Research on wafer scale bonding method based on gold-tin eutectic solders [MEMS packaging]

This paper presents the preliminary results for an on-going program in wafer-level MEMS packaging. In this particular paper, two classes of samples by reactive ion sputtering technique were presented. The first one was first sputtered with nickel/chromium (Ni/Cr) alloy and then sputtered with gold (Au) metal as bonding material; the second one was sputtered with Cr, tin (Sn) and Au respectively as bonding material. The bonding of the former sample based on Ni/Cr and Au material heating failed in most areas of the wafers. The eutectic bonding experiment of the later sample, based on Cr, Sn and Au material heating by a global heating method was completed in an annealing oven at a temperature of about 350/spl deg/C, and the heating time was three minutes. The testing results showed the eutectic bonding of Au-Sn by global heating was successful in most areas.