are obtained. An electrochemical stability of 94% is retained after 1500 cycles.     

外延CeO2高k栅介质层的结构及介电性能

利用脉冲激光沉积两步生长法在Si(111)衬底上制备了厚度为10～40nm的外延CeO<,2>薄膜,构建了Pt/CeO<,2>/Si MOS结构.研究了CeO<,2>薄膜的界面及介电性能,实验发现,界面处存在的电荷对MOS结构C-V特性的测量有较大影响,采用两步生长法制备的外延CeO<,2>薄膜在保持较大介电常数的同时...     

An ac microcalorimeter for measuring specific heat of thin films

Microcalorimeter based on suspended SiO₂ membrane structures has been designed and fabricated. The geometry of suspension arms is optimized by ANSYS simulation to ensure that it provides maximum thermal isolation between the membrane structure and the supporting substrate. The microcalorimeter is intended to be a sample carrier onto which other thin films can be deposited for thermal property measurement. An ac modulation method has been used to measure the specific heat of aluminum thin film with thickness from 13.5 to 370 nm. The measurements demonstrated clearly the dependence of specific heat on thin film thickness.     

Thermoreflectance temperature measurements for optically emitting devices

This work examines the difficulties associated with using optical techniques to measure temperature when the device itself emits a significant level of light over a wide spectrum, making it a challenge to separate the useful measurement signature from the device light emission. The specific situation considered here is that of using a thermoreflectance (TR) thermography approach to characterize the thermal behavior of semiconductor laser devices. A lowpass filter was placed in the optical path to minimize the primary laser irradiation on the TR imaging and then the TR response of the region of interest was determined over a wide range of visible light wavelengths to locate the maximum response. TR measurements performed at the optimal light wavelength successfully provided a submicron-resolution temperature map of the active area of sample lasers.     

低k介质多孔SiO2干凝胶薄膜的温度效应研究

采用正硅酸乙酯(TEOS)作为Si源,利用溶胶–凝胶旋涂法制备了多孔SiO2干凝胶薄膜,测试分析了200,300和400℃退火后样品的不同特性。研究了退火温度对多孔SiO2干凝胶低k薄膜的化学性质、物理性质和电学性能的影响。结果表明在400℃的退火温度下所制备的薄膜具有最佳性能:其厚度和折射率均达到最小值,分别为156 nm和1.31;孔隙度和均方根粗糙度均达到最大值,分别为33%和2.01 mm,并获得最低的相对介电常数(k=2)和最小的泄漏电流。     

Low-Pressure chemical vapour deposition of tantalum pentoxide films for ulsi devices using tantalum pentaethoxide as precursor

A laminar flow low-pressure chemical vapour deposition (LPCVD) system (LAM Integrity^TM) has been used to deposit tantalum pentoxide (Ta₂O₅) from Ta(OEt)₅ films in the presence of oxygen (O₂) at 470 °C at a typical deposition rate of 4 nm min^?1. Uniformities of <1.5% (SD 1σ) over a 150 mm silicon substrate were obtained. The layers were annealed under different conditions. It was discovered that the films did not change their stoichiometry as determined by Rutherford backscattering (RBS). The as-deposited films were amorphous but became crystalline (β-Ta₂O₅) at temperatures > 700 °C. The transmission electron microscopy (TEM) results on crystallisation behaviour were supported by X-ray diffraction data. The electrical properties of the Ta₂O₅ films have been characterised using MIS (metal/insulator/silicon) capacitor structures. Leakage values of <10^?6 A cm^?2 at 6 MV cm^?1 equivalent applied electric field and breakdown strengths of >7 MV cm^?1 at 1.6 μA were obtained for annealed layers. Compound dielectric constants (native silicon oxide thickness of about 2.5 nm plus Ta₂O₅ of various thicknesses) between 14 and >30 have been measured. The electrical properties reveal the potential use of Ta₂O₅ as a storage capacitor dielectric in 64 and 256 Mbit DRAM (dynamic random access memory) devices.     

混响室\

在功率平衡法的网络化公式应用中, 精确预知腔内装载物的耦合截面积是关键, 这通常依赖于混响室的实验测定.文中使用平面波角谱概念和蒙特卡罗方法来数值模拟混响室中的电磁环境, 在此基础上, 首次应用基于互易定理的快速全波分析方法提取了理想混响室内靠近理想导电地平面的多导体传输线的平均耦合截面积, 验证了方法的正确性, 并计算了单根裸线传输线、带包层传输线、双绞传输线、传输线附近有导体挡板以及多导体传输线端口的平均耦合截面积.该方法具有计算精度高、仿真速度快、适用范围广的特点.     

The annealing effect for structural, optical and electrical properties of dysprosium–manganese oxide films grown on Si substrate

Samples of (Dy–Mn) oxide thin films were prepared on quartz and Si(p) substrates for optical and electrical investigations. These samples were annealed at different temperatures and characterised by UV–VIS absorption spectroscopy, X-ray fluorescence (XRF) and X-ray diffraction (XRD). The XRF spectrum was used to determine the weight fraction ratio of Mn to Dy in the prepared samples. The XRD shows that Dy oxide and Mn oxide prevent each other to crystallise alone or making a solid solution even at 600 °C. However, compound of DyMnO₃ was formed through the solid-state reaction for T > 800 °C. The ac-conductance and capacitance were studied, as a function of frequency and gate voltage and the fixed and interface charge densities were determined. It was found that the “correlated barrier hopping” CBH model controls the frequency dependence of the conductivity, while the Kramers–Kronig (KK) relations explain the frequency dependence of the capacitance. The parameters of CBH model were determined and show that the ac-conduction in crystalline (Dy–Mn) oxide is realised by bipolaron mechanism, where the barrier height of hopping is equal to the bandgap determined the UV–VIS absorption spectroscopy.     

Annealing of lead zirconate titanate (65/35) thin films for ultra large scale integration storage dielectric applications: Phase transformation and electrical characteristics

Thin film capacitors of Lead Zirconate Titanate (PZT, 400 nm) of Zr/Ti ratio 65/35, deposited by reactive dc-magnetron sputtering, with low leakage current and high charge storge density(’Q _c ) for use as capacitor dielectrics in ultra-large scale integration dynamic random access memory (ULSI DRAM) cells have been fabricated and studied. The equivalent SiO₂ thickness for the optimized film is 5.3å for the fresh film and 9.1å after 10¹⁰ unipolar stress cycles (0 to -3 V). The leakage current density is 1.32 × 10^-7A/cm² for 3 V operation which is equivalent to an effective SiO₂ field of 55 MV/ cm. X-ray diffraction analysis reveals that as-deposited films (T _dep . = 200? C) contain no detectable perovskite phase. Post-deposition annealing is therefore essential, and critical to the fabrication of high quality capacitors for memory applications. The pyrochlore-to-perovskite phase transformation, the evolution of the microstructure, composition and the presence of different phases in the film have been studied as a function of annealing conditions. There is a purely outward radial growth of the interphase boundary, resulting in the increase in the curved surface area of the cylindrical perovskite aggregates throughout the film thickness with increasing thermal budget. The increase in perovskite phase content with annealing time at a constant annealing temperature indicates that a diffusional phase transformation from the pyrochlore to cubic perovskite phase above the Curie temperature occurs as a first step in the formation of the ferroelectric perovskite phase. The variation of two important dielectric properties, charge storage density and leakage current density is reported as a function of the annealing time and temperature. Furthermore, the variation of the charge storage density due to unipolar dynamic electrical stress is studied. The total area under the large-frequency C-V curve (which is the total reversible polarization) increases under unipolar dynamic stress (0 to -3 V) after 10¹⁰ stress cycles. The degradation in charge storage density is found to be primarily due to an increase in remanent polarization caused by the shift in the hysteresis loop as a result of the reduction in the internal bias field under the influence of the unipolar dynamic stress.     

Recent progress of (Ba,Sr)TiO<Subscript>3</Subscript> thin films for tunable microwave devices

The (Ba_1−xSr_x)TiO₃ (BST) ferroelectric thin films exhibit outstanding dielectric properties, even at high frequencies (>1 GHz), and large, electric-field dielectric tunability. This feature makes them suitable for developing a new class of tunable microwave devices. The dielectric properties and dielectric tuning property of BST thin films are closely related to the film compositions, substrate types, and post-deposition process. The successful implementation of BST films as high-frequency dielectrics in electrically tunable microwave devices requires a detailed understanding of both their processing and material properties. This paper will review the recent progress of BST thin films as active dielectrics for tunable microwave devices. The technical aspects of BST thin films, such as processing methods, post-annealing process, film compositions, film stress, oxygen defects, and interfacial structures between film and substrate, are briefly reviewed and discussed with specific samples from the recent literature. The major issues requiring additional investigations to improve the dielectric properties of BST thin films for tunable microwave applications are also discussed.     

ZnSe/ITO thin films:candidate for CdTe solar cell window layer

The crystal structure, electrical and optical properties of ZnSe thin films deposited on an In₂O₃:Sn (ITO) substrate are evaluated for their suitability as the window layer of CdTe thin film solar cells. ZnSe thin films of 80, 90, and 100 nm thickness were deposited by a physical vapor deposition method on Indium tin oxide coated glass substrates. The lattice parameters are increased to 5.834 Å when the film thickness was 100 nm, which is close to that of CdS. The crystallite size is decreased with the increase of film thickness. The optical transmission analysis shows that the energy gap for the sample with the highest thickness has also increased and is very close to 2.7 eV. The photo decay is also studied as a function of ZnSe film thickness.     

InP基转移电子器件接触性能的优化研究

The effect of the annealing time and annealing temperature on Ni/Ge/Au electrode contacts deposited on the n-type InP contact layer has been studied using a circular transmission line model. The minimum specific contact resistance of 3.210 7 cm2was achieved on the low-doped n-type InP contact layer with a 40 s anneal at 425 ℃. In order to improve the ohmic contact and reduce the difficulty in the fabrication of the high doped InP epi-layer, the doping concentration in the InP contact layer was chosen to be 51018cm 3in the fabrication of transferred electronic devices. Excellent differential negative resistance properties were obtained by an electron beam evaporating the Ni/Ge/Au/Ge/Ni/Au composite electrode on an InP epi-layer with a 60 s anneal at 380 ℃.     

Electrodeposition and characterization of ZnO thin films using sodium thiosulfate as an additive for photovoltaic solar cells

Zinc oxide thin films have been grown by electrodeposition technique onto Cu and ITO-coated glass substrates from an aqueous zinc nitrate solution with addition of sodium thiosulfate at 90℃.The effects of sodium thiosulfate on the electrochemical deposition of ZnO were investigated by cyclic voltammetry and chronoamperometry techniques.Deposited films were obtained at -0:60 V vs.SCE and characterized by XRD,SEM,FTIR, optical,photoelectrochemical and electrical measurements.Thickness of the deposited film was measured to be 357 nm.X-ray diffraction results indicated that the synthesized ZnO has a pure hexagonal wurtzite structure with a marked preferential orientation along (002) plane.FTIR results confirmed the presence of ZnO films at peak 558 cm^-1.SEM images showed uniform,compact morphology without any cracks and films composed of large flower-like ZnO agglomerates with star-shape.Optical properties of ZnO reveal a high optical transmission (>80%) and high absorption coefficient (α>105 cm^-1)in visible region.The optical energy band gap was found to be 3.28 eV.Photoelectrochemical measurements indicated that the ZnO films had n-type semiconductor conduction.Electrical properties of ZnO films showed a low electrical resistivity of 6.54 Ω·cm,carrier concentration of -1.3×10¹⁷cm^-3 and mobility of 7.35 cm²V^-1s^-1.