Alain Madec | Air Liquide (original) (raw)

Papers by Alain Madec

This work is a comparative study of the optical and chemical properties of Hydrogenated Silicon N... more This work is a comparative study of the optical and chemical properties of Hydrogenated Silicon Nitride films (SiNx:Hy) made with an atmospheric pressure PECVD (AP - Plasma Enhanced Chemical Vapor Deposition) process under development and an industrial Low Pressure (LP) PECVD reactor. The AP-PECVD films are deposited with a laboratory scale reactor using Ar, SiH4 and NH3 gas mixtures whereas the LP-PECVD silicon nitride is obtained in a Centrotherm reactor with NH3 and SiH4 as reactive gases. The optical parameters (refractive index and extinction coefficient) of the two silicon nitrides are compared before and after Rapid Thermal Annealing (RTA) by means of ellipsometric measurements and New Amorphous dispersion law. To compare the different chemistries of the layers, FTIR measurements are done, also before and after RTA. Si-H and N-H absorption peaks are related to the refractive index showing that the same optical properties are obtained with different chemical compositions. To finalize the comparison between LP and AP-PECVD, coatings have been processed on multicrystalline silicon solar cells.

The present work shows a detailed study on the formation and characterization of dielectric cappi... more The present work shows a detailed study on the formation and characterization of dielectric capping layers deposited by direct and remote plasma sources in the PECVD system. The capping layers were used in between the rear side passivation layer and the back side metal contact for high efficiency rear passivated p-type monocrystalline Si solar cells. Diverse conditions for deposition are presented and their influence on the solar cell performance is analyzed. Our dielectric layers on solar cell device are based on Air Liquide's precursors. Conversion efficiency above 19.4 % on monocrystalline p-type Cz-Si substrate is reached achieving 0.7% absolute gain compared to the reference (Al-BSF).

Appareil pour la mise en oeuvre d'un procede de traitement d'un substrat (3, 13) a deux f... more Appareil pour la mise en oeuvre d'un procede de traitement d'un substrat (3, 13) a deux faces par decharge a barriere dielectrique, comprenant une premiere electrode venant se placer au dessous de la face inferieure du substrat, une deuxieme electrode venant se placer au dessus de la face superieure du substrat, un moyen (6, 16) de mise en contact direct ou indirect de la premiere electrode (1, 11) avec la face inferieure du substrat (3, 13), un moyen (A/B) de maintien de la deuxieme electrode a une distance constante de la premiere electrode, et/ou a une distance constante de la face superieure du substrat,

This work is a comparative study of the optical and chemical properties of Hydrogenated Silicon N... more This work is a comparative study of the optical and chemical properties of Hydrogenated Silicon Nitride films (SiNx:Hy) made with an atmospheric pressure PECVD (AP - Plasma Enhanced Chemical Vapor Deposition) process under development and an industrial Low Pressure (LP) PECVD reactor. The AP-PECVD films are deposited with a laboratory scale reactor using Ar, SiH4 and NH3 gas mixtures whereas the LP-PECVD silicon nitride is obtained in a Centrotherm reactor with NH3 and SiH4 as reactive gases. The optical parameters (refractive index and extinction coefficient) of the two silicon nitrides are compared before and after Rapid Thermal Annealing (RTA) by means of ellipsometric measurements and New Amorphous dispersion law. To compare the different chemistries of the layers, FTIR measurements are done, also before and after RTA. Si-H and N-H absorption peaks are related to the refractive index showing that the same optical properties are obtained with different chemical compositions. To finalize the comparison between LP and AP-PECVD, coatings have been processed on multicrystalline silicon solar cells.

Apparatus for the implementation of a continuous process for treating substrates by dielectric ba... more Apparatus for the implementation of a continuous process for treating substrates by dielectric barrier discharge for the simultaneous processing of two substrates, comprising: - a first electrode, - a second electrode, at least one of the electrodes being covered a dielectric barrier, - means for feeding at least two substrates in the space between the two electrodes; - a intimately contacting means of the first electrode with one of the faces of a first substrate - an intimate contacting means of the second electrode with one side of a second substrate, - holding means of the second electrode at a constant distance from the first electrode, - a feeding means the space between the two substrates in a process gas, said first and second electrodes being connected to an electrical power source so that the discharge takes place between the electrodes, and fa CON to create a plasma in the process gas between the two substrates.

We present here the use of dimethylaluminium isopropoxide (DMAI) as the Al precursor to test the ... more We present here the use of dimethylaluminium isopropoxide (DMAI) as the Al precursor to test the significance of precursor purity on Al2O3 passivation layers. High-purity DMAI was compared with Fe-spiked batches (5 and 500 ppm). 30 nm Al2O3 was deposited onto n- and p-type crystalline silicon (c-Si) floatzone wafers using plasmaenhanced and thermal ALD at 200 °C. Effective carrier lifetimes were measured for as-deposited films, after annealing, and after high temperature annealing designed to mimic the contact "firing" process. The lifetimes afforded by Al2O3 deposited by plasma-enhanced ALD were more affected than those by thermal ALD, particularly at high Fe concentrations. Firing also affected the plasma-enhanced ALD films more compared with thermal ALD. The highest lifetimes (~1 ms) were obtained with the plasma-enhanced ALD films after annealing, whereas good lifetimes (100 μs) were afforded by the thermal ALD films already in the as-deposited state, compared with the very low lifetimes of the as-deposited plasma-enhanced ALD films. In general, n-type c-Si wafers were more sensitive to the Fe in the passivation layers than p-type. For thermal ALD, Fe-related lifetime degradation was only noticeable after firing, whereas for plasma-enhanced ALD, the degradation was observed after annealing.

The doped layers in thin film silicon and heterojunction solar cells deposited by Plasma Enhanced... more The doped layers in thin film silicon and heterojunction solar cells deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) provide a potential for device improvement. Conventionally, p-type doping is done by gases such as Diborane (B2H6), Boron Trifluoride (BF3), Boron Trichloride (BCl3) or Trimethylborane (TMB). From a practical point of view, these gases are toxic, corrosive and/or pyrophoric, and from a performance perspective, they may not provide the full range of optical and electrical properties for the doped layers. In this work, we explore the use of 1,3,5-Trimethylborazine (C3H12B3N3 , TMBz) as a doping gas for p-type layers deposited by PECVD. We examine layers of p-type hydrogenated micro-crystalline silicon (p-μc-Si:H) and p-type amorphous silicon (p-a-Si:H) using various optical and electrical characterisation techniques, as well as Secondary Ion Mass Spectroscopy (SIMS) and Fourier Transform Infrared Spectroscopy (FT-IR). Dark conductivities of the order of 10-2 S/cm were achieved at optimised deposition conditions for the p-μc-Si:H layers. With FT-IR, it was seen that under the deposition conditions of p-μc-Si:H, the ring structure of TMBz dissociates. These p-type layers were tested in single junction p-i-n devices and an initial efficiency of 4.5% was achieved with un-optimised layers.

ABSTRACT The present work shows a detailed study on the formation and characterization of dielect... more ABSTRACT The present work shows a detailed study on the formation and characterization of dielectric capping layers deposited by direct and remote plasma sources in the PECVD system. The capping layers were used in between the rear side passivation layer and the back side metal contact for high efficiency rear passivated p-type monocrystalline Si solar cells. Diverse conditions for deposition are presented and their influence on the solar cell performance is analyzed. Our dielectric layers on solar cell device are based on Air Liquide's precursors. Conversion efficiency above 19.4 % on monocrystalline p-type Cz-Si substrate is reached achieving 0.7% absolute gain compared to the reference (Al-BSF).

AIP Advances, 2016

The effect of small disilane addition on the gas phase properties of silane-hydrogen plasmas and ... more The effect of small disilane addition on the gas phase properties of silane-hydrogen plasmas and the microcrystalline silicon thin films growth is presented. The investigation was conducted in the high pressure regime and for constant power dissipation in the discharge with the support of plasma diagnostics, thin film studies and calculations of discharge microscopic parameters and gas dissociation rates. The experimental data and the calculations show a strong effect of disilane on the electrical properties of the discharge in the pressure window from 2 to 3 Torr that is followed by significant raise of the electron number density and the drop of the sheaths electric field intensity. Deposition rate measurements show an important four to six times increase even for disilane mole fractions as low as 0.3 %. The deposition rate enhancement was followed by a drop of the material crystalline volume fraction but films with crystallinity above 40 % were deposited with different combinatio...

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2016

The effect of small disilane addition to the silane/hydrogen mixture and of the total silane/hydr... more The effect of small disilane addition to the silane/hydrogen mixture and of the total silane/hydrogen flow rate on the silicon thin film growth rate and crystallinity were investigated. The study was performed by using simplified gas phase chemistry model along with plasma diagnostics such as electrical and deposition rate measurements. The results showed that even small disilane addition induces an increase in the electron density, silane electron-induced dissociation rate, and film growth rate. The increase in the total flow rate caused a linear increase in the film growth rate despite the negligible effect on the discharge microscopic parameters. Similar deposition rates and crystallinities were achieved with both disilane addition and increase in the flow rate, but the deposition efficiency was much higher in the case of disilane addition. The simplified gas phase chemistry model indicated an increase in the silyl production rate either with the disilane addition or the increase...

The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of sili... more The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of silicon thin films is investigated. Different ways of gas introduction into the plasma zone were tested including single gas entrance configuration as well as two different showerhead designs. Variation of flow and mixing conditions were critical for the effect of disilane addition on the electrical properties of the discharge and the film growth rate. Electrical measurements showed that the power density of the discharge is slightly affected by the disilane addition but affects much stronger the phase impedance leading to more resistive plasmas. The way the growth rate is influenced by the disilane addition depends on the RF electrode design and the proper choice of the process parameters.

Energy Procedia, 2015

Bifaciality offers a high potential to increase the efficiency of industrial silicon solar cells ... more Bifaciality offers a high potential to increase the efficiency of industrial silicon solar cells and their integration to sustainable building design. However, not enough work has been presented on doped dielectrics for bifacial solar cells. In this work we show a study on p-doped SiO x layers for bifacial solar cells. We use a non-conventional gas precursor, hexamethyldisiloxane (HMDSO) for the silicon-oxygen source, mixed with diborane as the p-type dopant and carbon-dioxide as the additional oxygen source. Our analysis reveals that layers deposited with HMDSO are thermally stable compared to the case when silane is used. Electrochemical capacitance voltage and secondary ion mass spectrometry measurements confirm the formation of a uniform boron doped layer inside the silicon bulk. Furthermore, we found that the depth of p + -n and p + -p junction can be controlled by the deposition parameters and the time of thermal diffusion. Chemical analysis shows that carbon is accumulated at the dielectric/wafer interface due to a barrier formation inside the carbon rich silicon. The p-SiO x layers can be applied on n-c-Si and p-c-Si base material as an emitter and back surface field respectively, demonstrating a feasible bifacial solar cell device.

Proceedings of the Water Environment Federation, 2008

ABSTRACT Low pressure membranes (LPMs) have been increasingly applied in the disinfection of wast... more ABSTRACT Low pressure membranes (LPMs) have been increasingly applied in the disinfection of wastewater effluent. The efficiency of LPM in disinfection is affected by the quality of the effluent, including ion composition and effluent organic matter (EfOM). In order to better understand the two effects, two types of commercial LPMs with similar pore size rating were challenged with MS2 bacteriophage in this study at bench and pilot scales. It was found that ion composition had different effects on the performance of LPMs with loose and tight pore structures, probably as a result of different role of electrostatic repulsions between viruses and the membranes. Meanwhile, the EfOM effect was related to the presence of a colloidal fraction larger than other dissolved organics. Detailed mechanism for the EfOM effect has not been identified.The results indicate that the performance of LPMs in wastewater disinfection may be strongly influenced by the effluent ion composition and EfOM properties and different from that determined in standard bench-scale challenge tests. This should be carefully considered in the evaluation and selection of LPMs for full-scale applications.

This work is a comparative study of the optical and chemical properties of Hydrogenated Silicon N... more This work is a comparative study of the optical and chemical properties of Hydrogenated Silicon Nitride films (SiNx:Hy) made with an atmospheric pressure PECVD (AP - Plasma Enhanced Chemical Vapor Deposition) process under development and an industrial Low Pressure (LP) PECVD reactor. The AP-PECVD films are deposited with a laboratory scale reactor using Ar, SiH4 and NH3 gas mixtures whereas the LP-PECVD silicon nitride is obtained in a Centrotherm reactor with NH3 and SiH4 as reactive gases. The optical parameters (refractive index and extinction coefficient) of the two silicon nitrides are compared before and after Rapid Thermal Annealing (RTA) by means of ellipsometric measurements and New Amorphous dispersion law. To compare the different chemistries of the layers, FTIR measurements are done, also before and after RTA. Si-H and N-H absorption peaks are related to the refractive index showing that the same optical properties are obtained with different chemical compositions. To finalize the comparison between LP and AP-PECVD, coatings have been processed on multicrystalline silicon solar cells.

The present work shows a detailed study on the formation and characterization of dielectric cappi... more The present work shows a detailed study on the formation and characterization of dielectric capping layers deposited by direct and remote plasma sources in the PECVD system. The capping layers were used in between the rear side passivation layer and the back side metal contact for high efficiency rear passivated p-type monocrystalline Si solar cells. Diverse conditions for deposition are presented and their influence on the solar cell performance is analyzed. Our dielectric layers on solar cell device are based on Air Liquide's precursors. Conversion efficiency above 19.4 % on monocrystalline p-type Cz-Si substrate is reached achieving 0.7% absolute gain compared to the reference (Al-BSF).

Appareil pour la mise en oeuvre d'un procede de traitement d'un substrat (3, 13) a deux f... more Appareil pour la mise en oeuvre d'un procede de traitement d'un substrat (3, 13) a deux faces par decharge a barriere dielectrique, comprenant une premiere electrode venant se placer au dessous de la face inferieure du substrat, une deuxieme electrode venant se placer au dessus de la face superieure du substrat, un moyen (6, 16) de mise en contact direct ou indirect de la premiere electrode (1, 11) avec la face inferieure du substrat (3, 13), un moyen (A/B) de maintien de la deuxieme electrode a une distance constante de la premiere electrode, et/ou a une distance constante de la face superieure du substrat,

This work is a comparative study of the optical and chemical properties of Hydrogenated Silicon N... more This work is a comparative study of the optical and chemical properties of Hydrogenated Silicon Nitride films (SiNx:Hy) made with an atmospheric pressure PECVD (AP - Plasma Enhanced Chemical Vapor Deposition) process under development and an industrial Low Pressure (LP) PECVD reactor. The AP-PECVD films are deposited with a laboratory scale reactor using Ar, SiH4 and NH3 gas mixtures whereas the LP-PECVD silicon nitride is obtained in a Centrotherm reactor with NH3 and SiH4 as reactive gases. The optical parameters (refractive index and extinction coefficient) of the two silicon nitrides are compared before and after Rapid Thermal Annealing (RTA) by means of ellipsometric measurements and New Amorphous dispersion law. To compare the different chemistries of the layers, FTIR measurements are done, also before and after RTA. Si-H and N-H absorption peaks are related to the refractive index showing that the same optical properties are obtained with different chemical compositions. To finalize the comparison between LP and AP-PECVD, coatings have been processed on multicrystalline silicon solar cells.

Apparatus for the implementation of a continuous process for treating substrates by dielectric ba... more Apparatus for the implementation of a continuous process for treating substrates by dielectric barrier discharge for the simultaneous processing of two substrates, comprising: - a first electrode, - a second electrode, at least one of the electrodes being covered a dielectric barrier, - means for feeding at least two substrates in the space between the two electrodes; - a intimately contacting means of the first electrode with one of the faces of a first substrate - an intimate contacting means of the second electrode with one side of a second substrate, - holding means of the second electrode at a constant distance from the first electrode, - a feeding means the space between the two substrates in a process gas, said first and second electrodes being connected to an electrical power source so that the discharge takes place between the electrodes, and fa CON to create a plasma in the process gas between the two substrates.

We present here the use of dimethylaluminium isopropoxide (DMAI) as the Al precursor to test the ... more We present here the use of dimethylaluminium isopropoxide (DMAI) as the Al precursor to test the significance of precursor purity on Al2O3 passivation layers. High-purity DMAI was compared with Fe-spiked batches (5 and 500 ppm). 30 nm Al2O3 was deposited onto n- and p-type crystalline silicon (c-Si) floatzone wafers using plasmaenhanced and thermal ALD at 200 °C. Effective carrier lifetimes were measured for as-deposited films, after annealing, and after high temperature annealing designed to mimic the contact "firing" process. The lifetimes afforded by Al2O3 deposited by plasma-enhanced ALD were more affected than those by thermal ALD, particularly at high Fe concentrations. Firing also affected the plasma-enhanced ALD films more compared with thermal ALD. The highest lifetimes (~1 ms) were obtained with the plasma-enhanced ALD films after annealing, whereas good lifetimes (100 μs) were afforded by the thermal ALD films already in the as-deposited state, compared with the very low lifetimes of the as-deposited plasma-enhanced ALD films. In general, n-type c-Si wafers were more sensitive to the Fe in the passivation layers than p-type. For thermal ALD, Fe-related lifetime degradation was only noticeable after firing, whereas for plasma-enhanced ALD, the degradation was observed after annealing.

The doped layers in thin film silicon and heterojunction solar cells deposited by Plasma Enhanced... more The doped layers in thin film silicon and heterojunction solar cells deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) provide a potential for device improvement. Conventionally, p-type doping is done by gases such as Diborane (B2H6), Boron Trifluoride (BF3), Boron Trichloride (BCl3) or Trimethylborane (TMB). From a practical point of view, these gases are toxic, corrosive and/or pyrophoric, and from a performance perspective, they may not provide the full range of optical and electrical properties for the doped layers. In this work, we explore the use of 1,3,5-Trimethylborazine (C3H12B3N3 , TMBz) as a doping gas for p-type layers deposited by PECVD. We examine layers of p-type hydrogenated micro-crystalline silicon (p-μc-Si:H) and p-type amorphous silicon (p-a-Si:H) using various optical and electrical characterisation techniques, as well as Secondary Ion Mass Spectroscopy (SIMS) and Fourier Transform Infrared Spectroscopy (FT-IR). Dark conductivities of the order of 10-2 S/cm were achieved at optimised deposition conditions for the p-μc-Si:H layers. With FT-IR, it was seen that under the deposition conditions of p-μc-Si:H, the ring structure of TMBz dissociates. These p-type layers were tested in single junction p-i-n devices and an initial efficiency of 4.5% was achieved with un-optimised layers.

ABSTRACT The present work shows a detailed study on the formation and characterization of dielect... more ABSTRACT The present work shows a detailed study on the formation and characterization of dielectric capping layers deposited by direct and remote plasma sources in the PECVD system. The capping layers were used in between the rear side passivation layer and the back side metal contact for high efficiency rear passivated p-type monocrystalline Si solar cells. Diverse conditions for deposition are presented and their influence on the solar cell performance is analyzed. Our dielectric layers on solar cell device are based on Air Liquide's precursors. Conversion efficiency above 19.4 % on monocrystalline p-type Cz-Si substrate is reached achieving 0.7% absolute gain compared to the reference (Al-BSF).

AIP Advances, 2016

The effect of small disilane addition on the gas phase properties of silane-hydrogen plasmas and ... more The effect of small disilane addition on the gas phase properties of silane-hydrogen plasmas and the microcrystalline silicon thin films growth is presented. The investigation was conducted in the high pressure regime and for constant power dissipation in the discharge with the support of plasma diagnostics, thin film studies and calculations of discharge microscopic parameters and gas dissociation rates. The experimental data and the calculations show a strong effect of disilane on the electrical properties of the discharge in the pressure window from 2 to 3 Torr that is followed by significant raise of the electron number density and the drop of the sheaths electric field intensity. Deposition rate measurements show an important four to six times increase even for disilane mole fractions as low as 0.3 %. The deposition rate enhancement was followed by a drop of the material crystalline volume fraction but films with crystallinity above 40 % were deposited with different combinatio...

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2016

The effect of small disilane addition to the silane/hydrogen mixture and of the total silane/hydr... more The effect of small disilane addition to the silane/hydrogen mixture and of the total silane/hydrogen flow rate on the silicon thin film growth rate and crystallinity were investigated. The study was performed by using simplified gas phase chemistry model along with plasma diagnostics such as electrical and deposition rate measurements. The results showed that even small disilane addition induces an increase in the electron density, silane electron-induced dissociation rate, and film growth rate. The increase in the total flow rate caused a linear increase in the film growth rate despite the negligible effect on the discharge microscopic parameters. Similar deposition rates and crystallinities were achieved with both disilane addition and increase in the flow rate, but the deposition efficiency was much higher in the case of disilane addition. The simplified gas phase chemistry model indicated an increase in the silyl production rate either with the disilane addition or the increase...

The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of sili... more The effect of very small disilane addition in silane-hydrogen mixtures on the growth rate of silicon thin films is investigated. Different ways of gas introduction into the plasma zone were tested including single gas entrance configuration as well as two different showerhead designs. Variation of flow and mixing conditions were critical for the effect of disilane addition on the electrical properties of the discharge and the film growth rate. Electrical measurements showed that the power density of the discharge is slightly affected by the disilane addition but affects much stronger the phase impedance leading to more resistive plasmas. The way the growth rate is influenced by the disilane addition depends on the RF electrode design and the proper choice of the process parameters.

Energy Procedia, 2015

Bifaciality offers a high potential to increase the efficiency of industrial silicon solar cells ... more Bifaciality offers a high potential to increase the efficiency of industrial silicon solar cells and their integration to sustainable building design. However, not enough work has been presented on doped dielectrics for bifacial solar cells. In this work we show a study on p-doped SiO x layers for bifacial solar cells. We use a non-conventional gas precursor, hexamethyldisiloxane (HMDSO) for the silicon-oxygen source, mixed with diborane as the p-type dopant and carbon-dioxide as the additional oxygen source. Our analysis reveals that layers deposited with HMDSO are thermally stable compared to the case when silane is used. Electrochemical capacitance voltage and secondary ion mass spectrometry measurements confirm the formation of a uniform boron doped layer inside the silicon bulk. Furthermore, we found that the depth of p + -n and p + -p junction can be controlled by the deposition parameters and the time of thermal diffusion. Chemical analysis shows that carbon is accumulated at the dielectric/wafer interface due to a barrier formation inside the carbon rich silicon. The p-SiO x layers can be applied on n-c-Si and p-c-Si base material as an emitter and back surface field respectively, demonstrating a feasible bifacial solar cell device.

Proceedings of the Water Environment Federation, 2008

ABSTRACT Low pressure membranes (LPMs) have been increasingly applied in the disinfection of wast... more ABSTRACT Low pressure membranes (LPMs) have been increasingly applied in the disinfection of wastewater effluent. The efficiency of LPM in disinfection is affected by the quality of the effluent, including ion composition and effluent organic matter (EfOM). In order to better understand the two effects, two types of commercial LPMs with similar pore size rating were challenged with MS2 bacteriophage in this study at bench and pilot scales. It was found that ion composition had different effects on the performance of LPMs with loose and tight pore structures, probably as a result of different role of electrostatic repulsions between viruses and the membranes. Meanwhile, the EfOM effect was related to the presence of a colloidal fraction larger than other dissolved organics. Detailed mechanism for the EfOM effect has not been identified.The results indicate that the performance of LPMs in wastewater disinfection may be strongly influenced by the effluent ion composition and EfOM properties and different from that determined in standard bench-scale challenge tests. This should be carefully considered in the evaluation and selection of LPMs for full-scale applications.