Precipitation of iron in multicrystalline silicon during annealing

Liu, AnYao; Macdonald, Daniel

doi:10.1063/1.4868587

Cited by 28 publications

(44 citation statements)

References 47 publications

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“…The finding that interstitial iron is gettered by SiN x films may help explain the discrepancy between the results of long, low temperature annealing experiments performed on multicrystalline silicon (mc-Si) by Krain et al, 37 Liu and Macdonald, 9 and Al-Amin and Murphy. 12 Krain et al 37 used SiN x passivation and found a systematic reduction in interstitial iron, with the activation energy being close to the diffusion activation energy of iron.…”

Section: Discussionmentioning

confidence: 66%

“…3(a)), most likely due to an insufficient degree of supersaturation of interstitial iron at 700 C and an insufficient time of 30 minutes for the nucleation and growth of iron silicide. 1,9,25 The SIMS iron profiles also show that the SiO 2 layer is unlikely to have served as a segregation gettering layer for iron, as the iron concentration in SiO 2 remains below the detection limit. This agrees with the work by Smith et al, 44 where the solubilities of iron in Si and SiO 2 were found to be similar.…”

Section: Discussionmentioning

confidence: 99%

“…[6][7][8] Similarly, in multicrystalline silicon materials for solar cells, the overall impact of iron can be alleviated by driving iron precipitation at the crystallographic defects, [9][10][11][12] although the process is much less effective than the high temperature phosphorus diffusion gettering approach.…”

Section: Introductionmentioning

confidence: 99%

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Gettering of interstitial iron in silicon by plasma-enhanced chemical vapour deposited silicon nitride films

Liu

Sun

Markevich

et al. 2016

Journal of Applied Physics

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It is known that the interstitial iron concentration in silicon is reduced after annealing silicon wafers coated with plasma-enhanced chemical vapour deposited (PECVD) silicon nitride films. The underlying mechanism for the significant iron reduction has remained unclear and is investigated in this work. Secondary ion mass spectrometry (SIMS) depth profiling of iron is performed on annealed iron-contaminated single-crystalline silicon wafers passivated with PECVD silicon nitride films. SIMS measurements reveal a high concentration of iron uniformly distributed in the annealed silicon nitride films. This accumulation of iron in the silicon nitride film matches the interstitial iron loss in the silicon bulk. This finding conclusively shows that the interstitial iron is gettered by the silicon nitride films during annealing over a wide temperature range from 250 °C to 900 °C, via a segregation gettering effect. Further experimental evidence is presented to support this finding. Deep-level transient spectroscopy analysis shows that no new electrically active defects are formed in the silicon bulk after annealing iron-containing silicon with silicon nitride films, confirming that the interstitial iron loss is not due to a change in the chemical structure of iron related defects in the silicon bulk. In addition, once the annealed silicon nitride films are removed, subsequent high temperature processes do not result in any reappearance of iron. Finally, the experimentally measured iron decay kinetics are shown to agree with a model of iron diffusion to the surface gettering sites, indicating a diffusion-limited iron gettering process for temperatures below 700 °C. The gettering process is found to become reaction-limited at higher temperatures.

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Section: Discussionmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 99%

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Gettering of interstitial iron in silicon by plasma-enhanced chemical vapour deposited silicon nitride films

Liu

Sun

Markevich

et al. 2016

Journal of Applied Physics

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“…The plot on the left shows that this occurs even far away from the grain boundaries, indicating precipitation at defects within the grains, as detailed elsewhere [24,25]. This precipitation at intra-grain defects is the most important in reducing the global dissolved Fe concentration during low temperature annealing, since the intra-grain regions account for a large majority of the wafer surface.…”

Section: Solid State Phenomena Vols 205-206mentioning

confidence: 90%

External and Internal Gettering of Interstitial Iron in Silicon for Solar Cells

Macdonald

Liu

Phang

2013

SSP

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Abstract. The removal of dissolved iron from the wafer bulk is important for the performance of ptype multicrystalline silicon solar cells. In this paper we review some recent progress in understanding both external and internal gettering of iron. Internal gettering at grain boundaries and dislocations occurs naturally during ingot cooling, and can also be driven further during cell processing, especially by moderate temperature anneals (usually below 700 °C). Internal gettering at intra-grain defects plays key a role during such precipitation annealing. External gettering to phosphorus diffused regions is crucial in reducing the dissolved iron concentration during cell processing, although its effectiveness depends strongly on the diffusion temperature and profile. Gettering of Fe by boron and aluminum diffusions is also found to be very effective under certain conditions.

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“…Extensive research has been performed into external gettering using phosphorus, boron, or aluminium to remove metallic impurities from the bulk [7][8][9]. A number of studies have also been performed into low temperature internal gettering in which metallic impurities are redistributed within the material in configurations in which they are less detrimental to average lifetime [10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%