Laser Systems & Solutions of Europe (France)

Pulsed laser annealing (PLA) offers significant advantages over conventional thermal processes for semiconductor device fabrication. Notably, it can provide ultrafast (~ns) and high-temperature (>1000 °C) profiles. When the maximum temperature exceeds the melting point, a solid-to-liquid phase transition occurs, followed immediately by rapid recrystallization. Power devices, such as insulated-gate bipolar transistors (IGBTs), require micrometer-sized junctions that are used as injection layers (collectors) on the back side of processed wafers. PLA, when used at high laser energy densities, proved to be an attractive technique for this application because it provides the appropriate thermal budget while avoiding damage to the front side of the device. However, this unique annealing mechanism raises questions about dopant diffusion and residual defects in the recrystallized region and just below it. Indeed, these energy densities (ED) have been shown to promote the incorporation of complex impurities from the surface and the creation of defects at the liquid/solid interface. This article reports on the impact of laser annealing at high energy densities (ranging from 1.7 to 8.0 J/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) and multipulse modes (between 1 and 10) on leakage current and capacitance-deep level transient spectroscopy (C-DLTS) measurements using Schottky and p–n diodes. Our results suggest that the solubility of vacancies in silicon is fixed by the maximum temperature reached and the ED. Increasing the number of laser pulses enables one to reach the maximum vacancy concentration and promote diffusion toward the surface. Concurrently, the diffusion of complex impurities into the melted region enables coupling between the two defect types, creating trap centers responsible for degrading the leakage current.

This research paper presents a sensor fusion methodology aimed at improving the accuracy and reliability of navigation systems in civil and general aviation, particularly during approach and landing. The objective is to provide sufficient accuracy required to perform automated landing which is a major goal for leading aviation companies like Airbus. The conventional INS/GPS solution has limitations due to weaknesses in GPS, exacerbated by challenging environmental conditions and increasing air traffic. The proposed methodology combines data from gyroscopes and accelerometers as inertial references, GPS as the primary observer, and Radio Altimeter (RA) and Instrument Landing System (ILS) as backup observer sensors when GPS is unreliable. An extended Kalman filter was developed and optimized using ground truth datasets to process the diverse sensor data. In addition, validation of the methodology was conducted using an X-plane plugin to simulate various landing scenarios at Montréal-Mirabel International Airport (CYMX) on runway 06. The results demonstrated improved positioning accuracy during the landing phase compared to the conventional INS/GPS solution, with a 50% enhancement in overall 3D positioning accuracy. The fusion approach offers several advantages over alternatives. It requires minimal hardware modifications to aircraft and airports, making it a cost-effective solution. Furthermore, it relies on radio avionic signals, reducing dependence on environmental conditions compared to vision-based solutions.

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 applicable thermal budget is restricted. In this work, UV-LA is performed to regrow a SOI layer partially amorphized by arsenic ion implantation and to activate the dopants. In a microsecond scale (~10^-6 s to ~10^-5 s) UV-LA process, monocrystalline solid phase recrystallization and dopant activation without junction deepening is evidenced, thus opening various applications in low thermal budget integration flows.

Explosive crystallization (EC) is often observed when using nanosecond-pulsed melt laser annealing (MLA) in amorphous silicon (Si) and germanium (Ge). The solidification velocity in EC is so fast that a diffusion-less crystallization can be expected. In the contacts of advanced transistors, the active level at the metal/semiconductor Schottky interface must be very high to achieve a sub-10−9 ohm·cm2 contact resistivity, which has been already demonstrated by using the dopant surface segregation induced by MLA. However, the beneficial layer of a few nanometers at the surface may be easily consumed during subsequent contact cleaning and metallization. EC helps to address such kind of process integration issues, enabling the optimal positioning of the peak of the dopant chemical profile. However, there is a lack of experimental studies of EC in heavily-doped semiconductor materials. Furthermore, to the best of our knowledge, dopant activation by EC has never been experimentally reported. In this paper, we present dopant redistribution and activation by an EC process induced by UV nanosecond-pulsed MLA in heavily gallium (Ga) ion-implanted high Ge content SiGe. Based on the obtained results, we also highlight potential issues of integrating EC into real device fabrication processes and discuss how to manage them.

Explosive crystallization is a well known phenomenon occurring due to the thermodynamic instability of strongly under-cooled liquids, which is particularly relevant in pulsed laser annealing processes of amorphous semiconductor materials due to the globally exothermic amorphous-to-liquid-to-crystal transition pathway. In spite of the assessed understanding of this phenomenon, quantitative predictions of the material kinetics promoted by explosive crystallization are hardly achieved due to the lack of a consistent model able to simulate the concurrent kinetics of the amorphous-liquid and liquid-crystal interfaces. Here, we propose a multi-well phase-field model specifically suited for the simulation of explosive crystallization induced by pulsed laser irradiation in the nanosecond time scale. The numerical implementation of the model is robust despite the discontinuous jumps of the interface speed induced by the phenomenon. The predictive potential of the simulations is demonstrated by means of comparisons of the modelling predictions with experimental data in terms of in situ reflectivity measurements and ex-situ micro-structural and chemical characterization.

Atomic scale surface preparation, e.g. atomic layer etching, cleaning, local surface modifications and selective area deposition, becomes increasingly important for device scaling at sub-10 nm technology nodes in order to meet more stringent process variations and the highly selective process requirements. In the fully self-aligned via process, a topography is created by recess etching the underlying metal (copper) layer using chemical mixtures. In addition to a high compatibility with the materials exposed, one of the key requirements is to control the copper recessing such that the change in its roughness is kept at a minimum. The fundamental understanding and control of the polycrystalline surface reactions and interactions at the atomic scale are needed. In this paper, we will demonstrate the copper recess process for atomic layer wet etching (ALWE) with combination of laser thermal annealing (LTA) for surface smoothening.

We present the extension of variational Monte Carlo (VMC) to the calculation of electronic excitation energies and oscillator strengths using time-dependent linear-response theory. By exploiting the analogy existing between the linear method for wave-function optimisation and the generalised eigenvalue equation of linear-response theory, we formulate the equations of linear-response VMC (LR-VMC). This LR-VMC approach involves the first-and second-order derivatives of the wave function with respect to the parameters. We perform first tests of the LR-VMC method within the Tamm-Dancoff approximation using single-determinant Jastrow-Slater wave functions with different Slater basis sets on some singlet and triplet excitations of the beryllium atom. Comparison with reference experimental data and with configuration-interaction-singles (CIS) results shows that LR-VMC generally outperforms CIS for excitation energies and is thus a promising approach for calculating electronic excited-state properties of atoms and molecules.

Two new processes for deep junction formation have been demonstrated with low thermal budget UV excimer laser annealing using the melting regime: (i) in-depth controllable activation after high energy implantation and (ii) diffusion and recrystallization after heavily-doped Si deposition.

Proprotein convertases (PCSKs) are conserved among species and involved in processing of MMPs and growth factors, but poorly characterised in atherosclerosis. Previously we demonstrated upregulation of PCSK6 in a large cohort of plaques from symptomatic vs. asymptomatic patients. This protease localized to smooth muscle cells (SMCs) and showed a positive correlation to markers of inflammation, extracellular matrix remodeling and cytokines in plaques. Here we aimed at elucidating its role in vascular development and disease. In zebrafish embryos PCSK6 localized to heart and vasculature and its ablation caused defective peripheral vascular patterning with cerebral and myocardial hemorrhage. Increased expression of PCSK6 in vascular pathologies was validated by microarrays from carotid plaques vs. undiseased arteries (n=32 patients, p&lt;0.0001), abdominal (AAA, n=14, p&lt;0.0001) and thoracic aortic aneurysms (TAA, n=244, p=0.012). By immunohistochemistry, PCSK6 localized mainly to SMCs in the fibrous cap and neo-vessels in plaques, AAA and TAA tissues. Investigation of mouse carotid ligation, rat artery balloon injury and human restenosis tissues with pronounced intimal hyperplasia confirmed induction of PCSK6 in proliferating SMCs. By microarrays following progression of rat carotid injury, PCSK6 was downregulated in early phases defined by inflammatory pathways, while upregulated in later phases with SMCs activation and localized in SMCs. Expression of PCSK6 in this model was positively correlated to PDGFB and IGF1 (Spearman r&gt;0.7, p&lt;0.0001). PCSK6 overexpression in SMCs in vitro increased their migration in a wound-healing assay, especially upon PDGFBB stimulation. By eQTL analyses several polymorphisms in the PCSK6 gene were found to influence its expression in plaques and aneurysm tissue. Among these, rs6598465 showed association with maximum progression of arterial intima-media thickness in high-risk coronary artery disease subjects (n=3400, p=0.037). We identified a functional link between elevated expression of PCSK6 and vascular remodeling characterized by SMC activation. The present study establishes PCSK6 as one of the key modulators of pathological processes in relation to plaque vulnerability.