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Depletion of boron-doped surfaces protected with barrier layers during POCL3-diffusion

: Lohmüller, E.; Werner, S.; Schön, J.; Thanas, M.; Mack, S.; Wolke, W.; Wolf, A.; Clement, F.; Biro, D.

Fulltext urn:nbn:de:0011-n-2669469 (610 KByte PDF)
MD5 Fingerprint: 8e68a326e2f58f96ad3e80d62751fa28
Created on: 29.11.2013

Mine, A. ; European Commission:
28th European Photovoltaic Solar Energy Conference and Exhibition, EU PVSEC 2013. Proceedings. DVD-ROM : 30 September to 04 October 2013, Paris, France
München: WIP-Renewable Energies, 2013
ISBN: 3-936338-33-7
European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) <28, 2013, Paris>
Conference Paper, Electronic Publication
Fraunhofer ISE ()
PV Produktionstechnologie und Qualitätssicherung; Silicium-Photovoltaik; Dotierung und Diffusion; Herstellung und Analyse von hocheffizienten Solarzellen; Pilotherstellung von industrienahen Solarzellen; Barrier; Depletion; Simulation; N-Type; Solar Cell

Different diffusion barrier layers applied on the boron-doped surfaces of silicon wafers with sawdamage etched surfaces are investigated with respect to their applicability in the fabrication process of n-type silicon solar cells using sequential tube furnace diffusions with a first BBr3- and a subsequent POCl3-diffusion. The barrier layers consist of silicon oxide and/or silicon nitride deposited either by plasma-enhanced chemical vapor deposition or sputter technology. The layer itself must act as barrier against phosphorus diffusion into the silicon wafer during POCl3-diffusion. Furthermore, it has to ensure that no substantial depletion of boron occurs at the wafer surface. The boron doping surface concentrations and profile depths measured after POCl3-diffusion depend on the applied diffusion barrier. If solely silicon oxide barrier layers are used, depletion of boron at the wafer surface and deeper profiles are observed, which we attribute to oxygen diffusion through the barrier and growth of a thin thermal oxide film at the silicon. With a thin silicon nitride layer incorporated into the diffusion barrier system, no significant change in the boron doping profile is detected. Numerical simulations of the boron diffusion during the POCl3- process agree well with the measurements and support these findings.