Activation Energy for the Post Implantation Annealing of 1019 cm-3 and 1020 cm-3 Ion Implanted Al in 4H SiC
TL;DR: In this article, the activation energy for the electrical activation of 1x1019 cm-3 and 1x1020 cm -3 ion implanted Al in 4H-SiC has been estimated.
Abstract: The activation energy for the electrical activation of 1x1019 cm-3 and of 1x1020 cm-3 ion implanted Al in 4H-SiC has been estimated. Ion implantation temperature and dose rate were in the range 430-500°C and around 1011 cm2s-1, respectively. Post implantation annealing temperatures varied between 1500 °C and 1950 °C. The annealing time per each annealing temperature was sufficiently long that the sheet resistance of the implanted layer could be equal to the stationary value at the applied annealing temperature. The Arrhenius plots of the room temperature sheet resistances with respect to the post implantation annealing temperatures featured an exponential trend for both the implanted Al concentrations. The activation energies of these plots are the activation energy for placing an implanted Al atom in a substitutional site, i.e. the electrical activation energy. Activation energies around 1 eV, equal within errors for the two implanted Al concentrations, were found.
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TL;DR: In this article, the microstructure, composition, as well as anti-oxidation performance of Al-doped SiC coatings with different preparation temperatures (1500-2100°C) were explored.
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TL;DR: A combination of low roughness parameter and high correlation length identify the transition from ripples to jagged morphology.
Abstract: The root mean square (rms) surface roughness extracted from atomic force microscopy is widely employed to complement the characterisation of ion implantation processes in 4H-SiC. It is known that the protection of a carbon film eliminates or mitigates roughening of the SiC surface during postimplantation annealing. This study, based on a rich original data collection of Al+ ion implanted 4H-SiC samples, allows for a quantitative description of the surface morphology as a function of the annealing temperature and time and of the Al implanted concentration. With increasing thermal budget, the evolution from flat, to blurred with ripples, granular, and finally jagged surface, results in a monotonous increase in the root mean square roughness. Additional information is given by the trends of the roughness exponent and of the correlation length, extracted from the height-height correlation function, which account for the surface evolution below 1700°C and for the effect of the Al implanted concentration on the ripple size, respectively. A combination of low roughness parameter and high correlation length identify the transition from ripples to jagged morphology. LAY DESCRIPTION: Selective area doping is a key step in the fabrication of hexagonal Silicon Carbide (4H-SiC) power electronic devices. It is achieved by ion implantation followed by a high temperature postimplantation annealing to restore the lattice and electrically activate the dopants. Aluminium, the preferred p-type dopant, is electrically activated at temperature ranging between 1500°C and 2000°C. The time required to complete the activation process is longer the lower the annealing temperature, spanning between some minutes and hundreds of hours. During annealing, 4H-SiC wafers are encapsulated by a temperature-resistant carbon layer (C-cap) in order to avoid step bunching and reduce surface roughening. Nevertheless, surface modifications can occur at high temperature. For this reason, the characterisations of 4H-SiC doping processes report not only the electrical activation of the dopants, but also the root mean square surface roughness obtained at the end of the process. However, rms values can be scattered because technological parameters such as the heating system and the way to deposit and remove the C-cap can affect the final result as well as the process parameters. Furthermore, the C-cap resistance to long annealing has been proven only by electrical measurements, but the surface morphology has never been observed. This work presents a quantitative characterisation of the surface morphology of Al implanted 4H-SiC as a function of the annealing temperature, time and of the Al implanted concentration, independent of the heating system and of the C-cap technology. The produced sample collection allowed to correlate characteristic surface features with the corresponding quantities extracted from image analysis that can be more sensitive to process parameters than the sole rms. These findings can be used to enrich process optimisation tools.
7 citations
Cites background from "Activation Energy for the Post Impl..."
...As an example, very long annealing at low temperature is needed to activate ion implanted Al in heteroepitaxial 3C-SiC, where the annealing temperature is limited by the melting point of the Si substrate (Nipoti et al., 2019)....
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TL;DR: The dependence on the annealing temperature, T a n n , of the Al asymptotic substitutional fraction φ ∞ in implanted silicon carbide (4H-SiC) is addressed from a statistical mechanical point of view in this article .
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Book•
23 Sep 2014
TL;DR: A comprehensive introduction and up-to-date reference to SiC power semiconductor devices covering topics from material properties to applications is provided in this paper. But the authors focus on the SiC Schottky barrier diodes (SBDs) and do not provide an in-depth reference for scientists and engineers working in this field.
Abstract: A comprehensive introduction and up-to-date reference to SiC power semiconductor devices covering topics from material properties to applications Based on a number of breakthroughs in SiC material science and fabrication technology in the 1980s and 1990s, the first SiC Schottky barrier diodes (SBDs) were released as commercial products in 2001. The SiC SBD market has grown significantly since that time, and SBDs are now used in a variety of power systems, particularly switch-mode power supplies and motor controls. SiC power MOSFETs entered commercial production in 2011, providing rugged, high-efficiency switches for high-frequency power systems. In this wide-ranging book, the authors draw on their considerable experience to present both an introduction to SiC materials, devices, and applications and an in-depth reference for scientists and engineers working in this fast-moving field . Fundamentals of Silicon Carbide Technology covers basic properties of SiC materials, processing technology, theory and analysis of practical devices, and an overview of the most important systems applications. Specifically included are:
658 citations
21 Oct 2005
628 citations
01 Dec 2005
Abstract: DESCRIPTION This Third Edition updates a landmark text with the latest findings The Third Edition of the internationally lauded Semiconductor Material and Device Characterization brings the text fully up-to-date with the latest developments in the field and includes new pedagogical tools to assist readers. Not only does the Third Edition set forth all the latest measurement techniques, but it also examines new interpretations and new applications of existing techniques.
465 citations
TL;DR: In this paper, a pyrolyzed photoresist film called carbon-cap (C-cap) is used as a protective cap of the surface of ion-implanted 4H-SiC wafers during the postimplantation annealing process with the aim to prevent Si sublimation and step bunching formation.
Abstract: A pyrolyzed photoresist film is commonly used as a protective cap of the surface of ion-implanted 4H-SiC wafers during the postimplantation annealing process with the aim to prevent Si sublimation and step bunching formation. Such a film that is called carbon-cap (C-cap) is always removed after postimplantation annealing and before any other processing step of the SiC wafer. Here, we show that this C-cap is a continuous, hard, black, mirrorlike, and planar thin film that can be patterned by a reactive ion etching O 2 -based plasma for the fabrication of ohmic contact pads on both Al + - and P + -implanted 4H-SiC. This C-cap material has an electrical resistivity of 1.5 × 10 -3 Ω cm and a good resistance against scratch. Al (1% Si) wires can be ultrasonically bonded on the C-cap pads. Such a bonding and the C-cap adhesion to the implanted 4H-SiC surface are stable for electrical characterizations in vacuum between room temperature and 450°C. The measured specific contact resistance of the C-cap on a 1 × 10 20 cm -3 p+-implanted 4H-SiC is 9 × 10- 5 Ω cm 2 at room temperature. Micro-Raman characterizations show that this C-cap is formed of a nanocrystalline graphitic phase.
55 citations
20 citations