Search

The EZ-FET is a device with simplified architecture and processing that enables fast electrical characterization of semiconductor films on insulators (SOI) with only two lithography levels and using regular process steps. For low temperature SOI substrates characterization, the EZ-FET must be processed at a low temperature, including the junctions formation, i.e., the dopant activation process. Two EZ-FET dopant activation approaches using nanosecond laser annealing at low thermal budget are presented in this work. The first is the classical process of partial source and drain amorphization followed by their recrystallization. The second is a simplified process consisting of full source and drain amorphization followed by recrystallization. Both approaches are evaluated through the analysis of the electrical behaviors of the resulting structures.

In this study, we have conclusively used UV-nanosecond laser annealing (UV-NLA) as an alternative to classical rapid thermal annealing (RTA) for the formation of stable Ni-GeSn alloys. The phase formation sequence was similar to the one obtained with RTA. At low laser energy densities (ED) and after the consumption of Ni, the Ni-rich phase, Ni5(GeSn)3, was first obtained. This phase was followed, for higher ED, by the mono-stanogermanide phase Ni(GeSn). Surface wrinkles appeared at high ED, resulting in a sheet resistance ( $\text{R}_{\text {sh}}$ ) increase. Meanwhile, $\text{R}_{\text {sh}}$ variations were mainly governed by the phases that were present at lower ED. By combining various analyses, we did not see any Ni(GeSn) agglomeration or Sn segregation. The use of UV-NLA yielded thermally stable Ni(GeSn) contact layers.

Abstract In this work, we present an on-chip 2D and 3D photonics integration solution compatible with Front End of Line integration (FEOL) using deposited polycrystalline silicon (poly:Si) for optical interconnects applications. Deposited silicon integration on a bulk silicon wafer is here discussed in all its processing steps and configurations. Moreover, results of deposited silicon high-Q Photonic Crystal (PhC) resonators are shown, demonstrating the possibility to employ optical resonators patterned on this material in the next generation of 2D and 3D integrated optical interconnects.

Abstract Ultraviolet Nanosecond Laser Annealing (LA) is a powerful tool for both fundamental investigations of ultrafast, nonequilibrium phase-change phenomena and technological applications (e.g., the processing of 3D sequentially integrated nano-electronic devices) where strongly confined heating and melting is desirable. Optimizing the LA process along with the experimental design is challenging, especially when involving complex 3D-nanostructured systems with various shapes and phases. To this purpose, it is essential to model critical nanoscale physical LA-induced phenomena, such as shape changes or formation and evolution of point and extended defects. To date, LA simulators are based on continuum models, which cannot fully capture the microscopic kinetics of a solid–liquid interface. In this work a fully atomistic LA simulation methodology is presented, based on the parallel coupling of a continuum, finite elements, μm-scale electromagnetic-thermal solver with a super-lattice Kinetic Monte Carlo atomistic model for melting. Benchmarks against phase-field models and experimental data validate the approach. LA of a Si(001) surface is studied varying laser fluence and pulse shape, assuming both homogeneous and inhomogeneous nucleation, revealing how liquid Si nuclei generate, deform and coalesce during irradiation. The proposed methodology is applicable to any system where the atom kinetics is determined by a strongly space- and time-dependent field, such as temperature or strain.

UV laser annealing (UV-LA) enables surface-localized high-temperature thermal processing to form abrupt junctions in emerging monolithically stacked devices, where the applicable thermal budget is restricted. In this work, UV-LA is performed to regrow a silicon-on-insulator wafer partially amorphized by arsenic ion implantation as well as to activate the dopants. In a microsecond scale ( $\sim 10^{-6}$ s to $\sim 10^{-5}$ s) UV-LA process, monocrystalline solid phase recrystallization and dopant activation without junction deepening are evidenced, thus opening various applications in low thermal budget integration flows. However, some concerns remain. First, the surface morphology is degraded after the regrowth, possibly because of the non-perfect uniformity of the used laser beam and/or the formation of defects near the surface involving the excess dopants. Second, many of the dopants are inactive and seem to form deep levels in the Si band gap, suggesting a further optimization of the ion implantation condition to manage the initial crystal damage and the heating profile to better accommodate the dopants into the substitutional sites.

Ante la perspectiva de que millones de personas en todo el mundo mueran por enfermedades crónicas no transmisibles, la comunidad científica reconoce el impacto en la salud mental de un diagnóstico de enfermedad crónica. Por eso, este estudio se propone describir la prevalencia de las enfermedades crónicas no transmisibles y los biomarcadores asociados al riesgo suicida. Para ello, se seleccionaron 27 artículos publicados entre el 2014 y 2020 de diversas bases de datos. Se encontró que las enfermedades más frecuentes asociadas al riesgo de suicidio fueron cáncer, hipertensión, enfermedad pulmonar obstructiva crónica, enfermedades inflamatorias intestinales, neumoconiosis y ooforectomía. En cuanto a los biomarcadores, se encontró que hay genes relacionados con el riesgo suicida en pacientes con enfermedades crónicas como el cáncer, enfermedades neurodegenerativas, diabetes y obesidad/colesterol. Otros factores de riesgo suicida se relacionaron con el inicio de la enfermedad en la adolescencia, el someterse a procedimientos quirúrgicos, quimioterapias, ser un hombre mayor de 65 años y ser soltero.

The solid phase recrystallization of partially amorphized SOI structures using a pulsed Ultra-Violet Nanosecond Laser Annealing (UV-NLA) is reported. It is shown that combining UV-NLA process with a heating chuck at low temperature (450 °C) results in the perfect recrystallization of the amorphized portion of the silicon layer. Actually, sub-melt multi-pulse UV-NLA enables obtaining the total crystal recovery and a very high dopant activation rate, comparable to melt laser annealing approaches or high temperature rapid thermal annealing, with a very low overall thermal budget. This approach is a great alternative to traditional solid phase epitaxial regrowth process, which reach it limits, in terms of recrystallization rate, at temperatures lower than 500 °C. The process presented here is thus suitable for integration paths in which the thermal budget must be limited as for example 3D sequential integration. Besides the high activation rate, another benefit of the solid phase recrystallization, compared to an equivalent laser anneal in the melt regime, is the almost unchanged surface roughness. Furthermore, the use of an in-situ metrology based on Time Resolved Reflectometry (TRR) enables the monitoring of the crystalline seed thickness evolution during UV-NLA and the estimation of the recrystallization rate.

We investigate the recrystallization of thick phosphorus-implanted GeSn layers using 308 nm Ultraviolet Nanosecond Laser Annealing (UV-NLA). We identify the optimal annealing conditions leading to the reconstruction of Ge0.92Sn0.08 crystal amorphized by dopant implantation. The fully recrystallized GeSn layers present specific structures with localized tin and strain variations. Above the non-amorphized and unmelted Ge0.92Sn0.08 seed layer, a first highly tensile strained GeSn sublayer is formed, with a tin gradient from 2.5% up to 10.5%. Closer to the surface, a second sublayer consists of tin-enriched vertical structures in a Ge0.93Sn0.07 matrix. Laser annealing enables us to reverse the strain of the GeSn layer. The initial GeSn presents a compressive strain of −0.10%, while the recrystallized Ge0.93Sn0.07 matrix is tensile strained at 0.39%. UV-NLA presents the advantages of (i) local annealing that recrystallizes amorphized GeSn layers after implantation without excessive tin segregation and (ii) reversing the strain of epitaxial GeSn layers from compressive to tensile. Our results open up promising perspectives for the integration of GeSn mid-IR photonic devices. [ABSTRACT FROM AUTHOR]

In this paper, we present an enhanced differential Hall effect measurement method (DHE) for ultrathin Si and SiGe layers for the investigation of dopant activation in the surface region with sub-nanometre resolution. In the case of SiGe, which constitutes the most challenging process, we show the reliability of the SC1 chemical solution (NH4OH/H2O2/H2O) with its slow etch rate, stoichiometry conservation and low roughness generation. The reliability of a complete DHE procedure, with an etching step as small as 0.5 nm, is demonstrated on a dedicated 20 nm thick SiGe test structure fabricated by CVD and uniformly doped in situ during growth. The developed method is finally applied to the investigation of dopant activation achieved by advanced annealing methods (including millisecond and nanosecond laser annealing) in two material systems: 6 nm thick SiGeOI and 11 nm thick SOI. In both cases, DHE is shown to be a uniquely sensitive characterisation technique for a detailed investigation of dopant activation in ultrashallow layers, providing sub-nanometre resolution for both dopant concentration and carrier mobility depth profiles.

A thorough study of the phosphorus (P) heavy doping of thin Silicon-On-Insulator (SOI) layers by UV nanosecond Laser Thermal Annealing (LTA) is presented in this work. As a function of the implant dose and laser annealing conditions, the melting regimes and regrowth processes, as well as the redistribution and activation of P in the top-Si amorphized layer, were investigated. The findings emphasize the critical role of the thin crystalline silicon layer that remains after the top-Si layer amorphizes, as it provides nucleation seeds for liquid phase recrystallization. The effect of the implant dose on the recrystallization process is thoroughly investigated in terms of melt energy thresholds, crystallographic nature of the resolidified layer, defect formation, surface roughness, and the formation of hillocks on the silicon surface. Optimized laser annealing conditions, corresponding to the laser energies just preceding the onset of the full melt, were identified for all implanted doses. Such optimized layers have perfect crystallinity, negligible P out-diffusion, a nearly perfectly flat P depth profile located below the segregation-induced surface pileup peak, and dopant active concentrations well above 1021 cm−3, which is close to the highest reported values for phosphorus in bulk Si substrates. [ABSTRACT FROM AUTHOR]

The Gambian and Malian fisheries and fish processing value chains are predominantly artisanal and represent a key source of protein and livelihoods, yet their eco-efficiency has not been studied to date. A Life Cycle Assessment was used to estimate the associated environmental impacts of those value chains and provide information on the eco-efficiency indicators, which relate technical efficiencies to environmental impacts. The results showed that industrial Gambian fleets’ fuel use efficiency is rather low as compared with the global mean fuel use intensity (landed fish/consumed fuel) for both small pelagics and demersal fish. In Mali, the fuel use intensity of motorised artisanal fisheries is lower than the mean values for artisanal inland fisheries in developing countries, but the important increase of frozen imported fish from fish farming multiplies the estimated impacts by four. The least energy-intensive fisheries (cast nets and stow nets in Gambia and opportunistic fishers in Mali) feature better eco-efficiency scores. Based on the identified sources of inefficiencies, we suggest improvements in the landing/processing infrastructure and fishing units’ engines, coupled with technical and business training and improved processing methods, to ameliorate seafood eco-efficiency and a stronger recognition of the importance of the artisanal fisheries subsector to overcome challenges and improving resource management.

The literature is increasing on how to prioritize climate-smart options with stakeholders but relatively few examples exist on how to co-design climate-smart farming systems with them, in particular with smallholder farmers. This article presents a methodological framework to co-design climate-smart farming systems with local stakeholders (farmers, scientists, NGOs) so that large-scale change can be achieved. This framework is based on the lessons learned during a research project conducted in Honduras and Colombia from 2015 to 2017. Seven phases are suggested to engage a process of co-conception of climate-smart farming systems that might enable implementation at scale: (1) “exploration of the initial situation,” which identifies local stakeholders potentially interested in being involved in the process, existing farming systems, and specific constraints to the implementation of climate-smart agriculture (CSA); (2) “co-definition of an innovation platform,” which defines the structure and the rules of functioning for a platform favoring the involvement of local stakeholders in the process; (3) “shared diagnosis,” which defines the main challenges to be solved by the innovation platform; (4) “identification and ex ante assessment of new farming systems,” which assess the potential performances of solutions prioritized by the members of the innovation platform under CSA pillars; (5) “experimentation,” which tests the prioritized solutions on-farm; (6) “assessment of the co-design process of climate-smart farming systems,” which validates the ability of the process to reach its initial objectives, particularly in terms of new farming systems but also in terms of capacity building; and (7) “definition of strategies for scaling up/out,” which addresses the scaling of the co-design process. For each phase, specific tools or methodologies are used: focus groups, social network analysis, theory of change, life-cycle assessment, and on-farm experiments. Each phase is illustrated with results obtained in Colombia or Honduras.