Modeling of the high aspect groove etching in Si in a Cl<Subscript>2</Subscript>/Ar mixture plasma

The model and the results of the modeling of etching deep grooves in Si in Сl₂/Ar plasma as a function of the energy of Cl⁺ and Ar⁺ incident ions (30–250 eV), taking into consideration the redeposition of the reaction products, which are removed from the groove bottom, are represented. The groove profiles with an aspect ratio (depth-to-width groove ratio) below 5 and Si atom yield coefficients per ion as a function of the incident ion energy were in agreement with the reference data. The profile evolution of the deep grooves with an aspect ratio (AR) of up to 10 at different energies of the incident ions is shown. The influence of the redeposition coefficient of the scattered particles and the shape of the mask on the groove profile is considered. The reasons for distorting the profile of the high-aspect grooves during their etching in the Сl₂/Ar plasma are discussed.     

Carbon etching with a high density plasma etcher

Generating suitable passivation on the carbon sidewall is a major challenge facing carbon etching especially for films thicker than 500 nm. Patterning carbon hard mask stacks for sub 90 nm technologies was tested for three different O₂-based chemistries using an inductively coupled plasma etch tool. The results show that the etched carbon profiles are highly dependant upon the O₂ flow and the total time of the etch process. Extended over etch times quite often initiates lateral etching and rapid loss of profile and critical dimension. An HBr/O₂/N₂ chemistry has been shown to provide the best options for profile control and more resistance to profile loss during extended over etching than the other chemistries which were tested during this study.     

Aspect-ratio-independent anisotropic silicon etching in a plasma chemical cyclic process

The conditions of implementation of aspect-ratio-independent etching (ARIE) are given for a two-stage etching/passivation process in an SF₆/C₄F₈ plasma. It is shown experimentally that the ARIE etching is achieved by extension of the stage of passivation and/or reduction of the energy of ions at the stage of etching. These phenomena lead to prolonged removal of the fluorocarbon film, which affects the dependence of the etching rate on the aspect ratio of the groove. A model of cyclic etching is presented that takes into account the aspect dependences of the processes on the groove bottom, namely, Si etching and deposition and removal of the fluorocarbon film. The simulation results correlate satisfactorily with the experimental data. Limitations of implementation of ARIE etching are discussed.     

刻蚀小尺寸CCD接触孔工艺研究

采用CF4,CHF3,Ar三种工艺气体进行小尺寸CCD接触孔刻蚀实验,研究了不同气体配比、不同射频功率对刻蚀速率、选择比、条宽控制、侧壁形貌等参数的影响。通过优化工艺参数,比较刻蚀结果,最终获得了适合于刻蚀CCD小孔的工艺条件。     

Variability study and design considerations of hyperabrupt junction voltage variable capacitors

In the present paper variability analysis of hyperabrupt epitaxial Schottky barrier voltage variable capacitors has been carried out. In particular, it is shown how each electrical parameter of a VVC (viz. cutoff frequency, capacitance ratio, and breakdown voltage) depends on the various physical parameters of the diffused device (viz. total no. of predeposited impurity atoms of the retrograde profile, the drive-in product D₁t₁, background doping, and epitaxial thickness). It is concluded that each electrical parameter has a widely different dependence on the various physical parameters and that for each specific application there are certain key physical parameters which need be tracked more closely during fabrication of the device than others. An optimum design criterion is given which shows that during an actual fabrication of such a device, if the predeposit cycle (for the retrograded hyperabrupt profile) departs from its dc (design centre) value then the later drive-in cycle should also be suitably changed from its dc value to obtain a minimum deviation of a given electrical parameter from its dc value.     

Analysis of groove NRD waveguide bend using the coupled-mode theory

In this paper, the propagation characteristics of the dominant mode in GNRD guide bend are analysed employing the coupled-mode theory. The curves of bending loss vs. The groove depth or width, radius of curvature and frequency are given, which caused by the mode conversion of the operatingLSM ₁₁ ^x mode to the parasiticLSE ₁₁ ^x mode. It is found that the groove depth has a great influence upon the bending loss than the other parameters. According to the theoretical results, appropriate sizes of groove and radius of curvature should be chosen in designing a GNRD bend structure.     

Potentialities of radio-occultation monitoring of the lower ionosphere on satellite-to-satellite paths

The data on the radio-occultation probing of the daytime ionosphere at altitudes of 70–130 km that are measured on satellite-to-satellite paths in subequatorial regions at latitudes of ±30° are analyzed. The dependence of regular variations in the integral electron concentration on the height of the ray line is discussed. It is shown that, at altitudes of 85–110 km, the height profile of electron concentration can be determined from the occultation data. The specific features of the variations in the radio-wave amplitude and in the integral electron concentration that are observed during the probing of sporadic ionospheric formations E _s are analyzed. Data on the frequency of occurrence of the E _s formations, their height, and the thickness of the layered structures are presented. The interfering effect of the ionospheric F region during determination of the parameters of the lower ionosphere is analyzed.     

Formation and Properties of an Oxide Film on an Si3N4Surface under Thermal Oxidation

The formation mechanism, composition, and properties of an oxide film that grows on an Si₃N₄ mask during the LOCOS process are studied experimentally. The effect of the HF etching of the mask oxide film on the profile of the bird's beak is investigated for different etching conditions.     

Attenuation Characteristics of Corrugated Circular Groove Waveguide

When neglecting space harmonics and higher-order slot modes, the attenuation characteristic of corrugated circular groove waveguide has been investigated. It is shown that under certain conditions, the attenuation coefficient of HE ₁₁ mode will be lower than that of dominant TE ⁽¹⁾ ₁₁ mode of circular groove waveguide with same radius.     

Determination of the structural and optical characteristics of Cu2ZnSnS4 semiconductor thin films

The results of X-ray diffraction and optical studies of Cu₂ZnSnS₄ films produced by the flash evaporation of binary sulfide compounds under different technological conditions is reported. It is shown that it is possible to produce Cu₂ZnSnS₄ films, rather perfect in structural and optical respects, by choosing the optimal annealing temperatures at different Ar vapor pressures. The lattice parameters of the compounds are determined. The systematic shift in the photoluminescence bands under variations in the excitation level is established. It is found that the characteristics of the bands depend to a large extent on the annealing temperature, the Ar pressure during thermal treatment, and the resultant stoichiometry composition of the samples. It is shown that Raman studies and luminescence measurements can be used to assess the quality of the synthesized Cu₂ZnSnS₄ films and to obtain data on the energy structure of defects in the band gap.     

Coherent phase equilibria in the Zn-Cd-Te system and liquid-phase epitaxy of elastically strained Zn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Cd<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Te alloy layers

The effect of elastic strains produced in epitaxial Zn _x Cd_{1 − x} Te alloy layers during deposition on the CdTe substrate on the parameters of growth is studied experimentally and theoretically. Phase equilibria between the elastically strained alloy layer, the crystal lattice of which is continuously (coherently) matched to the crystal lattice of the bulk substrate, are described by a coherent state diagram. The processes of mass transfer during the formation of heterostructures on the basis of the above-mentioned alloys and the substrate formed of the initial binary compounds are described in the context of the model of diffusion-limited crystallization. It is shown that such thermodynamic concepts can be used to describe experimental data on the parameters of the process of crystallization of elastically strained alloy layers during the formation of heterojunctions in the system involving the Zn-Cd-Te alloy and the substrate based on the initial binary compound.     

Optimized Cu-Sn Wafer-Level Bonding Using Intermetallic Phase Characterization

The objective of this study is to optimize the Cu/Sn solid–liquid interdiffusion process for wafer-level bonding applications. To optimize the temperature profile of the bonding process, the formation of intermetallic compounds (IMCs) which takes place during the bonding process needs to be well understood and characterized. In this study, a simulation model for the development of IMCs and the unreacted remaining Sn thickness as a function of the bonding temperature profile was developed. With this accurate simulation model, we are able to predict the parameters which are critical for bonding process optimization. The initial characterization focuses on a kinetics model of the Cu₃Sn thickness growth and the amount of Sn thickness that reacts with Cu to form IMCs. As-plated Cu/Sn samples were annealed using different temperatures (150°C to 300°C) and durations (0 min to 320 min). The kinetics model is then extracted from the measured thickness of IMCs of the annealed samples.     

Control of ordering in GaInP and effect on bandgap energy

Ga_xIn_1-x P layers with x ≈ 0.5 have been grown by atmospheric pressure organometallic vapor phase epitaxy on GaAs substrates with 10 micron wide, [110]-oriented grooves produced photolithographically on the surface. The [110] steps and the misorientation produced at the edges of the grooves have been found to have important effects on the formation of the Cu-Pt ordered structure (ordering on {111} planes) in the GaInP layers during growth. In this work, the groove shape is demonstrated to be critically important. For the optimum groove shape, with a maximum angle to the (001) surface of between 10 and 16°, single domains of the (-111) and (1-11) variants of the Cu-Pt ordered structure are formed on the two sides of the groove. Shallow (≤0.25 μm deep) grooves, with maximum angles of <10°, are less effective. Within the large domains on each side of the groove, small domains of the other variant are observed. The boundary between the two domains is seen to wander laterally by a micron or more during growth, due to the change in shape of the groove during growth. For deep (1.5 μm) grooves, with maximum angles to the (001) plane of 35°, only a single variant is formed on each side of the groove. However, the domains are small, dispersed in a disordered matrix. For substrates with deep grooves on a GaAs substrate misoriented by 9° toward the [-110] direction, an interesting and useful pattern is produced. One half of the groove is a single domain which shrinks in size as the growth proceeds. The other half of the groove, where the misorientation is larger, is disordered. Thus, every groove contains large (>1 μm² cross-sectional area and several mm long) regions of highly ordered and completely disordered material separated by no more than a few microns. This allows a direct determination of the effect of ordering on the bandgap of the material using cathodoluminescence (CL) spectroscopy. The 10K photoluminescence (PL) consists of three distinct peaks at 1.94, 1.88, and 1.84 eV. High resolution CL images reveal that the peaks come from different regions of the sample. The high energy peak comes from the disordered material and the low energy peak comes from the large ordered domains. Electron microprobe measurements of the solid composition demonstrate that the shift in emission energy is not due to changes in solid composition. This is the firstdirect verification that ordering causes a reduction in bandgap of any III/V alloy. Decreasing the Ga_0.5In_0.5P growth rate from the normal 2.0 to 0.5 μ/h is found to enhance ordering in layers grown on planar GaAs substrates. Transmission electron diffraction results show that the domain size also increases significantly. For material grown on exactly (001)-oriented substrates, a pronounced [001] streaking of the superlattice spots is observed. This is correlated with the presence of a dense pattern of fine lines lying in the (001) plane in the transmission electron micrographs. The PL of this highly ordered material consists of a single peak that shifts to higher energy by > 110 meV as the excitation intensity is increased by several orders of magnitude.     

A numerical method for predicting intermetallic layer thickness developed during the formation of solder joints

A numerical, method has been developed for calculating the thickness of intermetallic layers formed in substrate-solder systems during the soldering process. As input, the method requires the temperature-time profile for the soldering process and the isothermal liquid state growth rate parameters for the growth of the intermetallic layer. These usually consist of a growth constant, k_o, and an activation energy, Q. The method allows one to predict the thickness of a layer at any time during the soldering process. As such, it can be used in industrial solder processing to enhance the reliability and lifetime of solder joints by allowing control of the thickness of intermetallic layers. The validity of the method is demonstrated for intermetallic growth between copper and 62Sn-36Pb-2Ag solder. The kinetic parameters for the chosen model system were experimentally determined and isothermal intermetallic layer growth between molten solder and copper was found to follow a t^0.25 dependence on time t. The growth rate increased with increasing temperature according to an Arrhenius dependence in the temperature range 187 to 258°C with Q = 7.04 kJ/mol and k_o = 7.75 μm/min^0.25.     

A General Approach to First Order Phase Transitions and the Anomalous Behavior of Coexisting Phases in the Magnetic Case

First order phase transitions for materials with exotic properties are usually believed to happen at fixed values of the intensive parameters (such as pressure, temperature, etc.) characterizing their properties. It is also considered that the extensive properties of the phases (such as entropy, volume, etc.) have discontinuities at the transition point, but that for each phase the intensive parameters remain constant during the transition. These features are a hallmark for systems described by two thermodynamic degrees of freedom. In this work it is shown that first order phase transitions must be understood in the broader framework of thermodynamic systems described by three or more degrees of freedom. This means that the transitions occur along intervals of the intensive parameters, that the properties of the phases coexisting during the transition may show peculiar behaviors characteristic of each system, and that a generalized Clausius–Clapeyron equation must be obeyed. These features for the magnetic case are confirmed, and it is shown that experimental calorimetric data agree well with the magnetic Clausius–Clapeyron equation for MnAs. An estimate for the point in the temperature‐field plane where the first order magnetic transition turns to a second order one is obtained (the critical parameters) for MnAs and Gd₅Ge₂Si₂ compounds. Anomalous behavior of the volumes of the coexisting phases during the magnetic first order transition is measured, and it is shown that the anomalies for the individual phases are hidden in the behavior of the global properties as the volume.     

Investigation of power Trench MOSFETs with retrograde body profile

We present here a power Trench MOSFET (T-MOS) with retrograde body doping profile. The channel length and trench depth are both shortened compared with conventional T-MOS. High energy implantation is used to form retrograde body profile. Electronic parameters of the new structure have been obtained by process and device simulation. The results show that the new structure has much lower specific on-resistance (R_ds,on) because of its shorter channel when compared with conventional T-MOS. As the trench depth is shallowed, the gate charge density Q_g is also reduced.     

Isotropic Plasma Etching of SiO2 Films

The isotropic etching of SiO₂ with an SF₆–O₂ plasma is studied experimentally. It is shown that the key factors in the process are the total and partial pressures of SF₆ and O₂ and the RF power. A smoothed-down edge profile of contact windows is obtained if SF₆ and O₂ are mixed in a ratio of 1 : 10 to 1 : 5. The maximum etch rate is achieved at total pressures of 250 to 450 Pa.     

凹槽型微通道传热与流动性能的数值分析

针对电子器件的散热问题,提出了四种具有对称和等距凹槽的微通道,并通过三维数值模拟,研究了不同雷诺数下凹槽形状及布局对微通道性能的影响。结果表明:在给定的雷诺数范围内,圆形凹槽的传热性能仅次于三角凹槽,而梯形和矩形凹槽的传热性能较差。三角凹槽压降最大,其次是圆形,而梯形和矩形凹槽压降差异较小;同种形状不同布局的凹槽,压降几乎一致,这表明通过改变凹槽布局来提高性能不会产生额外压降损失。综合换热和压降特性,微通道热性能系数先增后减,故三角凹槽在雷诺数为600时获得最优热性能,而在雷诺数为900时等距圆形凹槽的热性能超过三角凹槽。     

A study of the role of HBr and oxygen on the etch selectivity and the post-etch profile in a polysilicon/oxide etch using HBr/O2 based high density plasma for advanced DRAMs

The role of HBr and oxygen on the etch selectivity and the post-etch profile in a polysilicon/oxide etch using HBr/O₂ based high density plasma was studied. HBr/O₂-based polysilicon etch process used in this study seems to be highly selective to the underlying oxide and produce a dielectric fill-friendly post-etch profile depending on the flow rates of HBr and oxygen. When appropriate amounts of HBr and oxygen (∼30 sccm of HBr and ∼3 sccm of oxygen) are present in the etch plasma, brominated silicon oxide seems to be deposited on the original gate oxide and the gate stack sidewall from the reaction of SiBr_x (reaction product during polysilicon etch step) and oxygen during the HBr/O₂-based oxide etch process. The deposited brominated oxide on the thin gate oxide seems to make the HBr/O₂-based plasma etch process extremely selective to the thin gate oxide by protecting the underlying gate oxide. The deposited brominated oxide on the gate stack sidewall seems to prevent the notching by protecting the sidewall during gate stack etching. The etch rate of the brominated oxide seems to be much faster than that of the thermal oxide during the 200:1 diluted HF cleaning. However, the deposited brominated oxide on the thin gate oxide and the gate stack sidewall during the plasma etching survived the following 1 min 200:1 diluted HF cleaning, as was observed in a TEM micrograph (Fig. 2(a)).     

A new technology for manufacturing the dielectric isolation of elements of microelectronic devices by oxidizing grooves in single-crystal silicon

The formation of the dielectric isolation of elements of microelectronic devices by oxidizing grooves in single-crystal silicon is considered. The new technological process makes it possible to shorten the manufacturing cycle and to improve the reliability and parameters of devices. It is shown that this result is attained by substantially shortening the time of oxidation of silicon, suppressing the “bird’s beak” irregularity, and reducing the capacitance of the metal-insulator-semiconductor structure through the etching of grooves with certain geometric parameters in silicon nitride. These parameters are the groove width 0.5–1.5 μm, the ratio of the width to the spacing between the grooves 0.56: 0.44, and the groove depth, which is larger than the width. The results of two-dimensional physical simulation support the advantages of the new technology over the standard process. The simulation was accomplished with the use of the SSUPREM4 program of the Silvaco bundled software.