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Proceedings Paper

SLiM-cut thin silicon wafering with enhanced crack and stress control
Author(s): Jan Vaes; Alex Masolin; Amaia Pesquera; Frédéric Dross
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Paper Abstract

The 'Stress induced LIft-off Method' (SLiM-Cut) is a kerf-free method for thin silicon fabrication, being developed at imec for photovoltaic applications [1]. This method makes particularly efficient use of bulk material, thus cutting down the Si cost. SLIM-Cut uses a metallic layer on top of thick silicon substrate. The bonding is achieved at high temperature. Quenching the assembly down to room temperature builds up stress inside the material. The system relaxes by propagating a crack parallel to the metal-silicon interface. The propagation of this crack over the entire surface allows the formation of a silicon foil. The choice of the stress inducing layer is of the utmost importance: (1) the interfacial strength has to be high enough for the crack to grow in the Si lattice, (2) the metal migration has to be limited in order not to compromise the PV conversion efficiency, and (3) the deposition method of the stressing layer should be compatible with PV cell processing. The focus is laid on the two main compromises of the technology today: the precise control of the stress applied to the substrate, and the metal-Si interface. Regarding the control of the stress applied, we have intentionally initiated the crack. Better control of the crack propagation was demonstrated. Tuning of the temperature becomes therefore possible and lift-off was achieved for temperature processing as low as 700°C. Although all crystal orientations (including <100>) have been successfully lifted-off, the choice of the crystal orientation influences strongly the final result. Regarding the metal-Si interface, a detail elemental study has enabled us to identify the composition of the interface layers responsible for good adhesion to the Si. This investigation is also the first step to the engineering of specific paste and cleaning solutions.

Paper Details

Date Published: 24 August 2010
PDF: 11 pages
Proc. SPIE 7772, Next Generation (Nano) Photonic and Cell Technologies for Solar Energy Conversion, 777212 (24 August 2010); doi: 10.1117/12.860537
Show Author Affiliations
Jan Vaes, IMEC (Belgium)
Alex Masolin, IMEC (Belgium)
Amaia Pesquera, IMEC (Belgium)
Frédéric Dross, IMEC (Belgium)

Published in SPIE Proceedings Vol. 7772:
Next Generation (Nano) Photonic and Cell Technologies for Solar Energy Conversion
Loucas Tsakalakos, Editor(s)

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