Contactless mapping of lifetime and diffusion length scan map of minority carriers in silicon wafers

Palais, Olivier; Gervais, Jean‐Loup; Yakimov, E. B.; Martinuzzi, S.

doi:10.1051/epjap:2000128

Cited by 20 publications

(14 citation statements)

References 19 publications

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“…This study is a preliminary study for the development of a characterization bench based on the microwave phaseshift technique (mW-PS) for the determination of impurities in silicon. mW-PS [36] is a sensitive (10 9 cm À3 limit [37]), contactless technique carried out at low level of carrier injection based on the measurement of the phaseshift between the modulated light excitation signal and the intensity of the reflected microwaves.…”

Section: Discussionmentioning

confidence: 99%

Nickel and gold identification in p-type silicon through TDLS: a modeling study

Dehili

Barakel

Ottaviani

et al. 2021

Eur. Phys. J. Appl. Phys.

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In Silicon, impurities introduce recombination centers and degrade the minority carrier lifetime. It is therefore important to identify the nature of these impurities through their characteristics: the capture cross section σ and the defect level Et. For this purpose, a study of the bulk lifetime of minority carriers can be carried out. The temperature dependence of the lifetime based on the Shockley-Read-Hall (SRH) statistic and related to recombination through defects is studied. Nickel and gold in p-type Si have been selected for the SRH lifetime modeling. The objective of the analysis is to carry out a study to evaluate gold and nickel identification prior to temperature-dependent lifetime measurements using the microwave phase-shift (μW-PS) technique. The μW-PS is derived from the PCD technique and is sensitive to lower impurity concentrations. It has been shown that both gold and nickel can be unambiguously identified from the calculated TDLS curves.

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Section: Discussionmentioning

confidence: 99%

Nickel and gold identification in p-type silicon through TDLS: a modeling study

Dehili

Barakel

Ottaviani

et al. 2021

Eur. Phys. J. Appl. Phys.

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“…Lifetime is also measured by the contact less microwave phase shift (µWPS) technique [6]. These measurements could be applied to the wafers before and after any type of treatment, including dissociation of FeB and CrB pairs, by annealing at 200…”

Section: Methodsmentioning

confidence: 99%

Minority carrier bulk lifetimes through a large multicrystalline silicon ingot and related solar cell properties

Martinuzzi

Gauthier²,

Barakel

et al. 2007

Eur. Phys. J. Appl. Phys.

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Abstract. The bulk lifetime τn and diffusion length Ln of minority carriers vary through the height of a cast multicrystalline silicon (mc-Si) block. This variation is due to the segregation of metallic impurities during the directional solidification and the native impurity concentrations increase from the bottom to the top of the ingot, which is solidified last, while the ingot bottom, which is solidified first, is contaminated by the contact with the crucible floor. It is of interest to verify if a correlation exists between the bulk lifetime τ of as cut wafers and the conversion efficiency η of solar cells. In a very large ingot (>310 kg), it was found that τ0, in raw wafers, τ dif in phosphorus diffused ones and Ln in diffused wafers are smaller in the top and in the bottom of the ingot. The same evolution is observed in solar cells, however the diffusion length values L cel in the central part of the ingot are markedly higher than those found in diffused wafers, due to the in-diffusion of hydrogen from the SiN-H antireflection coating layer. The variations of η and those of τ0, along the ingot height, are well correlated, suggesting that the evaluation of τ0 can predict the properties of the devices. In addition, segregation phenomena around the grain boundaries are observed at the bottom of the ingots, due to a marked contamination by the crucible floor, and at its top where impurities are accumulated. These phenomena are linked to the long duration of the solidification process and the large amount of imperfect silicon used to cast the ingot.

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“…Glow discharge mass spectroscopy (GDMS) was used to evaluate metallic impurity atom concentrations less than 1 ppma, and interstitial gas analysis (IGA) allowed determine carbon, nitrogen and and oxygen concentrations. Three wafers were chosen in each region and were investigated as cut, after phosphorus diffusion at 850 °C for 30 min (similar to the standard diffusion process used to make solar cells) or after an intentional gettering treatment due to a long phosphorus diffusion at 900 °C for 2 h. Mean values of electron bulk lifetime (τ) were determined in as cut (τ 0 ), phosphorus diffused (τ dif ) and gettered (τ get ) wafers, by means of the quasi steady state photoconductance technique 5 at low injection level (~ 10 12 cm -3 ), and also by the contact less microwave phase shift (µWPS) technique 6 . These measurements could be applied before and after any type of treatment, including dissociation of FeB and CrB pairs, by annealing at 200°C or by strong illumination.…”

Section: Methodsmentioning

confidence: 99%

Electrical and photovoltaic properties through a large multicrystalline Si ingot

Martinuzzi¹,

Perichaud²,

Palais³

et al. 2007

SPIE Proceedings

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Large multicrystalline cast silicon ingots (>310 kg) are cost effective in the photovoltaic industry and attenuate the feedstock shortage. The bulk lifetime τ n and diffusion length L n of minority carriers vary through the height due to the segregation of metallic impurities during the directional solidification. The native impurity concentrations increase from the bottom to the top of the ingot, which is solidified last, while the ingot bottom, which is solidified first, is contaminated by the contact with the crucible. It was found that τ n and L n are the smallest in the top and in the bottom of the ingot. In solar cells, the evolution is similar, however in the central part of the ingot L n is strongly increased due to the in-diffusion of hydrogen from the SiN-H antireflection coating layer. The variations along the ingot height of the conversion efficiency η and of τ n in raw wafers are well correlated, that can predict the values of η, allowing an in-line sorting of the wafers, before solar cells are made. If τ n is smaller than 1 µs, as observed at the extremities of the ingot, η will be limited to 10% only; if τ n is higher than 2.5 µs η achieve 15 % at least. In addition, impurity segregation phenomena around grain boundaries are observed at the extremities of the ingots, linked to the long duration of the solidification process. Reducing the height of the ingots could suppress these phenomena and not much material must be discarded. Another problem can come from the use of upgraded metallurgical silicon feedstock in which the densities of boron and phosphorus are very close. Due to the difference in the segregation coefficients, ingots may be entirely or partly p or n type, suggesting that a purification step tawards the dopants is required.

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Contactless mapping of lifetime and diffusion length scan map of minority carriers in silicon wafers

Cited by 20 publications

References 19 publications

Nickel and gold identification in p-type silicon through TDLS: a modeling study

Nickel and gold identification in p-type silicon through TDLS: a modeling study

Minority carrier bulk lifetimes through a large multicrystalline silicon ingot and related solar cell properties

Electrical and photovoltaic properties through a large multicrystalline Si ingot

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