Thermal stability of back side metallization multilayer for power device application

Metallization multilayers on the back side of a power device were focused in this study. Si wafers coated with high melting point metals were exposed at 300 °C for 300 h to investigate diffusion condition of the metallization layer. We developed and examined the thermal stability of die bonding material (Au paste) including sub–micrometer–sized Au particles. Auger electron spectroscopy was applied to observe the atomic composition of the multilayers in depth direction after the high temperature aging. Surface morphology was observed using optical microscope and scanning electron microscope. While atomic composition on Ti/Au changed drastically after the high temperature aging, other multilayers maintained their metallization composition. However, the surface morphology was slightly changed on Ti/Ru/Au, W/Au, and Ta/Au. Bond strength on the Ti/Pt/Au kept over 40 MPa with unified bonding layer after exposing at 300 °C for 1000 h.

► We examined metallization multilayer with high temperature durability.
► A paste for die bonding was newly developed.
► These technologies were required for a power device application.
► Ti/Pt/Au had acceptable performance after the high temperature aging test.