A new high temperature resistant bond technology using Ni(P)/Ta/TaN/Ta high temperature solder diffusion barrier

Abstract

The commonly used electroless plated Ni(P) diffusion barrier is prone to react rapidly with Au-Ge eutectic solder to form NiGe, Ni5Ge3 and Ni3P intermetalics (IMC) at the solder/Ni(P) interface afier aging at 330°C. The rapid growth of the Ni-Ge intermetalics and the subsequent oxidation of the Cu circuit path under the Ni(P) layer seriously degrade the joint of the Au-Ge solder/Ni(P) interface. To improve joint reliability, a 200 nm-thick Ni(P)/Ta/TaN/Ta diffusion barrier (DB) was prepared on the Ni(P) layer using a sputter process. SiC Schottky Barrier Diode (SBD) power devices were die bonded on the substrate with the Ni(P)/Ta/TaN/Ta DB in a vacuum reffow system. The bonded samples were aged at 330°C in air. Afier 1,000 hrs, little change in the bond strength of the SiC-SBD was observed. Little reaction between the Ni(P)/Ta/TaN/Ta DB and the Au-Ge solder was observed by transmission electron microscopy (TEM). The Ni(P)/Ta/TaN/Ta DB adheres well to the Ni(P) layer afier a thermal cycling test of 1,079 cycles in the temperature range of -40̃300°C.