Extended high temperature Al gettering for improvement and homogenization of minority carrier diffusion lengths in multicrystalline Si

Joshi, Subhash M.; Gösele, U.; Tan, T. Y.

doi:10.1016/s0927-0248(01)00029-0

Cited by 23 publications

(13 citation statements)

References 23 publications

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“…Therefore, diffusion is most rapid in wet oxidation. Thermally grown SiO 2 layer is usually amorphous in nature and has a density of $2.2 gm/cm 3 . The oxidation occurs throughout the porous silicon volume and this in term corresponds to the growth of several nanometers of regular silicon dioxide.…”

Section: Resultsmentioning

confidence: 99%

“…The presence of defects and impurities in the mc-Si substrate leads to the formation of energy levels in the forbidden zone, which essentially have some influence on the electrical (including the recombination) parameters of the material. This in turn results in a reduced minority carrier diffusion length (L n ) in the bulk region of the substrates [1][2][3]. Therefore, the processing step like gettering is the most suitable, which either removes or blocks the impurities and defects away from the device-active regions that have to be incorporated in the device-processing step to improve the electronic quality of the mc-Si substrate [4,5].…”

Section: Introductionmentioning

confidence: 99%

“…The extrinsic gettering (EG) mechanisms such as phosphorous diffusion gettering (PDG) [7], aluminum alloy gettering (AAG) [4,7] or a combination of phosphorous and aluminum gettering have shown beneficial effects to improve or restore the bulk quality of silicon substrate [7][8][9]. Due to the slow dissolution of precipitate in the dislocation regions, these regions cannot be improved by the conventional PDG or AAG process step [3,8,9].…”

Section: Introductionmentioning

confidence: 99%

“…The porous silicon has a hydrogen-rich surface, which makes the possibility of a bulk passivation effect during the hightemperature oxidation step and may also help to suppress the electrically active defects in the bulk region of the mc-Si substrate [18,19]. The grain boundary and dislocation passivation by Al indiffusion or indiffusion of atomic hydrogen generated at the Al-Si may also contribute to enhance SR in the longer wavelength range and hence to an apparent improvement of the minority carrier diffusion length in the porous silicon/aluminum co-gettered samples [3,8,18,20].…”

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Porous silicon and aluminum co-gettering experiment in p-type multicrystalline silicon substrate

Vinod

2007

Science and Technology of Advanced Materials

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The lifetimes of non-equilibrium minority carriers, which bound with the diffusion length, are considered as two important parameters of the low-quality multicrystalline silicon (mc-Si) substrate. Its value defines the quality of the initial substrate. It is also subjected to change as a result of many high-temperature operations during the device fabrication. Therefore, it is necessary to incorporate certain processing steps that either improve or preserve the electronic quality of the mc-Si substrate. In this study, a novel porous silicon and aluminum co-gettering experiment has been applied as a beneficial approach to improve the electronic quality of the low-resistivity mc-Si substrates. Porous silicon layers were prepared by anodization of the n + silicon region by a simple electrochemical etching process using an aqueous HF-based electrolyte, which leads to the creation of porous silicon microcavities. Besides making porous silicon and aluminum co-gettered samples, both phosphorous and aluminum alloy-gettered samples and reference samples were made. The gettering-induced lifetime enhancement in the test samples was monitored by measuring the lifetime/diffusion length of the test samples using two independent methods such as photoconductivity decay (PCD) measurement and the photocurrent generation method (PCM), respectively. The result in both the measurements has shown a reasonably good agreement with each other. Therefore, it is inferred that the applied co-gettering experiment has a synergetic effect to improve the lifetime of the mc-Si substrate. r

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Porous silicon and aluminum co-gettering experiment in p-type multicrystalline silicon substrate

Vinod

2007

Science and Technology of Advanced Materials

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“…We have previously identified the involved physical processes and accordingly modeled the gettering of metals, 1,[3][4][5][6] including metal dissolution from the precipitates, diffusion of metal atoms to and their stabilization at the gettering sites, and the effect of the precipitate volume misfit with the Si matrix on the gettering effectiveness. In the present problem of optical-processing gettering of Fe and FeSi 2 as the gettered metal and precipitates, we assume that the misfit due to precipitate dissolution is accommodated primarily by the point defect vacancies (V).…”

Section: Introductionmentioning

confidence: 99%

Precipitate Dissolution and Gettering under Vacancy Injection in Silicon: Final Subcontract Report, 21 March 2006 - 15 January 2008

Tan¹,

Li²

2008

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Using a deposited Al layer, optical processing at a temperature below the Si-Al eutectic temperature of T eu =577 o C for a few minutes and followed by T>T eu for a few more minutes are able to getter metallic precipitates out of multicrystalline Si. To accomplish the same, a few tens of hrs is needed when using thermal annealing at 700 o C. Possible mechanisms involved in opticalprocessing gettering are proposed. These mechanisms include vacancy injection, radiationenhanced solubility, and radiation-enhanced diffusion of vacancies and metal impurity atoms. Using FeSi 2 as a model case for which the Si lattice expands concomitantly with the dissolution of the precipitates, physical modeling and numerical simulations are carried out to uncover and test the conditions for the mechanisms to be effective. The mechanisms are found to be effective provided that the injected Si vacancies due to alloy formation are nearly all retained inside and evenly distributed throughout the Si bulk at the lower temperature, and that the Fe atom migration energy barrier is reduced by ~0.15 eV by radiation at the higher temperature. On the other hand, for the gettering of a precipitate species for which the Si lattice will shrink concomitantly with the dissolution of the precipitates, the vacancy-injection mechanism will not only be ineffective but should also have a detrimental effect.

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Ceccaroli¹,

Pizzini

2012

Advanced Silicon Materials for Photovoltaic Applications

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Extended high temperature Al gettering for improvement and homogenization of minority carrier diffusion lengths in multicrystalline Si

Cited by 23 publications

References 23 publications

Porous silicon and aluminum co-gettering experiment in p-type multicrystalline silicon substrate

Porous silicon and aluminum co-gettering experiment in p-type multicrystalline silicon substrate

Precipitate Dissolution and Gettering under Vacancy Injection in Silicon: Final Subcontract Report, 21 March 2006 - 15 January 2008

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