摘要:

Nanocrystals of group‐IV semiconductor materials (Si, Ge, and SiGe) have been fabricated in SiO2by ion implantation and subsequent thermal annealing. The microstructure of these nanocrystals has been studied by transmission electron microscopy. Critical influences of the annealing temperatures and implantation doses on the nanocrystal size distributions are demonstrated with the Ge‐implanted systems. Significant roughening of the nanocrystals occurs when the annealing temperature is raised above the melting temperature of the implanted semiconductor material. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359843

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An investigation of the electrical and structural properties of rapid thermal annealed Czochralski silicon wafers has been carried out. The electrical properties examined here are the minority carrier lifetime, measured using the laser microwave photoconductance technique, and the donor concentration (Nd), determined by the four‐point probe method. Thermal donors were intentionally introduced into the silicon and were found to be completely annihilated by the rapid thermal annealing (RTA) process. The minority carrier lifetime was found to increase significantly for wafers annealed at 900 and 1000 °C. It was concluded that due to the very short annealing time used in this work, a denuded zone was unlikely to form in silicon and be responsible for the increase in the lifetime. Infrared, x‐ray photoelectron (XPS) and Auger electron spectroscopies were used for the structural analysis. Auger results showed that higher oxygen concentration could be found in a thicker layer of silicon in annealed wafers, as compared to the as‐received, virgin sample. The XPS data showed that the SiO2:Si ratio increased from 0.28 for the virgin sample to 3.5 for wafers annealed at 1000 °C. It is suggested that the Auger and XPS data could be explained by considering oxygen outdiffused from the bulk of the silicon to the native oxide and the silicon next to the native oxide. We believe this is the first investigation of the effect of RTA on the behavior of oxygen and thermal donors, and its influence on the minority carrier lifetime of Czochralski silicon. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359844

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The distribution of interstitial oxygen and oxygen precipitates as a function of the anneal time was studied using a low‐temperature infrared absorption spectroscopy. We found that the density of the precipitation nuclei formed by an anneal at 800 °C is lower in the ring area than in the other areas of the wafer. The appearance of the ring area after precipitation annealing strongly depends on the preanneal temperature. A model explaining the formation of the ring‐shaped distribution of oxygen precipitates after two‐step anneal is proposed. In this model, the anomalous ring‐shaped distribution is explained by assuming the existence of nuclei which have been already nucleated in the ring area at an elevated temperature during crystal growth. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359845

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We investigate how the mobility and carrier density of AlGaAs/GaAs two‐dimensional electron gas are influenced by the fabrication process with plasma‐excited chemical vapor deposition (plasma‐CVD) SiN film. These properties are greatly reduced by annealing with plasma‐CVD SiN film as a cap but are restored by reannealing after removing the SiN film. We further use capacitance‐voltage measurements to investigate the influence of this same process on a more simplified structure, Si‐doped GaAs layer. Annealing with a plasma‐CVD SiN film changes the defect density of Si‐doped GaAs in two, temperature dependent ways: annealing below 380 °C reduces deposition damage, and annealing above 300 °C produces new defects, which might be caused by the film stress. These new defects can be reduced by reannealing after removing the SiN film. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.359846

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In order to develop a method to detect low‐level oxygen in thin silicon crystals by photoluminescence (PL), a radiative carbon–oxygen center (Ccenter: 0.79 eV) is formed in silicon crystals through carbon introduction by ion implantation. The PL intensity of theCcenter of the implanted sample is significantly increased by annealing the sample at 1000 °C followed by electron irradiation. The possibility of detecting a low concentration of oxygen (below 1×1015atoms/cm3) in a layer thinner than 1 &mgr;m thick is seen. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359847

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A monoenergetic slow positron beam has been used for the first time to profile porous silicon films. High values of the Doppler‐broadened line shape parameters are observed, which correspond to positron annihilation within the porous layers and these are attributed to the decay of para‐positronium. After allowing for the reduced density of the porous film, fitted values of thickness were deduced which were in reasonable agreement with values obtained from ellipsometry measurements. Low values of the Doppler parameters observed for the two samples with the thinnest films are attributed to oxide residing at the interface of the porous and bulk silicon regions. Etching the samples in a solution of 48% hydrogen fluoride reduced the porous film thickness significantly, suggesting that a considerable amount of the film consists of SiO2. A four‐component convolution analysis routine is used to analyze the individual 511 keV annihilation peaks, the result of which confirms the formation of positronium within the porous layer. Positron annihilation is shown to be a promising method for the nondestructive investigation of thin porous films. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359848

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The density of nanometer sized particles of different materials (Pd, Ag, Co, Carbon, oil droplets and oil burner exhaust) suspended in a carrier gas is determinedinsituas function of particle radius via the measurement of particle mobility and inertia using a differential mobility analyzer and a low pressure impactor. From the density and size of agglomerated particles, information on the structure of the agglomerates can be obtained; in particular a fractal‐like dimension can be determined. Whereas the densities of carbon particles and of particles in oil burner exhaust have the expected values, the densities of the metal particles are too low compared to the bulk values. The results for the fractal‐like dimensions of the agglomerates can be explained by assuming a mixture between monomer‐cluster and cluster‐cluster agglomeration in the free‐molecular regime. The fractal‐like dimension of ferromagnetic Cobalt agglomerates provides evidence that particles consisting of magnetic materials tend to form chainlike agglomerates. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359849

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Cylindrical cavities, viewed through the side as they collapsed onto solid surfaces, were studied using high‐speed streak and framing photography. The cavities were collapsed asymmetrically using shock waves of varying amplitude so that the rear surface formed a high‐speed jet which crossed the cavity and interacted with the target surface. Schlieren optics were used to visualise waves in the fluid and in the target. Two features of the collapsing bubble affected the damage to the target surface. The first was the impact of the high‐speed liquid jet on either the rear wall of the cavity or the target itself. The second was the production of a strong compression wave on the rebound of the bubble after it reached minimum volume. Damage to the targets related to their material properties. Metals, with low compressive but higher tensile strengths, plastically deformed beneath the penetrating jet to form a pit. Brittle materials, with high compressive but low tensile strengths, deformed by cracking. The position of the cavity relative to the surface had a major effect upon the geometry of the damage. With the cavity close to the target, the penetrating jet dominated the damage leaving single pits. With the cavity at some distance, the rebound wave was more important than the jet giving rise to a circular damage mark. This mechanism can be used to re‐interpret previous experimental observations [Y. Tomita and A. Shima, J. Fluid Mech.119, 535 (1986)]. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359850

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A high‐resolutioninsituSEM (scanning electron microscope) has been configured for real time comparison studies of the electromigration characteristics of Cu and Cu(Sn) alloys. Drift velocity test structures were fabricated and used to simulate the Cu line/W via structure in the multilevel interconnects. Electromigration comparison testings were carried out over a temperature range of 250 to 450 °C and current density of 5×105to 2.1×106A/cm2. Under these test conditions, the measured electromigration activation energy for Cu, Cu(0.5 wt %Sn), Cu(1.0 wt % Sn), and Cu(2 wt % Sn) are 0.73, 0.95, 1.25, and 1.14 eV, respectively. The measured critical length for Cu and Cu(Sn) alloys are &bartil;2.5 &mgr;m at a current density of 2.1×106A/cm2. The observed average drift velocity of Cu mass transport in Cu(Sn) alloys changes with the depletion of Sn atoms which were also found to move in the direction of electron current. Eventually, the Cu mass transport rate reaches a value comparable to that in pure copper test stripes. The measured resistivity values of the Cu(0.5 wt % Sn) and Cu(1 wt % Sn) using Van der Pauw test structures are 2.4 and 2.9 &mgr;&OHgr; cm, respectively. In comparison with Cu and Al(Cu) device interconnects, Cu(Sn) alloys exhibits higher electromigration activation energy, good resistance to hillocks and void formation and comparable resistivity. These characteristics clearly indicate the fact that Cu(Sn) alloys are potentially good candidate for advanced device interconnect applications where high‐current density and good electromigration resistance are required. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.359851

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have developed a novel grain‐boundary diffusion model using the transmission‐line matrix method. In conjunction with a two‐dimensional Monte Carlo thin‐film growth simulator, this model can be employed for the analysis of impurity diffusion in thin‐film diffusion barriers with realistic microstructures. In the model, the impurity at the upper surface of the barrier layer may diffuse through rapid and irregularly shaped grain‐boundary diffusion paths to reach the bottom surface. Calculations of the impurity concentration and out‐diffusion flux as a function of elapsed diffusion time and position enable the evaluation of the effectiveness of the barrier layer at a microstructure level. Consequently, the diffusion process is depicted with less assumptions and more precisely than previously available approaches. This paper details the grain‐boundary diffusion modeling method outlined above, with the emphasis on the treatment of various boundary conditions. A representative application to titanium nitride (TiN) thin‐film diffusion barriers is also demonstrated, as befits the high level of interest in this particular material for very large scale integrated devices. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360744

出版商:AIP    

年代:1995

数据来源: AIP