An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

Diffusion in silicon of elements from columns III and V of the Periodic Table is reviewed in theory and experiment. The emphasis is on the interactions of these substitutional dopants with point defects (vacancies and interstitials) as part of their diffusion mechanisms. The goal of this paper is to unify available experimental observations within the framework of a set of physical models that can be utilized in computer simulations to predict diffusion processes in silicon. The authors assess the present state of experimental data for basic parameters such as point-defect diffusivities and equilibrium concentrations and address a number of questions regarding the mechanisms of dopant diffusion. They offer illustrative examples of ways that diffusion may be modeled in one and two dimensions by solving continuity equations for point defects and dopants. Outstanding questions and inadequacies in existing formulations are identified by comparing computer simulations with experimental results. A summary of the progress made in this field in recent years and of directions future research may take is presented.

Point defects and dopant diffusion in silicon

New carrier mobility data for both arsenic- and boron-doped silicon are presented in the high doping range. The data definitely show that the electron mobility in As-doped silicon is significantly lower than in P-doped silicon for carrier concentrations higher than 1019cm-3. By integrating these data with those previously published, empirical relationships able to model the carrier mobility against carrier concentration in the whole experimental range examined to date (about eight decades in concentration) for As-, P-, and B-doped silicon are derived. Different parameters in the expression for the n-type dopants provide differentiation between the electron mobility in As-and in P-doped silicon. Finally, it is shown that these new expressions, once implemented in the SUPREM II process simulator, lead to reduced errors in the simulation of the sheet resistance values.

Modeling of carrier mobility against carrier concentration in arsenic-, phosphorus-, and boron-doped silicon

Implanted B and P dopants in Si exhibit transient enhanced diffusion (TED) during annealing which arises from the excess interstitials generated by the implant. In order to study the mechanisms of TED, transmission electron microscopy measurements of implantation damage were combined with B diffusion experiments using doping marker structures grown by molecular-beam epitaxy (MBE). Damage from nonamorphizing Si implants at doses ranging from 5×1012 to 1×1014/cm2 evolves into a distribution of {311} interstitial agglomerates during the initial annealing stages at 670–815 °C. The excess interstitial concentration contained in these defects roughly equals the implanted ion dose, an observation that is corroborated by atomistic Monte Carlo simulations of implantation and annealing processes. The injection of interstitials from the damage region involves the dissolution of {311} defects during Ostwald ripening with an activation energy of 3.8±0.2 eV. The excess interstitials drive substitutional B into electric...

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Physical mechanisms of transient enhanced dopant diffusion in ion-implanted silicon

Implanted B and P dopants in Si exhibit transient enhanced diffusion (TED) during initial annealing, due to Si interstitials being emitted from the region of the implant damage. The structural source of these interstitials has not previously been identified. Quantitative transmission electron microscopy measurements of extended defects are used to demonstrate that TED is caused by the emission of interstitials from specific defects. The defects are rodlike defects running along 〈110〉 directions, which consist of interstitials precipitating on {311} planes as a single monolayer of hexagonal Si. We correlate the evaporation of {311} defects during annealing at 670 and 815 °C with the length of the diffusion transient, and demonstrate a link between the number of interstitials emitted by the defects, and the flux of interstitials driving TED. Thus not only are {311} defects contributing to the interstitial flux, but the contribution attributable to {311} defect evaporation is sufficient to explain the whole ...

Implantation and transient B diffusion in Si: The source of the interstitials

Mesures par diffraction de rayons X et electriques sur des echantillons diversement dopes par implantation ionique et recuits par laser, apres traitement thermique a 800, 900 et 1000°C. Determination des profils de densites des porteurs: il y aurait precipitation de SiAs sous forme de disques minces

Precipitation as the Phenomenon Responsible for the Electrically Inactive Arsenic in Silicon

The precipitation and dissolution of monoclinic SiAs, in Si samples implanted with 1 and 1.5\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{As}}^{+}$/${\mathrm{cm}}^{2}$, was followed at 800, 900, and 1050 \ifmmode^\circ\else\textdegree\fi{}C by transmission electron microscopy (TEM) and secondary neutral mass spectrometry. It has been found that the concentration ${\mathit{C}}_{\mathrm{sat}}$ of mobile As, which diffuses after equilibration with the monoclinic SiAs precipitates, is given by ${\mathit{C}}_{\mathrm{sat}}$=1.3\ifmmode\times\else\texttimes\fi{}${10}^{23}$ exp(-0.42/kT) ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$, where kT is in eV. This saturation concentration includes different states of As in equilibrium with the monoclinic phase at the annealing temperatures, namely, (i) the electrically active and (ii) the inactive mobile dopant. The results presented in this paper indicate that the inactive As is in the form of clusters. The link between the clustering phenomenon and the presence of small particles detected by TEM observations is also discussed.

Precipitation, aggregation, and diffusion in heavily arsenic-doped silicon.

Lattice damage has been introduced in silicon wafers by silicon ion implantation at doses below and above amorphization threshold. In the first case, the annealing behavior of damage is consistent with the presence of amorphous islands near the surface and interstitial clusters in deeper regions. Unlike the former kind of defects, the temperature evolution of the latter strongly affects the diffusion of dopant atoms. Enhanced diffusion for dopant diffusing via interstitialcy mechanism accompanies in fact the interstitial cluster dissolution. The extent of this effect depends on the relative depth position of dopant and defects. When the local concentration of the interstitials increases (e.g., as a consequence of an implant made with the same dose, but with a lower energy) defect clustering begins to compete with their recovery, which makes the fraction of interstitials available for dopant diffusion smaller. Interstitial clustering is the dominant process occurring during annealing at the original amorph...

Some aspects of damage annealing in ion-implanted silicon: Discussion in terms of dopant anomalous diffusion

Supersaturated solutions of phosphorus in silicon were obtained by ion implantation and pulsed ruby laser annealing. The dependence of electron mobility and electrical resistivity on carrier density was accurately determined by Hall effect and resistivity measurements. Maximum dopant concentration was , corresponding to a resistivity of 110 μΩ cm and to an electron mobility of 11 cm2/V sec. The stability of these alloys was analyzed by isochronal and isothermal annealing. In the more heavily doped samples a remarkable deactivation of the dopant was verified also for thermal treatments of 1 hr at 300°C. TEM examinations showed a large amount of precipitates with density and size depending on supersaturation. Finally it was observed that the electron mobility depends only on the carrier density and is unaffected by the electrically inactive phosphorus, even when present at very high concentrations.

Electrical Properties and Stability of Supersaturated Phosphorus‐Doped Silicon Layers

The transient enhanced diffusion (TED) of As in silicon samples implanted at 35 keV with dose 5×1015 cm−2 has been investigated in the temperature range between 750 and 1030 °C by comparing experimental and simulated profiles. For temperatures higher than 900 °C the phenomenon is of modest entity and vanishes after a few seconds, whereas at lower temperatures diffusivity enhancements of some order of magnitude have been observed. The anomalous shift of the junction depth, evaluated at 2×1018 cm−3, is about 12 nm at 900 °C and increases up to 45 nm at 750 °C. It has been verified that the two are the contributions, that generate the interstitial excess responsible for the TED: (i) the implantation damage and (ii) the aggregation in clusters of the As atoms. From an experiment that allows us to separate the two contributions, we estimate that about one third of the TED observed in the first 20 min of annealing at 800 °C is due to the defects produced by clustering. The influence of clustering on the shape o...

Sandro Solmi

Papers

Precipitation as the Phenomenon Responsible for the Electrically Inactive Arsenic in Silicon

Precipitation, aggregation, and diffusion in heavily arsenic-doped silicon.

Some aspects of damage annealing in ion-implanted silicon: Discussion in terms of dopant anomalous diffusion

Electrical Properties and Stability of Supersaturated Phosphorus‐Doped Silicon Layers

Transient enhanced diffusion of arsenic in silicon