1.
L Helmich; D C Walter; D Bredemeier; J Schmidt
In: physica status solidi (RRL) – Rapid Research Letters, Bd. 14, Nr. 12, S. 2000367, 2020.
@article{Helmich2020,
title = {Atomic-Layer-Deposited Al2O3 as Effective Barrier against the Diffusion of Hydrogen from SiNx:H Layers into Crystalline Silicon during Rapid Thermal Annealing},
author = {L Helmich and D C Walter and D Bredemeier and J Schmidt},
doi = {10.1002/pssr.202000367},
year = {2020},
date = {2020-12-01},
journal = {physica status solidi (RRL) – Rapid Research Letters},
volume = {14},
number = {12},
pages = {2000367},
abstract = {Stacks of hydrogen-lean aluminum oxide, deposited via plasma-assisted atomic-layer-deposition, and hydrogen-rich plasma-enhanced chemical vapor-deposited silicon nitride (SiNx) are applied to boron-doped float-zone silicon wafers. A rapid thermal annealing (RTA) step is performed in an infrared conveyor-belt furnace at different set-peak temperatures. The hydrogen content diffused into the crystalline silicon during the RTA step is quantified by measurements of the silicon resistivity increase due to hydrogen passivation of boron dopant atoms. These experiments indicate that there exists a temperature-dependent maximum in the introduced hydrogen content. The exact position of this maximum depends on the composition of the SiNx layer. The highest total hydrogen content, exceeding 1015 cm−3, is introduced into the silicon bulk from silicon-rich SiNx layers with a refractive index of 2.3 (at λ = 633 nm) at an RTA peak temperature of 800 °C, omitting the Al2O3 interlayer. Adding an Al2O3 interlayer with a thickness of 20 nm reduces the hydrogen content by a factor of four, demonstrating that Al2O3 acts as a highly effective hydrogen diffusion barrier. Measuring the hydrogen content in the silicon bulk as a function of Al2O3 thickness at different RTA peak temperatures provides the hydrogen diffusion length in Al2O3 as a function of measured temperature.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Stacks of hydrogen-lean aluminum oxide, deposited via plasma-assisted atomic-layer-deposition, and hydrogen-rich plasma-enhanced chemical vapor-deposited silicon nitride (SiNx) are applied to boron-doped float-zone silicon wafers. A rapid thermal annealing (RTA) step is performed in an infrared conveyor-belt furnace at different set-peak temperatures. The hydrogen content diffused into the crystalline silicon during the RTA step is quantified by measurements of the silicon resistivity increase due to hydrogen passivation of boron dopant atoms. These experiments indicate that there exists a temperature-dependent maximum in the introduced hydrogen content. The exact position of this maximum depends on the composition of the SiNx layer. The highest total hydrogen content, exceeding 1015 cm−3, is introduced into the silicon bulk from silicon-rich SiNx layers with a refractive index of 2.3 (at λ = 633 nm) at an RTA peak temperature of 800 °C, omitting the Al2O3 interlayer. Adding an Al2O3 interlayer with a thickness of 20 nm reduces the hydrogen content by a factor of four, demonstrating that Al2O3 acts as a highly effective hydrogen diffusion barrier. Measuring the hydrogen content in the silicon bulk as a function of Al2O3 thickness at different RTA peak temperatures provides the hydrogen diffusion length in Al2O3 as a function of measured temperature.
2.
D Bredemeier; D C Walter; R Heller; J Schmidt
Impact of Silicon Nitride Film Properties on Hydrogen In-Diffusion into Crystalline Silicon Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 36th European Photovoltaic Solar Energy Conference and Exhibition, S. 112-115, Marseille, France, 2019, ISBN: 3-936338-60-4.
@inproceedings{Bredemeier2019d,
title = {Impact of Silicon Nitride Film Properties on Hydrogen In-Diffusion into Crystalline Silicon},
author = {D Bredemeier and D C Walter and R Heller and J Schmidt},
editor = {WIP},
doi = {10.4229/EUPVSEC20192019-2AO.4.4},
isbn = {3-936338-60-4},
year = {2019},
date = {2019-10-23},
booktitle = {Proceedings of the 36th European Photovoltaic Solar Energy Conference and Exhibition},
pages = {112-115},
address = {Marseille, France},
abstract = {Hydrogen-rich silicon nitride films deposited on top of crystalline silicon wafers are a common source of hydrogen within solar cell production. Upon rapid thermal annealing (RTA), hydrogen bonds within the silicon nitride films dissociate and the hydrogen diffuses both into the environment as well as into the silicon bulk. Within this study, we investigate the impact of silicon nitride material properties on the amount of hydrogen introduced into the silicon bulk during RTA treatment. The measurements clearly show that the atomic density of the silicon nitride film has a pronounced impact on the hydrogen in-diffusion. Importantly, we find that the total hydrogen loss during RTA within the silicon nitride films is not correlated with the actual amount of hydrogen introduced into the silicon bulk.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Hydrogen-rich silicon nitride films deposited on top of crystalline silicon wafers are a common source of hydrogen within solar cell production. Upon rapid thermal annealing (RTA), hydrogen bonds within the silicon nitride films dissociate and the hydrogen diffuses both into the environment as well as into the silicon bulk. Within this study, we investigate the impact of silicon nitride material properties on the amount of hydrogen introduced into the silicon bulk during RTA treatment. The measurements clearly show that the atomic density of the silicon nitride film has a pronounced impact on the hydrogen in-diffusion. Importantly, we find that the total hydrogen loss during RTA within the silicon nitride films is not correlated with the actual amount of hydrogen introduced into the silicon bulk.
3.
D Bredemeier; D C Walter; J Schmidt
Impact of Silicon Nitride Film Properties on Hydrogen In-Diffusion into Crystalline Silicon Vortrag
Marseille, France, 09.09.2019, (36th European Photovoltaic Solar Energy Conference and Exhibition).
@misc{Bredemeier2019c,
title = {Impact of Silicon Nitride Film Properties on Hydrogen In-Diffusion into Crystalline Silicon},
author = {D Bredemeier and D C Walter and J Schmidt},
year = {2019},
date = {2019-09-09},
address = {Marseille, France},
abstract = {Hydrogen-rich silicon nitride films deposited on top of crystalline silicon wafers are a common source of hydrogen within solar cell production. Upon rapid thermal annealing (RTA), hydrogen bonds within the silicon nitride films dissociate and the hydrogen diffuses both into the environment as well as into the silicon bulk. Within this study, we investigate the impact of silicon nitride material properties on the amount of hydrogen introduced into the silicon bulk during RTA treatment. The measurements clearly show that the atomic density of the silicon nitride film has a pronounced impact on the hydrogen in-diffusion. Importantly, we find that the total hydrogen loss during RTA within the silicon nitride films is not correlated with the actual amount of hydrogen introduced into the silicon bulk.},
note = {36th European Photovoltaic Solar Energy Conference and Exhibition},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
Hydrogen-rich silicon nitride films deposited on top of crystalline silicon wafers are a common source of hydrogen within solar cell production. Upon rapid thermal annealing (RTA), hydrogen bonds within the silicon nitride films dissociate and the hydrogen diffuses both into the environment as well as into the silicon bulk. Within this study, we investigate the impact of silicon nitride material properties on the amount of hydrogen introduced into the silicon bulk during RTA treatment. The measurements clearly show that the atomic density of the silicon nitride film has a pronounced impact on the hydrogen in-diffusion. Importantly, we find that the total hydrogen loss during RTA within the silicon nitride films is not correlated with the actual amount of hydrogen introduced into the silicon bulk.
4.
D Bredemeier; D C Walter; J Schmidt
In: Solar RRL, Bd. 2, Nr. 1, S. 1700159, 2018, ISSN: 2367-198X.
@article{Bredemeier2018,
title = {Possible Candidates for Impurities in mc-Si Wafers Responsible for Light-Induced Lifetime Degradation and Regeneration},
author = {D Bredemeier and D C Walter and J Schmidt},
doi = {10.1002/solr.201700159},
issn = {2367-198X},
year = {2018},
date = {2018-01-01},
journal = {Solar RRL},
volume = {2},
number = {1},
pages = {1700159},
abstract = {We examine the light‐induced carrier lifetime degradation and regeneration at elevated temperature in multicrystalline silicon (mc‐Si) wafers of different thicknesses. The experimental results show that the thinner the wafer the less pronounced the degradation is and the faster the regeneration takes place. We interpret this result in the framework of a recently proposed defect model, where the lifetime regeneration is attributed to the diffusion of the recombination‐active impurity to the wafer surfaces, where it is permanently trapped. Modeling the measured thickness‐dependent lifetime evolutions enables us to determine the diffusion coefficient of the impurity to be in the range (5 ± 2) × 10−11 cm2 s−1 at a temperature of 75 °C. Comparing the diffusion coefficient extracted from our measurements with data published in the literature allows us to exclude most impurities. Despite the large uncertainties in the diffusion coefficient data reported in the literature, reasonable agreement is only obtained for nickel, cobalt, and hydrogen. One important practical implication of our study is that mc‐Si wafers thinner than 120 μm do not suffer from pronounced light‐induced lifetime degradation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We examine the light‐induced carrier lifetime degradation and regeneration at elevated temperature in multicrystalline silicon (mc‐Si) wafers of different thicknesses. The experimental results show that the thinner the wafer the less pronounced the degradation is and the faster the regeneration takes place. We interpret this result in the framework of a recently proposed defect model, where the lifetime regeneration is attributed to the diffusion of the recombination‐active impurity to the wafer surfaces, where it is permanently trapped. Modeling the measured thickness‐dependent lifetime evolutions enables us to determine the diffusion coefficient of the impurity to be in the range (5 ± 2) × 10−11 cm2 s−1 at a temperature of 75 °C. Comparing the diffusion coefficient extracted from our measurements with data published in the literature allows us to exclude most impurities. Despite the large uncertainties in the diffusion coefficient data reported in the literature, reasonable agreement is only obtained for nickel, cobalt, and hydrogen. One important practical implication of our study is that mc‐Si wafers thinner than 120 μm do not suffer from pronounced light‐induced lifetime degradation.
5.
J Krügener; Y Larionova; B Wolpensinger; D Tetzlaff; S Reiter; M Turcu; R Peibst; J -D Kähler; T Wietler
Dopant diffusion from p+-poly-Si into c-Si during thermal annealing Proceedings Article
In: IEEE, (Hrsg.): 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC), S. 2451-2454, Portland, OR, USA, 2016, ISBN: 978-1-5090-2725-5.
@inproceedings{Krügener2016bc,
title = {Dopant diffusion from p+-poly-Si into c-Si during thermal annealing},
author = {J Krügener and Y Larionova and B Wolpensinger and D Tetzlaff and S Reiter and M Turcu and R Peibst and J -D Kähler and T Wietler},
editor = {IEEE},
doi = {10.1109/PVSC.2016.7750083},
isbn = {978-1-5090-2725-5},
year = {2016},
date = {2016-06-01},
booktitle = {2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC)},
journal = {Proceedings of the 43rd IEEE Photovoltaic Specialists Conference},
pages = {2451-2454},
address = {Portland, OR, USA},
abstract = {Passivating junctions, like hole-collecting p-polycrystalline silicon/SiOx/crystalline silicon junctions, need a thermal activation to activate their excellent passivation and contact properties. Here, the diffusion of boron from the highly doped poly-Si layer into the Si is often considered to compromise the passivation quality. In contrast we show that at least a slight diffusion of boron into the crystalline silicon is present for optimized annealing conditions. We achieve low emitter saturation current densities of 11 fA/cm2 for in situ p+ doped polysilicon deposited by low pressure chemical vapor deposition. Furthermore, we show that the polysilicon layer and the in-diffused region within the substrate are electrically connected.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Passivating junctions, like hole-collecting p-polycrystalline silicon/SiOx/crystalline silicon junctions, need a thermal activation to activate their excellent passivation and contact properties. Here, the diffusion of boron from the highly doped poly-Si layer into the Si is often considered to compromise the passivation quality. In contrast we show that at least a slight diffusion of boron into the crystalline silicon is present for optimized annealing conditions. We achieve low emitter saturation current densities of 11 fA/cm2 for in situ p+ doped polysilicon deposited by low pressure chemical vapor deposition. Furthermore, we show that the polysilicon layer and the in-diffused region within the substrate are electrically connected.
6.
H Wagner; A Dastgheib-Shirazi; B Min; A E Morishige; M Steyer; G Hahn; C Cañizo; T Buonassisi; P P Altermatt
In: Journal of Applied Physics, Bd. 119, S. 185704, 2016.
@article{Wagner2016,
title = {Optimizing phosphorus diffusion for photovoltaic applications: Peak doping, inactive phosphorus, gettering, and contact formation},
author = {H Wagner and A Dastgheib-Shirazi and B Min and A E Morishige and M Steyer and G Hahn and C Cañizo and T Buonassisi and P P Altermatt},
doi = {10.1063/1.4949326},
year = {2016},
date = {2016-05-01},
journal = {Journal of Applied Physics},
volume = {119},
pages = {185704},
abstract = {The phosphosilicate glass (PSG), fabricated by tube furnace diffusion using a POCl3 source, is widely used as a dopant source in the manufacturing of crystalline silicon solar cells. Although it has been a widely addressed research topic for a long time, there is still lack of a comprehensive understanding of aspects such as the growth, the chemical composition, possible phosphorus depletion, the resulting in-diffused phosphorus profiles, the gettering behavior in silicon, and finally the metal-contact formation. This paper addresses these different aspects simultaneously to further optimize process conditions for photovoltaic applications. To do so, a wide range of experimental data is used and combined with device and process simulations, leading to a more comprehensive interpretation. The results show that slight changes in the PSG process conditions can produce high-quality emitters. It is predicted that PSG processes at 860 °C for 60 min in combination with an etch-back and laser doping from PSG layer results in high-quality emitters with a peak dopant density Npeak = 8.0 × 10^18 cm−3 and a junction depth dj = 0.4 μm, resulting in a sheet resistivity ρsh = 380 Ω/sq and a saturation current-density J0 below 10 fA/cm2. With these properties, the POCl3 process can compete with ion implantation or doped oxide approaches.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The phosphosilicate glass (PSG), fabricated by tube furnace diffusion using a POCl3 source, is widely used as a dopant source in the manufacturing of crystalline silicon solar cells. Although it has been a widely addressed research topic for a long time, there is still lack of a comprehensive understanding of aspects such as the growth, the chemical composition, possible phosphorus depletion, the resulting in-diffused phosphorus profiles, the gettering behavior in silicon, and finally the metal-contact formation. This paper addresses these different aspects simultaneously to further optimize process conditions for photovoltaic applications. To do so, a wide range of experimental data is used and combined with device and process simulations, leading to a more comprehensive interpretation. The results show that slight changes in the PSG process conditions can produce high-quality emitters. It is predicted that PSG processes at 860 °C for 60 min in combination with an etch-back and laser doping from PSG layer results in high-quality emitters with a peak dopant density Npeak = 8.0 × 10^18 cm−3 and a junction depth dj = 0.4 μm, resulting in a sheet resistivity ρsh = 380 Ω/sq and a saturation current-density J0 below 10 fA/cm2. With these properties, the POCl3 process can compete with ion implantation or doped oxide approaches.
7.
N Wehmeier; B Lim; A Nowack; J Schmidt; T Dullweber; R Brendel
21.0%-efficient co-diffused screen-printed n-type silicon solar cell with rear-side boron emitter Artikel
In: physica status solidi (RRL) – Rapid Research Letters, Bd. 10, Nr. 2, S. 148-152, 2016.
@article{Wehmeier2016d,
title = {21.0%-efficient co-diffused screen-printed n-type silicon solar cell with rear-side boron emitter},
author = {N Wehmeier and B Lim and A Nowack and J Schmidt and T Dullweber and R Brendel},
doi = {10.1002/pssr.201510393},
year = {2016},
date = {2016-02-01},
journal = {physica status solidi (RRL) – Rapid Research Letters},
volume = {10},
number = {2},
pages = {148-152},
abstract = {Plasma enhanced chemical vapor deposition (PECVD) is applied to deposit boron silicate glasses (BSG) acting as boron diffusion source during the fabrication of n‐type silicon solar cells. We characterize the resulting boron‐diffused emitter after boron drive‐in from PECVD BSG by measuring the sheet resistances Rsheet,B and saturation current densities J0,B. For process optimization, we vary the PECVD deposition parameters such as the gas flows of the precursor gases silane and diborane and the PECVD BSG layer thickness. We find an optimum gas flow ratio of SiH4/B2H6= 8% and layer thickness of 40 nm. After boron drive in from these PECVD BSG diffusion sources, a low J0,B values of 21 fA/cm2 is reached for Rsheet},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Plasma enhanced chemical vapor deposition (PECVD) is applied to deposit boron silicate glasses (BSG) acting as boron diffusion source during the fabrication of n‐type silicon solar cells. We characterize the resulting boron‐diffused emitter after boron drive‐in from PECVD BSG by measuring the sheet resistances Rsheet,B and saturation current densities J0,B. For process optimization, we vary the PECVD deposition parameters such as the gas flows of the precursor gases silane and diborane and the PECVD BSG layer thickness. We find an optimum gas flow ratio of SiH4/B2H6= 8% and layer thickness of 40 nm. After boron drive in from these PECVD BSG diffusion sources, a low J0,B values of 21 fA/cm2 is reached for Rsheet
8.
A Dastgheib-Shirazi; M Steyer; G Micard; H Wagner; P P Altermatt; G Hahn
In: Energy Procedia, Bd. 38, S. 254-262, 2013, ISSN: 1876-6102, (Proceedings of the 3rd International Conference on Crystalline Silicon Photovoltaics (SiliconPV 2013)).
@article{DASTGHEIBSHIRAZI2013254,
title = {Relationships between Diffusion Parameters and Phosphorus Precipitation during the POCl3 Diffusion Process},
author = {A Dastgheib-Shirazi and M Steyer and G Micard and H Wagner and P P Altermatt and G Hahn},
doi = {10.1016/j.egypro.2013.07.275},
issn = {1876-6102},
year = {2013},
date = {2013-09-05},
journal = {Energy Procedia},
volume = {38},
pages = {254-262},
note = {Proceedings of the 3rd International Conference on Crystalline Silicon Photovoltaics (SiliconPV 2013)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
9.
N Wehmeier; G Schraps; H Wagner; B Lim; N -P Harder; P P Altermatt
Boron-doped PECVD silicon oxides as diffusion sources for simplified high-efficiency solar cell fabrication Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 28th European Photovoltaic Solar Energy Conference, S. 1980-1984, Paris, France, 2013, ISBN: 3-936338-33-7.
@inproceedings{Wehmeier2013,
title = {Boron-doped PECVD silicon oxides as diffusion sources for simplified high-efficiency solar cell fabrication},
author = {N Wehmeier and G Schraps and H Wagner and B Lim and N -P Harder and P P Altermatt},
editor = {WIP},
doi = {10.4229/28thEUPVSEC2013-2DV.3.52},
isbn = {3-936338-33-7},
year = {2013},
date = {2013-09-01},
booktitle = {Proceedings of the 28th European Photovoltaic Solar Energy Conference},
journal = {Proceedings of the 28th European Photovoltaic Solar Energy Conference},
pages = {1980-1984},
address = {Paris, France},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
10.
J Müller; K Bothe; S Herlufsen; H Hannebauer; R Ferre; R Brendel
In: Solar Energy Materials and Solar Cells, Bd. 106, S. 76-79, 2012, (SiliconPV).
@article{Müller2012d,
title = {Reverse saturation current density imaging of highly doped regions in silicon: A photoluminescence approach},
author = {J Müller and K Bothe and S Herlufsen and H Hannebauer and R Ferre and R Brendel},
doi = {10.1016/j.solmat.2012.05.026},
year = {2012},
date = {2012-11-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {106},
pages = {76-79},
note = {SiliconPV},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
11.
M Kessler; T Ohrdes; P P Altermatt; R Brendel
In: Journal of Applied Physics, Bd. 111, Nr. 5, S. 054508, 2012.
@article{Kessler2012,
title = {The effect of sample edge recombination on the averaged injection-dependent carrier lifetime in silicon},
author = {M Kessler and T Ohrdes and P P Altermatt and R Brendel},
doi = {10.1063/1.3691230},
year = {2012},
date = {2012-03-01},
journal = {Journal of Applied Physics},
volume = {111},
number = {5},
pages = {054508},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
12.
C Ulzhöfer; P P Altermatt; N -P Harder; R Brendel
In: Journal of Applied Physics, Bd. 107, Nr. 10, S. 104509, 2010.
@article{Ulzhöfer2010,
title = {Loss analysis of emitter-wrap-through silicon solar cells by means of experiment and three-dimensional device modeling},
author = {C Ulzhöfer and P P Altermatt and N -P Harder and R Brendel},
doi = {10.1063/1.3373612},
year = {2010},
date = {2010-05-01},
journal = {Journal of Applied Physics},
volume = {107},
number = {10},
pages = {104509},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
13.
J Schmidt; N Thiemann; R Bock; R Brendel
Recombination lifetimes in highly aluminum-doped silicon Artikel
In: Journal of Applied Physics, Bd. 106, Nr. 9, S. 093707, 2009.
@article{Schmidt2009b,
title = {Recombination lifetimes in highly aluminum-doped silicon},
author = {J Schmidt and N Thiemann and R Bock and R Brendel},
doi = {10.1063/1.3253742},
year = {2009},
date = {2009-11-01},
journal = {Journal of Applied Physics},
volume = {106},
number = {9},
pages = {093707},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
14.
W Stockum; I Köhler; O Doll; M James; E Plummer; L Nanson; M Prütz; S Wyczanowski; M Jahn; V Mertens; N -P Harder
Direct Inkjet Printing of SiO2 Diffusion Barrier for the Formation of Local Boron Back Surface Fields Proceedings Article
In: WIP, (Hrsg.): 24th European Photovoltaic Solar Energy Conference, S. 1723-1726, Hamburg, Germany, 2009, ISBN: 3-936338-25-6.
@inproceedings{Stockum2009,
title = {Direct Inkjet Printing of SiO2 Diffusion Barrier for the Formation of Local Boron Back Surface Fields},
author = {W Stockum and I Köhler and O Doll and M James and E Plummer and L Nanson and M Prütz and S Wyczanowski and M Jahn and V Mertens and N -P Harder},
editor = {WIP},
doi = {10.4229/24thEUPVSEC2009-2CV.5.4},
isbn = {3-936338-25-6},
year = {2009},
date = {2009-09-01},
booktitle = {24th European Photovoltaic Solar Energy Conference},
pages = {1723-1726},
address = {Hamburg, Germany},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
15.
D Hinken; K Bothe; K Ramspeck; S Herlufsen; R Brendel
Determination of the effective diffusion length of silicon solar cells from photoluminescence Artikel
In: Journal of Applied Physics, Bd. 105, Nr. 10, S. 104516, 2009.
@article{Hinken2009b,
title = {Determination of the effective diffusion length of silicon solar cells from photoluminescence},
author = {D Hinken and K Bothe and K Ramspeck and S Herlufsen and R Brendel},
doi = {10.1063/1.3130408},
year = {2009},
date = {2009-05-01},
journal = {Journal of Applied Physics},
volume = {105},
number = {10},
pages = {104516},
keywords = {},
pubstate = {published},
tppubtype = {article}
}