Papers by Author: Danilo Crippa

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Authors: Thomas Kreiliger, Marco Mauceri, Marco Puglisi, Fulvio Mancarella, Francesco La Via, Danilo Crippa, Wlodek Kaplan, Adolf Schöner, Anna Marzegalli, Leo Miglio, Hans von Känel
Abstract: The growth morphology of epitaxial 3C-SiC crystals grown on hexagonal pillars deeply etched into Si (111) substrates is presented. Different growth velocities of side facets let the top crystal facet evolve from hexagonal towards triangular shape during growth. The lateral size and separation between Si pillars determine the onset of fusion between neighboring crystals during growth at a height tailoring of which is crucial to reduce the stacking fault (SF) density of the coalesced surface. Intermediate partial fusion of neighboring crystals is shown as well as a surface of fully coalesced crystals.
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Authors: Francesco La Via, Fabrizio Roccaforte, Antonino La Magna, Roberta Nipoti, Fulvio Mancarella, Peter J. Wellmann, Danilo Crippa, Marco Mauceri, Peter Ward, Leo Miglio, Marcin Zielinski, Adolf Schöner, Ahmed Nejim, Laura Vivani, Rositza Yakimova, Mikael Syväjärvi, Gregory Grosset, Frank Torregrosa, Michael Jennings, Philip A. Mawby, Ruggero Anzalone, Salvatore Coffa, Hiroyuki Nagasawa
Abstract: The cubic polytype of SiC (3C-SiC) is the only one that can be grown on silicon substrate with the thickness required for targeted applications. Possibility to grow such layers has remained for a long period a real advantage in terms of scalability. Even the relatively narrow band-gap of 3C-SiC (2.3eV), which is often regarded as detrimental in comparison with other polytypes, can in fact be an advantage. However, the crystalline quality of 3C-SiC on silicon has to be improved in order to benefit from the intrinsic 3C-SiC properties. In this project new approaches for the reduction of defects will be used and new compliance substrates that can help to reduce the stress and the defect density at the same time will be explored. Numerical simulations will be applied to optimize growth conditions and reduce stress in the material. The structure of the final devices will be simulated using the appropriated numerical tools where new numerical model will be introduced to take into account the properties of the new material. Thanks to these simulations tools and the new material with low defect density, several devices that can work at high power and with low power consumption will be realized within the project.
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Authors: Hans von Känel, Leo Miglio, Danilo Crippa, Thomas Kreiliger, Marco Mauceri, Marco Puglisi, Fulvio Mancarella, Ruggero Anzalone, Nicolo’ Piluso, Francesco La Via
Abstract: The heteroepitaxial growth of 3C-SiC on Si (001) and Si (111) substrates deeply patterned at a micron scale by low-pressure chemical vapor deposition is shown to lead to space-filling isolated structures resulting from a mechanism of self-limitation of lateral expansion. Stacking fault densities and wafer bowing may be drastically reduced for optimized pattern geometries.
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Authors: Francesco La Via, Fabrizio Roccaforte, Salvatore di Franco, Alfonso Ruggiero, L. Neri, Ricardo Reitano, Lucia Calcagno, Gaetano Foti, Marco Mauceri, Stefano Leone, Giuseppe Pistone, Giuseppe Abbondanza, Gian Luca Valente, Danilo Crippa
Abstract: The effects of the Si/H2 ratio on the growth of the epitaxial layer and on the epitaxial defects was studied in detail. A large increase of the growth rate has been observed with the increase of the silicon flux in the CVD reactor. Close to a Si/H2 ratio of 0.05 % silicon nucleation in the gas phase occurs producing a great amount of silicon particles that precipitate on the wafers. The epitaxial layers grown with a Si/H2 ratio of 0.03% show a low defect density and a low leakage current of the Schottky diodes realized on these wafers. For these diodes the DLTS spectra show thepresence of several peaks at 0.14, 0.75, 1.36 and 1.43 eV. For epitaxial layers grown with higher values of the Si/H2 ratio and then with an higher growth rate, the leakage current of the Schottky diodes increases considerably.
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Authors: Massimo Camarda, Stefania Privitera, Ruggero Anzalone, Nicolò Piluso, Patrick Fiorenza, Alessandra Alberti, Giovanna Pellegrino, Antonino La Magna, Francesco La Via, Carmelo Vecchio, Marco Mauceri, Grazia Litrico, Antonino Pecora, Danilo Crippa
Abstract: In this paper we investigate the role of the growth rate (varied by changing the Si/H2 ratio and using TCS to avoid Si droplet formation) on the surface roughness (Rq), the density of single Shockley stacking faults (SSSF) and 3C-inclusions (i.e. epi-stacking faults, ESF). We find that optimized processes with higher growth rates allow to improve the films in all the considered aspects. This result, together with the reduced cost of growth processes, indicates that high growth rates should always be used to improve the overall quality of 4H-SiC homoepitaxial growths. Furthermore we analyze the connection between surface morphology and density of traps (Dit) at the SiO2/SiC interface in fabricated MOS devices finding consistent indications that higher surface roughness (step-bunched surfaces) can improve the quality of the interface by reducing the Dit value.
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Authors: Francesco La Via, Nicolo’ Piluso, Patrick Fiorenza, Marco Mauceri, Carmelo Vecchio, Antonino Pecora, Danilo Crippa
Abstract: In this work a new epitaxial process on 6 inches has been performed on 2° off-cut substrate. This off-cut will reduce the material loss during substrate preparation from the crystal boule. The thickness and doping uniformity of the samples grown in the LPE reactor PE1O6 is extremely good and the PL map shows a low defects density. The roughness is slightly higher on 2° off-cut and the process window becomes narrower.
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Authors: Francesco La Via, G. Galvagno, A. Firrincieli, Fabrizio Roccaforte, Salvatore di Franco, Alfonso Ruggiero, Milo Barbera, Ricardo Reitano, Paolo Musumeci, Lucia Calcagno, Gaetano Foti, Marco Mauceri, Stefano Leone, Giuseppe Pistone, F. Portuese, Giuseppe Abbondanza, Giovanni Abagnale, Gian Luca Valente, Danilo Crippa
Abstract: The growth rate of 4H-SiC epi layers has been increased by a factor 3 (up to 18μm/h) with respect to the standard process with the introduction of HCl in the deposition chamber. The epitaxial layers grown with the addition of HCl have been characterized by electrical, optical and structural characterization methods. An optimized process without the addition of HCl is reported for comparison. The Schottky diodes, manufactured on the epitaxial layer grown with the addition of HCl at 1600 °C, have electrical characteristics comparable with the standard epitaxial process with the advantage of an epitaxial growth rate three times higher.
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Authors: Francesco La Via, Massimo Camarda, Andrea Canino, Andrea Severino, Antonino La Magna, Marco Mauceri, Carmelo Vecchio, Danilo Crippa
Abstract: In this paper the epitaxial process with chloride precursors has been described. In particular it has been shown that the growth rate can be increased to about 100 μm/h but higher growth rate can be difficult to reach due to the limited surface diffusion at the usual temperature of SiC epitaxy. This process gives several advantages because it gives the opportunity to increase the throughput and consequently to reduce the cost of epitaxy, using new reactor structures, and to reduce several kind of defects (Basal Plane Dislocations, Stacking Faults, Threading Dislocations) and to decrease the surface roughness at the same time.
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Authors: Maurizio Masi, Alessandro Veneroni, A. Fiorucci, Francesco La Via, Gaetano Foti, Marco Mauceri, Stefano Leone, Giuseppe Pistone, Giuseppe Condorelli, Giuseppe Abbondanza, Gian Luca Valente, Danilo Crippa
Abstract: A simplified deposition model, involving both the description of the deposition and of the film morphology was adopted to quantitatively understand the experimental trends encountered in the epitaxial silicon carbide deposition in an industrial hot wall reactor. The attention was focused on the system involving chlorinated species because its really superior performances with respect the traditional silane/hydrocarbons process. The evolution of the crystalline structure (i.e., from poly to single) and of the surface roughness can be understood by simply comparing two characteristic times, like those inherent the surface diffusion and the matter supply to the surface.
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Authors: Danilo Crippa, Gian Luca Valente, Alfonso Ruggiero, L. Neri, Ricardo Reitano, Lucia Calcagno, Gaetano Foti, Marco Mauceri, Stefano Leone, Giuseppe Pistone, Giuseppe Abbondanza, G. Abbagnale, Alessandro Veneroni, Fabrizio Omarini, L. Zamolo, Maurizio Masi, Fabrizio Roccaforte, G. Giannazzo, Salvatore di Franco, Francesco La Via
Abstract: The results of a new epitaxial process using an industrial 6x2” wafer reactor with the introduction of HCl during the growth have been reported. A complete reduction of silicon nucleation in the gas phase has been observed even for high silicon dilution parameters (Si/H2>0.05) and an increase of the growth rate until about 20 µm/h has been measured. No difference has been observed in terms of defects, doping uniformity (average maximum variation 8%) and thickness uniformity (average maximum variation 1.2 %) with respect to the standard process without HCl.
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