Massimo Camarda - Academia.edu (original) (raw)

Papers by Massimo Camarda

Materials Science Forum, 2009

The choice of off-axis (111) Si substrates is poorly reported in literature despite of the abilit... more The choice of off-axis (111) Si substrates is poorly reported in literature despite of the ability of such an oriented Si substrate in the reduction of stacking faults generation and propagation. The introduction of off-axis surface would be relevant for the suppression of incoherent boundaries. We grew 3C-SiC films on (111) Si substrates with a miscut angle from 3° to 6° along <110> and <11 2 >. The film quality was proved to be high by X-Ray diffraction (XRD) characterization. Transmission electron microscopy was performed to give an evaluation of the stacking fault density while pole figures were conducted to detect microtwins. Good quality single crystal 3C-SiC films were finally grown on 6 inch off-axis (111)Si substrate. The generated stress on both 2 and 6 inch 3C-SiC wafers has been analyzed and discussed.

Materials Science Forum, 2009

We discuss the possible source of surface instabilities (with specific reference to the step bunc... more We discuss the possible source of surface instabilities (with specific reference to the step bunching phenomena) during the growth of cubic and hexagonal Silicon Carbide polytypes. For this analysis we use: results from superlattice Kinetic Monte Carlo simulations, atomic force microscope surface analysis and literature data. We show that only hexagonal polytypes with misorientation cut toward the <11-20> direction suffer "intrinsically" the step bunching phenomena (i.e. it is present, independently on the growth conditions) whereas cubic polytypes and hexagonal ones with misorientation cut toward the <10-10> direction do not.

A novel Monte Carlo kinetic model has been developed and implemented to predict growth rate regim... more A novel Monte Carlo kinetic model has been developed and implemented to predict growth rate regimes and defect formation for the homo-epitaxial growth of various SiC polytypes on different substrates. Using this model we have studied the generation of both point like and extended defects in terms of the growth rate and off-cut angle, finding qualitative agreement with both electrical and optical characterization and analytical results.

Silicon Carbide and Related Materials 2009, Pts 1 and 2, 2010

In this article, using Kinetic Monte simulations on super-lattices, we study the evolution of ext... more In this article, using Kinetic Monte simulations on super-lattices, we study the evolution of extended defects during epitaxial growth. Specifically we show that, in the case of misoriented, close-packed substrates, a single-layer stacking fault can either extend throughout the entire epilayer (i.e. extended from the substrate up to the surface) or close in a dislocation loop depending on the deposition conditions and the crystallographic structure of the exposed surface containing the defect. We explain this behaviour in terms of a surface kinetic competition between the defect and the surrounding, perfect crystal: if the growth rate of the defect is higher compared to the growth rate of the surrounding crystal the defect will expand, otherwise it will close. This physical mechanism allows us to explain several experimental results of homo-and heteroepitaxy.

Silicon Carbide and Related Materials 2009, Pts 1 and 2, 2010

The fabrication of SiC MEMS-based sensors requires new processes able to realize microstructures ... more The fabrication of SiC MEMS-based sensors requires new processes able to realize microstructures on either bulk material or on the SiC surface. The hetero-epitaxial growth of 3C-SiC on silicon substrates allows one to overcome the traditional limitations of SiC microfabrication. In this work a comparison between single crystal and poly crystal 3C-SiC micromachined structures will be presented. The free-standing structures realized (cantilevers and membrane) are also a suitable method for residual field stress investigation in 3C-SiC films. Measurement of the Raman shift indicates that the mono and poly-crystal 3C-SiC structures release the stress in different ways. Finite element analysis was performed to determine the stress field inside the films and provided a good fit to the experimental data. A comprehensive experimental and theoretical study of 3C-SiC MEMS structures has been performed and is presented.

Materials Science Forum - MATER SCI FORUM, 2010

Growth of 3C-SiC films on an off-axis (111) Si substrate, with a miscut of 4° towards the <110> d... more Growth of 3C-SiC films on an off-axis (111) Si substrate, with a miscut of 4° towards the <110> direction, is here reported. An extensive material characterization has been conducted by means of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and Raman spectroscopy, indicating a very promising film quality with extremely flat surface and interface. Notwithstanding the excellent film quality, the wafer bow is still limiting its full employment in device realization.

Silicon Carbide and Related Materials 2010, 2011

Materials Science Forum, 2011

Materials Science Forum, 2012

Using several characterization techniques (µ-Raman, mechanical profilometer and microstructure de... more Using several characterization techniques (µ-Raman, mechanical profilometer and microstructure deflections) together with a recent stress model [1] we study the heteroepitaxial growth of cubic silicon carbide on silicon (100). We find that the observed inconsistency between experimental results might be the result of defects generated on the silicon substrate during the carbonization process. In such a situation wafer curvature techniques do not allow the determination of the stress field in the grown films.

Materials Science Forum, 2013

we study the surface morphology of homoepitaxially grown 4H silicon carbide in terms of growth ra... more we study the surface morphology of homoepitaxially grown 4H silicon carbide in terms of growth rate, miscut direction of the substrate and post growth argon thermal annealings. All the results indicate that the final surface morphology is the result of a competition between energetic reorganization and kinetic randomness. Because in all observed conditions energetic reorganization favors surface ondulations ("step bunching"), out-of-equilibrium conditions are one of the keys to favor the reduction of the surface roughness to values below ~0.5 nm. We theoretically support these results using kinetics superlattice Monte Carlo simulations (KslMC).

Materials Science Forum, 2012

In this article we compare the strain distribution observed in 3C-SiC/Si(100) cantilevers, using ... more In this article we compare the strain distribution observed in 3C-SiC/Si(100) cantilevers, using the shift of the transverse optical (TO) mode in micro-Raman maps, with the values predicted using a recent analytic theory [1]. By taking advantage of an under etching of the microstructures during the fabrication processes, that removes a thin layer of highly defective SiC close to the film/substrate interface near the edges of the microstructures, we show that the variation of the experimental measured strain can be ascribed to a non-linearity of the strain field along the 3C-SiC film thickness.

Materials Science Forum, 2010

Single Shockley faults have been studied in 4H-SiC epitaxial layers by using a spatial resolved m... more Single Shockley faults have been studied in 4H-SiC epitaxial layers by using a spatial resolved micro-photoluminescence technique. In particular the Effect of the UV pumping laser has been investigated. We demonstrated that high power density exposition at 325 nm affects drastically the structural properties of the epitaxial layers leading to a growth of this defect. We also demonstrated that by opportunely tuning the power density of the UV laser on the sample it is possible to analyze a wide area without producing any negative effect.

Materials Science Forum, 2014

In this paper we investigate the role of the growth rate (varied by changing the Si/H 2 ratio and... more In this paper we investigate the role of the growth rate (varied by changing the Si/H 2 ratio and using TCS to avoid Si droplet formation) on the surface roughness (R q ), 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 (D it ) at the SiO 2 /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 D it value.

Surface Science, 2010

Three dimensional kinetic Monte Carlo simulations on super-lattices are applied to study the evol... more Three dimensional kinetic Monte Carlo simulations on super-lattices are applied to study the evolution of stacking faults during epitaxial growths. We show that, in the case of misoriented close packed substrates, these defects can either extend throughout the entire epilayer (i.e. extended from the substrate up to the surface) or close in dislocation loops, in dependence of the deposition conditions. We explain this behavior in terms of a surface kinetic competition between these defects and the surrounding crystal: if the local growth rate of the defect is larger compared with that of the perfect crystal the defect will expands, otherwise it will closes. This mechanisms allows to explain several experimental results on homo and hetero epitaxies.

Journal of Crystal Growth, 2008

A novel Monte Carlo kinetic model has been developed and implemented to predict growth rate regim... more A novel Monte Carlo kinetic model has been developed and implemented to predict growth rate regimes and defect formation for the homoepitaxial CVD growth of various SiC polytypes over different substrates. The model is an advancement with respect to standard Monte Carlo algorithms, allowing to simulate both epitaxial and defective structures. The model shows two different defects formation mechanisms depending on the off-angle cut of the initial substrate and on the growth rate. The 2D island nucleation represents the limiting process for large terraces, i.e. small off-angle cuts (4 degrees and below) and low deposition rates ($12 mm=h and below). Instead, for high deposition rates ($100 mm=h typical of the SiHCl 3 -based processes) the roughness of the step becomes of the order of the terrace width, so that local step bunching occurs, hindering the standard step-flow kinetic. This enhances the creation of local defects, being, these defects, associated essentially to vacancies. The simulations also indicated that the surface morphology after the growth process is the signature of the different growth regimes. A comparison between simulation results and experimental analysis of the surface structure by means of atomic force microscopy has been performed. r

Journal of Computational Physics, 2007

A modified Kinetic Lattice Monte Carlo model has been developed to predict growth rate regimes an... more A modified Kinetic Lattice Monte Carlo model has been developed to predict growth rate regimes and defect formation in the case of the homo-epitaxial growth of close packed crystalline structures. The model is an improvement over standard Monte Carlo algorithms, which usually retain fixed atom positions and bond partners indicative of perfect crystal lattices. Indeed, we extend the concepts of Monte Carlo growth simulations on super-lattices containing additional sites (defect sites) with respect to those of the reference material. This extension implies a reconsideration of the energetic mapping, which is extensively presented, and allows to describe a complex phenomenology that is out of accessibility of standard stochastic approaches. Results obtained using the Kawasaki and the Bond-Counting rules for the transition probability of the Monte Carlo event are discussed in details. These results demonstrate how the defect types (local or extended), the formation mechanisms and the defect generation regimes can be characterized using our approach.

Electrochemical and Solid-State Letters, 2011

We present a characterization technique to assess the quality of 4H-SiC CVD growth process based ... more We present a characterization technique to assess the quality of 4H-SiC CVD growth process based on optical methods. The setup allows characterizing the epilayer and the substrate at the same time, leading to a self-consistent determination of the epitaxial layer quality with respect to the substrate. By using high power density UV optical pumping to stress 4H-SiC epitaxial layers, we are able to check the generation and evolution of Single Shockley faults on large areas, without fabricating bipolar junctions. This characterization technique is a fast and non-destructive method to compare the quality of different 4H-SiC CVD growth process.

Electrochemical and Solid-State Letters, 2011

Heteroepitaxial cubic silicon carbide (3C-SiC) is an extremely promising material for micro-and n... more Heteroepitaxial cubic silicon carbide (3C-SiC) is an extremely promising material for micro-and nano-electromechanical systems due to its large Young's modulus. Unfortunately, the heteroepitaxy of 3C-SiC on Si substrate is affected by the high mismatch in the lattice parameters and the thermal expansion coefficients between the two dissimilar materials that generate a high number of defects in the material. In this work, through the measurement of natural resonant frequencies and Raman shift analysis, a strong relationship between the mechanical proprieties of the material (Young's modulus) and the film crystal quality (defect density) was observed.

Materials Science Forum, 2009

The choice of off-axis (111) Si substrates is poorly reported in literature despite of the abilit... more The choice of off-axis (111) Si substrates is poorly reported in literature despite of the ability of such an oriented Si substrate in the reduction of stacking faults generation and propagation. The introduction of off-axis surface would be relevant for the suppression of incoherent boundaries. We grew 3C-SiC films on (111) Si substrates with a miscut angle from 3° to 6° along <110> and <11 2 >. The film quality was proved to be high by X-Ray diffraction (XRD) characterization. Transmission electron microscopy was performed to give an evaluation of the stacking fault density while pole figures were conducted to detect microtwins. Good quality single crystal 3C-SiC films were finally grown on 6 inch off-axis (111)Si substrate. The generated stress on both 2 and 6 inch 3C-SiC wafers has been analyzed and discussed.

Materials Science Forum, 2009

We discuss the possible source of surface instabilities (with specific reference to the step bunc... more We discuss the possible source of surface instabilities (with specific reference to the step bunching phenomena) during the growth of cubic and hexagonal Silicon Carbide polytypes. For this analysis we use: results from superlattice Kinetic Monte Carlo simulations, atomic force microscope surface analysis and literature data. We show that only hexagonal polytypes with misorientation cut toward the <11-20> direction suffer "intrinsically" the step bunching phenomena (i.e. it is present, independently on the growth conditions) whereas cubic polytypes and hexagonal ones with misorientation cut toward the <10-10> direction do not.

A novel Monte Carlo kinetic model has been developed and implemented to predict growth rate regim... more A novel Monte Carlo kinetic model has been developed and implemented to predict growth rate regimes and defect formation for the homo-epitaxial growth of various SiC polytypes on different substrates. Using this model we have studied the generation of both point like and extended defects in terms of the growth rate and off-cut angle, finding qualitative agreement with both electrical and optical characterization and analytical results.

Silicon Carbide and Related Materials 2009, Pts 1 and 2, 2010

In this article, using Kinetic Monte simulations on super-lattices, we study the evolution of ext... more In this article, using Kinetic Monte simulations on super-lattices, we study the evolution of extended defects during epitaxial growth. Specifically we show that, in the case of misoriented, close-packed substrates, a single-layer stacking fault can either extend throughout the entire epilayer (i.e. extended from the substrate up to the surface) or close in a dislocation loop depending on the deposition conditions and the crystallographic structure of the exposed surface containing the defect. We explain this behaviour in terms of a surface kinetic competition between the defect and the surrounding, perfect crystal: if the growth rate of the defect is higher compared to the growth rate of the surrounding crystal the defect will expand, otherwise it will close. This physical mechanism allows us to explain several experimental results of homo-and heteroepitaxy.

Silicon Carbide and Related Materials 2009, Pts 1 and 2, 2010

The fabrication of SiC MEMS-based sensors requires new processes able to realize microstructures ... more The fabrication of SiC MEMS-based sensors requires new processes able to realize microstructures on either bulk material or on the SiC surface. The hetero-epitaxial growth of 3C-SiC on silicon substrates allows one to overcome the traditional limitations of SiC microfabrication. In this work a comparison between single crystal and poly crystal 3C-SiC micromachined structures will be presented. The free-standing structures realized (cantilevers and membrane) are also a suitable method for residual field stress investigation in 3C-SiC films. Measurement of the Raman shift indicates that the mono and poly-crystal 3C-SiC structures release the stress in different ways. Finite element analysis was performed to determine the stress field inside the films and provided a good fit to the experimental data. A comprehensive experimental and theoretical study of 3C-SiC MEMS structures has been performed and is presented.

Materials Science Forum - MATER SCI FORUM, 2010

Growth of 3C-SiC films on an off-axis (111) Si substrate, with a miscut of 4° towards the <110> d... more Growth of 3C-SiC films on an off-axis (111) Si substrate, with a miscut of 4° towards the <110> direction, is here reported. An extensive material characterization has been conducted by means of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and Raman spectroscopy, indicating a very promising film quality with extremely flat surface and interface. Notwithstanding the excellent film quality, the wafer bow is still limiting its full employment in device realization.

Silicon Carbide and Related Materials 2010, 2011

Materials Science Forum, 2011

Materials Science Forum, 2012

Using several characterization techniques (µ-Raman, mechanical profilometer and microstructure de... more Using several characterization techniques (µ-Raman, mechanical profilometer and microstructure deflections) together with a recent stress model [1] we study the heteroepitaxial growth of cubic silicon carbide on silicon (100). We find that the observed inconsistency between experimental results might be the result of defects generated on the silicon substrate during the carbonization process. In such a situation wafer curvature techniques do not allow the determination of the stress field in the grown films.

Materials Science Forum, 2013

we study the surface morphology of homoepitaxially grown 4H silicon carbide in terms of growth ra... more we study the surface morphology of homoepitaxially grown 4H silicon carbide in terms of growth rate, miscut direction of the substrate and post growth argon thermal annealings. All the results indicate that the final surface morphology is the result of a competition between energetic reorganization and kinetic randomness. Because in all observed conditions energetic reorganization favors surface ondulations ("step bunching"), out-of-equilibrium conditions are one of the keys to favor the reduction of the surface roughness to values below ~0.5 nm. We theoretically support these results using kinetics superlattice Monte Carlo simulations (KslMC).

Materials Science Forum, 2012

In this article we compare the strain distribution observed in 3C-SiC/Si(100) cantilevers, using ... more In this article we compare the strain distribution observed in 3C-SiC/Si(100) cantilevers, using the shift of the transverse optical (TO) mode in micro-Raman maps, with the values predicted using a recent analytic theory [1]. By taking advantage of an under etching of the microstructures during the fabrication processes, that removes a thin layer of highly defective SiC close to the film/substrate interface near the edges of the microstructures, we show that the variation of the experimental measured strain can be ascribed to a non-linearity of the strain field along the 3C-SiC film thickness.

Materials Science Forum, 2010

Single Shockley faults have been studied in 4H-SiC epitaxial layers by using a spatial resolved m... more Single Shockley faults have been studied in 4H-SiC epitaxial layers by using a spatial resolved micro-photoluminescence technique. In particular the Effect of the UV pumping laser has been investigated. We demonstrated that high power density exposition at 325 nm affects drastically the structural properties of the epitaxial layers leading to a growth of this defect. We also demonstrated that by opportunely tuning the power density of the UV laser on the sample it is possible to analyze a wide area without producing any negative effect.

Materials Science Forum, 2014

In this paper we investigate the role of the growth rate (varied by changing the Si/H 2 ratio and... more In this paper we investigate the role of the growth rate (varied by changing the Si/H 2 ratio and using TCS to avoid Si droplet formation) on the surface roughness (R q ), 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 (D it ) at the SiO 2 /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 D it value.

Surface Science, 2010

Three dimensional kinetic Monte Carlo simulations on super-lattices are applied to study the evol... more Three dimensional kinetic Monte Carlo simulations on super-lattices are applied to study the evolution of stacking faults during epitaxial growths. We show that, in the case of misoriented close packed substrates, these defects can either extend throughout the entire epilayer (i.e. extended from the substrate up to the surface) or close in dislocation loops, in dependence of the deposition conditions. We explain this behavior in terms of a surface kinetic competition between these defects and the surrounding crystal: if the local growth rate of the defect is larger compared with that of the perfect crystal the defect will expands, otherwise it will closes. This mechanisms allows to explain several experimental results on homo and hetero epitaxies.

Journal of Crystal Growth, 2008

A novel Monte Carlo kinetic model has been developed and implemented to predict growth rate regim... more A novel Monte Carlo kinetic model has been developed and implemented to predict growth rate regimes and defect formation for the homoepitaxial CVD growth of various SiC polytypes over different substrates. The model is an advancement with respect to standard Monte Carlo algorithms, allowing to simulate both epitaxial and defective structures. The model shows two different defects formation mechanisms depending on the off-angle cut of the initial substrate and on the growth rate. The 2D island nucleation represents the limiting process for large terraces, i.e. small off-angle cuts (4 degrees and below) and low deposition rates ($12 mm=h and below). Instead, for high deposition rates ($100 mm=h typical of the SiHCl 3 -based processes) the roughness of the step becomes of the order of the terrace width, so that local step bunching occurs, hindering the standard step-flow kinetic. This enhances the creation of local defects, being, these defects, associated essentially to vacancies. The simulations also indicated that the surface morphology after the growth process is the signature of the different growth regimes. A comparison between simulation results and experimental analysis of the surface structure by means of atomic force microscopy has been performed. r

Journal of Computational Physics, 2007

A modified Kinetic Lattice Monte Carlo model has been developed to predict growth rate regimes an... more A modified Kinetic Lattice Monte Carlo model has been developed to predict growth rate regimes and defect formation in the case of the homo-epitaxial growth of close packed crystalline structures. The model is an improvement over standard Monte Carlo algorithms, which usually retain fixed atom positions and bond partners indicative of perfect crystal lattices. Indeed, we extend the concepts of Monte Carlo growth simulations on super-lattices containing additional sites (defect sites) with respect to those of the reference material. This extension implies a reconsideration of the energetic mapping, which is extensively presented, and allows to describe a complex phenomenology that is out of accessibility of standard stochastic approaches. Results obtained using the Kawasaki and the Bond-Counting rules for the transition probability of the Monte Carlo event are discussed in details. These results demonstrate how the defect types (local or extended), the formation mechanisms and the defect generation regimes can be characterized using our approach.

Electrochemical and Solid-State Letters, 2011

We present a characterization technique to assess the quality of 4H-SiC CVD growth process based ... more We present a characterization technique to assess the quality of 4H-SiC CVD growth process based on optical methods. The setup allows characterizing the epilayer and the substrate at the same time, leading to a self-consistent determination of the epitaxial layer quality with respect to the substrate. By using high power density UV optical pumping to stress 4H-SiC epitaxial layers, we are able to check the generation and evolution of Single Shockley faults on large areas, without fabricating bipolar junctions. This characterization technique is a fast and non-destructive method to compare the quality of different 4H-SiC CVD growth process.

Electrochemical and Solid-State Letters, 2011

Heteroepitaxial cubic silicon carbide (3C-SiC) is an extremely promising material for micro-and n... more Heteroepitaxial cubic silicon carbide (3C-SiC) is an extremely promising material for micro-and nano-electromechanical systems due to its large Young's modulus. Unfortunately, the heteroepitaxy of 3C-SiC on Si substrate is affected by the high mismatch in the lattice parameters and the thermal expansion coefficients between the two dissimilar materials that generate a high number of defects in the material. In this work, through the measurement of natural resonant frequencies and Raman shift analysis, a strong relationship between the mechanical proprieties of the material (Young's modulus) and the film crystal quality (defect density) was observed.