Formation of Ag/Al Screen-Printing Contacts on B Emitters

In this study, the contact formation process of Al con- taining Ag screen-printing pastes to BBr3 -based B emitters on Si is investigated. Therefore, a detailed scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy study of top-view and cross-sectional samples was conducted. The possible influence of a SiNx:H antireflection coating was considered by comparing contacts with and without a SiNx:H layer. To analyze the role of the glass frit in the paste, the contact formation of pastes without glass was examined. The results indicate that the Ag/Al contact spots grow below the Si surface/SiNx:H layer. The glass frit is only indispensable for etching the antireflection layer—it is not needed for melting the metal in the screen-printing paste. The realized experiments lead to a phenomenological model for the contact for- mation process of Al containing screen-printing pastes to boron emitters.