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1991
Conference Paper
Titel
Impact of metallization techniques on 20 % efficient silicon solar cells
Abstract
The damage to the Si-SiOsub2 interface by electron- beam in comparison to thermal (i.e. resistive heating) evaporation of Al and Ti is investigated for oxide thicknesses ranging from 14 to 105 nm. C-V and PCD measurements on MOS test structures fabricated on 1 to 100 Omegacm p-type FZ-silicon reveal: (i) severe damage to the interface is caused by e-beam, but not by thermal evaporation, (ii) in terms of midgap interface state densities and PCD time constants the electron-beam damage is removed by a postmetallization anneal in forming gas for all oxide thicknesses, (iii) a photoresist or Al layer of up to 1.6Mym yields no effective shielding. Solar cells with thick passivating oxides (105 nm) gave comparably high efficiencies above 20 % for both metallization techniques. The earlier reported poor passivation quality of thin oxides on solar cell emitters metallized by electron-beam evaporation is possibly due to an increase of the interface state density towards the band egdes.
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