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In this work, the breakdown transients of Al2O3- and HfO2 based metal-insulator-metal (MIM) stacks with the same oxide thickness and identical metal electrodes were compared. Their connection with the thermal properties of the materials was investigated using alternative experimental setups. The differences and similarities between these transients in the fast and progressive breakdown regimes were assessed. According to the obtained results, Al2O3 exhibits longer breakdown transients than HfO2 and requires a higher voltage to initiate a very fast current runaway across the dielectric film. This distinctive behavior is ascribed to the higher thermal conductivity of Al2O3. Overall results link the breakdown process to the thermal properties of the oxides under test rather than to dissipation effects occurring at the metal electrodes. Fil: Pazos, Sebastián Matías. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Aguirre, Fernando Leonel. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Miranda, Enrique. Universitat Autònoma de Barcelona; España Fil: Lombardo, Salvatore. Consiglio Nazionale delle Ricerche; Italia Fil: Palumbo, Félix Roberto Mario. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

We have studied the effects of nitridation with nitric oxide on the leakage current of thin (

We have investigated the dynamics of hard intrinsic dielectric breakdown of gate oxide layers with thickness between 35 and 5.6 nm in n+ polycrystalline Si–SiO2–Si metal/oxide/semiconductor capacitors after constant voltage Fowler–Nordheim stress. The buildup of defects in the oxide during the degradation phase was monitored by quasi static C–V measurements. The dynamics of the final breakdown event was followed with high time resolution, allowing to measure voltage, current, and power versus time during the breakdown transient. Transmission electron microscopy data quantifying the damage produced during this transient are reported. Finally, we propose a phenomenological model concerning the dynamics of breakdown with model parameters adjusted on the basis of the experimental data.

The solid phase crystallization of chemical vapor deposited amorphous silicon films onto oxidized silicon wafers, induced either by thermal annealing or by ion beam irradiation at high substrate temperatures, has been extensively developed and it is reviewed here. We report and discuss a large variety of processing conditions. The structural and thermodynamical properties of the starting phase are emphasized. The morphological evolution of the amorphous towards the polycrystalline phase is investigated by transmission electron microscopy and it is interpreted in terms of a physical model containing few free parameters related to the thermodynamical properties of amorphous silicon and to the kinetical mechanisms of crystal grain growth. A direct extension of this model explains also the data concerning the ion-assisted crystal grain nucleation.

We have investigated electrical and structural characteristics of C coimplanted GexSi1−x layers formed by high dose Ge implantation in (100) Si followed by rapid thermal annealing at 1100 °C for 10 s. In the absence of C the layers, with Ge peak concentrations of about 15 at. %, are epitaxial and fully strained but show extrinsic dislocation loops in the Ge end of range region. In C coimplanted GexSi1−x the crystalline quality of the materials is improved since the formation of defects at the end of range is suppressed and the strain is reduced. From an electrical point of view the situation is reversed. The electrical characterization of p+/n diodes shows that, without C coimplantation, in GexSi1−x the hole mobility is larger than in Si, and the bandgap narrowing results in an increase of the minority carrier concentration. Moreover, the diffusion of minority carriers does not appear to be influenced by the presence of the secondary defects at the end of range. Vice versa, in C coimplanted GexSi1−x, even...

We have investigated the electrical characteristics of p+–n Si junction diodes implanted with 300 keV C ions at fluences of 0.5 and 1×1015 cm−2 and annealed at 900 or 1100 °C. In all cases cross‐sectional transmission electron microscopy shows an excellent crystalline quality, with no extended defects, and the C‐rich region is characterized by an n‐type doping. In the material annealed at 900 °C the C‐rich region shows a low electron mobility and the presence of deep donor levels, and, as a consequence, the diode characteristics are nonideal. These effects can be attributed to the formation of C–Si self‐interstitial‐type complexes after the 900 °C anneal. At 1100 °C part of the C–Si complexes dissolve and the electrical characteristics of the materials noticeably improve.

The photoluminescence of erbium‐doped semi‐insulating polycrystalline and amorphous silicon containing 30 at. % oxygen is studied. The films were deposited on single‐crystal Si substrates by chemical vapor deposition, implanted with 500 keV Er to fluences ranging from 0.05 to 6×1015 ions/cm2, and annealed at 300–1000 °C. Upon optical pumping near 500 nm, the samples show room‐temperature luminescence around 1.54 μm due to intra‐4f transitions in Er3+, excited by photogenerated carriers. The strongest luminescence is obtained after 400 °C annealing. Two classes of Er3+ can be distinguished, characterized by luminescence lifetimes of 170 and 800 μs. The classes are attributed to Er3+ in Si‐rich and in O‐rich environments. Photoluminescence excitation spectroscopy on a sample with 1×1015 Er/cm2 shows that ∼2% of the implanted Er is optically active. No quenching of the Er luminescence efficiency is observed between 77 K and room temperature in this Si‐based semiconductor. The internal quantum efficiency for the excitation of Er3+ via photogenerated carriers is 10−3 at room temperature. A model is presented which explains the luminescence data in terms of trapping of electrical carriers at localized Er‐related defects, and subsequent energy transfer to Er3+ ions, which can then decay by emission of 1.5 μm photons.

Room‐temperature electroluminescence at 1.54 μm is demonstrated in erbium‐implanted oxygen‐doped silicon (27 at. % O), due to intra‐4f transitions of the Er3+. The luminescence is electrically stimulated by biasing metal‐(Si:O, Er)‐p+ silicon diodes. The 30‐nm‐thick Si:O, Er films are amorphous layers deposited onto silicon substrates by chemical‐vapor deposition of SiH4 and N2O, doped by ion implantation with Er to a concentration up to ≊1.5 at. %, and annealed in a rapid thermal annealing furnace. The most intense electroluminescence is obtained in samples annealed at 400 °C in reverse bias under breakdown conditions and it is attributed to impact excitation of erbium by hot carriers injected from the Si into the Si:O, Er layer. The electrical characteristics of the diode are studied in detail and related to the electroluminescence characteristics. A lower limit for the impact excitation cross section of ≊6×10−16 cm2 is obtained.

The formation of p‐ and n‐type layers of semi‐insulating polycrystalline silicon has been investigated by implantation and diffusion of B, P, and As. At room temperature the material resistivity can be changed by more than six orders of magnitude for both p‐ and n‐type doping. A dramatic decrease of resistivity is observed for dopant concentrations above a threshold level which corresponds to the complete filling of midgap grain‐boundary traps. The determination of this critical concentration allows the evaluation of the donor and acceptor grain‐boundary trap densities which are found to lie in the range from 7 to 14×1012/cm2. The charged traps produce depletion layers and potential barriers at the grain boundaries; these barriers drive the free‐carrier motion under external fields. Above the threshold concentration, the barrier height decreases with the increasing concentration of active dopant, going from ≊0.5 eV to nearly 0 and correspondingly the resistivity drops down. Thermionic emission and tunneli...

The diffusion into a p‐type Si substrate of arsenic ions implanted into TiSi2 layers has been investigated for several thermal diffusion treatments in the 900–1100 °C temperature range. The drive‐in was performed using either a rapid thermal annealing system or a traditional furnace. Shallow (20–80‐nm depth) junctions were obtained with a high (1019–1020/cm3) dopant concentration at the silicide‐silicon interface. The amount of diffused arsenic atoms measured by Rutherford backscattering spectrometry increases linearly with the square root of the annealing time. A similar relation was found for the amount of electrically active arsenic, as measured by Van der Pauw structure in combination with anodic oxidation. The two quantities differ and the inactive dopants precipitate in the diffused layer as seen by transmission electron microscopy. This behavior might be associated to the high tensile stress induced by the silicide layer on the surface silicon region and to its influence on the solid solubility and...

An extensive study on the electrical properties of Si nanocrystals under dark and solar light exposure in AM1.5G conditions is presented. The nanostructures have been obtained through chemical vapor deposition of multilayers of ultrathin silicon rich oxide/SiO2 films and subsequent thermal annealing. The electrical data demonstrate that the current transport in such systems is mediated by tunnel effect, and the lowest effective energy barrier limiting the carrier transport has been found to be 1.7 eV, well below the value's of 3.1 eV and 4.7 eV of free electrons and holes, respectively, at the standard Si/silicon dioxide interface. Under AM1.5G solar light illumination the contribution of the photocarriers increases with the voltage and above 60 V shows a trend toward saturation. A quantitative explanation of this saturation is discussed. Moreover, the photocarrier generation rate in the nanocrystals averaged over the solar spectrum region is evaluated.

We study the phase transition from amorphous to face-centered-cubic (fcc) polycrystalline Ge2Sb2Te5 thin films. The transformation has the peculiar characteristic, still not well understood, of coexisting high transition rates at low annealing temperature (with grain growth velocities of the order of 1 nm/min at 140 degrees C) and large activation energies (about 2-2.5 eV). In this work all kinetic parameters governing the transition have been determined by in situ transmission electron microscopy analysis. They are thermally activated and consistently show large anomalies in the preexponential terms of transient and steady-state nucleation rates and grain growth rate. A possible explanation for these observations is described, based on a recently proposed atomic structure of the fcc Ge2Sb2Te5, characterized by a high level of disorder and distortion at the short range.

In this paper we review the subject of oxide breakdown (BD), focusing our attention on the case of the gate dielectrics of interest for current Si microelectronics, i.e., Si oxides or oxynitrides of thickness ranging from some tens of nanometers down to about 1 nm. The first part of the paper is devoted to a concise description of the subject concerning the kinetics of oxide degradation under high-voltage stress and the statistics of the time to BD. It is shown that, according to the present understanding, the BD event is due to a buildup in the oxide bulk of defects produced by the stress at high voltage. Defect concentration increases up to a critical value corresponding to the onset of one percolation path joining the gate and substrate across the oxide. This triggers the BD, which is therefore believed to be an intrinsic effect, not due to preexisting, extrinsic defects or processing errors. We next focus our attention on experimental studies concerning the kinetics of the final event of BD, during which the gate leakage increases above acceptable levels. In conditions of intrinsic BD, the leakage increase is due to the growth of damage within the oxide in localized regions. Observations concerning this damage are reviewed and discussed. The measurement of the current, voltage, and power dissipated during the BD transient are also reported and discussed in comparison with the data of structural damage. We then describe the current understanding concerning the dependence of the BD current transient on the conditions of electric field and voltage. In particular, as the oxide thickness and, as a consequence, the voltage levels used for accelerated reliability tests have decreased, the BD transient exhibits a marked change in behavior. As the stress voltage is decreased below a threshold value, the BD transient becomes slower. This recently discovered phenomenon has been termed progressive BD, i.e., a gradual growth of the BD spot and of the gate leakage, with a time scale that under operation conditions can be a large fraction of the total time to BD. We review the literature on this phenomenon, describing the current understanding concerning the dependence of the effect on voltage, temperature, oxide thickness, sample geometry, and its physical structure. We also discuss the possible relation to the so-called soft oxide BD mode and propose a simpler, more consistent terminology to describe different BD regimes. The last part of the paper is dedicated to exploratory studies, still at the early stages given the very recent subject, concerning the impact on the BD of materials for the metal-oxide-semiconductor gate stack and, in particular, metal gates.