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Spatial distribution and properties of oxide were examined in 300 mm nitrogen (N) doped CZ-Si. Experimentally grown materials with N ranging from ∼ 10 13 cm -3 to 10 15 cm -3 were studied by infrared light scattering tomography, scanning infrared microscopy, transmission electron microscopy and electron beam induced current. It was established that an increasing N content improves the uniformity of the radial distribution of precipitates in the bulk of the wafer, the density of precipitates reaching a level of ∼ 10 9 cm -3 . The width of the denuded zone varies in the range from 15 μm to 70 μm depending on radial position and N doping level. Electron microscopy revealed lower oxide precipitate densities of about 10 5 to 10 8 cm -3 . The results are interpreted in terms of existence of agglomerates of nanometer size precipitate muclei and/or by the defect-induced strain relaxation around the precipitates.

Interfaces of bonded hydrophilic and hydrophobic wafer pairs are studied by multiple internal reflection spectroscopy after annealing at 1100°C. Si−Hx and SiO−H stretching modes are still present in bonded hydrophilic wafers. Interfaces of bonded hydrophobic wafers, prepared by joining HF-etched surfaces without defonized water rinsing, are characterized by the dominance of hydrides (SiH, SiH2, SiH3). Their concentration is about 100 times higher than for bonded hydrophilic wafers. Comparison with the ATR-spectra of HF-treated surfaces showed appreciable shifts in the peak positions indicating that Si−H bonds might be involved in the bonding process.

The incubation time t0 of the crystallization of intrinsic and P, B-doped amorphous silicon-germanium (a-Si1–xGex: H) layers deposited on SiO2/Si(100) substrates is studied as a function of temperature and composition using in situ transmission electron microscopy (TEM). The temperature dependence of t0 follows an Arrhenius behavior t0 = t0* exp (W/kT) with activation energy W and prefactor t0* depending on x. The dependences of grain growth, nucleation rate as well as of the morphology of the polycrystalline films on temperature, doping, and composition are estimated. Doping SiGe films with B decreases grain growth rate during crystallization. Independent of the Ge content, such films stay nanocrystalline (grain size ≪10 nm) up to an annealing temperature of 800°C. During crystallization decomposition within SiGe films is observed. Furthermore, metal-induced crystallization in the Al/a-Si1–xGex:H structures is demonstrated. Die Inkubationszeit t0, die bei der Rekristallisation von intrinsischen bzw. P- und B-dotierten amorphen Silizium-Germanium-Schichten (a-Si1–xGex:H) auf SiO2/Si(100)-Substraten auftritt, wird in Abhangigkeit von der Temperatur und Zusammensetzung mittels in situ Transmissionselektronenmikroskopie (TEM) untersucht. Die Temperaturabhangigkeit von t0 folgt einer Arrhenius-Kurve der Form t0 = t0* exp (W/kT), wobei die Aktivierungsenergie W und die Zeitkonstante t0* von der Konzentration x abhangen. Durch in situ TEM-Experimente wird die Abhangigkeit des Kornwachstums und der Keimbildungsrate, aber auch der Morphologie der polykristallinen Schichten von Temperatur, Dotierung und Komposition ermittelt. So fuhrt eine B-Dotierung z. B. zu einer Verringerung der Wachstumsrate. Unabhangig vom Ge-Gehalt solcher Schichten erreichen die Kristallite nur eine Grose von ≪ 10 nm bei Temperaturen bis 800°C. Im Rahmen solcher Rekristallisationen treten auch Dekompositionen auf. Daruber hinaus last sich eine Rekristallisation durch Metall-Phasen beeinflussen, wie am System Al/a-Si1–xGex:H gezeigt wird.

Presently the most prominent silicon materials considered for silicon-on-insulator (SOI) technologies are SIMOX (separation by implanted oxygen) and bonded SOI. The present paper will review recent developments for these two types of approaches for SOI materials with special emphasis on the progress in obtaining ultra thin bonded SOI layers by local plasma etching or an etch-back procedure involving stress compensated boron-germanium doped etch-stop layers.

Single-crystalline silicon films with thicknesses as thin as 2000 A have been prepared on thermally mismatched quartz substrates by a simple wafer-bonding approach. Initial bonding at ≈ 80 °C, storage at room temperature for more than 100 h and multi-temperature (maximum 150 °C) consecutive annealing with a 1 °C min −1 ramping rate have been adopted to strengthen the bond and to prevent debonding at the edge of the bonded pairs during annealing and etching, where thermal shearing and peeling stresses are maximum. Final etching by EDP (ethylenediamine—pyrocatechol—water) effectively reduces the peeling failure of the highly stressed thinned silicon layer, mainly due to a reduced lateral oxide etching rate along the interface. The high carrier mobility in the single-crystalline silicon layer and the transparent and insulating quartz substrate provides a new dimension of freedom in applications.

β-SiC layers produced on Si substrates by rapid thermal chemical vapor deposition have been transferred onto oxidized Si substrates by bonding and etchback. For SiC films with a mean surface roughness of about 20 A, room temperature bonding to smooth oxidized Si wafers is possible under the influence of an external force. For 4 in. diam substrates, bonding of ∼85% of the area was obtained. Sections of the SiC/Si layer of the bonded pair peeled off when the Si substrate of the SiC layer is thinned down to ∼150 μm and below. This is probably caused by the low interface fracture energy due to trapped air at the bonding interface and by outgassing from the thermal oxide of SiC in addition to the film stress. Multistep annealing at 1100 o C between KOH etches of the Si substrate can enhance the interface fracture energy of the bonded pairs. A densification step of the SiC thermal oxide after dry oxidation helps to reduce the trapped gas in the oxide. Auger and transmission electron microscope, results have verified that the transferred SiC layer retains its original properties

Dislocations are native nanowires. The realization of well-defined dislocation networks allows the electrical characterization of only a small number of dislocations. Different types of dislocations were analyzed by integration into the channel of MOSFETs. A substantial increase of the drain current was proved if only a few dislocations are present in the channel of nMOSFETs. Low-temperature measurements indicate single-electron tunneling on dislocation core defects.

The (dynamic) glass transition of polymers in nanometer thin layers is both a prevailing but as well a highly controversial topic. In the current review the literature for the most studied case of polystyrene (as freestanding films or as deposited and suspended layers) will be discussed. Based on this, the extraordinary impact of sample preparation is immediately evident and outlined in detail. Recent results are presented on nanometric thin (≥5 nm) layers of polystyrene (PS) having widely varying molecular weights and polymethylmethacrylate (PMMA) deposited on different substrates. For the dielectric measurements two sample geometries are employed: the conventional technique using evaporated electrodes and a recently developed approach taking advantage of silica nanostructures as spacers. All applied methods deliver the concurring result that deviations from glassy dynamics and from the glass transition of the bulk never exceed margins of ±3 K independent of the layer thickness, the molecular weight of the polymer under study and the underlying substrate. Novel experiments are described on thin layers of polyisoprene, a type A polymer, having relaxation processes on two different length scales, the segmental and the normal mode. A further exciting perspective is the measurement of the dynamics of isolated polymer coils, for which first results will be presented.

This article deals with uncertainty in the analysis of strain in silicon nanoscale structures and devices using nanobeam electron diffraction (NBED). Specimen and instrument related errors and instabilities and their effects on NBED analysis are addressed using a nanopatterned ultrathin strained silicon layer directly on oxide as a model system. We demonstrate that zero-loss filtering significantly improves the NBED precision by decreasing the diffuse background in the diffraction patterns. To minimize the systematic deviations the acquired data were verified through a reliability test and then calibrated. Furthermore, the effect of strain relaxation by specimen preparation using a FIB is estimated by comparing profiles, which were acquired by analyzing slices of strained structures in a 220-nm-thick region of the sample (invasive preparation) and the entire strained nanostructures, which are embedded in a thicker region of the same sample (noninvasive preparation). Together with the random deviation, the corresponding systematic shift results in a total deviation of ∼1 × 10−3for NBED analyses, which is employed to estimate the measurement uncertainty in the thinner sample region. In contrast, the strain in the thick sample region is not affected by the preparation; the systematic shift reduces to a minimum, which improves the total deviation by ∼50%.

The accurate manipulation of strain in silicon nanowires can unveil new fundamental properties and enable novel or enhanced functionalities. To exploit these potentialities, it is essential to overcome major challenges at the fabrication and characterization levels. With this perspective, we have investigated the strain behavior in nanowires fabricated by patterning and etching of 15 nm thick tensile strained silicon (100) membranes. To this end, we have developed a method to excite the "forbidden" transverse-optical (TO) phonons in single tensile strained silicon nanowires using high-resolution polarized Raman spectroscopy. Detecting this phonon is critical for precise analysis of strain in nanoscale systems. The intensity of the measured Raman spectra is analyzed based on three-dimensional field distribution of radial, azimuthal, and linear polarizations focused by a high numerical aperture lens. The effects of sample geometry on the sensitivity of TO measurement are addressed. A significantly higher sensitivity is demonstrated for nanowires as compared to thin layers. In-plane and out-of-plane strain profiles in single nanowires are obtained through the simultaneous probe of local TO and longitudinal-optical (LO) phonons. New insights into strained nanowires mechanical properties are inferred from the measured strain profiles.

Defects in crystalline materials modify locally the periodic order in a crystal structure. They characterize the real structure and modify numerous physical and mechanical properties of a crystal. Crystal defects are generally divided by their dimension: point defects are also known as zero-dimensional (0-D) defects, while dislocations are 1-D, twins and grain boundaries are 2-D, and precipitates are denoted as 3-D defects. Dislocations were implemented for the first time in the early 1900th to explain the elastic behavior of homogeneous, isotropic media. Based on Volterra s “distorsioni” (Volterra, 1907), Love has introduced the term “dislocation” to describe a discontinuity of displacement in an elastic body (Love, 1927). The application of this term to denote a particular elementary type of deviation from the ideal crystal lattice structure was due to Orowan (1934), Polanyi (1934), and Taylor (1934a, 1934b). A dislocation is characterized by a vector parallel to the dislocation line and a displacement or Burgers vector which is a certain finite increment 称 induced by the elastic displacement vector 鍾. The Burgers vector is equal to one of the lattice vectors in magnitude and direction and may be written as (Hirth & Lothe, 1982) ∮穴憲沈 = 完 擢通日 擢鎚 穴嫌 = −決沈 . (1)

Variations of the heating rate (so-called ramping processes) cause different mechanisms of defect formation and reaction in Cz-grown silicon, which are not known for isothermal annealings. Electron microscopic investigations show that besides quantitative alterations of the defect density there are also reactions of the Frank partial dislocations (dissociation and, in further stages, formation of additional, perfect dislocations) as well as interactions of dislocations with point defect clusters. Based on the string model, from the interaction of perfect dislocations with clusters the supersaturation of point defects (silicon self-interstitials) is estimated to be 10. Reasons for such a high supersaturation, comparable to that caused by wet oxidations, are discussed. Anderungen der Aufheizraten (sog. Rampen-Prozesse) fuhren in Cz-Silicium zu verschiedenen Me-chanismen der Defektbildung und -reaktion, die von isothermen Warmebehandlungen nicht bekannt sind. Durch elektronenmikroskopische Untersuchungen wird gezeigt, das neben quantitativen Veranderungen der Defektdichten vor allem Reaktionen der Frankschen Partialversetzungen an Stapelfehlern (Dissoziation und in weiteren Stadien auch die Neubildung von vollstandigen Versetzungen) sowie Wechselwirkungen von Versetzungen mit Punktdefektclustern zu beobachten sind. Basierend auf dem String-Modell wird aus der Wechselwirkung von vollstandigen Versetzungen mit Jen Clustern eine Punktdefektubersattigung (Si-Eigenzwischengitteratome) von 10 abgeschatzt. Ursachen fur diese hohe Ubersattigung, die vergleichbar ist mit Feuchtoxidationen, werden diskutiert.

The initial stages of the formation of rod-like defects (RLD) in FZ silicon (n-type as well as p-type Si) are investigated by high-resolution electron microscopy (HREM). These defect represent a special type of agglomeration of self-interstitials on {113} planes. As possible sites of their nucleation, interstitial-type clusters are generated by ion implantation (B+, Si+). For their further growth self-interstitials are created by electron irradiation (400 keV) at room temperature. The HREM investigations show that the early stages of RLDs and their further growth are influenced by point defect and impurity clusters existing in the Si bulk. Die Bildung der Anfangsstadien von sogenannten, rod-like' Defekten (RLD) in FZ Silizium (sowohl n- als auch p-dotiertes Material) wird mittels hochauflosender Elektronenmikroskopie (HREM) untersucht. Diese Defekte stellen eine spezielle Form der Agglomeration von eigen-interstitiellen Atomen auf {113} Ebenen dar. Mogliche Stellen fur eine bevorzugte Agglomeration sind Punktdefektcluster, die in den vorliegenden Kristallen durch Ionenimplantation (B+, Si+) erzeugt werden. Die fur das weitere Defektwachstum benotigten Eigen-Zwischengitteratome werden durch Elektronen-Bestrahlung (400 keV) generiert. Die HREM Untersuchungen zeigen, das die fruhen Stadien der RLD's und ihr weiteres Wachstum durch die im Si Kristall vorhandenen Punktdefektcluster beeinflust werden.

We provide evidence of nanopatterning-induced bending of an ultrathin tensile strained silicon layer directly on oxide. This strained layer is achieved through the epitaxial growth of silicon on a Si0.84Ge0.16 virtual substrate and subsequent transfer onto a SiO2-capped silicon substrate by combining hydrophilic wafer bonding and the ion-cut process. Using high resolution transmission electron microscopy, we found that the upper face of the strained silicon nanostructures fabricated from the obtained heterostructure using electron beam lithography and dry reactive ion etching displays a concave shape. This bending results from the free-surface-induced strain relaxation, which implies lattice out-of-plane expansion near the edges and concomitant contraction at the center. For a ∼110 nm × 400 nm × 20 nm nanostructure, the bending is associated with an angle of 1.5 ◦ between the (2¯ 20) vertical atomic planes at the edges of the ∼110 nm side. No bending is, however, observed at the strained Si/SiO2 interface. This phenomenon cannot be explained by the classical Stoney’s formula or related formulations developed for nanoscale thin films. Here we employed a continuum mechanical approach to describe these observations using three-dimensional numerical calculations of relaxation-induced lattice displacements. (Some figures in this article are in colour only in the electronic version)

The physical properties of materials can be manipulated by applying stress or strain. For instance, the controlled introduction of strain in silicon (Si) devices was found to increase the charge careers mobility and modify the Si optical properties. The exploitation of this potential technology raises fundamental questions on strain and stress stability and behavior during the fabrication and processing of strained Si devices. In this paper, we address this issue and provide detailed three-dimensional finite element simulations of strain redistribution upon nanoscale patterning that is a crucial step in the fabrication of devices. The shown calculated results give valuable insights into the relaxation phenomenon of nano-scale strained silicon mesa-structures and point out ways to modify the strain field in one-dimensional optical micro-cavity waveguides based on photonic crystal designs. Our calculations are augmented by experimental data obtained by UV μ-Raman spectroscopy analysis.

The strain behavior in nanoscale patterned biaxial tensile strained Si layer on insulator is investigated in 60-nm-thick nanostructures with dimensions in the 80-400 nm range. The in-plane strain is evaluated by using UV micro-Raman. We found that less than 30% of the biaxial strain is maintained in the 200x200 nm(2) nanostructures. This relaxation, due to the formation of free surfaces, becomes more important in smaller nanostructures. The strain is completely relieved at 80 nm. This phenomenon is described based on detailed three-dimensional finite element simulations. The anisotropic relaxation in rectangular nanostructures is also discussed.

Metallic impurities are detrimental to many silicon devices and limit the efficiency of multi crystalline silicon solar cells. Therefore they are a major subject of ongoing research. Photoluminescence spectroscopy is a promising technique for detecting precipitated metals in silicon because of its sensitivity to the minority carrier density and to specific types of defects; however the impact of impurities on the defect luminescence could not be clarified yet. In this letter we examine the role of micron-sized iron and copper precipitates in direct bonded wafers by micro-photoluminescence spectroscopy. Both kinds of precipitates are detectable by means of the reduced band-to-band luminescence. An element-specific effect on the defect luminescence is observed. The results are confirmed by X-ray fluorescence spectroscopy.

This article addresses the behavior of strain in ultrathin SSOI during the nanopatterning process.

A MOS-LED and a p-n LED emitting based on the dislocation-related luminescence (DRL) at 1.5 micron were already demonstrated by the authors. Here we report recent observation of the Stark effect for the DRL in Si. Namely, a red/blue-shift of the DRL peak positions was observed in electro- and photo-luminescence when the electric field in the pn-LED was increased/lowered. Fitting the experimental data yields a strong characteristic coefficient of 0.0186 meV/(kV/cm)2. This effect may allow realization of a novel Si-based emitter and modulator combined in a single device.

As scaling of the critical transistor dimensions below 65 nm has been slowed down, the implementation of novel materials, especially high mobility channel materials is most attractive to boost the transistor performance. Applying strain to silicon has become a successful route. The electron mobility can be enhanced by biaxial strain introduced into Si by epitaxial growth of Si on a strain relaxed SiGe layer or by so called process induced methods applied directly on transistor level. The combination of strained Si and SOI is particularly promising due to the combination of the enhanced mobilities and the inherent advantages of SOI. First long channel n-MOSFETs with gate lengths of 5 to 50 mum and a 6.6 nm thick SiO2 gate dielectric were fabricated. For comparison, devices on unstrained SOI were made. The transfer characteristics of a fully depleted sSOI-MOSFET with a gate length of 5 mum and a gate width of 20 mum indicating an inverse sub-threshold slope of 75mV/dec.

Well-controlled fabrication of dislocation networks in Si using direct wafer bonding opens broad possibilities for nanotechnology applications. Concepts of dislocation-network-based light emitters, manipulators of biomolecules, gettering and insulating layers, and three-dimensional buried conductive channels are presented and discussed. A prototype of a Si-based light emitter working at a wavelength of about 1.5 microm with an efficiency potential estimated at 1% is demonstrated.

Strained silicon on insulators (sSOI) wafers with a supercritical thickness of 58 nm were produced using thin strain relaxed SiGe buffer layers, wafer bonding, selective etch back and epitaxial overgrowth. Raman spectroscopy revealed an homogeneous strain of 0.63 plusmn 0.03 % in the strained Si layer. Long channel n-type SOI-MOSFETs showed very large electron mobilities up to 1200 cm2/Vs in the strained Si devices. These values are more than two times larger than those of reference SOI n-MOSFETs. Mobility simulations with state of the art scattering models are then used to interpret the experiments.

A new concept for a Si light emitting diode (LED) capable of emitting at 1.5 mum efficiently is proposed. It utilizes radiation from a well-defined dislocation network created in a reproducible manner by Si wafer direct bonding. The wavelength of the light emitted from the network can be tailored by adjusting the misorientation between the Si wafers

Different approaches for Si-based light emitters were studied. The D band emission of dislocations formed by wafer bonding is a promising candidate for spatially confirmed emitters at 1.3mum leslambdales1.5mum

A novel Si MOS-LED is demonstrated, which is fully compatible with Si technology. It is based on a dislocation network fabricated by wafer direct bonding. Light emission at 1.5 μm was observed when the network was near the Si/SiO2 interface close to/inside the accumulation layer induced by the gate voltage.

Low-temperature measurements proved the existence of a two-dimensional electron gas at defined dislocation arrays in silicon. As a consequence, single-electron transitions (Coulomb blockades) are observed. It is shown that the high strain at dislocation cores modifies the band structure and results in the formation of quantum wells along dislocation lines. This causes quantization of energy levels inducing the formation of Coulomb blockades.

Spatial light modulators (SLMs) based on micromirrors for use in DUV lithography and adaptive optics require very high mirror planarity as well as mirror stability. The ideal mechanical properties of monocrystalline silicon make this material ideally suited for use in high precision optical MEMS devices. However, the integration of MEMS with CMOS poses certain restrictions on processing temperatures as well as on the compatibility of materials. The key to the successful fabrication of monocrystalline silicon micromirrors on CMOS is the silicon layer transfer process. Here, we discuss two carefully adapted wafer bonding processes that are CMOS compatible and that allow the transfer of a 300nm thick monocrystalline silicon thin film from a SOI donor wafer. One process is based on adhesive bonding using a patterned polymer layer, while the other process is based on direct bonding to a planarization layer of polished glass.

In silicon wafer bonding, the initial contact area spreads laterally with a typical speed on the order of 10 mm/s. We observed that this lateral bonding speed increases with decreasing ambient pressure, and is independent of the distance of the contact front to the rim of the wafers and independent of wafer thickness. From these results, we conclude that the lateral bonding speed is mainly determined by pressing the ambient gas out between the two wafers from a very localized area close to the propagating bonding front.

Bonded hydrophobic wafer pairs (PEW wafers) are applied as alternative substrates for optical devices (pin-diodes and complex MOEMS). Important parameters of diodes are analysed at temperatures up to 160/spl deg/C (dark current, photocurrent, CV-curves, rise time). Diodes produced on bonded hydrophobic wafer pairs show a similar or better behaviour than components prepared on the standard epitaxial wafers.

Wafers prepared by an HF dip without a subsequent water rinse were bonded at room temperature and annealed at temperatures up to 1100 °C. Based on substantial differences between bonded hydrophilic and hydrophobic Si wafer pairs in the changes of the interface energy with respect to temperature, secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM), we suggest that hydrogen bonding between Si‐F and H‐Si across two mating wafers is responsible for room temperature bonding of hydrophobic Si wafers. The interface energy of the bonded hydrophobic Si wafer pairs does not change appreciably with time up to 150 °C. This stability of the bonding interface makes reversible room‐temperature hydrophobic wafer bonding attractive for the protection of silicon wafer surfaces.

Wafer bonding started as a specific way to fabricate inexpensive thick (>1 /spl mu/m) film silicon-on-insulator (SOI) materials of high quality. In the meantime, also ultrathin SOI layers can be produced by wafer bonding and proper thinning techniques. In addition, silicon wafer bonding has shown to be a versatile technique for fabricating sensors and actuators. Especially in this area it is desirable to perform bonding at a temperature as low as possible. Wafer bonding may also be used to produce combinations of materials which may differ in terms of structure, crystallinity or lattice constant. The last feature allows the fabrication of III-V compound combinations which are not lattice matched and may be used for vertical cavity surface emitting lasers.

Phase separation and thermal crystallization of SiO/SiO 2 superlattices result in ordered arranged silicon nanocrystals. The preparation method enables independent control of particle size as well as of particle density and spatial position by using a constant stoichiometry of the layers. Infrared absorption and photoluminescence spectra are measured as a function of annealing temperature to study the phase separation process. Three photoluminescence emission bands are observed. A band centered at 560 nm is found in as-prepared samples and vanishes for annealing above 700 o C. A second band around 760 nm to 890 nm is detected for annealing temperatures above 500 o C. The superlattices show a strong luminescence and a size dependent blue shift in the visible and near-infrared region after crystallization for temperatures above 900 o C. The origin of the different photoluminescence bands at different phase separation stages of ultra thin SiO x layers are discussed based on transmission electron microscopy investigations and on correlations seen in photoluminescence spectra and infrared absorption. In addition, we report the PECVD preparation of amorphous SiO/SiO 2 superlattices which show a similar size dependent luminescence after crystallization.