The role of tin in reactions involving carbon interstitial atoms in irradiated silicon

The influence of doping with Sn on reactions proceeding with the involvement of interstitial C atoms in Si was studied. It is shown that Sn atoms in Si are effective sinks for interstitial C atoms (C_I); as a result, in Sn-doped Si, formation of C_IO_I and C_IC_S centers is not observed in the course of annealing of C_I centers; rather, C_ISn_S centers are formed. The C_IO_I and C_IC_S centers appear in Si:Sn only after annealing of the formed C_ISn_S complexes. It is ascertained that C_I atoms can occupy two different interstices around Sn atoms. The process of radiation-defect formation in Si:Sn was simulated in the approximation of quasi-chemical reactions. Expressions for dependences of concentrations of main radiation defects on the Sn content were derived; the results of calculations were compared with experimental data.     

Energy levels of vacancies and interstitial atoms in the band gap of silicon

Based on the analysis of the secondary processes of radiation-induced defect formation in Si crystals with charge-dependent selective traps for vacancies and interstitial atoms, the energy levels of vacancies and interstitial atoms were identified; these level were determined previously from the effect of the irradiation conditions on the annihilation rate of elementary primary defects. It is ascertained that the levels at ～E _c -0.28 eV and at ～E _c -0.65 eV in the band gap of Si belong, most likely, to vacancies; the levels at ～E _c -0.44 eV, at ～E _c -0.86 eV, and, presumably, at ～E _c -0.67 eV belong to intrinsic interstitial atoms.     

Erbium impurity atoms in silicon

It is shown using ¹⁶⁹Er(¹⁶⁹Tm) Mössbauer emission spectroscopy that the photoluminescent centers in crystalline erbium-doped silicon are [Er-O] clusters and that the local symmetry of the Er³⁺ ions in these clusters is similar to that in Er₂O₃. The photoluminescent centers in amorphous hydrogenated erbium-doped silicon are clusters, whose local structure also corresponds to erbium oxide.     

Diffusion of interstitial magnesium in dislocation-free silicon

The diffusion of magnesium impurity in the temperature range T = 600–800°C in dislocation-free single-crystal silicon wafers of p-type conductivity is studied. The surface layer of the wafer doped with magnesium by the ion implantation technique serves as the diffusion source. Implantation is carried out at an ion energy of 150 keV at doses of 5 × 10¹⁴ and 2 × 10¹⁵ cm^–2. The diffusion coefficient of interstitial magnesium donor centers (D _i ) is determined by measuring the depth of the p–n junction, which is formed in the sample due to annealing during the time t at a given T. As a result of the study, the dependence D _i (T) is found for the first time. The data show that the diffusion process occurs mainly by the interstitial mechanism.     

Photoconductivity of silicon with nanoclusters of manganese atoms

In this work, specific features of photoconductivity of silicon with multicharge nanoclusters of manganese atoms are investigated. It is shown that for such samples, anomalously high impurity photoconductivity is observed in the spectral region λ = 1.8–3 μm. It is also shown that such samples possess giant residual photoconductivity.     

Recombination-induced random walk diffusion of interstitial carbon in silicon

Recombination events at interstitial carbon atoms in silicon cause the carbon to step to adjacent interstitial positions. DLTS inp-type silicon is used to measure the random walk from interstitial carbon to interstitial carbon-oxygen centers. Electron capture at the interstitial carbon defect causes the carbon to step with a frequency of once per 16 capture events. Using 100 keV electron irradiations to produce electron-hole recombination events, we measure: the step frequency, electron capture cross section, and the mean time between electron captures at the interstitial carbon defect. Measurement of athermal diffusion in the dark indicates that the time between recombination events at interstitial carbon is 0.92 × 10¹¹ seconds if the electron density is 1 m⁻³. Interstitial carbon moves rapidly at low temperature by this random walk in p-type silicon.     

Dopant atoms as quantum components in silicon nanoscale devices

Recent progress in nanoscale fabrication allows many fundamental studies of the few dopant atoms in various semiconductor nanostructures. Since the size of nanoscale devices has touched the limit of the nature, a single dopant atom may dominate the performance of the device. Besides, the quantum computing considered as a future choice beyond Moore's law also utilizes dopant atoms as functional units. Therefore, the dopant atoms will play a significant role in the future novel nanoscale devices. This review focuses on the study of few dopant atoms as quantum components in silicon nanoscale device. The control of the number of dopant atoms and unique quantum transport characteristics induced by dopant atoms are presented. It can be predicted that the development of nanoelectronics based on dopant atoms will pave the way for new possibilities in quantum electronics.     

Interstitial diffusion under conditions of trapping of interstitial impurity atoms

The diffusion equation for nonequilibrium interstitial impurity atoms in the form convenient for numerical solution has been obtained. The proposed equation takes into account all different charge states of interstitial atoms and drift of all mobile charged species in the built-in electric field, although only the concentration of the neutral impurity interstitials must be obtained to solve the equation. The absorption of impurity interstitials by immobile sinks, mobile vacancies, and due to the passivation of dopant atoms is also taken into account. The derived effective coefficients that describe diffusion and trapping of impurity interstitials have the following characteristic features: (i) their dependences on the concentration of substitutionally dissolved dopant atoms are smooth and monotone; (ii) these concentration dependences are obtained in the form traditionally used for the approximation of effective diffusivity of substitutionally dissolved dopant atoms in processing-simulation codes.To illustrate the usability and efficiency of the derived equation for simulation of diffusion of nonequilibrium interstitial impurity atoms, the migration of deuterium interstitials in the silicon substrate doped with boron has been simulated. The calculated profile of deuterium concentration in the passivated region agrees well with the experimental data.     

DEEP LEVELS RELATED TO COPPER IN SILICON

Energy positions and carrier capture cross sections of the deep levels related to copper insilicon are measured by the DLTS.The annealing behaviour and spatial distributions of some of these levelsare also studied.The results show that there are no triple aceeptor or quadruple states corresponding to thesubstitutional copper in silicon,which have been reported in literature.Most of the deep levels related tocopper in silicon correspond to complexes of copper and defects in silicon.     

Special features of spatial redistribution of selenium atoms implanted in silicon

The spatial distribution of selenium atoms implanted in silicon was studied by secondary-ion mass spectrometry after annealing in the temperature range of 600–1200°C. For implantation doses exceeding the amorphization dose for silicon, formation of a peak of selenium concentration was detected beyond the mean projected range of selenium ions. The spatial position of the peak correlates well with the spatial position of the plane in which the calculated value of the specific energy losses of selenium ions in elastic collisions (according to the TRIM code) corresponds to the critical value for amorphization of silicon. Accumulation of impurities at the peak occurs at temperatures of 700°C and higher after recrystallization of the amorphized layer. Redistribution of selenium atoms to deeper layers of the sample due to diffusion is controlled by the temperature dependence of the solubility of selenium in silicon.     

Observation of low-temperature diffusion of aluminum impurity atoms in hydrogen-implanted silicon

Single-crystal samples of aluminum-doped silicon implanted with hydrogen at ∼80 K were examined by electron spin resonance (ESR). Two new ESR spectra labeled Si-AA15 and Si-AA16 were observed. The hyperfine structure of the spectra unambiguously reveals that two aluminum atoms and one aluminum atom are incorporated in the AA15 and AA16 defects, respectively. Observation of Al-Al pairs (the AA15 defect) is evidence in favor of long-range migration of aluminum atoms. The migration occurring in the experiment at T⩽200 K cannot be normal or recombination-enhanced (injection-enhanced) diffusion. Tentative models including Al-Al interstitial pairs as well as a hydrogen-enhanced migration mechanism are discussed. Fiz. Tekh. Poluprovodn. 32, 421–428 (April 1998)     

Self-passivated copper gates for amorphous silicon thin-filmtransistors

A solution to the amorphous silicon transistor gate metallization problem in active matrix liquid crystal displays (AMLCD's) is demonstrated, in the form of a self-passivated copper (Cu) process. Cu is passivated by a self-aligned chromium (Cr) oxide encapsulation formed by surface segregation of Cr in dilute Cu-10-30 at.%Cr alloys at 400°C, solving the problems of chemical reactivity during the plasma deposition, diffusion, poor adhesion to the substrate, and oxidation. The performance of self-passivated Cu bottom-gate thin-film transistors (TFT's) and their stability during thermal bias stress testing is comparable to that of Cr-gate reference TFT's. The gate line resistivity (including encapsulation) is 4.5 μΩ·cm at present     

Ti-Si-N diffusion barriers between silicon and copper

Thin films of Ti-Si-N, reactively spattered from a Ti₅Si₃ target, are assessed as diffusion barriers between silicon substrates and copper overlayers. By tests on shallow-junction diodes, a 100 nm Ti₃₄Si₂₃N₄₃ barrier is able to prevent copper from reaching the silicon substrate during a 850°C/30 min anneal in vacuum. A 10 nm film prevents diffusion up to 650°C/30 min. By high-resolution transmission electron microscopy, Ti₃₄Si₂₃N₄₃ predominantly consists of nanophase TiN grains roughly 2 nm in size     

Quenching of EL2 defect-induced luminescence in gallium arsenide by copper atoms

It is shown that the introduction of copper atoms into gallium arsenide crystals containing EL2 antisite defects results in virtually complete vanishing of the EL2-induced luminescence bands with radiation maxima at hv _m =0.63 and 0.68 eV. This occurs as a result of the deactivation of the EL2 defects as a result of their interaction with copper atoms, which account for the formation of electrically inactive EL2-Cu complexes. Fiz. Tekh. Poluprovodn. 31, 1045–1048 (September 1997)     

Distributions of substitutional and interstitial impurities in silicon ingot with different grain morphologies

A multicrystalline silicon ingot with columnar and irregular grains was obtained from metallurgical-grade silicon (MG-Si) by directional solidification. The segregation behaviors of substitutional and interstitial impurities in different grain morphologies have been studied. The concentration distribution of substitutional impurities (B and Al) in the silicon ingot was accord with the Scheil's equation, which depended on the grain morphology. However, the concentration distribution of interstitial impurities (Fe, Ti, Cu, and Ni) was only accord with the Scheil's equation under the columnar grains growth condition. The difference lattice sites of the impurities will result in the disparate segregation behavior of impurities for columnar and irregular grains growth, which leads to the diverse concentration distribution of substitutional and interstitial impurities in the silicon ingot. Furthermore, the transport mechanism of interstitial and substitutional impurities in front of the solid-liquid interface boundary has been revealed.     

Formation and annealing of metastable (interstitial oxygen)-(interstitial carbon) complexes in n- and p-type silicon

It is shown experimentally that, in contrast to the stable configuration of (interstitial carbon)-(interstitial oxygen) complexes (C _i O _i ), the corresponding metastable configuration (C _i O _i *) cannot be found in n-Si based structures by the method of capacitance spectroscopy. The rates of transformation C _i O _i * →C _i O _i are practically the same for both n- and p-Si with a concentration of charge carriers of no higher than 10¹³ cm^?3. It is established that the probabilities of the simultaneous formation of stable and metastable configurations of the complex under study in the case of the addition of an atom of interstitial carbon to an atom of interstitial oxygen is close to 50%. This is caused by the orientation dependence of the interaction potential of an atom of interstitial oxygen with an interstitial carbon atom, which diffuses to this oxygen atom.     

Surface-enhanced fluorescence from copper nanoparticles on silicon nanowires

A method to enhance surface plasmon coupled fluorescence from copper nanoparticles on silicon nanowires is presented. Owing to resonant plasmons oscillation on the surface of Cu/Si nanostructure, the fluorescence peaks of several lanthanide ions (praseodymium ions, Pr3+,neodymium ions Nd3+, holmium ions Ho3+, and erbium ions Er3+) were markedly enhanced with the enhancement of maximal 2 orders of magnitude, which was larger than that caused by unsupported Cu nanoparticles. These results might be explained by the local field overlap originated from the closed and fixed copper nanoparticles on silicon nanowires.     

Ultrasonic evaluation of the silicon/copper interfaces in IC packaging

The silicon die and copper lead-frame in integrated circuit (IC) packaging are bonded using a die attach adhesive, and the quality of the adhesive interface is a critical issue in the reliability testing of IC packaging and during the manufacturing process. Common defects such as cracks and delamination can be detected using the C-mode ultrasonic microscopic method with sufficient confidence. However, a weak interface due to weak adhesion and poor cohesion has often gone undetected and may become a potential defect at a later stage. There is a desire to study the interface quality quantitatively, so that any potentially defective area can be evaluated and identified early. This paper describes work in evaluating the quality of the interfaces that typically exist in IC packages by using longitudinal ultrasonic wave propagation with contact transducers. An interface spring model is used to predict the ultrasonic reflection coefficient relationship with varying interfacial spring constants. Experimental results of normal incidence reflection coefficients are obtained from the two-layered specimen bonded with die attach adhesive under varying conditioning process that simulates the degrading of the interface. Good qualitative agreement between the measurement and the prediction is obtained, and shows that the reflection coefficient depends strongly on the interface quality. The study demonstrates that the quantification of the interface quality is possible, using the reflection coefficient as a criterion.     

Si(CH3)4的MPD与Si原子的双光子共振三光子电离

在４１０￣４０４ｎｍ的紫激光作业下,利用平行板电极装置研究了Ｓｉ（ＣＨ３）４的多光子解离（ＭＰＤ）及Ｓｉ原子的的双光子共振三光子电离。观察到了Ｓｉ（ＣＨ３）４分子经ＭＰＤ产生的、处于３＾３ＰＪ＾〃（Ｊ＾〃＝０,１,２）态的硅原子,依据４＾３ＰＪ＾〃←３＾３ＰＪ＾〃（Ｊ＾′、Ｊ〃＝０,１,２）跃迁谱线的强度,得到了Ｓｉ（ＣＨ３）４经ＭＰＤ产生的、处于３＾３ＰＪ＾〃（Ｊ＾〃＝０,１,２）态的硅原子的密     

Morphology of copper precipitates characterizing lattice imperfection in EFG ribbon silicon

Some kinds of lattice imperfections are thought to cause poor conversion efficiency of EFG silicon ribbon solar cells. The development of an evaluation method of the lattice imperfections is important. A copper decoration technique by 2-zone furnace method using metal copper as decoration source and the decoration morphology of edge-defined, film-fed growth (EFG) silicon ribbon are described in this paper. First. copper precipitation conditions to decorate lattice imperfections enough and to prevent alloying phenomena at the sample surface are established, and the decoration morphologies are observed by I.R. microscopy. Subsequently, the lattice imperfection-photoelectrical property relationships are examined by measuring the local photocurrent generated by a laser beam incident on the ribbon solar cell. The technique is proved to provide a good evaluation method for lattice imperfections correlating with poor photocurrent.