Structure and electrical conductivity of polycrystalline silicon films grown by molecularbeam deposition accompanied by low-energy ion bombardment of the growth surface

This paper discusses how the structure and electrical conductivity of polycrystalline silicon films grown by molecular-beam deposition are affected by the growth conditions. It shows that the films can be improved by applying to the substrate a voltage in the range 50–300 V, negative with respect to the silicon source. Such films also have higher conductivity. The results are explained in terms of bombardment of the growing film by dopant ions. Fiz. Tekh. Poluprovodn. 34, 291–295 (March 1997)     

二氧化锡溅射工艺研究

SnO2是最早使用也是目前使用最广泛的一种气敏材料，使用该材料设计制作的气敏传感器具有许多优点。在简要介绍溅射镀膜的成膜过程和特点的基础上，着重介绍了SnO2膜的制备流程，分析了功率和温度变化对成膜质量的影响。     

二氧化锡溅射工艺研究

SnO2 是最早使用也是目前使用最广泛的一种气敏材料 ,使用该材料设计制作的气敏传感器具有许多优点。在简要介绍溅射镀膜的成膜过程和特点的基础上 ,着重介绍了SnO2 膜的制备流程 ,分析了功率和温度变化对成膜质量的影响     

Simulation of formation of nanostructures during sputtering of the surface by ion bombardment

The results of the investigation of a spatially nonlocal model of surface erosion by the ion bombardment are presented. It is shown that the equilibrium states of the surface in the scope of the model are the plane and a terrace-like profile. Critical values of the bombardment angle and surface diffusion, at which the equilibrium states are lost to perturbations in the form of traveling waves, are determined. The obtained results allow us to explain the main form of the surface topography formed during ion sputtering of the surface, and to determine their parameters, the existence region, and the sequence of appearance.     

离子束溅射氧化钽薄膜光学特性的热处理效应

主要研究了离子束溅射制备的氧化钽薄膜在大气氛围下热处理对其光学特性的影响规律。实验中热处理温度范围的选择为150~550℃,间隔为200℃。研究中分别采用介电常数的Cody-Lorentz色散模型和振子模型对氧化钽薄膜的能带特性（1~4 eV）和红外波段（400~4 000 cm-1）的微结构振动特性进行了表征。研究结果表明,在150℃和350℃之间出现热处理温度转折点,即热处理温度高于此值时消光系数增加。Urbach能量的变化与消光系数趋势相同,而禁带宽度的变化与消光系数恰好相反。通过红外微结构振动特性分析,薄膜中仍存在亚氧化物的化学计量缺陷。     

Gate oxide reliability improvement related to dry local oxidation of silicon

Gate oxide reliability can be effectively improved by using dry field oxidation instead of the conventional wet one. The obtained improvement is suggested to occur because of a better oxide quality in the active region border due to the absence of the characteristic defects induced by wet local oxidation.     

Gate oxide breakdown in FET devices and circuits: From nanoscale physics to system-level reliability

Gate oxide breakdown has been historically considered a catastrophic failure mechanism for CMOS technology. With CMOS downscaling the mid 1990’s have seen the emergence of soft breakdown as a possible failure mode. At the same time the notion started appearing that the first breakdown event does not necessarily spell the immediate failure of the entire CMOS application. Relaxation of the CMOS circuit reliability criteria, however, requires a thorough understanding of the impact of the breakdown path on FET behavior. This cannot be consistently achieved without the microscopic perspective of the physical effects occurring in the affected device. Future CMOS applications will be able to sustain many soft breakdown events, which will be treated as additional parametric variation. Tools ranging from simulation to circuit monitoring will assure reliability at the functional level.     

Enhancing crystallization of silicon nanocrystal embedded in silicon-rich oxide by ion beam-assisted sputtering

This study examined the material and optical properties of Si nanocrystals (NCs) embedded in Si-rich oxide (SRO) films prepared through ion beam-assisted sputtering (IBAS). Transmission electron microscopy and grazing-incidence X-ray diffraction revealed that IBAS improved the formation of the Si NCs in the SRO films. The size and density of Si NCs were predominantly controlled by IBAS with varying anode voltage. The photoluminescence levels of the SRO films were enhanced, which was associated with the quantum confinement effect of the Si NCs. The benefits of an Ar ion beam used on the SRO films are discussed in this paper. The results indicate that IBAS is a promising approach for the development of highly efficient Si-based optoelectronic devices.     

Improvement of gate oxide reliability for tantalum-gate MOS devicesusing xenon plasma sputtering technology

The effects of ion species in the sputtering deposition process on gate oxide reliability have been experimentally investigated. The use of xenon (Xe) plasma instead of argon (Ar) plasma in tantalum (Ta) film sputtering deposition for gate electrode formation makes it possible to improve the gate oxide reliability. The Xe plasma process exhibits 1.5 times higher breakdown field and five times higher 50%-charge-to-breakdown (Q_BD). In the Ta sputtering deposition process on gate oxide, the physical bombardment of energetic inert-gas ion causes the generation of hole trap sites in gate oxide, resulting in the lower gate oxide reliability. A simplified model providing a better understanding of the empirical relation between the gate oxide damage and the inert-gas ion bombardment energy in the gate-Ta sputtering deposition process is also presented     

Exploration of heavy ion irradiation effects on gate oxide reliability in power MOSFETs

Heavy ion irradiation effects on gate oxide reliability in power MOSFETs were explored. Devices were exposed to heavy ion fluences and LETs simulating exposure in spacecraft at bias levels not expected to cause catastrophic failure. Time dependent dielectric breakdown measurements and charge separation techniques resulted in no detectable changes. The gate voltage at which oxide breakdown occurs and the gate I–V curves suggest subtle changes in device characteristics that can be detected at high gate biases. However, there is no indication that heavy ion exposure results in a significant reduction in gate oxide reliability.     

Pulsed DC magnetron sputtering deposition of crystalline photocatalytic titania coatings at elevated process pressures

The use of elevated process pressures is described in the magnetron sputter deposition of titanium dioxide photocatalytic coatings to enable the direct low-temperature formation of the most photoactive titania crystal phase; anatase. Most other works on this subject deal with relatively low ‘conventional’ pressures (0.1–0.5 Pa). However, the present work describes pulsed DC reactive magnetron sputtering deposition of titanium dioxide thin films at process pressures in the range 2–5 Pa in a purpose-built sputtering rig. The influence of the other deposition conditions, such as pulse frequency and duty cycle, is also discussed. Additionally, a series of N-doped titania coatings was produced by using air as the reactive gas. The morphological and compositional properties of the coatings were studied using energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Wettability of the films was studied through measurement of water contact angles under UV light irradiation. Photocatalytic properties of the samples were assessed through the degradation of two model pollutants, methylene blue and stearic acid, under UV light irradiation. The results showed that elevated process pressures (4 Pa and above) allow the direct deposition of anatase titania films, without additional heat treatment, while amorphous titania tends to form at lower process pressures.     

Effects of the sputtering deposition process of metal gate electrode on the gate dielectric characteristics

Effects of the N₂-introduced reactive sputtering deposition of metal gate electrodes on the gate leakage current and the dielectric reliability of the W/WN_x and W/TiN metal gate MOS capacitors are investigated. The gate dielectric characteristics of W gate MOS capacitor are degraded during the sputtering deposition of the gate electrode. However, the sputtering process-induced degradation of the dielectric characteristics is improved by increasing N₂ flow ratio during the deposition of WN_x gate electrode. This improvement is considered to be due to the termination of the dangling bonds in the surface-damaged layer in the gate dielectric by the surface nitridation. The nitridation of 1.5 at.% is found to effectively improve both gate leakage characteristics and dielectric reliability of the W/WN_x gate MOS capacitor to a level comparable to those of the poly-Si gate. The characteristics of W/WN_x gate MOS transistors are also improved by the surface nitridation through the decrease of the gate leakage current. However, the surface nitridation enhances the electron trapping probability under substrate injection, which results in the lower activation energy of CVS–Q_bd of metal gate MOS capacitors.     

Memory characteristics of MOSFETs with densely stacked silicon nanocrystal Layers in the gate oxide synthesized by low-energy ion beam

Densely stacked silicon nanocrystal layers embedded in the gate oxide of MOSFETs are synthesized with Si ion implantation into an SiO/sub 2/ layer at an implantation energy of 2 keV. In this letter, the memory characteristics of MOSFETs with 7-nm tunnel oxide and 20-nm control oxide at various temperatures have been investigated. A threshold voltage window of /spl sim/ 0.5 V is achieved under write/erase (W/E) voltages of +12 V/-12 V for 1 ms. The devices exhibit good endurance up to 10/sup 5/ W/E cycles even at a high operation temperature of 150/spl deg/C. They also have good retention characteristics with an extrapolated ten-year memory window of /spl sim/ 0.3 V at 100/spl deg/C.     

Molding compound trends in a denser packaging world: qualificationtests and reliability concerns

This work benchmarks the current reliability tests used by the electronics industry, examines those tests that affect and are affected by molding compounds, discusses the relevance of accelerated testing, and addresses the major reliability issues facing current molding compound development efforts. Six compound-related reliability concerns were selected: moldability; package stresses; package cracking; halogen-induced intermetallic growth at bond pads; moisture-induced corrosion; and interfacial delamination. Causes of each failure type are surveyed and remedies are recommended     

Influence of the deposition conditions on the properties of titanium oxide produced by r.f. magnetron sputtering

This work refers to the electro-optical and structural characteristics of titanium oxide (TiO_x) thin films produced by radio frequency (r.f.) magnetron sputtering that present promising performances for gate dielectric applications, alone or in mixed tandem structures, such as with Al_yO_z films, taking advantage of its high dielectric constant. Films produced with a O₂/Ar ratio between 0.1 and 0.15 present an improved stochiometry and density where the resistivity overcomes 10¹¹ Ω cm and the fixed charge density decreases below 10¹² cm⁻². The deposition pressure influences greatly the growth rate that seems to be a determinant factor dictating the films properties.     

The impact of F contamination induced by the process on the gate oxide reliability

The effects of F contaminants introduced by the CVD WSi₂ deposition and diffused to the gate oxide interfaces by the thermal treatment performed during the process have been analyzed. High field stresses showed a degradation of the quality of the oxides contaminated by fluorine, but decreasing the stress field below a critical value of 10.5 MV/cm no more effect of fluorine on the gate oxide reliability was detectable.     

Pressure-induced formation of thermal donor centers in silicon after oxygen ion bombardment

This paper discusses the generation of thermal donor centers in silicon by oxygen ion implantation in the temperature range 350 to 550 °C. These donors are distributed almost uniformly over the entire thickness of the silicon crystals and well outside the region of direct penetration of the ions. It is established that implantation of Czochralski-grown silicon with oxygen ions followed by annealing accelerates the introduction of these donors into the silicon, and that application of hydrostatic pressure further accelerates the process of donor-center formation. The data indicate that this accelerated introduction of donors is associated with diffusion of radiation-induced defects from the implanted layer into the crystal bulk, and that the diffusion coefficients of these defects are 1×10⁻⁷ cm²/s or larger. Fiz. Tekh. Poluprovodn. 33, 1153–1157 (October 1999)     

Statistical lifetime reliability optimization considering joint effect of process variation and aging

Aging effect degrades circuit performance in the runtime, interacts with fabrication-induced device parameter variation, and thus posing significant impact on circuit lifetime reliability. In this work, a statistical circuit optimization flow is proposed to ensure lifetime reliability of the manufactured chip in the presence of process variation and aging effects. It exploits a variation-aware gate-level statistical aging degradation model to characterize circuit lifetime reliability, identifies a set of worst duty cycles on the inputs of statistically critical gates to estimate the worst delay degradations on these gates. Based on the delay degradation information, statistical gate sizing is performed which enables the manufactured chip to satisfy lifetime reliability constraint in term of low area overhead.     

离子束溅射参数与Ta2O5薄膜特性的关联性

离子束溅射技术是制备Ta2O5薄膜的重要技术之一。采用正交试验设计方法,系统研究了Ta2O5薄膜的折射率、折射率非均匀性、消光系数、沉积速率和应力与工艺参数（基板温度、离子束压、离子束流和氧气流量）之间的关联性。通过使用分光光度计和椭圆偏振仪测量Ta2O5薄膜透过率光谱和反射椭偏特性,再利用全光谱反演计算的方法获得薄膜的折射率、折射率非均匀性、消光系数和物理厚度。Ta2O5薄膜的应力通过测量基底镀膜前后的表面变形量计算得到。实验结果表明:基板温度是影响Ta2O5薄膜特性的共性关键要素,其他工艺参数的选择与需求的薄膜特性相关。研究结果对于制备不同应用的Ta2O5薄膜制备工艺参数选择具有指导意义。