Anodic Oxidation of Si in Oxygen/Chlorine Plasma

By adding a few percent of chlorine to oxygen plasma, the anodization rate of Si was enhanced; for example, the rate was doubled for oxygen containing 3-percent chlorine. With a chlorine concentration of 1.5 percent, the density of trap states at the Si-SiO/sub 2/ interface was reduced from 7 X 10/sup 11//cm/sup 2//spl dot/eV to 5 X 10/sup 11//cm/sup 2/ /spl dot/eV at the midgap of Si; after annealing at 800/spl deg/C in argon for 60 min, it was reduced to 8 X 10/sup 10//cm/sup 2//spl dot/eV, and did not return to the original value after heating the specimen to 800/spl deg/C. The density and capture cross section of traps in plasma-anodic oxide were also measured using the constant-current avalanche-injection method. The number of electron traps with small cross sections in plasma-anodic SiO/sub 2/ films was reduced by annealing them at 800/spl deg/C in argon, but SiO/sub 2/ films which were anodized in oxygen/chlorine plasma showed an increase of trap density under the same annealing condition.     

Simulating the chlorine plasma etching profile of high-aspect-ratio trenches in Si

We simulate etching trenches in Si with a high (over 15) aspect ratio, i.e., the ratio between the trench depth and width in Cl₂ plasma in wide ranges of the ratio between the flows of Cl atoms and Cl⁺ ions (3–300) and ion energies (50–250 eV). We demonstrate that the trenches with a high aspect (HA) ratio (~20) and almost vertical walls can be formed at the maximum energies of E _i = 250 eV and R = 300. At the lower values of these parameters, etching an HA-ratio trench is accompanied by its narrowing, curvature, or bending. We discuss the origin of the HA-trench bending effect at small R values and a high energy of the incident ions.     

Selective anodic oxidation of silicon in oxygen plasma

Plasma-enhanced oxidation process at low temperature was studied for the selective oxidation of silicon. Silicon dioxide films as thick as 1 µm were routinely obtained at the substrate temperature of 600 °C. The oxidation was found to proceed through the motion of both oxygen and silicon ions and/or their vacancies under the electric field applied across the oxide. Aluminum oxide film was used as a mask for selective oxidation and very small lateral oxidation under the mask was found. Furthermore, no generation of dislocations was found at mask edges. The properties of the oxide were found comparable to those of thermally grown oxide. Electron-spin resonance measurements revealed one kind of defects in the oxide, which was attributed to the interface states by comparing with results obtained by measuring the capacitance-voltage characteristics. The morphology of the Si-SiO2interface, studied by transmission electron microscopy was not significantly different from that of thermally grown SiO2-Si systems. Impurity redistribution in the substrate was not observed.     

Adhesion of NCF to oxidized Si wafers after oxygen plasma treatment

The effect of oxygen plasma treatment on the adhesion between nonconductive film (NCF) and oxidized Si was investigated. Oxidized Si wafers were treated with oxygen plasma for 5 min and then rinsed in de-ionized water (DIW). The water contact angle was measured by means of the sessile drop technique and the surface roughness was measured by means of atomic force microscopy. The adhesion of the NCF to the oxidized Si wafer was evaluated by means of a single-lap shear test after bonding at 150°C for 5 s. Oxygen plasma treatment decreased the water contact angle. The roughness of the oxidized Si wafer decreased when oxygen plasma treatment was applied alone, but was increased when both oxygen plasma treatment and DIW rinse were applied. Similarly, the shear strength decreased when oxygen plasma treatment was applied alone, but the adhesion of NCF increased when both oxygen plasma treatment and DIW rinse were applied. The increased surface roughness of the oxidized Si wafer played an important role in increasing the adhesion between the NCF and the oxidized Si wafer. The shear strength further increased after post-heat treatment at 170°C for 1 hr or at 280°C for 15 s. Low shear strength observed before post-heat treatment was ascribed to incomplete NCF curing. Differences observed in the adhesion strength between two types of NCF were attributed to differences in their curing degrees and their degrees of surface coverage of the oxidized Si substrates.     

Anodic oxidation of a-Si:H films

It is shown that thick native oxide layers (up to 2500 ?) can be grown on a-Si:H films at room temperature by anodic oxidation. Ellipsometric measurements indicate uniformity of the oxide layer with a refractive index of 1.46. The voltage growth rate is found to be 5.3 ?/V.     

大气状态下AFM阳极氧化加工Si的研究

Si纳米氧化线是构筑基于Si的纳米器件的基础。通过AFM针尖诱导阳极氧化加工的n型Si(100)的实验得到凸出的n型Si(100)氧化物高度和偏置电压成线性关系,与针尖扫描速度成负对数关系,并在前人的基础上深化了AFM针尖诱导氧化加工的机理和理论模型,得到了合适的加工条件为偏压8 V和扫描速度1μm/s。     

InP and Si metal-oxide semiconductor structures fabricated using oxygen plasma assisted wafer bonding

In this paper, InP metal-oxide-semiconductor (MOS) structures are fabricated by transferring thermally grown SiO₂ to InP from oxidized Si wafers using oxygen plasma assisted wafer bonding followed by annealing at either 125°C or at 400°C. Well-defined accumulation and inversion regions in recorded capacitance-voltage (C-V) curves were obtained. The long-term stability was comparable to what has been previously reported. The structures exhibited high breakdown fields, equivalent to thermally grown SiO₂-Si MOS structures. The transferring process was also used to fabricate bonded Si MOS structures.     

阳极氧化工艺及成膜机理

铝基板经阳极氧化后形成一层耐磨、耐腐蚀、电绝缘的氧化膜。铝合金成分、微观组织结构、氧化前处理等因素都会对阳极氧化产生影响。本文基于阳极氧化工艺流程,结合工艺参数,探讨了氧化膜的形成和生长过程,进而分析了影响氧化膜性能的深层原因,对生产有一定的参考意义。     

Physical processes in duplexer discharges in chlorine and oxygen

The high-power properties of the input-window discharge of a TR tube are analyzed in terms of the transmission and reflection coefficients of a thin plasma slab terminated by a low-intensity secondary gap discharge. Computer solutions were obtained for equations expressing the TR properties of arc loss, leakage power, recovery time, and phase shift as functions of collision frequency and electron density. Measurements of arc loss and leakage power in a chlorine discharge yielded values of electron density of 1 × 10¹⁴to 6 × 10¹³electrons/cm³over a 0.5- to 80-torr pressure range. The recovery period atX-band corresponds to a decaying plasma in which electron density decays from 10¹⁴to 10¹²electrons/cm³. This decay occurs in less than 0.5 µs for chlorine discharges. An analysis of the physical mechanisms controlling fast recovery times in electronegative gases shows that the two most important physical mechanisms are recombination of electrons and ions in the early recovery period and electron attachment in the late recovery period. Experimental data is presented for the recovery of chlorine and oxygen over a pressure range of 0.5 to 80 torr. An analysis of measured values of attachment frequency in oxygen indicates that the electron temperature in the recovery period, which is early in the afterglow, was in the 1.4- to 1.2-eV range.     

Electrical characterization of high-k gate dielectrics fabricated using plasma oxidation and post-deposition annealing of a Hf/SiO2/Si structure

High permittivity (high-k) gate dielectrics were fabricated using the plasma oxidation of Hf metal/SiO₂/Si followed by the post-deposition annealing (PDA), which induced a solid-phase reaction between HfO_x and SiO₂. The oxidation time and PDA temperature affected the equivalent oxide thickness (EOT) and the leakage current density of the high-k dielectric films. The interfacial structure of the high-k dielectric film/Si was transformed from HfO_x/SiO₂/Si to HfSi_xO_y/Si after the PDA, which led to a reduction in EOT to 1.15 nm due to a decrease in the thickness of SiO₂. These high-k dielectric film structures were investigated by X-ray photoelectron spectroscopy. The leakage current density of high-k dielectric film was approximately four orders of magnitude lower than that of SiO₂.     

小型单重态氧发生器中氯气利用率的测量

在一台为化学氧碘激光器而研制的小型射流式单重态氧发生器上建立了一套氯气利用率测量系统;从实验和理论两方面详细研究了光源线宽、气流温度、水气含量、气流组分对紫外吸光光度法测量氯气利用率的影响;测量结果和误差分析表明,在良好设计的实验中,氯气利用率的相对测量误差约为2%,主要来源于光电倍增管(PMT)的噪音.最后,提出了减少测量误差和扩大氯气利用率测量量程的方法.我们的工作将有助于更加准确地和精确地测量化学氧碘激光系统中的单重态氧发生器的氯气利用率.     

重掺硅衬底材料中氧沉淀研究进展

对国内外在重掺硅中氧沉淀方面的研究做了综合阐述,对氧沉淀研究现状和存在问题进行了讨论,同时就热处理,掺杂剂对氧沉淀的影响做了浅析,使人们对重掺硅衬底中氧沉淀这一领域有更深的认识.     

Oxygen segregation and Ge diffusion in annealed oxygen ion-implanted relaxed SiGe/Si heterostructures

Relaxed SiGe-on-insulator (SGOI) is a suitable material to fabricate strained Si structures. Separation-by-implantation-of-oxygen (SIMOX) is a competing method to synthesize SGOI materials. In this work, SiGe/Si samples were implanted with 3×10¹⁷ cm⁻² oxygen ions at 60 kV, followed by high-temperature annealing. Oxygen segregation and Ge diffusion during the annealing process were investigated using Rutherford backscattering spectroscopy/channeling (RBS/C), high-resolution x-ray diffraction (HRXRD), and high-resolution transmission electron microscopy (HRTEM). Our results show that the sample structure strongly depends on the thermal history and Ge diffuses mainly at the beginning stage of the high-temperature process. The process can be improved by introducing an annealing step at a medium temperature before high-temperature annealing, and sharper interfaces and good crystal quality can be obtained. Our results indicate that the SIMOX process for silicon-on-insulator (SOI) fabrication can be adopted to produce SGOI.     

External circuit system effects on chlorine plasma instabilities

The effects of the external circuit on plasma instabilities in an inductive plasma source are investigated. The instabilities are found to be asymmetric with respect to the circuit input impedance. A simplified model of the antenna-plasma coupling provides an explanation of the asymmetry.     

Control of chlorine inductively coupled plasma using optical-emission spectroscopy

Magneto-resistive random access memory (MRAM) technology is recognized as one of the next key advances in computer memory. To create MRAM, various metals are successively laid down by sputtering to create stacks, which are then etched into suitable patterns. Each layer requires a different process and maximum plasma energy to efficiently etch the metal while maintaining the stack at the lowest possible temperature to preserve magnetic properties. Computer control is necessary for fast response as the reaction progresses through different layers. This control system design enables high-speed control of the energy available in the plasma using high-speed spectrometers without extensive calculation of extraneous state variables.     

Microwave plasma oxidation of silicon

The stringent requirements of the next generation of VLSI will force the temperature of IC processing to a lower regime. One of the most important areas is the formation of gate and field dielectrics. Dopant re-distribution, stacking fault and dislocation generation as well as bird's-beak problems can be eliminated or minimized by low temperature oxygen microwave plasma anodization. This paper describes our investigation in the low pressure, low temperature oxidation of silicon using this technique. Oxidation rate dependence on anodization current, time, orientation, plasma power and temperature are measured. Properties of the plasma oxide was characteristized by thickness uniformity, refractive index, infrared absorption and C-V measurement. Discussion on the species responsible for the oxidation, the transport mechanisms and the factors that could affect the kinetics of the growth are presented. We conclude that the technique looks promising for the future.     

氧化铝、氧化钛多孔膜的阳极氧化制备与微结构比较

采用阳极氧化法分别获得了纳米结构的氧化铝多孔膜和氧化钛多孔膜。对多孔膜的微结构、形貌、晶相等进行了检测与分析;系统研究了阳极氧化电压对纳米孔孔径的影响,分析了金属箔片退火、两步阳极氧化对纳米孔有序度和孔径均匀性的影响;对阳极氧化过程中出现的新颖的上下双层和内外双层多孔膜形貌进行了分析和讨论。初步获得了纳米多孔膜的形成机理,阳极氧化铝、氧化钛纳米多孔膜在制备、微结构等方面存在许多共同点。     

Fabrication of Si nanostructures by controlled sidewall oxidation

We have fabricated Si dots and wires with widths as small as 2 nm by thermally oxidizing an etched mesa in a controlled manner. Electrical contacts are deposited on the Si nanostructures so that their current-voltage characteristics may be measured. For dots fabricated from wafers with a n-i-n doping profile we observe alinear dependence of the room temperature conductance on the device diameter, which we explain in terms of the profile of the Si/SiO₂ interface. We are able to extract the width of the unoxidized Si from this dependence and find that the I(V) of devices with active widths less than 10 nm measured at 77 K is non-linear. I(V) measurements are also presented for bar shaped devices fabricated from pn material which clearly show that rectification occurs, even for active widths less than 10 nm.