| 摘要 |
PURPOSE:To establish a stable process having excellent affinity and wettability with soft solder in a chip fixing process in the next process by constituting electrode structure on the rear by Ni-Sn-Ag-Au or Ni-Sn-Ag and by interposing Sn between Ni and Ag. CONSTITUTION:Three layers of Ni, Sn and Ag are attached onto the rear of an silicon wafer 1 by the same vacuum system through an evaporation method. Ni 3 in thickness of 2000-10000Angstrom , Sn in 400-600Angstrom and Ag 6 in 8000-12000Angstrom are affixed at that time. The wafer on which Ni-Sn-Ag are vapor-deposited is taken out of an evaporating device once, and sintered and treated at a high temperature of 450-500 deg.C in inert gas atmosphere such as Ni and Ar gases, and a nickel silicide layer 2 is formed, thus acquiring good ohmic contact on the reverse side. Sn is melted during the heat treatment of the sintering, and the alloy layers of Sn-Ag 5 and Ni-Sn-Ag 4 are shaped, thus obtaining an ohmic metallic layer having the superior degree of adhesion. Au 7 is deposited by evaporation in thickness of 2000-4000Angstrom in order to improve wettability with soft solder. |
