Formation of buried oxide layers by high dose implantation of oxygen ions in silicon

Buried implanted oxide layers have been formed by high dose implantation of oxygen ions of the order of 1 × l0¹⁸−2 in silicon. The effects of dose at a given energy, and energy for a given peak concentration, on the distribution profile of oxygen have been studied. An approximately Gaussian distribution is observed at doses contributing less than the stoichiometric requirement of oxygen for the formation of silicon dioxide. A saturation in the oxygen peak concentration is reached when the stoichiometric requirement is exceeded. The excess implanted oxygen results in a broadening of the stoichiometric implanted oxide layer. A consequent reduction in the interface damage is observed. Other parameters being equal, at higher substrate temperatures the interface damage is decreased. For a given peak concentration, the implanted oxide is buried more deeply with increasing ion energy. Infra-red absorption characteristics of the implanted oxide are almost identical to those of thermal oxide layers grown in a dry oxygen ambient. The implanted oxide layer exhibits also an extremely high resistivity compared to the substrate material. Department of Electronics, University of Kent,Canterbury,Kent,U.K.     

Composition analysis of oxidized buried SiC layers in silicon from EFTEM images

Energy filter transmission election microscopy (EFTEM) is used to investigate the composition of a Si/SiO_x/SiC multilayer structure formed by ion-beam synthesis. The implanted dose is used as a standard for the quantification of the elemental maps. The carbon redistribution upon the oxidation of SiC is monitored.     

光注入型SiC BCCD的可行性分析

An SiC optoinjected charge-coupled device with buried channels(BCCD)is designed for the detection of ultraviolet light(UV),and its feasibility is studied by means of Silvaco numerical simulation software.Charge storageandtransfercharacteristicsoftheBCCDcanbeconformedbysimulationresults.Theburiedchanneldesign is a key point to realize the high sensitivity of the device.The channel mobility of electrons in the 6H-SiC BCCD can be changed from 47 to 200 cm2/(V s)when the channel is replaced from surface to the subsurface of 0.2 m.With the optimized device parameters,the density of stored electrons can reach up to 1.062 1011cm2and the number of stored electrons is up to 1.826 108for UV light with wavelengths from 200 to 380 nm and an intensity of 0.1 W/cm2under a driving voltage of 15 V at room temperature.     

Formation and control of boron buried layers in silicon using anexcimer laser

Buried layers have been shown to enhance performance of Si MOSFETs in the deep submicrometer regime. Epitaxial growth methods such as atomic layer doping or ion implantation are currently used for the formation of such doping profiles. In this work, we propose an alternative approach, using a XeCl (λ=308 mn) pulsed excimer laser, for the fabrication of pulse-shaped B profiles in Si. This process affords simplicity, versatility, and independent control over the depth, width, and the height of the B buried layer     

MicroRaman study of crystallographic defects in SiC crystals

Crystallographic defects are one of the main troubles for the use of SiC crystals in high power/high temperature electronics. The understanding of these defects is essential for the optimization of the crystal growth process. MicroRaman spectroscopy appears as a very promising technique for studying these defects, since it provides local (1 μm²) information about crystal order, stress, polytype identification and doping, which are important aspects for the characterization of the defects. We present herein a Raman study of a few of these defects: planar inclusions, bulk inclusions and micropipes in 4H and 6H crystals, either semiinsulating and n-type. The main results are referred to the presence of inclusions of different polytypes, Si segregation at the micropipe hollow and impurity gettering effects around inclusions in n-type material.     

Properties of buried SiC layers produced by carbon ion implantation in (100) bulk silicon and silicon-on-sapphire

Buried layers of SiC were formed in (100) single-crystal bulk silicon and silicon-on-sapphire by ion implantation of 125–180 keV, (0.56-1.00) × 10¹⁸ C/cm² at 30–40 μA/ cm² into samples held at 450-650° C. The as-implanted and 950° C annealed samples were characterized by differential infra-red absorbance and reflectance, Rutherford backscattering and channeling spectrometry, x-ray diffraction, four-point probe measurements, Dektak profilometry, I-V measurements, spreading resistance measurements and secondary ion mass spectrometry. Work done while affiliated with Rockwell International Corporation, Microelectronics Research & Development Center, 3370 Miraloma Avenue, Anaheim, CA 92803 and a Visiting Associate at the California Institute of Technology, Department of Applied Physics, Mail Code 116-81, Pasadena, CA 91125.     

含空位缺陷碳化硅纳米管的电子结构和光学性质

Based on first-principle calculations,the electronic structures and optical properties of a single-walled (7,0) SiC nanotube(SiCNT) with a carbon vacancy defect or a silicon vacancy defect are investigated.In the three silicon atoms around the carbon vacancy,two atoms form a stable bond and the other is a dangling bond.A similar structure is found in the nanotube with a silicon vacancy.A carbon vacancy results in a defect level near the top of the valence band,while a silicon vacancy leads to the formation of three defect levels in the band gap of the nanotube.Transitions between defect levels and energy levels near the bottom of the conduction band have a close relationship with the formation of the novel dielectric peaks in the lower energy range of the dielectric function.     

Formation of radiation defects in high-resistivity silicon as a result of cyclic irradiation and annealing

Transformation of radiation-induced defects in p ⁺-n-n ⁺ structures fabricated from highresistivity n-type silicon subjected to cyclic irradiation and annealing is investigated. The kinetic behavior of the increase in the concentration of the C_i-O_i defects is analyzed as a function of the detector fabrication process. During the second irradiation cycle a transformation of the defects, which were formed as a result of annealing of the original radiation defects, is observed. The appearance of “hidden” sources of deep center formation is revealed. It is established that the presence of a higher oxygen concentration, which arises in the samples as a result of the extended silicon oxidation process, results in a more active complex-formation of carbon-containing defects in comparison with samples with reduced oxygen content. Fiz. Tekh. Poluprovodn. 31, 299–304 (February 1997)     

Properties of p +-n structures with a buried layer of radiation-induced defects

The p ⁺-n structures based on n-type Si with dopant density 1.7×10¹³–1.2×10¹⁴ cm⁻³ were irradiated with ²³⁸Pu α particles. A layer containing radiation-induced defects with a density of the order of 3×10¹³ cm⁻³ was produced at a depth of 20 μm. This defect density gave rise to intense draining of nonequilibrium carriers in the injection-extraction regime with stationary injection as well as with pulsed generation by single particles. This makes it possible to treat the damaged layer as a plane, introduced into the bulk, with an infinite surface recombination rate. The radiation-induced defects also participated in decreasing the conductivity. A characteristic space charge distribution and, correspondingly, a bias dependence of the capacitance are observed in the structure under reverse bias. Despite the presence of formally three charge regions, four sections appear on the capacitance curve. This latter effect is due to the “additional” charge step arising in the contact potential difference field and is characteristic of compensated deep levels in semiconductors. Fiz. Tekh. Poluprovodn. 32, 359–365 (March 1998)     

On the problem of the radiation hardness of SiC nuclear radiation detectors at high working temperatures

Owing to the radiation-induced pronounced conductivity compensation in silicon carbide, carrier localization (trapping) prevails over recombination in capture of nonequilibrium carriers. This makes it possible, by raising the temperature, to reduce the time of carrier retention by a trapping center to values shorter than the duration of signal shaping by electronic circuits. For structural defects created by 6.5-MeV protons, the temperature excluding degradation of the detector signal via carrier localization is estimated. The values of the appearing generation current the noise of which can restrict the operation of a detector in the spectrometric mode are determined.     

High-performance AlGaAs/GaAs HBT's utilizing proton-implanted buried layers and highly doped base layers

Fabrication of AlGaAs/GaAs heterojunction bipolar transistors (HBT's) using a proton-implanted external collector layer and a highly doped base layer is presented. Influence of the proton implantation on base-collector junction characteristics is systematically investigated. At the optimized implantation condition, a buried semi-insulating layer beneath the external base is formed without deteriorating the junction current-voltage characteristics. In a fabricated HBT with 2 µm × 10 µm emitter size, a cutoff frequency fTof 50 GHz and a maximum oscillation frequency fmaxof 70 GHz have been achieved.     

Asymmetric waveguide devices with buried AlO/sub x/ cladding layers

We demonstrate a highly asymmetric waveguide filter for wavelength division multiplexing applications using wet oxidation of AlAs to form low-index cladding layers. The dual waveguide structure consists of a low-index polymer waveguide coupled to a lossy high-index AlGaAs waveguide. The high asymmetry between the polymer and AlGaAs yields high resolution at small device lengths. The light is coupled in and out of the polymer guide and exhibits Fabry-Perot-like resonances as the light couples to different modes of the AlGaAs. With a device length of 400 /spl mu/m, we observe resonances with a width of about 1 nm at 800 nm, agreeing with theoretical expectations. In addition to the simple filter demonstrated here, such a structure could be used to form active light emitting or detector devices.     

Electrical characterization of dielectrically isolated siliconsubstrates containing buried metallic layers

Dielectrically isolated substrates containing buried highly conducting WSi₂ layers are characterized for the first time using MOS capacitors. The active silicon layer is approximately 3 μm thick with a buried WSi₂ layer adjacent to the isolation layer. The buried metal forms the back contact of the capacitor and excellent MOS characteristics are observed. Minority carrier lifetimes in excess of 200 μs were measured indicating the suitability of these substrates for use in device manufacture     

具有部分界面等电势浮空埋层的高压SOI PLDMOS

A novel silicon-on-insulator（SOI） high-voltage pLDMOS is presented with a partial interface equipotential floating buried layer（FBL） and its analytical model is analyzed in this paper.The surface heavily doped p-top layers,interface floating buried N⁺/P⁺ layers,and three-step field plates are designed carefully in the FBL SOI pLDMOS to optimize the electric field distribution of the drift region and reduce the specific resistance.On the condition of ESIMOX（epoxy separated by implanted oxygen）,it has been shown that the breakdown voltage of the FBL SOI pLDMOS is increased from—232 V of the conventional SOI to—425 V and the specific resistance R_on,sp is reduced from 0.88 to 0.2424Ω·cm².     

Gallium phosphide epitaxial layers with high mobility

Measurements on epitaxial layers of GaP, containing negligible amounts of GaAs, have yielded mobilities up to 200cm2/Vs at room temperature, and a peak value of 1480cm2/Vs. The residual impurity appears to be Si.     

Redistribution of Al in implanted SiC layers as a result of thermal annealing

The experimental Al concentration profiles formed on implantation of Al into SiC at room temperature with subsequent high-temperature annealing are analyzed. It is shown that, at doses above the amorphization threshold, the profiles exhibit a number of specific features: a shift of the maximum of the distribution, accumulation of dopants at the surface, and formation of box-shaped profiles. To describe quantitatively the redistribution of Al dopants in the SiC layers implanted with high doses, the segregation-diffusion model is suggested for the first time. The model takes into account segregation of dopants between the α and c phases during solid-state epitaxial crystallization followed by diffusion of dopants and their evaporation from the surface The formation of box-shaped Al profiles as a result of short-term thermal annealing is attributed to the origination of highly damaged single-crystal and polycrystalline SiC layers in the recrystallized region, with a high diffusion coefficient of dopants, and to the suppression of the enhanced transient diffusion in the remaining single-crystal part of the implanted layer.     

Interaction of Fluorocarbon with Silicon Monoxide and Processes of SiC Nanowire Formation

Semiconductors - A study of the processes of the thermal carbonization of silicon monoxide in the presence of nonstoichiometric carbon monofluoride demonstrated that raising the annealing...     

Large-area oxidation of AlAs layers for dielectric stacks and thick buried oxides

The wet oxidation of AlAs and AlGaAs has been limited to relatively small lateral dimensions and relatively thin layers. Approaches are described to extend the oxide dimensions both horizontally and vertically, creating large-area and thick buried oxides. Two types of large-area structures are examined: dielectric stacks with thin buried oxides and semiconductor-on-insulator structures with thick buried oxides. Low Al-content AlGaAs layers with low oxidation rates are used as the high-index layers in large-area dielectric-stack structures. High Al-content AlGaAs layers with low volume contraction are used to create stable, thick buried oxides with millimeter-scale areas.     

Effect of low-temperature annealing on characteristics of SiC detectors with radiation-induced defects

p ⁺-n-n ⁺ detector structures based on CVD films with an uncompensated donor concentration of 2 × 10¹⁴ cm^?3 have been studied. The p ⁺-region was created by implantation of Al ions. The detectors were preliminarily irradiated with 8-MeV protons at a fluence of 3 × 10¹⁴ cm^?2 and then annealed at 600°C for 1 h. In measurements performed in the temperature range 20–150°C, the forward-and reverse-bias modes were compared. It is shown that the annealing leads to a higher collection efficiency of carriers generated by nuclear radiation and to a decrease in the amount of charge accumulated by traps in the course of testing. Despite the positive effect of the annealing, a considerable amount of radiation defects remain, which is manifested, in particular, in the kinetics of the forward current.