Microelectronics and Photonics by Stefano Chiussi
Applied Surface Science, 2002
Bolometers based on micromachined poly-SiGe as active elements have recently been demonstrated. T... more Bolometers based on micromachined poly-SiGe as active elements have recently been demonstrated. The advantage of using poly-SiGe relies on its low thermal conductivity, high coef®cient of temperature resistance and perfect compatibility with the IC silicon technology. In order to simplify a device integration of such elements, a combination of laser-assisted low thermal budget techniques such as laser-induced chemical vapour deposition and laser-assisted crystallisation has been proposed. The present paper shows the ®rst results obtained using this``all laser-assisted'' process for producing amorphous as well as polycrystalline SiGe alloys and the simulation of the crystallisation processes via numerical analysis for tuning the parameters of the crystallisation process. #
Applied Surface Science, 1996
An integrated laser assisted process has been applied to prepare heteroepitaxial SixGe(1-x) alloy... more An integrated laser assisted process has been applied to prepare heteroepitaxial SixGe(1-x) alloys on Si(100) using the combination of laser induced chemical vapour deposition (LCVD) and pulsed laser induced epitaxy (PLIE). Both processes have been carried out with 193 nm radiation of an ArF excimer laser leading first to high quality amorphous hydrogenated germanium (a-Ge:H) thin films by LCVD and then to unstrained epitaxial SixGe 0 -x) alloys by PLIE. The optimization for depositing homogeneous, low impurity a-Ge:H films has been followed by profilometry, Raman spectroscopy and X-ray diffraction (XRD). Subsequent melting and recrystallization by PLIE was studied by X-ray photoelectron spectroscopy (XPS) for analysing the distribution tail of the graded SixGe 0 -x) alloys and conventional XRD analysis to determine the epitaxy of the relaxed, Ge-rich, SixGe(l_x) phase. The analyses evidenced the formation of thin unstrained epitaxial SixGe(1-x) layers, which can be used as buffer layers for the growth of symmetrically strained superlattices.
Applied Surface Science, 2000
Amorphous hydrogenated silicon nitride ®lms (a-Si 1Àx N x :H) can have varied applications in opt... more Amorphous hydrogenated silicon nitride ®lms (a-Si 1Àx N x :H) can have varied applications in optoelectronics when produced as alloys with a wide range mobility gap. Employing ArF LCVD and using SiH 4 /NH 3 or Si 2 H 6 /NH 3 as the precursor gases, we have tailored the bandgap (E g ) of this material from 1.6 to 4.9 eV. It was found that Si 2 H 6 /NH 3 mixture produced highly silicon-rich alloys with compositions below the percolation threshold (x $ 0X52) of Si±Si bonds and E g between 1.6 and 2.9 eV, while SiH 4 /NH 3 , produced nitrogen-rich alloys (x $ 0X59) with E g upto 4.9 eV. This alloy can thus serve as dielectric and passivating ®lms and also as a wide bandgap semiconductor. Correlations of the gap variation with ®lm structure and composition are discussed. #
Thin Solid Films, 1998
Hydrogenated amorphous silicon nitride films produced by ArF laser-induced CVD in parallel config... more Hydrogenated amorphous silicon nitride films produced by ArF laser-induced CVD in parallel configuration using SiH rNH rAr gas 4 3 mixtures undergo post deposition chemical transformations when deposited at low temperatures. These dielectric films are found to oxidise over time on exposure to the ambient humid environment, when deposited at substrate temperatures T F 2508C. Time evolution s of these oxidation processes have been monitored through FTIR spectroscopy and ellipsometric analyses and substantiated with the deconvolution of the infrared spectra to track down intermediate oxidation species. For T F 2008C, we observe a fast oxidation process s involving gradual elimination of the Si-N, N-H and Si-H peaks and simultaneous growth of Si-O and Si-OH peaks. Above this temperature, the oxidation process has been found to slow down considerably and for T G 3008C stable films are obtained. Based on s these data, we discuss the possible film composition dependent oxidation pathway that can lead to Si-N bond rupture and creation of Si-O and Si-OH bonds. q 1998 Elsevier Science S.A.
Thin Solid Films, 2008
Rare earth oxides are emerging candidates for gate oxide films as they have high dielectric const... more Rare earth oxides are emerging candidates for gate oxide films as they have high dielectric constants as well as promising crystal and electronic structures. Lanthanum oxide is one of them but, even if many of its properties are known, no data exist in literature on its thermal conductivity. In this work, La 2 O 3 thermal diffusivity has been measured by laser flash technique in the temperature range 300 K-1600 K and, from it, its thermal conductivity has been derived. Thermal diffusivity showed a decreasing trend from 2.7 ⁎ 10 − 6 m 2 /s to 0.7 ⁎ 10 − 6 m 2 /s while thermal conductivity decreases from 6 W/m/K to 2.1 W/m/K in the studied temperature range. Results have been applied to the thermal analysis of excimer laser annealing of La 2 O 3 /Si and a-Ge/La 2 O 3 /c-Si structures.
Journal of Applied Physics, 1997
Structural properties of graded Si(1−x)Gex layers obtained on Si(100) by pulsed laser induced epi... more Structural properties of graded Si(1−x)Gex layers obtained on Si(100) by pulsed laser induced epitaxy were investigated by means of conventional powder x-ray diffraction and x-ray photoelectron spectroscopy. The Si(1−x)Gex epitaxial layers were formed by pulsed KrF-laser driven rapid melting and crystallization of thin amorphous Ge layers deposited onto the Si(100). The experimental results showed that, by increasing the number of
Applied Surface Science, 2005
The calculations of the temperature distribution induced by excimer lasers in silicon and germani... more The calculations of the temperature distribution induced by excimer lasers in silicon and germanium by using different mathematical approaches are presented. In this work, the heat conduction differential equation is solved by: (i) conventional analytical method, where the thermal parameters, i.e., thermal conductivity, specific heat and density are temperature independent; (ii) the Kirchhoff transformation method, that incorporates the dependence of the thermal conductivity with the temperature through a polynomial function; (iii) a numerical approach, by using the finite elements method (ANSYS program), which allows the incorporation of all temperature dependent parameters and the phase changes of the material using the enthalpy function.
Surface & Coatings Technology, 1996
... of MRS 284, 1993, p. 313. [6] W. Ting, J. Ahn and DL Kwong, J. Appl. Phys., 70 (1991) 3934. [... more ... of MRS 284, 1993, p. 313. [6] W. Ting, J. Ahn and DL Kwong, J. Appl. Phys., 70 (1991) 3934. [13] EG Parada, P. Gonzalez, J. Serra, B. Leon, M. Perez-Amor, [7] AB Joshi, DL Kwong and S.Lee, Appl. Phys. Lett., 60 J. Flicstein and RAB Devine, Appl. SUJ$ Sci., 86 (1995) 294. ...
Applied Surface Science, 2002
Bolometers based on micromachined poly-SiGe as active elements have recently been demonstrated. T... more Bolometers based on micromachined poly-SiGe as active elements have recently been demonstrated. The advantage of using poly-SiGe relies on its low thermal conductivity, high coef®cient of temperature resistance and perfect compatibility with the IC silicon technology. In order to simplify a device integration of such elements, a combination of laser-assisted low thermal budget techniques such as laser-induced chemical vapour deposition and laser-assisted crystallisation has been proposed. The present paper shows the ®rst results obtained using this``all laser-assisted'' process for producing amorphous as well as polycrystalline SiGe alloys and the simulation of the crystallisation processes via numerical analysis for tuning the parameters of the crystallisation process. #
Applied Surface Science, 1996
An integrated laser assisted process has been applied to prepare heteroepitaxial SixGe(1-x) alloy... more An integrated laser assisted process has been applied to prepare heteroepitaxial SixGe(1-x) alloys on Si(100) using the combination of laser induced chemical vapour deposition (LCVD) and pulsed laser induced epitaxy (PLIE). Both processes have been carried out with 193 nm radiation of an ArF excimer laser leading first to high quality amorphous hydrogenated germanium (a-Ge:H) thin films by LCVD and then to unstrained epitaxial SixGe 0 -x) alloys by PLIE. The optimization for depositing homogeneous, low impurity a-Ge:H films has been followed by profilometry, Raman spectroscopy and X-ray diffraction (XRD). Subsequent melting and recrystallization by PLIE was studied by X-ray photoelectron spectroscopy (XPS) for analysing the distribution tail of the graded SixGe 0 -x) alloys and conventional XRD analysis to determine the epitaxy of the relaxed, Ge-rich, SixGe(l_x) phase. The analyses evidenced the formation of thin unstrained epitaxial SixGe(1-x) layers, which can be used as buffer layers for the growth of symmetrically strained superlattices.
Applied Surface Science, 2000
Amorphous hydrogenated silicon nitride ®lms (a-Si 1Àx N x :H) can have varied applications in opt... more Amorphous hydrogenated silicon nitride ®lms (a-Si 1Àx N x :H) can have varied applications in optoelectronics when produced as alloys with a wide range mobility gap. Employing ArF LCVD and using SiH 4 /NH 3 or Si 2 H 6 /NH 3 as the precursor gases, we have tailored the bandgap (E g ) of this material from 1.6 to 4.9 eV. It was found that Si 2 H 6 /NH 3 mixture produced highly silicon-rich alloys with compositions below the percolation threshold (x $ 0X52) of Si±Si bonds and E g between 1.6 and 2.9 eV, while SiH 4 /NH 3 , produced nitrogen-rich alloys (x $ 0X59) with E g upto 4.9 eV. This alloy can thus serve as dielectric and passivating ®lms and also as a wide bandgap semiconductor. Correlations of the gap variation with ®lm structure and composition are discussed. #
Thin Solid Films, 1998
Hydrogenated amorphous silicon nitride films produced by ArF laser-induced CVD in parallel config... more Hydrogenated amorphous silicon nitride films produced by ArF laser-induced CVD in parallel configuration using SiH rNH rAr gas 4 3 mixtures undergo post deposition chemical transformations when deposited at low temperatures. These dielectric films are found to oxidise over time on exposure to the ambient humid environment, when deposited at substrate temperatures T F 2508C. Time evolution s of these oxidation processes have been monitored through FTIR spectroscopy and ellipsometric analyses and substantiated with the deconvolution of the infrared spectra to track down intermediate oxidation species. For T F 2008C, we observe a fast oxidation process s involving gradual elimination of the Si-N, N-H and Si-H peaks and simultaneous growth of Si-O and Si-OH peaks. Above this temperature, the oxidation process has been found to slow down considerably and for T G 3008C stable films are obtained. Based on s these data, we discuss the possible film composition dependent oxidation pathway that can lead to Si-N bond rupture and creation of Si-O and Si-OH bonds. q 1998 Elsevier Science S.A.
Thin Solid Films, 2008
Rare earth oxides are emerging candidates for gate oxide films as they have high dielectric const... more Rare earth oxides are emerging candidates for gate oxide films as they have high dielectric constants as well as promising crystal and electronic structures. Lanthanum oxide is one of them but, even if many of its properties are known, no data exist in literature on its thermal conductivity. In this work, La 2 O 3 thermal diffusivity has been measured by laser flash technique in the temperature range 300 K-1600 K and, from it, its thermal conductivity has been derived. Thermal diffusivity showed a decreasing trend from 2.7 ⁎ 10 − 6 m 2 /s to 0.7 ⁎ 10 − 6 m 2 /s while thermal conductivity decreases from 6 W/m/K to 2.1 W/m/K in the studied temperature range. Results have been applied to the thermal analysis of excimer laser annealing of La 2 O 3 /Si and a-Ge/La 2 O 3 /c-Si structures.
Journal of Applied Physics, 1997
The effects of nitrogen flow ratio, target area ratio of Cr, and substrate temperature on the str... more The effects of nitrogen flow ratio, target area ratio of Cr, and substrate temperature on the structure of DC reactive sputtered Fe-Cr-N ternary films have been studied. X-ray diffraction measurements show that Fe-Cr-N films consist of α-Fe(Cr) and γ -(Fe,Cr) 4 N x (x < 1) phases. The crystal grain of the α-Fe(Cr) phase becomes finer and a (200) texture of the γ -(Fe,Cr) 4 N x phase becomes more marked with increasing the nitrogen flow ratio. X-ray photoelectron spectra of the films show that oxidation resistance of Fe-Cr-N films is superior to that of Fe-N films, and oxides are formed only in the film surface due to contacting with the ambient atmosphere and oxygen contamination is very small in the inner parts of these films. C 1999 Kluwer Academic Publishers
Applied Surface Science, 2005
The calculations of the temperature distribution induced by excimer lasers in silicon and germani... more The calculations of the temperature distribution induced by excimer lasers in silicon and germanium by using different mathematical approaches are presented. In this work, the heat conduction differential equation is solved by: (i) conventional analytical method, where the thermal parameters, i.e., thermal conductivity, specific heat and density are temperature independent; (ii) the Kirchhoff transformation method, that incorporates the dependence of the thermal conductivity with the temperature through a polynomial function; (iii) a numerical approach, by using the finite elements method (ANSYS program), which allows the incorporation of all temperature dependent parameters and the phase changes of the material using the enthalpy function.
Surface & Coatings Technology, 1996
... of MRS 284, 1993, p. 313. [6] W. Ting, J. Ahn and DL Kwong, J. Appl. Phys., 70 (1991) 3934. [... more ... of MRS 284, 1993, p. 313. [6] W. Ting, J. Ahn and DL Kwong, J. Appl. Phys., 70 (1991) 3934. [13] EG Parada, P. Gonzalez, J. Serra, B. Leon, M. Perez-Amor, [7] AB Joshi, DL Kwong and S.Lee, Appl. Phys. Lett., 60 J. Flicstein and RAB Devine, Appl. SUJ$ Sci., 86 (1995) 294. ...
Applied Surface Science, 2002
Bolometers based on micromachined poly-SiGe as active elements have recently been demonstrated. T... more Bolometers based on micromachined poly-SiGe as active elements have recently been demonstrated. The advantage of using poly-SiGe relies on its low thermal conductivity, high coef®cient of temperature resistance and perfect compatibility with the IC silicon technology. In order to simplify a device integration of such elements, a combination of laser-assisted low thermal budget techniques such as laser-induced chemical vapour deposition and laser-assisted crystallisation has been proposed. The present paper shows the ®rst results obtained using this``all laser-assisted'' process for producing amorphous as well as polycrystalline SiGe alloys and the simulation of the crystallisation processes via numerical analysis for tuning the parameters of the crystallisation process. #
Applied Surface Science, 1996
An integrated laser assisted process has been applied to prepare heteroepitaxial SixGe(1-x) alloy... more An integrated laser assisted process has been applied to prepare heteroepitaxial SixGe(1-x) alloys on Si(100) using the combination of laser induced chemical vapour deposition (LCVD) and pulsed laser induced epitaxy (PLIE). Both processes have been carried out with 193 nm radiation of an ArF excimer laser leading first to high quality amorphous hydrogenated germanium (a-Ge:H) thin films by LCVD and then to unstrained epitaxial SixGe 0 -x) alloys by PLIE. The optimization for depositing homogeneous, low impurity a-Ge:H films has been followed by profilometry, Raman spectroscopy and X-ray diffraction (XRD). Subsequent melting and recrystallization by PLIE was studied by X-ray photoelectron spectroscopy (XPS) for analysing the distribution tail of the graded SixGe 0 -x) alloys and conventional XRD analysis to determine the epitaxy of the relaxed, Ge-rich, SixGe(l_x) phase. The analyses evidenced the formation of thin unstrained epitaxial SixGe(1-x) layers, which can be used as buffer layers for the growth of symmetrically strained superlattices.
Applied Surface Science, 2000
Amorphous hydrogenated silicon nitride ®lms (a-Si 1Àx N x :H) can have varied applications in opt... more Amorphous hydrogenated silicon nitride ®lms (a-Si 1Àx N x :H) can have varied applications in optoelectronics when produced as alloys with a wide range mobility gap. Employing ArF LCVD and using SiH 4 /NH 3 or Si 2 H 6 /NH 3 as the precursor gases, we have tailored the bandgap (E g ) of this material from 1.6 to 4.9 eV. It was found that Si 2 H 6 /NH 3 mixture produced highly silicon-rich alloys with compositions below the percolation threshold (x $ 0X52) of Si±Si bonds and E g between 1.6 and 2.9 eV, while SiH 4 /NH 3 , produced nitrogen-rich alloys (x $ 0X59) with E g upto 4.9 eV. This alloy can thus serve as dielectric and passivating ®lms and also as a wide bandgap semiconductor. Correlations of the gap variation with ®lm structure and composition are discussed. #
Thin Solid Films, 1998
Hydrogenated amorphous silicon nitride films produced by ArF laser-induced CVD in parallel config... more Hydrogenated amorphous silicon nitride films produced by ArF laser-induced CVD in parallel configuration using SiH rNH rAr gas 4 3 mixtures undergo post deposition chemical transformations when deposited at low temperatures. These dielectric films are found to oxidise over time on exposure to the ambient humid environment, when deposited at substrate temperatures T F 2508C. Time evolution s of these oxidation processes have been monitored through FTIR spectroscopy and ellipsometric analyses and substantiated with the deconvolution of the infrared spectra to track down intermediate oxidation species. For T F 2008C, we observe a fast oxidation process s involving gradual elimination of the Si-N, N-H and Si-H peaks and simultaneous growth of Si-O and Si-OH peaks. Above this temperature, the oxidation process has been found to slow down considerably and for T G 3008C stable films are obtained. Based on s these data, we discuss the possible film composition dependent oxidation pathway that can lead to Si-N bond rupture and creation of Si-O and Si-OH bonds. q 1998 Elsevier Science S.A.
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Microelectronics and Photonics by Stefano Chiussi